Commitments And Contingencies - Narrative (Details) - USD ($)	9 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016	Dec. 31, 2015
Product Warranty Liability [Line Items]
Warranty claims reserves	$ 32,300,000	$ 32,300,000	$ 28,600,000	$ 32,400,000
Standard product warranty, low end of range (in months)	12 months
Standard product warranty, high end of range (in months)	60 months
Product liability reserves	$ 22,800,000		$ 21,700,000
Period over which product liability self-insurance retention levels have fluctuated (in years)	10 years
Maximum
Product Warranty Liability [Line Items]
Product liability self-insurance maximum retention level for new occurrence	$ 2,000,000