Borrowing Arrangements - Fair Value Notes (Details) - Senior Notes - USD ($)	Apr. 30, 2021	Jan. 31, 2020	Jun. 30, 2015	Dec. 31, 2012
2012 Notes
Debt Instrument [Line Items]
Aggregate Principal Amount	$ 350,000,000.0			$ 350,000,000.0
Fair value	364,600,000
2015 Notes
Debt Instrument [Line Items]
Aggregate Principal Amount	300,000,000.0		$ 300,000,000.0
Fair value	335,700,000
2017 Notes
Debt Instrument [Line Items]
Aggregate Principal Amount	500,000,000.0
Fair value	551,300,000
2020 Notes
Debt Instrument [Line Items]
Aggregate Principal Amount	500,000,000.0	$ 500,000,000.0
Fair value	$ 522,300,000