Investments (Contractual Maturities Debt Securities) (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Amortized cost
Total debt investment securities	$ 18,052	$ 15,417
Due in one year or less	104
Due after one year through five years	1,448
Due after five years through ten years	1,691
Due after ten years	$ 14,809
Avg yield
Total debt investment securities	1.72%
Due in one year or less	1.92%
Due after one year through five years	1.85%
Due after five years through ten years	1.98%
Due after ten years	1.67%
Amortized cost
Total investment securities	$ 18,672	$ 16,053
Due in one year or less	275
Due after one year through five years	1,608
Due after five years through ten years	1,863
Due after ten years	$ 14,926
Avg yield
Total debt investment securities	1.75%
Due in one year or less	1.76%
Due after one year through five years	2.00%
Due after five years through ten years	2.05%
Due after ten years	1.68%
Municipal securities
Amortized cost
Total debt investment securities	$ 620
Due in one year or less	171
Due after one year through five years	160
Due after five years through ten years	172
Due after ten years	$ 117
Avg yield
Total debt investment securities	2.75%
Due in one year or less	1.67%
Due after one year through five years	3.37%
Due after five years through ten years	2.81%
Due after ten years	3.36%
Amortized cost
Total debt investment securities	$ 1,522
Due in one year or less	104
Due after one year through five years	643
Due after five years through ten years	506
Due after ten years	$ 269
Avg yield
Total debt investment securities	2.33%
Due in one year or less	1.92%
Due after one year through five years	2.43%
Due after five years through ten years	2.30%
Due after ten years	2.31%
U.S. Treasury securities
Amortized cost
Total debt investment securities	$ 155
Due in one year or less	0
Due after one year through five years	0
Due after five years through ten years	0
Due after ten years	$ 155
Avg yield
Total debt investment securities	1.28%
Due in one year or less	0.00%
Due after one year through five years	0.00%
Due after five years through ten years	0.00%
Due after ten years	1.28%
Agency securities
Amortized cost
Total debt investment securities	$ 991
Due in one year or less	0
Due after one year through five years	361
Due after five years through ten years	267
Due after ten years	$ 363
Avg yield
Total debt investment securities	2.12%
Due in one year or less	0.00%
Due after one year through five years	1.36%
Due after five years through ten years	2.52%
Due after ten years	2.59%
Agency guaranteed mortgage-backed securities
Amortized cost
Total debt investment securities	$ 14,233
Due in one year or less	0
Due after one year through five years	391
Due after five years through ten years	725
Due after ten years	$ 13,117
Avg yield
Total debt investment securities	1.65%
Due in one year or less	0.00%
Due after one year through five years	1.41%
Due after five years through ten years	1.63%
Due after ten years	1.66%
Small Business Administration loan-backed securities
Amortized cost
Total debt investment securities	$ 1,076
Due in one year or less	0
Due after one year through five years	53
Due after five years through ten years	133
Due after ten years	$ 890
Avg yield
Total debt investment securities	1.37%
Due in one year or less	0.00%
Due after one year through five years	1.42%
Due after five years through ten years	1.56%
Due after ten years	1.34%
Other debt securities
Amortized cost
Total debt investment securities	$ 75
Due in one year or less	0
Due after one year through five years	0
Due after five years through ten years	60
Due after ten years	$ 15
Avg yield
Total debt investment securities	2.15%
Due in one year or less	0.00%
Due after one year through five years	0.00%
Due after five years through ten years	1.96%
Due after ten years	2.90%