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Loans and Loans Held for Sale - Summary of Restructured Loans (Details) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2019 | Mar. 31, 2018 | Dec. 31, 2018
Financing Receivable, Modifications [Line Items] |  |  |  |
Restructured loans | [1] | $ 5,499 | $ 6,770 |
Commercial and industrial |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |
Restructured loans | [1] | 5,201 | 6,041 |
Commercial construction |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |
Restructured loans | [1] | 0 | 157 |
Residential mortgage |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |
Restructured loans | [1] | 49 | 0 |
Home equity |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |
Restructured loans | [1] | 249 | 555 |
Installment and other consumer |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |
Restructured loans | [1] | 0 | $ 17 |
Performing TDRs |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |
Restructured loans |  | 23,002 |  | $ 16,786
Performing TDRs | Commercial real estate |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |
Restructured loans |  | 2,019 |  | 2,054
Performing TDRs | Commercial and industrial |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |
Restructured loans |  | 13,447 |  | 7,026
Performing TDRs | Commercial construction |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |
Restructured loans |  | 1,913 |  | 1,912
Performing TDRs | Residential mortgage |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |
Restructured loans |  | 2,025 |  | 2,214
Performing TDRs | Home equity |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |
Restructured loans |  | 3,590 |  | 3,568
Performing TDRs | Installment and other consumer |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |
Restructured loans |  | 8 |  | 12
Nonperforming TDRs |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |
Restructured loans |  | 7,873 |  | 11,088
Nonperforming TDRs | Commercial real estate |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |
Restructured loans |  | 1,074 |  | 1,139
Nonperforming TDRs | Commercial and industrial |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |
Restructured loans |  | 3,463 |  | 6,646
Nonperforming TDRs | Commercial construction |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |
Restructured loans |  | 406 |  | 406
Nonperforming TDRs | Residential mortgage |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |
Restructured loans |  | 1,520 |  | 1,543
Nonperforming TDRs | Home equity |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |
Restructured loans |  | 1,406 |  | 1,349
Nonperforming TDRs | Installment and other consumer |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |
Restructured loans |  | 4 |  | 5
Total TDRs |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |
Restructured loans |  | 30,875 |  | 27,874
Total TDRs | Commercial real estate |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |
Restructured loans |  | 3,093 |  | 3,193
Total TDRs | Commercial and industrial |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |
Restructured loans |  | 16,910 |  | 13,672
Total TDRs | Commercial construction |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |
Restructured loans |  | 2,319 |  | 2,318
Total TDRs | Residential mortgage |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |
Restructured loans |  | 3,545 |  | 3,757
Total TDRs | Home equity |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |
Restructured loans |  | 4,996 |  | 4,917
Total TDRs | Installment and other consumer |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |
Restructured loans |  | $ 12 |  | $ 17
[1] | Excludes loans that were fully paid off or fully charged-off by period end. The pre-modification balance represents the balance outstanding prior to modification. The post-modification balance represents the outstanding balance at period end.

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- Definition Post-modification amount of investment in financing receivables modified by troubled debt restructurings. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 33 -URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953676-111524 + Details
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