Non-Insurance Revenues from Contracts with Customers (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Deferred non-insurance warranty revenue	$ 4,309		$ 4,309		$ 4,023
Contract with customer, liability, revenue recognized	$ 300	$ 300	$ 600	$ 600