Insurance - Analysis of changes in the liability for losses and loss adjustment expenses, net of reinsurance (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020		Jun. 30, 2019
Analysis of changes in the liability for losses and loss adjustment expenses, net of reinsurance
Balance at beginning of year	$ 10,232		$ 9,741
Less reinsurance recoverables, net of allowance	3,024		2,942
Net liability at beginning of year	7,208		6,799
Liability for losses and loss adjustment expenses, period increase (decrease) [Abstract]
Provision for losses and LAE occurring in the current period	1,597		1,501
Net increase (decrease) in the provision for claims of prior years	(119)		(86)
Total losses and LAE incurred	1,478	[1]	1,415
Payments for losses and LAE of:
Current year	(284)		(291)
Prior years	(1,068)		(1,079)
Total payments	(1,352)		(1,370)
Foreign currency translation and other	(20)		1
Net liability at end of period	7,314		6,845
Add back reinsurance recoverables, net of allowance	3,007		2,732
Gross unpaid losses and LAE included in the balance sheet at end of period	$ 10,321		$ 9,577

[1] Includes $106 million in losses and LAE incurred in the Neon exited lines in the first six months of 2020.