Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended											12 Months Ended
	Jan. 31, 2017	[1]	Oct. 31, 2016	Jul. 31, 2016	Apr. 30, 2016	Jan. 31, 2016	[2]	Oct. 31, 2015	Jul. 31, 2015	[3]	Apr. 30, 2015	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Net sales	$ 1,229.6		$ 949.3	$ 931.6	$ 891.3	$ 1,213.6		$ 938.2	$ 990.5		$ 962.4	$ 4,001.8	$ 4,104.9	$ 4,249.9
Gross Profit	788.2		579.5	577.1	545.6	764.8		564.5	593.0		569.0	2,490.3	2,491.3	2,537.2
Earnings from operations	256.5		155.2	174.9	134.6	260.9		156.4	172.8		170.0	721.2	760.1	891.4
Net earnings	$ 157.8		$ 95.1	$ 105.7	$ 87.5	$ 163.2		$ 91.0	$ 104.9		$ 104.9	$ 446.1	$ 463.9	$ 484.2
Basic	$ 1.27		$ 0.76	$ 0.84	$ 0.69	$ 1.28		$ 0.71	$ 0.81		$ 0.81	$ 3.57	$ 3.61	$ 3.75
Diluted	$ 1.26		$ 0.76	$ 0.84	$ 0.69	$ 1.28		$ 0.70	$ 0.81		$ 0.81	$ 3.55	$ 3.59	$ 3.73

[1] On a pre-tax basis, includes charges for the quarter ended January 31, 2017 of:i.$25.4 million, which reduced net earnings per diluted share by $0.13, associated with an impairment charge related to software costs capitalized in connection with the development of a new finished goods inventory management and merchandising information system (see "Note B. Summary of Significant Accounting Policies" and "Note E. Property, Plant and Equipment"); andii.$12.6 million, which reduced net earnings per diluted share by $0.06, associated with impairment charges related to financing arrangements with diamond mining and exploration companies (see "Note B. Summary of Significant Accounting Policies" and "Note J. Commitments and Contingencies").

[2] On a pre-tax basis, includes charges for the quarter ended January 31, 2016 of: i.$28.3 million, which reduced net earnings per diluted share by $0.14, associated with an impairment charge related to a financing arrangement with Koidu Limited (see "Note B. Summary of Significant Accounting Policies" and "Note J. Commitments and Contingencies"); andii.$8.8 million, which reduced net earnings per diluted share by $0.04, associated with severance related to staffing reductions and subleasing of certain office space for which only a portion of the Company's future rent obligations will be recovered (see "Note J. Commitments and Contingencies").

[3] On a pre-tax basis, includes a charge of $9.6 million for the quarter ended July 31, 2015, which reduced net earnings per diluted share by $0.05, associated with an impairment charge related to a financing arrangement with Koidu Limited (see "Note B. Summary of Significant Accounting Policies" and "Note J. Commitments and Contingencies").