Equity (Deficit) Changes in AOCI (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Increase (Decrease) in Accumulated Other Comprehensive Income [Roll Forward]
Total other comprehensive loss	$ 206	$ 648	$ 326
Accumulated Net Unrealized Investment Gain (Loss), AFS Securities [Member]
Increase (Decrease) in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	716	1,358
Other comprehensive income (loss) before reclassifications	53	(55)
Amounts reclassified from other comprehensive income	(259)	(587)
Total other comprehensive loss	(206)	(642)
Ending balance	510	716	1,358
Accumulated Other Comprehensive Income (Loss), Other [Member]
Increase (Decrease) in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	43	49
Other comprehensive income (loss) before reclassifications	8	2
Amounts reclassified from other comprehensive income	(8)	(8)
Total other comprehensive loss	0	(6)
Ending balance	43	43	49
Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	759	1,407
Other comprehensive income (loss) before reclassifications	61	(53)
Amounts reclassified from other comprehensive income	(267)	(595)
Total other comprehensive loss	(206)	(648)
Ending balance	$ 553	$ 759	$ 1,407