Summary of Significant Accounting Policies (Goodwill and Other Intangible Assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Oct. 02, 2020
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Asset Impairment Charges	$ 24,300
Other Asset Impairment Charges	12,000
Goodwill [Line Items]
Impairment of Long-Lived Assets to be Disposed of	36,285	$ 0	$ 0
Other Asset Impairment Charges	12,000
Asset Impairment Charges	24,300
Goodwill, Impairment Loss	50,307	0	0
Impairment of Intangible Assets, Finite-lived	0	$ 0	$ 10,000
Aerosystems [Member]
Goodwill [Line Items]
Reporting Unit, Amount of Fair Value in Excess of Carrying Amount				$ 56,100
Goodwill, Impairment Loss	50,300
U.K. Composites [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Asset Impairment Charges	24,300
Other Asset Impairment Charges	12,000
Goodwill [Line Items]
Other Asset Impairment Charges	12,000
Asset Impairment Charges	24,300
Translation Adjustment Functional to Reporting Currency, Gain (Loss), Reclassified to Earnings, Net of Tax	$ 22,856