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Loans and Loans Held for Sale - Additional Information (Details) $ in Thousands | 1 Months Ended | 3 Months Ended | 12 Months Ended |
--- | --- | --- | --- | ---
May 03, 2017 USD ($) contract | Mar. 31, 2017 USD ($) contract loan | Mar. 31, 2016 USD ($) loan | Dec. 31, 2015 | Dec. 31, 2016 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, net of unearned income |  | $ 5,600 |  |  | $ 5,200
Loans, net of discount related to purchase accounting adjustments |  | 6,000 |  |  | 7,100
Loans receivable, net |  | 5,761,181 |  |  | $ 5,615,212
Maximum concentration of commercial real estate and commercial construction portfolio in loans (in excess of) |  |  |  |  | 7.00%
Increase in loans held for sale during the period |  | $ 10,600 |  |  |
Threshold period of satisfactory performance for troubled debt restructuring to be restored to accruing status |  | 6 months |  |  |
Commitment to lend additional funds on troubled debt restructuring |  | $ 500 |  |  |
Minimum period of loan payment defaults following restructure for TDRs to be in default |  | 90 days |  |  |
Number of troubled debt restructuring loans that defaulted | loan |  | 0 |  |  |
Subsequent Event |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Increase in loans held for sale during the period | $ 11,300 |  |  |  |
Number of loans held-for-sale sold during period | contract | 2 |  |  |  |
Commercial |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Percentage of commercial loans in total portfolio loans |  | 78.00% |  |  |
Commercial Loans |  | $ 4,492,232 |  |  | $ 4,355,395
Maximum concentration of commercial real estate and commercial construction portfolio in loans (in excess of) |  | 7.00% |  |  | 7.00%
Commercial Real Estate |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans receivable, net |  | $ 2,614,724 |  |  | $ 2,498,476
Number of loans modified not considered to be troubled debt restructuring | contract |  | 3 |  |  |
Loans modified not considered to be troubled debt restructuring |  | $ 1,500 |  |  |
Commercial Real Estate | Commercial |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Commercial Loans |  | 2,614,724 |  |  | 2,498,476
Commercial And Industrial |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans receivable, net |  | $ 1,422,297 |  |  | 1,401,035
Number of loans modified not considered to be troubled debt restructuring | contract |  | 7 |  |  |
Loans modified not considered to be troubled debt restructuring |  | $ 6,500 |  |  |
Commercial And Industrial | Commercial |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Commercial Loans |  | 1,422,297 |  |  | 1,401,035
Commercial Construction |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans receivable, net |  | 455,211 |  |  | 455,884
Number of troubled debt restructuring loans that defaulted | loan |  |  | 1 |  |
Recorded investment of troubled debt restructuring loans that defaulted |  |  | $ 600 |  |
Commercial Construction | Commercial |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Commercial Loans |  | 455,211 |  |  | 455,884
Residential Mortgage |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans receivable, net |  | 700,610 |  |  | 701,982
Commercial Real Estate and Commercial Construction | Commercial |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Commercial Loans |  | $ 3,100,000 |  |  | $ 3,000,000
Combined percentage of commercial real estate and commercial construction in total commercial loans |  | 68.00% |  |  | 68.00%
Combined percentage of commercial real estate and commercial construction in total portfolio loans |  | 53.00% |  |  | 53.00%
Concentration risk percentage of commercial real estate and commercial construction |  | 0.00% |  | 0.00% |
Out of market exposure of combined portfolio (percent) |  | 5.20% |  |  | 5.20%
Percentage of total loans out-of-state excluding contiguous states |  | 2.80% |  |  | 2.70%
Integrity Bancshares, Inc. |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans receivable, net |  | $ 488,000 |  |  | $ 543,000
Integrity Bancshares, Inc. | Commercial Real Estate |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans receivable, net |  | 251,000 |  |  | 273,000
Integrity Bancshares, Inc. | Commercial And Industrial |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans receivable, net |  | 118,000 |  |  | 141,000
Integrity Bancshares, Inc. | Commercial Construction |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans receivable, net |  | 29,200 |  |  | 33,000
Integrity Bancshares, Inc. | Residential Mortgage |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans receivable, net |  | 68,500 |  |  | 74,000
Integrity Bancshares, Inc. | Home Equity, Installment and Other Consumer Construction |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans receivable, net |  | $ 21,300 |  |  | $ 22,000

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