Short-term and Long-term Investments - Summary of Estimated Fair Value of Available-for-Sale Investments Classified by Contractual Maturities (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Amortized Cost And Fair Value Debt Securities [Abstract]
Due within one year	$ 98,380
After one year through three years	51,388
Aggregate Fair Value	$ 149,768	$ 188,561

Amount of debt securities categorized neither as held-to-maturity nor trading.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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Balance Type:	debit
Period Type:	instant