Receivables (Details) (USD $) | 9 Months Ended | |
|---|---|---|
Sep. 30, 2011 | Dec. 31, 2010 | |
| Receivables [Abstract] | ||
| Potential refund if performance criteria are not met | $ 16,700,000 | |
| Period of performance criteria (in years) | 15Y | |
| Accounts, Notes, Loans and Financing Receivable [Line Items] | ||
| Receivables, net | 397,633,000 | 326,543,000 |
Billed [Member] | ||
| Accounts, Notes, Loans and Financing Receivable [Line Items] | ||
| Receivables, net | 106,548,000 | 56,035,000 |
Unbilled [Member] | ||
| Accounts, Notes, Loans and Financing Receivable [Line Items] | ||
| Receivables, net | 291,085,000 | 270,508,000 |
| Period of incentive fees due (in years) | 15Y | |
| Incentive Fees Due Incrementally | $ 13,700,000 | $ 14,900,000 |