Industry Segment and Geographic Data (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013 Customer Segment	Dec. 31, 2012	Dec. 31, 2011
Segment Reporting Information [Line Items]
Number of reportable operating segments									2
Financial information for reportable segment [Abstract]
Net sales									$ 983,704	$ 948,916	$ 874,625
Depreciation and amortization									17,595	16,466	14,145
Operating income (loss)									86,863	71,431	64,899
Investment in equity affiliates	6,308				0				6,308	0	0
Capital expenditures	11,410				11,811				11,410	11,811	11,037
Total assets	615,523				576,594				615,523	576,594	550,722
Reconciliation of segment operating income to net earnings [Abstract]
Operating income									86,863	71,431	64,899
Other non-operating income (expense)									1	(696)	3,370
Interest expense									1,902	2,788	3,821
Earnings from continuing operations before taxes									84,962	67,947	64,448
Income tax expense									31,919	24,978	121
Earnings from continuing operations	9,391	17,686	16,400	9,566	6,310	17,444	13,721	5,494	53,043	42,969	64,327
Discontinued operations, net of tax	(455)	(389)	(357)	(392)	(395)	(604)	(317)	(300)	(1,593)	(1,616)	(1,926)
Net earnings	8,936	17,297	16,043	9,174	5,915	16,840	13,404	5,194	51,450	41,353	62,401
Revenues [Abstract]
Revenues	218,708	264,162	270,126	230,708	192,355	275,975	268,875	211,711	983,704	948,916	874,625
Long-lived assets [Abstract]
Long-lived assets	159,167				146,956				159,167	146,956	132,798
Number of largest individual customers									5
Net sales by major customer (in hundredths)									66.00%	64.00%	62.00%
Five Largest Individual Customers [Member]
Long-lived assets [Abstract]
Net sales by major customer (in hundredths)									66.00%	64.00%	62.00%
NAPA Auto Parts [Member]
Long-lived assets [Abstract]
Net sales by major customer (in hundredths)									19.00%
Advance Auto Parts, Inc. [Member]
Long-lived assets [Abstract]
Net sales by major customer (in hundredths)									15.00%
O' Reilly Automotive, Inc. [Member]
Long-lived assets [Abstract]
Net sales by major customer (in hundredths)									18.00%
United States [Member]
Revenues [Abstract]
Revenues									884,380	865,861	791,625
Long-lived assets [Abstract]
Long-lived assets	135,834				137,240				135,834	137,240	125,189
Canada [Member]
Revenues [Abstract]
Revenues									51,853	50,215	52,497
Long-lived assets [Abstract]
Long-lived assets	1,526				1,658				1,526	1,658	1,626
Europe [Member]
Revenues [Abstract]
Revenues									10,657	8,093	9,496
Long-lived assets [Abstract]
Long-lived assets	11,310				4,161				11,310	4,161	2,322
Other Foreign [Member]
Revenues [Abstract]
Revenues									36,814	24,747	21,007
Long-lived assets [Abstract]
Long-lived assets	10,497				3,897				10,497	3,897	3,661
Intersegment Eliminations [Member]
Financial information for reportable segment [Abstract]
Net sales									0	0	0
Engine Management [Member]
Financial information for reportable segment [Abstract]
Net sales									711,245	665,105	628,673
Depreciation and amortization									13,235	13,093	11,599
Operating income (loss)									96,335	69,578	56,261
Investment in equity affiliates	6,308				0				6,308	0	0
Capital expenditures	8,628				8,941				8,628	8,941	9,014
Total assets	384,712				362,824				384,712	362,824	372,410
Reconciliation of segment operating income to net earnings [Abstract]
Operating income									96,335	69,578	56,261
Engine Management [Member] | Intersegment Eliminations [Member]
Financial information for reportable segment [Abstract]
Net sales									25,720	18,234	21,175
Temperature Control [Member]
Financial information for reportable segment [Abstract]
Net sales									262,537	268,804	233,723
Depreciation and amortization									3,763	2,924	1,772
Operating income (loss)									9,147	15,019	17,699
Investment in equity affiliates	0				0				0	0	0
Capital expenditures	2,682				2,005				2,682	2,005	1,949
Total assets	150,280				132,644				150,280	132,644	97,656
Reconciliation of segment operating income to net earnings [Abstract]
Operating income									9,147	15,019	17,699
Temperature Control [Member] | Intersegment Eliminations [Member]
Financial information for reportable segment [Abstract]
Net sales									6,329	4,804	5,041
Other [Member]
Financial information for reportable segment [Abstract]
Net sales									9,922	15,007	12,229
Depreciation and amortization									597	449	774
Operating income (loss)									(18,619)	(13,166)	(9,061)
Investment in equity affiliates	0				0				0	0	0
Capital expenditures	100				865				100	865	74
Total assets	80,531				81,126				80,531	81,126	80,656
Reconciliation of segment operating income to net earnings [Abstract]
Operating income									(18,619)	(13,166)	(9,061)
Other [Member] | Intersegment Eliminations [Member]
Financial information for reportable segment [Abstract]
Net sales									$ (32,049)	$ (23,038)	$ (26,216)