Quarterly report pursuant to Section 13 or 15(d)

FAIR VALUE DISCLOSURES - Schedule of Fair Value of Fixed-Rate Debt (Details)

v3.8.0.1
FAIR VALUE DISCLOSURES - Schedule of Fair Value of Fixed-Rate Debt (Details) - Senior Notes [Member] - USD ($)
Sep. 30, 2017
Jun. 06, 2017
Dec. 31, 2016
4.50% senior notes due 2018 [Member]      
Fair value of fixed-rate debt      
Stated interest rate 4.50%   4.50%
4.50% senior notes due 2018 [Member] | Level 2 [Member]      
Debt Instrument [Line Items]      
Aggregate Principal $ 175,000,000   $ 175,000,000
Fair value of fixed-rate debt      
Estimated Fair Value $ 175,875,000   $ 177,625,000
7.15% senior notes due 2020 [Member]      
Fair value of fixed-rate debt      
Stated interest rate 7.15%   7.15%
7.15% senior notes due 2020 [Member] | Level 2 [Member]      
Debt Instrument [Line Items]      
Aggregate Principal $ 300,000,000   $ 300,000,000
Fair value of fixed-rate debt      
Estimated Fair Value $ 330,000,000   $ 325,500,000
7.00% senior notes due 2022 [Member]      
Fair value of fixed-rate debt      
Stated interest rate 7.00%   7.00%
7.00% senior notes due 2022 [Member] | Level 2 [Member]      
Debt Instrument [Line Items]      
Aggregate Principal $ 300,000,000   $ 300,000,000
Fair value of fixed-rate debt      
Estimated Fair Value $ 342,750,000   $ 324,750,000
6.00% senior notes due 2025 [Member]      
Fair value of fixed-rate debt      
Stated interest rate 6.00%   6.00%
6.00% senior notes due 2025 [Member] | Level 2 [Member]      
Debt Instrument [Line Items]      
Aggregate Principal $ 200,000,000   $ 200,000,000
Fair value of fixed-rate debt      
Estimated Fair Value $ 213,000,000   202,500,000
5.125% senior notes due 2027 [Member]      
Debt Instrument [Line Items]      
Aggregate Principal   $ 300,000,000  
Fair value of fixed-rate debt      
Stated interest rate 5.125% 5.125%  
5.125% senior notes due 2027 [Member] | Level 2 [Member]      
Debt Instrument [Line Items]      
Aggregate Principal $ 300,000,000   0
Fair value of fixed-rate debt      
Estimated Fair Value $ 300,750,000   $ 0
1.875% convertible senior notes due 2032 [Member]      
Fair value of fixed-rate debt      
Stated interest rate 1.875%   1.875%
1.875% convertible senior notes due 2032 [Member] | Level 2 [Member]      
Debt Instrument [Line Items]      
Aggregate Principal $ 0   $ 126,500,000
Fair value of fixed-rate debt      
Estimated Fair Value $ 0   $ 126,105,000