Segment Information - Additional Information (Detail) - Segment	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Segment Reporting Information [Line Items]
Number of operating segments			2
Geographic Concentration Risk [Member] | U.S. [Member] | Revenues [Member]
Segment Reporting Information [Line Items]
Concentration risk percentage	80.20%	78.50%	79.90%	77.80%
Geographic Concentration Risk [Member] | U.S. [Member] | Consolidated Assets [Member]
Segment Reporting Information [Line Items]
Concentration risk percentage			90.90%		90.10%