Quarterly report pursuant to Section 13 or 15(d)

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

 v2.3.0.11
Senior Unsecured Notes (Summary Of Senior Unsecured Notes) (Details) (USD $)
In Thousands, unless otherwise specified
 6 Months Ended
Jun. 30, 2011
Dec. 31, 2010
Senior unsecured notes $ 1,118,859 $ 1,118,451
5.250% Senior Unsecured Notes, Due January 15, 2012 [Member]
    
Senior unsecured notes 99,890 99,793
Effective Rate 5.457% [1]  
Interest rate of the senior unsecured notes 5.25%  
Maturity date of the senior unsecured notes Jan. 15, 2012  
6.150% Senior Unsecured Notes, Due December 15, 2012 [Member]
    
Senior unsecured notes 94,192 93,946
Effective Rate 6.894% [1]  
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]
    
Senior unsecured notes 25,917 25,861
Effective Rate 6.448% [1]  
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]
    
Senior unsecured notes 99,944 99,930
Effective Rate 4.742% [1]  
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]
    
Senior unsecured notes 200,629 200,749
Effective Rate 5.11% [1]  
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]
    
Senior unsecured notes 149,671 149,625
Effective Rate 5.297% [1]  
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]
    
Senior unsecured notes 200,351 200,389
Effective Rate 5.806% [1]  
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]
    
Senior unsecured notes $ 248,265 $ 248,158
Effective Rate 8.017% [1]  
Interest rate of the senior unsecured notes 7.75%  
Maturity date of the senior unsecured notes Aug. 15, 2019  
[1] Includes the cost of terminated treasury lock agreements (if any), offering and other transaction costs and the discount/premium on the notes, as applicable.