INCOME TAXES - Effective Income Tax Reconciliation (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Amount
U.S. Federal income tax expense (benefit)	$ 444	$ (1,214)	$ 359
Increase (decrease) resulting from:
Goodwill impairment	0	1,217	0
State and local income taxes (net of federal benefit)	22	1	61
Bank-owned life insurance	(17)	(17)	(18)
Tax-exempt interest	(15)	(13)	(12)
Tax credits	(27)	(11)	(8)
Other	(4)	(5)	(1)
Total	$ 403	$ (42)	$ 381
Rate
Federal income tax rate, Rate	35.00%	35.00%	35.00%
Increase (decrease) resulting from:
Goodwill Impairment, Rate	0.00%	(35.10%)	0.00%
State and local income taxes (net of federal benefit), Rate	1.70%	0.00%	5.90%
Bank-owned life insurance, Rate	(1.30%)	0.50%	(1.80%)
Tax-exempt interest, Rate	(1.20%)	0.40%	(1.10%)
Tax credits, Rate	(2.10%)	0.30%	(0.70%)
Other, Rate	(0.30%)	0.10%	(0.10%)
Total, Rate	31.80%	1.20%	37.20%