Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues
Net earned premiums	$ 125	$ 142	$ 136	$ 145	$ 178	$ 186	$ 162	$ 164	$ 548	$ 690	$ 864
Net investment income	100	98	99	101	96	99	101	122	398	418	408
Net realized investment gains (losses)	(18)	(7)	(2)	(5)	(14)	7	15	32	(32)	40	(29)
Net change in fair value of credit derivatives	9	21	48	34	5	58	(6)	54	112	111	98
Fair value gains (losses) on FG VIEs	3	5	2	4	5	3	12	10	14	30
Bargain purchase gain and settlement of pre-existing relationships					0	0	0	58	0	58	259
Commutation gains	0	1	(18)	1	0	255	0	73	(16)	328	8
Other income (loss)	(5)	14	(44)	13	11	15	24	14	(22)	64	31
Expenses
Loss and LAE	21	17	44	(18)	34	223	72	59	64	388	295
Amortization of DAC	4	3	4	5	6	5	4	4	16	19	18
Interest expense	23	23	24	24	24	24	25	24	94	97	102
Other operating expenses	65	56	62	65	61	58	57	68	248	244	245
Income (loss) before income taxes	101	175	87	217	156	313	150	372	580	991	1,017
Provision (benefit) for income taxes	13	14	12	20	104	105	(3)	55	59	261	136
Net income (loss)	$ 88	$ 161	$ 75	$ 197	$ 52	$ 208	$ 153	$ 317	$ 521	$ 730	$ 881
Earnings per share:
Basic (in dollars per share)	$ 0.84	$ 1.48	$ 0.67	$ 1.71	$ 0.44	$ 1.75	$ 1.26	$ 2.53	$ 4.73	$ 6.05	$ 6.61
Diluted (in dollars per share)	$ 0.83	$ 1.47	$ 0.67	$ 1.68	$ 0.44	$ 1.72	$ 1.24	$ 2.49	$ 4.68	$ 5.96	$ 6.56