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Loans and Allowances for Credit Losses, Activity in Allowance for Credit Losses (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended |  |
--- | --- | --- | --- | ---
Sep. 30, 2019 | Sep. 30, 2018 | Sep. 30, 2019 | Sep. 30, 2018 | Sep. 30, 2019 | Dec. 31, 2018
Allowance for loan losses [Roll Forward] |  |  |  |  |  |
Beginning balance | $ 202,534 | $ 215,142 | $ 207,457 | $ 230,682 |  |
Provision for loan losses | 12,539 | 4,408 | 25,426 | 709 |  |
Loans charged off | (11,707) | (11,073) | (36,709) | (29,068) |  |
Recoveries | 1,066 | 2,092 | 8,258 | 8,246 |  |
Ending balance | 204,432 | 210,569 | 204,432 | 210,569 |  |
Allowance for off-balance sheet credit losses [Roll Forward] |  |  |  |  |  |
Beginning balance | 1,903 | 2,433 | 1,790 | 3,734 |  |
Provision for off-balance sheet credit losses | (539) | (408) | (426) | (1,709) |  |
Ending balance | 1,364 | 2,025 | 1,364 | 2,025 |  |
Total provision for credit losses | 12,000 | 4,000 | 25,000 | (1,000) |  |
Recorded investment [Abstract] |  |  |  |  |  |
Collectively measured for impairment, recorded investment |  |  |  |  | $ 22,112,901 | $ 21,493,483
Individually measured for impairment, recorded investment |  |  |  |  | 172,466 | 163,247
Total |  |  |  |  | 22,285,367 | 21,656,730
Related allowance [Abstract] |  |  |  |  |  |
Collectively measured for impairment, related allowance |  |  |  |  | 179,144 | 180,957
Individually measured for impairment, related allowance |  |  |  |  | 7,533 | 8,732
Total | 204,432 | 215,142 | 204,432 | 210,569 | 204,432 | 207,457
Commercial [Member] |  |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |  |
Beginning balance | 106,397 | 113,722 | 102,226 | 124,269 |  |
Provision for loan losses | 9,861 | (1,285) | 34,740 | 2,720 |  |
Loans charged off | (9,875) | (9,602) | (31,728) | (24,940) |  |
Recoveries | 260 | 1,263 | 1,405 | 2,049 |  |
Ending balance | 106,643 | 104,098 | 106,643 | 104,098 |  |
Allowance for off-balance sheet credit losses [Roll Forward] |  |  |  |  |  |
Beginning balance | 1,742 | 2,361 | 1,655 | 3,644 |  |
Provision for off-balance sheet credit losses | (536) | (424) | (449) | (1,707) |  |
Ending balance | 1,206 | 1,937 | 1,206 | 1,937 |  |
Total provision for credit losses | 9,325 | (1,709) | 34,291 | 1,013 |  |
Recorded investment [Abstract] |  |  |  |  |  |
Collectively measured for impairment, recorded investment |  |  |  |  | 14,312,919 | 13,536,237
Individually measured for impairment, recorded investment |  |  |  |  | 111,706 | 99,841
Total |  |  |  |  | 14,424,625 | 13,636,078
Related allowance [Abstract] |  |  |  |  |  |
Collectively measured for impairment, related allowance |  |  |  |  | 99,110 | 93,494
Individually measured for impairment, related allowance |  |  |  |  | 7,533 | 8,732
Total | 106,397 | 113,722 | 102,226 | 104,098 | 106,643 | 102,226
Commercial real estate [Member] |  |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |  |
Beginning balance | 54,188 | 58,758 | 60,026 | 56,621 |  |
Provision for loan losses | 102 | 1,391 | (10,075) | 248 |  |
Loans charged off | 0 | 0 | (118) | 0 |  |
Recoveries | 60 | 40 | 4,517 | 3,320 |  |
Ending balance | 54,350 | 60,189 | 54,350 | 60,189 |  |
Allowance for off-balance sheet credit losses [Roll Forward] |  |  |  |  |  |
Beginning balance | 116 | 17 | 52 | 45 |  |
Provision for off-balance sheet credit losses | (3) | 19 | 61 | (9) |  |
Ending balance | 113 | 36 | 113 | 36 |  |
Total provision for credit losses | 99 | 1,410 | (10,014) | 239 |  |
Recorded investment [Abstract] |  |  |  |  |  |
Collectively measured for impairment, recorded investment |  |  |  |  | 4,602,872 | 4,743,192
Individually measured for impairment, recorded investment |  |  |  |  | 23,185 | 21,621
Total |  |  |  |  | 4,626,057 | 4,764,813
Related allowance [Abstract] |  |  |  |  |  |
Collectively measured for impairment, related allowance |  |  |  |  | 54,350 | 60,026
Individually measured for impairment, related allowance |  |  |  |  | 0 | 0
