Fair Value Measurement - Estimates Fair Value of Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012	Dec. 31, 2011
Financial Assets
Cash and due from banks	$ 78,070	$ 125,605	$ 102,815	$ 140,325
Securities available-for-sale	971,178	1,021,244
Held-to-maturity , Amortized cost	608,761	602,509
Net loans	3,751,001	3,635,063
Loans held for sale	14,517	21,903
Accrued interest receivable	19,248	19,354
Bank owned life insurance	119,546	119,671
Financial Liabilities
Deposits	4,938,755	4,944,284
Federal Home Loan Bank borrowings	60,344	111,187
Other borrowings	200,538	142,971
Junior subordinated debt	106,118	113,832
Accrued interest payable	3,516	3,856
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Financial Assets
Cash and due from banks	78,070	125,605
Securities available-for-sale	9,050	9,059
Accrued interest receivable	19,248	19,354
Bank owned life insurance	119,546	119,671
Financial Liabilities
Deposits	3,362,364	3,294,664
Other borrowings	153,750	95,768
Accrued interest payable	3,516	3,856
Significant Other Observable Inputs (Level 2) [Member]
Financial Assets
Securities available-for-sale	962,128	1,012,162
Held-to-maturity , Amortized cost	614,456	638,469
Loans held for sale	14,517	21,903
Financial Liabilities
Deposits	1,597,200	1,668,692
Federal Home Loan Bank borrowings	64,418	114,461
Other borrowings	49,926	46,985
Junior subordinated debt	63,763	64,624
Significant Unobservable Inputs (Level 3) [Member]
Financial Assets
Securities available-for-sale		23
Held-to-maturity , Amortized cost	747	804
Net loans	3,710,157	3,600,068
Carrying Amount [Member]
Financial Assets
Cash and due from banks	78,070	125,605
Securities available-for-sale	971,178	1,021,244
Held-to-maturity , Amortized cost	608,761	602,509
Net loans	3,751,001	3,635,063
Loans held for sale	14,517	21,903
Accrued interest receivable	19,248	19,354
Bank owned life insurance	119,546	119,671
Financial Liabilities
Deposits	4,938,755	4,944,284
Federal Home Loan Bank borrowings	60,344	111,187
Other borrowings	200,538	142,971
Junior subordinated debt	106,118	113,832
Accrued interest payable	3,516	3,856
Fair Value Estimate [Member]
Financial Assets
Cash and due from banks	78,070	125,605
Securities available-for-sale	971,178	1,021,244
Held-to-maturity , Amortized cost	615,203	639,273
Net loans	3,710,157	3,600,068
Loans held for sale	14,517	21,903
Accrued interest receivable	19,248	19,354
Bank owned life insurance	119,546	119,671
Financial Liabilities
Deposits	4,959,564	4,963,356
Federal Home Loan Bank borrowings	64,418	114,461
Other borrowings	203,676	142,753
Junior subordinated debt	63,763	64,624
Accrued interest payable	$ 3,516	$ 3,856