Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues
Net earned premiums	$ 178	$ 186	$ 162	$ 164	$ 236	$ 231	$ 214	$ 183	$ 690	$ 864	$ 766
Net investment income	96	99	101	122	117	94	98	99	418	408	423
Net realized investment gains (losses)	(14)	7	15	32	(24)	(2)	10	(13)	40	(29)	(26)
Net change in fair value of credit derivatives	5	58	(6)	54	74	21	63	(60)	111	98	728
Fair value gains (losses) on CCS	2	(4)	2	(2)	50	(23)	(11)	(16)	(2)	0	27
Fair value gains (losses) on FG VIEs	5	3	12	10	27	(11)	4	18	30	38
Bargain purchase gain and settlement of pre-existing relationships	0	0	0	58	0	259	0	0	58	259	214
Other income (loss)	9	274	22	89	(10)	(3)	18	34	394	39	37
Expenses
Loss and LAE	34	223	72	59	112	(9)	102	90	388	295	424
Amortization of DAC	6	5	4	4	5	4	5	4	19	18	20
Interest expense	24	24	25	24	25	26	25	26	97	102	101
Other operating expenses	61	58	57	68	57	65	63	60	244	245	231
Income (loss) before income taxes	156	313	150	372	271	480	201	65	991	1,017	1,431
Provision (benefit) for income taxes	104	105	(3)	55	74	1	55	6	261	136	375
Net income (loss)	$ 52	$ 208	$ 153	$ 317	$ 197	$ 479	$ 146	$ 59	$ 730	$ 881	$ 1,056
Earnings per share:
Basic (in dollars per share)	$ 0.44	$ 1.75	$ 1.26	$ 2.53	$ 1.51	$ 3.63	$ 1.09	$ 0.43	$ 6.05	$ 6.61	$ 7.12
Diluted (in dollars per share)	0.44	1.72	1.24	2.49	1.49	3.60	1.09	0.43	5.96	6.56	7.08
Dividends (in dollars per share)	$ 0.1425	$ 0.1425	$ 0.1425	$ 0.1425	$ 0.13	$ 0.13	$ 0.13	$ 0.13	$ 0.57	$ 0.52	$ 0.48