Selected Quarterly Financial Data and Supplemental Information (Details) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018 USD ($) $ / shares	Sep. 30, 2018 USD ($) $ / shares	Jun. 30, 2018 USD ($) $ / shares	Mar. 31, 2018 USD ($) $ / shares	Dec. 31, 2017 USD ($) $ / shares	Sep. 30, 2017 USD ($) $ / shares	Jun. 30, 2017 USD ($) $ / shares	Mar. 31, 2017 USD ($) $ / shares	Dec. 31, 2018 USD ($) $ / shares	Dec. 31, 2017 USD ($) $ / shares	Dec. 31, 2016 USD ($) $ / shares	Feb. 18, 2019 stockholder
Subsequent Event [Line Items]
Revenue | $	$ 3,712	$ 3,504	$ 3,734	$ 4,000	$ 3,685	$ 3,341	$ 3,495	$ 3,503	$ 14,950	$ 14,024	$ 13,211
Operating income | $	621	541	691	908	670	535	701	749	2,761	2,655	2,431
Income from continuing operations | $	159	279	536	696	28	397	507	578	1,670	1,510	1,795
Discontinued operations, net of tax | $					2	0	0	0	0	2	0
Net income attributable to the Company | $	$ 153	$ 276	$ 531	$ 690	$ 29	$ 393	$ 501	$ 569	$ 1,650	$ 1,492	$ 1,768
Basic Per Share Data(a):
Continuing operations (in dollars per share)	$ 0.30	$ 0.55	$ 1.05	$ 1.36	$ 0.05	$ 0.77	$ 0.98	$ 1.10	$ 3.26	$ 2.91	$ 3.41
Discontinued operations, net of tax (in dollars per share)	0.00	0.00	0.00	0.00	0.01	0.00	0.00	0.00
Net income attributable to the Company (in dollars per share)	0.30	0.55	1.05	1.36	0.06	0.77	0.98	1.10	3.26	2.91	3.41
Diluted Per Share Data(a):
Continuing operations (in dollars per share)	0.30	0.54	1.04	1.34	0.05	0.76	0.96	1.09	3.23	2.87	3.38
Discontinued operations, net of tax (in dollars per share)	0.00	0.00	0.00	0.00	0.01	0.00	0.00	0.00
Net income attributable to the Company (in dollars per share)	0.30	0.54	1.04	1.34	0.06	0.76	0.96	1.09	$ 3.23	$ 2.87	$ 3.38
Dividends Paid Per Share	$ 0.415	$ 0.415	$ 0.375	$ 0.375	$ 0.375	$ 0.375	$ 0.34	$ 0.34
Provisional charge | $									$ 460
Subsequent Event
Diluted Per Share Data(a):
Stockholders of record | stockholder												5,063