Earnings per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Earnings Per Share [Abstract]
Net Income (Loss) Attributable to Parent	$ 46.9	$ 49.5	$ 86.7	$ 91.7
Net income attributable to common shareholders per common share - Basic (usd per share)	$ 0.70	$ 0.74	$ 1.30	$ 1.37
Net income attributable to common shareholders per common share - Diluted (usd per share)	$ 0.70	$ 0.74	$ 1.29	$ 1.36
Average Common Shares Outstanding - Basic (in shares)	66,685	66,696	66,731	66,866
Add potential effect of exercise of stock options and other unvested equity awards (in shares)	533	648	578	659
Average shares outstanding - Diluted (in shares)	67,218	67,344	67,309	67,525
Shares with anti-dilutive effect excluded from the computation of Diluted EPS (in shares)	320	307	332	286