Summary of Significant Accounting Policies - Fair Value (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jul. 15, 2016
Assets:
Other assets	$ 4,840		$ 5,064	$ 4,840
Total Assets	4,840		5,064	4,840
Liabilities:
Long term debt	312,384		269,739	312,384
Interest rate swaps	2,178		2,031	2,178
Total Liabilities	318,191		274,322	318,191
Reconciliation of liability related to earnout
Balance at the beginning of the period			3,100		$ 10,373
Adjustments to fair value	(600)	$ (1,186)	(900)	(1,786)
Payments to former owners				(5,487)
Balance at the end of the period	3,100			3,100
Related Party Transactions
Related Party Transaction, Purchases from Related Party			0	0
Advertising expenses
Advertising expenses incurred			5,213	4,471	4,269
Research and development expenses
Research and development expenses			3,194	2,926	3,132
Henderson
Liabilities:
Earnout	529		352	529
Dejana
Liabilities:
Earnout	3,100		2,200	3,100		$ 10,200
Level 3 | Henderson
Liabilities:
Earnout, portion in other current liabilities	87		352	87
Earnout, portion in other long term liabilities	442			442
Level 3 | Dejana
Liabilities:
Earnout, portion in other long term liabilities	3,100		2,200	3,100
Recurring | Level 2
Reconciliation of liability related to earnout
Derivative Liability, Current	597		127	597
Derivative Asset, Noncurrent			1,904
Derivative Liability, Noncurrent	1,581			1,581
Recurring | Level 3 | Henderson
Reconciliation of liability related to earnout
Balance at the beginning of the period			529	529	636
Payments to former owners			(177)	(107)
Balance at the end of the period	$ 529		352	529	529
Recurring | Level 3 | Dejana
Reconciliation of liability related to earnout
Balance at the beginning of the period				$ 3,100
Adjustments to fair value			(900)
Balance at the end of the period			$ 2,200		3,100
Fleet Pride Inc,
Related Party Transactions
Related Party Transaction, Purchases from Related Party					$ 242