Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share [Abstract]
Stock Issued During Period, Shares, New Issues									3,210,427	3,089,234	3,731,075
Net income	$ 1,173	$ 1,091	$ 1,150	$ 1,040	$ 355	$ 1,231	$ 1,294	$ 1,082	$ 4,454	$ 3,962	$ 3,861
Weighted-average shares outstanding									455,910,463	463,629,203	467,145,716
Share-based compensation plans									3,004,200	3,173,145	4,051,185
Adjusted weighted-average shares outstanding and assumed conversions									458,914,663	466,802,348	471,196,901
Basic earnings per share	$ 2.59	$ 2.40	$ 2.52	$ 2.27	$ 0.77	$ 2.66	$ 2.78	$ 2.32	$ 9.77	$ 8.55	$ 8.26
Diluted earnings per share	$ 2.57	$ 2.38	$ 2.50	$ 2.25	$ 0.76	$ 2.64	$ 2.76	$ 2.30	$ 9.71	$ 8.49	$ 8.19
Potential anti-dilutive share conversions									2,410,337	3,543,188	1,776,025