Investment in equity investees (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Equity Method Investment Summarized Financial Information Income Statement Abstract
Income Tax Expense Benefit	$ (237,380)	$ (77,893)	$ (294,257)	$ (61,701)
Equity Method Investee Member | E V E R T E C Inc [Member]
Equity Method Investment Summarized Financial Information Income Statement Abstract
Revenues	79,825	71,702	152,221	143,197
Equity Method Investment Summarized Financial Information Expenses	149,772	74,535	216,645	141,445
Income Tax Expense Benefit	(5,012)	(88,526)	(4,961)	(87,472)
Equity Method Investment Summarized Financial Information Net Income Loss	(64,935)	85,693	(59,463)	89,224
Equity Method Investment Summarized Financial Information Abstract
Equity Method Investment Summarized Financial Information Assets	947,281		947,281		977,745
Equity Method Investment Summarized Financial Information Liabilities	$ 780,604		$ 780,604		$ 855,290