Consolidated Statements Of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
OPERATING ACTIVITIES
Net income	$ 1,198	$ 1,235	$ 743
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for credit losses	74	(1)	74
Provision for deferred income taxes	12	24	79
Depreciation and amortization	114	120	121
Net periodic defined benefit credit	(29)	(18)	(18)
Share-based compensation expense	39	48	39
Net amortization of securities	2	3	6
Accretion of loan purchase discount	0	(1)	(3)
Net securities losses	7	19	0
Net gains on sales of foreclosed property	1	(1)	(3)
Net change in accrued income receivable	17	(45)	(33)
Net change in accrued expenses payable	(27)	49	41
Other, net	(318)	184	39
Net cash provided by operating activities	1,090	1,616	1,085
INVESTING ACTIVITIES
Maturities and redemptions of investment securities available-for-sale	2,262	1,781	1,615
Sales of investment securities available-for-sale	987	1,256	1,259
Purchases of investment securities available-for-sale	(3,346)	(3,032)	(3,112)
Maturities and redemptions of investment securities held-to-maturity	0	0	319
Net change in loans	(324)	(1,045)	(175)
Proceeds from sales of foreclosed property	1	8	22
Net increase in premises and equipment	(86)	(90)	(69)
Purchases of Federal Home Loan Bank stock	(201)	(41)	(42)
Redemptions of Federal Home Loan Bank stock	201	0	42
Proceeds from bank-owned life insurance settlements	10	9	18
Other, net	2	(2)	3
Net cash used in investing activities	(494)	(1,156)	(120)
FINANCING ACTIVITIES
Net change in deposits	1,711	(2,082)	(1,180)
Net change in short-term borrowings	27	34	(15)
Maturities of medium- and long-term debt	(350)	0	(500)
Issuances and advances of medium- and long-term debt	1,050	1,850	0
Terminations of medium- and long-term debt	0	0	(16)
Repurchases of common stock	(1,394)	(1,338)	(560)
Cash dividends paid on common stock	(402)	(263)	(180)
Issuances of common stock under employee stock plans	18	52	118
Other, net	1	3	(5)
Net cash provided by (used in) financing activities	661	(1,744)	(2,338)
Net increase (decrease) in cash and cash equivalents	1,257	(1,284)	(1,373)
Cash and cash equivalents at beginning of period	4,561	5,845	7,218
Cash and cash equivalents at end of period	5,818	4,561	5,845
Interest paid	462	261	122
Income taxes paid	266	200	336
Noncash investing and financing activities:
Loans transferred to other real estate	12	3	8
Residential mortgage-backed securities transferred from held-to-maturity to available-for-sale	0	1,266	0
Securities transferred from available-for-sale to equity securities	$ 0	$ 81	$ 0