Summary Of Significant Accounting Policies (Rollforward Analysis Of The Allowance Against Accounts Receivable Balance) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Allowance for Bad Debt, Beginning Balance	$ (10,031)	$ (7,631)	$ (6,069)
Allowance for Bad Debt, Charged to costs and expenses	(2,699)	(2,400)	(1,562)
Allowance for Bad Debts, Foreign currency gain	880
Allowance for Bad Debt, Ending Balance	(11,850)	(10,031)	$ (7,631)
Gabon [Member]
Allowance for Bad Debt, Charged to costs and expenses	$ (2,700)	$ (2,400)