Fair Value Measurements (Details) (USD $) In Thousands	Jun. 30, 2011
Fair Value Hierarchy Table for Assets and Liabilities Measured at Fair Value
Derivative assets liabilities at fair value net	$ 61,100
Fair Value, Measurements, Recurring [Member]
Fair Value Hierarchy Table for Assets and Liabilities Measured at Fair Value
Trading securities held in our deferred compensation plans	52,129
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets [Member]
Fair Value Hierarchy Table for Assets and Liabilities Measured at Fair Value
Trading securities held in our deferred compensation plans	52,129
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets [Member] | Call Option [Member]
Fair Value Hierarchy Table for Assets and Liabilities Measured at Fair Value
Derivative assets liabilities at fair value net	0
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets [Member] | Collars [Member]
Fair Value Hierarchy Table for Assets and Liabilities Measured at Fair Value
Derivative assets liabilities at fair value net	0
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets [Member] | Swap [Member]
Fair Value Hierarchy Table for Assets and Liabilities Measured at Fair Value
Derivative assets liabilities at fair value net	0
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs [Member]
Fair Value Hierarchy Table for Assets and Liabilities Measured at Fair Value
Trading securities held in our deferred compensation plans	0
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs [Member] | Call Option [Member]
Fair Value Hierarchy Table for Assets and Liabilities Measured at Fair Value
Derivative assets liabilities at fair value net	(51,351)
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs [Member] | Collars [Member]
Fair Value Hierarchy Table for Assets and Liabilities Measured at Fair Value
Derivative assets liabilities at fair value net	94,507
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs [Member] | Swap [Member]
Fair Value Hierarchy Table for Assets and Liabilities Measured at Fair Value
Derivative assets liabilities at fair value net	17,934
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs [Member]
Fair Value Hierarchy Table for Assets and Liabilities Measured at Fair Value
Trading securities held in our deferred compensation plans	0
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs [Member] | Call Option [Member]
Fair Value Hierarchy Table for Assets and Liabilities Measured at Fair Value
Derivative assets liabilities at fair value net	0
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs [Member] | Collars [Member]
Fair Value Hierarchy Table for Assets and Liabilities Measured at Fair Value
Derivative assets liabilities at fair value net	0
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs [Member] | Swap [Member]
Fair Value Hierarchy Table for Assets and Liabilities Measured at Fair Value
Derivative assets liabilities at fair value net	0
Fair Value, Measurements, Recurring [Member] | Call Option [Member]
Fair Value Hierarchy Table for Assets and Liabilities Measured at Fair Value
Derivative assets liabilities at fair value net	(51,351)
Fair Value, Measurements, Recurring [Member] | Collars [Member]
Fair Value Hierarchy Table for Assets and Liabilities Measured at Fair Value
Derivative assets liabilities at fair value net	94,507
Fair Value, Measurements, Recurring [Member] | Swap [Member]
Fair Value Hierarchy Table for Assets and Liabilities Measured at Fair Value
Derivative assets liabilities at fair value net	$ 17,934