Capitalized Contract Cost (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2018	Jan. 01, 2018
Capitalized Contract Cost [Line Items]
Contract costs capitalized during the period		$ 32,827
Costs amortized during the period	$ 10,900	(33,642)
Change in capitalized contract cost, other		(540)
Balance of costs to obtain a contract	$ 14,688	$ 14,688	$ 16,043