Segment Information (Details) - USD ($) $ in Thousands		3 Months Ended			9 Months Ended
		Oct. 31, 2019	Oct. 31, 2018		Oct. 31, 2019		Oct. 31, 2018		Jan. 31, 2019
Segment Reporting Information
Net sales		$ 9,118,944	$ 9,340,029		$ 26,617,612		$ 26,774,449
Operating income:		141,888	146,888		364,259		327,749
Stock-based compensation expense		(7,347)	(8,139)		(23,707)		(23,694)
Depreciation and amortization:		37,967	39,242		112,726		119,641
Capital expenditures:		18,140	17,430		51,650		40,153
Identifiable assets:		12,694,736			12,694,736				$ 12,986,552
Long-lived assets:		275,013			275,013				274,917
Goodwill & acquisition-related intangible assets, net:		1,646,747			1,646,747				1,719,629
Legal settlements and other, net		0	(7,207)		(282)		(15,406)
Acquisition, integration and restructuring expenses		4,647	20,277		16,077		66,799
Other Tax Expense (Benefit)			5,500		600		6,100
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal		1,390	29		1,390		6,746
Americas
Segment Reporting Information
Net sales	[1]	4,202,320	4,137,852		12,308,249		11,799,389
Operating income:	[2]	82,420	112,399	[3],[4]	244,138	[4]	261,671	[3],[4]
Depreciation and amortization:		$ 24,163	$ 23,394		$ 71,602		$ 70,244
Sales to unaffiliated customers, as percentage of total sales		91.00%	91.00%		90.00%		90.00%
Capital expenditures:		$ 11,191	$ 11,493		$ 29,989		$ 24,105
Identifiable assets:		5,670,555			5,670,555				5,402,316
Long-lived assets:	[1]	219,300			219,300				217,863
Goodwill & acquisition-related intangible assets, net:		$ 1,045,627			$ 1,045,627				$ 1,083,699
Long-lived assets, as percentage of total assets		96.00%			96.00%				96.00%
Restructuring Charges		$ 3,500			$ 7,800
Legal settlements and other, net			(7,200)		(300)		(15,400)
Acquisition, integration and restructuring expenses			6,000				19,000
Proceeds, Accounts Receivable, Previously Written Off, Recovery			25,000				25,000
Europe
Segment Reporting Information
Net sales		4,622,270	4,920,156		13,371,397		14,130,985
Operating income:	[5],[6],[7]	66,536	39,889		140,605		86,292
Depreciation and amortization:		11,763	13,679		35,294		42,686
Capital expenditures:		6,373	4,742		19,158		13,821
Identifiable assets:		6,420,274			6,420,274				$ 6,970,822
Long-lived assets:		51,051			51,051				52,162
Goodwill & acquisition-related intangible assets, net:		545,625			545,625				575,776
Restructuring Charges		1,000			7,200
Acquisition, integration and restructuring expenses			13,100				44,400
Other Tax Expense (Benefit)			5,500				6,500
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal		1,400			1,400		6,700
Asia-Pacific
Segment Reporting Information
Net sales		294,354	282,021		937,966		844,075
Operating income:		279	2,739		3,223		3,480
Depreciation and amortization:		2,041	2,169		5,830		6,711
Capital expenditures:		576	$ 1,195		2,503		$ 2,227
Identifiable assets:		603,907			603,907				613,414
Long-lived assets:		4,662			4,662				4,892
Goodwill & acquisition-related intangible assets, net:		$ 55,495			$ 55,495				$ 60,154

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

[2] Operating income in the Americas for the three months ended October 31, 2019 and 2018 includes acquisition, integration and restructuring expenses of $3.5 million and $6.0 million, respectively. Operating income in the Americas for the nine months ended October 31, 2019 and 2018 includes acquisition, integration and restructuring expenses of $7.8 million and $19.0 million, respectively (see further discussion in Note 3 – Acquisition, Integration and Restructuring Expenses).

[3] Operating income in the Americas for the three and nine months ended October 31, 2018 includes a benefit of approximately $25 million related to the collection of an accounts receivable balance previously considered uncollectible.

[4] Operating income in the Americas includes a gain related to legal settlements and other, net, of $7.2 million for the three months ended October 31, 2018. Operating income in the Americas includes a gain related to legal settlements and other, net, of $0.3 million and $15.4 million for the nine months ended October 31, 2019 and 2018, respectively (see further discussion in Note 1 – Business and Summary of Significant Accounting Policies).

[5] Operating income in Europe for both the three and nine months ended October 31, 2019 includes a gain on disposal of a subsidiary of $1.4 million. Operating income in Europe for the nine months ended October 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).

[6] Operating income in Europe for the three months ended October 31, 2019 and 2018 includes acquisition, integration and restructuring expenses of $1.0 million and $13.1 million, respectively. Operating income in Europe for the nine months ended October 31, 2019 and 2018 includes acquisition, integration and restructuring expenses of $7.2 million and $44.4 million, respectively.

[7] Operating income in Europe for the three and nine months ended October 31, 2018 includes expenses of $5.5 million and $6.5 million, respectively, related to the recognition of certain tax indemnification liabilities (see further discussion in Note 6 – Income Taxes).