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Loans and Allowance for Credit Losses, Loans by Portfolio Type (Details) - USD ($) $ in Thousands | Sep. 30, 2019 | Dec. 31, 2018
--- | --- | ---
Loan receivables disclosure [Abstract] |  |  |
Loans, fixed rate of interest |  | $ 6,136,400 | $ 5,749,373
Loans, variable rate of interest |  | 15,976,501 | 15,744,110
Loans, non-accrual |  | 172,466 | 163,247
Total |  | 22,285,367 | 21,656,730
Accruing loans past due (90 days) | [1] | 1,541 | 1,338
Credit Commitments [Abstract] |  |  |
Outstanding commitments to extend credit |  | 11,000,000 |
Outstanding standby letters of credit |  | 713,000 |
Commercial [Member] |  |  |
Loan receivables disclosure [Abstract] |  |  |
Loans, fixed rate of interest |  | 3,184,237 | 2,251,188
Loans, variable rate of interest |  | 11,128,682 | 11,285,049
Loans, non-accrual |  | 111,706 | 99,841
Total |  | 14,424,625 | 13,636,078
Commercial real estate [Member] |  |  |
Loan receivables disclosure [Abstract] |  |  |
Loans, fixed rate of interest |  | 1,070,050 | 1,477,274
Loans, variable rate of interest |  | 3,532,822 | 3,265,918
Loans, non-accrual |  | 23,185 | 21,621
Total |  | 4,626,057 | 4,764,813
Residential mortgage [Member] |  |  |
Loan receivables disclosure [Abstract] |  |  |
Loans, fixed rate of interest |  | 1,690,286 | 1,830,224
Loans, variable rate of interest |  | 389,713 | 358,254
Loans, non-accrual |  | 37,304 | 41,555
Total |  | 2,117,303 | 2,230,033
Personal [Member] |  |  |
Loan receivables disclosure [Abstract] |  |  |
Loans, fixed rate of interest |  | 191,827 | 190,687
Loans, variable rate of interest |  | 925,284 | 834,889
Loans, non-accrual |  | 271 | 230
Total |  | $ 1,117,382 | $ 1,025,806
[1] | Excludes residential mortgage loans guaranteed by agencies of the U.S. government

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