Summary of Significant Accounting Policies Earnings Per Share (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended										12 Months Ended
	Jan. 31, 2018	[1]	Oct. 31, 2017	Jul. 31, 2017	Apr. 30, 2017	Jan. 31, 2017	[2]	Oct. 31, 2016	Jul. 31, 2016	Apr. 30, 2016	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount											0.6	1.3	0.8
Net earnings	$ 61.9		$ 100.2	$ 115.0	$ 92.9	$ 157.8		$ 95.1	$ 105.7	$ 87.5	$ 370.1	$ 446.1	$ 463.9
Basic											124.5	125.1	128.6
Incremental shares based upon the assumed exercise of stock options and unvested restricted stock units											0.6	0.4	0.5
Weighted Average Number of Shares Outstanding, Diluted											125.1	125.5	129.1

[1] For the quarter ended January 31, 2018, includes net tax expense of $146.2 million, or $1.17 per diluted share, related to the estimated impact of the 2017 Tax Act (see "Note O. Income Taxes").

[2] 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").