Acquisition of Clifton Bancorp Inc. - Summary of Unaudited Supplemental Pro Forma Information (Detail) - Clifton Bancorp Inc. [Member] - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Mar. 31, 2018	Mar. 31, 2018
Business Acquisition Pro Forma Information Nonrecurring Adjustment [Line Items]
Net interest income	$ 39,237	$ 116,817
Non-interest income	3,986	11,878
Non-interest expense	27,902	81,811
Net income available to common stockholders	$ 10,745	$ 25,581

The pro forma net Income or Loss for the period as if the business combination or combinations had been completed at the beginning of a period.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(3)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(2)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration