Benefit Plans (Reconciliation of Level 3 Plan Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fixed Maturities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	$ 784
Fair value of plan assets at December 31	752	$ 784
Corporate and other bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	465
Fair value of plan assets at December 31	510	465
Total assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	1,332
Fair value of plan assets at December 31	1,317	1,332
Fair Value, Inputs, Level 3 [Member] | Fixed Maturities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	10	15
Defined Benefit Plan, Actual Return on Plan Assets Still Held	0	0
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period	0	0
Defined Benefit Plan, Purchases, Sales, and Settlements	0	0
Defined Benefit Plan, Net transfers into (out of) Level 3	0	(5)
Fair value of plan assets at December 31	10	10
Fair Value, Inputs, Level 3 [Member] | Corporate and other bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	10	15
Defined Benefit Plan, Actual Return on Plan Assets Still Held	0	0
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period	0	0
Defined Benefit Plan, Purchases, Sales, and Settlements	0	0
Defined Benefit Plan, Net transfers into (out of) Level 3	0	(5)
Fair value of plan assets at December 31	10	10
Fair Value, Inputs, Level 3 [Member] | Total assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	10	15
Defined Benefit Plan, Actual Return on Plan Assets Still Held	0	0
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period	0	0
Defined Benefit Plan, Purchases, Sales, and Settlements	0	0
Defined Benefit Plan, Net transfers into (out of) Level 3	0	(5)
Fair value of plan assets at December 31	$ 10	$ 10