Share-Based Compensation Weighted Average Grant Date Fair Value of Restricted Stock Units (Details) - $ / shares	12 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Performance-Based Restricted Stock Units
Schedule Of Share Based Compensation, Restricted Stock Units Award, Grant Date Fair Value of Units Granted [Line Items]
Granted, stock units weighted average grant date fair value (USD per share)	$ 251.75	$ 174.92	$ 153.73
Time-Vested Restricted Stock Units
Schedule Of Share Based Compensation, Restricted Stock Units Award, Grant Date Fair Value of Units Granted [Line Items]
Granted, stock units weighted average grant date fair value (USD per share)	$ 216.06	$ 165.96	$ 145.57

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration