SECURITIES PURCHASED UNDER RESALE AGREEMENTS AND SOLD UNDER REPURCHASE AGREEMENTS (Details 2) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Amount of securities sold under repurchase agreements
Gross repurchase agreements	$ 450,000,000	$ 995,000,000
Weighted average interest rates (as a percent)	2.60%	3.70%
Extinguishment charges	$ (21,818,000)	$ 0	$ 0
Repurchase agreements extinguished	545,000,000
Maturities in 2016
Amount of securities sold under repurchase agreements
Gross repurchase agreements	0
Maturities in 2017
Amount of securities sold under repurchase agreements
Gross repurchase agreements	0
Maturities in 2018
Amount of securities sold under repurchase agreements
Gross repurchase agreements	0
Maturities in 2019
Amount of securities sold under repurchase agreements
Gross repurchase agreements	0
Maturities in 2020
Amount of securities sold under repurchase agreements
Gross repurchase agreements	0
Maturities in 2021 and thereafter
Amount of securities sold under repurchase agreements
Gross repurchase agreements	450,000,000
Repurchase Agreements
Amount of securities sold under repurchase agreements
Extinguishment charges	$ 21,818,000	$ 0	$ 0