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Loans and Loans Held for Sale - Additional Information (Details) | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | ---
Sep. 30, 2017 USD ($) contract tdr loan | Sep. 30, 2016 USD ($) contract tdr loan | Sep. 30, 2017 USD ($) contract tdr loan | Sep. 30, 2016 USD ($) contract tdr loan | Dec. 31, 2016 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, net of unearned income | $ 3,600,000 |  | $ 3,600,000 |  | $ 5,200,000
Loans, net of discount related to purchase accounting adjustments | 4,600,000 |  | 4,600,000 |  | 7,100,000
Loans receivable, net | $ 5,868,694,000 |  | 5,868,694,000 |  | $ 5,615,212,000
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 |  |  | $ 44,100,000 |  |
Threshold period of satisfactory performance for troubled debt restructuring to be restored to accruing status |  |  | 6 months |  |
Number of troubled debt restructuring loans returned back to accruing status | tdr | 0 | 0 | 1 | 0 |
Amount of troubled debt restructuring loans returned to accruing status |  |  | $ 2,000,000 |  |
Number of loans modified not considered to be troubled debt restructuring | contract |  |  | 13 |  |
Loans modified not considered to be troubled debt restructuring |  |  | $ 11,800,000 |  |
Commitment to lend additional funds on troubled debt restructuring | $ 0 |  | $ 0 |  |
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 | 0 | 0 | 0 |
Disposal Group, Held-for-sale, Not Discontinued Operations | State College Retail Branch |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Increase in loans held for sale during the period |  |  | $ 43,400,000 |  |
Integrity Bancshares, Inc. |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans receivable, net | $ 415,000,000 |  | $ 415,000,000 |  | $ 543,000,000
Commercial |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Percentage of commercial loans in total portfolio loans | 78.00% |  | 78.00% |  | 78.00%
Commercial loans | $ 4,561,391,000 |  | $ 4,561,391,000 |  | $ 4,355,395,000
Commercial Real Estate |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans receivable, net | $ 2,681,693,000 |  | $ 2,681,693,000 |  | 2,498,476,000
Number of loans modified not considered to be troubled debt restructuring | contract | 1 | 1 | 4 | 2 |
Loans modified not considered to be troubled debt restructuring | $ 1,000,000 | $ 1,900,000 | $ 1,500,000 | $ 2,500,000 |
Commercial Real Estate | Integrity Bancshares, Inc. |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans receivable, net | 219,000,000 |  | 219,000,000 |  | 273,000,000
Commercial Real Estate | Commercial |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Commercial loans | 2,681,693,000 |  | 2,681,693,000 |  | 2,498,476,000
Commercial and Industrial |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans receivable, net | 1,446,811,000 |  | $ 1,446,811,000 |  | 1,401,035,000
Number of loans modified not considered to be troubled debt restructuring | contract |  | 12 | 9 | 15 |
Loans modified not considered to be troubled debt restructuring |  | $ 16,900,000 | $ 10,300,000 | $ 25,600,000 |
Commercial and Industrial | Integrity Bancshares, Inc. |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans receivable, net | 103,000,000 |  | 103,000,000 |  | 141,000,000
Commercial and Industrial | Commercial |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Commercial loans | 1,446,811,000 |  | 1,446,811,000 |  | 1,401,035,000
Commercial Construction |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans receivable, net | 432,887,000 |  | 432,887,000 |  | 455,884,000
Commercial Construction | Integrity Bancshares, Inc. |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans receivable, net | 15,000,000 |  | 15,000,000 |  | 33,000,000
Commercial Construction | Commercial |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Commercial loans | 432,887,000 |  | 432,887,000 |  | 455,884,000
Residential Mortgage |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans receivable, net | 697,367,000 |  | 697,367,000 |  | 701,982,000
Residential Mortgage | Integrity Bancshares, Inc. |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans receivable, net | 60,000,000 |  | 60,000,000 |  | 74,000,000
Home Equity, Installment and Other Consumer Construction | Integrity Bancshares, Inc. |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans receivable, net | 18,000,000 |  | 18,000,000 |  | 22,000,000
Commercial Real Estate and Commercial Construction | Commercial |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Commercial loans | $ 3,100,000,000 |  | $ 3,100,000,000 |  | $ 3,000,000,000
Combined percentage of commercial real estate and commercial construction in total commercial loans | 68.00% |  | 68.00% |  | 68.00%
Combined percentage of commercial real estate and commercial construction in total portfolio loans | 54.00% |  | 54.00% |  | 53.00%
Concentration risk percentage of commercial real estate and commercial construction |  |  | 0.00% |  | 0.00%
Maximum concentration of commercial real estate and commercial construction portfolio in loans (in excess of) | 14.00% |  | 14.00% |  | 14.00%
Out of market exposure of combined portfolio (percent) | 5.10% |  | 5.10% |  | 5.20%
Percentage of total loans out-of-state excluding contiguous states | 2.70% |  | 2.70% |  | 2.70%

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