CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Reclassification of unrealized losses on cash flow hedges from accumulated other comprehensive income (loss) to net income, tax expense (benefit)	$ (4)	$ 8	$ 8
Net unrealized gains (losses) on securities still held, tax expense (benefit)	4	8	(5)
Reclassification from accumulated other comprehensive income (loss) to net income, tax expense (benefit)	1	(1)	(1)
Net gain (loss) and prior service benefit (cost), tax expense (benefit)	11	(14)	(5)
Reclassification from accumulated other comprehensive income (loss) to net income, tax expense (benefit)	(1)	(1)	(1)
Net unrealized gains (losses) on foreign currency translation, tax expense (benefit)	0	0	0
Other comprehensive income (loss) related to equity method investee, tax expense (benefit)	1	0	1
AOCI Impacts of NEP Deconsolidation, tax	0	0	15
Impact on Disposal, Tax	$ (19)	$ 0	$ 0