Revenue (Revenue by Product Category) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Net sales	$ 979,896	$ 946,375	$ 1,900,775	$ 1,771,780
Millwork, doors & windows [Member]
Disaggregation of Revenue [Line Items]
Net sales	287,999	271,135	583,668	511,057
Structural components [Member]
Disaggregation of Revenue [Line Items]
Net sales	164,535	166,955	324,879	308,231
Lumber & lumber sheet goods [Member]
Disaggregation of Revenue [Line Items]
Net sales	292,817	281,855	551,956	523,814
Other building products & services [Member]
Disaggregation of Revenue [Line Items]
Net sales	$ 234,545	$ 226,430	$ 440,272	$ 428,678