Condensed Statement of Comprehensive Income (Loss) (Parent Company Only) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Condensed Statement of Income Captions [Line Items]
Other revenues									$ 39	$ 38	$ 35
Total net revenue	$ 454	$ 73	$ 445	$ 456	$ 461	$ 440	$ 438	$ 475	1,428	1,814	1,723
Total operating expense									1,207	1,145	1,275
Income before other income (expense), income tax benefit, and equity in income (loss) of consolidated subsidiaries									261	633	305
Total other income (expense)									(170)	(181)	(110)
Income before income tax benefit and equity in income (loss) of consolidated subsidiaries									91	452	195
Income tax benefit									(177)	159	109
Equity in undistributed income (loss) of subsidiaries									7	3	4
Net income	$ 89	$ (153)	$ 292	$ 40	$ 41	$ 86	$ 69	$ 97	268	293	86
Other comprehensive income (loss)									150	204	(143)
Comprehensive income (loss)									418	497	(57)
Parent Company [Member]
Condensed Statement of Income Captions [Line Items]
Dividends from subsidiaries									859	311	193
Other revenues									371	333	281
Total net revenue									1,230	644	474
Total operating expense									487	421	359
Income before other income (expense), income tax benefit, and equity in income (loss) of consolidated subsidiaries									743	223	115
Total other income (expense)									(127)	(166)	(108)
Income before income tax benefit and equity in income (loss) of consolidated subsidiaries									616	57	7
Income tax benefit									(287)	(88)	(76)
Equity in undistributed income (loss) of subsidiaries									(635)	148	3
Net income									268	293	86
Other comprehensive income (loss)									150	204	(143)
Comprehensive income (loss)									$ 418	$ 497	$ (57)