Income Taxes - Reconciliation of Income Tax Expense Computed Using U.S. Statutory Federal Tax Rate to Actual Income Tax Expense (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Amount
Income tax expense at the U.S. federal statutory tax rate	$ 1,844	$ 1,710	$ 1,505
One-time charge due to tax legislation	1,862	0	0
Excess tax benefits for share-based payment awards	(106)	(152)	0
U.S. manufacturing deduction benefit (b)	(7)	(117)	(123)
Research and development tax credit	(115)	(107)	(70)
Tax deductible dividends	(94)	(92)	(87)
Other, net	(44)	(109)	(52)
Total income tax expense	$ 3,340	$ 1,133	$ 1,173
Rate
Income tax expense at the U.S. federal statutory tax rate	35.00%	35.00%	35.00%
Deferred tax write down and transition tax (a)	35.30%	0.00%	0.00%
Excess tax benefits for share-based payment awards	(2.00%)	(3.10%)	0.00%
U.S. manufacturing deduction benefit (b)	(0.10%)	(2.40%)	(2.90%)
Research and development tax credit	(2.20%)	(2.20%)	(1.60%)
Tax deductible dividends	(1.80%)	(1.90%)	(2.00%)
Other, net	(0.80%)	(2.20%)	(1.20%)
Income tax expense	63.40%	23.20%	27.30%