Quarterly Results (Unaudited) Level 4 (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 4,513	$ 4,562	$ 4,685	$ 4,617	$ 4,617	$ 4,769	$ 4,616	$ 4,612	$ 18,377	$ 18,614	$ 20,673
Benefits, Losses and Expenses	4,009	4,183	4,215	3,992	4,173	4,273	4,466	4,003	16,399	16,915	19,202
Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest	421	372	413	467	345	388	150	466	1,673	1,349	1,225
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	0	9	0	0	37	0	(617)	29	9	(551)	(1,049)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ 421	$ 381	$ 413	$ 467	$ 382	$ 388	$ (467)	$ 495	$ 1,682	$ 798	$ 176
Earnings Per Share, Basic	$ 1.03	$ 0.92	$ 0.99	$ 1.11	$ 0.89	$ 0.89	$ (1.04)	$ 1.10	$ 4.05	$ 1.81	$ 0.37
Earnings Per Share, Diluted	$ 1.01	$ 0.90	$ 0.96	$ 1.08	$ 0.86	$ 0.86	$ (1.00)	$ 1.03	$ 3.96	$ 1.73	$ 0.36
Weighted Average Number of Shares Outstanding, Basic	406.9	413.8	418.7	422.6	429.6	437.2	450.6	449.8	415.5	441.8	447.7
Weighted Average Number of Shares Outstanding, Diluted	415.9	423.0	428.1	433.7	442.6	450.8	467.9	478.6	425.2	460.2	490.6	[1]

[1] [1]For additional information, see Note 13 - Equity and Note 17 - Stock Compensation Plans of Notes to Consolidated Financial Statements.