Significant Accounting Policies (Details) (USD $)
12 Months Ended
Dec. 31, 2012
Dec. 31, 2014
Dec. 31, 2013
Significant Accounting Policies [Line Items]      
Amortization of intangible assets $ 8,000,000    
Goodwill 4,478,038,000 4,724,639,000 4,720,275,000
Unbilled rebates receivable   366,700,000 54,600,000
PBM      
Significant Accounting Policies [Line Items]      
Goodwill 4,458,373,000 4,704,974,000 4,700,610,000
HCIT      
Significant Accounting Policies [Line Items]      
Goodwill $ 19,665,000 19,665,000 $ 19,665,000
Minimum      
Significant Accounting Policies [Line Items]      
Finite-lived intangibles, estimated useful life   1 year  
Minimum | Customer Relationships      
Significant Accounting Policies [Line Items]      
Finite-lived intangibles, estimated useful life   3 years  
Maximum      
Significant Accounting Policies [Line Items]      
Finite-lived intangibles, estimated useful life   15 years  
Maximum | Customer Relationships      
Significant Accounting Policies [Line Items]      
Finite-lived intangibles, estimated useful life   10 years  
Furniture and equipment      
Significant Accounting Policies [Line Items]      
Property and equipment, useful Life   5 years  
Computer equipment and software | Minimum      
Significant Accounting Policies [Line Items]      
Property and equipment, useful Life   3 years  
Computer equipment and software | Maximum      
Significant Accounting Policies [Line Items]      
Property and equipment, useful Life   5 years