Segment Information (Entity-Wide Disclosures) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Customer revenues	$ 157,938	$ 138,443	$ 149,618	$ 143,593	$ 156,963	$ 140,877	$ 138,904	$ 143,279	$ 589,592	$ 580,023	$ 607,438
Customer Revenues [Member]
Segment Reporting Information [Line Items]
Customer revenues									589,592	580,023	607,438
All other [Member]
Segment Reporting Information [Line Items]
Customer revenues									142,294	117,292	112,343
All other [Member] | Customer Revenues [Member]
Segment Reporting Information [Line Items]
Customer revenues									72,005	63,915	55,117
Aircraft maintenance and part sales [Member] | All other [Member] | Customer Revenues [Member]
Segment Reporting Information [Line Items]
Customer revenues									26,393	23,175	21,669
Mail handling services [Member] | All other [Member] | Customer Revenues [Member]
Segment Reporting Information [Line Items]
Customer revenues									34,025	30,117	23,671
Facility and ground equipment maintenance [Member] | All other [Member] | Customer Revenues [Member]
Segment Reporting Information [Line Items]
Customer revenues									11,119	10,030	8,304
Other [Member] | All other [Member] | Customer Revenues [Member]
Segment Reporting Information [Line Items]
Customer revenues									$ 468	$ 593	$ 1,473