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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, 2019 | Dec. 31, 2018
--- | --- | ---
Financing Receivable, Past Due [Line Items] |  |
Current | $ 5,985,973 | $ 5,890,141
Past due | 55,362 | 58,878
Non - performing | 45,027 | 46,073
Total Loans | 6,041,335 | 5,949,019
Commercial real estate |  |
Financing Receivable, Past Due [Line Items] |  |
Current | 2,875,439 | 2,903,997
Past due | 31,456 | 17,835
Non - performing | 28,783 | 12,052
Total Loans | 2,906,895 | 2,921,832
Commercial and industrial |  |
Financing Receivable, Past Due [Line Items] |  |
Current | 1,554,081 | 1,482,473
Past due | 5,646 | 10,943
Non - performing | 4,130 | 8,960
Total Loans | 1,559,727 | 1,493,416
Commercial construction |  |
Financing Receivable, Past Due [Line Items] |  |
Current | 265,977 | 243,004
Past due | 1,226 | 14,193
Non - performing | 1,226 | 14,193
Total Loans | 267,203 | 257,197
Residential mortgage |  |
Financing Receivable, Past Due [Line Items] |  |
Current | 741,453 | 717,447
Past due | 9,902 | 9,232
Non - performing | 6,782 | 7,128
Total Loans | 751,355 | 726,679
Home equity |  |
Financing Receivable, Past Due [Line Items] |  |
Current | 457,296 | 465,152
Past due | 6,900 | 6,410
Non - performing | 4,081 | 3,698
Total Loans | 464,195 | 471,562
Installment and other consumer |  |
Financing Receivable, Past Due [Line Items] |  |
Current | 71,808 | 67,281
Past due | 232 | 265
Non - performing | 25 | 42
Total Loans | 72,041 | 67,546
Consumer construction |  |
Financing Receivable, Past Due [Line Items] |  |
Current | 11,784 | 8,416
Past due | 0 | 0
Non - performing | 0 | 0
Total Loans | 11,784 | 8,416
Loans Held for Sale |  |
Financing Receivable, Past Due [Line Items] |  |
Current | 8,135 | 2,371
Past due | 0 | 0
Non - performing | 0 | 0
Total Loans | 8,135 | 2,371
30 to 59 Days Past Due |  |
Financing Receivable, Past Due [Line Items] |  |
Past due | 6,643 | 8,473
30 to 59 Days Past Due | Commercial real estate |  |
Financing Receivable, Past Due [Line Items] |  |
Past due | 1,456 | 3,638
30 to 59 Days Past Due | Commercial and industrial |  |
Financing Receivable, Past Due [Line Items] |  |
Past due | 606 | 1,000
30 to 59 Days Past Due | Commercial construction |  |
Financing Receivable, Past Due [Line Items] |  |
Past due | 0 | 0
30 to 59 Days Past Due | Residential mortgage |  |
Financing Receivable, Past Due [Line Items] |  |
Past due | 1,900 | 1,584
30 to 59 Days Past Due | Home equity |  |
Financing Receivable, Past Due [Line Items] |  |
Past due | 2,555 | 2,103
30 to 59 Days Past Due | Installment and other consumer |  |
Financing Receivable, Past Due [Line Items] |  |
Past due | 126 | 148
30 to 59 Days Past Due | Consumer construction |  |
Financing Receivable, Past Due [Line Items] |  |
Past due | 0 | 0
30 to 59 Days Past Due | Loans Held for Sale |  |
Financing Receivable, Past Due [Line Items] |  |
Past due | 0 | 0
60 to 89 Days Past Due |  |
Financing Receivable, Past Due [Line Items] |  |
Past due | 3,692 | 4,332
60 to 89 Days Past Due | Commercial real estate |  |
Financing Receivable, Past Due [Line Items] |  |
Past due | 1,217 | 2,145
60 to 89 Days Past Due | Commercial and industrial |  |
Financing Receivable, Past Due [Line Items] |  |
Past due | 910 | 983
60 to 89 Days Past Due | Commercial construction |  |
Financing Receivable, Past Due [Line Items] |  |
Past due | 0 | 0
60 to 89 Days Past Due | Residential mortgage |  |
Financing Receivable, Past Due [Line Items] |  |
Past due | 1,220 | 520
60 to 89 Days Past Due | Home equity |  |
Financing Receivable, Past Due [Line Items] |  |
Past due | 264 | 609
60 to 89 Days Past Due | Installment and other consumer |  |
Financing Receivable, Past Due [Line Items] |  |
Past due | 81 | 75
60 to 89 Days Past Due | Consumer construction |  |
Financing Receivable, Past Due [Line Items] |  |
Past due | 0 | 0
60 to 89 Days Past Due | Loans Held for Sale |  |
Financing Receivable, Past Due [Line Items] |  |
Past due | $ 0 | $ 0

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