Concentration Risk - Additional Information (Detail)	6 Months Ended	12 Months Ended
	Jun. 30, 2012	Dec. 31, 2011
Customer One
Concentration Risk [Line Items]
Percentage of accounts receivable from one customer out of total accounts receivable	18.00%	23.00%
Customer Two
Concentration Risk [Line Items]
Percentage of accounts receivable from one customer out of total accounts receivable	10.00%	11.00%
Customer Concentration Risk
Concentration Risk [Line Items]
Percentage of revenue from one customer out of total revenue		19.00%