Fair Value of Financial Instruments - Fair Value of Fixed-Rate Notes (Details) $ in Thousands	Mar. 31, 2018 USD ($)
5.125% Senior Notes due 2019
Fair Value of Fixed - Rate Notes
Fair value of fixed - rate notes	$ 353,208
6.875% Senior Notes due 2021
Fair Value of Fixed - Rate Notes
Fair value of fixed - rate notes	366,819
7.50% Senior Notes due 2023
Fair Value of Fixed - Rate Notes
Fair value of fixed - rate notes	618,072
6.125% Senior Notes due 2025
Fair Value of Fixed - Rate Notes
Fair value of fixed - rate notes	$ 370,651

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

No definition available.

Name:	us-gaap_LongTermDebtFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant