Benefit Plans (Components of net periodic cost (benefit)) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Non-service cost:
Insurance claims and policyholders’ benefits	$ 1,327	$ 1,280	$ 2,666	$ 2,573
Other operating expenses	298	292	601	568
Pension Plans, Defined Benefit
Net periodic pension cost (benefit)
Service cost	0	0	0	0
Non-service cost:
Interest cost on projected benefit obligation	24	26	47	52
Expected return on plan assets	(40)	(39)	(80)	(78)
Amortization of net actuarial loss	9	9	18	18
Settlement loss	1	0	5	2
Total non-service cost	(6)	(4)	(10)	(6)
Total net periodic pension cost (benefit)	(6)	(4)	(10)	(6)
Insurance claims and policyholders’ benefits	2	1	3	2
Other operating expenses	$ 4	$ 3	$ 7	$ 4