Commitments and Contingencies (Details) (USD $)	3 Months Ended	12 Months Ended									12 Months Ended
	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 AmCareco Litigation [Member]	Dec. 31, 2012 Connecticut Commercial Campus [Member]	Dec. 31, 2012 California Headquarters [Member]	Dec. 31, 2012 California Office Space [Member]	Dec. 31, 2012 Litigation Related to Information Security Issues [Member] employees_members_providers actions claims	Mar. 18, 2011 Litigation Related to Information Security Issues [Member] Customers	Dec. 31, 2012 Pharmacy and Health Quality Services [Member]	Dec. 31, 2012 IT Infrastructure Management Services [Member]	Dec. 31, 2012 Software Applications Development Services [Member]	Dec. 31, 2012 Claims Processing Services [Member]	Mar. 31, 2011 Litigation Payment [Member]	Dec. 31, 2005 Litigation Payment [Member]
Commitments and Contingencies [Line Items]
Operating Lease Agreement Term Minimum						5 years
Operating Lease Agreement Term Maximum						10 years
Remaining Operating Lease Agreement Term Minimum						4 years
Remaining Operating Lease Agreement Term Maximum						5 years
Litigation and Investigations Related to Unaccounted-for Server Drives [Abstract]
Number of pending litigations									3
Total number of people with information on drives									2,000,000
Number of pending litigations after consolidation									2
Period of free credit monitoring dervices									2 years
Estimated putative class members										800,000
Damages sought for each member in class									$ 1,000
Number of named plaintiffs' claims on which arbitration was requested									2
Number of motions for arbitration granted									1
Number of litigations matters					2
Number of separate states receivers					3
Number of health plans liquidated					3
Former subsidiary merged					1
Payments for legal settlements	177,200,000				181,000,000
Operating Leases [Abstract]
Operating lease impairment						7,400,000
Credit adjusted risk free interest rate						3.26%
Operating Lease Agreement Term							10 years	10 years
Long-Term Purchase Obligations [Abstract]
Long-term purchase commitment, amount											148,200,000	98,700,000	30,700,000	35,600,000
Remaining Long Term Purchase Obligations Term												1 year	1 year	4 years
Operating Leases, Future Minimum Commitments [Abstract]
2013		54,600,000
2014		52,700,000
2015		47,800,000
2016		40,100,000
2017		28,600,000
Thereafter		82,300,000
Total minimum commitments		306,100,000					6,700,000	104,800,000
Remaining Long Term Purchase Obligations Term Minimum											2 years
Remaining Long Term Purchase Obligations Term Maximum											4 years
Unrecorded Unconditional Purchase Obligation [Abstract]
2013		230,100,000
2014		147,800,000
2015		79,300,000
2016		17,200,000
2017		3,200,000
Thereafter		0
Total minimum commitments		477,600,000
Operating Leases and Other Purchase Obligations [Abstract]
Lease expense		47,800,000	52,100,000	61,400,000
Long-term purchase obligation expense		214,900,000	188,700,000	184,100,000
Surety Bonds [Abstract]
Maximum exposure, undiscounted																114,700,000
Standby letters of credit securing surety bonds															$ 88,100,000