Concentration Risk - Additional Information (Detail)	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Concentration Risk [Line Items]
Number of customer accounting for more than ten percent of accounts receivable	3	1
Customer One
Concentration Risk [Line Items]
Percentage of accounts receivable from one customer out of total accounts receivable	19.00%	26.00%
Customer Two
Concentration Risk [Line Items]
Percentage of accounts receivable from one customer out of total accounts receivable	11.00%
Customer Three
Concentration Risk [Line Items]
Percentage of accounts receivable from one customer out of total accounts receivable	11.00%
Customer Concentration Risk
Concentration Risk [Line Items]
Percentage of revenue from one customer out of total revenue	19.00%
Number of customer accounting for more than ten percent of revenue	1