Commitments And Contingencies (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) class_actions	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Commitments And Contingencies [Line Items]
California gross premium tax rate	2.35%
Proceeds from Divestiture of Businesses	$ 0.0	$ 0.0	$ 740.0
Accenture LLP [Member]
Commitments And Contingencies [Line Items]
Long-term purchase commitment, amount	168.0
International Business Machines Corporation [Member]
Commitments And Contingencies [Line Items]
Long-term purchase commitment, amount	$ 349.0
In re WellPoint, Inc. (n/k/a Anthem, Inc.) Out-of-Network UCR Rates Litigation [Member]
Commitments And Contingencies [Line Items]
Number of putative class actions consolidated into a single lawsuit | class_actions	11
Anthem, Inc. v. Express Scripts, Inc. [Member]
Commitments And Contingencies [Line Items]
Excess pricing assertion, remaining term of the agreement	$ 13,000.0
Excess pricing assertion, post-termination transition period	1,800.0
Loss Contingency, Damages Sought, Value	158.0
Proceeds from Divestiture of Businesses	4,675.0
General proceedings [Member]
Commitments And Contingencies [Line Items]
Possible losses, in excess of established reserves, minimum	0.0
Possible losses, in excess of established reserves, maximum	250.0
Penn Treaty [Member]
Commitments And Contingencies [Line Items]
Possible losses, in excess of established reserves, minimum	190.0
Possible losses, in excess of established reserves, maximum	$ 220.0