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Related Party Transactions - Transactions with Joint Ventures (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2015
Related Party Transaction [Line Items]
Other (income) expense, net	$ 100
Other Nonoperating Income	$ 25	$ 68	$ 526	$ 257
Doosan-PSI, LLC \| Corporate Joint Venture
Related Party Transaction [Line Items]
Investment amount with related party					$ 1,000
Percent of noncontrolling interest					50.00%