Goodwill and Other Intangible Assets (Goodwill) (Details) (USD $)
In Thousands, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Goodwill [Roll Forward]    
Goodwill, beginning of period $ 4,720,275 $ 4,478,038
Acquisitions 2,026 225,761
Measurement periods adjustments 2,338 16,476
Goodwill, end of period 4,724,639 4,720,275
PBM    
Goodwill [Roll Forward]    
Goodwill, beginning of period 4,700,610 4,458,373
Acquisitions 2,026 225,761
Measurement periods adjustments 2,338 16,476
Goodwill, end of period 4,704,974 4,700,610
HCIT    
Goodwill [Roll Forward]    
Goodwill, beginning of period 19,665 19,665
Acquisitions 0 0
Measurement periods adjustments 0 0
Goodwill, end of period $ 19,665 $ 19,665