Income Taxes - Additional Information (Details) € in Millions, $ in Millions		3 Months Ended								6 Months Ended	12 Months Ended
	Oct. 04, 2017 EUR (€)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Income Tax Disclosure [Abstract]
Provision for income taxes, net		$ 327	$ 508	$ 74	$ 287	$ 16	$ 58	$ 467	$ 229		$ 1,197	$ 769	$ 1,425
Cash taxes paid, net of refunds											1,184	957	412
Provisional tax benefit for impact of the Act												789
Income Taxes [Line Items]
Valuation allowance against the net deferred tax assets										$ 600
Tax credit carryforwards		1,700									1,700
Accrued interest and penalties, net of federal income tax benefit, related to tax contingencies		127				$ 107					127	107
Interest and penalties, net of federal income tax benefit											20	$ 40	$ 9
Federal
Income Taxes [Line Items]
Net operating loss carryforwards		627									627
Federal | IRS
Income Taxes [Line Items]
Tax examination, estimate of additional tax expense											1,500
Federal | Capital Loss Carryforward
Income Taxes [Line Items]
Tax credit carryforwards		261									261
Foreign
Income Taxes [Line Items]
Net operating loss carryforwards		7,800									7,800
Foreign | Luxembourg Tax Administration
Income Taxes [Line Items]
Tax examination, estimate of additional tax expense | €	€ 250
State
Income Taxes [Line Items]
Net operating loss carryforwards		$ 919									$ 919