INVESTMENT AND MORTGAGE-BACKED SECURITIES, Fiscal Year Maturity and Other Disclosures (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Transfers [Member]
OTTI and Non-credit Losses Recognized in Earnings and AOCI [Abstract]
Reductions for previous credit losses realized on securities sold during the year	$ (706)	$ 0
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Cumulative balance at the beginning of the period	756	807
Amortization	(50)	(51)
Reduction for previous credit losses realized on securities sold	(706)	0
Cumulative balance at end of the period	0	756	$ 807
Pooled Bank Trust Preferred Securities ("TRUP CDOs") [Member]
OTTI and Non-credit Losses Recognized in Earnings and AOCI [Abstract]
Cumulative pre-tax balance at the beginning of the period	9,157	9,295	9,514
(Amortization) Accretion of previously recognized OTTI	(80)	(138)	(219)
Reductions for previous credit losses realized on securities sold during the year	(9,077)
Cumulative pre-tax balance at end of the period	0	9,157	9,295
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Reduction for previous credit losses realized on securities sold	(9,077)
Pooled Bank Trust Preferred Securities ("TRUP CDOs") [Member] | Credit Related OTTI [Member]
OTTI and Non-credit Losses Recognized in Earnings and AOCI [Abstract]
Cumulative pre-tax balance at the beginning of the period	8,613	8,717	8,945
(Amortization) Accretion of previously recognized OTTI	(60)	(104)	(228)
Reductions for previous credit losses realized on securities sold during the year	(8,553)
Cumulative pre-tax balance at end of the period	0	8,613	8,717
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Reduction for previous credit losses realized on securities sold	(8,553)
Pooled Bank Trust Preferred Securities ("TRUP CDOs") [Member] | Non Credit Related OTTI [Member]
OTTI and Non-credit Losses Recognized in Earnings and AOCI [Abstract]
Cumulative pre-tax balance at the beginning of the period	544	578	569
(Amortization) Accretion of previously recognized OTTI	(20)	(34)	9
Reductions for previous credit losses realized on securities sold during the year	(524)
Cumulative pre-tax balance at end of the period	0	544	578
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Reduction for previous credit losses realized on securities sold	(524)
Registered Mutual Funds [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Cumulative balance at the beginning of the period	0	0
Cumulative balance at end of the period	$ 0	$ 0	$ 0