Estimated Fair Values of Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012	Dec. 31, 2011
Fair Value Disclosures [Abstract]
Cash and cash equivalents, Carrying Value	$ 427,711	$ 640,147	$ 644,060	$ 570,854
Restricted cash and cash equivalents, Carrying Amount	24,486	18,116
Investments, Carrying Amount	21,044	45,992
Debt, Carrying Amount	(95,635)	(102,708)
Forward contracts, Carrying Amount	(42,892)	21,434
Cash and cash equivalents, Fair Value	427,711	640,147
Restricted cash and cash equivalents, Fair Value	24,486	18,116
Investments, Fair Value	21,044	45,992
Debt, Fair Value	(98,640)	(106,324)
Forward contracts, Fair Value	$ (42,892)	$ 21,434