Industry Segment and Geographic Data (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014 Customer Segment	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Number of reportable operating segments									2
Financial information for reportable segment [Abstract]
Net sales									$ 980,392	$ 983,704	$ 948,916
Depreciation and amortization									17,295	17,595	16,466
Operating income (loss)									85,338	86,863	71,431
Investment in equity affiliates	20,004				6,308				20,004	6,308	0
Capital expenditures	13,904				11,410				13,904	11,410	11,811
Total assets	673,551				615,523				673,551	615,523	576,594
Reconciliation of segment operating income to net earnings [Abstract]
Operating income									85,338	86,863	71,431
Other non-operating income (expense)									(1,969)	1	(696)
Interest expense									1,616	1,902	2,788
Earnings from continuing operations before taxes									81,753	84,962	67,947
Income tax expense									28,854	31,919	24,978
Earnings from continuing operations	11,517	17,806	11,169	12,407	9,391	17,686	16,400	9,566	52,899	53,043	42,969
Discontinued operations, net of tax	(419)	(8,240)	(529)	(682)	(455)	(389)	(357)	(392)	(9,870)	(1,593)	(1,616)
Net earnings	11,098	9,566	10,640	11,725	8,936	17,297	16,043	9,174	43,029	51,450	41,353
Revenues [Abstract]
Revenues	218,054	257,046	272,540	232,752	218,708	264,162	270,126	230,708	980,392	983,704	948,916
Long-lived assets [Abstract]
Long-lived assets	192,578				159,167				192,578	159,167	146,956
Number of largest individual customers									5
Net sales by major customer (in hundredths)									68.00%	66.00%	64.00%
Five Largest Individual Customers [Member]
Long-lived assets [Abstract]
Net sales by major customer (in hundredths)									68.00%	66.00%	64.00%
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)									16.00%
O' Reilly Automotive, Inc. [Member]
Long-lived assets [Abstract]
Net sales by major customer (in hundredths)									19.00%
AutoZone, Inc [Member]
Long-lived assets [Abstract]
Net sales by major customer (in hundredths)									10.00%
United States [Member]
Revenues [Abstract]
Revenues									871,665	884,380	865,861
Long-lived assets [Abstract]
Long-lived assets	158,350				135,834				158,350	135,834	137,240
Canada [Member]
Revenues [Abstract]
Revenues									53,412	51,853	50,215
Long-lived assets [Abstract]
Long-lived assets	1,546				1,526				1,546	1,526	1,658
Europe [Member]
Revenues [Abstract]
Revenues									13,299	10,657	8,093
Long-lived assets [Abstract]
Long-lived assets	11,725				11,310				11,725	11,310	4,161
Other Foreign [Member]
Revenues [Abstract]
Revenues									42,016	36,814	24,747
Long-lived assets [Abstract]
Long-lived assets	20,957				10,497				20,957	10,497	3,897
Intersegment Eliminations [Member]
Financial information for reportable segment [Abstract]
Net sales									0	0	0
Engine Management [Member] | Reportable Segments [Member]
Financial information for reportable segment [Abstract]
Net sales									709,263	711,245	665,105
Depreciation and amortization									12,425	13,235	13,093
Operating income (loss)									103,861	96,335	69,578
Investment in equity affiliates	6,368				6,308				6,368	6,308	0
Capital expenditures	11,182				8,628				11,182	8,628	8,941
Total assets	409,275				384,712				409,275	384,712	362,824
Reconciliation of segment operating income to net earnings [Abstract]
Operating income									103,861	96,335	69,578
Engine Management [Member] | Intersegment Eliminations [Member]
Financial information for reportable segment [Abstract]
Net sales									23,633	25,720	18,234
Temperature Control [Member] | Reportable Segments [Member]
Financial information for reportable segment [Abstract]
Net sales									259,065	262,537	268,804
Depreciation and amortization									4,171	3,763	2,924
Operating income (loss)									6,445	9,147	15,019
Investment in equity affiliates	13,636				0				13,636	0	0
Capital expenditures	2,650				2,682				2,650	2,682	2,005
Total assets	173,070				150,280				173,070	150,280	132,644
Reconciliation of segment operating income to net earnings [Abstract]
Operating income									6,445	9,147	15,019
Temperature Control [Member] | Intersegment Eliminations [Member]
Financial information for reportable segment [Abstract]
Net sales									6,966	6,329	4,804
Other [Member] | Reportable Segments [Member]
Financial information for reportable segment [Abstract]
Net sales									12,064	9,922	15,007
Depreciation and amortization									699	597	449
Operating income (loss)									(24,968)	(18,619)	(13,166)
Investment in equity affiliates	0				0				0	0	0
Capital expenditures	72				100				72	100	865
Total assets	91,206				80,531				91,206	80,531	81,126
Reconciliation of segment operating income to net earnings [Abstract]
Operating income									(24,968)	(18,619)	(13,166)
Other [Member] | Intersegment Eliminations [Member]
Financial information for reportable segment [Abstract]
Net sales									$ (30,599)	$ (32,049)	$ (23,038)