Fair Value of Financial Instruments (Narrative) (Details) - USD ($) $ in Thousands |
Jun. 30, 2018 |
Dec. 31, 2017 |
---|---|---|
Debt Instrument [Line Items] | ||
Unamortized debt issuance costs | $ 32,900 | $ 34,781 |
Senior notes | 6.625% Senior Notes due 2023 | ||
Debt Instrument [Line Items] | ||
Unamortized debt issuance costs | 4,800 | |
Senior notes | 6.000% Senior Notes due 2024 | ||
Debt Instrument [Line Items] | ||
Unamortized debt issuance costs | 9,400 | |
Senior notes | 6.375% Senior Notes due 2025 | ||
Debt Instrument [Line Items] | ||
Unamortized debt issuance costs | 13,200 | |
Senior notes | 6.375% Senior Notes Due 2026 | ||
Debt Instrument [Line Items] | ||
Unamortized debt issuance costs | 5,400 | |
Carry value | Senior notes | ||
Debt Instrument [Line Items] | ||
Carrying value of notes | 2,000,000 | |
Fair value | Senior notes | ||
Debt Instrument [Line Items] | ||
Carrying value of notes | $ 2,000,000 |