Consolidated Statements of Income - USD ($) shares in Thousands, $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
INTEREST INCOME
Loans		$ 928	$ 746	$ 2,753	$ 1,875
Loans held for sale		17	10	39	23
Securities available for sale		91	88	276	237
Held-to-maturity securities		55	30	161	78
Trading account assets		7	4	21	17
Short-term investments		6	7	14	17
Other investments		5	5	12	10
Total interest income		1,109	890	3,276	2,257
INTEREST EXPENSE
Deposits		72	49	196	114
Federal funds purchased and securities sold under repurchase agreements		0	0	1	0
Bank notes and other short-term borrowings		3	2	12	7
Long-term debt		86	59	228	155
Total interest expense		161	110	437	276
NET INTEREST INCOME		948	780	2,839	1,981
Provision for credit losses		51	59	180	200
Net interest income after provision for credit losses		897	721	2,659	1,781
NONINTEREST INCOME
Trust and investment services income		135	122	404	341
Investment banking and debt placement fees		141	156	403	325
Service charges on deposit accounts		91	85	268	218
Operating lease income and other leasing gains		16	6	69	41
Corporate services income		54	51	163	154
Cards and payments income		75	66	210	164
Corporate-owned life insurance income		31	29	94	85
Consumer mortgage income		7	6	19	11
Mortgage servicing fees		21	15	54	37
Net gains (losses) from principal investing		3	5	4	16
Other income	[1]	18	8	134	61
Total noninterest income		592	549	1,822	1,453
NONINTEREST EXPENSE
Personnel		558	594	1,665	1,425
Net occupancy		74	73	239	193
Computer processing		56	70	171	158
Business services and professional fees		49	76	140	157
Equipment		29	26	83	68
Operating lease expense		24	15	64	42
Marketing		34	32	85	66
FDIC assessment		21	21	62	38
Intangible asset amortization		25	13	69	28
OREO expense, net		3	3	8	6
Other expense		119	159	414	355
Total noninterest expense		992	1,082	3,000	2,536
INCOME (LOSS) FROM CONTINUING OPERATIONS BEFORE INCOME TAXES		497	188	1,481	698
Income taxes		134	16	386	141
INCOME (LOSS) FROM CONTINUING OPERATIONS		363	172	1,095	557
Income (loss) from discontinued operations, net of taxes $, $1, $3 and, $3 (see note 12)		1	1	6	5
NET INCOME (LOSS)		364	173	1,101	562
Less: Net income (loss) attributable to noncontrolling interests		0	1	1	0
NET INCOME (LOSS) ATTRIBUTABLE TO KEY		364	172	1,100	562
Income (loss) from continuing operations attributable to Key common shareholders		349	165	1,038	540
Net income (loss) attributable to Key common shareholders		$ 350	$ 166	$ 1,044	$ 545
Per common share:
Income (loss) from continuing operations attributable to Key common shareholders (in usd per share)		$ 0.32	$ 0.17	$ 0.96	$ 0.61
Income (loss) from discontinued operations, net of taxes (in usd per share)		0.00	0.00	0.01	0.01
Net income (loss) attributable to Key common shareholders (in usd per share)	[2]	0.32	0.17	0.97	0.62
Per common share — assuming dilution:
Income (loss) from continuing operations attributable to Key common shareholders (in usd per share)		0.32	0.16	0.95	0.60
Income (loss) from discontinued operations, net of taxes (in usd per share)		0.00	0.00	0.01	0.01
Net income (loss) attributable to Key common shareholders (in usd per share)	[2]	0.32	0.17	0.96	0.61
Cash dividends declared per common share (in usd per share)		$ 0.095	$ 0.085	$ 0.275	$ 0.245
Weighted-average common shares outstanding (in shares)		1,073,390	982,080	1,075,296	880,824
Effect of convertible preferred stock (in shares)		0	0	0	0
Effect of common share options and other stock awards (in shares)		15,451	12,580	16,359	8,965
Weighted-average common shares and potential common shares outstanding (in shares)	[3]	1,088,841	994,660	1,091,655	889,789

[1] For the three months ended September 30, 2017, net securities gains totaled less than $1 million. For the three months ended September 30, 2016, net securities losses totaled $6 million. For the three months ended September 30, 2017, and September 30, 2016, 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.