Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands				12 Months Ended
	Dec. 14, 2016	Jul. 01, 2016	Jan. 07, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Class of Stock [Line Items]
Common stock, net proceeds				$ 0	$ 48,678	$ 22
Harmony Bank
Class of Stock [Line Items]
Consideration paid through common stock		3,201,109
Consideration price per share (usd per share)		$ 14.31
Average strike price (usd per share)		$ 9.07
Cash paid in connection with cancellation of the old stock options		$ 869
Pascack Bancorp, Inc.
Class of Stock [Line Items]
Consideration paid through common stock			3,314,284
Consideration price per share (usd per share)			$ 11.35
Average strike price (usd per share)			$ 7.37
Cash paid in connection with cancellation of the old stock options			$ 122
Cash paid for acquisition			$ 4,500
At-the-market Common Stock Issuance
Class of Stock [Line Items]
Common stock sold	2,739,650
Common stock, weighted average price (usd per share)	$ 18.25
Common stock, gross proceeds	$ 50,000
Common stock, net proceeds	$ 48,700