Consolidated Statements of Income - USD ($) shares in Thousands, $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
INTEREST INCOME
Loans		$ 1,466	$ 1,516	$ 4,310	$ 4,578
Loans held for sale		18	18	43	40
Securities available for sale		408	298	1,211	789
Held-to-maturity securities		64	70	188	218
Trading account assets		11	15	44	45
Short-term investments		156	244	487	578
Other investments		8	14	25	47
Total interest income		2,131	2,175	6,308	6,295
INTEREST EXPENSE
Deposits		748	887	2,231	2,486
Federal funds purchased and securities sold under repurchase agreements		4	1	9	3
Bank notes and other short-term borrowings		14	43	75	140
Long-term debt		181	292	572	952
Total interest expense		947	1,223	2,887	3,581
NET INTEREST INCOME		1,184	952	3,421	2,714
Provision for credit losses		107	95	363	296
Net interest income after provision for credit losses		1,077	857	3,058	2,418
NONINTEREST INCOME
Trust and investment services income		150	140	435	415
Investment banking and debt placement fees		184	171	537	467
Cards and payments income		86	84	253	246
Service charges on deposit accounts		75	67	217	196
Corporate services income		72	69	213	206
Commercial mortgage servicing fees		73	73	219	190
Corporate-owned life insurance income		35	36	100	102
Consumer mortgage income		14	12	42	42
Operating lease income and other leasing gains		11	16	34	61
Other income		8	(2)	16	28
Net securities gains (losses)		(6)	(935)	(6)	(948)
Total noninterest income		702	(269)	2,060	1,005
NONINTEREST EXPENSE
Personnel		742	670	2,127	1,980
Net occupancy		65	66	201	199
Computer processing		105	104	319	307
Business services and professional fees		44	41	132	119
Equipment		20	20	61	60
Operating lease expense		9	14	30	48
Marketing		22	21	67	61
Other expense		170	158	525	542
Total noninterest expense		1,177	1,094	3,462	3,316
INCOME (LOSS) FROM CONTINUING OPERATIONS BEFORE INCOME TAXES		602	(506)	1,656	107
Income taxes		112	(95)	337	26
Income (loss) from continuing operations		490	(411)	1,319	81
Income (loss) from discontinued operations		(1)	1	0	2
NET INCOME (LOSS)		489	(410)	1,319	83
Income (loss) from continuing operations attributable to Key common shareholders		454	(447)	1,211	(27)
Net income (loss) attributable to Key common shareholders		$ 453	$ (446)	$ 1,211	$ (25)
Per Common Share:
Income (loss) from continuing operations attributable to Key common shareholders (in usd per share)		$ 0.41	$ (0.47)	$ 1.10	$ (0.03)
Income (loss) from discontinued operations, net of taxes (in usd per share)		0	0	0	0
Net income (loss) attributable to Key common shareholders (in usd per share)	[1]	0.41	(0.47)	1.10	(0.03)
Per Common Share — assuming dilution:
Income (loss) from continuing operations attributable to Key common shareholders (in usd per share)		0.41	(0.47)	1.09	(0.03)
Income (loss) from discontinued operations, net of taxes (in usd per share)		0	0	0	0
Net income (loss) attributable to Key common shareholders (in usd per share)	[1]	$ 0.41	$ (0.47)	$ 1.09	$ (0.03)
Weighted-average Common Shares outstanding (in shares)		1,100,830	948,979	1,099,520	936,962
Effect of Common Share options and other stock awards (in shares)		9,845	0	8,864	0
Weighted-average Common Shares and potential Common Shares outstanding (in shares)	[2]	1,110,675	948,979	1,108,384	936,962

[1] EPS may not foot due to rounding

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