Stock-based Compensation (Tables)

12 Months Ended

Sep. 30, 2020

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Fair Values of Options, Black-Scholes Option-Pricing Model, Weighted-Average Assumptions

The fair values of the options granted for the year ended September 30, 2020 were estimated on the dates of grants using the Black-Scholes option-pricing model with the following weighted-average assumptions:

	Year Ended September 30,
	2020			2019			2018
Risk-free interest rate		1.61	%		2.86	%		2.10	%
Expected volatility		34.26	%		29.68	%		26.43	%
Expected life (in years)		5.26			5.22			5.46
Dividend yield		—			—			—

Stock Options Outstanding and Activity During the Period

The following table summarizes all stock option activity for the periods presented (in millions, except per share and time period amounts):

	Options Outstanding			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value1
Balance as of September 30, 2019		2.3		$	32.61		6.1	$	12.0
Granted		0.5			31.95
Exercised		(0.2	)		19.51
Canceled/Forfeited		(0.1	)		37.30
Expired		—			31.68
Balance as of September 30, 2020		2.5		$	33.09		5.9	$	6.9
Vested and expected to vest after September 30, 2020		2.4		$	33.13		5.9	$	6.8
Exercisable as of September 30, 2020		1.6		$	33.69		4.5	$	5.1

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¹ Aggregate intrinsic value as represents the difference between the closing fair value of the underlying common stock and the exercise price of outstanding, in-the-money options on the date of measurement.

Stock Option Grants, Vesting, and Exercises

The following table summarizes additional information on stock options for the periods presented (in millions, except per share amounts):

	Year Ended September 30,
	2020		2019		2018
Weighted-average fair value of stock options granted	$	10.35	$	8.91	$	15.86
Total grant date fair value of stock options vested	$	4.3	$	3.9	$	4.2
Total intrinsic value of stock options exercised	$	2.1	$	2.8	$	9.6

Restricted Shares and Units Outstanding and Activity During the Period

The following table summarizes all restricted stock unit activity for the periods presented (in millions, except per share amounts):

	RSUs Outstanding			Weighted-Average Grant Date Fair Value
Balance as of September 30, 2019		1.1		$	37.48
Granted		0.5			31.81
Released		(0.3	)		44.87
Canceled/Forfeited		(0.1	)		33.69
Balance as of September 30, 2020		1.2		$	33.55
Vested and expected to vest after September 30, 2020		1.0		$	34.68

Schedule Of Restricted Stock Units Additional Information

The following table summarizes additional information on RSUs for the period presented (in millions, except per share amounts):

	Year Ended September 30,
	2020		2019		2018
Weighted-average fair value of RSUs granted	$	31.81	$	28.02	$	57.40
Total grant date fair value of RSUs vested	$	14.4	$	16.1	$	6.7
Total intrinsic value of RSUs released	$	9.8	$	11.5	$	11.0