Property and Equipment, Net - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Property, Plant and Equipment [Abstract]
Depreciation and amortization expense related to property and equipment	$ 3.3	$ 3.0	$ 9.6	$ 9.0
Property and equipment under capital lease	3.3		3.3		3.2
Accumulated depreciation related to assets under capital lease	3.0		3.0		2.6
Internal-use software development costs capitalized	1.0		2.0	0
Carrying value of internal-use software, net of accumulated amortization	10.6		10.6		9.3
Amortization of capitalized costs related to internal-use software	$ 0.6	$ 1.8	$ 1.3	$ 3.8