Deferred Commissions (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Capitalized Contract Cost [Line Items]
Deferred commissions	$ 27,200,000		$ 27,200,000		$ 21,900,000
Deferred commissions amortization	4,100,000	$ 3,700,000	7,900,000	$ 7,100,000
Deferred commissions impairment	$ 0	$ 0	$ 0	$ 0
Minimum
Capitalized Contract Cost [Line Items]
Sales commissions amortization period			3 years
Maximum
Capitalized Contract Cost [Line Items]
Sales commissions amortization period			7 years