Revenues, net - Additional Information (Details) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019	Mar. 31, 2020	Jan. 01, 2020	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable not billed	$ 71,489,000	$ 73,920,000
Provision for doubtful receivables	1,434,000	1,163,000	$ 1,346,000	$ 1,163,000	$ 1,168,000	$ 1,255,000	$ 956,000
Contract Acquisition Costs
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Impairment loss in relation to costs capitalized	0	0
Contract Fulfillment Costs
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Impairment loss in relation to costs capitalized	$ 0	$ 0
Previous U.S. GAAP Standards
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Provision for doubtful receivables				$ 1,163,000