Acquisitions - Additional Information (Detail) $ / shares in Units, $ in Thousands			12 Months Ended
	Jan. 04, 2019 USD ($) Branch $ / shares shares	Jan. 07, 2016 USD ($) Branch $ / shares shares	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Business Acquisition, Contingent Consideration [Line Items]
Assets			$ 5,806,093	$ 5,405,639
Loans and leases, net of deferred fees			4,456,733	4,152,720
Deposits			4,620,670	4,368,748
Total stockholders’ equity			623,739	583,122	$ 550,044	$ 400,516
Merger and acquisition integration-related expenses			$ 464	$ 0	$ 4,103
Pascack Bancorp, Inc.
Business Acquisition, Contingent Consideration [Line Items]
Consideration paid through common stock | shares		3,314,284
Consideration price per share (usd per share) | $ / shares		$ 11.35
Average strike price (usd per share) | $ / shares		$ 7.37
Cash paid in connection with cancellation of the old stock options		$ 122
Pascack Bancorp, Inc. | New Jersey
Business Acquisition, Contingent Consideration [Line Items]
Number of bank branches operated | Branch		8
Subsequent Event [Member] | Highlands Bancorp, Inc.
Business Acquisition, Contingent Consideration [Line Items]
Assets	$ 480,800
Loans and leases, net of deferred fees	438,300
Deposits	408,800
Total stockholders’ equity	$ 31,200
Subsequent Event [Member] | Highlands Bancorp, Inc.
Business Acquisition, Contingent Consideration [Line Items]
Consideration paid through common stock | shares	2,837,524
Consideration price per share (usd per share) | $ / shares	$ 14.71
Average strike price (usd per share) | $ / shares	$ 8.09
Cash paid in connection with cancellation of the old stock options	$ 797
Subsequent Event [Member] | Highlands Bancorp, Inc. | New Jersey
Business Acquisition, Contingent Consideration [Line Items]
Number of bank branches operated | Branch	4
Conversion ratio	1.015