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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
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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

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