Short-term Investments - Short-term Investments Available-for-sale Securities (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	$ 56,828	$ 32,693
Gross unrealized gains	27	25
Gross unrealized losses	(18)	(3)
Fair value	56,837	32,715
U.S. government-related debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	1,550	1,565
Gross unrealized gains	1	1
Gross unrealized losses
Fair value	1,551	1,566
Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	55,278	31,128
Gross unrealized gains	26	24
Gross unrealized losses	(18)	(3)
Fair value	$ 55,286	$ 31,149

Available For Sale Securities Gross Unrealized Gains Accumulated In Investments

No definition available.

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- Definition

Amount of accumulated pre-tax unrealized loss before deducting pre-tax unrealized gain on investments in available-for-sale securities impacting investments.

+ References

No definition available.

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- Definition

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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- Definition

Investments which are intended to be sold in the short term (usually less than one year or the normal operating cycle, whichever is longer) including trading securities, available-for-sale securities, held-to-maturity securities, and other short-term investments not otherwise listed in the existing taxonomy.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.2)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 1

-Subparagraph g

-Article 7

+ Details

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