Warranty Reserve (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Movement in Standard and Extended Product Warranty Accrual, Increase (Decrease) [Roll Forward]
Balance —	$ 30,459	$ 34,574	$ 31,095
Accruals for warranty expense, net of adjustments	35,001	28,364	33,113
Settlements made	(31,859)	(32,479)	(29,634)
Balance —	$ 33,601	$ 30,459	$ 34,574