|
Risk Management Activities (Narrative) (Details) (USD $)
|
0 Months Ended | 6 Months Ended | 6 Months Ended | 12 Months Ended | 6 Months Ended | 12 Months Ended | 6 Months Ended | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
Sep. 16, 2005
|
Jul. 22, 2003
|
Jun. 30, 2013
|
Jun. 30, 2012
|
Dec. 31, 2012
|
Jun. 30, 2013
Physical Sales Contracts Marked-To-Market [Member]
|
Dec. 31, 2012
Physical Sales Contracts Marked-To-Market [Member]
|
Jun. 30, 2013
Financial Derivative Contracts Marked To Market [Member]
|
Dec. 31, 2012
Financial Derivative Contracts Marked To Market [Member]
|
Sep. 16, 2005
5.25% - Due September 15, 2017 [Member]
|
Sep. 16, 2005
5.45% - Due September 15, 2020 [Member]
|
Jun. 30, 2013
Millennium Pipeline Company, L.L.C [Member]
|
Jun. 30, 2012
Millennium Pipeline Company, L.L.C [Member]
|
|
| Derivative Instruments Gain Loss [Line Items] | |||||||||||||
| Gain (Loss) on Cash Flow Hedge Ineffectiveness, Net | $ 0 | $ 0 | |||||||||||
| Additional Collateral, Aggregate Fair Value | 800,000 | ||||||||||||
| Face amount of notes | 1,000,000,000 | 1,000,000,000 | |||||||||||
| Reserves against physical sale contract derivatives | 300,000 | 700,000 | |||||||||||
| Fair value of physical sales contracts and derivative contracts | 14,700,000 | 35,400,000 | (15,000,000) | (33,200,000) | |||||||||
| Outstanding debt | 7,400,000,000 | ||||||||||||
| Outstanding debt subject to interest rate fluctuations | 500,000,000 | ||||||||||||
| Derivative, Notional Amount | 900,000,000 | 500,000,000 | |||||||||||
| Number of counterparties in swap agreement | 4 | ||||||||||||
| Fixed interest rate under swap agreement | 5.40% | ||||||||||||
| Floating interest amount, average interest addition | 0.78% | ||||||||||||
| Number of counterparties in swap agreement settled | 6 | ||||||||||||
| Payment for settlement of interest rate swap | 35,500,000 | ||||||||||||
| Forward starting interest rate swap settlement amount | 9,000,000 | ||||||||||||
| Percentage of interest in Millennium | 47.50% | 47.50% | |||||||||||
| Loss recognized in income statement classified in accumulated other comprehensive income(loss) | 0 | ||||||||||||
| Cash on deposit with brokers for margin requirements | 27,700,000 | 45,700,000 | |||||||||||
| Interest rate on debt | 5.25% | 5.45% | |||||||||||
| Debt Instrument, Interest Rate, Effective Percentage | 5.67% | 5.88% | |||||||||||
| Other Comprehensive Income Unrecognized Gain Loss On Derivatives Arising During Period Net Of Tax | $ 18,200,000 | $ 18,700,000 | |||||||||||