Segment Information (Details) - USD ($) $ in Thousands		3 Months Ended							6 Months Ended				12 Months Ended
		Jul. 31, 2018		Jan. 31, 2018	Oct. 31, 2017	Jul. 31, 2017		Apr. 30, 2017	Jul. 31, 2018		Jul. 31, 2017		Jan. 31, 2018
Segment Reporting Information
Revenues		$ 8,886,101		$ 10,033,397	$ 8,448,471	$ 8,092,353		$ 7,023,620	$ 17,434,420		$ 15,115,973		$ 33,597,841
Operating income:		110,365				103,531			180,861		178,609
Stock-based compensation expense		(7,968)				(7,974)			(15,555)		(12,892)
Depreciation and amortization:		39,918				38,890			80,399		70,573
Capital expenditures:		14,268				11,367			22,723		41,813
Identifiable assets:		11,833,316		12,920,359					11,833,316				12,920,359
Long-lived assets:		268,137		279,091					268,137				279,091
Goodwill & acquisition-related intangible assets, net:		1,823,490		1,914,500					1,823,490				1,914,500
Legal settlements and other, net		(5,234)				(28,655)			(8,199)		(41,343)
Acquisition, integration and restructuring expenses		13,297				30,117			46,522		72,183
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal		6,717				0			6,717		0
Americas
Segment Reporting Information
Revenues	[1]	4,043,331				3,769,696			7,661,537		6,905,018
Operating income:		87,930	[2]			87,975	[2]		149,272	[3]	138,875	[3]
Depreciation and amortization:		$ 23,591				$ 20,971			$ 46,850		$ 37,663
Sales to unaffiliated customers, as percentage of total sales	[1]	91.00%				90.00%			89.00%		89.00%
Capital expenditures:		$ 8,233				$ 7,087			$ 12,612		$ 27,959
Identifiable assets:		5,186,581		5,014,409					5,186,581				5,014,409
Long-lived assets:		209,351		214,922					209,351				214,922
Goodwill & acquisition-related intangible assets, net:		$ 1,109,835		$ 1,139,273					$ 1,109,835				$ 1,139,273
Long-lived assets, as percentage of total assets		97.00%		97.00%					97.00%				97.00%
Legal settlements and other, net		$ (5,200)				(30,000)			$ (8,200)		(42,600)
Acquisition, integration and restructuring expenses		(900)				14,300			13,100		44,400
Europe
Segment Reporting Information
Revenues		4,549,127				4,043,110			9,210,829		7,750,375
Operating income:	[5]	29,085	[4]			18,464			46,403	[4]	43,263
Depreciation and amortization:		14,016				15,690			29,007		29,223
Capital expenditures:		5,362				2,920			9,079		12,314
Identifiable assets:		6,046,378		$ 7,336,974					6,046,378				$ 7,336,974
Long-lived assets:		53,693		57,781					53,693				57,781
Goodwill & acquisition-related intangible assets, net:		600,331		645,134					600,331				645,134
Acquisition, integration and restructuring expenses		13,300				14,700			31,300		26,200
Asia-Pacific
Segment Reporting Information
Revenues		293,643				279,547			562,054		460,580
Operating income:		1,318				5,066			741		9,363
Depreciation and amortization:		2,311				2,229			4,542		3,687
Capital expenditures:		673				$ 1,360			1,032		$ 1,540
Identifiable assets:		600,357		568,976					600,357				568,976
Long-lived assets:		5,093		6,388					5,093				6,388
Goodwill & acquisition-related intangible assets, net:		$ 113,324		$ 130,093					$ 113,324				$ 130,093

[1] Net sales in the United States represented 91% and 90%, respectively, of the total Americas' net sales for the three months ended July 31, 2018 and 2017, and 89% of the total Americas' net sales for both the six months ended July 31, 2018 and 2017. Total long-lived assets in the United States represented 97% of the Americas' total long-lived assets at both July 31, 2018 and January 31, 2018.

[2] Operating income in the Americas for the three months ended July 31, 2018 and 2017 includes acquisition, integration and restructuring expenses of $(0.9) million and $14.3 million, respectively (see further discussion in Note 5 – Acquisition, Integration and Restructuring Expenses) and a gain related to legal settlements and other, net, of $5.2 million and $30.0 million, respectively (see further discussion in Note 1 - Business and Summary of Significant Accounting Policies).

[3] Operating income in the Americas for the six months ended July 31, 2018 and 2017 includes acquisition, integration and restructuring expenses of $13.1 million and $44.4 million, respectively and a gain related to legal settlements and other, net, of $8.2 million and $42.6 million, respectively.

[4] Operating income in Europe for the three and six months ended July 31, 2018 includes a gain on disposal of a subsidiary of $6.7 million (see further discussion in Note 6 – Gain on Disposal of Subsidiary).

[5] Operating income in Europe for the three months ended July 31, 2018 and 2017 includes acquisition, integration and restructuring expenses of $13.3 million and $14.7 million, respectively. Operating income in Europe for the six months ended July 31, 2018 and 2017, includes acquisition, integration and restructuring expenses of $31.3 million and $26.2 million, respectively.