Consolidated Statements of Income - USD ($) shares in Thousands, $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
INTEREST INCOME
Loans		$ 2,773	$ 2,149	$ 2,110
Loans held for sale		34	37	21
Securities available for sale		329	293	277
Held-to-maturity securities		122	96	93
Trading account assets		23	21	25
Short-term investments		22	8	6
Other investments		16	18	22
Total interest income		3,319	2,622	2,554
INTEREST EXPENSE
Deposits		171	105	117
Federal funds purchased and securities sold under repurchase agreements		1	0	2
Bank notes and other short-term borrowings		10	9	9
Long-term debt		218	160	133
Total interest expense		400	274	261
NET INTEREST INCOME		2,919	2,348	2,293
Provision for credit losses		266	166	57
Net interest income after provision for credit losses		2,653	2,182	2,236
NONINTEREST INCOME
Trust and investment services income		464	433	403
Investment banking and debt placement fees		482	445	397
Service charges on deposit accounts		302	256	261
Operating lease income and other leasing gains		62	73	96
Corporate services income		215	198	178
Cards and payments income		233	183	166
Corporate-owned life insurance income		125	127	118
Consumer mortgage income		17	12	10
Mortgage servicing fees		57	48	46
Net gains (losses) from principal investing		20	51	78
Other income	[1]	94	54	44
Total noninterest income		2,071	1,880	1,797
NONINTEREST EXPENSE
Personnel		2,073	1,652	1,591
Net occupancy		305	255	261
Computer processing		255	164	158
Business services and professional fees		235	159	156
Equipment		98	88	96
Operating lease expense		59	47	42
Marketing		101	57	49
FDIC assessment		61	32	30
Intangible asset amortization		55	36	39
OREO expense, net		9	6	5
Other expense		505	344	334
Total noninterest expense		3,756	2,840	2,761
INCOME (LOSS) FROM CONTINUING OPERATIONS BEFORE INCOME TAXES		968	1,222	1,272
Income taxes		179	303	326
INCOME (LOSS) FROM CONTINUING OPERATIONS		789	919	946
Income (loss) from discontinued operations, net of taxes of $1, $1, and ($23) (see Note 14)		1	1	(39)
NET INCOME (LOSS)		790	920	907
Less: Net income (loss) attributable to noncontrolling interests		(1)	4	7
NET INCOME (LOSS) ATTRIBUTABLE TO KEY		791	916	900
Income (loss) from continuing operations attributable to Key common shareholders		753	892	917
Net income (loss) attributable to Key common shareholders		$ 754	$ 893	$ 878
Per common share:
Income (loss) from continuing operations attributable to Key common shareholders (in dollars per share)		$ 0.81	$ 1.06	$ 1.05
Income (loss) from discontinued operations, net of taxes (in dollars per share)		0.00	0.00	(0.04)
Net income (loss) attributable to Key common shareholders (in dollars per share)	[2]	0.81	1.06	1.01
Per common share — assuming dilution:
Income (loss) from continuing operations attributable to Key common shareholders (in dollars per share)		0.80	1.05	1.04
Income (loss) from discontinued operations, net of taxes (in dollars per share)		0.00	0.00	(0.04)
Net income (loss) attributable to Key common shareholders (in dollars per share)	[2]	0.80	1.05	0.99
Cash dividends declared per common share (in dollars per share)		$ 0.33	$ 0.29	$ 0.250
Weighted-average common shares outstanding (000) (in shares)		927,816	836,846	871,464
Effect of convertible preferred stock (in shares)		0	0	0
Effect of common share options and other stock awards (in shares)		10,720	7,643	6,735
Weighted-average common shares and potential common shares outstanding (000) (in shares)	[3]	938,536	844,489	878,199

[1] Net securities gains (losses) totaled less than $1 million for the years ended December 31, 2016, 2015, and 2014. For 2016, 2015, and 2014, 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.