Equity Changes in AOCI (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Increase (Decrease) in Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	$ 4,030
Total other comprehensive income (loss)	(648)	$ (326)	$ 530
Ending balance	6,071	4,030
Accumulated Net Unrealized Investment Gain (Loss), AFS Securities [Member]
Increase (Decrease) in Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	1,358	2,121
Other comprehensive income (loss) before reclassifications	(55)	(280)
Amounts reclassified from other comprehensive income (loss)	(587)	(483)
Total other comprehensive income (loss)	(642)	(763)
Ending balance	716	1,358	2,121
Accumulated Other Comprehensive Income (Loss), Other [Member]
Increase (Decrease) in Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	49	(388)
Other comprehensive income (loss) before reclassifications	2	17
Amounts reclassified from other comprehensive income (loss)	(8)	420
Total other comprehensive income (loss)	(6)	437
Ending balance	43	49	(388)
Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	1,407	1,733
Other comprehensive income (loss) before reclassifications	(53)	(263)
Amounts reclassified from other comprehensive income (loss)	(595)	(63)
Total other comprehensive income (loss)	(648)	(326)
Ending balance	$ 759	$ 1,407	$ 1,733