Consolidated Entities and Equity Method Investments - Redeemable Noncontrolling Interest (Details) - USD ($) $ in Millions |
12 Months Ended | |
|---|---|---|
Dec. 31, 2017 |
Dec. 31, 2016 |
|
| Noncontrolling Interest [Roll Forward] | ||
| Redemption of redeemable noncontrolling interests | $ (129) | |
| Southern Power | ||
| Noncontrolling Interest [Roll Forward] | ||
| Beginning balance | $ 164 | 43 |
| Net income attributable to redeemable noncontrolling interests | 2 | 4 |
| Distributions to redeemable noncontrolling interests | (2) | (1) |
| Capital contributions from redeemable noncontrolling interests | 2 | 118 |
| Redemption of redeemable noncontrolling interests | (59) | (129) |
| Reclassification to non-redeemable noncontrolling interests | (114) | |
| Change in fair value of redeemable noncontrolling interests | 7 | |
| Ending balance | $ 0 | $ 164 |