Stock-based Compensation Summary of Stock Option Activity (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2017 USD ($) $ / shares shares
Stock Appreciation Rights (SARs)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Grant Date Fair Value [Roll Forward]
Weighted Average Option Price, Outstanding beginning balance | $ / shares	$ 30.49
Weighted Average Option Price, Spin Conversion | $ / shares	28.06
Weighted Average Option Price, Granted | $ / shares	41.73
Weighted Average Option Price, Exercised | $ / shares	29.62
Weighted Average Option Price, Forfeited or expired | $ / shares	39.17
Weighted Average Option Price, Outstanding ending balance | $ / shares	27.02
Weighted Average Option Price, Exercisable | $ / shares	$ 26.40
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Shares Subject to Option, Outstanding beginning balance | shares	1,201,165
Shares Subject to Option, Spin Conversion | shares	29,241
Shares Subject to Option, Granted | shares	15,693
Shares Subject to Option, Exercised | shares	(290,378)
Shares Subject to Option, Forfeited or expired | shares	(62,410)
Shares Subject to Option, Outstanding ending balance | shares	893,311
Shares Subject to Option, Exercisable | shares	853,260
Weighted Average Remaining Contractual Life (years), Outstanding	3 years 292 days
Weighted Average Remaining Contractual Life (years), Exercisable	3 years 183 days
Aggregate Intrinsic Value, Outstanding | $	$ 12
Aggregate Intrinsic Value, Exercisable | $	$ 12
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Grant Date Fair Value [Roll Forward]
Weighted Average Option Price, Outstanding beginning balance | $ / shares	$ 32.07
Weighted Average Option Price, Spin Conversion | $ / shares	31.02
Weighted Average Option Price, Granted | $ / shares	41.73
Weighted Average Option Price, Exercised | $ / shares	28.33
Weighted Average Option Price, Forfeited or expired | $ / shares	42.33
Weighted Average Option Price, Outstanding ending balance | $ / shares	32.76
Weighted Average Option Price, Exercisable | $ / shares	$ 33.16
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Shares Subject to Option, Outstanding beginning balance | shares	22,332,233
Shares Subject to Option, Spin Conversion | shares	1,547,096
Shares Subject to Option, Granted | shares	2,841,686
Shares Subject to Option, Exercised | shares	(5,919,790)
Shares Subject to Option, Forfeited or expired | shares	(1,070,782)
Shares Subject to Option, Outstanding ending balance | shares	19,730,443
Shares Subject to Option, Exercisable | shares	15,054,034
Weighted Average Remaining Contractual Life (years), Outstanding	4 years 329 days
Weighted Average Remaining Contractual Life (years), Exercisable	4 years
Aggregate Intrinsic Value, Outstanding | $	$ 187
Aggregate Intrinsic Value, Exercisable | $	$ 180