Quarterly Financial Data (Unaudited) Text (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Tax Cuts and Jobs Act of 2017 Estimated Net Tax Expense	$ 146.2
Tax Cuts and Jobs Act of 2017 per share impact	$ 1.17
Asset impairment charges		$ 25.4	$ 10.0	$ 25.4	$ 0.0
Asset impairment charge per share impact		$ 0.13
Loan impairment charges		$ 12.6	$ 3.0	$ 12.6	$ 37.9
Loan impairment charges per share impact		$ 0.06