Summary of Significant Accounting Policies - Computation of Weighted Average Basic and Diluted Shares Outstanding (Detail) (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
Numerator:
Income from continuing operations	$ 597	$ 701	$ 609	$ 548	$ 627	$ 598	$ 494	$ 461	$ 2,450	$ 2,180	$ 2,383
Income from discontinued operations			11	41	31	38	37	41	52	147	108
Net income attributable to Company	$ 595us-gaap_NetIncomeLoss	$ 699us-gaap_NetIncomeLoss	$ 619us-gaap_NetIncomeLoss	$ 589us-gaap_NetIncomeLoss	$ 658us-gaap_NetIncomeLoss	$ 636us-gaap_NetIncomeLoss	$ 531us-gaap_NetIncomeLoss	$ 502us-gaap_NetIncomeLoss	$ 2,502us-gaap_NetIncomeLoss	$ 2,327us-gaap_NetIncomeLoss	$ 2,491us-gaap_NetIncomeLoss
Denominator:
Basic-weighted average common shares outstanding									428	426	425
Dilutive effect of employee stock options and other unvested stock awards									2	2	2
Diluted outstanding shares									430	428	427
Basic:
Income from continuing operations	$ 1.39	$ 1.63	$ 1.42	$ 1.28	$ 1.47	$ 1.40	$ 1.16	$ 1.08	$ 5.73	$ 5.11	$ 5.61
Income from discontinued operations			$ 0.03	$ 0.10	$ 0.07	$ 0.09	$ 0.09	$ 0.10	$ 0.12	$ 0.35	$ 0.25
Net income attributable to Company	$ 1.39us-gaap_EarningsPerShareBasic	$ 1.63us-gaap_EarningsPerShareBasic	$ 1.45us-gaap_EarningsPerShareBasic	$ 1.38us-gaap_EarningsPerShareBasic	$ 1.54us-gaap_EarningsPerShareBasic	$ 1.49us-gaap_EarningsPerShareBasic	$ 1.25us-gaap_EarningsPerShareBasic	$ 1.18us-gaap_EarningsPerShareBasic	$ 5.85us-gaap_EarningsPerShareBasic	$ 5.46us-gaap_EarningsPerShareBasic	$ 5.86us-gaap_EarningsPerShareBasic
Diluted:
Income from continuing operations	$ 1.39	$ 1.62	$ 1.42	$ 1.28	$ 1.46	$ 1.40	$ 1.15	$ 1.07	$ 5.70	$ 5.09	$ 5.58
Income from discontinued operations			$ 0.02	$ 0.09	$ 0.07	$ 0.09	$ 0.09	$ 0.10	$ 0.12	$ 0.35	$ 0.25
Net income attributable to Company	$ 1.39us-gaap_EarningsPerShareDiluted	$ 1.62us-gaap_EarningsPerShareDiluted	$ 1.44us-gaap_EarningsPerShareDiluted	$ 1.37us-gaap_EarningsPerShareDiluted	$ 1.53us-gaap_EarningsPerShareDiluted	$ 1.49us-gaap_EarningsPerShareDiluted	$ 1.24us-gaap_EarningsPerShareDiluted	$ 1.17us-gaap_EarningsPerShareDiluted	$ 5.82us-gaap_EarningsPerShareDiluted	$ 5.44us-gaap_EarningsPerShareDiluted	$ 5.83us-gaap_EarningsPerShareDiluted
Cash dividends per share	$ 0.46	$ 0.46	$ 0.46	$ 0.26	$ 0.26	$ 0.26	$ 0.26	$ 0.13	$ 1.64	$ 0.91	$ 0.49

Aggregate dividends paid during the period for each share of common stock outstanding.

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