Investments (Summary of Amount of Gross Unrealized Losses for Debt Securities and Estimated Fair Value) (Details) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Gross unrealized losses
Total investment securities, less than 12 months	$ 2,006	$ 237
Total investment securities, 12 months or more	752	89
Total investment securities, total	2,758	326
Estimated fair value
Total investment securities, less than 12 months	19,753	14,137
Total investment securities, 12 months or more	4,900	1,902
Total investment securities, total	24,653	16,039
Municipal securities
Gross unrealized losses
Held-to-maturity, less than 12 Months	14	1
Available-for-sale, less than 12 Months	86	4
Held-to-maturity, 12 months or more	22	1
Available-for-sale, 12 Months or more	15	0
Held-to-maturity, total	36	2
Available-for-sale, total	101	4
Estimated fair value
Held-to-maturity, less than 12 Months	327	88
Available-for-sale, less than 12 Months	1,189	327
Held-to-maturity, 12 months or more	96	68
Available-for-sale, 12 months or more	84	8
Held-to-maturity, total	423	156
Available-for-sale, total	1,273	335
U.S. Treasury, agencies and corporations
Gross unrealized losses
Available-for-sale, less than 12 Months	60	0
Available-for-sale, 12 Months or more	55	21
Available-for-sale, total	115	21
Estimated fair value
Available-for-sale, less than 12 Months	341	0
Available-for-sale, 12 months or more	101	134
Available-for-sale, total	442	134
Agency securities
Gross unrealized losses
Available-for-sale, less than 12 Months	17	1
Available-for-sale, 12 Months or more	5	0
Available-for-sale, total	22	1
Estimated fair value
Available-for-sale, less than 12 Months	729	121
Available-for-sale, 12 months or more	96	1
Available-for-sale, total	825	122
Agency guaranteed mortgage-backed securities
Gross unrealized losses
Available-for-sale, less than 12 Months	1,827	231
Available-for-sale, 12 Months or more	632	39
Available-for-sale, total	2,459	270
Estimated fair value
Available-for-sale, less than 12 Months	17,069	13,574
Available-for-sale, 12 months or more	3,886	942
Available-for-sale, total	20,955	14,516
Small Business Administration loan-backed securities
Gross unrealized losses
Available-for-sale, less than 12 Months	1	0
Available-for-sale, 12 Months or more	23	28
Available-for-sale, total	24	28
Estimated fair value
Available-for-sale, less than 12 Months	84	27
Available-for-sale, 12 months or more	637	749
Available-for-sale, total	721	776
Other
Gross unrealized losses
Available-for-sale, less than 12 Months	1	0
Available-for-sale, 12 Months or more	0	0
Available-for-sale, total	1	0
Estimated fair value
Available-for-sale, less than 12 Months	14	0
Available-for-sale, 12 months or more	0	0
Available-for-sale, total	14	0
Available-for-sale
Gross unrealized losses
Available-for-sale, less than 12 Months	1,992	236
Available-for-sale, 12 Months or more	730	88
Available-for-sale, total	2,722	324
Estimated fair value
Available-for-sale, less than 12 Months	19,426	14,049
Available-for-sale, 12 months or more	4,804	1,834
Available-for-sale, total	$ 24,230	$ 15,883