Borrowing Arrangements - Fair Value Notes (Details) - Senior Notes - USD ($)	Jul. 31, 2020	Jan. 31, 2020	Dec. 15, 2017	Jun. 30, 2017	Jun. 30, 2015	Dec. 31, 2012
2012 Senior Notes
Debt Instrument [Line Items]
Face amount	$ 350,000,000.0					$ 350,000,000.0
Fair value disclosure	369,600,000
Senior Notes due 2025
Debt Instrument [Line Items]
Face amount	300,000,000.0				$ 300,000,000.0
Fair value disclosure	342,100,000
2017 Senior Notes
Debt Instrument [Line Items]
Face amount	500,000,000.0		$ 400,000,000.0	$ 500,000,000.0
Fair value disclosure	577,200,000
2.85 Notes due January 15 2030
Debt Instrument [Line Items]
Face amount	500,000,000.0	$ 500,000,000.0
Fair value disclosure	$ 562,000,000.0