Variable Interest Entities (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Jun. 30, 2020	Dec. 31, 2019
Variable Interest Entity [Line Items]
Assets not available for use	$ 319,616		$ 275,909
Liabilities with no recourse	97,072		74,467
Noncontrolling interest	3,900		1,200
Variable Interest Entity, Primary Beneficiary | Waymo
Variable Interest Entity [Line Items]
Noncontrolling interest		$ 3,200
Variable Interest Entity, Primary Beneficiary | Nonrecourse
Variable Interest Entity [Line Items]
Liabilities with no recourse	2,300		1,200
Variable Interest Entity, Primary Beneficiary | Asset Pledged as Collateral
Variable Interest Entity [Line Items]
Assets not available for use	$ 5,700		$ 3,100