Equity and Noncontrolling Interests Equity and Noncontrolling Interests - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended				6 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2019	Mar. 31, 2018	May 01, 2019	Apr. 30, 2019	Sep. 30, 2016
Equity, Class of Treasury Stock [Line Items]
Deferred tax asset from stock options exercised and restricted stock vestings				$ 179
Stock repurchase program, authorized amount	$ 8,500	$ 1,000		$ 1,000	$ 8,500
Treasury Stock, Value, Acquired, Cost Method	533		$ 49		1,000	$ 199
Stock Repurchase Program, Remaining Authorized Repurchase Amount	1,000				1,000
Post Merger Stock Repurchase Program [Member]
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, authorized amount									$ 1,000
Parent
Equity, Class of Treasury Stock [Line Items]
Treasury Stock, Value, Acquired, Cost Method	$ 533		$ 49		1,000	199
Accounting Standards Update 2014-09 [Member]
Equity, Class of Treasury Stock [Line Items]
Cumulative Effect on Retained Earnings, Net of Tax					45
Accounting Standards Update 2014-09 [Member] | Parent
Equity, Class of Treasury Stock [Line Items]
Cumulative Effect on Retained Earnings, Net of Tax		45			45	0
Accounting Standards Update 2016-16 [Member]
Equity, Class of Treasury Stock [Line Items]
Cumulative Effect on Retained Earnings, Net of Tax					546
Accounting Standards Update 2016-16 [Member] | Parent
Equity, Class of Treasury Stock [Line Items]
Cumulative Effect on Retained Earnings, Net of Tax		$ 546			$ 546	$ 0
Subsequent Event [Member]
Equity, Class of Treasury Stock [Line Items]
Stock Repurchase Program, Remaining Authorized Repurchase Amount								$ 8,500
Share tender offer to purchase up to $4.0 billion of ordinary shares							$ 4,000
Minimum [Member] | Subsequent Event [Member]
Equity, Class of Treasury Stock [Line Items]
Share tender offer, price per share							$ 36.00
Maximum [Member] | Subsequent Event [Member]
Equity, Class of Treasury Stock [Line Items]
Share tender offer, price per share							$ 40.00