Supplemental Cash Flow Information - Cash Paid (Details) - USD ($) $ in Millions	12 Months Ended
	Jan. 31, 2019	Jan. 31, 2018	Jan. 31, 2017
Supplemental Cash Flow Information [Abstract]
Interest, net of interest capitalization	$ 40.6	$ 41.5	$ 40.6
Income taxes	$ 291.4	$ 156.2	$ 213.9