Leases - Lease Costs and Other Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Finance lease cost:
Amortization of leased assets	$ 805,000	$ 1,143,000	$ 2,546,000	$ 2,796,000
Interest on lease liabilities	81,000	108,000	277,000	366,000
Operating lease cost	509,000	732,000	1,603,000	2,062,000
Short-term lease cost	380,000	494,000	1,255,000	1,474,000
Total lease cost	$ 1,775,000	$ 2,477,000	5,681,000	6,698,000
Variable lease income			0	0
Sublease income			0
Other information
Cash paid for amounts included in the measurement of lease liabilities			5,426,000	6,862,000
Operating cash flows from finance leases			276,000	366,000
Operating cash flows from operating leases			2,859,000	3,536,000
Financing cash flows from finance leases			2,291,000	2,960,000
Right-of-use assets obtained in exchange for new finance lease liabilities			243,000	1,142,000
Right-of-use assets obtained in exchange for new operating lease liabilities			$ (12,000)	$ 140,000
Lease Term and Discount Rate
Weighted-average remaining lease term in months - finance leases	1 year 10 months 28 days	2 years 8 months 23 days	1 year 10 months 28 days	2 years 8 months 23 days
Weighted-average remaining lease term in months - operating leases	7 years 11 months 12 days	7 years 10 months 17 days	7 years 11 months 12 days	7 years 10 months 17 days
Weighted-average discount rate - finance leases	6.30%	5.20%	6.30%	5.20%
Weighted-average discount rate - operating leases	11.40%	10.90%	11.40%	10.90%