Total | 54,188 | 58,758 | 60,026 | 56,621 | 54,350 | 60,026
Residential mortgage [Member] |  |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |  |
Beginning balance | 15,724 | 18,544 | 17,964 | 18,451 |  |
Provision for loan losses | (253) | 1 | (2,660) | (418) |  |
Loans charged off | (56) | (91) | (192) | (326) |  |
Recoveries | 119 | 229 | 422 | 976 |  |
Ending balance | 15,534 | 18,683 | 15,534 | 18,683 |  |
Allowance for off-balance sheet credit losses [Roll Forward] |  |  |  |  |  |
Beginning balance | 44 | 53 | 52 | 43 |  |
Provision for off-balance sheet credit losses | 0 | (3) | (8) | 7 |  |
Ending balance | 44 | 50 | 44 | 50 |  |
Total provision for credit losses | (253) | (2) | (2,668) | (411) |  |
Recorded investment [Abstract] |  |  |  |  |  |
Collectively measured for impairment, recorded investment |  |  |  |  | 2,079,999 | 2,188,478
Individually measured for impairment, recorded investment |  |  |  |  | 37,304 | 41,555
Total |  |  |  |  | 2,117,303 | 2,230,033
Related allowance [Abstract] |  |  |  |  |  |
Collectively measured for impairment, related allowance |  |  |  |  | 15,534 | 17,964
Individually measured for impairment, related allowance |  |  |  |  | 0 | 0
Total | 15,724 | 18,544 | 15,534 | 18,451 | 15,534 | 17,964
Personal [Member] |  |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |  |
Beginning balance | 9,388 | 8,646 | 9,473 | 9,124 |  |
Provision for loan losses | 1,911 | 883 | 3,434 | 1,486 |  |
Loans charged off | (1,776) | (1,380) | (4,671) | (3,802) |  |
Recoveries | 627 | 560 | 1,914 | 1,901 |  |
Ending balance | 10,150 | 8,709 | 10,150 | 8,709 |  |
Allowance for off-balance sheet credit losses [Roll Forward] |  |  |  |  |  |
Beginning balance | 1 | 2 | 31 | 2 |  |
Provision for off-balance sheet credit losses | 0 | 0 | (30) | 0 |  |
Ending balance | 1 | 2 | 1 | 2 |  |
Total provision for credit losses | 1,911 | 883 | 3,404 | 1,486 |  |
Recorded investment [Abstract] |  |  |  |  |  |
Collectively measured for impairment, recorded investment |  |  |  |  | 1,117,111 | 1,025,576
Individually measured for impairment, recorded investment |  |  |  |  | 271 | 230
Total |  |  |  |  | 1,117,382 | 1,025,806
Related allowance [Abstract] |  |  |  |  |  |
Collectively measured for impairment, related allowance |  |  |  |  | 10,150 | 9,473
Individually measured for impairment, related allowance |  |  |  |  | 0 | 0
Total | 9,388 | 8,646 | 10,150 | 9,124 | 10,150 | 9,473
Specific Allowance [Member] |  |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |  |
Beginning balance |  |  | 189,689 |  |  |
Ending balance | 186,677 |  | 186,677 |  |  |
Recorded investment [Abstract] |  |  |  |  |  |
Collectively measured for impairment, recorded investment |  |  |  |  | 22,112,901 | 21,493,483
Individually measured for impairment, recorded investment |  |  |  |  | 172,466 | 163,247
Total |  |  |  |  | 22,285,367 | 21,656,730
Related allowance [Abstract] |  |  |  |  |  |
Collectively measured for impairment, related allowance |  |  |  |  | 179,144 | 180,957
Individually measured for impairment, related allowance |  |  |  |  | 7,533 | 8,732
Total | 186,677 |  | 186,677 |  | 186,677 | 189,689
Nonspecific Allowance [Member] |  |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |  |
Beginning balance | 16,837 | 15,472 | 17,768 | 22,217 |  |
Provision for loan losses | 918 | 3,418 | (13) | (3,327) |  |
Loans charged off | 0 | 0 | 0 | 0 |  |
Recoveries | 0 | 0 | 0 | 0 |  |
Ending balance | 17,755 | 18,890 | 17,755 | 18,890 |  |
Allowance for off-balance sheet credit losses [Roll Forward] |  |  |  |  |  |
Beginning balance | 0 | 0 | 0 | 0 |  |
Provision for off-balance sheet credit losses | 0 | 0 | 0 | 0 |  |
Ending balance | 0 | 0 | 0 | 0 |  |
Total provision for credit losses | 918 | 3,418 | (13) | (3,327) |  |
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 | $ 16,837 | $ 15,472 | $ 17,755 | $ 22,217 | $ 17,755 | $ 17,768

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