Investments (Summary of Investment Securities) (Details) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Amortized cost
Available-for-sale	$ 28,012	$ 24,202
Total HTM and AFS investment securities	28,626	24,643
Gross unrealized gains
Available-for-sale	7	170
Total HTM and AFS investment securities	7	174
Gross unrealized losses
Available-for-sale	2,722	324
Total HTM and AFS investment securities	2,758	326
Estimated fair value
Held-to-maturity, Estimated fair value	578	443
Available-for-sale	25,297	24,048
Total HTM and AFS investment securities	25,875	24,491
Municipal securities
Amortized cost
Held-to-maturity	614	441
Available-for-sale	1,835	1,652
Gross unrealized gains
Held-to-maturity	0	4
Available-for-sale	3	46
Gross unrealized losses
Held-to-maturity	36	2
Available-for-sale	101	4
Estimated fair value
Held-to-maturity, Estimated fair value	578	443
Available-for-sale	1,737	1,694
U.S. Treasury securities
Amortized cost
Available-for-sale	557	155
Gross unrealized gains
Available-for-sale	0	0
Gross unrealized losses
Available-for-sale	115	21
Estimated fair value
Available-for-sale	442	134
Agency securities
Amortized cost
Available-for-sale	899	833
Gross unrealized gains
Available-for-sale	0	13
Gross unrealized losses
Available-for-sale	22	1
Estimated fair value
Available-for-sale	877	845
Agency guaranteed mortgage-backed securities
Amortized cost
Available-for-sale	23,768	20,549
Gross unrealized gains
Available-for-sale	2	108
Gross unrealized losses
Available-for-sale	2,459	270
Estimated fair value
Available-for-sale	21,311	20,387
Small Business Administration loan-backed securities
Amortized cost
Available-for-sale	878	938
Gross unrealized gains
Available-for-sale	2	2
Gross unrealized losses
Available-for-sale	24	28
Estimated fair value
Available-for-sale	856	912
Other debt securities
Amortized cost
Available-for-sale	75	75
Gross unrealized gains
Available-for-sale	0	1
Gross unrealized losses
Available-for-sale	1	0
Estimated fair value
Available-for-sale	$ 74	$ 76