Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Contingency [Line Items]
Provision for income taxes included an increase related to estimated impact of tax rate changes		$ 301
Provision for tax benefits related to settlement of employee awards		82	$ 162
Reductions in interest (net of tax)		14	15	$ 7
Provision for income taxes			51
Foreign pretax income		$ 91	$ 149	$ 178
Effective tax rate		35.00%	35.00%	35.00%
Provisional amount related to remeasurement of deferred tax assets and liabilities, recorded as a component of provision for income taxes		$ 301
Provisional amount reclassified from deferred tax liabilities for the one-time transition tax		127
State net operating loss carryforwards		121
Federal net operating loss carryforwards		82
Liability for unrecognized tax benefits		439	$ 418
Unrecognized tax benefits, accrued interest		44	45
Unrecognized tax benefits that would impact effective tax rate		145	137
Deferred tax assets, reductions		$ 4	$ 4
Scenario, Forecast [Member]
Income Tax Contingency [Line Items]
Effective tax rate	21.00%
State and Local Jurisdiction [Member] | Minimum [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards, expiration date		2020
State and Local Jurisdiction [Member] | Maximum [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards, expiration date		2036