Segment Reporting (Schedule of Net Sales by Segment) (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
Travel Trailer and Fifth Wheels
Segment Reporting Information
Total net sales									1,405,983	1,099,882	938,787
Motorhomes
Segment Reporting Information
Total net sales									159,417	116,191	86,513
OEMs Adjacent Industries
Segment Reporting Information
Total net sales									411,223	332,018	274,760
Aftermarket Segment
Segment Reporting Information
Total net sales									$ 171,147	$ 130,807	$ 103,006