| Fair Value, Net Asset (Liability) | $9.7B | $10.1B | $10.9B | $11.3B | $11.7B | $12B | $12B | $12.9B |
| Debt Securities, Available-for-sale, and Equity Securities, FV-NI | $9.7B | $10.6B | $11.3B | $11.5B | $12.1B | $11.9B | $11.8B | $12.6B |
| Deferred Income Taxes and Other Tax Liabilities, Noncurrent | $10.4B | $10.6B | $10.7B | $10.8B | $10.9B | $11.4B | $11.6B | $12B |
| Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Gain | $4.2B | $5B | $5.6B | $5.7B | $6.1B | $5.8B | $5.5B | $6.3B |
| Debt issuances | $8.5B | $9.8B | $3.5B | $6.4B | $7.7B | $7.7B | $3.2B | $3.9B |
| Available for sale investments | $2.8B | $3B | $3.1B | $3.2B | $3.4B | $3.3B | $3.5B | $3.6B |
| Common stock, shares authorized (in shares) | 2B | 2B | 2B | 2B | 2B | 2B | 2B | 2B |
| Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year 10 | $1.5B | $1.6B | $1.6B | $1.6B | $1.8B | $1.7B | $1.9B | $1.9B |
| Noncontrolling interests in subsidiaries | $2.8B | $1.1B | $1.1B | $1.1B | $1.1B | $1.1B | $1.1B | $1.1B |
| Other Operating Lease, Liability, Noncurrent | $897M | $917M | $915M | $925M | $956M | $957M | $1B | $1B |
| Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year One Through Five | $671M | $696M | $715M | $785M | $862M | $791M | $921M | $896M |
| Accumulated Deferred Investment Tax Credit | $856M | $864M | $862M | $860M | $866M | $894M | $888M | $882M |
| Common Stock, Shares, Outstanding | 771M | 771M | 772M | 772M | 772M | 776M | 777M | 778M |
| Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year 5 Through 10 | $545M | $598M | $614M | $664M | $712M | $721M | $610M | $695M |
| Derivative, gross, assets | $525M | $189M | $255M | $247M | $162M | $434M | $472M | $539M |
| Derivatives | $304M | $91M | $129M | $163M | $99M | $130M | $114M | $336M |
| Equity method investments (Note 11) | $505M | $492M | $502M | $483M | $477M | $353M | $357M | $332M |
| Gross Assets/Liabilities | $520M | $729M | $612M | $473M | $561M | $319M | $272M | $256M |
| Derivatives, gross, liabilities | $520M | $729M | $612M | $473M | $561M | $319M | $272M | $256M |
| Derivative Liability | $520M | $729M | $612M | $473M | $561M | $319M | $272M | $256M |
| Accounts Receivable, Allowance for Credit Loss | $203M | $205M | $204M | $207M | $218M | $209M | $204M | $199M |
| Allowance for doubtful accounts - receivables | $49M | $55M | $102M | $119M | $127M | $124M | $204M | $199M |
| Debt Securities, Available-for-sale, and Equity Securities, FV-NI, Unrealized Loss | $351M | $171M | $191M | $187M | $111M | $219M | $209M | $150M |
| Derivative Liability, Noncurrent | $159M | $217M | $162M | $180M | $300M | $133M | $132M | $121M |
| Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, Year One | $137M | $116M | $126M | $115M | $92M | $89M | $83M | $87M |
| Accrual for Environmental Loss Contingencies | $90M | $88M | $86M | $82M | $80M | $73M | $68M | $73M |
| Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs | $30M | $15M | $6M | $35M | $17M | $9M | $3M | $14M |
| Aggregate Fair Value of Additional Collateral Required | $291M | $198M | $197M | $225M | $150M | $95M | $31M | $9M |
| Additional Collateral Required - One Notch Downgrade | $291M | $198M | $197M | $225M | $150M | $95M | $31M | $9M |
| Derivative, Net Liability Position, Aggregate Fair Value | $312M | $342M | $314M | $242M | $198M | $101M | $31M | $9M |
| Common stock, par value (in dollars per share) | $0.00 | $0.00 | $0.00 | $0.00 | $0.00 | $0.00 | $0.00 | $0.00 |
| Accidental outage insurance coverage policy limit | — | — | — | — | — | $490M | — | — |
| Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Excluding Held For Sale | — | $345M | — | — | — | $418M | — | — |
| Collateral already posted, aggregate fair value | $21M | $144M | $117M | $17M | $48M | $6M | — | — |
| Cumulative Payables Sold | — | $50M | — | — | — | $13M | — | — |
| Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net | — | $1B | — | — | — | $1B | — | — |
| Debt Instrument, Unamortized Discount (Premium), Net | — | -$916M | — | — | — | -$845M | — | — |
| Weighted Average Interest Rate (as a percent) | — | 4.3% | — | — | — | 4.4% | — | — |
| Decommissioning costs | — | $8.8B | — | — | — | $9B | — | — |
| Deferred Tax Liabilities, Gross | — | $15.7B | — | — | — | $15.8B | — | — |
| Progress Energy merger purchase accounting adjustments | — | $260M | — | — | — | $227M | — | — |
