Loans - Summary of Allowance for Loan Losses and Recorded Investment in Loans (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Schedule Of Allowance For Loan Losses [Line Items]
Balance, beginning of period				$ 26,977				$ 18,122	$ 26,977	$ 18,122	$ 12,508
Charge-offs									(4,769)	(2,561)	(2,462)
Recoveries									135	381	66
Provision	2,400	2,400	2,400	2,600	4,800	1,800	1,800	2,635	9,800	11,035	8,010
Balance, end of period	32,143				26,977				32,143	26,977	18,122
Individually evaluated for impairment	3,955				6,942				3,955	6,942
Collectively evaluated for impairment	28,188				20,035				28,188	20,035
Ending balance-total	2,357,777				1,922,217				2,357,777	1,922,217
Loans receivable [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Ending balance-total	2,357,777				1,922,217				2,357,777	1,922,217
Individually evaluated for impairment	17,115				21,313				17,115	21,313
Collectively evaluated for impairment	2,340,662				1,900,904				2,340,662	1,900,904
Construction [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance, beginning of period				2,004				722	2,004	722
Charge-offs									(46)
Recoveries										16
Provision									832	1,266
Balance, end of period	2,790				2,004				2,790	2,004
Individually evaluated for impairment	42				176				42	176
Collectively evaluated for impairment	2,748				1,828				2,748	1,828
Ending balance-total	212,430				168,544				212,430	168,544
Construction [Member] | Loans receivable [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Ending balance-total	212,430				168,544				212,430	168,544
Individually evaluated for impairment	309				799				309	799
Collectively evaluated for impairment	212,121				167,745				212,121	167,745
Commercial real estate [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance, beginning of period				10,716				9,871	10,716	9,871
Charge-offs									(292)	(1,262)
Recoveries									19	132
Provision									3,337	1,975
Balance, end of period	13,780				10,716				13,780	10,716
Individually evaluated for impairment	1,639				951				1,639	951
Collectively evaluated for impairment	12,141				9,765				12,141	9,765
Ending balance-total	1,128,181				988,994				1,128,181	988,994
Commercial real estate [Member] | Loans receivable [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Ending balance-total	1,128,181				988,994				1,128,181	988,994
Individually evaluated for impairment	9,811				5,203				9,811	5,203
Collectively evaluated for impairment	1,118,370				983,791				1,118,370	983,791
Consumer real estate [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance, beginning of period				2,450				1,519	2,450	1,519
Charge-offs										(59)
Recoveries									30	22
Provision									176	968
Balance, end of period	2,656				2,450				2,656	2,450
Individually evaluated for impairment	183				362				183	362
Collectively evaluated for impairment	2,473				2,088				2,473	2,088
Ending balance-total	117,653				103,516				117,653	103,516
Consumer real estate [Member] | Loans receivable [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Ending balance-total	117,653				103,516				117,653	103,516
Individually evaluated for impairment	2,990				1,178				2,990	1,178
Collectively evaluated for impairment	114,663				102,338				114,663	102,338
Commercial and industrial [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance, beginning of period				11,675				5,928	11,675	5,928
Charge-offs									(4,229)	(1,068)
Recoveries									68	153
Provision									5,163	6,662
Balance, end of period	12,677				11,675				12,677	11,675
Individually evaluated for impairment	2,091				5,453				2,091	5,453
Collectively evaluated for impairment	10,586				6,222				10,586	6,222
Ending balance-total	883,111				647,090				883,111	647,090
Commercial and industrial [Member] | Loans receivable [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Ending balance-total	883,111				647,090				883,111	647,090
Individually evaluated for impairment	4,005				14,133				4,005	14,133
Collectively evaluated for impairment	879,106				632,957				879,106	632,957
Other consumer [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Balance, beginning of period				132				82	132	82
Charge-offs									(202)	(172)
Recoveries									18	58
Provision									292	164
Balance, end of period	240				132				240	132
Individually evaluated for impairment
Collectively evaluated for impairment	240				132				240	132
Ending balance-total	16,402				14,073				16,402	14,073
Other consumer [Member] | Loans receivable [Member]
Schedule Of Allowance For Loan Losses [Line Items]
Ending balance-total	16,402				14,073				16,402	14,073
Individually evaluated for impairment
Collectively evaluated for impairment	$ 16,402				$ 14,073				$ 16,402	$ 14,073