Acquisitions and Acquisition Related Items - Additional Information (Detail) (USD $)	Mar. 31, 2013	Dec. 31, 2012	Nov. 08, 2012
Business Acquisition [Line Items]
Right to the Horizant business	$ 13,557,000	$ 13,557,000	$ 13,557,000

Amount of acquisition cost of a business combination allocated to assets, excluding financial assets and goodwill, lacking physical substance.

No definition available.

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