Condensed Financial Information (Parent Company) (Condensed Balance Sheet - Parenthetical) (Details) - USD ($) $ / shares in Units, $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Condensed Balance Sheet Statements, Captions [Line Items]
Amortized cost of fixed maturity securities available-for-sale	$ 286,069	$ 271,676
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, aggregate liquidation preference	2,100	2,100
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	3,000,000,000	3,000,000,000
Common stock, shares issued	1,168,710,101	1,164,029,985
Common stock, shares outstanding	1,043,588,396	1,095,519,005
Treasury stock, shares	125,121,705	68,510,980
Parent Company
Condensed Balance Sheet Statements, Captions [Line Items]
Amortized cost of fixed maturity securities available-for-sale	$ 4,520	$ 3,900
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, aggregate liquidation preference	2,100	2,100
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	3,000,000,000	3,000,000,000
Common stock, shares issued	1,168,710,101	1,164,029,985
Common stock, shares outstanding	1,043,588,396	1,095,519,005
Treasury stock, shares	125,121,705	68,510,980