Estimated Fair Values of Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Dec. 31, 2011
Fair Value Disclosures [Abstract]
Cash and cash equivalents, Carrying Value	$ 282,370	$ 640,147	$ 638,794	$ 570,854
Restricted cash and cash equivalents, Carrying Amount	18,488	18,116
Investments, Carrying Amount	17,282	45,992
Debt, Carrying Amount	(94,141)	(102,708)
Forward contracts, Carrying Amount	(17,569)	21,434
Cash and cash equivalents, Fair Value	282,370	640,147
Restricted cash and cash equivalents, Fair Value	18,488	18,116
Investments, Fair Value	17,282	45,992
Debt, Fair Value	(95,919)	(106,324)
Forward contracts, Fair Value	$ (17,569)	$ 21,434