Segment Information - Company's Segments Information (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jul. 31, 2020	Jul. 31, 2019	Jul. 31, 2020	Jul. 31, 2019
Net sales:
Net sales		$ 747.1	$ 1,048.5	$ 1,302.6	$ 2,051.6
Earnings (losses) from operations:
Earnings from operations for segments	[1]	110.9	236.2	86.9	446.0
Americas
Net sales:
Net sales		246.7	454.8	471.8	861.1
Earnings (losses) from operations:
Earnings from operations for segments	[1]	(4.7)	86.9	(45.9)	143.8
Asia-Pacific
Net sales:
Net sales		298.9	297.6	472.6	621.7
Earnings (losses) from operations:
Earnings from operations for segments	[1]	72.7	73.2	88.6	159.2
Japan
Net sales:
Net sales		111.1	155.3	197.4	300.0
Earnings (losses) from operations:
Earnings from operations for segments	[1]	35.4	56.2	51.8	109.6
Europe
Net sales:
Net sales		83.8	116.3	145.1	218.8
Earnings (losses) from operations:
Earnings from operations for segments	[1]	12.6	19.7	2.6	31.9
Total reportable segments
Net sales:
Net sales		740.5	1,024.0	1,286.9	2,001.6
Earnings (losses) from operations:
Earnings from operations for segments	[1]	116.0	236.0	97.1	444.5
Other
Net sales:
Net sales		6.6	24.5	15.7	50.0
Earnings (losses) from operations:
Earnings from operations for segments	[1]	$ (5.1)	$ 0.2	$ (10.2)	$ 1.5

[1] Represents earnings (loss) from operations before (i) unallocated corporate expenses, (ii) Interest expense and financing costs, (iii) Other income, net