Business Combinations - Additional Information (Detail)	9 Months Ended		1 Months Ended			9 Months Ended									12 Months Ended
	Sep. 30, 2012 USD ($)	Dec. 31, 2011 USD ($)	Oct. 31, 2012 North America	Oct. 31, 2012 Wholesale North America Segment	Oct. 31, 2012 Canadian Aftermarket Product Distributors	Sep. 30, 2012 All 2012 Acquisitions USD ($)	Sep. 30, 2012 All 2012 Acquisitions North America	Sep. 30, 2012 All 2012 Acquisitions Wholesale North America Segment	Sep. 30, 2012 All 2012 Acquisitions Self Service Segment	Dec. 31, 2011 All 2011 Acquisitions USD ($)	Dec. 31, 2011 Euro Car Parts Holdings Limited USD ($)	Dec. 31, 2011 Euro Car Parts Holdings Limited GBP (£)	Dec. 31, 2011 2012 Contingent Payment GBP (£)	Dec. 31, 2011 2013 Contingent Payment GBP (£)	Dec. 31, 2011 All 2011 Acquisitions Excluding ECP USD ($)	Dec. 31, 2011 All 2011 Acquisitions Excluding ECP Wholesale North America Segment	Dec. 31, 2011 All 2011 Acquisitions Excluding ECP Heavy Duty Truck Segment	Dec. 31, 2011 All 2011 Acquisitions Excluding ECP Self Service Segment	Dec. 31, 2011 All 2011 Acquisitions Excluding ECP and Akzo USD ($)	Dec. 31, 2011 Engine Remanufacturers Wholesale North America Segment	Dec. 31, 2011 Akzo Nobel Wholesale North America Segment USD ($)
Business Acquisition
Number of acquisitions			5	4	2		13	8	5						20	12	5	3		2
Total acquisition date fair value of the consideration for acquisitions						$ 143,100,000					$ 403,700,000	£ 261,600,000			$ 207,300,000
Cash used in acquisitions, net of cash acquired						129,258,000				486,934,000	293,725,000	190,300,000			193,209,000
Notes issued						8,206,000				34,219,000	28,302,000	18,400,000			5,917,000
Other purchase price obligations						66,000				8,646,000	4,136,000	2,700,000			4,510,000
Acquisition fair value of contingent consideration						5,540,000				81,239,000	77,539,000	50,200,000			3,700,000
Minimum payment under contingent consideration agreement													22,000,000	23,000,000
Maximum payment under contingent consideration agreement						6,500,000							25,000,000	30,000,000					4,600,000		21,000,000
Goodwill	1,597,936,000	1,476,063,000				109,878,000				438,068,000	332,891,000				105,177,000
Goodwill recorded for acquisitions	105,738,000
Number of contingent consideration arrangements resulting from acquisitions																			2
Goodwill expected to be deductible for income tax purposes						85,200,000									88,300,000
Revenue generated by acquisitions						62,400,000
Operating income generated by acquisitions						$ 6,800,000