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Loans and Allowance for Credit Losses, Loans by Portfolio Type (Details) - USD ($) $ in Thousands | Jun. 30, 2019 | Dec. 31, 2018
--- | --- | ---
Loan receivables disclosure [Abstract] |  |  |
Loans, fixed rate of interest |  | $ 6,206,884 | $ 5,749,373
Loans, variable rate of interest |  | 15,864,989 | 15,744,110
Loans, non-accrual |  | 183,779 | 163,247
Total |  | 22,255,652 | 21,656,730
Accruing loans past due (90 days) | [1] | 2,698 | 1,338
Credit Commitments [Abstract] |  |  |
Outstanding commitments to extend credit |  | 11,000,000 |
Outstanding standby letters of credit |  | 699,000 |
Commercial [Member] |  |  |
Loan receivables disclosure [Abstract] |  |  |
Loans, fixed rate of interest |  | 3,264,990 | 2,251,188
Loans, variable rate of interest |  | 10,948,523 | 11,285,049
Loans, non-accrual |  | 123,395 | 99,841
Total |  | 14,336,908 | 13,636,078
Commercial real estate [Member] |  |  |
Loan receivables disclosure [Abstract] |  |  |
Loans, fixed rate of interest |  | 1,008,236 | 1,477,274
Loans, variable rate of interest |  | 3,680,127 | 3,265,918
Loans, non-accrual |  | 21,670 | 21,621
Total |  | 4,710,033 | 4,764,813
Residential mortgage [Member] |  |  |
Loan receivables disclosure [Abstract] |  |  |
Loans, fixed rate of interest |  | 1,751,803 | 1,830,224
Loans, variable rate of interest |  | 380,542 | 358,254
Loans, non-accrual |  | 38,477 | 41,555
Total |  | 2,170,822 | 2,230,033
Personal [Member] |  |  |
Loan receivables disclosure [Abstract] |  |  |
Loans, fixed rate of interest |  | 181,855 | 190,687
Loans, variable rate of interest |  | 855,797 | 834,889
Loans, non-accrual |  | 237 | 230
Total |  | $ 1,037,889 | $ 1,025,806
[1] | Excludes residential mortgage loans guaranteed by agencies of the U.S. government

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