Revenues by Geographic Region (Detail)	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
Segment Reporting Information
Revenue by geographic region	100.00%		100.00%
United States
Segment Reporting Information
Revenue by geographic region	94.00%		94.00%
Canada
Segment Reporting Information
Revenue by geographic region	6.00%		6.00%
Other countries
Segment Reporting Information
Revenue by geographic region		[1]		[1]

[1] Less than 1% of revenue.