Stockholders' Equity - Additions to and Reclassifications out of Accumulated Other Comprehensive (Loss) Earnings (Details) - USD ($) $ in Millions	12 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other comprehensive earnings, net of tax	$ (42.4)	$ (68.6)	$ 118.2
Foreign currency translation adjustments
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Pre-tax gain recognized in OCI	(21.3)	(62.9)	97.9
Income tax (expense) benefit	(1.1)	2.7	(2.2)
Other comprehensive earnings, net of tax	(22.4)	(60.2)	95.7
Unrealized gain on marketable securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Pre-tax gain recognized in OCI	0.0	0.0	0.2
Income tax (expense) benefit	0.0	0.0	0.7
Reclassification of gain (loss)	0.0	0.0	(3.5)
Other comprehensive earnings, net of tax	0.0	0.0	(2.6)
Deferred hedging gain (loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Pre-tax gain recognized in OCI	50.5
Income tax (expense) benefit	(9.3)
Reclassification of gain (loss)	(6.5)
Other comprehensive earnings, net of tax	34.7
Deferred hedging gain (loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Pre-tax gain recognized in OCI		(1.1)	(21.0)
Income tax (expense) benefit		0.7	1.2
Reclassification of gain (loss)		(1.2)	13.0
Other comprehensive earnings, net of tax		(1.6)	(6.8)
Net actuarial (loss) gain
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification of gain (loss)	(82.0)	(24.2)	30.6
Net unrealized loss on benefit plans
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification of gain (loss)	11.2	15.1	13.3
Amortization of prior service credit included in net earnings
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification of gain (loss)	(0.5)	(0.6)	(0.5)
Accumulated defined benefit plans adjustment
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax (expense) benefit	16.6	2.9	(11.5)
Other comprehensive earnings, net of tax	$ (54.7)	$ (6.8)	$ 31.9