Share-Based Compensation (RSU Activity) (Details) shares in Thousands	9 Months Ended
	Jun. 30, 2021 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options exercisable (shares) | shares	3,505
Shares
Forfeited | shares	42
Weighted Average Grant Date Fair Value/Share
Weighted average grant date fair value, forfeited (in dollars per share) | $ / shares	$ 6.73
Weighted average exercise price, options vested and expected to vest (in dollars per share) | $ / shares	$ 13.50
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options exercisable (shares) | shares	1,147
Shares
Outstanding at beginning of the period (shares) | shares	750
Granted | shares	729
Vested in period (shares) | shares	(239)
Forfeited | shares	23
Outstanding at beginning of the period | shares	1,210
Weighted Average Grant Date Fair Value/Share
Weighted average grant date fair value, nonvested, equity instruments other than options, beginning of the period (in dollar per share) | $ / shares	$ 17.86
Weighted average grant date fair value, granted (in dollars per share) | $ / shares	25.94
Weighted average grant date fair value, vested (in dollars per share) | $ / shares	17.55
Weighted average grant date fair value, forfeited (in dollars per share) | $ / shares	20.38
Weighted average grant date fair value, nonvested, equity instruments other than options, end of the period (in dollar per share) | $ / shares	22.72
Weighted average exercise price, options vested and expected to vest (in dollars per share) | $ / shares	$ 22.57
Cancelled (shares) | shares	(7)
Weighted average exercise price, cancelled (in dollars per share) | $ / shares	$ 21.22
Special RSU
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options exercisable (shares) | shares	422
Shares
Granted | shares	469
Outstanding at beginning of the period | shares	469
Weighted Average Grant Date Fair Value/Share
Weighted average grant date fair value, granted (in dollars per share) | $ / shares	$ 16.92
Weighted average grant date fair value, nonvested, equity instruments other than options, end of the period (in dollar per share) | $ / shares	16.92
Weighted average exercise price, options vested and expected to vest (in dollars per share) | $ / shares	$ 16.92