Shareholders' Equity - Schedule of Stock Repurchases (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended				6 Months Ended		87 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019
Class of Stock [Line Items]
Shares purchased (in shares)							124.6
Total repurchase cost	$ 1,056	$ 101	$ 402	$ 553			$ 12,200
2012 - Share Repurchase Program
Class of Stock [Line Items]
Shares purchased (in shares)	5.8		2.8		6.4	6.7
Average price per share of stock repurchased (in dollars per share)	$ 183.23		$ 141.23		$ 181.07	$ 141.06
Total repurchase cost	$ 1,050		$ 400		$ 1,150	$ 950
Additional associated costs	6		2		7	5
Total repurchase and associated costs	$ 1,056		$ 402		$ 1,157	$ 955