Investments (Amortized Cost and Fair Value of Available-for-Sale Debt Securities by Contractual Maturity) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Schedule of Investments [Line Items]
Due in one year or less, Amortized Cost	$ 2,603
Due after one year through five years, Amortized Cost	12,885
Due after five years through ten years, Amortized Cost	11,342
Due after ten years, Amortized Cost	4,152
Total debt securities - available-for-sale, Amortized Cost	39,669	$ 38,079
Due in one year or less, Fair Value	2,614
Due after one year through five years, Fair Value	13,065
Due after five years through ten years, Fair Value	11,524
Due after ten years, Fair Value	4,275
Debt Securities, Available-for-sale	40,217	39,828
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, within One Year, Amortized Cost	235
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, within One Year, Fair Value	236
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Amortized Cost	355
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Fair Value	354
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Amortized Cost	28
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Fair Value	29
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, after 10 Years, Amortized Cost	23
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, after 10 Years, Fair Value	24
Debt Securities, Held-to-maturity	641	638
Debt Securities, Held-to-maturity, Fair Value	643	647
U.S. Agency Mortgage-Backed Securities [Member]
Schedule of Investments [Line Items]
Mortgage-backed securities, Amortized Cost	5,868
Total debt securities - available-for-sale, Amortized Cost	5,868	6,849
Debt Securities, Available-for-sale	5,901	7,091
Mortgage-backed securities, Fair Value	5,901
Non-U.S. Agency Mortgage-Backed Securities [Member]
Schedule of Investments [Line Items]
Mortgage-backed securities, Amortized Cost	2,819
Total debt securities - available-for-sale, Amortized Cost	2,819	2,116
Debt Securities, Available-for-sale	2,838	$ 2,207
Mortgage-backed securities, Fair Value	$ 2,838