XML 62 R47.htm IDEA: XBRL DOCUMENT v3.8.0.1
Common Shares (Narrative) (Details) - USD ($)
$ / shares in Units, $ in Thousands
 1 Months Ended 12 Months Ended
May 31, 2017
Nov. 30, 2014
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Feb. 16, 2018
May 05, 2017
Sep. 23, 2016
Aug. 31, 2015
Treasury Stock, Shares     10,073,000 10,330,000          
Treasury Stock, Value     $ 364,066 $ 373,339          
Number of common and preferred stock authorized to issue     185,000,000            
Common shares, authorized     175,000,000 175,000,000          
Preferred shares, authorized     10,000,000            
Common Stock, Shares, Outstanding     92,700,000            
Preferred Stock, Shares Outstanding     0            
Common shares issued     4,778 0 0        
Proceeds from issuance of common shares     $ 445,038 $ 0 $ 0        
Special Dividend, Per Share               $ 4.25  
2017 ATM program [Member]                  
Maximum aggregate offering price of common shares $ 315,300                
2014 ATM program [Member]                  
Maximum aggregate offering price of common shares   $ 331,300              
Maximum aggregate offering price of remaining common shares available for sale             $ 315,300    
Common shares issued     28,100            
Subsequent Event [Member] | 2017 ATM program [Member]                  
Maximum aggregate offering price of remaining common shares available for sale           $ 312,800      
April 2007 Repurchase Plan [Member]                  
Stock Repurchase Program, Authorized Amount     $ 500,000            
April 2007 Repurchase Plan [Member] | Subsequent Event [Member]                  
Stock Repurchase Program, Remaining Authorized Repurchase Amount           $ 269,800      
2017 equity offering [Member]                  
Common shares issued     4,800,000            
Proceeds from issuance of common shares     $ 442,500            
Unsecured Credit Facility [Member]                  
Line of Credit Facility, Current Borrowing Capacity     $ 600,000           $ 500,000