Income Taxes - Income Taxes (Details) € in Millions, $ in Millions		3 Months Ended		12 Months Ended
	Oct. 04, 2017 EUR (€)	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)
Income Tax Disclosure [Abstract]
Provision for income taxes		$ 744	$ 836
Discrete tax benefits		273	261
Cash paid for income taxes, net of refunds		305	$ 168	$ 1,017	$ 840
Tax contingencies		$ 3,800		$ 3,800		$ 3,900
Luxembourg Tax Administration [Member] | Foreign Tax Authority [Member]
Income Tax Examination [Line Items]
Tax examination, estimate of additional tax expense | €	€ 250