Revenue (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net sales	$ 920,879	$ 825,405
Contract assets change	6,214
Contract liabilities change	6,765
Revenue recognized previously included in contract liabilities	24,400
Building Products [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net sales	686,700	620,900
Construction Services [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net sales	$ 234,200	$ 204,500