Investments (Summary of Investment Securities) (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Amortized cost
Held-to-maturity	$ 10,065	$ 10,382
Available-for-sale	11,040	11,759
Total HTM and AFS investment securities	21,105	22,141
Gross unrealized gains 1
Held-to-maturity	2	156
Available-for-sale	1	0
Total HTM and AFS investment securities	3	156
Gross unrealized losses
Held-to-maturity	176	72
Available-for-sale	1,558	1,459
Estimated fair value
Held-to-maturity, Estimated fair value	9,891	10,466
Available-for-sale	9,483	10,300
Total HTM and AFS investment securities	19,374	20,766
Total HTM and AFS investment securities	1,734	1,531
U.S. Treasury securities
Amortized cost
Available-for-sale	570	585
Gross unrealized gains 1
Available-for-sale	0	0
Gross unrealized losses
Available-for-sale	109	93
Estimated fair value
Available-for-sale	461	492
Agency securities
Amortized cost
Held-to-maturity	152	93
Available-for-sale	503	663
Gross unrealized gains 1
Held-to-maturity	0	0
Available-for-sale	0	0
Gross unrealized losses
Held-to-maturity	8	6
Available-for-sale	32	33
Estimated fair value
Held-to-maturity, Estimated fair value	144	87
Available-for-sale	471	630
Agency guaranteed mortgage-backed securities
Amortized cost
Held-to-maturity	9,583	9,935
Available-for-sale	8,124	8,530
Gross unrealized gains 1
Held-to-maturity	2	156
Available-for-sale	1	0
Gross unrealized losses
Held-to-maturity	148	50
Available-for-sale	1,302	1,239
Estimated fair value
Held-to-maturity, Estimated fair value	9,437	10,041
Available-for-sale	6,823	7,291
Small Business Administration loan-backed securities
Amortized cost
Available-for-sale	516	571
Gross unrealized gains 1
Available-for-sale	0	0
Gross unrealized losses
Available-for-sale	23	25
Estimated fair value
Available-for-sale	493	546
Municipal securities
Amortized cost
Held-to-maturity	330	354
Available-for-sale	1,302	1,385
Gross unrealized gains 1
Held-to-maturity	0	0
Available-for-sale	0	0
Gross unrealized losses
Held-to-maturity	20	16
Available-for-sale	91	67
Estimated fair value
Held-to-maturity, Estimated fair value	310	338
Available-for-sale	1,211	1,318
Other debt securities
Amortized cost
Available-for-sale	25	25
Gross unrealized gains 1
Available-for-sale	0	0
Gross unrealized losses
Available-for-sale	1	2
Estimated fair value
Available-for-sale	$ 24	23
Available-for-sale, Unrealized Gains, Other
Gross unrealized gains 1
Available-for-sale		$ 1