Acquisitions and Equity Investments - Additional Information (Detail) $ / shares in Units, employee in Thousands, Store in Thousands, $ in Thousands			2 Months Ended	12 Months Ended
	Nov. 02, 2017 USD ($) Store employee	Apr. 03, 2017 USD ($) Location	Dec. 31, 2017 USD ($) $ / shares	Dec. 31, 2017 USD ($) Location Business $ / shares	Dec. 31, 2016 USD ($) Business $ / shares	Dec. 31, 2015 USD ($) Business $ / shares	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Business Acquisition [Line Items]
Cash paid for acquisition				$ 1,457,000	$ 420,000	$ 140,000
Company acquired | Business				15
Net sales				$ 16,308,801	15,339,713	15,280,044	$ 15,341,647	$ 14,077,843
Goodwill and other intangible assets acquired				1,926,000
Payment for debt extinguishment or debt prepayment cost				833,775	0	$ 0
Finite-lived intangible assets acquired				$ 796,544	$ 139,982
Diluted net income per common share (in dollars per share) | $ / shares				$ 4.18	$ 4.59	$ 4.63
United States [Member]
Business Acquisition [Line Items]
Net sales				$ 13,293,325	$ 12,822,320	$ 12,843,078	12,565,329	11,594,713
Canada [Member]
Business Acquisition [Line Items]
Net sales				$ 1,549,915	1,390,979	1,395,695	$ 1,583,075	$ 1,560,799
Automotive
Business Acquisition [Line Items]
Company acquired | Business				12
Automotive | Australia [Member]
Business Acquisition [Line Items]
Number of locations | Location				3
Industrial
Business Acquisition [Line Items]
Company acquired | Business				2
Electrical/ Electronic Materials
Business Acquisition [Line Items]
Company acquired | Business				1
2016 Companies Acquired [Member]
Business Acquisition [Line Items]
Cash paid for acquisition				$ 1,334,000	$ 370,000
Company acquired | Business					19
Goodwill and other intangible assets acquired					$ 260,000
2016 Companies Acquired [Member] | Customer relationships
Business Acquisition [Line Items]
Other intangible assets acquired					$ 112,000
Weighted average amortization lives (in years)					17 years
2016 Companies Acquired [Member] | Trademarks
Business Acquisition [Line Items]
Other intangible assets acquired					$ 28,000
Weighted average amortization lives (in years)					35 years
2016 Companies Acquired [Member] | Automotive
Business Acquisition [Line Items]
Company acquired | Business					11
2016 Companies Acquired [Member] | Industrial
Business Acquisition [Line Items]
Company acquired | Business					5
2016 Companies Acquired [Member] | Electrical/ Electronic Materials
Business Acquisition [Line Items]
Company acquired | Business					1
2016 Companies Acquired [Member] | Business Products
Business Acquisition [Line Items]
Company acquired | Business					2
2017 Companies Acquired [Member] | Automotive
Business Acquisition [Line Items]
Company acquired | Business				12
Net sales				$ 1,900,000
Standard Motor Parts [Member] | Automotive | United States [Member]
Business Acquisition [Line Items]
Number of locations | Location				5
Olympic Brake Supply [Member] | Automotive | United States [Member]
Business Acquisition [Line Items]
Number of locations | Location				6
Merle's Automotive Supply [Member] | Automotive | United States [Member]
Business Acquisition [Line Items]
Number of locations | Location				14
Monroe Motor Products [Member] | Automotive | United States [Member]
Business Acquisition [Line Items]
Number of locations | Location				17
Stone Truck Parts [Member] | Automotive | United States [Member]
Business Acquisition [Line Items]
Number of locations | Location				4
Service de Freins Montreal Ltee [Member] | Automotive | Canada [Member]
Business Acquisition [Line Items]
Number of locations | Location				4
Belcher Parts and Attachments [Member] | Automotive | Canada [Member]
Business Acquisition [Line Items]
Number of locations | Location				1
Universal Supply Group [Member] | Automotive | Canada [Member]
Business Acquisition [Line Items]
Number of locations | Location				21
