Segment Reporting (Disaggregation of Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation of Revenue [Line Items]
Net sales	$ 684,455	$ 547,483	$ 1,334,947	$ 1,045,819
OEM Segment
Disaggregation of Revenue [Line Items]
Net sales	616,918	502,775	1,217,097	964,804
Travel trailers and fifth-wheels
Disaggregation of Revenue [Line Items]
Net sales	399,464	357,251	804,421	687,525
Motorhomes
Disaggregation of Revenue [Line Items]
Net sales	49,071	36,248	101,986	73,292
Adjacent industries OEMs
Disaggregation of Revenue [Line Items]
Net sales	168,383	109,276	310,690	203,987
Aftermarket Segment
Disaggregation of Revenue [Line Items]
Net sales	67,537	44,708	117,850	81,015
Chassis, chassis parts and slide-out mechanisms | OEM Segment
Disaggregation of Revenue [Line Items]
Net sales	247,811	235,516	500,514	458,465
Windows and doors | OEM Segment
Disaggregation of Revenue [Line Items]
Net sales	169,372	109,393	318,892	206,593
Furniture and mattresses | OEM Segment
Disaggregation of Revenue [Line Items]
Net sales	105,278	82,740	210,796	153,914
Axles and suspension solutions | OEM Segment
Disaggregation of Revenue [Line Items]
Net sales	33,148	32,359	66,753	64,540
Other | OEM Segment
Disaggregation of Revenue [Line Items]
Net sales	61,309	42,767	120,142	81,292
U.S.
Disaggregation of Revenue [Line Items]
Net sales	658,373	537,828	1,286,275	1,027,402
U.S. | OEM Segment
Disaggregation of Revenue [Line Items]
Net sales	593,944	495,818	1,174,500	951,431
U.S. | Travel trailers and fifth-wheels
Disaggregation of Revenue [Line Items]
Net sales	397,511	356,689	801,253	686,007
U.S. | Motorhomes
Disaggregation of Revenue [Line Items]
Net sales	37,553	32,741	80,959	66,503
U.S. | Adjacent industries OEMs
Disaggregation of Revenue [Line Items]
Net sales	158,880	106,388	292,288	198,921
U.S. | Aftermarket Segment
Disaggregation of Revenue [Line Items]
Net sales	64,429	42,010	111,775	75,971
International
Disaggregation of Revenue [Line Items]
Net sales	26,082	9,655	48,672	18,417
International | OEM Segment
Disaggregation of Revenue [Line Items]
Net sales	22,974	6,957	42,597	13,373
International | Travel trailers and fifth-wheels
Disaggregation of Revenue [Line Items]
Net sales	1,953	562	3,168	1,518
International | Motorhomes
Disaggregation of Revenue [Line Items]
Net sales	11,518	3,507	21,027	6,789
International | Adjacent industries OEMs
Disaggregation of Revenue [Line Items]
Net sales	9,503	2,888	18,402	5,066
International | Aftermarket Segment
Disaggregation of Revenue [Line Items]
Net sales	$ 3,108	$ 2,698	$ 6,075	$ 5,044