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Allowance for Loan Losses - Age Analysis of Past Due Loans Segregated by Class of Loans (Details) - USD ($) $ in Thousands | Mar. 31, 2017 | Dec. 31, 2016
--- | --- | ---
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Loans, Current | $ 5,708,067 | $ 5,563,123
Total nonaccrual loans | 45,992 | 42,635
Total past due | 53,114 | 52,089
Total Loans | 5,761,181 | 5,615,212
Commercial Real Estate |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Loans, Current | 2,605,369 | 2,479,513
Total nonaccrual loans | 8,617 | 16,172
Total past due | 9,355 | 18,963
Total Loans | 2,614,724 | 2,498,476
Commercial And Industrial |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Loans, Current | 1,397,625 | 1,391,475
Total nonaccrual loans | 21,879 | 8,071
Total past due | 24,672 | 9,560
Total Loans | 1,422,297 | 1,401,035
Commercial Construction |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Loans, Current | 451,001 | 450,410
Total nonaccrual loans | 3,758 | 4,927
Total past due | 4,210 | 5,474
Total Loans | 455,211 | 455,884
Residential Mortgage |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Loans, Current | 690,524 | 689,635
Total nonaccrual loans | 8,218 | 9,918
Total past due | 10,086 | 12,347
Total Loans | 700,610 | 701,982
Home Equity Loan |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Loans, Current | 474,824 | 476,866
Total nonaccrual loans | 3,484 | 3,439
Total past due | 4,578 | 5,418
Total Loans | 479,402 | 482,284
Installment and Other Consumer |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Loans, Current | 70,006 | 65,525
Total nonaccrual loans | 36 | 108
Total past due | 213 | 327
Total Loans | 70,219 | 65,852
Consumer Construction |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Loans, Current | 4,363 | 5,906
Total nonaccrual loans | 0 | 0
Total past due | 0 | 0
Total Loans | 4,363 | 5,906
Loans Held for Sale |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Loans, Current | 14,355 | 3,793
Total nonaccrual loans | 0 | 0
Total past due | 0 | 0
Total Loans | 14,355 | 3,793
30 to 59 Days Past Due |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total past due | 6,074 | 6,598
30 to 59 Days Past Due | Commercial Real Estate |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total past due | 664 | 2,032
30 to 59 Days Past Due | Commercial And Industrial |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total past due | 2,245 | 1,061
30 to 59 Days Past Due | Commercial Construction |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total past due | 452 | 547
30 to 59 Days Past Due | Residential Mortgage |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total past due | 1,584 | 1,312
30 to 59 Days Past Due | Home Equity Loan |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total past due | 1,007 | 1,470
30 to 59 Days Past Due | Installment and Other Consumer |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total past due | 122 | 176
30 to 59 Days Past Due | Consumer Construction |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total past due | 0 | 0
30 to 59 Days Past Due | Loans Held for Sale |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total past due | 0 | 0
60 to 89 Days Past Due |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total past due | 1,048 | 2,856
60 to 89 Days Past Due | Commercial Real Estate |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total past due | 74 | 759
60 to 89 Days Past Due | Commercial And Industrial |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total past due | 548 | 428
60 to 89 Days Past Due | Commercial Construction |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total past due | 0 | 0
60 to 89 Days Past Due | Residential Mortgage |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total past due | 284 | 1,117
60 to 89 Days Past Due | Home Equity Loan |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total past due | 87 | 509
60 to 89 Days Past Due | Installment and Other Consumer |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total past due | 55 | 43
60 to 89 Days Past Due | Consumer Construction |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total past due | 0 | 0
60 to 89 Days Past Due | Loans Held for Sale |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Total past due | $ 0 | $ 0

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