Consolidated Statements of Income - USD ($) shares in Thousands, $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
INTEREST INCOME
Loans		$ 4,267	$ 4,023	$ 3,677
Loans held for sale		63	66	52
Securities available for sale		537	409	369
Held-to-maturity securities		262	284	222
Trading account assets		32	29	27
Short-term investments		61	46	26
Other investments		13	21	17
Total interest income		5,235	4,878	4,390
INTEREST EXPENSE
Deposits		853	517	278
Federal funds purchased and securities sold under repurchase agreements		2	11	1
Bank notes and other short-term borrowings		17	21	15
Long-term debt		454	420	319
Total interest expense		1,326	969	613
NET INTEREST INCOME		3,909	3,909	3,777
Provision for credit losses		445	246	229
Net interest income after provision for credit losses		3,464	3,663	3,548
NONINTEREST INCOME
Trust and investment services income		475	499	535
Investment banking and debt placement fees		630	650	603
Service charges on deposit accounts		337	349	357
Operating lease income and other leasing gains		162	89	96
Corporate services income		236	233	219
Cards and payments income		275	270	287
Corporate-owned life insurance income		136	137	131
Consumer mortgage income		46	30	26
Mortgage servicing fees		94	82	71
Other income	[1]	68	176	153
Total noninterest income		2,459	2,515	2,478
NONINTEREST EXPENSE
Personnel		2,250	2,309	2,278
Net occupancy		293	308	331
Computer processing		214	210	225
Business services and professional fees		186	184	192
Equipment		100	105	114
Operating lease expense		123	120	92
Marketing		96	102	120
FDIC assessment		31	72	82
Intangible asset amortization		89	99	95
OREO expense, net		13	6	11
Other expense		506	460	558
Total noninterest expense		3,901	3,975	4,098
INCOME (LOSS) FROM CONTINUING OPERATIONS BEFORE INCOME TAXES		2,022	2,203	1,928
Income taxes		314	344	637
INCOME (LOSS) FROM CONTINUING OPERATIONS		1,708	1,859	1,291
Income (loss) from discontinued operations		9	7	7
NET INCOME (LOSS)		1,717	1,866	1,298
Less: Net income (loss) attributable to noncontrolling interests		0	0	2
NET INCOME (LOSS) ATTRIBUTABLE TO KEY		1,717	1,866	1,296
Income (loss) from continuing operations attributable to Key common shareholders		1,611	1,793	1,219
Net income (loss) attributable to Key common shareholders		$ 1,620	$ 1,800	$ 1,226
Per Common Share:
Income (loss) from continuing operations attributable to Key common shareholders (in dollars per share)		$ 1.62	$ 1.72	$ 1.13
Income (loss) from discontinued operations, net of taxes (in dollars per share)		0.01	0.01	0.01
Net income (loss) attributable to Key common shareholders (in dollars per share)	[2]	1.63	1.73	1.14
Per Common Share — assuming dilution:
Income (loss) from continuing operations attributable to Key common shareholders (in dollars per share)		1.61	1.70	1.12
Income (loss) from discontinued operations, net of taxes (in dollars per share)		0.01	0.01	0.01
Net income (loss) attributable to Key common shareholders (in dollars per share)	[2]	1.62	1.71	1.13
Cash dividends declared per common share (in dollars per share)		$ 0.71	$ 0.565	$ 0.38
Weighted-average common shares outstanding (in shares)		992,091	1,040,890	1,072,078
Effect of convertible preferred stock (in shares)		0	0	0
Effect of common share options and other stock awards (in shares)		10,163	13,792	16,515
Weighted-average common shares and potential common shares outstanding (in shares)	[3]	1,002,254	1,054,682	1,088,593

[1] Net securities gains (losses) totaled $20 million for the year ended December 31, 2019, less than $1 million for the year ended December 31, 2018, and $1 million for the year ended December 31, 2017. For 2019, 2018, and 2017, we did not have any impairment losses related to securities.

[2] EPS may not foot due to rounding.

[3] Assumes conversion of Common Share options and other stock awards and/or convertible preferred stock, as applicable.