Fair Value Measurements - Estimated Fair Values of Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013	Dec. 31, 2012
Fair Value Disclosures [Abstract]
Cash and cash equivalents, Carrying Amount	$ 643,951	$ 118,702	$ 282,370	$ 640,147
Restricted cash and cash equivalents, Carrying Amount	239,315	23,652
Investments, Carrying Amount	2,613	13,511
Debt, Carrying Amount	(900,291)	(88,562)
Forward contracts, Carrying Amount	(30,438)	(28,767)
Cash and cash equivalents, Fair Value	643,951	118,702
Restricted cash and cash equivalents, Fair Value	239,315	23,652
Investments, Fair Value	2,613	13,511
Debt, Fair Value	(894,536)	(90,005)
Forward contracts, Fair Value	$ (30,438)	$ (28,767)