LOANS HELD FOR INVESTMENT - Portfolio Activity (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Change in the activity of loan portfolio
Balance at the beginning of the period			$ 1,313,937,000
Initial funding			491,561,000
Origination fees and discounts, net of costs			(6,138,000)
Additional funding			12,993,000
Amortizing payments			(251,000)
Loan payoffs			(273,734,000)
Origination fee accretion			4,893,000	$ 3,717,000
Balance at the end of the period	$ 1,543,261,000		1,543,261,000
Impairment charges recognized	$ 0	$ 0	$ 0	$ 0