CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net unrealized derivative instrument (losses) gains arising during the periods, tax	$ (9)	$ (38)	$ 57
Reclassification adjustment for net derivative gains included in net income, tax	(9)	(22)	(9)
Net unrealized securities losses arising during the periods, tax	(4)	(82)	(38)
Other-than-temporary impairment not recognized in earnings on securities, tax	0	(10)	(14)
Reclassification of net securities gains to net income, tax	(2)	(2)	(8)
Actuarial loss, tax	12	(20)	(3)
Amortization of actuarial loss, tax	5	6	3
Amortization of net prior service credit, tax	$ 0	$ 0	$ 0