INVESTMENT AND MORTGAGE-BACKED SECURITIES, Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Registered Mutual Funds [Member]
Available-for-Sale Securities, Fair Value [Abstract]
Less than 12 Consecutive Months		$ 0
12 Consecutive Months or Longer		2,591
Total		2,591
Available-for-Sale Securities, Unrealized Losses [Abstract]
Less than 12 Consecutive Months		0
12 Consecutive Months or Longer		84
Total		84
Pass-through MBS Issued by Government Sponsored Entities ("GSEs") [Member]
Available-for-Sale Securities, Fair Value [Abstract]
Less than 12 Consecutive Months	$ 215,028	55,819
12 Consecutive Months or Longer	0	0
Total	215,028	55,819
Available-for-Sale Securities, Unrealized Losses [Abstract]
Less than 12 Consecutive Months	1,889	325
12 Consecutive Months or Longer	0	0
Total	1,889	325
Agency Collateralized Mortgage Obligation ("CMO") [Member]
Available-for-Sale Securities, Fair Value [Abstract]
Less than 12 Consecutive Months	45,534	86,746
12 Consecutive Months or Longer	3,063	3,168
Total	48,597	89,914
Available-for-Sale Securities, Unrealized Losses [Abstract]
Less than 12 Consecutive Months	881	96
12 Consecutive Months or Longer	85	69
Total	$ 966	$ 165