Litigation and Related Matters (Narrative) (Details)	1 Months Ended	3 Months Ended		12 Months Ended	36 Months Ended
	Sep. 30, 2010 site	Mar. 31, 2021 USD ($) Litigation site	Mar. 31, 2020 USD ($)	Dec. 31, 2007	Dec. 31, 2020 USD ($)
Loss Contingencies [Line Items]
Number of active and independent litigation matters for which pursuing coverage and recoveries | Litigation		2
Settlement agreement amount of litigation agreement					$ 52,500,000
Environmental insurance recoveries received in excess of cumulative expenses incurred		$ 4,900,000			5,000,000.0
Environmental liabilities		900,000			1,200,000
Reserves for potential environmental liabilities		0	$ 0
Accounts Payable and Accrued Expenses [Member]
Loss Contingencies [Line Items]
Environmental liabilities		$ 0			300,000
Macon Site [Member]
Loss Contingencies [Line Items]
Number of landfills listed as Superfund site | site		2
Number of landfills AWI entered into an Administrative Order on Consent for a Removal Action | site	1
Submission date of final report to EPA	Oct. 11, 2016
Elizabeth City [Member]
Loss Contingencies [Line Items]
Percentage of site costs Navy agreed to pay				33.33%
Cost of Sales [Member]
Loss Contingencies [Line Items]
Settlement agreement amount of litigation agreement					9,200,000
SG&A Expenses [Member]
Loss Contingencies [Line Items]
Settlement agreement amount of litigation agreement					$ 38,300,000