VARIABLE INTEREST ENTITIES - FINANCING RECEIVABLES (Credit Risk Profiles of Middle Market Loans) (Details) (RSO [Member], USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable, Impaired [Line Items]
Loans and receivables	$ 1,935,793	$ 1,377,037
Middle-market Loans [Member]
Financing Receivable, Impaired [Line Items]
Loans and receivables	250,113	44,253
Rating 1 [Member] | Middle-market Loans [Member]
Financing Receivable, Impaired [Line Items]
Loans and receivables	0	0
Rating 2 [Member] | Middle-market Loans [Member]
Financing Receivable, Impaired [Line Items]
Loans and receivables	240,245	39,780
Rating 3 [Member] | Middle-market Loans [Member]
Financing Receivable, Impaired [Line Items]
Loans and receivables	9,868	0
Rating 4 [Member] | Middle-market Loans [Member]
Financing Receivable, Impaired [Line Items]
Loans and receivables	0	0
Rating 5 [Member] | Middle-market Loans [Member]
Financing Receivable, Impaired [Line Items]
Loans and receivables	0	0
Held for Sale [Member] | Middle-market Loans [Member]
Financing Receivable, Impaired [Line Items]
Loans and receivables	$ 0	$ 4,473