Incremental Costs to Obtain a Contract with a Customer (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Commission and incentive payments
Capitalized Contract Cost [Line Items]
Total deferred costs	$ 62,710		$ 62,710		$ 68,293
Commission and incentive payments | Deferred costs included in prepaid and other current assets
Capitalized Contract Cost [Line Items]
Total deferred costs	41,085		41,085		41,955
Commission and incentive payments | Deferred costs included in other assets
Capitalized Contract Cost [Line Items]
Total deferred costs	21,625		21,625		$ 26,338
Deferred commissions
Capitalized Contract Cost [Line Items]
Amortization expense	$ 10,900	$ 11,200	$ 32,500	$ 32,900