Summary of Significant Accounting Policies - Contract Balances (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Changes in the Company's contract assets and contract liabilities
Contract asset, Beginning balance	$ 3,631	$ 500
Contract asset, Additions		0
Contract asset, Deductions	8,000	500
Contract Asset, Impact Of Netting.	4,369
Contract liabilities:
Contract liabilities, Beginning balance	127,432	80,802
Contract liabilities, Additions	50	65,287
Contract liabilities, Deductions	(1,325)	(237)
Contract Liabilities, Impact Of Netting	4,369
Contract liabilities, Ending balance	$ 130,526	$ 145,852