CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
PROPERTY, PLANT AND EQUIPMENT (Notes 1, 6, 9 and 10)
Accumulated depreciation of Palo Verde sale leaseback	$ 218,186	$ 213,094
Accumulated amortization on intangible assets	373,706	330,584
Accumulated amortization on nuclear fuel	$ 113,375	$ 85,270
EQUITY (Note 7)
Common stock, authorized shares	150,000,000	150,000,000
Common stock, issued shares	109,356,974	108,820,067
Treasury stock at cost, shares	111,161	50,410