Summary of Significant Accounting Policies (PPE Useful Lives) (Details)	12 Months Ended
	Mar. 31, 2016
Land improvements | Minimum
Depreciation using the straight-line method
Property, plant and equipment, useful life	10 years
Land improvements | Maximum
Depreciation using the straight-line method
Property, plant and equipment, useful life	15 years
Buildings and building improvements | Minimum
Depreciation using the straight-line method
Property, plant and equipment, useful life	3 years
Buildings and building improvements | Maximum
Depreciation using the straight-line method
Property, plant and equipment, useful life	39 years
Furniture, fixtures and office equipment | Minimum
Depreciation using the straight-line method
Property, plant and equipment, useful life	2 years
Furniture, fixtures and office equipment | Maximum
Depreciation using the straight-line method
Property, plant and equipment, useful life	10 years
Equipment leased to customers under Power Purchase Agreements
Depreciation using the straight-line method
Property, plant and equipment, useful life	20 years
Plant equipment | Minimum
Depreciation using the straight-line method
Property, plant and equipment, useful life	3 years
Plant equipment | Maximum
Depreciation using the straight-line method
Property, plant and equipment, useful life	10 years