MARKETABLE SECURITIES - Narrative (Details)	6 Months Ended
	Jun. 30, 2017 USD ($) security position	Jun. 30, 2016 security	Dec. 31, 2016 USD ($) position
Schedule of Available-for-sale Securities [Line Items]
Securities held to maturity	$ 182,248,000		$ 189,371,000
Unrealized losses	1,130,000		4,700,000
Other than temporary impairment losses on debt securities related to credit losses	$ 0		$ 0
Number of positions in an unrealized loss position | position	100		177
Fair value of securities pledged as collateral	$ 245,600,000		$ 259,499,000
Number of held-to-maturity securities sold | security	3	3
Non-Agency Collateralized Mortgage Obligations
Schedule of Available-for-sale Securities [Line Items]
Securities held to maturity	$ 1,522,000
Unrealized losses	$ 507,000