Shareholders' Equity - Key's and KeyBank's Actual Capital Amounts and Ratios, Minimum Capital Amounts and Ratios (Details) $ in Millions	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Key
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital to Net Risk-Weighted Assets, Actual Amount	$ 18,030	$ 17,976
Tier 1 Capital to Average Quarterly Tangible Assets, Amount	15,549	14,907
Tier 1 Capital to Net Risk-Weighted Assets, Actual Amount	$ 15,549	$ 14,907
Total Capital to Net Risk-Weighted Assets, Actual Ratio	0.1249	0.1340
Tier 1 Capital to Net Risk-Weighted Assets, Actual Ratio	0.1077	0.1111
Tier 1 Capital to Average Quarterly Tangible Assets, Actual Ratio	0.0847	0.0894
Total Capital to Net Risk-Weighted Assets, to Meet Minimum Capital Adequacy Requirements, Amount	$ 11,552	$ 10,736
Tier 1 Capital to Net Risk-Weighted Assets, to Meet Minimum Capital Adequacy Requirements, Amount	8,664	8,052
Tier 1 Capital to Average Quarterly Tangible Assets to Meet Minimum Capital Adequacy Requirements, Amount	$ 7,344	$ 6,671
Total Capital to Net Risk-Weighted Assets, to Meet Minimum Capital Adequacy Requirements, Ratio	0.0800	0.0800
Tier 1 Capital to Net Risk-Weighted Assets, to Meet Minimum Capital Adequacy Requirements, Ratio	0.0600	0.0600
Tier 1 Capital to Average Quarterly Tangible Assets to Meet Minimum Capital Adequacy Requirements, Ratio	0.0400	0.0400
KeyBank (consolidated)
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital to Net Risk-Weighted Assets, Actual Amount	$ 17,211	$ 17,195
Tier 1 Capital to Average Quarterly Tangible Assets, Amount	15,143	14,539
Tier 1 Capital to Net Risk-Weighted Assets, Actual Amount	$ 15,143	$ 14,539
Total Capital to Net Risk-Weighted Assets, Actual Ratio	0.1221	0.1309
Tier 1 Capital to Net Risk-Weighted Assets, Actual Ratio	0.1075	0.1107
Tier 1 Capital to Average Quarterly Tangible Assets, Actual Ratio	0.0837	0.0880
Total Capital to Net Risk-Weighted Assets, to Meet Minimum Capital Adequacy Requirements, Amount	$ 11,274	$ 10,511
Tier 1 Capital to Net Risk-Weighted Assets, to Meet Minimum Capital Adequacy Requirements, Amount	8,456	7,884
Tier 1 Capital to Average Quarterly Tangible Assets to Meet Minimum Capital Adequacy Requirements, Amount	$ 7,241	$ 6,605
Total Capital to Net Risk-Weighted Assets, to Meet Minimum Capital Adequacy Requirements, Ratio	0.0800	0.0800
Tier 1 Capital to Net Risk-Weighted Assets, to Meet Minimum Capital Adequacy Requirements, Ratio	0.0600	0.0600
Tier 1 Capital to Average Quarterly Tangible Assets to Meet Minimum Capital Adequacy Requirements, Ratio	0.0400	0.0400
Total Capital to Net Risk-Weighted Assets, to Qualify as Well Capitalized Under Federal Deposit Insurance Act, Amount	$ 14,093	$ 13,139
Tier 1 Capital to Net Risk-Weighted Assets, to Qualify as Well Capitalized Under Federal Deposit Insurance Act, Amount	11,274	10,511
Tier 1 Capital to Average Quarterly Tangible Assets to Qualify as Well Capitalized Under Federal Deposit Insurance Act, Amount	$ 9,051	$ 8,256
Total Capital to Net Risk-Weighted Assets, to Qualify as Well Capitalized Under Federal Deposit Insurance Act, Ratio	0.1000	0.1000
Tier 1 Capital to Net Risk-Weighted Assets, to Qualify as Well Capitalized Under Federal Deposit Insurance Act, Ratio	0.0800	0.0800
Tier 1 Capital to Average Quarterly Tangible Assets to Qualify as Well Capitalized Under Federal Deposit Insurance Act, Ratio	5.00%	5.00%

Tangible Capital Qualify As Well Capitalized Under Federal Deposit Insurance Act

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