Quarterly report pursuant to Section 13 or 15(d)

Condensed Consolidating Financial Information (Narrative) (Details)

v3.8.0.1
Condensed Consolidating Financial Information (Narrative) (Details) - USD ($)
Mar. 31, 2018
Oct. 11, 2017
Dec. 21, 2016
Oct. 14, 2016
Apr. 21, 2015
6.625% Senior Notes due 2023 | Senior notes          
Condensed Financial Statements, Captions [Line Items]          
Debt instrument, amount         $ 350,000,000.0
6.000% Senior Notes due 2024 | Senior notes          
Condensed Financial Statements, Captions [Line Items]          
Debt instrument, amount       $ 650,000,000.0  
6.375% Senior Notes due 2025 | Senior notes          
Condensed Financial Statements, Captions [Line Items]          
Debt instrument, amount     $ 600,000,000.0    
6.375% Senior Notes Due 2026 | Senior notes          
Condensed Financial Statements, Captions [Line Items]          
Debt instrument, amount   $ 450,000,000.0      
Guarantors          
Condensed Financial Statements, Captions [Line Items]          
Ownership percentage by parent 100.00%