Stock-Based Compensation (Tables)

6 Months Ended

Mar. 31, 2018

Stock-Based Compensation

Summary of compensation cost for stock-based payment arrangements recognized in general and administrative expense

	Three Months Ended				Six Months Ended
	March 31,				March 31,
	2018		2017		2018		2017
	(in thousands)				(in thousands)
Compensation expense
Stock options	$	2,109	$	1,869	$	4,072	$	3,521
Restricted stock		6,350		4,709		11,474		8,958
	$	8,459	$	6,578	$	15,546	$	12,479

Summary of weighted-average assumptions utilized in determining the fair value of options granted

	2018		2017
Risk-free interest rate	2.2	%	2.0	%
Expected stock volatility	36.1	%	39.4	%
Dividend yield	4.8	%	3.4	%
Expected term (in years)	6.0		5.5

Summary of stock option activity

	Three Months Ended March 31, 2018
				Weighted
				Average
		Weighted		Remaining	Aggregate
		Average		Contractual	Intrinsic
	Shares	Exercise		Term	Value
	(in thousands)	Price		(in years)	(in millions)
Outstanding at January 1, 2018	3,755	$	57.82
Granted	7		71.57
Exercised	(41)		30.66
Outstanding at March 31, 2018	3,721	$	58.15	6.24	$	40.1
Vested and expected to vest at March 31, 2018	3,721	$	58.15	6.24	$	40.1
Exercisable at March 31, 2018	2,358	$	55.64	4.75	$	31.1

	Six Months Ended
	March 31, 2018
		Weighted
		Average
	Shares	Exercise
	(in thousands)	Price
Outstanding at October 1, 2017	3,278	$	56.41
Granted	667		58.66
Exercised	(224)		34.27
Outstanding at March 31, 2018	3,721	$	58.15

Summary of restricted stock awards and changes in restricted stock outstanding

	Six Months Ended
	March 31, 2018
		Weighted Average
	Shares	Grant Date Fair
	(in thousands)	Value per Share
Unvested at October 1, 2017	659	$	70.76
Granted	619		59.43
Vested (1)	(251)		71.63
Forfeited	(4)		66.27
Unvested on March 31, 2018	1,023	$	63.71

(1)The number of restricted stock awards vested includes shares that we withheld on behalf of our employees to satisfy the statutory tax withholding requirements.