Segments of Operations - Assets by segment (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Total assets	$ 73,566	$ 70,130	$ 63,456
Property and casualty insurance
Segment Reporting Information [Line Items]
Total assets	19,689	19,098	17,681
Annuity
Segment Reporting Information [Line Items]
Total assets	47,626	45,074	39,952
Other
Segment Reporting Information [Line Items]
Total assets	$ 6,251	$ 5,958	$ 5,823