CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 348	$ 297	$ 986	$ 763
Other comprehensive income:
Net unrealized derivative instrument (losses) gains arising during the periods, net of income taxes of ($1), $0, $13 and $29, respectively	(1)	(1)	22	45
Reclassification adjustment for net derivative gains included in net income, net of income taxes of ($2), ($4), ($8) and ($14), respectively	(2)	(6)	(13)	(23)
Net unrealized securities gains (losses) arising during the periods, net of income taxes of $8, ($17), $44 and $114, respectively	13	(28)	74	190
Other-than-temporary impairment not recognized in earnings on securities, net of income taxes of $0, $2, ($1) and ($11), respectively	0	3	(2)	(18)
Reclassification of net securities (gains) losses to net income, net of income taxes of $0, $1, ($1) and ($1), respectively	(1)	2	(2)	(1)
Employee Benefit Plans: Amortization of actuarial loss, net of income taxes of $2, $2, $6 and $5, respectively	3	2	8	7
Total other comprehensive income (loss), net of income taxes	12	(28)	87	200
Total comprehensive income	$ 360	$ 269	$ 1,073	$ 963