Commitments and Contingencies - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Product liability reserves
Period over which product liability self-insurance retention levels have fluctuated (in years)	10 years
Product liability reserves	$ 20,800,000	$ 21,700,000
Warranty claims reserves	35,200,000	$ 28,600,000
Maximum
Product liability reserves
Product liability self-insurance maximum retention level for new occurrence	$ 2,000,000