Summary of Significant Accounting Policies Earnings Per Share (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended											12 Months Ended
	Jan. 31, 2016	[1]	Oct. 31, 2015	Jul. 31, 2015	[2]	Apr. 30, 2015	Jan. 31, 2015	Oct. 31, 2014	[3]	Jul. 31, 2014	Apr. 30, 2014	Jan. 31, 2016	Jan. 31, 2015	Jan. 31, 2014
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount												0.8	0.3	0.4
Net earnings	$ 163.2		$ 91.0	$ 104.9		$ 104.9	$ 196.2	$ 38.3		$ 124.1	$ 125.6	$ 463.9	$ 484.2	$ 181.4
Basic												128.6	129.2	127.8
Incremental shares based upon the assumed exercise of stock options and unvested restricted stock units												0.5	0.7	1.1
Weighted Average Number of Shares Outstanding, Diluted												129.1	129.9	128.9

[1] 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").

[2] 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").

[3] On a pre-tax basis, includes a charge of $93.8 million for the quarter ended October 31, which reduced net earnings per diluted share by $0.47, associated with the redemption of $400.0 million in aggregate principal amount of the Private Placement Notes prior to their scheduled maturities (see "Note G - Debt").