Segments of Operations - Assets by segment and sub-segment (Details) - USD ($) $ in Millions		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Total assets		$ 63,456	$ 60,658	$ 55,072
Property and casualty insurance
Segment Reporting Information [Line Items]
Total assets	[1]	17,681	17,171	15,574
Annuity
Segment Reporting Information [Line Items]
Total assets		39,952	37,179	33,409
Other
Segment Reporting Information [Line Items]
Total assets		$ 5,823	$ 6,308	$ 6,089

[1] Not allocable to sub-segments.