Income Taxes - Continuing Operations (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Provision (benefit) for income taxes	$ (11)	$ 26	$ (5)	$ 79	$ (55)	$ 111	$ 98	$ 76	$ 89	$ 230	$ (56)
Income taxes related to adjustments included in common equity:
Unrealized gains (losses) on investment securities, net									(135)	(242)	114
Unrealized gains (losses) on derivatives classified as cash flow hedges									9	2	(46)
Employer accounting for post-retirement plans									2	0	(4)
Other-than-temporary impairment on debt securities									0	0	43
Total income taxes									$ (35)	$ (10)	$ 51