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Loans and Allowances for Credit Losses, Activity in Allowance for Credit Losses (Details) - USD ($) $ in Thousands | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2019 | Dec. 31, 2018
Allowance for loan losses [Roll Forward] |  |  |  |  |
Beginning balance | $ 207,457 | $ 230,682 | $ 246,159 |  |
Provision for loan losses | 44,205 | 9,944 | 510 |  |
Loans charged off | (50,977) | (43,583) | (25,599) |  |
Recoveries | 10,074 | 10,414 | 9,612 |  |
Ending balance | 210,759 | 207,457 | 230,682 |  |
Accrual for off-balance sheet credit losses [Roll Forward] |  |  |  |  |
Beginning balance | 1,790 | 3,734 | 11,244 |  |
Provision for off-balance sheet credit risk | (205) | (1,944) | (7,510) |  |
Ending balance | 1,585 | 1,790 | 3,734 |  |
Total provision for credit losses | 44,000 | 8,000 | (7,000) |  |
Recorded investment [Abstract] |  |  |  |  |
Collectively measured for impairment, recorded investment |  |  |  | $ 21,570,036 | $ 21,493,483
Individually measured for impairment, recorded investment |  |  |  | 180,951 | 163,247
Total |  |  |  | 21,750,987 | 21,656,730
Related allowance [Abstract] |  |  |  |  |
Collectively measured for impairment, related allowance |  |  |  | 176,150 | 180,957
Individually measured for impairment, related allowance |  |  |  | 17,414 | 8,732
Total measured for impairment, related allowance | 210,759 | 207,457 | 230,682 | 210,759 | 207,457
Commercial [Member] |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Beginning balance | 102,226 | 124,269 | 140,213 |  |
Provision for loan losses | 57,125 | 12,521 | (595) |  |
Loans charged off | (43,185) | (37,880) | (19,810) |  |
Recoveries | 2,021 | 3,316 | 4,461 |  |
Ending balance | 118,187 | 102,226 | 124,269 |  |
Accrual for off-balance sheet credit losses [Roll Forward] |  |  |  |  |
Beginning balance | 1,655 | 3,644 | 11,063 |  |
Provision for off-balance sheet credit risk | (221) | (1,989) | (7,419) |  |
Ending balance | 1,434 | 1,655 | 3,644 |  |
Total provision for credit losses | 56,904 | 10,532 | (8,014) |  |
Recorded investment [Abstract] |  |  |  |  |
Collectively measured for impairment, recorded investment |  |  |  | 13,916,234 | 13,536,237
Individually measured for impairment, recorded investment |  |  |  | 115,416 | 99,841
Total |  |  |  | 14,031,650 | 13,636,078
Related allowance [Abstract] |  |  |  |  |
Collectively measured for impairment, related allowance |  |  |  | 100,773 | 93,494
Individually measured for impairment, related allowance |  |  |  | 17,414 | 8,732
Total measured for impairment, related allowance | 118,187 | 102,226 | 140,213 | 118,187 | 102,226
Commercial Real Estate [Member] |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Beginning balance | 60,026 | 56,621 | 50,749 |  |
Provision for loan losses | (12,046) | (147) | 4,008 |  |
Loans charged off | (1,161) | 0 | (76) |  |
Recoveries | 4,986 | 3,552 | 1,940 |  |
Ending balance | 51,805 | 60,026 | 56,621 |  |
Accrual for off-balance sheet credit losses [Roll Forward] |  |  |  |  |
Beginning balance | 52 | 45 | 123 |  |
Provision for off-balance sheet credit risk | 55 | 7 | (78) |  |
Ending balance | 107 | 52 | 45 |  |
Total provision for credit losses | (11,991) | (140) | 3,930 |  |
Recorded investment [Abstract] |  |  |  |  |
Collectively measured for impairment, recorded investment |  |  |  | 4,406,157 | 4,743,192
Individually measured for impairment, recorded investment |  |  |  | 27,626 | 21,621
Total |  |  |  | 4,433,783 | 4,764,813
Related allowance [Abstract] |  |  |  |  |
Collectively measured for impairment, related allowance |  |  |  | 51,805 | 60,026
Individually measured for impairment, related allowance |  |  |  | 0 | 0
Total measured for impairment, related allowance | 60,026 | 60,026 | 56,621 | 51,805 | 60,026
Residential Mortgage [Member] |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Beginning balance | 17,964 | 18,451 | 18,224 |  |
Provision for loan losses | (3,838) | (1,156) | 116 |  |
