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Summary of Significant Accounting Policies - Additional Information (Detail) $ in Thousands | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2015 USD ($) segment entity subsidiary | Mar. 04, 2015 USD ($) | Dec. 31, 2014 USD ($)
Summary Of Significant Accounting Policies [Line Items] |  |  |
Number of subsidiary | subsidiary | 3 |  |
Percentage of outstanding common stock of investees accounted for using equity method of accounting | 100.00% |  |
Number of entities non-banking activities | entity | 5 |  |
Assets | $ 6,318,354 |  | $ 4,964,686
Period for satisfactory payment of TDRs | 6 months |  |
Evaluation for impairment of substandard and nonaccrual commercial loans | $ 500 |  |
Number of reporting units | segment | 3 |  |
Goodwill | $ 291,764 |  | 175,820
Amortization period of intangible assets | 10 years |  |
Percentage of amount recognized of tax benefit | 50.00% |  |
Community Banking |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |
Assets | $ 6,305,046 |  | 4,954,728
Goodwill | $ 287,600 |  |
Percentage of goodwill to reporting units | 99.00% |  |
Insurance |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |
Assets | $ 9,619 |  | $ 7,468
Goodwill | $ 4,200 |  |
Percentage of goodwill to reporting units | 1.00% |  |
Interest Rate Lock Commitments |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |
Period for interest rate lock commitment | 60 days |  |
Integrity Bancshares, Inc. |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |
Goodwill | $ 115,944 | $ 115,900 |
Common Wealth Trust Life Insurance Company |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |
Percentage of outstanding common stock of investees accounted for using equity method of accounting | 50.00% |  |
Minimum |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |
Percentage of outstanding common stock of investees accounted for using equity method of accounting | 20.00% |  |
Maximum |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |
Percentage of outstanding common stock of investees accounted for using equity method of accounting | 50.00% |  |
Core Deposits And Customers Lists | Minimum |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |
Acquired finite-lived intangibles, weighted average life | 10 years |  |
Core Deposits And Customers Lists | Maximum |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |
Acquired finite-lived intangibles, weighted average life | 20 years |  |
Corporate Joint Venture [Member] |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |
Percentage of outstanding common stock of investees accounted for using equity method of accounting | 50.00% |  |

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