Benefit Plans (Components of net periodic cost (benefit)) (Details) - Pension Plans - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Net periodic pension cost (benefit)
Service cost	$ 0	$ 0	$ 0	$ 0
Non-service cost (benefit):
Interest cost on projected benefit obligation	23	25	70	77
Expected return on plan assets	(40)	(38)	(120)	(116)
Amortization of net actuarial loss	10	9	28	27
Settlement loss	0	6	5	8
Total non-service cost (benefit)	(7)	2	(17)	(4)
Total net periodic pension cost (benefit)	(7)	2	(17)	(4)
Insurance Claims and Policyholder's Benefits
Non-service cost (benefit):
Total non-service cost (benefit)	(3)	1	(6)	(1)
Other Operating Expenses
Non-service cost (benefit):
Total non-service cost (benefit)	$ (4)	$ 1	$ (11)	$ (3)