Shareholders' Equity - Schedule of Stock Repurchases (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		84 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019
Class of Stock [Line Items]
Shares purchased (in shares)			118.9
Total repurchase cost	$ 101	$ 553	$ 11,100
2012 - Share Repurchase Program
Class of Stock [Line Items]
Shares purchased (in shares)	0.6	3.9
Average price per share of stock repurchased (in dollars per share)	$ 161.16	$ 140.94
Total repurchase cost	$ 100	$ 550
Additional associated costs	1	3
Total repurchase and associated costs	$ 101	$ 553