Short-term Investments - Fair Values of Available-for-sale Securities by Contractual Maturity (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013
Short Term Investments Classified By Security Type [Abstract]
Maturing in one year or less	$ 26,725
Maturing after one year through three years	5,990
Fair value	$ 32,715

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

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

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant