Fair Value Disclosures - Quantitative Information about Level 3 Fair Value Measurements (Detail) (Other investments, at fair value [Member], Equity securities [Member], Star Asia [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Other investments, at fair value [Member] | Equity securities [Member] | Star Asia [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	$ 24,136	$ 30,169
Weighted average, Discount rate on debt	6.65%	6.82%
Range of Significant Inputs, Discount rate on debt	6.65%	6.82%