| Lease obligations | — | $418M | — | — | — | $430M | — | — |
| Deferred Tax Assets, Net of Valuation Allowance | — | $5.1B | — | — | — | $4.4B | — | — |
| Alternative minimum tax | — | $69M | — | — | — | $133M | — | — |
| Pension, post-retirement and other employee benefits | — | $65M | — | — | — | $89M | — | — |
| Other | — | $327M | — | — | — | $284M | — | — |
| Deferred Tax Assets, Valuation Allowance | — | $544M | — | — | — | $517M | — | — |
| Deferred Tax Liabilities, Net | — | $10.6B | — | — | — | $11.4B | — | — |
| Deferred Tax Liabilities, Property, Plant and Equipment | — | $12B | — | — | — | $11.9B | — | — |
| Deferred Tax Liabilities, Regulatory Assets | — | $1.9B | — | — | — | $1.8B | — | — |
| Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Next Fiscal Year | — | 6.5% | — | — | — | 7.0% | — | — |
| Defined Benefit Plan, Ultimate Health Care Cost Trend Rate | — | 4.8% | — | — | — | 4.8% | — | — |
| Coal | — | $842M | — | — | — | $801M | — | — |
| Excess nuclear liability program coverage | — | $16.2B | — | — | — | $15.8B | — | — |
| Finance Lease, Right-of-Use Asset, Accumulated Amortization | — | $3M | — | — | — | — | — | — |
| Property, plant and equipment | — | $697M | — | — | — | $670M | — | — |
| Gross Carrying Amount | — | $296M | — | — | — | $296M | — | — |
| First mortgage bonds | — | $37.4B | — | — | — | $39.8B | — | — |
| Settlement of equity forwards, net cash proceeds | — | — | — | — | — | $297M | — | — |
| Goodwill accumulated impairment losses | $0 | $0 | $0 | $0 | $0 | $0 | $0 | $0 |
| Insurance coverage percentage additional weeks (as a percent) | — | 80.0% | — | — | — | 80.0% | — | — |
| Insurance coverage percentage initial weeks (as a percent) | — | 100.0% | — | — | — | 100.0% | — | — |
| Industry aggregate limit | — | $3.2B | — | — | — | $3.2B | — | — |
| Pro rata assessment for each reactor owned for each incident exceeding public liability insurance | — | $166M | — | — | — | $166M | — | — |
| Annual payment limit to pro rata assessments | — | $24.7M | — | — | — | $24.7M | — | — |
| Insured public liability limit per nuclear incident | — | $16.2B | — | — | — | $16.2B | — | — |
| Sublimit accidental outage recovery | — | $328M | — | — | — | $291M | — | — |
| Sublimit for non-nuclear terrorist events | — | $1.8B | — | — | — | $1.8B | — | — |
| Sublimit property damage losses | — | $1.5B | — | — | — | $1.5B | — | — |
| Interest Rate Derivatives, at Fair Value, Net | — | -$32M | — | — | — | $82M | — | — |
| Liabilities of discontinued operations (Note 2) | $1.6B | $157M | $126M | $112M | $85M | $89M | $0 | $0 |
| Long-Term Debt and Lease Obligation | — | $72.5B | — | — | — | $76.3B | — | — |
| Long Term Debt Excluding Purchase Accounting Adjustments | — | $74.7B | — | — | — | $80.2B | — | — |
| 2028 | — | $4.2B | — | — | — | $4.9B | — | — |
| 2029 | — | $4.3B | — | — | — | $3.1B | — | — |
| 2029 | — | $4.6B | — | — | — | $5B | — | — |
| 2030 | — | $2.5B | — | — | — | $3.9B | — | — |
| Thereafter | — | $56.4B | — | — | — | $59B | — | — |
| 2027 | — | $2.8B | — | — | — | $4.3B | — | — |
| Tax exempt bonds | — | $1.3B | — | — | — | $1.3B | — | — |
| Maximum magnitude of retroactive premiums | — | $10 | — | — | — | $10 | — | — |
| Notes payable and commercial paper | — | $4.9B | — | — | — | $4.2B | — | — |
| Number of licensed nuclear reactors | — | 95.00 | — | — | — | 95.00 | — | — |
| Equipment | — | $3.4B | — | — | — | $3.9B | — | — |
| Land | — | $2.3B | — | — | — | $2.6B | — | — |
| Other plant in service | — | $6.9B | — | — | — | $6.9B | — | — |
| Regulatory Asset | — | $17.3B | — | — | — | $17B | — | — |
| Regulatory liabilities | — | $15.4B | — | — | — | $16.1B | — | — |
| Restructuring Reserve | — | $102M | — | — | — | $19M | — | — |
| Shares reserved for awards to employees and outside directors (in shares) | — | 15M | — | — | — | 15M | — | — |
| Additional nuclear accident limit | — | $1.3B | — | — | — | $1.3B | — | — |
| Short term obligations classified as long-term debt | — | $937M | — | — | — | $937M | — | — |
| Unrecognized tax benefits | — | $62M | — | — | — | $74M | — | — |
| Amount that if recognized, would affect the effective tax rate or regulatory liability | — | $57M | — | — | — | $68M | — | — |
| Principal amount of demand notes | — | $985M | — | — | — | $1.1B | — | — |