Stockholders' Equity - Additions to and Reclassifications out of Accumulated Other Comprehensive (Loss) Earnings (Details) - USD ($) $ in Millions		12 Months Ended
		Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
Equity [Abstract]
Foreign currency translation adjustments		$ 97.9	$ 8.3	$ (59.9)
Income tax (expense) benefit		(2.2)	(16.7)	0.9
Foreign currency translation adjustments		95.7	(8.4)	(59.0)
Unrealized gain (loss) on marketable securities		0.2	2.7	(4.1)
Reclassification for gain included in net earnings a	[1]	(3.5)	0.0	(0.4)
Income tax benefit (expense)		0.7	(0.9)	1.6
Unrealized (loss) gain on marketable securities		(2.6)	1.8	(2.9)
Unrealized (loss) gain on hedging instruments		(21.0)	12.1	(22.2)
Reclassification adjustment for loss (gain) included in net earnings b	[2]	13.0	4.9	(11.7)
Income tax benefit (expense)		1.2	(6.3)	12.5
Unrealized (loss) gain on hedging instruments		(6.8)	10.7	(21.4)
Net actuarial gain		30.6	14.1	122.5
Amortization of net loss included in net earnings	[3]	13.3	14.7	30.4
Amortization of prior service credit included in net earnings	[3]	(0.5)	(0.7)	(0.6)
Income tax expense		(11.5)	(10.3)	(56.6)
Unrealized gain on benefit plans		31.9	17.8	95.7
Other comprehensive earnings, net of tax		$ 118.2	$ 21.9	$ 12.4

[1] These gains are reclassified into Other (income) expense, net.

[2] These losses (gains) are reclassified into Interest expense and financing costs and Cost of sales (see "Note H. Hedging Instruments" for additional details).

[3] These losses (gains) are included in the computation of net periodic pension costs (see "Note N. Employee Benefit Plans" for additional details).