Deferred Costs - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Deferred sales commissions	$ 30.7	$ 29.1
Deferred costs capitalized	2.8	2.7
Acquisition related costs	2.7
Amortization expense for deferred costs	$ 3.9	$ 3.3