Earnings Per Common Share Computation (Details) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	3 Months Ended										12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010		Sep. 30, 2010	Jun. 30, 2010		Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income available for common stockholders	$ 199	$ 445	$ 460	$ 315	$ 107	[1]	$ 393	$ 340	[2]	$ 259	$ 1,419	$ 1,099	$ 1,040
Weighted-average outstanding shares of common stock used to compute basic earnings per common share											165,413	167,782	167,364
Shares used to compute diluted earnings per common share											167,827	169,798	169,071
Basic earnings per common share	$ 1.22	$ 2.71	$ 2.76	$ 1.88	$ 0.64	[1]	$ 2.35	$ 2.02	[2]	$ 1.54	$ 8.58	$ 6.55	$ 6.21
Diluted earnings per common share	$ 1.20	$ 2.67	$ 2.71	$ 1.86	$ 0.63	[1]	$ 2.32	$ 2.00	[2]	$ 1.52	$ 8.46	$ 6.47	$ 6.15
Number of antidilutive stock options and restricted stock awards excluded from computation											864	3,820	5,675
Employee Stock Options [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Dilutive effect of employee stock options and restricted stock											959	676	677
Restricted Stock [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Dilutive effect of employee stock options and restricted stock											1,455	1,340	1,030

[1] Includes an expense of $139 million ($88 million after tax, or $0.52 per diluted common share) associated with reserve strengthening for our closed block of long-term care policies acquired in connection with the 2007 acquisition of KMG America Corporation as more fully described in Note 17 to the consolidated financial statements.

[2] Includes an expense of $147 million ($93 million after tax, or $0.55 per diluted common share) for the write-down of deferred acquisition costs associated with our individual commercial medical policies as more fully described in Note 17 to the consolidated financial statements.