Contract Assets, Contract Costs and Contract Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Contract with Customer, Asset, Net, Current	$ 108,645	$ 121,614
Increase (Decrease) in Contract with Customer, Asset Current	$ (12,969)
Increase (Decrease) in Contract with Customer Asset, Current, Percentage	(10.70%)
Capitalized Contract Cost, Net, Current	$ 3,511	6,052
increase (Decrease) in Capitalized Contract Cost Current	$ (2,541)
Increase (Decrease) in Capitalized Contract Cost, Current, Percentage	(42.00%)
Capitalized Contract Cost, Net, Noncurrent	$ 8,311	6,099
Increase (Decrease) in Capitalized Contract Cost Noncurrent	$ 2,212
Increase (Decrease) in Capitalized Contract Cost, Noncurrent, Percentage	36.30%
Contract with Customer, Liability, Current	$ 39,073	42,942
Increase (Decrease) in Contract with Customer Liability, Current	$ (3,869)
Increase (Decrease) in Contract with Customer Liability, Current, Percentage	(9.00%)
Contract with Customer, Liability, Noncurrent	$ 11,019	37,855
Increase (Decrease) in Contract with Customer Liability, Noncurrent	$ (26,836)
Increase (Decrease) in Contract with Customer Liability, Noncurrent, Percentage	(70.90%)
Government Contract Receivable, Progress Payment Offset	$ 32,400	30,200
Impairment of Long-Lived Assets to be Disposed of	36,285	0	$ 0
Capitalized Contract Cost, Amortization	11,500	11,600
Contract with Customer, Liability, Revenue Recognized	58,100	48,500
U.K. Composites [Member]
Disaggregation of Revenue [Line Items]
Contract with Customer, Asset, Net, Current	1,200
Contract Changes Negotiated Settlements and Claims [Member]
Disaggregation of Revenue [Line Items]
Contract with Customer, Asset, Net, Current	3,178	3,745
Costs to Fulfill [Member]
Disaggregation of Revenue [Line Items]
Capitalized Contract Cost, Net	9,300	6,600
Costs to Obtain [Member]
Disaggregation of Revenue [Line Items]
Capitalized Contract Cost, Net	$ 2,500	$ 5,600