Selected Quarterly Financial Data (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Net interest income	$ 621	$ 617	$ 626	$ 606	$ 569	$ 543	$ 673	$ 519	$ 2,470	[1]	$ 2,304	[1]	$ 2,041	[1]
Provision for credit losses	267	47	(6)	53	64	23	85	16	361		188		193
Net interest income after provision for credit losses	354	570	632	553	505	520	588	503	2,109		2,116		1,848
Other revenues	274	531	403	464	459	386	261	500	1,672		1,606		1,857
Operating expenses	808	786	850	777	864	934	876	750	3,221	[2]	3,424	[2]	3,887	[2]
Income (loss) before income tax	(180)	315	185	240	100	(28)	(27)	253	560		298		(182)
Income tax expense (benefit)	(55)	111	98	76	30	(29)	(206)	149	230		(56)		156
Net income (loss)	$ (125)	$ 204	$ 87	$ 164	$ 70	$ 1	$ 179	$ 104	$ 330		$ 354		$ (338)

[1] Net interest income of each segment represents the difference between actual interest earned on assets and interest paid on liabilities of the segment adjusted for a funding charge or credit. Segments are charged a cost to fund assets (e.g. customer loans) and receive a funding credit for funds provided (e.g. customer deposits) based on equivalent market rates. The objective of these charges/credits is to transfer interest rate risk from the segments to one centralized unit in Balance Sheet Management and more appropriately reflect the profitability of segments.

[2] Expenses for the segments include fully apportioned corporate overhead expenses.