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Regulatory Matters - Key's and KeyBank's Actual Capital Amounts and Ratios, Minimum Capital Amounts and Ratios (Details) $ in Millions | Dec. 31, 2025 USD ($) | Dec. 31, 2024 USD ($)
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KeyBank (consolidated) |  |
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] |  |
Total risk-based capital, actual amount | $ 21,198 | $ 20,518
Common equity Tier 1 risk-based capital, actual amount | 18,376 | 17,560
Tier 1 risk- based capital, actual amount | 18,376 | 17,560
Tier 1 risk- based capital, leverage amount | $ 18,376 | $ 17,560
Total risk-based capital, actual ratio | 0.1471 | 0.1512
Common equity Tier 1 risk-based capital, actual ratio | 0.1275 | 0.1294
Tier 1 risk-based capital, actual ratio | 0.1275 | 0.1294
Tier 1 risk- based capital, leverage actual ratio | 0.0996 | 0.0942
Total risk-based capital, regulatory minimum, ratio | 0.0800 | 0.0800
Common equity Tier 1 risk-based capital, regulatory minimum, ratio | 0.0450 | 0.0450
Tier 1 risk-based capital, regulatory minimum, ratio | 0.0600 | 0.0600
Tier 1 risk-based capital, leverage regulatory minimum ratio | 0.0400 | 0.0400
Total risk-based capital, regulatory minimum with stress capital buffer | 0.1120 | 0.1110
Common equity Tier 1 risk-based capital, regulatory minimum with stress capital buffer | 0.0770 | 0.0760
Tier 1 risk-based capital, regulatory minimum with stress capital buffer | 0.0920 | 0.0910
Tier 1 risk based capital leverage, regulatory minimum with stress capital buffer | 0.0400 | 0.0400
Total risk-based capital, capitalized | 0.1000 | 0.1000
Common equity Tier 1 risk-based capital, capitalized | 0.0650 | 0.0650
Tier 1 risk-based capital, capitalized | 0.0800 | 0.0800
Tier 1 risk-based capital, leverage capitalized | 0.0500 | 0.0500
Parent |  |
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] |  |
Total risk-based capital, actual amount | $ 22,910 | $ 22,336
Common equity Tier 1 risk-based capital, actual amount | 17,195 | 16,489
Tier 1 risk- based capital, actual amount | 19,641 | 18,934
Tier 1 risk- based capital, leverage amount | $ 19,641 | $ 18,934
Total risk-based capital, actual ratio | 0.1570 | 0.1615
Common equity Tier 1 risk-based capital, actual ratio | 0.1178 | 0.1192
Tier 1 risk-based capital, actual ratio | 0.1346 | 0.1369
Tier 1 risk- based capital, leverage actual ratio | 0.1050 | 0.1003
Total risk-based capital, regulatory minimum, ratio | 0.0800 | 0.0800
Common equity Tier 1 risk-based capital, regulatory minimum, ratio | 0.0450 | 0.0450
Tier 1 risk-based capital, regulatory minimum, ratio | 0.0600 | 0.0600
Tier 1 risk-based capital, leverage regulatory minimum ratio | 0.0400 | 0.0400
Total risk-based capital, regulatory minimum with stress capital buffer | 0.1120 | 0.1110
Common equity Tier 1 risk-based capital, regulatory minimum with stress capital buffer | 0.0770 | 0.0760
Tier 1 risk-based capital, regulatory minimum with stress capital buffer | 0.0920 | 0.0910
Tier 1 risk based capital leverage, regulatory minimum with stress capital buffer | 0.0400 | 0.0400

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