Business Acquisitions and Divestitures (Narrative) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended				12 Months Ended					12 Months Ended		0 Months Ended		12 Months Ended		12 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	Dec. 24, 2012	Dec. 31, 2013 Government Business [Member]	Dec. 31, 2012 Government Business [Member]	Dec. 31, 2011 Government Business [Member]	Dec. 31, 2012 Amerigroup [Member]	Dec. 24, 2012 Amerigroup [Member]	Dec. 31, 2012 Amerigroup [Member] Government Business [Member]	Dec. 24, 2012 Amerigroup [Member] Government Business [Member]	Dec. 24, 2012 Amerigroup [Member] Restricted Stock Awards [Member]	Dec. 24, 2012 Amerigroup [Member] Nonvested Stock Option [Member]	Dec. 31, 2012 Amerigroup [Member] Customer Relationships [Member]	Dec. 24, 2012 Amerigroup [Member] Customer Relationships [Member]	Dec. 31, 2012 Amerigroup [Member] Provider And Hospital Relationships [Member]	Dec. 24, 2012 Amerigroup [Member] Provider And Hospital Relationships [Member]	Dec. 31, 2013 Amerigroup [Member]
Business Acquisition and Divestitures [Line Items]
Other intangible assets												$ 975.0					$ 975.0
Cash consideration per share amount																	$ 92.00
Cash consideration																	4,755.8
Number of Amerigroup awards converted																				0.5	0.1
Number of WellPoint awards received																				0.7	0.2
Fair value of converted Amerigroup stock awards																				17.1	2.6
Transaction costs																24.0
Measurement period adjustments, goodwill									27.4	(2.0)																28.9
Measurement period adjustments, other intangible assets																										20.0
Measurement period adjustments, current liabilities																										(1.6)
Measurement period adjustments, noncurrent liabilities																										50.5
Goodwill												3,062.0							3,062.0
Other finite-lived intangible assets																							65.0		30.0
Intangible assets amortization period, years																						3 years		20 years
Indefinite-lived intangible assets, Medicaid contracts and trade names																	880.0
Operating revenue									70,191.4	60,514.0	59,865.2		31,366.7	21,625.7	19,874.0			219.0
Net loss	148.2	656.2	800.1	885.2	464.2	691.2	643.6	856.5	2,489.7	2,655.5	2,646.7							6.1
Loss on disposal from discontinued operations									221.8	0	0
Tax benefit from loss on disposal from discontinued operations									$ 57.3