Segment Reporting (Schedule of Net Sales by Segment) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information
Net sales	$ 536,616	$ 604,244	$ 684,455	$ 650,492	$ 547,137	$ 554,814	$ 547,483	$ 498,336	$ 2,475,807	$ 2,147,770	$ 1,678,898
OEM Segment
Segment Reporting Information
Net sales									2,242,616	1,976,623	1,548,091
Travel Trailer and Fifth Wheels
Segment Reporting Information
Net sales									1,440,730	1,405,983	1,099,882
Motorhomes
Segment Reporting Information
Net sales									187,297	159,417	116,191
OEMs Adjacent Industries
Segment Reporting Information
Net sales									614,589	411,223	332,018
Aftermarket Segment
Segment Reporting Information
Net sales									233,191	171,147	130,807
U.S.
Segment Reporting Information
Net sales									2,371,750	2,101,530	1,656,629
U.S. | OEM Segment
Segment Reporting Information
Net sales									2,149,162	1,940,893	1,531,896
U.S. | Travel Trailer and Fifth Wheels
Segment Reporting Information
Net sales									1,431,574	1,403,079	1,097,385
U.S. | Motorhomes
Segment Reporting Information
Net sales									143,488	138,895	108,961
U.S. | OEMs Adjacent Industries
Segment Reporting Information
Net sales									574,100	398,919	325,550
U.S. | Aftermarket Segment
Segment Reporting Information
Net sales									222,588	160,637	124,733
Int'l
Segment Reporting Information
Net sales									104,057	46,240	22,269
Int'l | OEM Segment
Segment Reporting Information
Net sales									93,454	35,730	16,195
Int'l | Travel Trailer and Fifth Wheels
Segment Reporting Information
Net sales									9,156	2,904	2,497
Int'l | Motorhomes
Segment Reporting Information
Net sales									43,809	20,522	7,230
Int'l | OEMs Adjacent Industries
Segment Reporting Information
Net sales									40,489	12,304	6,468
Int'l | Aftermarket Segment
Segment Reporting Information
Net sales									$ 10,603	$ 10,510	$ 6,074