CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Reclassification of unrealized losses on cash flow hedges from accumulated other comprehensive income (loss) to net income, tax expense	$ 8	$ 13	$ 32
Net unrealized gains (losses) on securities still held, tax expense (benefit)	(5)	94	50
Reclassification from accumulated other comprehensive income (loss) to net income, tax benefit (less than in 2018)	(1)	(25)	(13)
Net gain (loss) and prior service benefit (cost) tax expense (benefit) (less than for the year ended December 31, 2018)	(5)	29	(13)
Reclassification from accumulated other comprehensive income (loss) to net income, tax benefit	(1)	(1)	0
Net unrealized gains (losses) on foreign currency translation, tax expense (benefit)	0	1	(2)
Other comprehensive income (loss) related to equity method investee, tax	1	1	2
AOCI Impacts of NEP Deconsolidation, tax	$ 15	$ 0	$ 0