Claim, Claim Adjustment Expense and Future Policy Benefit Reserves, A&EP Reserves (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2010
Additional amounts ceded under LPT [Abstract]
Net A&EP adverse development before consideration of LPT	$ 125	$ 150	$ 178
Provision for uncollectible third-party reinsurance on A&EP	(25)	(25)	(16)
Total additional amounts ceded under LPT	100	125	162
Retroactive reinsurance benefit recognized	(94)	(107)	(114)
Pretax impact of deferred retroactive reinsurance	6	18	48
A&EP Reserves [Member]
A&EP Reserves [Abstract]
Net A&EP claim and allocated claim adjustment expense reserves				$ 1,600
Aggregate limit under A&EP Loss Portfolio Transfer				4,000
Ceded A&EP claim and allocated claim adjustment expense reserves under existing third party reinsurance contracts transferred to NICO under A&EP Loss Portfolio Transfer				1,200
Reinsurance premium paid to NICO under A&EP loss portfolio transfer				2,000
Net reinsurance receivables transferred to NICO under A&EP Loss Portfolio Transfer				215
Total consideration				$ 2,200
Additional amounts ceded under LPT [Abstract]
Releases from provision for uncollectible third-party reinsurance	25	25	$ 16
Cumulative amounts ceded under loss portfolio transfer	3,300	3,200
Unrecognized deferred retroactive reinsurance benefit	398	392
Fair value of collateral trust account	$ 4,200	$ 3,700