Incremental Costs to Obtain a Contract with a Customer (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Commission and incentive payments
Capitalized Contract Cost [Line Items]
Total deferred costs	$ 63,037		$ 63,037		$ 68,293
Commission and incentive payments | Deferred costs included in prepaid and other current assets
Capitalized Contract Cost [Line Items]
Total deferred costs	41,180		41,180		41,955
Commission and incentive payments | Deferred costs included in other assets
Capitalized Contract Cost [Line Items]
Total deferred costs	21,857		21,857		$ 26,338
Deferred commissions
Capitalized Contract Cost [Line Items]
Amortization expense	$ 10,800	$ 10,800	$ 21,600	$ 21,700