Loans charged off | (288) | (378) | (649) |  |
Recoveries | 562 | 1,047 | 760 |  |
Ending balance | 14,400 | 17,964 | 18,451 |  |
Accrual for off-balance sheet credit losses [Roll Forward] |  |  |  |  |
Beginning balance | 52 | 43 | 50 |  |
Provision for off-balance sheet credit risk | (8) | 9 | (7) |  |
Ending balance | 44 | 52 | 43 |  |
Total provision for credit losses | (3,846) | (1,147) | 109 |  |
Recorded investment [Abstract] |  |  |  |  |
Collectively measured for impairment, recorded investment |  |  |  | 2,046,550 | 2,188,478
Individually measured for impairment, recorded investment |  |  |  | 37,622 | 41,555
Total |  |  |  | 2,084,172 | 2,230,033
Related allowance [Abstract] |  |  |  |  |
Collectively measured for impairment, related allowance |  |  |  | 14,400 | 17,964
Individually measured for impairment, related allowance |  |  |  | 0 | 0
Total measured for impairment, related allowance | 17,964 | 17,964 | 18,451 | 14,400 | 17,964
Personal [Member] |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Beginning balance | 9,473 | 9,124 | 8,773 |  |
Provision for loan losses | 3,537 | 3,175 | 2,964 |  |
Loans charged off | (6,343) | (5,325) | (5,064) |  |
Recoveries | 2,505 | 2,499 | 2,451 |  |
Ending balance | 9,172 | 9,473 | 9,124 |  |
Accrual for off-balance sheet credit losses [Roll Forward] |  |  |  |  |
Beginning balance | 31 | 2 | 8 |  |
Provision for off-balance sheet credit risk | (31) | 29 | (6) |  |
Ending balance | 0 | 31 | 2 |  |
Total provision for credit losses | 3,506 | 3,204 | 2,958 |  |
Recorded investment [Abstract] |  |  |  |  |
Collectively measured for impairment, recorded investment |  |  |  | 1,201,095 | 1,025,576
Individually measured for impairment, recorded investment |  |  |  | 287 | 230
Total |  |  |  | 1,201,382 | 1,025,806
Related allowance [Abstract] |  |  |  |  |
Collectively measured for impairment, related allowance |  |  |  | 9,172 | 9,473
Individually measured for impairment, related allowance |  |  |  | 0 | 0
Total measured for impairment, related allowance | 9,172 | 9,473 | 8,773 | 9,172 | 9,473
Specific Allowance [Member] |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Beginning balance | 189,689 |  |  |  |
Ending balance | 193,564 | 189,689 |  |  |
Recorded investment [Abstract] |  |  |  |  |
Collectively measured for impairment, recorded investment |  |  |  | 21,570,036 | 21,493,483
Individually measured for impairment, recorded investment |  |  |  | 180,951 | 163,247
Total |  |  |  | 21,750,987 | 21,656,730
Related allowance [Abstract] |  |  |  |  |
Collectively measured for impairment, related allowance |  |  |  | 176,150 | 180,957
Individually measured for impairment, related allowance |  |  |  | 17,414 | 8,732
Total measured for impairment, related allowance | 189,689 | 189,689 |  | 193,564 | 189,689
Nonspecific Allowance [Member] |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Beginning balance | 17,768 | 22,217 | 28,200 |  |
Provision for loan losses | (573) | (4,449) | (5,983) |  |
Loans charged off | 0 | 0 | 0 |  |
Recoveries | 0 | 0 | 0 |  |
Ending balance | 17,195 | 17,768 | 22,217 |  |
Accrual for off-balance sheet credit losses [Roll Forward] |  |  |  |  |
Beginning balance | 0 | 0 | 0 |  |
Provision for off-balance sheet credit risk | 0 | 0 | 0 |  |
Ending balance | 0 | 0 | 0 |  |
Total provision for credit losses | (573) | (4,449) | (5,983) |  |
Recorded investment [Abstract] |  |  |  |  |
Collectively measured for impairment, recorded investment |  |  |  | 0 | 0
Individually measured for impairment, recorded investment |  |  |  | 0 | 0
Total |  |  |  | 0 | 0
Related allowance [Abstract] |  |  |  |  |
Collectively measured for impairment, related allowance |  |  |  | 0 | 0
Individually measured for impairment, related allowance |  |  |  | 0 | 0
Total measured for impairment, related allowance | $ 17,195 | $ 22,217 | $ 22,217 | $ 17,195 | $ 17,768

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