Commitments and Contingencies (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended				75 Months Ended	3 Months Ended	1 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Litigation	Dec. 31, 2012 Government Contract Billing Matter	Sep. 30, 2012 State of Massachusetts Notices of Assessment	Nov. 30, 2011 Italy Fire item
Self-Insurance Liabilities
Self-insurance accruals	$ 34,806				$ 39,358				$ 34,806	$ 39,358
Commitments and Contingencies
Loss contingencies, reasonably possible loss exposure in excess of the amount currently accrued												37,000
Total revenue billed and recorded since renewal of contract in October 2006	758,467	748,125	752,165	746,498	741,837	768,306	758,551	746,009	3,005,255	3,014,703	2,892,349		54,000
Notices of assessment from the state of Massachusetts related to a corporate excise audit of the 2004 through 2006 tax years														$ 8,191
Number of customer lawsuits															2