Basis of Presentation and Significant Accounting Policies and Practices - Effects of Adoption of New Standard (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income statement data:
Provision for income taxes									$ 1,335	$ 1,230	$ 1,053
Net income	$ 1,047	$ 1,018	$ 819	$ 711	$ 836	$ 798	$ 696	$ 656	$ 3,595	$ 2,986	$ 2,821
Average diluted shares outstanding, in millions									1,021	1,043	1,080
Basic EPS	$ 1.04	$ 1.00	$ 0.81	$ 0.70	$ 0.81	$ 0.77	$ 0.66	$ 0.62	$ 3.54	$ 2.86	$ 2.61
Diluted EPS	$ 1.02	$ 0.98	$ 0.79	$ 0.69	$ 0.80	$ 0.76	$ 0.65	$ 0.61	$ 3.48	$ 2.82	$ 2.57
Cash flow data:
Cash flows from operating activities									$ 4,614	$ 4,397	$ 4,054
Cash flows from financing activities									$ (3,810)	(4,294)	(4,105)
ASU No. 2016-09 | Reported
Income statement data:
Provision for income taxes		$ 413	$ 323	$ 282
Net income		$ 968	$ 779	$ 668
Average diluted shares outstanding, in millions		1,017	1,016	1,018
Basic EPS		$ 0.95	$ 0.77	$ 0.65
Diluted EPS		$ 0.94	$ 0.76	$ 0.65
Cash flow data:
Cash flows from operating activities		$ 1,413	$ 1,069	$ 547						4,268	3,892
Cash flows from financing activities		(676)	(1,180)	(839)						(4,165)	(3,943)
ASU No. 2016-09 | Recast
Income statement data:
Provision for income taxes		363	283	239
Net income		$ 1,018	$ 819	$ 711
Average diluted shares outstanding, in millions		1,023	1,020	1,022
Basic EPS		$ 1.00	$ 0.81	$ 0.70
Diluted EPS		$ 0.98	$ 0.79	$ 0.69
Cash flow data:
Cash flows from operating activities		$ 1,465	$ 1,109	$ 653						4,397	4,054
Cash flows from financing activities		$ (728)	$ (1,220)	$ (945)						$ (4,294)	$ (4,105)