Quarterly report pursuant to Section 13 or 15(d)

Senior and Convertible Senior Notes (Details)

v3.3.0.814
Senior and Convertible Senior Notes (Details) - USD ($)
$ in Thousands
Sep. 30, 2015
Jun. 02, 2015
Dec. 31, 2014
Debt Instrument [Line Items]      
Senior Notes $ 1,104,060   $ 904,486
Senior Notes [Member] | 4.50% senior notes due 2018 [Member]      
Debt Instrument [Line Items]      
Long-term debt $ 175,000   $ 175,000
Debt instrument, stated rate (percentage) 4.50%   4.50%
Senior Notes [Member] | 7.15% senior notes due 2020 [Member]      
Debt Instrument [Line Items]      
Long-term debt $ 302,560   $ 302,986
Debt instrument, stated rate (percentage) 7.15%   7.15%
Unamortized premium $ 2,560   $ 2,986
Senior Notes [Member] | 7.00% senior notes due 2022 [Member]      
Debt Instrument [Line Items]      
Long-term debt $ 300,000   $ 300,000
Debt instrument, stated rate (percentage) 7.00%   7.00%
Senior Notes [Member] | 6.00% senior notes due 2025 [Member]      
Debt Instrument [Line Items]      
Long-term debt $ 200,000   $ 0
Debt instrument, stated rate (percentage) 6.00% 6.00%  
Senior Notes [Member] | 1.875% convertible senior notes due 2032 [Member]      
Debt Instrument [Line Items]      
Long-term debt [1] $ 126,500   $ 126,500
Debt instrument, stated rate (percentage) 1.875%   1.875%
[1] The Convertible Notes may be redeemed by the note-holders on the fifth, tenth and fifteenth anniversary dates of the issuance date of the Convertible Notes.