Revenue Recognition (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Total revenues	$ 22,334,000	$ 59,215,000	$ 103,269,000
Deferred contract costs	0	0
Revenue, remaining performance obligation, amount			1,600,000
Contract with customer, liability	0	0
License revenue
Disaggregation of Revenue [Line Items]
Total revenues	$ 0	$ 0	$ 1,846,000