Significant Customers (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Concentration Risk [Line Items]
Accounts receivable	$ 52,247	$ 47,858
DHL [Member] | Revenues from Leases and Contracted Services [Member] | Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Percentage of consolidated revenues	54.00%	53.00%	36.00%
DHL [Member] | Accounts Receivable [Member]
Concentration Risk [Line Items]
Accounts receivable	24,100	18,300
BAX/Schenker [Member] | Revenues from Services Performed [Member] | Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Percentage of consolidated revenues	0.00%		26.00%
BAX/Schenker [Member] | Accounts Receivable [Member]
Concentration Risk [Line Items]
Accounts receivable	0
US Military [Member] | Revenues from Services Performed [Member] | Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Percentage of consolidated revenues	17.00%	16.00%	12.00%
US Military [Member] | Accounts Receivable [Member]
Concentration Risk [Line Items]
Accounts receivable	$ 4,800	$ 4,200