PARENT COMPANY ONLY FINANCIALS - Condensed Cash Flow Statements (Details) - USD ($)			12 Months Ended
	Jul. 28, 2016	Apr. 07, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
OPERATING ACTIVITIES
Net income			$ 1,045,000,000	$ 840,000,000	$ 865,000,000
Deferred income taxes			153,000,000	249,000,000	141,000,000
Gain on sales of assets			0	0	9,000,000
(Decrease) increase in other liabilities			(59,000,000)	(161,000,000)	239,000,000
(Increase) decrease in other assets			(274,000,000)	(467,000,000)	(295,000,000)
Net cash provided by operating activities			1,490,000,000	1,229,000,000	1,390,000,000
INVESTING ACTIVITIES
Net cash used in investing activities			(11,326,000,000)	(5,905,000,000)	(10,274,000,000)
FINANCING ACTIVITIES
Proceeds from issuance of long-term borrowed funds			15,144,000,000	6,750,000,000	3,249,000,000
Repayments of long-term borrowed funds	$ (500,000,000)		(8,429,000,000)	(766,000,000)	(6,000,000)
Treasury stock purchased		$ (250,000,000)	(430,000,000)	(500,000,000)	(334,000,000)
Net proceeds from issuance of preferred stock			0	247,000,000	0
Dividends declared and paid to common stockholders			(241,000,000)	(214,000,000)	(806,000,000)
Dividends declared and paid to preferred stockholders			(14,000,000)	(7,000,000)	0
Net cash provided by financing activities			10,455,000,000	4,485,000,000	9,403,000,000
Increase (decrease) in cash and cash equivalents			619,000,000	(191,000,000)	519,000,000
Cash and cash equivalents at beginning of period			3,085,000,000	3,276,000,000	2,757,000,000
Cash and cash equivalents at end of period			3,704,000,000	3,085,000,000	3,276,000,000
Parent company
OPERATING ACTIVITIES
Net income			1,045,000,000	840,000,000	865,000,000
Deferred income taxes			5,000,000	49,000,000	27,000,000
Gain on sales of assets			(3,000,000)	(3,000,000)	0
Equity in undistributed (earnings) losses of subsidiaries			(526,000,000)	(546,000,000)	(404,000,000)
(Decrease) increase in other liabilities			(19,000,000)	(48,000,000)	18,000,000
(Increase) decrease in other assets			35,000,000	(16,000,000)	(74,000,000)
Other operating, net			(4,000,000)	3,000,000	17,000,000
Total adjustments			(512,000,000)	(561,000,000)	(416,000,000)
Net cash provided by operating activities			533,000,000	279,000,000	449,000,000
INVESTING ACTIVITIES
Proceeds from sales and maturities of securities available for sale			0	8,000,000	0
Payments for investments in and advances to subsidiaries			(40,000,000)	(215,000,000)	(1,470,000,000)
Sale or repayment of investments in and advances to subsidiaries			588,000,000	376,000,000	945,000,000
Other investing, net			(2,000,000)	0	(11,000,000)
Net cash used in investing activities			546,000,000	169,000,000	(536,000,000)
FINANCING ACTIVITIES
Proceeds from issuance of long-term borrowed funds			349,000,000	1,000,000,000	1,000,000,000
Repayments of long-term borrowed funds			(625,000,000)	(750,000,000)	0
Proceeds from issuance of common stock			22,000,000	27,000,000	13,000,000
Treasury stock purchased			(430,000,000)	(500,000,000)	(334,000,000)
Net proceeds from issuance of preferred stock			0	247,000,000	0
Dividends declared and paid to common stockholders			(241,000,000)	(214,000,000)	(806,000,000)
Dividends declared and paid to preferred stockholders			(14,000,000)	(7,000,000)	0
Net cash provided by financing activities			(939,000,000)	(197,000,000)	(127,000,000)
Increase (decrease) in cash and cash equivalents			140,000,000	251,000,000	(214,000,000)
Cash and cash equivalents at beginning of period			531,000,000	280,000,000	494,000,000
Cash and cash equivalents at end of period			$ 671,000,000	$ 531,000,000	$ 280,000,000