Summary of Significant Accounting Policies - Opening and Closing Balances of the Company's Contract Assets and Deferred Revenue (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Contract assets, current portion
Beginning balance	$ 496
Ending balance	272
Change	(224)
Contract assets
Beginning balance	3,216
Ending balance	3,610
Change	394
Deferred Revenue, Current
Beginning balance	14,991
Ending balance	12,868
Change	(2,123)
Deferred Revenue
Beginning balance	27,852
Ending balance	23,576
Change	(4,276)
Deferred revenue related to leases, current portion	2,900	$ 3,800
Deferred revenue related to leases, noncurrent portion	$ 2,600	$ 7,900