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.