INVESTMENTS - Investments, at Fair Value, Additional Information (Detail) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2016	Dec. 31, 2015
Schedule Of Investments In Marketable Securities [Line Items]
Securities sold short, proceeds	$ 68,170	$ 102,236
United States:
Schedule Of Investments In Marketable Securities [Line Items]
Total debt securities, cost	2,130,737	15,304,870
Total equity securities, cost	2,213	13,290,699
Europe:
Schedule Of Investments In Marketable Securities [Line Items]
Total debt securities, cost	1,008,521	4,207,531
Total equity securities, cost	701	7,627,245
Asia and other:
Schedule Of Investments In Marketable Securities [Line Items]
Total debt securities, cost	55,151	1,090,867
Total equity securities, cost	$ 163,082	$ 3,370,406