Investments in Debt and Equity Securities (Details 3) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Due in one year or less, Cost Basis	$ 136
Due after one year through five years, Cost Basis	730
Due after five through ten years, Cost Basis	287
Due after ten years, Cost Basis	63
Due in one year or less, Fair Value	136
Due after one year through five years, Fair Value	759
Due after five years through ten years, Fair Value	294
Due after ten years, Fair Value	64
Debt Securities, Available-for-sale, Amortized Cost	1,645		$ 1,613
Available-for-sale securities, debt securities	1,694		1,683
Schedule of Investments in Debt and Equity Securities
Unrealized gain (loss) on equity securities	20	$ (54)
Available-for-sale Securities, Proceeds, Gains and Losses
Proceeds from the sale of available-for-sale securities	100	58
Gross gains from the sale of available-for-sale securities	0	0
Gross losses from the sale of available-for-sale securities	0	$ 0
U.S. governmental agency mortgage-backed securities
Investments, Debt and Equity Securities [Abstract]
Debt Securities, Available-for-sale, Amortized Cost	349		362
Available-for-sale securities, debt securities	359		374
Residential
Investments, Debt and Equity Securities [Abstract]
Debt Securities, Available-for-sale, Amortized Cost	5		5
Available-for-sale securities, debt securities	5		5
Commercial
Investments, Debt and Equity Securities [Abstract]
Debt Securities, Available-for-sale, Amortized Cost	75		60
Available-for-sale securities, debt securities	$ 77		$ 64