Segment Information (Details) (USD $)
In Thousands, unless otherwise specified
 3 Months Ended 9 Months Ended
Sep. 30, 2012
Sep. 30, 2011
Sep. 30, 2012
Sep. 30, 2011
Dec. 31, 2011
Segment Reporting Information [Line Items]          
Revenues $ 3,190,780 $ 1,287,290 $ 6,610,580 $ 3,596,981  
Cost of revenue 2,955,889 1,204,948 6,142,796 3,376,859  
Gross profit 234,891 82,342 467,784 220,122  
Total assets 7,373,208 997,098 7,373,208 997,098 1,050,307
P B M [Member]
          
Segment Reporting Information [Line Items]          
Revenues 3,150,755 1,256,369 6,493,029 3,511,148  
Cost of revenue 2,940,060 1,188,197 6,094,664 3,330,886  
Gross profit 210,695 68,172 398,365 180,262  
Total assets 7,146,899 690,445 7,146,899 690,445  
H C I T
          
Segment Reporting Information [Line Items]          
Revenues 40,025 30,921 117,551 85,833  
Cost of revenue 15,829 16,751 48,132 45,973  
Gross profit 24,196 14,170 69,419 39,860  
Total assets $ 226,309 $ 306,653 $ 226,309 $ 306,653