Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash flows from operating activities:
Net income	$ 19,531	$ 20,266	$ 19,147
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for loan losses	353	645	1,927
ESOP and stock compensation expense	8,891	4,653	5,037
Depreciation	3,385	3,640	3,634
Amortization of premiums, and deferred loan costs, net of (accretion) of discounts, and deferred loan fees	1,800	1,695	1,949
Amortization of intangible assets	210	416	440
Income on bank owned life insurance	(3,767)	(3,902)	(3,607)
Gain on sale of premises and equipment and other real estate owned, net	(282)	0	(397)
Net gain on sale of loans held-for-sale	(4)	(79)	(60)
Proceeds from sale of loans held-for-sale	2,392	1,707	12,726
Origination of loans held-for-sale	(2,388)	(1,157)	(3,986)
Losses (gains) on securities transactions, net	339	(227)	(3,217)
Net impairment losses on securities recognized in earnings	0	0	434
Net purchases of trading securities	(687)	(579)	(358)
(Increase) decrease in accrued interest receivable	(248)	122	17
Decrease (increase) in other assets	3,359	(2,948)	978
Deferred taxes	(1,632)	(1,167)	(4,033)
Increase (decrease) in accrued expenses and other liabilities	1,059	2,625	(623)
Net cash provided by operating activities	32,311	25,710	30,008
Cash flows from investing activities:
Net increase in loans receivable	(246,562)	(267,912)	(253,145)
Purchase of loans	(186,876)	(186,475)	0
Redemption (purchase) of FHLB of New York stock, net	3,416	(11,703)	(4,966)
Purchases of securities available-for-sale	0	(436)	(289,562)
Principal payments and maturities on securities available-for-sale	173,923	161,650	331,536
Principal payments and maturities on securities held-to-maturity	870	442	0
Purchases of securities held-to-maturity	(7,657)	(4,066)	0
Proceeds from sale of securities available-for-sale	51,148	11,975	259,551
Purchase of bank owned life insurance	0	0	(28,464)
Proceeds from sale of premises and equipment and other real estate owned	918	418	519
Purchases and improvements of premises and equipment	(802)	(809)	(2,916)
Net cash (used in) provided by investing activities	(211,622)	(296,916)	12,553
Cash flows from financing activities:
Net increase (decrease) in deposits	432,264	127,976	(174,617)
Dividends paid	(12,184)	(12,884)	(26,859)
Net proceeds from sale of common stock	0	0	54,648
Merger of Northfield Bancorp, MHC	0	0	124
Purchase of common stock for Employee Stock Ownership Plan (ESOP)	0	0	(14,224)
Exercise of stock options	158	212	21
Purchase of treasury stock	(48,446)	(138,702)	(3,628)
Additional tax benefit on equity awards	122	390	296
Increase in advance payments by borrowers for taxes and insurance	3,070	1,351	2,953
Repayments under capital lease obligations	(179)	(272)	(289)
Proceeds from securities sold under agreements to repurchase and other borrowings	250,314	821,373	539,250
Repayments related to securities sold under agreements to repurchase and other borrowings	(470,664)	(512,768)	(487,758)
Net cash provided by (used in) by financing activities	154,455	286,676	(110,083)
Net (decrease) increase in cash and cash equivalents	(24,856)	15,470	(67,522)
Cash and cash equivalents at beginning of period	76,709	61,239	128,761
Cash and cash equivalents at end of period	51,853	76,709	61,239
Supplemental cash flow information:
Interest	19,738	15,002	17,177
Income taxes	10,800	16,696	16,196
Non-cash transactions:
Transfers of held-to-maturity securities to available-for-sale securities	0	0	2,200
Loans charged-off, net	1,875	390	2,314
Transfers of loans to other real estate owned	0	860	0
Other real estate owned write-downs	71	305	124
Transfers of loans to held-for-sale, at fair value	0	0	3,704
Deposits utilized to purchase common stock	$ 0	$ 0	$ 289,554