INCOME TAXES (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current Income Tax Expense (Benefit) [Abstract]
Federal										$ 20,818	$ 42,834	$ 21,127
State and City										5,523	17,026	3,235
Current Income Tax Expense (Benefit), Total										26,341	59,860	24,362
Deferred Income Tax Expense (Benefit) [Abstract]
Federal										8,334	702	2,269
State and City										2,181	395	4,614
Deferred Income Tax Expense (Benefit), Total										10,515	1,097	6,883
Federal, Total										29,152	43,536	23,396
State and City, Total										7,704	17,421	7,849
Income Tax Expense (Benefit), Total	$ 15,442	$ 7,230	$ 7,295	$ 6,889	$ 8,816	$ 7,481	$ 8,173	$ 36,487		36,856	60,957	31,245
Income Tax Reconciliation [Abstract]
Tax at Federal statutory rate										31,058	46,715	26,606
State and local taxes, net of federal income tax benefit										5,008	11,323	5,102
ESOP acceleration expense										0	3,962	0
Benefit plan differences										(535)	(54)	(59)
Adjustments for prior period returns and tax items										84	(13)	590
Investment in BOLI										(776)	(957)	(842)
Enactment of federal tax reform										3,135	0	0
Equity based compensation										(1,283)	0	0
Other, net										165	(19)	(152)
Income Tax Expense (Benefit), Total	15,442	$ 7,230	$ 7,295	$ 6,889	8,816	$ 7,481	$ 8,173	$ 36,487		$ 36,856	$ 60,957	$ 31,245
Effective tax rate										41.53%	45.67%	41.10%
Deferred tax assets [Abstract]
Allowance for loan losses	6,836				9,203					$ 6,836	$ 9,203
Employee benefit plans	7,148				15,630					7,148	15,630
Tax effect of purchase accounting fair value adjustments	307				453					307	453
Other	2,135				1,756					2,135	1,756
Total deferred tax assets	16,426				27,042					16,426	27,042
Deferred tax liabilities [Abstract]
Tax effect of other components of income on investment securities and MBS	1,474				766					1,474	766
Difference in book and tax carrying value of fixed assets	20				776					20	776
Difference in book and tax basis of unearned loan fees	2,837				3,021					2,837	3,021
Difference in book and tax basis of deferred income from REIT subsidiary	2,262				0					2,262	0
Other	605				214					605	214
Total deferred tax liabilities	7,198				4,777					7,198	4,777
Net deferred tax asset (recorded in other assets)	9,228				22,265					$ 9,228	22,265
Income Tax Disclosure [Line Items]
Corporate income tax rate										35.00%
Recorded tax expense										$ 3,135
Valuation allowance of deferred tax assets	0				0					0	0
Bad debt reserve subject to recapture [Abstract]
Accumulated bad debt reserves for which no provision for income tax was required to be recorded	15,158				15,158					15,158	15,158
Additional income tax expense due to bad debt recapture										6,844	6,844
Unrecognized tax benefits	$ 0				$ 0					$ 0	$ 0
Plan [Member]
Income Tax Disclosure [Line Items]
Corporate income tax rate									21.00%