Segment Information (Narrative) (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2017 USD ($) segments	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Segment Reporting Information [Line Items]
REVENUES	$ 322,971	$ 254,101	$ 253,211	$ 237,917	$ 221,675	$ 193,261	$ 176,549	$ 177,385	$ 1,068,200	$ 768,870	$ 619,264
Number of reportable segments (in segments) | segments									3
Interest expense									$ 17,023	11,318	11,232
Customer Revenues [Member]
Segment Reporting Information [Line Items]
REVENUES									$ 1,068,200	$ 768,870	$ 619,264
Schedule of Revenue from External Customers and Long-Lived Assets, by Geographical Areas [Table Text Block]									170100	168221	206484
ACMI Services [Member]
Segment Reporting Information [Line Items]
REVENUES									$ 614,741	$ 492,859	$ 433,109
Property, Plant and Equipment, Additions									28,700
ACMI Services [Member] | Customer Revenues [Member]
Segment Reporting Information [Line Items]
REVENUES									614,721	492,859	431,989
CAM [Member]
Segment Reporting Information [Line Items]
REVENUES									209,560	195,092	177,789
Interest expense									15,600	10,600	9,400
Property, Plant and Equipment, Additions									283,800
CAM [Member] | Customer Revenues [Member]
Segment Reporting Information [Line Items]
REVENUES									140,434	117,642	93,395
Ground Services [Member]
Segment Reporting Information [Line Items]
REVENUES									206,631	116,796	60,163
Property, Plant and Equipment, Additions									2,900
Ground Services [Member] | Customer Revenues [Member]
Segment Reporting Information [Line Items]
REVENUES									$ 204,150	$ 114,813	$ 58,160