Fair Value Measurements (Details) - Changes in Level 3 - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Changes in Level 3 fair value category [Roll Forward]
Level 3 fair value category, beginning balance	$ 121	$ 222
Level 3 fair value category, total realized and unrealized investment gains (losses) reported in net realized investment gains	(1)	3
Level 3 fair value category, total unrealized investment gains (losses) reported in increases in other comprehensive income (loss)	2	4
Level 3 fair value category purchases	95	44
Level 3 fair value category sales	(1)	(26)
Level 3 fair value category settlements/maturities	(15)	(19)
Gross transfers into Level 3	3	0
Gross transfers out of Level 3	(3)	(107)
Level 3 fair value category, ending balance	201	121
Amount of total realized investment gains (losses) for the period included in the consolidated statement of income attributable to changes in the fair value of assets still held at the reporting date	0	0
Fixed maturities [Member]
Changes in Level 3 fair value category [Roll Forward]
Level 3 fair value category, beginning balance	101	186
Level 3 fair value category, total realized and unrealized investment gains (losses) reported in net realized investment gains	(1)	0
Level 3 fair value category, total unrealized investment gains (losses) reported in increases in other comprehensive income (loss)	2	4
Level 3 fair value category purchases	79	38
Level 3 fair value category sales	0	(1)
Level 3 fair value category settlements/maturities	(15)	(19)
Gross transfers into Level 3	3	0
Gross transfers out of Level 3	(3)	(107)
Level 3 fair value category, ending balance	166	101
Amount of total realized investment gains (losses) for the period included in the consolidated statement of income attributable to changes in the fair value of assets still held at the reporting date	0	0
Other investments [Member]
Changes in Level 3 fair value category [Roll Forward]
Level 3 fair value category, beginning balance	20	36
Level 3 fair value category, total realized and unrealized investment gains (losses) reported in net realized investment gains	0	3
Level 3 fair value category, total unrealized investment gains (losses) reported in increases in other comprehensive income (loss)	0	0
Level 3 fair value category purchases	16	6
Level 3 fair value category sales	(1)	(25)
Level 3 fair value category settlements/maturities	0	0
Gross transfers into Level 3	0	0
Gross transfers out of Level 3	0	0
Level 3 fair value category, ending balance	35	20
Amount of total realized investment gains (losses) for the period included in the consolidated statement of income attributable to changes in the fair value of assets still held at the reporting date	$ 0	$ 0