CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
PROPERTY, PLANT AND EQUIPMENT (Notes 1, 6 and 10)
Accumulated depreciation of Palo Verde sale leaseback	$ 222,055	$ 218,186
Accumulated amortization on intangible assets	411,543	373,706
Accumulated amortization on nuclear fuel	$ 133,950	$ 113,375
EQUITY (Note 7)
Common stock, authorized shares	150,000,000	150,000,000
Common stock, issued shares	109,837,957	109,356,974
Treasury stock at cost, shares	95,192	111,161