MORTGAGE LOANS (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
MORTGAGE LOANS
Mortgage loans holdings	$ 6,528,890	$ 6,132,125
Mortgage loan call option period	12 years
Amount that would become due in remainder of 2017, if loans are called at their next call dates	$ 54,700
Amount that would become due in 2018 through 2022, if loans are called at their next call dates	976,200
Amount that would become due in 2023 through 2027, if loans are called at their next call dates	124,600
Amount that would become due after 2027, if loans are called at their next call dates	$ 9,900