Accounts Receivable, net - Narrative (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended				6 Months Ended
	Dec. 31, 2019	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled revenues accrued	$ 22,200	$ 19,100				$ 22,200
Receivables outstanding balance	135,997	125,130				135,997
Provision (reversal) of allowance for doubtful accounts receivables		0		$ 5,491
Texas Customer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivables outstanding balance		$ 1,400
Amount of damages claimed	$ 1,400
Provision (reversal) of allowance for doubtful accounts receivables						$ 1,400
Renewable Energy Industry Customer | Services
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision (reversal) of allowance for doubtful accounts receivables			$ (1,000)	5,700	$ 700
Recovery from unrelated bad debt provision			$ 1,700	$ 200