Segment Reporting (Schedule of Net Sales by Product) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information
Total net sales	$ 547,137	$ 554,814	$ 547,483	$ 498,336	$ 402,899	$ 412,370	$ 440,831	$ 422,798	$ 2,147,770	$ 1,678,898	$ 1,403,066
OEM Segment
Segment Reporting Information
Total net sales									1,976,623	1,548,091	1,300,060
Aftermarket Segment
Segment Reporting Information
Total net sales									171,147	130,807	103,006
Chassis, Chassis Parts and Slide-out Mechanisms | OEM Segment
Segment Reporting Information
Total net sales									914,397	743,160	664,542
Windows and Doors | OEM Segment
Segment Reporting Information
Total net sales									424,625	335,717	301,171
Furniture and Mattresses | OEM Segment
Segment Reporting Information
Total net sales									342,680	245,596	161,840
Axles and Suspension Solutions | OEM Segment
Segment Reporting Information
Total net sales									123,513	115,538	108,464
Other Products | OEM Segment
Segment Reporting Information
Total net sales									$ 171,408	$ 108,080	$ 64,043