Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Consolidated Balance Sheets [Abstract]
Securitization property	$ 1,009,103	$ 882,346
Securitization bonds	$ 1,070,556	$ 931,131
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	500,000,000	500,000,000
Common stock, shares issued	254,752,788	254,752,788
Treasury stock, shares	78,396,988	76,006,920