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Loans and Allowances for Credit Losses, Activity in Allowance for Credit Losses (Details) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended |  |
--- | --- | --- | --- | ---
Jun. 30, 2019 | Jun. 30, 2018 | Jun. 30, 2019 | Jun. 30, 2018 | Jun. 30, 2019 | Dec. 31, 2018
Allowance for loan losses [Roll Forward] |  |  |  |  |  |
Beginning balance | $ 205,340 | $ 223,967 | $ 207,457 | $ 230,682 |  |
Provision for loan losses | 4,918 | 1,702 | 12,887 | (3,699) |  |
Loans charged off | (13,227) | (15,105) | (25,002) | (17,995) |  |
Recoveries | 5,503 | 4,578 | 7,192 | 6,154 |  |
Ending balance | 202,534 | 215,142 | 202,534 | 215,142 |  |
Allowance for off-balance sheet credit losses [Roll Forward] |  |  |  |  |  |
Beginning balance | 1,821 | 4,135 | 1,790 | 3,734 |  |
Provision for off-balance sheet credit losses | 82 | (1,702) | 113 | (1,301) |  |
Ending balance | 1,903 | 2,433 | 1,903 | 2,433 |  |
Total provision for credit losses | 5,000 | 0 | 13,000 | (5,000) |  |
Recorded investment [Abstract] |  |  |  |  |  |
Collectively measured for impairment, recorded investment |  |  |  |  | $ 22,071,873 | $ 21,493,483
Individually measured for impairment, recorded investment |  |  |  |  | 183,779 | 163,247
Total |  |  |  |  | 22,255,652 | 21,656,730
Related allowance [Abstract] |  |  |  |  |  |
Collectively measured for impairment, related allowance |  |  |  |  | 181,659 | 180,957
Individually measured for impairment, related allowance |  |  |  |  | 4,038 | 8,732
Total | 205,340 | 223,967 | 207,457 | 230,682 | 202,534 | 207,457
Commercial [Member] |  |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |  |
Beginning balance | 103,577 | 120,083 | 102,226 | 124,269 |  |
Provision for loan losses | 13,771 | 7,116 | 24,879 | 4,005 |  |
Loans charged off | (11,385) | (13,775) | (21,853) | (15,338) |  |
Recoveries | 434 | 298 | 1,145 | 786 |  |
Ending balance | 106,397 | 113,722 | 106,397 | 113,722 |  |
Allowance for off-balance sheet credit losses [Roll Forward] |  |  |  |  |  |
Beginning balance | 1,725 | 4,027 | 1,655 | 3,644 |  |
Provision for off-balance sheet credit losses | 17 | (1,666) | 87 | (1,283) |  |
Ending balance | 1,742 | 2,361 | 1,742 | 2,361 |  |
Total provision for credit losses | 13,788 | 5,450 | 24,966 | 2,722 |  |
Recorded investment [Abstract] |  |  |  |  |  |
Collectively measured for impairment, recorded investment |  |  |  |  | 14,213,513 | 13,536,237
Individually measured for impairment, recorded investment |  |  |  |  | 123,395 | 99,841
Total |  |  |  |  | 14,336,908 | 13,636,078
Related allowance [Abstract] |  |  |  |  |  |
Collectively measured for impairment, related allowance |  |  |  |  | 102,359 | 93,494
Individually measured for impairment, related allowance |  |  |  |  | 4,038 | 8,732
Total | 103,577 | 120,083 | 106,397 | 113,722 | 106,397 | 102,226
Commercial real estate [Member] |  |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |  |
Beginning balance | 58,134 | 57,070 | 60,026 | 56,621 |  |
Provision for loan losses | (8,173) | (1,409) | (10,177) | (1,143) |  |
Loans charged off | (118) | 0 | (118) | 0 |  |
Recoveries | 4,345 | 3,097 | 4,457 | 3,280 |  |
Ending balance | 54,188 | 58,758 | 54,188 | 58,758 |  |
Allowance for off-balance sheet credit losses [Roll Forward] |  |  |  |  |  |
Beginning balance | 48 | 44 | 52 | 45 |  |
Provision for off-balance sheet credit losses | 68 | (27) | 64 | (28) |  |
Ending balance | 116 | 17 | 116 | 17 |  |
Total provision for credit losses | (8,105) | (1,436) | (10,113) | (1,171) |  |
Recorded investment [Abstract] |  |  |  |  |  |
Collectively measured for impairment, recorded investment |  |  |  |  | 4,688,363 | 4,743,192
Individually measured for impairment, recorded investment |  |  |  |  | 21,670 | 21,621
