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, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Numerator:
Net income attributable to Company	$ 668	$ 612	$ 605	$ 606	$ 574	$ 532	$ 481	$ 407	$ 2,491	$ 1,994	$ 1,667
Denominator:
Basic-weighted average common shares outstanding									425	422	417
Dilutive effect of employee stock options and other unvested stock awards									2	2	2
Diluted outstanding shares									427	424	419
Basic earnings attributable to Company per share	$ 1.57	$ 1.44	$ 1.42	$ 1.43	$ 1.36	$ 1.26	$ 1.14	$ 0.97	$ 5.86	$ 4.73	$ 3.99
Diluted earnings attributable to Company per share	$ 1.56	$ 1.43	$ 1.42	$ 1.42	$ 1.35	$ 1.25	$ 1.13	$ 0.96	$ 5.83	$ 4.70	$ 3.98
Cash dividends per share	$ 0.13	$ 0.12	$ 0.12	$ 0.12	$ 0.12	$ 0.11	$ 0.11	$ 0.11	$ 0.49	$ 0.45	$ 0.41