Variable Interest Entities - Effect of Consolidating FG VIE's on Financial Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Variable Interest Entity [Line Items]
Net earned premiums	$ 142	$ 186	$ 423	$ 512
Net investment income	98	99	298	322
Fair value gains (losses) on FG VIEs	5	3	11	25
Loss and LAE	17	223	43	354
Income (loss) before income taxes	175	313	479	835
Less: tax provision (benefit)	14	105	46	157
Net income (loss)	161	208	433	678
Effect on OCI	(3)	0	(1)	0
Net cash flows provided by (used in) operating activities			352	354
Effect on shareholders' equity (decrease) increase	6,583		6,583		$ 6,839
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Net earned premiums	(3)	(3)	(9)	(11)
Net investment income	(1)	(2)	(3)	(4)
Fair value gains (losses) on FG VIEs	5	3	11	25
Loss and LAE	(3)	1	0	5
Income (loss) before income taxes	(2)	(1)	(1)	15
Less: tax provision (benefit)	0	0	0	5
Net income (loss)	(2)	(1)	(1)	10
Effect on OCI	(2)	0	0	0
Net cash flows provided by (used in) operating activities	1	$ 6	7	$ 16
Effect on shareholders' equity (decrease) increase	$ 1		$ 1		$ 2