Investments - Summary of Other Equity Investments (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Dec. 31, 2008
Schedule of Equity Method Investments [Line Items]
Other Equity Investments	$ 62,818	$ 69,320
G5 [Member]
Schedule of Equity Method Investments [Line Items]
Other Equity Investments	18,886	19,720
ABS [Member]
Schedule of Equity Method Investments [Line Items]
Other Equity Investments	43,932	46,851
Pan [Member]
Schedule of Equity Method Investments [Line Items]
Other Equity Investments	$ 0	$ 2,749	$ 4,158