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Basis of Presentation - Schedule of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 7,047		$ 2,594
Increase (decrease) of cash and cash equivalents	4,453
Cash, cash equivalents and restricted cash	8,324	$ 3,537	3,917	$ 3,916
Increase (decrease) in cash, cash equivalents and restricted cash	4,407	$ (379)
Prepaid expenses and other
Cash and Cash Equivalents [Line Items]
Restricted cash	1,154		1,221
Increase (decrease) in restricted cash	(67)
Other assets
Cash and Cash Equivalents [Line Items]
Restricted cash	123		$ 102
Increase (decrease) in restricted cash	$ 21