Significant Customers (Details) (USD $) In Thousands, unless otherwise specified			3 Months Ended				3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2014 DHL [Member] Revenues from Leases and Contracted Services [Member] Customer Concentration Risk [Member]	Mar. 31, 2013 DHL [Member] Revenues from Leases and Contracted Services [Member] Customer Concentration Risk [Member]	Mar. 31, 2014 DHL [Member] Accounts Receivable [Member]	Dec. 31, 2013 DHL [Member] Accounts Receivable [Member]	Mar. 31, 2014 US Military [Member] Revenues from Services Performed [Member] Customer Concentration Risk [Member]	Mar. 31, 2013 US Military [Member] Revenues from Services Performed [Member] Customer Concentration Risk [Member]	Mar. 31, 2014 US Military [Member] Accounts Receivable [Member]	Dec. 31, 2013 US Military [Member] Accounts Receivable [Member]
Concentration Risk [Line Items]
Percentage of consolidated revenues			56.00%	53.00%			16.00%	18.00%
Accounts receivable	$ 50,827	$ 52,247			$ 25,700	$ 24,100			$ 4,800	$ 4,800