Summary of Significant Accounting Policies - Contract Balances (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Changes in the Company's contract assets and contract liabilities
Contract asset, Beginning balance	$ 3,631	$ 500
Contract asset, Additions		8,000
Contract asset, Deductions	(8,000)	(500)
Contract Asset, Impact Of Netting.	4,369	(4,369)
Contract asset, Ending balance		3,631
Contract liabilities:
Contract liabilities (deferred revenue), Beginning balance	127,432	80,802
Contract liabilities (deferred revenue), Additions	42,050	65,816
Contract liabilities (deferred revenue), Deductions	(63,742)	(14,817)
Contract Liabilities (deferred revenue), Impact Of Netting	4,369	(4,369)
Contract liabilities (deferred revenue), Ending balance	$ 110,109	$ 127,432