Goodwill and Other Intangible Assets (Goodwill) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($)
Goodwill [Roll Forward]
Goodwill, gross, beginning balance	$ 321,044
Accumulated impairment losses, beginning balance	(41,539)
Goodwill, net, beginning balance	279,505
Foreign currency translation adjustments	(25)
Goodwill, gross, ending balance	321,019
Accumulated impairment losses, ending balance	(41,539)
Goodwill, net, ending balance	279,480
Office Furniture
Goodwill [Roll Forward]
Goodwill, gross, beginning balance	137,845
Accumulated impairment losses, beginning balance	(41,396)
Goodwill, net, beginning balance	96,449
Foreign currency translation adjustments	(25)
Goodwill, gross, ending balance	137,820
Accumulated impairment losses, ending balance	(41,396)
Goodwill, net, ending balance	96,424
Hearth Products
Goodwill [Roll Forward]
Goodwill, gross, beginning balance	183,199
Accumulated impairment losses, beginning balance	(143)
Goodwill, net, beginning balance	183,056
Foreign currency translation adjustments	0
Goodwill, gross, ending balance	183,199
Accumulated impairment losses, ending balance	(143)
Goodwill, net, ending balance	$ 183,056