Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Available-for-sale Debt Securities, Amortized Cost Basis	$ 55,742	$ 56,965
Available-for-sale Equity Securities, Amortized Cost Basis	812	1,135
Available-for-sale Securities, Equity Securities	875	1,121
Variable Interest Entity, Consolidated, Carrying Amount, Assets	$ 5	$ 166
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	1,500,000,000	1,500,000,000
Common stock, shares issued	490,923,222	490,923,222
Treasury stock, shares	111,275,234	89,102,038
Commercial Loan [Member]
Allowance for Loan and Lease Losses, Real Estate	$ 19	$ 23
Fixed Maturities [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	0	150
Equity Securities [Member]
Available-for-sale Equity Securities, Amortized Cost Basis	0	293
Available-for-sale Securities, Equity Securities	0	282
Partnership Interest [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	0	2
Other Liabilities [Member]
Other liabilities, variable interest entity liabilities	5	12
Other Assets [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	0	0
Short-term Investments [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	0	3
Cash [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	5	10
Equity Securities [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	0	1
Equity Securities [Member]
Available-for-sale Equity Securities, Amortized Cost Basis	812	842
Available-for-sale Securities, Equity Securities	$ 875	$ 839