Consolidated Statements of Financial Position (Parenthetical) - $ / shares	Sep. 30, 2020	Sep. 30, 2019
Shareholders' equity
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	200,000,000.0	200,000,000.0
Common stock, shares issued (in shares)	53,800,000	53,600,000
Treasury stock, shares (in shares)	10,700,000	4,800,000