SCHEDULE I - Balance Sheets (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Current Assets:
Cash	$ 43,364	$ 45,748	$ 6,559	$ 23,395
Receivables, Net	765,391	792,822
Prepayments and Other Current Assets	214,288	199,947
Total Current Assets	2,087,049	2,227,295
Deferred Debits and Other Assets:
Derivative Assets Noncurrent	74,155	90,612
Other Long-Term Assets	291,537	327,766
Total Deferred Debits and Other Assets	8,132,302	9,470,519
Goodwill	3,519,401	3,519,401	300,000
Total Assets	27,795,537	28,302,824
Current Liabilities:
Notes Payable to Banks	1,093,000	1,120,196
Long-Term Debt - Current Portion	533,346	763,338
Accounts Payable - Current	742,251	764,350
Other Liabilities - Current	702,776	861,691
Total Current Liabilities	3,275,651	3,643,690
Deferred Credits and Other Liabilities:
Other Long-Term Liabilities	923,053	967,561
Total Deferred Credits and Other Liabilities	6,975,957	7,984,221
Capitalization:
Long-Term Debt	7,776,833	7,200,156
Common Shareholders' Equity:
Common Stock	1,665,351	1,662,547
Capital Surplus, Paid In	6,192,765	6,183,267
Retained Earnings	2,125,980	1,802,714
Accumulated Other Comprehensive Loss	46,031	72,854
Treasury Stock	(326,537)	(338,624)
Common Shareholders' Equity	9,611,528	9,237,050
Total Capitalization	17,543,929	16,592,774
Total Liabilities and Capitalization	27,795,537	28,302,824
Nu Parent [Member]
Current Assets:
Cash	35	429	62	268
Notes Receivable from Affiliated Companies	871,050	914,025
Receivables, Net	1	1
Accounts Receivable from Affiliated Companies	95,513	110,217
Prepayments and Other Current Assets	59,904	72,514
Total Current Assets	1,026,503	1,097,186
Deferred Debits and Other Assets:
Equity Method Investments	7,733,051	7,173,961
Notes Receivable, Related Parties, Noncurrent	62,500	25,000
Deferred Tax Assets, Net, Noncurrent	205,779	215,683
Other Long-Term Assets	22,099	17,108
Total Deferred Debits and Other Assets	11,255,240	10,663,563
Goodwill	3,231,811	3,231,811
Total Assets	12,281,743	11,760,749
Current Liabilities:
Notes Payable to Banks	1,014,500	1,150,000
Long-Term Debt - Current Portion	31,696	581,688
Accounts Payable - Current	441	9,932
Accounts Payable to Affiliated Companies	144,026	47,593
Other Liabilities - Current	59,559	41,383
Total Current Liabilities	1,250,222	1,830,596
Deferred Credits and Other Liabilities:
Other Long-Term Liabilities	122,226	114,903
Total Deferred Credits and Other Liabilities	122,226	114,903
Capitalization:
Long-Term Debt	1,297,767	578,200
Common Shareholders' Equity:
Common Stock	1,665,351	1,662,547
Capital Surplus, Paid In	6,192,765	6,183,267
Retained Earnings	2,125,980	1,802,714
Accumulated Other Comprehensive Loss	(46,031)	(72,854)
Treasury Stock	(326,537)	(338,624)
Common Shareholders' Equity	9,611,528	9,237,050
Total Capitalization	10,909,295	9,815,250
Total Liabilities and Capitalization	$ 12,281,743	$ 11,760,749