Revenue from Contracts with Customers - Revenue by sales channel (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Revenues				$ 230,828
Direct
Disaggregation of Revenue [Line Items]
Revenues	$ 139,908
Partner
Disaggregation of Revenue [Line Items]
Revenues				$ 90,920
ASC 606
Disaggregation of Revenue [Line Items]
Revenues		$ 321,607
ASC 606 | Direct
Disaggregation of Revenue [Line Items]
Revenues		186,130
ASC 606 | Partner
Disaggregation of Revenue [Line Items]
Revenues		$ 135,477
Operating Lease Expected Revenue
Disaggregation of Revenue [Line Items]
Revenues			$ 278,889
Operating Lease Expected Revenue | Direct
Disaggregation of Revenue [Line Items]
Revenues			164,084
Operating Lease Expected Revenue | Partner
Disaggregation of Revenue [Line Items]
Revenues			$ 114,805