Disclosures About Fair Value Measurements (Assets And Liabilities That Are Measured At Fair Value On A Recurring Basis) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Fair Value Disclosure	$ 282	$ 278
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		334,376
Deferred Compensation Plan Assets	63,971	49,685
Assets, Fair Value Disclosure	230,344	384,339
Liabilities, Fair Value Disclosure	21,559	25,723
Recurring Measurements, (Fair Value, Total)	208,785	358,616
Commodity Derivatives [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	156,561
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	11,626	15,999
Interest Rate Derivatives [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	9,530
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	9,933	9,724
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Fair Value Disclosure	136	124
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		0
Deferred Compensation Plan Assets	63,971	49,685
Assets, Fair Value Disclosure	64,107	49,809
Liabilities, Fair Value Disclosure	0	0
Recurring Measurements, (Fair Value, Total)	64,107	49,809
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Commodity Derivatives [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	0
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	0	0
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Interest Rate Derivatives [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	0
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	0	0
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Fair Value Disclosure	146	154
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		334,376
Deferred Compensation Plan Assets	0	0
Assets, Fair Value Disclosure	166,237	334,530
Liabilities, Fair Value Disclosure	21,559	25,723
Recurring Measurements, (Fair Value, Total)	144,678	308,807
Significant Other Observable Inputs (Level 2) [Member] | Commodity Derivatives [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	156,561
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	11,626	15,999
Significant Other Observable Inputs (Level 2) [Member] | Interest Rate Derivatives [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	9,530
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	9,933	9,724
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Fair Value Disclosure	0	0
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		0
Deferred Compensation Plan Assets	0	0
Assets, Fair Value Disclosure	0	0
Liabilities, Fair Value Disclosure	0	0
Recurring Measurements, (Fair Value, Total)	0	0
Significant Unobservable Inputs (Level 3) [Member] | Commodity Derivatives [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	0
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	0	0
Significant Unobservable Inputs (Level 3) [Member] | Interest Rate Derivatives [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	0
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	$ 0	$ 0