Litigation and Related Matters (Narrative) (Details) $ in Millions	1 Months Ended	3 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2010 site	Sep. 30, 2016 USD ($) Litigation	Sep. 30, 2016 USD ($) Litigation site	Sep. 30, 2015 USD ($)	Dec. 31, 2007	Dec. 31, 2015 USD ($)
Litigation And Related Matters [Line Items]
Number of active and independent litigation matters for which pursuing coverage and recoveries | Litigation		2	2
Potential environmental liabilities		$ 4.8	$ 4.8			$ 6.0
Reserves for potential environmental liabilities		2.0	2.5	$ 1.4
Recorded amount for probable recoveries		$ 0.0	$ 0.0			$ 0.0
Macon Site [Member]
Litigation And Related Matters [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
Maximum period required to submit Post-Removal Control Plan after EPA approves final report			120 days
Elizabeth City [Member]
Litigation And Related Matters [Line Items]
Percentage of site costs Navy agreed to pay					33.33%