Summary of Significant Accounting Policies - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands					3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2022	Jul. 21, 2022	Jul. 20, 2022	Nov. 29, 2021	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021	May 01, 2021	Apr. 30, 2021
Revenue from External Customer [Line Items]
Restricted cash held in escrow	$ 20,100				$ 20,100		$ 20,100
Cash held in restricted account	13,700				13,700		13,700
Short term investments	146,936				146,936		146,936		$ 0
Transaction expenses		$ 8,299
Contingent consideration (in shares)		10,000,000
Stock issued (in shares)				1,000,000					0
Allowance for doubtful accounts	100				100		100		$ 0
Estimated value of total asset retirement obligation	5,968				5,968		5,968		$ 5,738
Net revenues after discount under purchase and sales agreement					66,550	$ 47,184	168,814	$ 104,968
Lease revenue under ASC 840					1,240	$ 1,459	2,920	3,286
Revenue recognized included in contract liabilities							9,785	$ 4,678
Backlog	$ 36,311				36,311		36,311
Class B Ordinary Share | Opal Fuels
Revenue from External Customer [Line Items]
Stock issued (in shares)		144,399,037
Redeemable non-controlling interests
Revenue from External Customer [Line Items]
Change in redemption value of Redeemable non-controlling interests					1,160,723
Sponsor Letter Agreement
Revenue from External Customer [Line Items]
Percentage of common stock subject to vesting and forfeiture conditions		10.00%
Common stock subject to vesting and forfeiture conditions, period		60 months
Contingent consideration (in shares)		763,908
Forward Purchase Agreement
Revenue from External Customer [Line Items]
Contingent consideration (in shares)	1,700,000
Sunoma Loan
Revenue from External Customer [Line Items]
Interest reserve	$ 1,778				1,778		1,778
Opal Term Loan II | Secured Debt
Revenue from External Customer [Line Items]
Contribution to joint venture	$ 5,800				$ 5,800		$ 5,800
Beacon
Revenue from External Customer [Line Items]
Percentage of ownership											44.30%
Beacon | Beacon
Revenue from External Customer [Line Items]
Subsequent ownership percentage										100.00%
Meteora | Forward Purchase Agreement
Revenue from External Customer [Line Items]
Contingent consideration (in shares)		2,000,000
Contingent consideration, escrow		$ 20,040
Contingent consideration, price (in dollars per share)		$ 10.02
Contingent consideration period		6 months
Meteora | Forward Purchase Agreement | ArcLight Class A Common STock
Revenue from External Customer [Line Items]
Stock issued (in shares)			2,000,000
Accounts Payable | Supplier Concentration Risk | One Vendor
Revenue from External Customer [Line Items]
Concentration risk percentage							22.00%
Two Customers | Revenue Benchmark | Customer Concentration Risk
Revenue from External Customer [Line Items]
Concentration risk percentage					49.00%	18.00%	45.00%	30.00%
Two Customers | Accounts Receivable | Customer Concentration Risk
Revenue from External Customer [Line Items]
Concentration risk percentage							38.00%
One Customer | Accounts Receivable | Customer Concentration Risk
Revenue from External Customer [Line Items]
Concentration risk percentage									11.00%
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-10-01
Revenue from External Customer [Line Items]
Backlog recognition period (in months)	12 months				12 months		12 months
Transferred over Time
Revenue from External Customer [Line Items]
Percentage of revenue recognized over time					28.00%	29.80%	24.60%	22.20%
RNG fuel
Revenue from External Customer [Line Items]
Lease revenue under ASC 840					$ 856	$ 694	$ 1,906	$ 1,644
RNG fuel | NextEra
Revenue from External Customer [Line Items]
Minimum of environmental attributes to be sold, percentage				90.00%
Net revenues after discount under purchase and sales agreement					19,335		49,023
Renewable Power
Revenue from External Customer [Line Items]
Lease revenue under ASC 840					$ 384	$ 765	$ 1,014	$ 1,642