Estimated Fair Values of Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Fair Value Disclosures [Abstract]
Cash and cash equivalents, Carrying Value	$ 118,702	$ 640,147	$ 570,854	$ 403,463
Restricted cash and cash equivalents, Carrying Amount	23,652	18,116
Investments, Carrying Amount	13,511	45,992
Debt, Carrying Amount	(88,562)	(102,708)
Derivative contracts, Carrying amount	(28,767)	21,434
Cash and cash equivalents, Fair Value	118,702	640,147
Restricted cash and cash equivalents, Fair Value	23,652	18,116
Investments, Fair Value	13,511	45,992
Debt, Fair Value	(90,005)	(106,324)
Derivative contracts, Fair Value	$ (28,767)	$ 21,434