Long-term Debt (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
6.125% Senior Notes due 2022 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Principal Amount	$ 476,796	$ 476,796
Long-term Debt, Fair Value	$ 472,963	452,336
Senior Notes, interest rate, stated percentage	6.125%
5.0% Senior Notes due 2024 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Principal Amount	$ 500,000	500,000
Long-term Debt, Fair Value	$ 464,215	439,265
Senior Notes, interest rate, stated percentage	5.00%
5.625% Senior Notes due 2025 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Principal Amount	$ 500,000	500,000
Long-term Debt, Fair Value	$ 455,650	436,460
Senior Notes, interest rate, stated percentage	5.625%
6.75% Senior Notes due 2026 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Principal Amount	$ 500,000	500,000
Long-term Debt, Fair Value	$ 470,000	448,305
Senior Notes, interest rate, stated percentage	6.75%
6.625% Senior Notes due 2027 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Principal Amount	$ 500,000	500,000
Long-term Debt, Fair Value	$ 463,900	442,500
Senior Notes, interest rate, stated percentage	6.625%
1.50% Senior Convertible Notes Due 2021 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Principal Amount	$ 172,500	172,500
Long-term Debt, Fair Value	$ 160,339	$ 158,614
Senior Notes, interest rate, stated percentage	1.50%

Face (par) amount of debt instrument at time of issuance.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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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.

+ References

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