Annual report pursuant to Section 13 and 15(d)

Senior Unsecured Notes (Narrative) (Details)

v3.3.1.900
Senior Unsecured Notes (Narrative) (Details)
$ in Thousands
 12 Months Ended
Jan. 07, 2016
USD ($)
item
Dec. 31, 2015
USD ($)
Dec. 31, 2014
USD ($)
Dec. 31, 2013
USD ($)
Debt Instrument [Line Items]        
Senior Unsecured Notes   $ 1,268,844 $ 1,267,744  
Repayments of senior unsecured notes     350,000 $ 100,000
3.12% Senior Unsecured Notes Due January 2019 [Member]        
Debt Instrument [Line Items]        
Maturity date of the senior unsecured notes   Jan. 01, 2019    
5.800% Senior Unsecured Notes, Due January 15, 2016 [Member]        
Debt Instrument [Line Items]        
Senior Unsecured Notes [1]   $ 200,010 $ 200,086  
Interest rate of senior unsecured notes [1]   5.80%    
Maturity date of the senior unsecured notes [1]   Jan. 15, 2016    
Subsequent Event [Member] | 3.12% Senior Unsecured Notes Due January 2019 [Member]        
Debt Instrument [Line Items]        
Senior Unsecured Notes $ 350,000      
Interest rate of senior unsecured notes 3.12%      
Number of extension options | item 2      
Loan extension period 1 year      
Spread over LIBOR 1.40%      
Subsequent Event [Member] | 5.800% Senior Unsecured Notes, Due January 15, 2016 [Member]        
Debt Instrument [Line Items]        
Repayments of senior unsecured notes $ 200,000      
[1] On January 15, 2016, the Company repaid these notes at their maturity using proceeds from a new unsecured term loan and borrowings under the Company's unsecured revolving credit facility.