Income Taxes - Provision for Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Jan. 31, 2019	Oct. 31, 2018	Jul. 31, 2018	Apr. 30, 2018	Jan. 31, 2018	Oct. 31, 2017	Jul. 31, 2017	Apr. 30, 2017	Jan. 31, 2019	Jan. 31, 2018	Jan. 31, 2017
Federal:
Current									$ (13.3)	$ (0.8)	$ 1.6
Deferred									(6.7)	(19.3)	8.4
State:
Current									(1.8)	(0.3)	(1.9)
Deferred									0.1	2.2	1.3
Foreign:
Current									65.3	50.9	93.9
Deferred									(5.5)	(23.1)	(45.0)
Income tax expense	$ 31.7	$ 35.2	$ 16.0	$ 18.6	$ (24.8)	$ 8.6	$ 17.6	$ 8.2	$ 38.1	$ 9.6	$ 58.3