CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ 1,045	$ 840	$ 865
Other comprehensive (loss) income:
Net unrealized derivative instrument (losses) gains arising during the periods, net of income taxes of ($38), $57, and $122, respectively	(62)	93	212
Reclassification adjustment for net derivative (gains) losses included in net income, net of income taxes of ($22), ($9), and $10, respectively	(36)	(14)	17
Net unrealized securities available for sale (losses) gains arising during the periods, net of income taxes of ($82), ($38), and $116, respectively	(139)	(66)	198
Other-than-temporary impairment not recognized in earnings on securities, net of income taxes of ($10), ($14), and ($13), respectively	(17)	(22)	(22)
Reclassification of net securities gains to net income, net of income taxes of ($2), ($8), and ($7), respectively	(2)	(14)	(11)
Employee benefit plans:
Actuarial loss, net of income taxes of ($20), ($3), and ($92), respectively	(34)	(3)	(148)
Net prior service credit, net of income taxes of $0, $0 and $3, respectively	0	0	4
Amortization of actuarial loss, net of income taxes of $6, $3, and $3, respectively	10	12	7
Amortization of net prior service credit, net of income taxes $0, $0 and $0, respectively	(1)	(1)	(1)
Divestitures effective September 1, 2014, net of income taxes of $0, $0 and $12, respectively	0	0	20
Total other comprehensive (loss) income, net of income taxes	(281)	(15)	276
Total comprehensive income	$ 764	$ 825	$ 1,141