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Allowance for Loan Losses - Age Analysis of Past Due Loans Segregated by Class of Loans (Details) - USD ($) $ in Thousands | Jun. 30, 2018 | Dec. 31, 2017
--- | --- | ---
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Current | $ 5,759,858 | $ 5,730,074
Non - performing | 21,372 | 23,938
Past due | 30,061 | 35,860
Total Loans | 5,789,919 | 5,765,934
Commercial real estate |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Current | 2,781,239 | 2,681,395
Non - performing | 4,617 | 3,468
Past due | 7,402 | 4,599
Total Loans | 2,788,641 | 2,685,994
Commercial and industrial |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Current | 1,450,174 | 1,426,754
Non - performing | 4,853 | 5,646
Past due | 5,404 | 6,512
Total Loans | 1,455,578 | 1,433,266
Commercial construction |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Current | 297,849 | 377,968
Non - performing | 1,870 | 3,873
Past due | 1,938 | 6,366
Total Loans | 299,787 | 384,334
Residential mortgage |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Current | 689,751 | 687,195
Non - performing | 6,112 | 7,165
Past due | 8,689 | 11,579
Total Loans | 698,440 | 698,774
Home equity |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Current | 465,261 | 480,956
Non - performing | 3,871 | 3,715
Past due | 6,361 | 6,370
Total Loans | 471,622 | 487,326
Installment and other consumer |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Current | 66,371 | 66,770
Non - performing | 49 | 71
Past due | 267 | 434
Total Loans | 66,638 | 67,204
Consumer construction |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Current | 5,412 | 4,551
Non - performing | 0 | 0
Past due | 0 | 0
Total Loans | 5,412 | 4,551
Loans Held for Sale |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Current | 3,801 | 4,485
Non - performing | 0 | 0
Past due | 0 | 0
Total Loans | 3,801 | 4,485
30 to 59 Days Past Due |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Past due | 6,496 | 9,123
30 to 59 Days Past Due | Commercial real estate |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Past due | 2,473 | 997
30 to 59 Days Past Due | Commercial and industrial |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Past due | 432 | 420
30 to 59 Days Past Due | Commercial construction |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Past due | 68 | 2,473
30 to 59 Days Past Due | Residential mortgage |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Past due | 1,445 | 2,975
30 to 59 Days Past Due | Home equity |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Past due | 1,906 | 2,065
30 to 59 Days Past Due | Installment and other consumer |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Past due | 172 | 193
30 to 59 Days Past Due | Consumer construction |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Past due | 0 | 0
30 to 59 Days Past Due | Loans Held for Sale |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Past due | 0 | 0
60 to 89 Days Past Due |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Past due | 2,193 | 2,799
60 to 89 Days Past Due | Commercial real estate |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Past due | 312 | 134
60 to 89 Days Past Due | Commercial and industrial |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Past due | 119 | 446
60 to 89 Days Past Due | Commercial construction |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Past due | 0 | 20
60 to 89 Days Past Due | Residential mortgage |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Past due | 1,132 | 1,439
60 to 89 Days Past Due | Home equity |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Past due | 584 | 590
60 to 89 Days Past Due | Installment and other consumer |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Past due | 46 | 170
60 to 89 Days Past Due | Consumer construction |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Past due | 0 | 0
60 to 89 Days Past Due | Loans Held for Sale |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
Past due | $ 0 | $ 0

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