INVESTMENTS, AT FAIR VALUE - Investments, at Fair Value (Parenthetical) (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
United States [Member]
Schedule Of Investments In Marketable Securities [Line Items]
Total fixed income securities	$ 13,054,005	$ 13,320,475
Total equity securities	10,526,283	11,637,988
Europe [Member]
Schedule Of Investments In Marketable Securities [Line Items]
Total fixed income securities	3,085,553	4,383,068
Total equity securities	3,749,094	2,960,210
Asia and other [Member]
Schedule Of Investments In Marketable Securities [Line Items]
Total fixed income securities	1,099,405	1,298,868
Total equity securities	$ 2,298,307	$ 1,726,145