Fair Value of Financial Instrument - Carrying Amount and Estimated 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	$ 80,986	$ 62,955	$ 50,343	$ 80,256
Federal funds sold and interest-bearing accounts	44,800	204,984	43,904
FDIC loss-share receivable	49,180	65,441	105,513	159,724
Financial liabilities:
Other borrowings	100,293	194,572	0
Subordinated deferrable interest debentures	64,842	55,466	42,269
Carrying Value [Member]
Financial assets:
Cash and due from banks	80,986	62,955	50,343
Federal funds sold and interest-bearing accounts	44,800	204,984	43,904
Loans, net	2,745,897	2,392,521	1,930,373
FDIC loss-share receivable	49,180	65,441	105,513
Financial liabilities:
Deposits	3,389,035	2,999,231	2,443,103
Securities sold under agreements to repurchase	51,109	83,516	19,142
Other borrowings	100,293	194,572
Subordinated deferrable interest debentures	64,842	55,466	42,269
Fair Value [Member]
Financial assets:
Cash and due from banks	80,986	62,995	50,343
Federal funds sold and interest-bearing accounts	44,800	204,984	43,904
Loans, net	2,754,953	2,404,909	1,956,198
FDIC loss-share receivable	46,242	61,317	99,558
Financial liabilities:
Deposits	3,389,880	3,000,061	2,444,263
Securities sold under agreements to repurchase	51,109	83,516	19,412
Other borrowings	100,293	194,572
Subordinated deferrable interest debentures	45,864	36,277	23,231
Fair Value [Member] | Level 1 [Member]
Financial assets:
Cash and due from banks	80,986	62,955	50,343
Federal funds sold and interest-bearing accounts	44,800	204,984	43,904
Loans, net
FDIC loss-share receivable
Financial liabilities:
Deposits
Securities sold under agreements to repurchase	51,109	83,516	19,412
Other borrowings
Subordinated deferrable interest debentures
Fair Value [Member] | Level 2 [Member]
Financial assets:
Cash and due from banks
Federal funds sold and interest-bearing accounts
Loans, net	2,754,953	2,404,909	1,956,198
FDIC loss-share receivable
Financial liabilities:
Deposits	3,389,880	3,000,061	2,444,263
Securities sold under agreements to repurchase
Other borrowings	100,293	194,572
Subordinated deferrable interest debentures	45,864	36,277	23,231
Fair Value [Member] | Level 3 [Member]
Financial assets:
Cash and due from banks
Federal funds sold and interest-bearing accounts
Loans, net
FDIC loss-share receivable	46,242	61,317	99,558
Financial liabilities:
Deposits
Securities sold under agreements to repurchase
Other borrowings
Subordinated deferrable interest debentures