Earnings Per Share (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended															12 Months Ended
	Dec. 31, 2013		Sep. 30, 2013	Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2012		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012		Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Earnings Per Share [Abstract]
Shareholders' net income	$ 361	[1]	$ 553	$ 505	[2]	$ 57	[3]	$ 406	[4]	$ 466	[5]	$ 380	[6]	$ 371	[7]	$ 1,476	$ 1,623	$ 1,260
Shares (in thousands):
Weighted average																279,296,000	284,819,000	270,691,000
Common stock equivalents																5,389,000	4,711,000	3,558,000
Total shares																284,685,000	289,530,000	274,249,000
EPS, basic	$ 1.32		$ 1.99	$ 1.79		$ 0.20		$ 1.43		$ 1.64		$ 1.33		$ 1.30		$ 5.28	$ 5.70	$ 4.65
EPS, effect of dilution																$ (0.10)	$ (0.09)	$ (0.06)
EPS, diluted	$ 1.29		$ 1.95	$ 1.76		$ 0.20		$ 1.41		$ 1.61		$ 1.31		$ 1.28		$ 5.18	$ 5.61	$ 4.59
Antidilutive Options [Abstract]
Antidilutive options																900,000	2,500,000	3,700,000

[1] The fourth quarter of 2013 includes an after-tax charge of $40 million for an organizational efficiency plan.

[2] The second quarter of 2013 includes an after-tax charge of $24 million for the Pharmacy Benefits Manager (“PBM”) partnering agreement with Catamaran.

[3] The first quarter of 2013 includes an after-tax gain of $25 for the GMIB business, an after-tax charge of $507 million for the transaction with Berkshire to effectively exit the Run-off Reinsurance business, and an after-tax charge of $51 million related to the disability claims regulatory matter in the Group Disability and Life segment.

[4] The fourth quarter of 2012 includes an after-tax gain of $7 million for the GMIB business and an after-tax charge of $68 million for litigation matters.

[5] The third quarter of 2012 includes an after-tax gain of $32 million for the GMIB business, an after-tax charge of $12 million for costs associated with acquisitions, and an after-tax charge of $50 million for costs associated with an organizational efficiency plan.

[6] The second quarter of 2012 includes an after-tax loss of $51 million for the GMIB business.

[7] The first quarter of 2012 includes an after-tax gain of $41 million for the GMIB business, an after-tax charge of $28 million for costs associated with acquisitions, and an after-tax charge of $13 million for costs associated a litigation matter in Global Health Care.