Stock-Based Compensation - Stock Options and Awards Activity (Details) shares in Thousands	9 Months Ended
	Jun. 30, 2018 $ / shares shares
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Nonvested stock, beginning of period (in shares) | shares	399
Granted (in shares) | shares	98
Vested (in shares) | shares	(213)	[1]
Forfeited (in shares) | shares	(6)
Nonvested stock, end of period (in shares) | shares	278
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Nonvested stock, beginning of period (in dollars per share) | $ / shares	$ 118.83
Granted (in dollars per share) | $ / shares	255.64
Vested (in dollars per share) | $ / shares	88.43	[1]
Forfeited (in dollars per share) | $ / shares	116.70
Nonvested stock, end of period (in dollars per share) | $ / shares	$ 155.03
Performance Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Nonvested stock, beginning of period (in shares) | shares	176
Granted (in shares) | shares	78
Vested (in shares) | shares	(95)	[1]
Forfeited (in shares) | shares	0
Nonvested stock, end of period (in shares) | shares	159
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Nonvested stock, beginning of period (in dollars per share) | $ / shares	$ 105.34
Granted (in dollars per share) | $ / shares	315.05
Vested (in dollars per share) | $ / shares	70.57	[1]
Forfeited (in dollars per share) | $ / shares	0.00
Nonvested stock, end of period (in dollars per share) | $ / shares	$ 155.76
Restricted Stock Units and Awards [Abstract]
Targeted goal of performance based awards and units	100.00%
Performance Restricted Stock Units | Minimum
Restricted Stock Units and Awards [Abstract]
Percentage of performance-based awards earned by recipient	0.00%
Performance Restricted Stock Units | Maximum
Restricted Stock Units and Awards [Abstract]
Percentage of performance-based awards earned by recipient	200.00%

[1] Service-based restricted stock units vested during the fiscal year. Performance-based restricted stock units included at 100% of target goal; under the terms of the awards, the recipient may earn between 0% and 200% of the award.