2017 Acquisitions [Member]
Business Acquisition [Line Items]
Company acquired | Business				15
Net sales				$ 429,000
2017 Acquisitions [Member] | Customer relationships
Business Acquisition [Line Items]
Other intangible assets acquired			$ 619,000	$ 619,000
Weighted average amortization lives (in years)				19 years
2017 Acquisitions [Member] | Trademarks
Business Acquisition [Line Items]
Other intangible assets acquired			176,000	$ 176,000
Weighted average amortization lives (in years)				27 years
2017 Acquisitions [Member] | Other Intangible Assets
Business Acquisition [Line Items]
Other intangible assets acquired			1,000	$ 1,000
Weighted average amortization lives (in years)				2 years
2017 Acquisitions [Member] | Industrial
Business Acquisition [Line Items]
Company acquired | Business				2
Net sales				$ 118,000
2017 Acquisitions [Member] | Electrical/ Electronic Materials
Business Acquisition [Line Items]
Net sales				$ 65,000
Apache Hose & Belting Company, Inc. [Member] | Industrial
Business Acquisition [Line Items]
Number of locations | Location				7
Empire Wire and Supply [Member] | Electrical/ Electronic Materials
Business Acquisition [Line Items]
Number of locations | Location				3
Alliance Automotive Group [Member]
Business Acquisition [Line Items]
Cash paid for acquisition	$ 1,080,000
Net sales			$ 256,400
Weighted average amortization lives (in years)	19 years
Cash acquired from acquisition	$ 109,000
Number of employees in acquired entity | employee	8
Number of stores of acquired entity | Store	2
Revenue reported by acquired entity for last annual period				$ 1,700,000
Payment for debt extinguishment or debt prepayment cost	$ 825,000
Intangible assets	727,000
Diluted net income per common share (in dollars per share) | $ / shares			$ 0.07
Pro forma revenue				$ 17,627,000	$ 16,575,000
Pro forma earnings per share, diluted (in dollars per share) | $ / shares				$ 4.56	$ 4.55
Alliance Automotive Group [Member] | Customer relationships
Business Acquisition [Line Items]
Finite-lived intangible assets acquired	550,000
Alliance Automotive Group [Member] | Trademarks
Business Acquisition [Line Items]
Finite-lived intangible assets acquired	$ 176,000
Alliance Automotive Group [Member] | Trademarks | Minimum [Member]
Business Acquisition [Line Items]
Weighted average amortization lives (in years)	27 years
Alliance Automotive Group [Member] | Trademarks | Maximum [Member]
Business Acquisition [Line Items]
Weighted average amortization lives (in years)	2 years
Alliance Automotive Group [Member] | Other Intangible Assets
Business Acquisition [Line Items]
Weighted average amortization lives (in years)	21 years
Finite-lived intangible assets acquired	$ 1,000
Inenco Group [Member]
Business Acquisition [Line Items]
Revenue reported by acquired entity for last annual period		$ 325,000
Percentage of voting interests acquired		35.00%
Payments to acquire equity method investments		$ 72,100
Number of locations of acquired entity | Location		161
Percentage of voting interests with option to be acquired		65.00%
2015 Companies Acquired [Member]
Business Acquisition [Line Items]
Cash paid for acquisition						120,000
Goodwill and other intangible assets acquired						90,000
2015 Companies Acquired [Member] | Customer relationships
Business Acquisition [Line Items]
Other intangible assets acquired						$ 39,000
Weighted average amortization lives (in years)						15 years
2015 Companies Acquired [Member] | Automotive
Business Acquisition [Line Items]
Company acquired | Business						5
2015 Companies Acquired [Member] | Industrial
Business Acquisition [Line Items]
Company acquired | Business						4
2015 Companies Acquired [Member] | Electrical/ Electronic Materials
Business Acquisition [Line Items]
Company acquired | Business						1
2015 Companies Acquired [Member] | Business Products
Business Acquisition [Line Items]
Company acquired | Business						3