Investments in Debt and Equity Securities (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Schedule of Investments in Debt and Equity Securities
Cost basis	$ 1,645	$ 1,613
Unrealized pretax net gains (losses)	49	70
Fair Value	1,694	1,683
U.S. treasury bonds
Schedule of Investments in Debt and Equity Securities
Cost basis	10	10
Unrealized pretax net gains (losses)	0	0
Fair Value	10	10
Other U.S. and non-U.S. government bonds
Schedule of Investments in Debt and Equity Securities
Cost basis	58	58
Unrealized pretax net gains (losses)	1	1
Fair Value	59	59
Corporate bonds
Schedule of Investments in Debt and Equity Securities
Cost basis	998	962
Unrealized pretax net gains (losses)	34	50
Fair Value	1,032	1,012
Asset-backed securities
Schedule of Investments in Debt and Equity Securities
Cost basis	150	156
Unrealized pretax net gains (losses)	2	3
Fair Value	152	159
U.S. governmental agency mortgage-backed securities
Schedule of Investments in Debt and Equity Securities
Cost basis	349	362
Unrealized pretax net gains (losses)	10	12
Fair Value	359	374
Residential
Schedule of Investments in Debt and Equity Securities
Cost basis	5	5
Unrealized pretax net gains (losses)	0	0
Fair Value	5	5
Commercial
Schedule of Investments in Debt and Equity Securities
Cost basis	75	60
Unrealized pretax net gains (losses)	2	4
Fair Value	$ 77	$ 64