Employee Benefit Arrangements - Obligations and Funded Status (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Change in plan assets:
Accumulated other comprehensive (income) loss, net of tax	$ (15)	$ (26)	$ (33)
Other Postretirement Benefits
Change in benefit obligation:
Benefits obligations, beginning balance	21	28
Service cost	0	0	0
Interest cost	1	1	1
Net actuarial (gains) losses	1	(2)
Benefits paid	3	3
(Gain) loss recognized due to curtailment	0	0
Plan amendments	0	(3)
Benefits obligations, ending balance	20	21	28
Change in plan assets:
Fair value of plan assets, beginning balance	0	0
Actual return on plan assets	0	0
Employer contributions	3	3
Benefits paid	(3)	(3)
Fair value of plan assets, ending balance	0	0	0
Funded status at end of the year	(20)	(21)
Accrued benefit cost	(20)	(21)
Net amount recognized	(20)	(21)
Prior service cost (credit)	(15)	(18)
Tax effect	5	6
Accumulated other comprehensive (income) loss, net of tax	(10)	(12)
Pension Plan
Change in benefit obligation:
Benefits obligations, beginning balance	2,116	2,054
Service cost	24	25	26
Interest cost	93	96	104
Net actuarial (gains) losses	156	33
Benefits paid	98	92
(Gain) loss recognized due to curtailment	3	0
Plan amendments	0	0
Benefits obligations, ending balance	2,294	2,116	2,054
Change in plan assets:
Fair value of plan assets, beginning balance	1,463	1,395
Actual return on plan assets	257	80
Employer contributions	142	80
Benefits paid	(98)	(92)
Fair value of plan assets, ending balance	1,764	1,463	$ 1,395
Funded status at end of the year	(530)	(653)
Accrued benefit cost	(530)	(653)
Net amount recognized	(530)	(653)
Prior service cost (credit)	(10)	(21)
Tax effect	4	7
Accumulated other comprehensive (income) loss, net of tax	$ (6)	$ (14)