Significant Customers (Details) (USD $) In Thousands, unless otherwise specified			3 Months Ended				3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2013 DHL [Member] Revenues from Leases and Contracted Services [Member] Customer Concentration Risk [Member]	Mar. 31, 2012 DHL [Member] Revenues from Leases and Contracted Services [Member] Customer Concentration Risk [Member]	Mar. 31, 2013 DHL [Member] Accounts Receivable [Member]	Dec. 31, 2012 DHL [Member] Accounts Receivable [Member]	Mar. 31, 2013 US Military [Member] Revenues from Services Performed [Member] Customer Concentration Risk [Member]	Mar. 31, 2012 US Military [Member] Revenues from Services Performed [Member] Customer Concentration Risk [Member]	Mar. 31, 2013 US Military [Member] Accounts Receivable [Member]	Dec. 31, 2012 US Military [Member] Accounts Receivable [Member]
Concentration Risk [Line Items]
Percentage of consolidated revenues			53.00%	50.00%			18.00%	17.00%
Accounts receivable	$ 43,153	$ 47,858			$ 17,100	$ 18,300			$ 4,900	$ 4,200