Equipment Acquisitions, Dispositions and Depreciation and Impairment Policies (Narrative) (Details) $ in Thousands	3 Months Ended
	Jun. 30, 2016 USD ($) equipment	Mar. 31, 2016 USD ($) equipment	Mar. 31, 2015 USD ($)
Property, Plant and Equipment [Line Items]
Payments to Acquire Property, Plant, and Equipment | $		$ 47,436	$ 47,430
Sales Price Of Equipment | $		100
Amortization Of Deferred Gains Included In Gains On Asset Dispositions And Impairments, Net | $		$ 1,707	0
Wind Farm Utility Vessel [Member]
Property, Plant and Equipment [Line Items]
Number Of Equipments Delivered | equipment		1
Gain (Loss) on Asset Dispositions and Impairments, Net [Member]
Property, Plant and Equipment [Line Items]
Amortization Of Deferred Gains Included In Gains On Asset Dispositions And Impairments, Net | $		$ 623	$ 1,048
Subsequent Event [Member]
Property, Plant and Equipment [Line Items]
Sales Price Of Equipment | $	$ 90,000
Subsequent Event [Member] | Inland River Towboat [Member]
Property, Plant and Equipment [Line Items]
Number Of Equipments Sold | equipment	14
Number of Equipment Under Construction | equipment	1
Subsequent Event [Member] | Inland River Liquid Tank Barges - 30,000 Barrel [Member]
Property, Plant and Equipment [Line Items]
Number Of Equipments Sold | equipment	20
Number of Equipment Under Construction | equipment	1