Borrowing Arrangements Fair Value Notes (Details) - Senior Notes - USD ($)	Jan. 31, 2021	Jan. 31, 2020	Jun. 30, 2017	Jun. 30, 2015	Dec. 31, 2012
2012 Notes
Debt Instrument [Line Items]
Face amount	$ 350,000,000.0				$ 350,000,000.0
Fair value disclosure	366,300,000
$300 2015 Notes
Debt Instrument [Line Items]
Face amount	300,000,000.0			$ 300,000,000
Fair value disclosure	341,400,000
2017 Notes
Debt Instrument [Line Items]
Face amount	500,000,000.0		$ 500,000,000.0
Fair value disclosure	564,600,000
2020 Notes
Debt Instrument [Line Items]
Face amount	500,000,000.0	$ 500,000,000.0
Fair value disclosure	$ 542,700,000