Loans, Net - Schedule of Loans by Portfolio and Segment (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 5,997,147		$ 5,193,187
Allowance for loan losses	(33,706)	$ (31,995)	(29,126)	$ (27,046)	$ (24,513)	$ (22,880)
Loans, net	5,963,441		5,164,061
Net deferred fees, costs, and premium and discount	7,300		7,100
Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	474,076		582,424
Allowance for loan losses	(1,926)			(2,299)
New Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	5,523,071		4,610,763
Allowance for loan losses	(28,510)			(19,579)
Total real estate loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	4,765,392		4,166,072
Total real estate loans | New Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	4,330,757		3,632,563
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	1,437,270		1,301,754
Allowance for loan losses	(9,745)	(9,454)	(8,450)	(9,652)	(9,296)	(8,206)
Commercial real estate | Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	(935)			(1,375)
Commercial real estate | New Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	1,209,762		998,141
Allowance for loan losses	(6,696)			(5,692)
Owner-occupied commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	590,814		545,829
Allowance for loan losses	(2,252)	(2,281)	(2,243)	(1,548)	(1,252)	(1,020)
Owner-occupied commercial real estate | Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	(340)			(54)
Owner-occupied commercial real estate | New Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	571,558		524,728
Allowance for loan losses	(1,912)			(1,494)
1-4 single family residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	2,033,060		1,666,288
Allowance for loan losses	(7,439)	(7,309)	(6,425)	(5,744)	(5,213)	(4,740)
1-4 single family residential | Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	(282)			(335)
1-4 single family residential | New Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	1,923,092		1,541,255
Allowance for loan losses	(7,099)			(5,139)
Construction, land and development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	614,249		571,849
Allowance for loan losses	(3,763)	(3,415)	(3,404)	(3,024)	(2,312)	(2,456)
Construction, land and development | Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	(37)			(56)
Construction, land and development | New Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	582,615		537,494
Allowance for loan losses	(3,378)			(2,175)
Home equity loans and lines of credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	89,999		80,352
Allowance for loan losses	(615)	(499)	(483)	(563)	(398)	(355)
Home equity loans and lines of credit | Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	(273)			(432)
Home equity loans and lines of credit | New Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	43,730		30,945
Allowance for loan losses	(342)			(131)
Total other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	1,231,755		1,027,115
Total other loans | New Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	1,192,314		978,200
Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	1,224,573		1,018,898
Allowance for loan losses	(9,465)	(8,580)	(7,665)	(6,059)	(5,705)	(5,745)
Commercial and industrial | Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	(55)			(41)
Commercial and industrial | New Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	1,187,788		972,803
Allowance for loan losses	(9,044)			(4,885)
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	7,182		8,217
Allowance for loan losses	(427)	$ (457)	(456)	(456)	$ (337)	$ (358)
Consumer | Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	(4)			(6)
Consumer | New Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	4,526		5,397
Allowance for loan losses	(39)			(63)
ASC 310-30 Loans | Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	274,724		355,740
Allowance for loan losses	(3,270)			(5,168)
ASC 310-30 Loans | Total real estate loans | Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	243,524		316,567
Allowance for loan losses	(2,520)		(2,252)
ASC 310-30 Loans | Total real estate loans | New Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0		0
Allowance for loan losses	0		0
ASC 310-30 Loans | Commercial real estate | Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	182,828		247,628
Allowance for loan losses	(2,114)		(1,898)	(2,585)
ASC 310-30 Loans | Commercial real estate | New Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0		0
Allowance for loan losses	0		0
ASC 310-30 Loans | Owner-occupied commercial real estate | Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0		0
Allowance for loan losses	0		0	0
ASC 310-30 Loans | Owner-occupied commercial real estate | New Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0		0
Allowance for loan losses	0		0
ASC 310-30 Loans | 1-4 single family residential | Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	35,400		40,922
Allowance for loan losses	(58)		(26)	(270)
ASC 310-30 Loans | 1-4 single family residential | New Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0		0
Allowance for loan losses	0		0
ASC 310-30 Loans | Construction, land and development | Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	25,296		28,017
Allowance for loan losses	(348)		(328)	(793)
ASC 310-30 Loans | Construction, land and development | New Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0		0
Allowance for loan losses	0		0
ASC 310-30 Loans | Home equity loans and lines of credit | Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0		0
Allowance for loan losses	0		0	0
ASC 310-30 Loans | Home equity loans and lines of credit | New Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0		0
Allowance for loan losses	0		0
ASC 310-30 Loans | Total other loans | Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	31,200		39,173
Allowance for loan losses	(750)		(859)
ASC 310-30 Loans | Total other loans | New Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0		0
Allowance for loan losses	0		0
ASC 310-30 Loans | Commercial and industrial | Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	28,984		36,783
Allowance for loan losses	(366)		(453)	(1,133)
ASC 310-30 Loans | Commercial and industrial | New Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0		0
Allowance for loan losses	0		0
ASC 310-30 Loans | Consumer | Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	2,216		2,390
Allowance for loan losses	(384)		(406)	$ (387)
ASC 310-30 Loans | Consumer | New Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	0		0
Allowance for loan losses	0		0
Non-ASC 310-30 Loans | Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	199,352		226,684
Non-ASC 310-30 Loans | Total real estate loans | Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	191,111		216,942
Non-ASC 310-30 Loans | Commercial real estate | Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	44,680		55,985
Non-ASC 310-30 Loans | Owner-occupied commercial real estate | Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	19,256		21,101
Non-ASC 310-30 Loans | 1-4 single family residential | Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	74,568		84,111
Non-ASC 310-30 Loans | Construction, land and development | Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	6,338		6,338
Non-ASC 310-30 Loans | Home equity loans and lines of credit | Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	46,269		49,407
Non-ASC 310-30 Loans | Total other loans | Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	8,241		9,742
Non-ASC 310-30 Loans | Commercial and industrial | Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	7,801		9,312
Non-ASC 310-30 Loans | Consumer | Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 440		$ 430