Accounts Receivable - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2011 Customer Concentration Risk Entity	Jun. 30, 2010 Customer Concentration Risk Entity	Jun. 30, 2011 Credit Concentration Risk	Dec. 31, 2010 Credit Concentration Risk
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of major customers	4	4
Revenues, major customers	$ 84.0	$ 60.4
Percentage of revenue from major customers	60.00%	51.00%
Accounts receivable, major customers			$ 28.3	$ 31.1
Percentage of accounts receivable from major customers			42.00%	43.00%