GENERAL AND BASIS OF PRESENTATION Additional Information (Detail) (USD $)							3 Months Ended		6 Months Ended			3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended
	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2011 Domestic Country Entity	Dec. 31, 2010 Domestic Country Entity	Jun. 30, 2011 Foreign Country	Dec. 31, 2010 Foreign Country	Jun. 30, 2011 Southern California Edison Company	Jun. 30, 2010 Southern California Edison Company	Jun. 30, 2011 Southern California Edison Company	Jun. 30, 2010 Southern California Edison Company	Aug. 02, 2010 Mammoth Complex	Jun. 30, 2011 Sierra Pacific Power Company And Nevada Power Company	Jun. 30, 2010 Sierra Pacific Power Company And Nevada Power Company	Jun. 30, 2011 Sierra Pacific Power Company And Nevada Power Company	Jun. 30, 2010 Sierra Pacific Power Company And Nevada Power Company	Jun. 30, 2011 Hawaii Electric Light Company	Jun. 30, 2010 Hawaii Electric Light Company	Jun. 30, 2011 Hawaii Electric Light Company	Jun. 30, 2010 Hawaii Electric Light Company	Jun. 30, 2011 Kenya Power And Lighting Co LTD	Jun. 30, 2010 Kenya Power And Lighting Co LTD	Jun. 30, 2011 Kenya Power And Lighting Co LTD	Jun. 30, 2010 Kenya Power And Lighting Co LTD
Basis of Presentation [Line Items]
Cash deposit in financial institution			$ 17,247,000	$ 55,537,000	$ 33,166,000	$ 37,929,000
Number of financial institutions used for deposit			7	7
Federal insurance of financial institution per account			250,000	250,000
Accounts receivable related to operations in foreign countries	$ 72,185,000	$ 54,495,000			$ 42,230,000	$ 26,128,000
Percentage of receivable from major customers that generated 10% or more of revenues	41.00%	40.00%
Percentage of total revenue							29.50%	25.50%	28.30%	25.50%		12.00%	13.70%	14.10%	16.20%	11.80%	8.00%	11.20%	7.60%	8.40%	9.20%	8.60%	9.90%
Acquired ownership interest											50.00%