Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Fixed-maturity securities held as available-for-sale, amortized cost	$ 5,206	$ 5,450
Preferred stock, par value	$ 1	$ 1
Preferred stock, authorized shares	10,000,000	10,000,000
Preferred stock, issued	0	0
Preferred stock, outstanding	0	0
Common stock, par value	$ 1	$ 1
Common stock, authorized shares	400,000,000	400,000,000
Common stock, issued shares	283,905,896	283,989,999
Accumulated other comprehensive income (loss), taxes	$ 17	$ 37
Treasury stock, shares	153,946,569	148,789,168
Non Variable Interest Entity [Member]
Fixed-maturity securities held as available-for-sale, amortized cost	$ 4,723	$ 4,713
Investments pledged as collateral, amortized cost	136	234
Short-term investments held as available-for-sale, amortized cost	398	552
Other investments, fair value	4	5
Medium-term notes, financial instruments carried at fair value	104	101
Variable Interest Entity Primary Beneficiary [Member]
Investments held-to-maturity, fair value	879	876
Variable interest entity notes, financial instruments carried at fair value	$ 1,306	$ 1,351