Segment Information (Details) (USD $)
In Thousands, unless otherwise specified
3 Months Ended
Mar. 31, 2013
segment
Mar. 31, 2012
Dec. 31, 2012
Segment Reporting Information [Line Items]      
Number of operating segments 2    
Revenues $ 3,219,716 $ 1,717,097  
Cost of revenue 2,971,344 1,606,708  
Gross profit 248,372 110,389  
Total assets 7,296,794 1,284,131 7,385,127
P B M
     
Segment Reporting Information [Line Items]      
Revenues 3,181,553 1,681,145  
Cost of revenue 2,954,101 1,590,189  
Gross profit 227,452 90,956  
Total assets 7,177,351 1,024,253  
H C I T
     
Segment Reporting Information [Line Items]      
Revenues 38,163 35,952  
Cost of revenue 17,243 16,519  
Gross profit 20,920 19,433  
Total assets $ 119,443 $ 259,878