Share-Based Compensation (Tables)

12 Months Ended

Sep. 30, 2019

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

Fair value is estimated at the grant date based on a Black-Scholes-Merton option-pricing model using the following weighted-average assumptions:

	Year ended September 30, 2019
	2019		2018		2017
Expected stock price volatility	27	%	30	%	31	%
Expected dividend yield	—	%	—	%	—	%
Risk free interest rate	1.86	%	1.23	%	0.99	%
Average expected life (in years)	6.05		3.06		3.08

Share-based Compensation, Stock Options, Activity [Table Text Block]

The following is a summary of stock option activity for the year ended September 30, 2019:

	Shares Available for Grant		Number of Options Outstanding		Weighted Average  Exercise Price		Weighted Average Grant Date Fair Value		Weighted Average Remaining Term (in years)	Aggregate Intrinsic Value ($ millions)
Balances at September 30, 2018	588,020		835,454		$	29.27	$	11.93	3.01	$	15.9
Additional shares authorized by shareholders	1,000,000
Granted	(922,000	)	922,000		$	44.31	$	10.47
Exercised			(46,444	)	$	25.04	$	5.21
Forfeited	25,048		(25,048	)	$	31.31	$	11.91
Expired	1,584		(1,584	)	$	33.83	$	7.46
Balances at September 30, 2019	692,652		1,684,378		$	37.59	$	11.32	4.62	$	9.2
Exercisable at September 30, 2019			472,424		$	28.96	$	12.27	2.08	$	5.8

Schedule of Share-based Compensation, Shares Authorized under Stock Option Plans, by Exercise Price Range [Table Text Block]

The options outstanding as of September 30, 2019 broken down by exercise price are as follows:

Exercise Price					Number of Options Outstanding	Weighted Average Exercise Price		Weighted Average Remaining Term (in Years)
$	—	-	$	5.00	—	n/a		n/a
$	5.00	-	$	10.00	—	n/a		n/a
$	10.00	-	$	15.00	—	n/a		n/a
$	15.00	-	$	20.00	—	n/a		n/a
$	20.00	-	$	25.00	—	n/a		n/a
$	25.00	-	$	30.00	564,000	$	25.91	2.37
$	30.00	-	$	35.00	32,881	$	31.37	0.28
$	35.00	-	$	40.00	213,830	$	39.33	2.43
$	40.00	-	$	45.00	871,667	$	44.91	6.78
$	45.00	-	$	50.00	—	n/a		n/a
$	50.00	-	$	55.00	—		n/a	n/a
$	55.00	-	$	60.00	2,000	$	55.28	2.89
					1,684,378	$	37.59	4.62

Schedule of Share-based Compensation, Restricted Stock Units Award Activity [Table Text Block]

The following is a summary of restricted stock activity through September 30, 2019:

	Shares Available for Grant		Number of Shares Outstanding		Weighted Average Grant Date Fair Value		Weighted Average Remaining Term (in years)	Aggregate Intrinsic Value ($ millions)
Balances at September 30, 2018	1,377,278		274,628		$	38.20	1.15	$	13.3
Granted	(223,481	)	223,481		$	39.57
Vested	—		(144,226	)	$	35.85
Forfeited	3,105		(3,105	)	$	35.62
Balances at September 30, 2019	1,156,902		350,778		$	40.06	1.36	$	14.4