Receivables (Details) (USD $)	3 Months Ended
	Mar. 31, 2012	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivables	$ 420,350,000	$ 333,467,000
Period of performance criteria (in years)	15Y
Potential refund if performance criteria are not met	14,000,000
Billed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivables	59,330,000	77,505,000
Unbilled [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivables	361,020,000	255,962,000
Incentive fees due incrementally	9,900,000	10,200,000
Period of incentive fees due (in years)	15Y
Receivables pertaining to the Commercial Resupply Services contract	$ 204,800,000	$ 130,400,000