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Allowance for Loan Losses - Additional Information (Details) - USD ($) $ in Thousands | 6 Months Ended |
--- | --- | ---
Jun. 30, 2019 | Dec. 31, 2018
Financing Receivable, Allowance for Credit Loss [Line Items] |  |
Loans | $ 6,041,335 | $ 5,949,019
Loans considered nonperforming (in days) | 90 days |
Threshold for evaluation for impairment of substandard and nonaccrual commercial loans | $ 500 |
Commercial | Substandard |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |
Increase (decrease) in loans | (43,300) |
Loans | 137,900 | 181,200
Commercial | Special Mention |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |
Increase (decrease) in loans | 18,400 |
Loans | $ 105,700 | $ 87,300

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