Revenues by Geographic Region (Detail)
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Segment Reporting Information      
Revenue by geographic region 100.00% 100.00% 100.00%
United States      
Segment Reporting Information      
Revenue by geographic region 95.00% 95.00% 94.00%
Canada      
Segment Reporting Information      
Revenue by geographic region 3.00% 5.00% 6.00%
Other Countries      
Segment Reporting Information      
Revenue by geographic region 2.00%    [1]    [1]
[1] Less than 1% of revenue