New Accounting Pronouncements - Select Unaudited Consolidated Statement of Cash Flow Line Items (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash flows from operating activities:
Net loss	$ (45,875)	$ (24,774)
Changes in operating assets and liabilities, excluding the impact of acquisition of businesses:
Deferred commissions	(1,962)	(2,109)
Deferred revenue	$ 572	9,898
Accounting Standards Update 2014-09 | Calculated under Revenue Guidance in Effect before Topic 606
Cash flows from operating activities:
Net loss		(25,523)
Changes in operating assets and liabilities, excluding the impact of acquisition of businesses:
Deferred commissions		(175)
Deferred revenue		8,713
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Cash flows from operating activities:
Net loss		749
Changes in operating assets and liabilities, excluding the impact of acquisition of businesses:
Deferred commissions		(1,934)
Deferred revenue		$ 1,185