Business and Basis of Presentation (Narrative) (Details) $ in Millions			1 Months Ended		6 Months Ended		12 Months Ended
	Jul. 18, 2018 USD ($)	Jan. 01, 2018 USD ($)	May 31, 2018 Facility	Jan. 31, 2017 Facility	Jun. 30, 2018	Jun. 30, 2017 USD ($)	Dec. 31, 2017	Nov. 17, 2017 USD ($)
Business And Basis Of Presentation [Line Items]
Corporate statutory tax rate					21.00%		35.00%
Tax cuts and jobs act of 2017 reclassification from AOCI to retained earnings		$ 54.3
ASU 2017-07 [Member] | Increase in Cost of Goods Sold [Member]
Business And Basis Of Presentation [Line Items]
Reclassification adjustment amount						$ 10.2
ASU 2017-07 [Member] | Increase in Selling General and Administrative Expenses [Member]
Business And Basis Of Presentation [Line Items]
Reclassification adjustment amount						5.6
ASU 2017-07 [Member] | Increase in Other Non-operating Income, Net [Member]
Business And Basis Of Presentation [Line Items]
Reclassification adjustment amount						$ 15.8
Tectum, Inc. [Member]
Business And Basis Of Presentation [Line Items]
Number of manufacturing facility | Facility				2
Plasterform, Inc. [Member]
Business And Basis Of Presentation [Line Items]
Number of manufacturing facility | Facility			1
Subsequent Event [Member]
Business And Basis Of Presentation [Line Items]
Potential adjustments to the purchase price consideration	$ 35.0
Potential adjustments to the purchase price consideration	20.0
August 1, 2018 [Member] | Subsequent Event [Member]
Business And Basis Of Presentation [Line Items]
Receivable from sale of business	250.0
September 15, 2018 [Member] | Subsequent Event [Member]
Business And Basis Of Presentation [Line Items]
Receivable from sale of business	$ 80.0
EMEA and Pacific Rim Business [Member]
Business And Basis Of Presentation [Line Items]
Consideration to be received in connection with sale of businesses								$ 330.0
WAVE [Member]
Business And Basis Of Presentation [Line Items]
Equity interest percentage					50.00%