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Loans (Summary of Loan Portfolio) (Detail) - USD ($) $ in Thousands | Mar. 31, 2022 | Dec. 31, 2021 | Mar. 31, 2021
--- | --- | --- | ---
Loans [Line Items] |  |  |
Total loans, net of unearned income | $ 35,280,547 | $ 34,789,104 | $ 33,171,233
Total loans, net of unearned income, percentage | 100.00% | 100.00% | 100.00%
Commercial |  |  |
Loans [Line Items] |  |  |
Total loans, net of unearned income | $ 11,583,963 | $ 11,904,068 | $ 12,708,207
Total loans, net of unearned income, percentage | 33.00% | 34.00% | 38.00%
Commercial real estate |  |  |
Loans [Line Items] |  |  |
Total loans, net of unearned income | $ 9,235,074 | $ 8,990,286 | $ 8,544,779
Total loans, net of unearned income, percentage | 26.00% | 26.00% | 26.00%
Home equity |  |  |
Loans [Line Items] |  |  |
Total loans, net of unearned income | $ 321,435 | $ 335,155 | $ 390,253
Total loans, net of unearned income, percentage | 1.00% | 1.00% | 1.00%
Residential real estate |  |  |
Loans [Line Items] |  |  |
Total loans, net of unearned income | $ 1,799,985 | $ 1,637,099 | $ 1,421,973
Total loans, net of unearned income, percentage | 5.00% | 5.00% | 4.00%
Premium finance receivables | Property and casualty insurance |  |  |
Loans [Line Items] |  |  |
Total loans, net of unearned income | $ 4,937,408 | $ 4,855,487 | $ 3,958,543
Total loans, net of unearned income, percentage | 14.00% | 14.00% | 12.00%
Premium finance receivables | Life insurance |  |  |
Loans [Line Items] |  |  |
Total loans, net of unearned income | $ 7,354,163 | $ 7,042,810 | $ 6,111,495
Total loans, net of unearned income, percentage | 21.00% | 20.00% | 19.00%
Consumer and other |  |  |
Loans [Line Items] |  |  |
Total loans, net of unearned income | $ 48,519 | $ 24,199 | $ 35,983
Total loans, net of unearned income, percentage | 0.00% | 0.00% | 0.00%

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