Shareholders' Equity - Ordinary Shares (Details) - USD ($) $ / shares in Units, shares in Thousands	1 Months Ended	12 Months Ended
	Jan. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Feb. 28, 2017	Nov. 30, 2014	Apr. 30, 2012
Common Stock Programs
Cost of shares repurchased		$ 2,415,000,000	$ 1,257,000,000	$ 1,550,000,000
Additional transaction costs		$ 12,000,000	$ 6,000,000
Share Repurchase Program of 2012
Common Stock Programs
Share repurchase authorization limit							$ 5,000,000,000.0
Number of shares repurchased (in shares)		108,200
Cost of shares repurchased		$ 9,600,000,000
Share Repurchase Program of 2014
Common Stock Programs
Share repurchase authorization limit		$ 15,000,000,000.0			$ 5,000,000,000.0	$ 5,000,000,000.0
Share Repurchase Program
Common Stock Programs
Number of shares repurchased (in shares)		18,000	12,200
Average price per share of shares purchased under share repurchase program (in dollars per share)		$ 133.67	$ 102.66
Cost of shares repurchased		$ 2,400,000,000	$ 1,300,000,000
Share Repurchase Programs of 2012 and 2014
Common Stock Programs
Share repurchase, remaining authorization limit		$ 5,400,000,000
Subsequent Event | Share Repurchase Program
Common Stock Programs
Number of shares repurchased (in shares)	118
Average price per share of shares purchased under share repurchase program (in dollars per share)	$ 134.41
Cost of shares repurchased	$ 15,900,000