Share-Based Compensation (RSU Activity) (Details) shares in Thousands	6 Months Ended
	Mar. 31, 2021 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options exercisable (shares) | shares	3,857
Shares
Forfeited | shares	7
Weighted Average Grant Date Fair Value/Share
Weighted average grant date fair value, forfeited (in dollars per share) | $ / shares	$ 6.47
Weighted average exercise price, options vested and expected to vest (in dollars per share) | $ / shares	$ 13.25
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options exercisable (shares) | shares	948
Shares
Outstanding at beginning of the period (shares) | shares	750
Granted | shares	494
Vested in period (shares) | shares	(234)
Forfeited | shares	3
Outstanding at beginning of the period | shares	1,000
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	24.69
Weighted average grant date fair value, vested (in dollars per share) | $ / shares	17.64
Weighted average grant date fair value, forfeited (in dollars per share) | $ / shares	18.85
Weighted average grant date fair value, nonvested, equity instruments other than options, end of the period (in dollar per share) | $ / shares	21.26
Weighted average exercise price, options vested and expected to vest (in dollars per share) | $ / shares	$ 21.11
Cancelled (shares) | shares	(7)
Weighted average exercise price, cancelled (in dollars per share) | $ / shares	$ 21.22