Goodwill and Intangible Assets - Additional Information (Detail) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($) Segment	Jun. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)
Goodwill And Intangible Assets [Line Items]
Goodwill	$ 109,974		$ 109,974		$ 109,974
Number of reportable unit | Segment			1
Amortization of core deposit intangible	107	$ 119	$ 218	$ 242
Somerset Hills Acquisition [Member]
Goodwill And Intangible Assets [Line Items]
Goodwill	22,900		22,900		22,900
Core deposit intangible	2,700		2,700
Prior Acquisitions [Member]
Goodwill And Intangible Assets [Line Items]
Goodwill	$ 87,100		$ 87,100		$ 87,100