Acquisitions and Sale of Businesses - Impact of exited lines on earnings (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Sale of Businesses
Net investment income									$ 2,132	$ 2,303	$ 2,094
Net earnings, including noncontrolling interests	$ 694	$ 164	$ 167	$ (304)	$ 191	$ 143	$ 209	$ 326	721	869	517
Realized gains on subsidiaries									23	0	0
Income tax expense (benefit)									(127)	(239)	(122)
Less: Net loss attributable to noncontrolling interests									11	28	13
Neon Capital Limited
Sale of Businesses
Underwriting loss									(135)	(36)	(63)
Net investment income									(5)	6	10
Other income and expenses, net									(5)	(10)	(5)
Net earnings, including noncontrolling interests									(145)	$ (40)	$ (58)
Realized gains on subsidiaries	$ 23								23
Total pretax loss from Neon exited lines									(122)
Income tax expense (benefit)									72
Less: Net loss attributable to noncontrolling interests									(11)
Net loss from Neon exited lines attributable to shareholders									$ (39)