CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 223	$ 209
Other comprehensive income:
Net unrealized derivative instrument gains arising during the periods, net of income taxes of $21 and $39, respectively	33	65
Reclassification adjustment for net derivative gains included in net income, net of income taxes of ($6) and ($1), respectively	(8)	(2)
Net unrealized securities available for sale gains arising during the periods, net of income taxes of $92 and $54, respectively	154	90
Other-than-temporary impairment not recognized in earnings on securities, net of income taxes of ($15) and ($11), respectively	(25)	(19)
Reclassification of net securities gains to net income, net of income taxes of ($3) and ($3), respectively	(5)	(4)
Defined benefit pension plans:
Amortization of actuarial loss, net of income taxes $2 and $1, respectively	2	2
Total other comprehensive income, net of income taxes	151	132
Total comprehensive income	$ 374	$ 341