Description of Business and Summary of Significant Accounting Policies - Additional Information (Details)				1 Months Ended		3 Months Ended					6 Months Ended		12 Months Ended
	Mar. 09, 2021 USD ($) Installment	Feb. 19, 2021 USD ($)	Jan. 19, 2021 USD ($)	Feb. 28, 2021 USD ($)	Jan. 31, 2021 USD ($)	Jun. 30, 2021 USD ($) Facility $ / shares shares	Mar. 31, 2021 USD ($) Installment	Dec. 31, 2020 USD ($) $ / shares	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Jun. 30, 2021 USD ($) Acquisition Station Facility $ / shares shares	Jun. 30, 2020 USD ($)	Dec. 31, 2020 USD ($) $ / shares	Mar. 31, 2022 USD ($) $ / shares shares	Apr. 30, 2021 USD ($) $ / shares shares	Mar. 12, 2021 $ / shares shares	Oct. 20, 2020 $ / shares shares	Oct. 19, 2020 $ / shares shares	Dec. 31, 2019 USD ($)
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Number of facilities in operation | Facility						10					10
Number of acquisitions completed | Acquisition											7
Cash						$ 12,426,000		$ 26,644,000			$ 12,426,000		$ 26,644,000
Working capital deficit						78,100,000					78,100,000
Stockholders' deficit						(43,019,000)	$ (33,888,000)	$ (67,322,000)	$ (44,791,000)	$ (34,152,000)	(43,019,000)	$ (44,791,000)	$ (67,322,000)						$ (12,673,000)
Debt and lease obligations						132,300,000					132,300,000
Cash provided by operating activities											11,604,000	(18,381,000)
Net income						$ (9,154,000)	31,223,000		(10,508,000)	$ (13,702,000)	22,069,000	(24,210,000)
Pre-tax gain on extinguishment of debt											$ 800,000
Warrants to purchase common stock | shares																	5,072,000	7,925,000
Warrants, exercise price | $ / shares								$ 0.01					$ 0.01				$ 0.01	$ 2.50
ASU 2019-12 [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Change in accounting principle, accounting standards update, adopted						true					true
Change in accounting principle, accounting standards update, adoption date						Jan. 01, 2021					Jan. 01, 2021
Change in accounting principle, accounting standards update, immaterial effect						true					true
Bridge Loan and Executive Loans [Member] | Subsequent Event [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Aggregate amount														$ 9,800,000
Amendments to Secured Convertible Promissory Notes [Member] | Subsequent Event [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Warrants to purchase common stock | shares														7,553,750
Warrants, exercise price | $ / shares														$ 0.01
Aggregate amount														$ 9,500,000
USPS [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Compensation received for work performed							28,500,000
Payments for transportation settlements		$ 17,500,000	$ 7,100,000
Additional settlement payment including rate adjustments under settlement agreement								$ 3,800,000
Other operating revenue							34,800,000
Factoring Arrangements [Member] | Letter of Intent and Memo of Understanding [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Proceeds from transportation settlements	$ 1,600,000			$ 17,500,000	$ 7,100,000
Transportation settlements fund held in reserve	600,000
Repayment of factor advances	11,000,000.0						11,000,000.0
Amount retained to reduce outstanding principal amount of factoring advances	$ 6,900,000						$ 6,900,000
Number of installments for repayment | Installment	48						48
Frequency of payments	monthly						monthly
Date of first required payment	Jan. 01, 2022						Jan. 01, 2022
Funds held in reserve against advances utilized					$ 3,000,000.0
Funds held in reserve against advances	$ 800,000						$ 800,000
Paycheck Protection Program Loan, CARES Act [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Principal amount									$ 10,000,000.0			$ 10,000,000.0
Note Purchase Agreements and Releases [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Principal amount						$ 4,000,000.0					$ 4,000,000.0
Notes payable in cash						$ 600,000					$ 600,000				$ 100,000
Warrants to purchase shares of common stock | shares						1,481,453					1,481,453				231,453
Warrants, exercise price | $ / shares						$ 0.01					$ 0.01				$ 0.01	$ 2.50
Note Purchase Agreements and Releases [Member] | Maximum [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Warrants to purchase shares of common stock | shares																1,200,000
Note Purchase Agreements and Releases [Member] | Warrant Exercise Price of 2.50 Per Share [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Warrants, exercise price | $ / shares																$ 2.50
Note Purchase Agreements and Releases [Member] | Warrant Exercise Price of 2.50 Per Share [Member] | Maximum [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Warrants to purchase shares of common stock | shares																950,000
Note Purchase Agreements and Releases [Member] | Warrant Exercise Price of 0.01 Per Share [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Warrants, exercise price | $ / shares																$ 0.01
Note Purchase Agreements and Releases [Member] | Warrant Exercise Price of 0.01 Per Share [Member] | Maximum [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Warrants to purchase shares of common stock | shares																250,000
Loan Agreement [Member] | Main Street Loan [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Principal amount due							$ 16,700,000	33,600,000					$ 33,600,000
Principal amount								$ 17,000,000.0					17,000,000.0
Settlement Agreement [Member] | USPS [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Nonrecurring cash receipts											$ 28,500,000
Pre-tax nonrecurring revenue											$ 34,800,000
Deferred gain recognized													$ 6,300,000
CNG [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Number of fueling stations | Station											1
Number of compressed natural gas stations | Station											3