Segment Information (Details) - USD ($) $ in Thousands		3 Months Ended			6 Months Ended
		Jul. 31, 2019	Jul. 31, 2018		Jul. 31, 2019	Jul. 31, 2018		Jan. 31, 2019
Segment Reporting Information
Net sales		$ 9,092,244	$ 8,886,101		$ 17,498,668	$ 17,434,420
Operating income:		124,747	110,365		222,371	180,861
Stock-based compensation expense		(8,055)	(7,968)		(16,360)	(15,555)
Depreciation and amortization:		37,502	39,918		74,759	80,399
Capital expenditures:		18,231	14,268		33,510	22,723
Identifiable assets:		12,055,055			12,055,055			$ 12,986,552
Long-lived assets:		273,128			273,128			274,917
Goodwill & acquisition-related intangible assets, net:		1,657,770			1,657,770			1,719,629
Legal settlements and other, net		0	(5,234)		(282)	(8,199)
Acquisition, integration and restructuring expenses		5,209	13,297		11,430	46,522
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal		0	6,717		0	6,717
Americas
Segment Reporting Information
Net sales	[1]	4,316,731	4,043,331		8,105,929	7,661,537
Operating income:	[2],[3]	93,085	87,930		161,718	149,272
Depreciation and amortization:		$ 23,790	$ 23,591		$ 47,439	$ 46,850
Sales to unaffiliated customers, as percentage of total sales		91.00%	91.00%		90.00%	89.00%
Capital expenditures:		$ 10,526	$ 8,233		$ 18,798	$ 12,612
Identifiable assets:		5,569,530			5,569,530			5,402,316
Long-lived assets:	[1]	216,638			216,638			217,863
Goodwill & acquisition-related intangible assets, net:		$ 1,057,818			$ 1,057,818			$ 1,083,699
Long-lived assets, as percentage of total assets		96.00%			96.00%			96.00%
Restructuring Charges		$ 1,341			$ 4,252
Legal settlements and other, net			(5,200)		(300)	(8,200)
Acquisition, integration and restructuring expenses			(900)			13,100
Europe
Segment Reporting Information
Net sales		4,439,627	4,549,127		8,749,127	9,210,829
Operating income:	[4]	37,649	29,085	[5]	74,069	46,403	[5]
Depreciation and amortization:		12,021	14,016		23,531	29,007
Capital expenditures:		6,658	5,362		12,785	9,079
Identifiable assets:		5,870,713			5,870,713			$ 6,970,822
Long-lived assets:		51,310			51,310			52,162
Goodwill & acquisition-related intangible assets, net:		542,938			542,938			575,776
Restructuring Charges		3,229			6,300
Acquisition, integration and restructuring expenses			13,300			31,300
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal						6,700
Asia-Pacific
Segment Reporting Information
Net sales		335,886	293,643		643,612	562,054
Operating income:		2,068	1,318		2,944	741
Depreciation and amortization:		1,691	2,311		3,789	4,542
Capital expenditures:		1,047	$ 673		1,927	$ 1,032
Identifiable assets:		614,812			614,812			613,414
Long-lived assets:		5,180			5,180			4,892
Goodwill & acquisition-related intangible assets, net:		$ 57,014			$ 57,014			$ 60,154

[1] Net sales in the United States represented 91% of the total Americas' net sales for both the three months ended July 31, 2019 and 2018, and 90% and 89%, respectively, of the total Americas' net sales for the six months ended July 31, 2019 and 2018. Total long-lived assets in the United States represented 96% of the Americas' total long-lived assets at both July 31, 2019 and January 31, 2019.

[2] Operating income in the Americas includes a gain related to legal settlements and other, net, of $5.2 million for the three months ended July 31, 2018. Operating income in the Americas includes a gain related to legal settlements and other, net, of $0.3 million and $8.2 million for the six months ended July 31, 2019 and 2018, respectively (see further discussion in Note 1 - Business and Summary of Significant Accounting Policies).

[3] Operating income in the Americas for the three months ended July 31, 2019 and 2018 includes acquisition, integration and restructuring expenses of $1.3 million and $(0.9) million, respectively. Operating income in the Americas for the six months ended July 31, 2019 and 2018 includes acquisition, integration and restructuring expenses of $4.3 million and $13.1 million, respectively (see further discussion in Note 3 – Acquisition, Integration and Restructuring Expenses).

[4] Operating income in Europe for the three months ended July 31, 2019 and 2018 includes acquisition, integration and restructuring expenses of $3.2 million and $13.3 million, respectively. Operating income in Europe for the six months ended July 31, 2019 and 2018 includes acquisition, integration and restructuring expenses of $6.3 million and $31.3 million, respectively.

[5] 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 4 – Gain on Disposal of Subsidiary).