Shareholders' Equity - Schedule of Stock Repurchases (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		102 Months Ended	108 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Sep. 30, 2020	Mar. 31, 2021
Equity, Class of Treasury Stock [Line Items]
Total repurchase cost	$ 50	$ 463
2012 - Share Repurchase Program
Equity, Class of Treasury Stock [Line Items]
Shares purchased (in shares)	0.2	2.2		137.5
Average price per share (in dollars per share)	$ 217.70	$ 212.78
Total repurchase cost	$ 50	$ 461	$ 14,800
Additional associated costs	0	2
Total costs recorded to retained earnings	$ 50	$ 463