Geographic Information and Major Customers - Additional Information (Detail)	3 Months Ended		12 Months Ended
	Mar. 31, 2013 Customer	Mar. 31, 2012 Customer	Dec. 31, 2012 Customer
Geographic Reporting Disclosure [Line Items]
Number of reportable segments	1
Major customer percentage	10.00%	10.00%
Number of customers accounting for 10% or more of company total revenue	0
Trade accounts receivable
Geographic Reporting Disclosure [Line Items]
Number of customers accounting for 10% or more of company total revenue	0	1	1
Trade accounts receivable | Minimum
Geographic Reporting Disclosure [Line Items]
Percentage of company outstanding trade receivables accounted by one customer	10.00%		10.00%