Investments (Net Investment Income) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	$ 4,952	$ 4,976	$ 4,876
Investment expense	(125)	(117)	(122)
Total net investment income	4,827	4,859	4,754
Fixed Maturity AFS Securities [Member] | AFS Securities [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	4,079	4,041	3,976
Available-for-sale equity securities [Member] | AFS Securities [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	9	9	6
Trading securities [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	107	125	137
Mortgage loans on real estate [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	395	378	388
Real estate [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	4	7	13
Policy loans [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	152	155	155
Invested cash [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	3	2	3
Commercial mortgage loan prepayment and bond makewhole premiums [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	105	138	117
Alternative investments [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	88	130	86
Consent fees [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	5	2	4
Other Investments [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	$ 5	(11)	$ (9)
Parent Company [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Total net investment income		$ 1