Income Taxes - Narrative (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure
U.S. federal statutory income tax rate	35.00%	35.00%	35.00%
Tax benefit from share-based award activity	$ 1,721	$ 1,853	$ 602
Valuation allowance, deferred tax assets	205	101
Tax-effected benefit to be recognized in additional paid in capital if net operating loss carryforward is utilized	$ 655
Cumulative stock ownership change threshold	50.00%
Change in ownership percentage over period	3 years
Unrecognized tax benefits	$ 3,017	$ 1,682	$ 1,316	$ 164
Unrecognized tax benefits that would impact effective tax rate	2,400
Internal Revenue Service (IRS)
Income Tax Disclosure
Operating loss carryforwards	$ 2,700
Operating loss carryforwards expiration year	2032
Tax credit carryforward	$ 1,080
Tax credit carryforward expiration year	2030
State and Local Jurisdiction
Income Tax Disclosure
Operating loss carryforwards	$ 3,310
Operating loss carryforwards expiration year	2023
Tax credit carryforward	$ 905
Tax credit carryforward expiration year	2032