Segment Information (Details) - USD ($) $ in Thousands		3 Months Ended																12 Months Ended
		Jan. 31, 2019		Oct. 31, 2018		Jul. 31, 2018		Apr. 30, 2018		Jan. 31, 2018		Oct. 31, 2017		Jul. 31, 2017		Apr. 30, 2017		Jan. 31, 2019		Jan. 31, 2018	Jan. 31, 2017
Segment Reporting Information
Revenues		$ 10,464,501		$ 9,340,029		$ 8,886,101		$ 8,548,319		$ 10,033,397		$ 8,448,471		$ 8,092,353		$ 7,023,620		$ 37,238,950		$ 33,597,841	$ 24,193,697
Stock-based compensation expense																		(31,513)		(29,381)	(13,947)
Operating income (loss):		166,053	[1],[2]	146,888	[1],[3],[4]	110,365	[1],[3]	70,496	[1],[3]	151,903	[5]	79,567	[5]	103,531	[5],[6]	75,078	[5],[6]	493,802		410,079	291,902
Depreciation and amortization:																		158,997		150,046	54,437
Capital expenditures:																		61,414		231,937	39,335
Identifiable assets:		12,986,552								12,920,359								12,986,552		12,920,359
Long-lived assets:		274,917								279,091								274,917		279,091
Goodwill & acquisition-related intangible assets, net:		1,719,629								1,914,500								1,719,629		1,914,500
Business Combination, Acquisition Related Costs		21,100		20,300		13,300		33,200		34,300		$ 29,700		30,100		42,100		87,920		136,272	28,966
Allowance for Doubtful Accounts Receivable				25,000
Legal settlements and other, net				$ (7,200)		$ (5,200)		$ (3,000)						$ (28,700)		$ (12,700)		(15,406)		(41,343)	(4,142)
Value added tax assessments																		0		1,652	1,049
Gain on disposal of subsidiary																		6,746		0	0
Goodwill Impairment		47,434																47,434		0	0
Americas
Segment Reporting Information
Revenues	[7]																	16,041,103		14,419,221	9,525,513
Operating income (loss):	[8],[9]																	366,637		248,350	144,246
Depreciation and amortization:																		$ 93,612		$ 84,265	$ 18,844
U.S. Sales as Percentage of Total Americas Sales																		90.00%		89.00%	90.00%
Capital expenditures:																		$ 37,141		$ 207,399	$ 19,275
Identifiable assets:		5,402,316								5,014,409								5,402,316		5,014,409
Long-lived assets:		217,863								214,922								217,863		214,922
Goodwill & acquisition-related intangible assets, net:		$ 1,083,699								$ 1,139,273								$ 1,083,699		$ 1,139,273
Long-lived Assets, as Percentage of Total Assets		96.00%								97.00%								96.00%		97.00%
Business Combination, Acquisition Related Costs																		$ 25,200		$ 75,500	18,000
Allowance for Doubtful Accounts Receivable																		25,000
Legal settlements and other, net																		(15,400)		(42,600)	(4,100)
Goodwill Impairment																		0
Europe
Segment Reporting Information
Revenues																		20,026,057		18,147,917	14,668,184
Operating income (loss):	[10]																	195,375		173,611	161,603
Depreciation and amortization:																		56,533		57,794	35,593
Capital expenditures:																		20,818		21,471	20,060
Identifiable assets:		$ 6,970,822								$ 7,336,974								6,970,822		7,336,974
Long-lived assets:		52,162								57,781								52,162		57,781
Goodwill & acquisition-related intangible assets, net:		575,776								645,134								575,776		645,134
Business Combination, Acquisition Related Costs																		57,700		56,200	11,000
Gain on disposal of subsidiary																		6,746
Goodwill Impairment																		0
Asia Pacific [Member]
Segment Reporting Information
Revenues																		1,171,790		1,030,703	0
Operating income (loss):																		(36,697)	[11]	17,499	0
Depreciation and amortization:																		8,852		7,987	0
Capital expenditures:																		3,455		3,067	$ 0
Identifiable assets:		613,414								568,976								613,414		568,976
Long-lived assets:		4,892								6,388								4,892		6,388
Goodwill & acquisition-related intangible assets, net:		60,154								$ 130,093								60,154		$ 130,093
Goodwill Impairment		$ 47,434																$ 47,434

[1] During the first, second, third and fourth quarters of fiscal 2019, the Company recorded $33.2 million, $13.3 million, $20.3 million and $21.1 million of acquisition, integration and restructuring expenses, respectively (see Note 6 – Acquisition, Integration and Restructuring Expenses for further discussion).

[2] During the fourth quarter of fiscal 2019, the Company recorded goodwill impairment expense of $47.4 million (see Note 4 – Goodwill and Intangible Assets for further discussion).

[3] During the first, second and third quarters of fiscal 2019, the Company recorded a gain of $3.0 million, $5.2 million and $7.2 million, respectively, in legal settlements and other, net (see Note 1 - Business and Summary of Significant Accounting Policies for further discussion).

[4] During the third quarter of fiscal 2019, the Company included a $25 million benefit in operating income related to the collection of an accounts receivable balance previously considered uncollectible.

[5] During the first, second, third and fourth quarters of fiscal 2018, the Company recorded $42.1 million, $30.1 million, $29.7 million and $34.3 million of acquisition, integration and restructuring expenses, respectively.

[6] During the first and second quarters of fiscal 2018, the Company recorded a gain of $12.7 million and $28.7 million, respectively, in legal settlements and other, net.

[7] Net sales in the U.S. represented 90%, 89% and 90% of the total Americas' net sales for the fiscal years ended January 31, 2019, 2018 and 2017, respectively. Total long-lived assets in the U.S. represented 96% and 97% of the Americas' total long-lived assets at January 31, 2019 and 2018, respectively.

[8] Operating income in the Americas for the fiscal years ended January 31, 2019, 2018 and 2017 includes a gain recorded in legal settlements and other, net, of $15.4 million, $42.6 million and $4.1 million, respectively (see Note 1 – Business and Summary of Significant Accounting Policies for further discussion).

[9] Operating income in the Americas for the fiscal years ended January 31, 2019, 2018 and 2017 includes acquisition, integration and restructuring expenses of $25.2 million, $75.5 million and $18.0 million, respectively (see Note 6 – Acquisition, Integration and Restructuring Expenses for further discussion). Operating income in the Americas for the fiscal year ended January 31, 2019 includes a benefit of approximately $25 million related to the collection of an accounts receivable balance previously considered uncollectible.

[10] Operating income in Europe for the fiscal years ended January 31, 2019, 2018 and 2017 includes acquisition, integration and restructuring expenses of $57.7 million, $56.2 million and $11.0 million, respectively.

[11] Operating income in Asia-Pacific for the fiscal year ended January 31, 2019 includes goodwill impairment expense of $47.4 million (see Note 4 – Goodwill and Intangible Assets for further discussion).