Geographic Concentrations - Additional Information (Detail) (Geographic Concentration Risk)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Foreign Countries | Sales Revenue, Segment
Concentration Risk [Line Items]
Number of foreign countries representing more than ten percent	0	0	0
Foreign Countries | Property, Plant and Equipment
Concentration Risk [Line Items]
Number of foreign countries representing more than ten percent	0	0
Minimum | United States | Sales Revenue, Segment
Concentration Risk [Line Items]
Concentration risk	90.00%	90.00%	90.00%
Minimum | United States | Property, Plant and Equipment
Concentration Risk [Line Items]
Concentration risk	87.00%	84.00%