CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Statement of Comprehensive Income [Abstract]
Changes in unrealized gains (losses) - taxes (benefits)	$ (20)	$ 16	$ (7)	$ 65
Reclassification adjustment for net losses (gains) realized in net income - benefits (taxes)	(3)	(5)	(16)	(11)
Changes in market value of derivatives - taxes (benefits)	1	3	2	3
Reclassification adjustment for net losses (gains) realized in net income - benefits (taxes)	$ 2	$ 0	$ 4	$ 0