Consolidated Statement Of Stockholders' Equity - 9 months ended Jun. 30, 2017 - USD ($) $ in Millions	Total	Common stock	Additional paid-in capital	Accumulated deficit	Accumulated other comprehensive income (loss)	Noncontrolling Interest [Member]
Balance at Sep. 30, 2016	$ 419.5	$ 1.6	$ 1,563.9	$ (1,078.9)	$ (68.3)	$ 1.2
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss) Attributable to Parent	104.0	0.0	0.0		0.0
Net Income (Loss) Attributable to Noncontrolling Interest						(0.1)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	103.9
Dividends declared	(17.6)	0.0	(17.6)	0.0	0.0	0.0
Stock repurchased under buyback program	55.0	0.0	55.0	0.0	0.0	0.0
Shares retained for employee taxes	(2.7)	0.0		0.0	0.0	0.0
Stock-based compensation	3.7	0.0	3.7	0.0	0.0	0.0
Stock issued under stock compensation plans	5.2	0.0	5.2	0.0	0.0	0.0
Other Comprehensive Income (Loss), Net of Tax	5.3	0.0	0.0	0.0	5.3	0.0
Balance at Jun. 30, 2017	$ 462.3	$ 1.6	$ 1,497.5	$ (974.9)	$ (63.0)	$ 1.1