Investments (Summary Of Investment Securities) (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Marketable Securities [Line Items]
Held-to-maturity, Amortized cost	$ 688
Held-to-maturity, fair value	691	$ 597
Available-for-sale, Amortized cost	13,841	13,686
Available-for-sale, Gross unrealized gains	402	126
Available-for-sale, Gross unrealized losses	42	87
Available-for-sale, at fair value	14,201	13,725
Total investment securities, Amortized cost	14,529	14,278
Total investment securities, Gross unrealized gains	407	131
Total investment securities, Gross unrealized losses	44	87
Total investment securities, estimated fair value	14,892	14,322
Municipal Securities [Member]
Marketable Securities [Line Items]
Held-to-maturity, Amortized cost	688	592
Held-to-maturity, Gross unrealized gains	5	5
Held-to-maturity, Gross unrealized losses	2	0
Held-to-maturity, fair value	691	597
Available-for-sale, Amortized cost	1,239	1,282
Available-for-sale, Gross unrealized gains	62	37
Available-for-sale, Gross unrealized losses	0	0
Available-for-sale, at fair value	1,301	1,319
US Treasury Securities [Member]
Marketable Securities [Line Items]
Available-for-sale, Amortized cost	100	25
Available-for-sale, Gross unrealized gains	0	0
Available-for-sale, Gross unrealized losses	0	0
Available-for-sale, at fair value	100	25
Agency Securities [Member]
Marketable Securities [Line Items]
Available-for-sale, Amortized cost	1,241	1,301
Available-for-sale, Gross unrealized gains	36	5
Available-for-sale, Gross unrealized losses	1	4
Available-for-sale, at fair value	1,276	1,302
Agency Guaranteed Mortgage Backed Securities [Member]
Marketable Securities [Line Items]
Available-for-sale, Amortized cost	9,911	9,518
Available-for-sale, Gross unrealized gains	304	83
Available-for-sale, Gross unrealized losses	2	42
Available-for-sale, at fair value	10,213	9,559
Small Business Administration Loan Backed Securities [Member]
Marketable Securities [Line Items]
Available-for-sale, Amortized cost	1,325	1,535
Available-for-sale, Gross unrealized gains	0	1
Available-for-sale, Gross unrealized losses	39	41
Available-for-sale, at fair value	1,286	1,495
Available-for-sale, Other debt securities [Member]
Marketable Securities [Line Items]
Available-for-sale, Amortized cost	25	25
Available-for-sale, Gross unrealized gains	0	0
Available-for-sale, Gross unrealized losses	0	0
Available-for-sale, at fair value	$ 25	$ 25

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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