SECURITIES PURCHASED UNDER RESALE AGREEMENTS AND SOLD UNDER REPURCHASE AGREEMENTS (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Resale agreements
Gross resale agreements	$ 2,100,000	$ 2,050,000
Weighted average interest rates (as a percent)	1.73%	1.61%
Repurchase agreements
Gross repurchase agreements	$ 450,000	$ 450,000
Weighted average interest rates (as a percent)	2.90%	2.60%