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Inventories Inventories (Policies)	12 Months Ended
Inventories Inventories (Policies)	Dec. 31, 2018
Inventory Disclosure [Abstract]
Inventories	Inventories Inventories consist principally of materials purchased for resale, including lumber, sheet goods, millwork, doors and windows, as well as certain manufactured products and are valued at the lower of cost or net realizable value, with cost being measured using a weighted average cost approach, which approximates the first-in, first-out approach.