MANAGEMENT AGREEMENT AND RELATED PARTY TRANSACTIONS (Details 4) (Affiliates, USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Investments in affiliates
Investment in affiliates, number of issuers	28	32
Par	$ 2,100.0	$ 2,100.0
Corporate loans
Investments in affiliates
Par	1,900.0	2,000.0
Corporate debt securities
Investments in affiliates
Par	52.8	39.3
Equity investments, at estimated fair value
Investments in affiliates
Par	84.5	73.8
Joint ventures and partnerships
Investments in affiliates
Aggregate cost amount	$ 400.3	$ 137.6
Affiliated investments | Percent to total investment in corporate loans, debt securities and other investments
Investments in affiliates
Investment in affiliates as a percentage of total investment (in percentage)	27.00%	29.00%