General (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2015 USD ($) item	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($) segment multiplier item	Jun. 30, 2014 USD ($)
Operating results by business segment
Number of segments | segment			5
Revenues	$ 1,157,607,000	$ 888,014,000	$ 2,138,575,000	$ 1,854,489,000
Commercial | Risk Based Product
Operating results by business segment
Covered Lives | item	2,600,000		2,600,000
Revenues			$ 138,800,000
Commercial | ASO (Administrative Services Only)
Operating results by business segment
Covered Lives | item	12,700,000		12,700,000
Revenues			$ 62,100,000
Commercial | EAP (Employee Assistance Programs)
Operating results by business segment
Covered Lives | item	13,400,000		13,400,000
Revenues			$ 102,300,000
Public Sector | Risk Based Product
Operating results by business segment
Covered Lives | item	1,500,000		1,500,000
Revenues			$ 832,500,000
Public Sector | ASO (Administrative Services Only)
Operating results by business segment
Covered Lives | item	1,800,000		1,800,000
Revenues			$ 30,300,000
Specialty Solutions | Risk Based Product
Operating results by business segment
Covered Lives | item	7,400,000		7,400,000
Revenues			$ 228,400,000
Specialty Solutions | ASO (Administrative Services Only)
Operating results by business segment
Covered Lives | item	16,200,000		16,200,000
Revenues			$ 28,200,000
Pharmacy Management
Operating results by business segment
Number of multiple applied for adjusted claim | multiplier			3
Number of days for applying the multiple			90 days
Pharmacy Management | PBM (Pharmacy Benefit Management)
Operating results by business segment
Adjusted claims paid			$ 8,100,000
Pharmacy Management | PBA (Pharmacy Benefit Administration)
Operating results by business segment
Adjusted claims paid			$ 29,500,000
Number of states served | item	25		25
Pharmacy Management | Specialty Dispensing
Operating results by business segment
Adjusted claims paid			$ 52,400
Pharmacy Management | Commercial PBM
Operating results by business segment
Generic dispensing rate (as a percent)			84.00%
Number of members served | item			1,600,000
Pharmacy Management | Medical pharmacy management programs
Operating results by business segment
Number of members served | item			10,000,000
Managed Healthcare
Operating results by business segment
Number of segments | segment			2