v2.4.0.6
Goodwill, transmission system rights, power purchase agreements and development intangible assets and liabilities (Details 3) (USD $)
In Thousands, unless otherwise specified
12 Months Ended
Dec. 31, 2012
Weighted average remaining amortization period related to our intangible assets  
Weighted average remaining amortization period 9 years
Power Purchase Agreements
 
Estimated future amortization  
2013 60,199
2014 60,527
2015 56,802
2016 56,802
2017 56,802
Weighted average remaining amortization period related to our intangible assets  
Weighted average remaining amortization period 9 years
Fuel Supply Agreements
 
Estimated future amortization  
2013 (1,173)
2014 (1,173)
2015 (1,173)
2016 (1,173)
2017 (1,173)
Weighted average remaining amortization period related to our intangible assets  
Weighted average remaining amortization period 10 years