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Business Acquisitions and Divestitures (Assets Liabilities Acquired) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 24, 2012
Business Acquisition [Line Items]
Goodwill	$ 17,082.0us-gaap_Goodwill	$ 16,917.2us-gaap_Goodwill	$ 16,889.8us-gaap_Goodwill
Amerigroup [Member]
Business Acquisition [Line Items]
Current assets				2,716.5
Goodwill				3,062.0
Other intangible assets				975.0
Other non current assets				406.1
Total assets acquired				7,159.6
Current liabilities				1,416.6
Non current liabilities				967.5
Total liabilities assumed				2,384.1
Net assets acquired				$ 4,775.5