Fair Value Measurement - Estimates Fair Value of Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013	Dec. 31, 2012
Financial Assets
Cash and due from banks	$ 94,488	$ 95,551	$ 78,070	$ 125,605
Securities available-for-sale	1,006,079	934,386
Securities held-to-maturity	607,695	598,520
Net loans	3,900,377	3,847,549
Loans held for sale	10,641	5,855
Accrued interest receivable	19,087	18,960
Bank owned life insurance	121,878	121,390
Financial Liabilities
Deposits	5,117,403	5,062,530
Federal Home Loan Bank borrowings	138,596	39,508
Other borrowings	94,745	150,536
Junior subordinated debt	106,156	106,137
Accrued interest payable	2,306	2,354
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Financial Assets
Cash and due from banks	94,488	95,551
Securities available-for-sale	10,558	9,962
Securities held-to-maturity
Net loans
Loans held for sale
Accrued interest receivable	19,087	18,960
Bank owned life insurance	121,878	121,390
Financial Liabilities
Deposits	3,691,573	3,551,052
Federal Home Loan Bank borrowings
Other borrowings	68,475	104,196
Junior subordinated debt
Accrued interest payable	2,306	2,354
Significant Other Observable Inputs (Level 2) [Member]
Financial Assets
Cash and due from banks
Securities available-for-sale	995,521	924,424
Securities held-to-maturity	627,805	595,581
Net loans
Loans held for sale	10,641	5,855
Accrued interest receivable
Bank owned life insurance
Financial Liabilities
Deposits	1,435,949	1,525,155
Federal Home Loan Bank borrowings	141,126	42,314
Other borrowings	28,186	48,819
Junior subordinated debt	77,075	74,038
Accrued interest payable
Significant Unobservable Inputs (Level 3) [Member]
Financial Assets
Cash and due from banks
Securities available-for-sale
Securities held-to-maturity	735	727
Net loans	3,784,772	3,754,465
Loans held for sale
Accrued interest receivable
Bank owned life insurance
Financial Liabilities
Deposits
Federal Home Loan Bank borrowings
Other borrowings
Junior subordinated debt
Accrued interest payable
Carrying Amount [Member]
Financial Assets
Cash and due from banks	94,488	95,551
Securities available-for-sale	1,006,079	934,386
Securities held-to-maturity	607,695	598,520
Net loans	3,900,377	3,847,549
Loans held for sale	10,641	5,855
Accrued interest receivable	19,087	18,960
Bank owned life insurance	121,878	121,390
Financial Liabilities
Deposits	5,117,403	5,062,530
Federal Home Loan Bank borrowings	138,596	39,508
Other borrowings	94,745	150,536
Junior subordinated debt	106,156	106,137
Accrued interest payable	2,306	2,354
Fair Value Estimate [Member]
Financial Assets
Cash and due from banks	94,488	95,551
Securities available-for-sale	1,006,079	934,386
Securities held-to-maturity	628,540	596,308
Net loans	3,784,772	3,754,465
Loans held for sale	10,641	5,855
Accrued interest receivable	19,087	18,960
Bank owned life insurance	121,878	121,390
Financial Liabilities
Deposits	5,127,522	5,076,207
Federal Home Loan Bank borrowings	141,126	42,314
Other borrowings	96,661	153,015
Junior subordinated debt	77,075	74,038
Accrued interest payable	$ 2,306	$ 2,354