Goodwill and Other Intangible Assets - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jul. 01, 2016	Jan. 07, 2016	May 31, 2013
Goodwill And Intangible Assets [Line Items]
Goodwill	$ 136,433	$ 136,433
Core deposit intangible	1,800	2,400
Amortization of core deposit intangible	$ 594	$ 654	$ 734
Harmony Bank
Goodwill And Intangible Assets [Line Items]
Core deposit intangible				$ 691
Pascack Bancorp, Inc.
Goodwill And Intangible Assets [Line Items]
Core deposit intangible					$ 1,500
Somerset Hills Acquisition
Goodwill And Intangible Assets [Line Items]
Core deposit intangible						$ 2,700