Total |  |  |  |  | 4,710,033 | 4,764,813
Related allowance [Abstract] |  |  |  |  |  |
Collectively measured for impairment, related allowance |  |  |  |  | 54,188 | 60,026
Individually measured for impairment, related allowance |  |  |  |  | 0 | 0
Total | 58,134 | 57,070 | 54,188 | 56,621 | 54,188 | 60,026
Residential mortgage [Member] |  |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |  |
Beginning balance | 15,668 | 18,431 | 17,964 | 18,451 |  |
Provision for loan losses | 1 | (257) | (2,407) | (419) |  |
Loans charged off | (94) | (135) | (136) | (235) |  |
Recoveries | 149 | 505 | 303 | 747 |  |
Ending balance | 15,724 | 18,544 | 15,724 | 18,544 |  |
Allowance for off-balance sheet credit losses [Roll Forward] |  |  |  |  |  |
Beginning balance | 47 | 62 | 52 | 43 |  |
Provision for off-balance sheet credit losses | (3) | (9) | (8) | 10 |  |
Ending balance | 44 | 53 | 44 | 53 |  |
Total provision for credit losses | (2) | (266) | (2,415) | (409) |  |
Recorded investment [Abstract] |  |  |  |  |  |
Collectively measured for impairment, recorded investment |  |  |  |  | 2,132,345 | 2,188,478
Individually measured for impairment, recorded investment |  |  |  |  | 38,477 | 41,555
Total |  |  |  |  | 2,170,822 | 2,230,033
Related allowance [Abstract] |  |  |  |  |  |
Collectively measured for impairment, related allowance |  |  |  |  | 15,724 | 17,964
Individually measured for impairment, related allowance |  |  |  |  | 0 | 0
Total | 15,668 | 18,431 | 17,964 | 18,451 | 15,724 | 17,964
Personal [Member] |  |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |  |
Beginning balance | 8,783 | 8,408 | 9,473 | 9,124 |  |
Provision for loan losses | 1,660 | 755 | 1,523 | 603 |  |
Loans charged off | (1,630) | (1,195) | (2,895) | (2,422) |  |
Recoveries | 575 | 678 | 1,287 | 1,341 |  |
Ending balance | 9,388 | 8,646 | 9,388 | 8,646 |  |
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 | 1,660 | 755 | 1,493 | 603 |  |
Recorded investment [Abstract] |  |  |  |  |  |
Collectively measured for impairment, recorded investment |  |  |  |  | 1,037,652 | 1,025,576
Individually measured for impairment, recorded investment |  |  |  |  | 237 | 230
Total |  |  |  |  | 1,037,889 | 1,025,806
Related allowance [Abstract] |  |  |  |  |  |
Collectively measured for impairment, related allowance |  |  |  |  | 9,388 | 9,473
Individually measured for impairment, related allowance |  |  |  |  | 0 | 0
Total | 8,783 | 8,408 | 9,388 | 9,124 | 9,388 | 9,473
Specific Allowance [Member] |  |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |  |
Beginning balance |  |  | 189,689 |  |  |
Ending balance | 185,697 |  | 185,697 |  |  |
Recorded investment [Abstract] |  |  |  |  |  |
Collectively measured for impairment, recorded investment |  |  |  |  | 22,071,873 | 21,493,483
Individually measured for impairment, recorded investment |  |  |  |  | 183,779 | 163,247
Total |  |  |  |  | 22,255,652 | 21,656,730
Related allowance [Abstract] |  |  |  |  |  |
Collectively measured for impairment, related allowance |  |  |  |  | 181,659 | 180,957
Individually measured for impairment, related allowance |  |  |  |  | 4,038 | 8,732
Total | 185,697 |  | 189,689 |  | 185,697 | 189,689
Nonspecific Allowance [Member] |  |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |  |
Beginning balance | 19,178 | 19,975 | 17,768 | 22,217 |  |
Provision for loan losses | (2,341) | (4,503) | (931) | (6,745) |  |
Loans charged off | 0 | 0 | 0 | 0 |  |
Recoveries | 0 | 0 | 0 | 0 |  |
Ending balance | 16,837 | 15,472 | 16,837 | 15,472 |  |
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 | (2,341) | (4,503) | (931) | (6,745) |  |
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 | $ 19,178 | $ 19,975 | $ 16,837 | $ 15,472 | $ 16,837 | $ 17,768

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