Debt (Details) (USD $)	Jun. 30, 2012	Dec. 31, 2011	Jan. 31, 2012 HealthSpring [Member]	Jun. 30, 2012 Other Long Term Debt [Member]	Dec. 31, 2011 Other Long Term Debt [Member]	Jun. 30, 2012 Notes Due 2016275 Interest [Member]	Dec. 31, 2011 Notes Due 2016275 Interest [Member]	Jun. 30, 2012 Notes Due 20175375 Interest [Member]	Dec. 31, 2011 Notes Due 20175375 Interest [Member]	Jun. 30, 2012 Notes Due 2018635 Interest [Member]	Dec. 31, 2011 Notes Due 2018635 Interest [Member]	Jun. 30, 2012 Notes Due 201985 Interest [Member]	Dec. 31, 2011 Notes Due 201985 Interest [Member]	Jun. 30, 2012 Notes Due 20204375 Interest [Member]	Dec. 31, 2011 Notes Due 20204375 Interest [Member]	Jun. 30, 2012 Notes Due 20205125 Interest [Member]	Dec. 31, 2011 Notes Due 20205125 Interest [Member]	Jun. 30, 2012 Notes Due 202145 Interest [Member]	Dec. 31, 2011 Notes Due 202145 Interest [Member]	Jun. 30, 2012 Notes Due 2021637 Interest [Member]	Dec. 31, 2011 Notes Due 2021637 Interest [Member]	Jun. 30, 2012 Notes Due 20224 Interest [Member]	Dec. 31, 2011 Notes Due 20224 Interest [Member]	Jun. 30, 2012 Notes Due 2023765 Interest [Member]	Dec. 31, 2011 Notes Due 2023765 Interest [Member]	Jun. 30, 2012 Notes Due 202383 Interest [Member]	Dec. 31, 2011 Notes Due 202383 Interest [Member]	Jun. 30, 2012 Debentures Due 20277875 Interest [Member]	Dec. 31, 2011 Debentures Due 20277875 Interest [Member]	Jun. 30, 2012 Step Down Notes Due 203383 Interest [Member]	Dec. 31, 2011 Step Down Notes Due 203383 Interest [Member]	Jun. 30, 2012 Notes Due 2036615 Interest [Member]	Dec. 31, 2011 Notes Due 2036615 Interest [Member]	Jun. 30, 2012 Notes Due 20415875 Interest [Member]	Dec. 31, 2011 Notes Due 20415875 Interest [Member]	Jun. 30, 2012 Notes Due 20425375 Interest [Member]	Dec. 31, 2011 Notes Due 20425375 Interest [Member]
Debt Type Details [Abstract]
Commercial Paper	$ 225,000,000	$ 100,000,000
Long Term Debt Current	1,000,000	4,000,000
Total short-term debt	226,000,000	104,000,000
Statement Line Items [Line Items]
Long-term debt	4,985,000,000	4,990,000,000		38,000,000	43,000,000	600,000,000	600,000,000	250,000,000	250,000,000	131,000,000	131,000,000	251,000,000	251,000,000	249,000,000	249,000,000	299,000,000	299,000,000	298,000,000	298,000,000	78,000,000	78,000,000	743,000,000	743,000,000	100,000,000	100,000,000	17,000,000	17,000,000	300,000,000	300,000,000	83,000,000	83,000,000	500,000,000	500,000,000	298,000,000	298,000,000	750,000,000	750,000,000
Interest rate of long term debt issued						2.75%		5.375%		6.35%		8.50%		4.375%		5.125%		4.50%		6.37%		4.00%		7.65%		8.30%		7.875%		8.30%		6.15%		5.875%		5.375%
Debt Text Details [Abstract]
Revolving Credit and Letter of Credit Agreement - Borrowing Capacity	1,400,000,000
Revolving Credit and Letter of Credit Agreement - Additional Borrowing Capacity	4,500,000,000
Letters of Credit Issued	99,000,000
Business Acquisition [Line Items]
Total Debt Outstanding	$ 5,200,000,000		$ 326,000,000