Selected Quarterly Financial Data and Supplemental Information(Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Feb. 20, 2015 stockholder
Subsequent Event [Line Items]
Revenue	$ 3,246	$ 3,141	$ 3,300	$ 3,264	$ 3,115	$ 2,932	$ 3,088	$ 3,126	$ 12,951	$ 12,261	$ 11,924
Operating income	536	445	647	673	489	404	577	607	2,301	2,077	1,829
Income from continuing operations	269	305	440	457	307	260	400	412	1,471	1,379	1,204
Discontinued operations, net of tax	30	(1)	(2)	(1)	0	(1)	(5)	12	26	6	(3)
Net income attributable to the Company	$ 294	$ 297	$ 431	$ 443	$ 303	$ 253	$ 388	$ 413	$ 1,465	$ 1,357	$ 1,176
Basic Per Share Data:
Continuing operations	$ 0.49	$ 0.55	$ 0.79	$ 0.81	$ 0.55	$ 0.46	$ 0.71	$ 0.73	$ 2.64	$ 2.46	$ 2.16
Discontinued operations, net of tax	$ 0.05	$ 0.00	$ (0.01)	$ 0.00	$ 0.00	$ 0.00	$ 0.00	$ 0.02
Net income attributable to the Company	$ 0.54	$ 0.55	$ 0.78	$ 0.81	$ 0.55	$ 0.46	$ 0.71	$ 0.75	$ 2.69	$ 2.47	$ 2.16
Diluted Per Share Data:
Continuing operations	$ 0.48	$ 0.54	$ 0.78	$ 0.80	$ 0.54	$ 0.45	$ 0.70	$ 0.72	$ 2.61	$ 2.42	$ 2.13
Discontinued operations, net of tax	$ 0.06	$ 0.00	$ (0.01)	$ 0.00	$ 0.00	$ 0.00	$ (0.01)	$ 0.02
Net income attributable to the Company	$ 0.54	$ 0.54	$ 0.77	$ 0.80	$ 0.54	$ 0.45	$ 0.69	$ 0.74	$ 2.65	$ 2.43	$ 2.13
Dividends Paid Per Share	$ 0.28	$ 0.28	$ 0.25	$ 0.25	$ 0.25	$ 0.25	$ 0.23	$ 0.23
Subsequent Event [Member]
Diluted Per Share Data:
Stockholders of record												6,197