Fair Value Measurements (Details) (USD $) In Thousands	Jun. 30, 2011
Financial assets and liabilities measured at fair value on a recurring basis
Fair value, measured on recurring basis, investments	$ 26,073
Fair value, assets measured on recurring basis, derivative financial instruments, assets	10,440
Quoted Prices in Active Markets for Identical Assets (Level 1)
Financial assets and liabilities measured at fair value on a recurring basis
Fair value, measured on recurring basis, investments	26,073
Fair value, assets measured on recurring basis, derivative financial instruments, assets	0
Significant Other Observable Inputs (Level 2)
Financial assets and liabilities measured at fair value on a recurring basis
Fair value, measured on recurring basis, investments	0
Fair value, assets measured on recurring basis, derivative financial instruments, assets	10,440
Significant Unobservable Inputs (Level 3)
Financial assets and liabilities measured at fair value on a recurring basis
Fair value, measured on recurring basis, investments	0
Fair value, assets measured on recurring basis, derivative financial instruments, assets	$ 0