Significant Customers (Details) (USD $) In Thousands, unless otherwise specified			3 Months Ended		6 Months Ended				3 Months Ended		6 Months Ended
	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2013 DHL [Member] Revenues from Leases and Contracted Services [Member] Customer Concentration Risk [Member]	Jun. 30, 2012 DHL [Member] Revenues from Leases and Contracted Services [Member] Customer Concentration Risk [Member]	Jun. 30, 2013 DHL [Member] Revenues from Leases and Contracted Services [Member] Customer Concentration Risk [Member]	Jun. 30, 2012 DHL [Member] Revenues from Leases and Contracted Services [Member] Customer Concentration Risk [Member]	Jun. 30, 2013 DHL [Member] Accounts Receivable [Member]	Dec. 31, 2012 DHL [Member] Accounts Receivable [Member]	Jun. 30, 2013 US Military [Member] Revenues from Services Performed [Member] Customer Concentration Risk [Member]	Jun. 30, 2012 US Military [Member] Revenues from Services Performed [Member] Customer Concentration Risk [Member]	Jun. 30, 2013 US Military [Member] Revenues from Services Performed [Member] Customer Concentration Risk [Member]	Jun. 30, 2012 US Military [Member] Revenues from Services Performed [Member] Customer Concentration Risk [Member]	Jun. 30, 2013 US Military [Member] Accounts Receivable [Member]	Dec. 31, 2012 US Military [Member] Accounts Receivable [Member]
Concentration Risk [Line Items]
Percentage of consolidated revenues			56.00%	54.00%	54.00%	52.00%			16.00%	16.00%	17.00%	16.00%
Accounts receivable	$ 43,840	$ 47,858					$ 19,400	$ 18,300					$ 3,700	$ 4,200