XML 40 R29.htm IDEA: XBRL DOCUMENT v3.7.0.1
Debt (Details) - USD ($)
Mar. 31, 2017
Feb. 28, 2017
Dec. 31, 2016
Debt Instrument [Line Items]      
Maximum borrowing capacity   $ 300,000,000  
Line of credit facility, accordion feature   $ 100,000,000  
Long-term Debt, Gross $ 1,300,000,000   $ 1,300,000,000
Unamortized debt issuance costs 13,790,000   15,400,000
Total debt, net 1,286,210,000   1,284,600,000
Unsecured Senior Notes Due 2019 [Member]      
Debt Instrument [Line Items]      
Senior Notes $ 500,000,000    
Stated interest rate on unsecured senior notes 6.375%    
Long-term Debt, Gross     $ 500,000,000
Unsecured Senior Notes Due 2021 [Member]      
Debt Instrument [Line Items]      
Senior Notes $ 800,000,000    
Stated interest rate on unsecured senior notes 7.125%   7.125%
Long-term Debt, Gross $ 800,000,000   $ 800,000,000