Segment Information (Details) (USD $)
In Thousands, unless otherwise specified
3 Months Ended
Mar. 31, 2014
segment
Mar. 31, 2013
Dec. 31, 2013
Segment Reporting Information [Line Items]      
Number of operating segments 2    
Revenues $ 4,914,479 $ 3,219,716  
Cost of revenue 4,599,817 2,971,344  
Gross profit 314,662 248,372  
Total assets 8,794,473 7,296,794 7,995,763
P B M
     
Segment Reporting Information [Line Items]      
Revenues 4,878,375 3,181,553  
Cost of revenue 4,583,284 2,954,101  
Gross profit 295,091 227,452  
Total assets 8,392,454 7,177,351  
H C I T
     
Segment Reporting Information [Line Items]      
Revenues 36,104 38,163  
Cost of revenue 16,533 17,243  
Gross profit 19,571 20,920  
Total assets $ 402,019 $ 119,443