Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2015
Income Taxes [Line Items]
U.S. federal statutory tax rate			21.00%	35.00%	28.10%	35.00%	35.00%
Provision for income taxes					$ 19,903	$ 4,412	$ 5,100
Deferred tax liabilities, revenue recognition						5,486
Income taxes paid, net of refunds					5,500	2,400	3,900
Unrecognized tax benefits	$ 11,961		$ 11,961		11,961	11,737	10,164	$ 9,599
Unrecognized tax benefits, if recognized would affect our effective tax rates	11,300		11,300		11,300	10,200	8,800
Accrued interest expense related to uncertain tax positions net of federal income tax benefits	3,000		3,000		3,000	2,300	1,900
Interest expense on unrecognized tax benefits, net of tax effects					688	399	163
Accounting Standards Update 2014-09 | Restatement Adjustment
Income Taxes [Line Items]
Provision for income taxes						$ 2,467	$ 2,147
Deferred tax liabilities, revenue recognition	7,400		7,400		7,400
Tax Cuts and Jobs Act
Income Taxes [Line Items]
Provision for income taxes	(104)	$ 13,800			13,700
Charge related to transition tax					17,900
Benefit from impact of changes in tax rate					$ 4,200
Regional Operating Centers
Income Taxes [Line Items]
Foreign earnings, taxed at rates lower than U.S. rate as a percentage of foreign income before tax					87.00%	76.00%	91.00%
Federal
Income Taxes [Line Items]
Operating loss carryforwards	257		257		$ 257
Foreign Country
Income Taxes [Line Items]
Operating loss carryforwards	11,400		11,400		11,400
State
Income Taxes [Line Items]
Operating loss carryforwards	$ 1,400		$ 1,400		$ 1,400
Federal and State | Earliest Tax Year
Income Taxes [Line Items]
Operating loss carryforwards expiration year					2019
Federal and State | Latest Tax Year
Income Taxes [Line Items]
Operating loss carryforwards expiration year					2038