Segments of Operations - Assets by segment (Details) - USD ($) $ in Millions		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Total assets		$ 70,130	$ 63,456	$ 60,658
Property and casualty insurance
Segment Reporting Information [Line Items]
Total assets	[1]	19,098	17,681	17,171
Annuity
Segment Reporting Information [Line Items]
Total assets		45,074	39,952	37,179
Other
Segment Reporting Information [Line Items]
Total assets		$ 5,958	$ 5,823	$ 6,308

[1] Not allocable to sub-segments.