Summary of Significant Accounting Policies (Details 3) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Warranty activity
Warranty reserves, beginning of the year	$ 6,281	$ 7,844	$ 8,886
Accruals for warranties issued during the year	5,528	6,439	3,656
Reductions related to pre-existing warranties	(3,792)	(5,611)	(3,042)
Warranties paid	(2,078)	(2,372)	(1,629)
Other (principally foreign currency translation)	17	(19)	(27)
Warranty reserves, beginning of the year	5,956	6,281	7,844
Self-insurance
Loss Contingencies [Line Items]
Insurance expense from continuing operations	16,400	15,000	13,600
Decrease in pre-tax insurance expense due to retrospective insurance reserve adjustments from continuing operations	2,600	5,400	$ 8,500
Liabilities for asserted and unasserted claims	33,600	37,100
Liabilities covered by insurance carriers	$ 4,100	$ 3,500