Basis of Presentation - Schedule of Cumulative Effect for Adoption of New Accounting Pronouncement (Details) - USD ($) $ in Millions	Jun. 30, 2020	Jan. 01, 2020	Dec. 31, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses	$ 1,070		$ 0
Allowance for doubtful accounts	0		733
Other assets	10,178		10,141
Deferred income taxes	33,798		34,703
Retained earnings	$ 56,746		$ 53,147
Adjustments due to Topic 326
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses		$ 919
Allowance for doubtful accounts		(733)
Other assets		(79)
Deferred income taxes		(65)
Retained earnings		(200)
Cumulative Effect, Period Of Adoption, Adjusted Balance
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses		919
Allowance for doubtful accounts		0
Other assets		10,062
Deferred income taxes		34,638
Retained earnings		$ 52,947