Goodwill and Other Intangible Assets (Details)	12 Months Ended															12 Months Ended						1 Months Ended		12 Months Ended	1 Months Ended	12 Months Ended	1 Months Ended	12 Months Ended	1 Months Ended	12 Months Ended
	Dec. 31, 2014 USD ($)		Dec. 31, 2013 USD ($)		Dec. 31, 2012 USD ($)	Dec. 31, 2014 Customer Relationships [Member] USD ($)	Dec. 31, 2013 Customer Relationships [Member] USD ($)	Dec. 31, 2014 Trademarks and Trade Names [Member] USD ($)	Dec. 31, 2013 Trademarks and Trade Names [Member] USD ($)	Dec. 31, 2014 Non-Compete Agreements [Member] USD ($)	Dec. 31, 2013 Non-Compete Agreements [Member] USD ($)	Dec. 31, 2014 Patents and Supply Contracts [Member] USD ($)	Dec. 31, 2013 Patents and Supply Contracts [Member] USD ($)	Dec. 31, 2014 Leaseholds [Member] USD ($)	Dec. 31, 2013 Leaseholds [Member] USD ($)	Dec. 31, 2014 Computer Software [Member] USD ($)	Dec. 31, 2013 Computer Software [Member] USD ($)	Dec. 31, 2012 Computer Software [Member] USD ($)	Dec. 31, 2014 Computer Software [Member] Minimum [Member]	Dec. 31, 2014 Computer Software [Member] Maximum [Member]	Dec. 31, 2014 CompressorWorks, Inc. [Member] Leaseholds [Member]	Feb. 28, 2013 SMP Europe [Member] USD ($)	Feb. 28, 2013 SMP Europe [Member] GBP (£)	Dec. 31, 2013 SMP Europe [Member] USD ($)	Feb. 28, 2013 SMP Europe [Member] Customer Relationships [Member] USD ($)	Dec. 31, 2014 SMP Europe [Member] Customer Relationships [Member] USD ($)	Jan. 31, 2014 Pensacola Fuel Injection Inc. [Member] USD ($)	Dec. 31, 2014 Pensacola Fuel Injection Inc. [Member] USD ($)	Apr. 30, 2014 Annex Manufacturing [Member] USD ($)	Dec. 31, 2014 Annex Manufacturing [Member] USD ($)	Dec. 31, 2014 Annex Manufacturing [Member] Customer Relationships [Member] USD ($)	Dec. 31, 2014 Annex Manufacturing [Member] Non-Compete Agreements [Member] USD ($)	Dec. 31, 2014 Engine Management [Member] USD ($)	Dec. 31, 2013 Engine Management [Member] USD ($)	Dec. 31, 2013 Engine Management [Member] SMP Europe [Member] USD ($)	Dec. 31, 2014 Engine Management [Member] Pensacola Fuel Injection Inc. [Member] USD ($)	Dec. 31, 2014 Engine Management [Member] Annex Manufacturing [Member] USD ($)	Dec. 31, 2014 Temperature Control [Member] USD ($)	Dec. 31, 2013 Temperature Control [Member] USD ($)	Dec. 31, 2013 Temperature Control [Member] SMP Europe [Member] USD ($)	Dec. 31, 2014 Temperature Control [Member] Pensacola Fuel Injection Inc. [Member] USD ($)	Dec. 31, 2014 Temperature Control [Member] Annex Manufacturing [Member] USD ($)
Goodwill by operating segment [Abstract]
Goodwill gross, Beginning balance	$ 76,493,000		$ 74,315,000																														$ 66,790,000	$ 64,612,000				$ 9,703,000	$ 9,703,000
Goodwill accumulated impairment loss, Beginning balance	(38,488,000)		(38,488,000)																														(38,488,000)	(38,488,000)				0	0
Goodwill net, Beginning balance	38,005,000		35,827,000																														28,302,000	26,124,000				9,703,000	9,703,000
Goodwill acquired during period																						2,000,000		2,027,000			12,500,000	12,528,000	4,600,000	4,567,000					2,027,000	12,528,000	0			0	0	4,567,000
Goodwill foreign currency exchange rate change	(125,000)		151,000																														(125,000)	151,000				0	0
Goodwill gross, Ending balance	93,463,000		76,493,000		74,315,000																												79,193,000	66,790,000				14,270,000	9,703,000
Goodwill accumulated impairment loss, Ending balance	(38,488,000)		(38,488,000)		(38,488,000)																												(38,488,000)	(38,488,000)				0	0
Goodwill net, Ending balance	54,975,000		38,005,000		35,827,000																							12,528,000		4,567,000			40,705,000	28,302,000				14,270,000	9,703,000
Purchase price paid in cash																											12,200,000	12,225,000	11,500,000	11,500,000
Purchase price of business																						6,500,000	4,200,000
Goodwill acquired in business acquisition																						2,000,000		2,027,000			12,500,000	12,528,000	4,600,000	4,567,000					2,027,000	12,528,000	0			0	0	4,567,000
Acquired Indefinite-lived Intangible Assets [Line Items]
Total acquired intangible assets	57,299,000		52,772,000			48,646,000	44,179,000	6,800,000	6,800,000	970,000	910,000	723,000	723,000	160,000	160,000
Less accumulated amortization	(24,120,000)	[1]	(19,202,000)	[1]
Net acquired intangible assets	33,179,000		33,570,000
Intangible assets acquired [Abstract]
Amount of acquired indefinite-lived intangible assets								5,200,000
Intangible assets acquired in business acquisition																									3,800,000	3,800,000					4,700,000	100,000
Estimated useful life of intangible assets																			3 years	10 years	5 years				10 years	10 years					7 years	5 years
Amortization of acquired intangible assets [Abstract]
Amortization expense	5,000,000		5,000,000		4,700,000
Estimated amortization expense in year 2015	5,000,000
Estimated amortization expense in year 2016	4,900,000
Estimated amortization expense in year 2017	4,700,000
Estimated amortization expense in years 2018 through 2028	13,400,000
Other intangible assets	17,200,000		16,800,000
Accumulated computer software amortization	16,000,000		15,500,000
Amortization of computer software																$ 500,000	$ 600,000	$ 500,000

[1] Applies to all intangible assets, except for trademarks and trade names totaling $5.2 million, which have indefinite useful lives and, as such, are not being amortized.