Guarantees - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Guarantees [Abstract]
Deferred revenue included in other current and non-current liabilities	$ 29,700,000	$ 30,400,000
Amount of residual value guarantees and buyback commitments given by the company	$ 28,200,000	$ 32,800,000
Standard product warranty, low end of range (in months)	12 months
Standard product warranty, high end of range (in months)	60 months