Annual report pursuant to Section 13 and 15(d)

Senior Unsecured Notes (Summary Of Senior Unsecured Notes) (Details)

v2.4.0.6
Senior Unsecured Notes (Summary Of Senior Unsecured Notes) (Details) (USD $)
In Thousands, unless otherwise specified
 12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Long-Term Debt [Line Items]    
Senior Unsecured Notes $ 1,119,267 $ 1,118,451
5.250% Senior Unsecured Notes, Due January 15, 2012 [Member]
    
Long-Term Debt [Line Items]    
Senior Unsecured Notes 99,988 [1] 99,793 [1]
Effective Rate 5.457% [1],[2]  
Interest rate of the Senior Unsecured Notes 5.25% [1]  
Maturity date of the Senior Unsecured Notes Jan. 15, 2012 [1]  
6.150% Senior Unsecured Notes, Due December 15, 2012 [Member]
    
Long-Term Debt [Line Items]    
Senior Unsecured Notes 94,438 93,946
Effective Rate 6.894% [2]  
Interest rate of the Senior Unsecured Notes 6.15%  
Maturity date of the Senior Unsecured Notes Dec. 15, 2012  
5.820% Senior Unsecured Notes, Due March 15, 2013 [Member]
    
Long-Term Debt [Line Items]    
Senior Unsecured Notes 25,972 25,861
Effective Rate 6.448% [2]  
Interest rate of the Senior Unsecured Notes 5.82%  
Maturity date of the Senior Unsecured Notes Mar. 15, 2013  
4.600% Senior Unsecured Notes, Due June 15, 2013 [Member]
    
Long-Term Debt [Line Items]    
Senior Unsecured Notes 99,958 99,930
Effective Rate 4.742% [2]  
Interest rate of the Senior Unsecured Notes 4.60%  
Maturity date of the Senior Unsecured Notes Jun. 15, 2013  
5.125% Senior Unsecured Notes, Due February 15, 2014 [Member]
    
Long-Term Debt [Line Items]    
Senior Unsecured Notes 200,509 200,749
Effective Rate 5.11% [2]  
Interest rate of the Senior Unsecured Notes 5.125%  
Maturity date of the Senior Unsecured Notes Feb. 15, 2014  
5.125% Senior Unsecured Notes, Due January 15, 2015 [Member]
    
Long-Term Debt [Line Items]    
Senior Unsecured Notes 149,717 149,625
Effective Rate 5.297% [2]  
Interest rate of the Senior Unsecured Notes 5.125%  
Maturity date of the Senior Unsecured Notes Jan. 15, 2015  
5.800% Senior Unsecured Notes, Due January 15, 2016 [Member]
    
Long-Term Debt [Line Items]    
Senior Unsecured Notes 200,313 200,389
Effective Rate 5.806% [2]  
Interest rate of the Senior Unsecured Notes 5.80%  
Maturity date of the Senior Unsecured Notes Jan. 15, 2016  
7.750% Senior Unsecured Notes, Due August 15, 2019 [Member]
    
Long-Term Debt [Line Items]    
Senior Unsecured Notes $ 248,372 $ 248,158
Effective Rate 8.017% [2]  
Interest rate of the Senior Unsecured Notes 7.75%  
Maturity date of the Senior Unsecured Notes Aug. 15, 2019  
[1] These notes were paid at maturity, primarily from borrowing on the Company's unsecured revolving credit facility.
[2] Includes the cost of terminated treasury lock agreements (if any), offering and other transaction costs and the discount/premium on the notes, as applicable.