Fair Value Measurements - Additional Information (Detail) (USD $)	6 Months Ended
Jun. 30, 2013	Jun. 30, 2012
Fair Value, Measurement Inputs, Disclosure [Line Items]
Marketable securities maturities	Twelve
Net unrealized gain (loss) included in comprehensive income related to marketable securities	$ 19,000	$ 19,000

Amount after tax, before reclassification adjustments, of unrealized holding gain (loss) on available-for-sale securities.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 11

-URI http://asc.fasb.org/extlink&oid=28358780&loc=d3e637-108580

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 10A

-Subparagraph (e)

-URI http://asc.fasb.org/extlink&oid=28358780&loc=SL7669646-108580

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration