Summary of Cash, Cash Equivalents and Marketable Securities (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013	Dec. 31, 2012
Cash, cash equivalents and marketable securities [Line Items]
Amortized Cost	$ 575,040	$ 636,504
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	575,040	636,504
Cash and cash equivalents	575,040	636,504	588,462	387,196
Cash [Member]
Cash, cash equivalents and marketable securities [Line Items]
Amortized Cost	163,040	495,990
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	163,040	495,990
Cash and cash equivalents	163,040	495,990
Time deposits [Member]
Cash, cash equivalents and marketable securities [Line Items]
Amortized Cost	412,000	140,514
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	412,000	140,514
Cash and cash equivalents	$ 412,000	$ 140,514