Summary of Other Equity Investments (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2013 G5	Dec. 31, 2012 G5	Mar. 31, 2013 ABS	Dec. 31, 2012 ABS	Dec. 31, 2012 Pan	Dec. 31, 2008 Pan
Schedule of Equity Method Investments [Line Items]
Other Equity Investments	$ 63,957	$ 69,320	$ 20,323	$ 19,720	$ 43,634	$ 46,851	$ 2,749	$ 4,158