Summary of Significant Accounting Policies - Contract Balances (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 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	3,000	500
Contract Asset, Impact Of Netting.	411
Contract asset, Ending balance	1,042
Contract liabilities:
Contract liabilities, Beginning balance	127,432	80,802
Contract liabilities, Additions		65,287
Contract liabilities, Deductions	(1,228)	(158)
Contract Liabilities, Impact Of Netting	411
Contract liabilities, Ending balance	$ 126,615	$ 145,931