Summary of Significant Accounting Policies (Health Plan Services Health Care Cost) (Details) - USD ($)		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Health Care Organizations [Line Items]
Provision For Adverse Deviation		$ 74,300,000	$ 77,700,000
Liability for unpaid claims and claims adjustment expense, incurred claims, prior years	[1]	(107,400,000)	(14,600,000)	$ (56,200,000)
Prior Years Favorable Reserve Development		(29,700,000)
Prior Years Unfavorable Reserve Development			36,600,000
Provision For Adverse Deviation, Release		(77,700,000)	(51,200,000)
Premium deficiency reserve		$ 0	$ 0

[1] This line represents the change in reserves attributable to the difference between the original estimate of incurred claims for prior years and the revised estimate. Negative amounts in this line represent favorable development in estimated prior years’ health care costs. Positive amounts in this line represent unfavorable development in estimated prior years’ health care costs. For the year ended December 31, 2015, we had $107.4 million in favorable reserve developments related to prior years. This reserve development for the year ended December 31, 2015 consisted of $29.7 million in favorable prior year development and a release of $77.7 million of the provision for adverse deviation held at December 31, 2014. We believe that the $29.7 million favorable development for the year ended December 31, 2015 was primarily due to the growth of the new Medicaid expansion population in 2014. For the year ended December 31, 2014, we had $14.6 million in net favorable reserve developments related to prior years. This reserve development for the year ended December 31, 2014 consisted of $36.6 million in unfavorable prior year development primarily due to the existence of moderately adverse conditions and a release of $51.2 million of the provision for adverse deviation held at December 31, 2013. We believe that the $36.6 million unfavorable development for the year ended December 31, 2014 was primarily due to unanticipated benefit utilization in our commercial business arising from dates of service in the fourth quarter of 2013 as a result of an uncertain environment related to the ACA. The favorable development related to prior years that was recorded in the year ended December 31, 2013 resulted from claims being settled for amounts less than originally estimated. In 2013, this was primarily due to the absence of moderately adverse conditions. The favorable developments related to prior years do not directly correspond to an increase in our operating results because any favorable prior period reserve development increases current period net income only to the extent that the current period provision for adverse deviation (see footnote (f)) is less than the benefit recognized from the prior period favorable development. See Note 2 under the heading "Health Plan Services Health Care Cost" for more information.