Purchase Price Allocation of ISD Corporation Acquisition (Detail) (ISD Corporation, USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 Year
Schedule of Business Acquisitions, Purchase Price Allocation [Line Items]
Cash	$ 2,375
Accounts Receivable	2,030
Other current assets	958
Total current assets acquired	5,363
Property and equipment	519
Goodwill	11,380
Total assets acquired	23,906
Current liabilities acquired	(4,681)
Net assets acquired	19,225
Intellectual property rights
Schedule of Business Acquisitions, Purchase Price Allocation [Line Items]
Amortizable intangible assets	2,338
Acquired intangible assets, weighted-average useful lives (in years)	5
Customer relationships
Schedule of Business Acquisitions, Purchase Price Allocation [Line Items]
Amortizable intangible assets	4,059
Acquired intangible assets, weighted-average useful lives (in years)	9
Trade Name
Schedule of Business Acquisitions, Purchase Price Allocation [Line Items]
Amortizable intangible assets	$ 247
Acquired intangible assets, weighted-average useful lives (in years)	5