Leases - Supplemental Balance Sheet Information (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Leases
Operating lease ROU assets	$ 13,461	$ 23,457
Financial position	us-gaap:OtherAssetsNoncurrent	us-gaap:OtherAssetsNoncurrent
Operating lease liabilities - current	$ 6,247	$ 10,479
Financial position	us-gaap:OtherLiabilitiesCurrent	us-gaap:OtherLiabilitiesCurrent
Operating lease liabilities - noncurrent	$ 8,812	$ 14,694
Financial position	us-gaap:OtherLiabilitiesNoncurrent	us-gaap:OtherLiabilitiesNoncurrent
Total Operating lease liabilities	$ 15,059	$ 25,173
Property and equipment, gross	160,645	174,960
Accumulated depreciation	(138,742)	(140,234)
Financing Lease ROU assets	$ 56	$ 248
Financial position	us-gaap:PropertyPlantAndEquipmentNet	us-gaap:PropertyPlantAndEquipmentNet
Finance lease liabilities - current	$ 41	$ 203
Financial position	us-gaap:OtherLiabilitiesCurrent	us-gaap:OtherLiabilitiesCurrent
Finance lease liabilities - noncurrent	$ 11	$ 55
Financial position	us-gaap:OtherLiabilitiesNoncurrent	us-gaap:OtherLiabilitiesNoncurrent
Finance lease liabilities	$ 52	$ 258
Weighted average remaining lease term - Operating leases	4 years	4 years
Weighted average remaining lease term - Financing leases	1 year	1 year
Weighted average discount rate - Operating leases	4.08%	4.32%
Weighted average discount rate - Financing leases	6.00%	6.00%
Finance lease assets
Leases
Property and equipment, gross	$ 333	$ 985
Accumulated depreciation	$ (277)	$ (737)