Income Taxes (Details) € in Millions, $ in Millions		3 Months Ended			12 Months Ended
	Oct. 04, 2017 EUR (€)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Mar. 31, 2017 USD ($)	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)
Income Tax Disclosure [Abstract]
Provision for income taxes		$ 287		$ 229
Discrete tax benefits		368		122
Cash taxes paid, net of refunds		513		$ 246	$ 1,224	$ 520
Tax contingencies		2,600	$ 2,300		$ 2,600
Income Tax Examination [Line Items]
Provisional tax benefit for impact of the Act			$ 789
Internal Revenue Service (IRS) | Domestic Tax Authority [Member]
Income Tax Examination [Line Items]
Tax examination, estimate of additional tax expense		$ 1,500
Luxembourg Tax Administration [Member] | Foreign Tax Authority [Member]
Income Tax Examination [Line Items]
Tax examination, estimate of additional tax expense | €	€ 250