Purchase Price Allocation (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets	$ 15,700
Voxel Holdings Incorporated
Acquired Finite-Lived Intangible Assets [Line Items]
Cash and cash equivalents	930
Account receivable and other current assets	1,081
Property and equipment	4,795
Goodwill	20,007
Intangible assets	15,700
Other assets	336
Accounts payable and accrued expenses	(1,636)
Deferred revenue	(368)
Capital lease obligations	(1,288)
Other long-term liabilities	(137)
Deferred income tax liability	(6,140)	(6,140)
Business Acquisition, Purchase Price Allocation, Assets Acquired (Liabilities Assumed), Net, Total	$ 33,280