Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues
Net earned premiums	$ 123	$ 123	$ 112	$ 118	$ 125	$ 142	$ 136	$ 145	$ 476	$ 548	$ 690
Net investment income	82	88	110	98	98	99	98	100	378	395	417
Asset management fees	22	0	0	0					22	0	0
Net realized investment gains (losses)	10	16	8	(12)	(18)	(7)	(2)	(5)	22	(32)	40
Net change in fair value of credit derivatives	19	5	(8)	(22)	9	21	48	34	(6)	112	111
Fair value gains (losses) on FG VIEs	0	4	33	5	3	5	2	4	42	14
Foreign exchange gains (losses) on remeasurement	48	(21)	(14)	11	(15)	(8)	(36)	22	24	(37)	60
Bargain purchase gain and settlement of pre-existing relationships									0	0	58
Commutation gains	0	0	1	0	0	1	(18)	1	1	(16)	328
Other income (loss)	(8)	(9)	24	(3)	11	22	(8)	(8)	4	17	5
Expenses
Loss and LAE	18	30	(1)	46	21	17	44	(18)	93	64	388
Amortization of deferred acquisition costs	5	3	4	6	4	3	4	5	18	16	19
Employee compensation and benefit expenses	60	38	39	41	40	36	36	40	178	152
Interest expense	22	22	22	23	23	23	24	24	89	94	97
Other operating expenses	54	27	21	23	25	20	26	25	125	96	101
Income (loss) before income taxes and equity in net earnings of investees	137	86	181	56	100	176	86	217	460	579	991
Equity in net earnings of investees	1	0	1	2	1	(1)	1	0	4	1	0
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	138	86	182	58	101	175	87	217	464	580	991
Provision (benefit) for income taxes	2	17	40	4	13	14	12	20	63	59	261
Net income (loss)	136	69	142	54	88	161	75	197	401	521	730
Less: noncontrolling interests	(1)	0	0	0	0	0	0	0	(1)	0	0
Net income (loss)	$ 137	$ 69	$ 142	$ 54	$ 88	$ 161	$ 75	$ 197	$ 402	$ 521	$ 730
Earnings per share:
Basic (in dollars per share)	$ 1.43	$ 0.71	$ 1.40	$ 0.52	$ 0.84	$ 1.48	$ 0.67	$ 1.71	$ 4.04	$ 4.73	$ 6.05
Diluted (in dollars per share)	$ 1.42	$ 0.70	$ 1.39	$ 0.52	$ 0.83	$ 1.47	$ 0.67	$ 1.68	$ 4.00	$ 4.68	$ 5.96
Asset Management Fees [Member]
Revenues
Asset management fees									$ 18