Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ 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 Data [Abstract]
Revenues	$ 2,269		$ 2,153	$ 2,327	$ 2,352	$ 2,378	$ 2,411	$ 2,440	$ 2,463		$ 9,101		$ 9,692		$ 9,932
Net income (loss)	$ (70)	[1]	$ 178	$ 138	$ 233	$ 198	$ 213	$ 267	$ 13	[2]	$ 479	[1]	$ 691	[2]	$ 937
Basic earnings (loss) per share	$ (0.26)		$ 0.66	$ 0.51	$ 0.86	$ 0.73	$ 0.79	$ 0.99	$ 0.05		$ 1.77		$ 2.56		$ 3.48
Diluted earnings (loss) per share	$ (0.26)		$ 0.66	$ 0.51	$ 0.86	$ 0.73	$ 0.79	$ 0.98	$ 0.05		$ 1.77		$ 2.55		$ 3.47

[1] Net income in the fourth quarter of 2015 included a charge related to recognition of a premium deficiency in our long term care business.

[2] Net income in the first quarter of 2014 included the impairment loss on the sale of CAC.