Investments (Amortized Cost and Fair Value of Available-for-Sale Debt Securities by Contractual Maturity) (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Schedule of Investments [Line Items]
Due in one year or less, Amortized Cost	$ 4,713
Due after one year through five years, Amortized Cost	13,135
Due after five years through ten years, Amortized Cost	12,210
Due after ten years, Amortized Cost	5,412
Total debt securities - available-for-sale, Amortized Cost	45,926	$ 39,669
Due in one year or less, Fair Value	4,682
Due after one year through five years, Fair Value	12,404
Due after five years through ten years, Fair Value	10,897
Due after ten years, Fair Value	4,968
Debt Securities, Available-for-sale	42,321	40,217
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, within One Year, Amortized Cost	374
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, within One Year, Fair Value	369
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Amortized Cost	265
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Fair Value	256
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Amortized Cost	37
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Fair Value	36
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, after 10 Years, Amortized Cost	20
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, after 10 Years, Fair Value	18
Debt Securities, Held-to-maturity	696	641
Debt Securities, Held-to-maturity, Fair Value	679	643
U.S. Agency Mortgage-Backed Securities [Member]
Schedule of Investments [Line Items]
Mortgage-backed securities, Amortized Cost	7,379
Total debt securities - available-for-sale, Amortized Cost	7,379	5,868
Debt Securities, Available-for-sale	6,586	5,901
Mortgage-backed securities, Fair Value	6,586
Non-U.S. Agency Mortgage-Backed Securities [Member]
Schedule of Investments [Line Items]
Mortgage-backed securities, Amortized Cost	3,077
Total debt securities - available-for-sale, Amortized Cost	3,077	2,819
Debt Securities, Available-for-sale	2,784	$ 2,838
Mortgage-backed securities, Fair Value	$ 2,784