Fair Value Measurements - Additional Information (Detail) (Certificates of Deposit, Fair Value, Inputs, Level 2, USD $) In Millions, unless otherwise specified	Dec. 31, 2012
Certificates of Deposit \| Fair Value, Inputs, Level 2
Fair Value Measurements Disclosure [Line Items]
Assets at fair value	$ 2.8

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=25499696&loc=d3e19207-110258

Name:	us-gaap_AssetsFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant