CONSOLIDATED STATEMENTS OF CAPITALIZATION (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011		Dec. 31, 2010
Long-Term Debt
Unamortized discount	$ (8,349)		$ (8,250)
Total long-term debt	3,486,275		3,235,223
Long-term debt, current maturities	605,633		6,970
Long-term debt, noncurrent	2,880,642		3,228,253
Common Stockholder's Equity
Common stock - 100 shares authorized of $0.01 par value, 100 shares outstanding at Dec. 31, 2011 and 2010, respectively	0		0
Additional paid in capital	3,316,386		3,255,586
Retained earnings	1,001,709		875,151
Accumulated other comprehensive (loss) income	(12,377)		7,457
Total common stockholder's equity	4,305,718		4,138,194
First Mortgage Bonds [Member] | Series Due Oct. 1, 2012 [Member]
Long-Term Debt
Long-term debt, gross	600,000		600,000
First Mortgage Bonds [Member] | Series Due March 1, 2013 [Member]
Long-Term Debt
Long-term debt, gross	250,000		250,000
First Mortgage Bonds [Member] | Series Due April 1, 2014 [Member]
Long-Term Debt
Long-term debt, gross	275,000		275,000
First Mortgage Bonds [Member] | Series Due Sept. 1, 2017 [Member]
Long-Term Debt
Long-term debt, gross	129,500	[1]	129,500	[1]
First Mortgage Bonds [Member] | Series Due Aug. 1, 2018 [Member]
Long-Term Debt
Long-term debt, gross	300,000		300,000
First Mortgage Bonds [Member] | Series Due Jan. 1, 2019 [Member]
Long-Term Debt
Long-term debt, gross	48,750	[1]	48,750	[1]
First Mortgage Bonds [Member] | Series Due June 1, 2019 [Member]
Long-Term Debt
Long-term debt, gross	400,000		400,000
First Mortgage Bonds [Member] | Series Due Nov. 15, 2020 [Member]
Long-Term Debt
Long-term debt, gross	400,000		400,000
First Mortgage Bonds [Member] | Series Due Sept. 1, 2037 [Member]
Long-Term Debt
Long-term debt, gross	350,000		350,000
First Mortgage Bonds [Member] | Series Due Aug. 1, 2038 [Member]
Long-Term Debt
Long-term debt, gross	300,000		300,000
First Mortgage Bonds [Member] | Series Due Aug. 15, 2041 [Member]
Long-Term Debt
Long-term debt, gross	250,000		0
Capital Lease Obligations [Member]
Long-Term Debt
Capital lease obligations	$ 191,374		$ 190,223

[1] Pollution control financing