Commitments and Contingencies (Warranty activity) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Letters of Credit Outstanding, Amount	$ 7,200		$ 7,200
Movement in Standard Product Warranty Accrual [Roll Forward]
Standard Product Warranty Accrual, Increase (Decrease) for Preexisting Warranties	51	$ 169	(88)	$ 72
Accrued Expenses
Movement in Standard Product Warranty Accrual [Roll Forward]
Warranty accrual, beginning of period	4,851	2,898	3,840	2,980
Warranties issued	1,137	930	2,992	2,351
Settlements	(638)	(639)	(1,343)	(2,045)
Warranty accrual, end of period	5,401	$ 3,358	5,401	$ 3,358
Performance Bonds
Product Warranty Liability [Line Items]
Amount of performance bonds outstanding	$ 10,400		$ 10,400		$ 5,400