Investments in Debt and Equity Securities - Summary of cost basis and fair value of the available-for-sale debt securities by contractual maturity (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Cost Basis
Due in one year or less	$ 940		$ 940
Due after one year through five years	1,812		1,812
Due after five years through ten years	262		262
Due after ten years	68		68
Debt securities, available-for-sale, cost basis	3,651		3,651		$ 3,311
Fair Value
Due in one year or less	929		929
Due after one year through five years	1,737		1,737
Due after five years through ten years	248		248
Due after ten years	67		67
Debt securities	3,493		3,493		3,164
Available-for-sale Securities, Proceeds, Gains and Losses
Proceeds from the sale of available-for-sale securities	271	$ 204	710	$ 474
Gross gains from the sale of available-for-sale securities	0	0	0	1
Gross losses from the sale of available-for-sale securities	1	$ 0	1	$ 1
U.S. governmental agency
Cost Basis
Debt securities, available-for-sale, cost basis	429		429		364
Fair Value
Debt securities	384		384		333
Residential
Cost Basis
Debt securities, available-for-sale, cost basis	3		3		3
Fair Value
Debt securities	2		2		2
Commercial
Cost Basis
Debt securities, available-for-sale, cost basis	137		137		127
Fair Value
Debt securities	$ 126		$ 126		$ 117