Variable Interest Entities (Narrative) (Details) - USD ($) $ in Millions	1 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Variable Interest Entity [Line Items]
Assets not available for use	$ 335,387	$ 319,616
Liabilities with no recourse	97,822	97,072
Noncontrolling interest	4,400	3,900
Variable Interest Entity, Primary Beneficiary | Waymo
Variable Interest Entity [Line Items]
Additional funding to investment	2,500
Nonrecourse | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Liabilities with no recourse	2,300	2,300
Asset Pledged as Collateral | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Assets not available for use	$ 7,300	$ 5,700