CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 320	$ 223
Other comprehensive income (loss):
Net unrealized derivative instrument (losses) gains arising during the periods, net of income taxes of ($2) and $21, respectively	(3)	33
Reclassification adjustment for net derivative gains included in net income, net of income taxes of ($4) and ($6), respectively	(6)	(8)
Net unrealized securities available for sale gains arising during the periods, net of income taxes of $3 and $92, respectively	5	154
Other-than-temporary impairment not recognized in earnings on securities, net of income taxes of ($7) and ($15), respectively	(12)	(25)
Reclassification of net securities gains to net income, net of income taxes of ($1) and ($3), respectively	(2)	(5)
Employee benefit plans:
Amortization of actuarial loss, net of income taxes of $2 and $2, respectively	3	2
Total other comprehensive (loss) income, net of income taxes	(15)	151
Total comprehensive income	$ 305	$ 374