Commitments And Contingencies (Details) $ in Millions	3 Months Ended
	Mar. 31, 2017 USD ($)
Commitments And Contingencies [Line Items]
Gross premium tax rate, state of California	2.35%
Possible losses, in excess of established reserves, minimum	$ 0.0
Possible losses, in excess of established reserves, maximum	250.0
Anthem, Inc. v. Express Scripts, Inc. [Member]
Commitments And Contingencies [Line Items]
Excess pricing assertion, remaining term of the agreement at lawsuit filing date	13,000.0
Excess pricing assertion, post-termination transition period	1,800.0
Amount of damages sought for operational breaches	158.0
Proceeds originally received at time of divestiture	4,675.0
Penn Treaty [Member]
Commitments And Contingencies [Line Items]
Estimated liability for guaranty association assessments	$ 253.8