Summary of Significant Accounting Policies - Long-Lived Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Goodwill and intangible assets
Long-lived intangible impairment	$ 0	$ 0	$ 0
Total intangible assets	18,820	13,320
Less accumulated amortization	(13,320)	(12,856)
Net intangible assets	5,500	464
Amortization expense	500	800	$ 1,000
Estimated amortization expense
2022	0
2023	0
2024	300
2025	300
2026	300
Thereafter	4,600
Customer relationships
Goodwill and intangible assets
Total intangible assets	$ 5,376	5,376
Customer relationships | Minimum
Goodwill and intangible assets
Estimated useful lives	1 year
Customer relationships | Maximum
Goodwill and intangible assets
Estimated useful lives	8 years
Acquired contracts
Goodwill and intangible assets
Total intangible assets	$ 9,884	4,384
Acquired contracts | Minimum
Goodwill and intangible assets
Estimated useful lives	1 year
Acquired contracts | Maximum
Goodwill and intangible assets
Estimated useful lives	20 years
Contractual Rights to Manure Feedstock
Goodwill and intangible assets
Estimated useful lives	20 years
Contractual rights acquired	$ 5,500
Cash paid for Acquired contracts	1,000
Acquired contracts included in Accrued liabilities	$ 4,500
Initial term of contractual rights acquired	20 years
Trademark and trade names
Goodwill and intangible assets
Total intangible assets	$ 2,700	2,700
Trademark and trade names | Minimum
Goodwill and intangible assets
Estimated useful lives	2 years
Trademark and trade names | Maximum
Goodwill and intangible assets
Estimated useful lives	10 years
Non-compete agreements
Goodwill and intangible assets
Estimated useful lives	3 years
Total intangible assets	$ 860	$ 860