LOANS RECEIVABLE AND INVESTMENTS (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable
Total investments reported as Secured loans receivable and investments, net, carrying amount	$ 526,553	$ 1,346,359
Total investments reported as Secured loans receivable and investments, net, amortized cost	519,463	1,345,557
Total investments reported as Secured loans receivable and investments, net, fair value	505,115	1,340,987
Total investments reported as Secured loans receivable and investments, net, unrealized gain	7,090	802
Total investments reported as Secured loans receivable and investments, net, unrealized gain	13,487	802
Total loans receivable and investments, net, carrying amount	780,285	1,406,216
Total loans receivable and investments, net, amortized cost	766,798	1,405,414
Total loans receivable and investments, net, fair value	758,450	1,399,836
Total loans receivable and investments, net, unrealized gain	7,090	802
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises
Accounts, Notes, Loans and Financing Receivable
Total investments reported as Secured loans receivable and investments, net, unrealized gain	7,090	802
Total loans receivable and investments, net, unrealized gain	7,090	802
Government-sponsored pooled loan investments, net, carrying amount and fair value	59,921	54,665
Government-sponsored pooled loan investments, amortized cost	52,831	53,863
Debt Securities
Accounts, Notes, Loans and Financing Receivable
Total investments reported as Secured loans receivable and investments, net, unrealized gain	6,397
Total loans receivable and investments, net, unrealized gain	6,397
Government-sponsored pooled loan investments, net, carrying amount and fair value	203,760	0
Government-sponsored pooled loan investments, amortized cost	197,363
Secured/ Mortgage Loans and Other
Accounts, Notes, Loans and Financing Receivable
Total investments reported as Secured loans receivable and investments, net, unrealized gain	0	0
Total loans receivable and investments, net, unrealized gain	0	0
Secured/mortgage loans and other, net, carrying amount	466,632	1,291,694
Secured/mortgage loans and other, net, amortized cost	466,632	1,291,694
Secured/mortgage loans and other, net, fair value	445,194	1,286,322
Non-Mortgage Loans Receivable, Net
Accounts, Notes, Loans and Financing Receivable
Total investments reported as Secured loans receivable and investments, net, unrealized gain	0	0
Total loans receivable and investments, net, unrealized gain	0	0
Non-mortgage loans receivable, net, carrying amount	49,972	59,857
Non-mortgage loans receivable, net, amortized cost	49,972	59,857
Non-mortgage loans receivable, net, fair value	$ 49,575	$ 58,849