Commitments and Contingencies (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended		69 Months Ended	3 Months Ended	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012 Government Contract Billing Matter	Jun. 30, 2012 State of Massachusetts Notices of Assessment	Jun. 30, 2012 Litigation
Commitments and Contingencies
Loss contingencies, reasonably possible loss exposure in excess of the amount currently accrued							$ 40,000
Total revenue billed and recorded since renewal of contract in October 2006	752,165	758,551	1,498,663	1,504,560	50,000
Notices of assessment from the state of Massachuesetts related to a corporate excise audit of the 2004 through 2006 tax years						$ 8,191