Segment Information - Revenue by Product Type (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Revenue from External Customer [Line Items]
Premiums and fees, mail order pharmacy revenues and other revenues	$ 9,174	$ 8,374	$ 18,292	$ 16,551

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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