Stock-Based Compensation (Options and Common Shares Reserved for Grant) (Details) - Stock Options $ / shares in Units, shares in Thousands, $ in Thousands	6 Months Ended
	Mar. 31, 2021 USD ($) $ / shares shares
Options Outstanding [Roll Forward]
Options Outstanding, Beginning Balance (in shares) | shares	3,393
Options Outstanding, Granted (in shares) | shares	455
Options Outstanding, Exercised (in shares) | shares	(588)
Options Outstanding, Forfeited / Canceled (in shares) | shares	(129)
Options Outstanding, Ending Balance (in shares) | shares	3,131
Options Outstanding, Exercisable (in shares) | shares	1,878
Weighted Average Exercise Price [Roll Forward]
Weighted Average Exercise Price, Beginning Balance	$ 12.20
Weighted Average Exercise Price, Granted	17.59
Weighted Average Exercise Price, Exercised	11.26
Weighted Average Exercise Price, Forfeited / Canceled	13.98
Weighted Average Exercise Price, Ending Balance	13.09
Weighted Average Exercise Price, Exercisable	$ 11.40
Weighted Average Remaining Contractual Term [Abstract]
Weighted Average Remaining Contractual Term, Outstanding	4 years 1 month 6 days
Weighted Average Remaining Contractual Term, Exercisable	3 years
Aggregate Intrinsic Value, Outstanding | $	$ 18,714	[1]
Aggregate Intrinsic Value, Exercisable | $	$ 14,248	[1]
Closing Stock Price	$ 18.99

[1] The aggregate intrinsic value represents the total pre-tax intrinsic value, based on our closing stock price of $18.99 as of March 31, 2021, which would have been received by the option holders had all option holders exercised their options as of that date. The intrinsic value of an option is the amount by which the fair value of the underlying stock exceeds its exercise price.