Annual report pursuant to Section 13 and 15(d)

Debt (Details 3)

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Debt (Details 3) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2011
Dec. 31, 2010
Carrying amount and estimated fair value of debt    
Debt, net $ 2,426,303 $ 2,323,681
Carrying Amount
   
Carrying amount and estimated fair value of debt    
Fixed-rate debt 1,284,754 1,559,034
Variable- rate debt 1,141,549 764,647
Debt, net 2,426,303 2,323,681
Total Estimated Fair Value
   
Carrying amount and estimated fair value of debt    
Fixed-rate debt 1,292,501 1,579,022
Variable- rate debt 1,139,856 769,247
Debt, net $ 2,432,357 $ 2,348,269