Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2019

Schedule of inventories

Inventories consisted of the following as of December 31, 2018 and 2019 (in thousands):

	2018		2019
Raw materials and spare parts	$	34,890	$	29,874
Finished goods		85		—
Total inventory	$	34,975	$	29,874

Schedule of finite-lived intangible assets

The Company’s intangible assets as of December 31, 2018 and 2019 were as follows (in thousands):

	2018		2019
Customer relationships	$	5,376	$	5,376
Acquired contracts		4,384		4,384
Trademark and trade names		2,700		2,700
Non-compete agreements		860		860
Total intangible assets		13,320		13,320
Less accumulated amortization		(11,113)		(12,091)
Net intangible assets	$	2,207	$	1,229

Schedule of goodwill

The following table summarizes the activity related to the carrying amount of goodwill (in thousands):

Balance as of December 31, 2017	$	64,328
Balance as of December 31, 2018	$	64,328
Balance as of December 31, 2019	$	64,328

ASC 606

Schedule of adoption adjustments

The ASC 606 adoption adjustments are as follows, and relate to significant financing components resulting from an advance payment by a customer of the Company’s subsidiary, NG Advantage LLC (“NG Advantage”) and an extended payment term to a station construction customer (in thousands):

	Balance as of		Adjustments		Balance as of
	December 31, 2017		due to ASC 606		January 1, 2018
Notes receivable and other long-term assets, net	$	21,397	$	(963)	$	20,434
Deferred revenue	$	3,432	$	330	$	3,762
Accumulated deficit	$	(683,570)	$	(1,293)	$	(684,863)

ASC 842

Schedule of adoption adjustments

The effect of adopting ASC 842 was as follows (in thousands):

	Balance as of		Adjustments		Balance as of
	December 31, 2018		Due to ASC 842		January 1, 2019
Operating lease right-of-use assets	$	—	$	24,453	$	24,453
Operating lease obligations	$	—	$	25,943	$	25,943
Accrued liabilities	$	48,469	$	(496)	$	47,973
Other long-term liabilities	$	15,035	$	(994)	$	14,041