PARENT COMPANY ONLY FINANCIALS - Condensed Statements of Operations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating Income
Total interest income	$ 4,266	$ 3,854	$ 3,664
Operating expense
Salaries and employee benefits	1,709	1,636	1,678
Interest expense	508	452	363
All other expenses	526	530	573
Applicable income taxes	489	423	403
NET INCOME	1,045	840	865
Other comprehensive (loss) income, net of income taxes
Net unrealized derivative instrument (losses) gains arising during the period	(62)	93	212
Net unrealized securities (losses) gains arising during the period	(139)	(66)	198
Net other comprehensive (loss) income	(281)	(15)	276
Total other comprehensive (loss) income, net of income taxes	(281)	(15)	276
Total comprehensive income	764	825	1,141
Payments of ordinary common stock dividends	241	214	806
Dividends to preferred stockholders	14	7
Parent company
Operating Income
Dividends	555	345	595
Interest income	53	54	29
Management and service fees	26	20	21
Securities gains	3	3	0
All other operating income	7	4	5
Total interest income	644	426	650
Operating expense
Salaries and employee benefits	37	15	63
Interest expense	99	108	80
All other expenses	15	38	123
Total operating expense	151	161	266
Income before taxes and undistributed income	493	265	384
Applicable income taxes	(26)	(29)	(77)
Income before undistributed income of subsidiaries and associated companies	519	294	461
Equity in undistributed income (losses) of subsidiaries and associated companies	526	546	404
NET INCOME	1,045	840	865
Other comprehensive (loss) income, net of income taxes
Net pension plan activity arising during the period	(2)	1	8
Net unrealized derivative instrument (losses) gains arising during the period	(8)	2	0
Net unrealized securities (losses) gains arising during the period	0	(2)	1
Net other comprehensive (loss) income	(10)	1	9
Other comprehensive income (loss) activity of Bank subsidiaries, net of income taxes	(271)	(16)	267
Total other comprehensive (loss) income, net of income taxes	(281)	(15)	276
Total comprehensive income	764	825	1,141
Bank subsidiaries | Parent company
Operating expense
Equity in undistributed income (losses) of subsidiaries and associated companies	522	543	402
Nonbank subsidiaries | Parent company
Operating expense
Equity in undistributed income (losses) of subsidiaries and associated companies	$ 4	$ 3	$ 2