Accumulated depreciation and amortization (Tables)

3 Months Ended

Mar. 31, 2012

Accumulated depreciation and amortization

Schedule of accumulated depreciation and amortization

	March 31, 2012		December 31, 2011
Property, plant and equipment	$	132,208	$	116,287
Transmission system rights		53,350		51,387
Other intangible assets and power purchase and fuel liabilities		110,752		88,808