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Loans and Loans Held for Sale - Additional Information (Detail) $ in Thousands | 3 Months Ended | 6 Months Ended |  |
--- | --- | --- | --- | ---
Jun. 30, 2015 USD ($) SecurityLoan | Jun. 30, 2015 USD ($) SecurityLoan | Mar. 04, 2015 USD ($) | Dec. 31, 2014 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Loans and Leases Receivable, Deferred Income | $ 14,000 | $ 14,000 |  | $ 2,100
Discount on loans related to purchase accounting fair value adjustments | $ 14,700 | $ 14,700 |  |
Percentage of commercial loans in total portfolio loans | 76.00% | 76.00% |  | 75.00%
Commercial Loans | $ 3,639,300 | $ 3,639,300 |  | $ 2,892,522
Concentration Risk, Product |  | no |  |
Maximum concentration of commercial real estate and commercial construction portfolio in loans (in excess of) | 7.00% | 7.00% |  | 7.00%
Minimum period of loan payment defaults following restructure for TDRs to be in default |  | 90 days |  |
Commercial Real Estate and Commercial Construction [Member] |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Commercial Loans | $ 2,400,000 | $ 2,400,000 |  |
Combined percentage of commercial real estate and commercial construction in total commercial loans | 66.00% | 66.00% |  | 66.00%
Combined percentage of commercial real estate and commercial construction in total portfolio loans | 50.00% | 50.00% |  | 49.00%
Out Of State Exposure Of Combined Portfolio | 6.30% | 6.30% |  | 8.00%
Percentage of total loans out-of-state excluding contiguous states | 3.10% | 3.10% |  | 3.90%
Construction Loans [Member] |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Commercial Loans | $ 344,983 | $ 344,983 |  | $ 216,148
Number Of Loans Modified Not Considered To Be Troubled Debt Restructuring | SecurityLoan | 4 | 4 |  |
Loans modified not considered to be troubled debt restructuring | $ 1,300 | $ 1,300 |  |
Commercial Real Estate [Member] |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Commercial Loans | $ 2,054,935 | $ 2,054,935 |  | 1,682,236
Number Of Loans Modified Not Considered To Be Troubled Debt Restructuring | SecurityLoan | 1 | 3 |  |
Loans modified not considered to be troubled debt restructuring | $ 800 | $ 1,000 |  |
Home Equity [Member] |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Number Of Loans Modified Not Considered To Be Troubled Debt Restructuring | SecurityLoan | 2 | 2 |  |
Loans modified not considered to be troubled debt restructuring | $ 200 | $ 200 |  |
Commercial and Industrial [Member] |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Commercial Loans | $ 1,239,382 | $ 1,239,382 |  | $ 994,138
Number Of Loans Modified Not Considered To Be Troubled Debt Restructuring | SecurityLoan | 4 | 6 |  |
Loans modified not considered to be troubled debt restructuring | $ 5,500 | $ 5,700 |  |
Integrity Bancshares, Inc. [Member] |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Discount on loans related to purchase accounting fair value adjustments |  |  | $ 14,800 |
Integrity Bancshares, Inc. [Member] | Commercial Real Estate and Commercial Construction [Member] |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Commercial Loans | $ 424,000 | $ 424,000 |  |

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