Significant Accounting Policies - Assessment of Revenue under ASC 606 (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Sep. 30, 2020
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Amounts invoiced and not collected, beginning	$ 48,883		$ 9,006
Amounts invoiced and not collected, ending	9,006	$ 48,883	1,766
Deferred Cost of Sales, After Transition Adjustment	6,415		1,261
Deferred Cost of Sales, After Transition Adjustment	1,261	6,415	247
Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Amounts Invoiced and Not Collected, Transition Adjustment		21,385
Proceeds from Sale and Collection of Receivables	8,219		7,240
Amounts Invoiced and Not Collected, Write-off of Deferred Costs for Customer Contracts where Collection is no Longer Reasonable Assured		10,273
Deferred Cost of Sales, Transition Adjustment		2,565
Deferred Cost of Sales, Cash Collected	$ 1,151		$ 1,014
Deferred Cost of Sales, Write-off of Deferred Costs for Customer Contracts Where Collection is No Longer Reasonably Assured		$ 1,438