Segment And Geographic Information (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Revenues	$ 105,705	$ 82,692	$ 201,079	$ 164,198
Net book value	2,218,212		2,218,212		$ 2,004,961
Operating Segments [Member]
Property, Plant and Equipment [Line Items]
Revenues	105,705	$ 82,692	201,079	$ 164,198
Railcars [Member]
Property, Plant and Equipment [Line Items]
Net book value	$ 457,000		$ 457,000