Long-Term Debt (Tables)

9 Months Ended

Sep. 30, 2018

Debt Disclosure [Abstract]

Schedule of Borrowing Base Utilization [Table Text Block]

The borrowing base utilization grid under the Credit Agreement is as follows:

Borrowing Base Utilization Percentage	<25%		≥25% <50%		≥50% <75%		≥75% <90%		≥90%
Eurodollar Loans	1.500	%	1.750	%	2.000	%	2.250	%	2.500	%
ABR Loans or Swingline Loans	0.500	%	0.750	%	1.000	%	1.250	%	1.500	%
Commitment Fee Rate	0.375	%	0.375	%	0.500	%	0.500	%	0.500	%

Schedule of Credit Agreement Facilities [Table Text Block]

The following table presents the outstanding balance, total amount of letters of credit outstanding, and available borrowing capacity under the Credit Agreement as of October 24, 2018, and September 30, 2018, and under the Fifth Amended and Restated Credit Agreement as of December 31, 2017:

	As of October 24, 2018		As of September 30, 2018		As of December 31, 2017
	(in thousands)
Credit facility balance (1)	$	—	$	—	$	—
Letters of credit (2)	200		200		200
Available borrowing capacity	999,800		999,800		924,800
Total aggregate lender commitment amount	$	1,000,000	$	1,000,000	$	925,000

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⁽¹⁾  Unamortized deferred financing costs attributable to the credit facility are presented as a component of other noncurrent assets on the accompanying balance sheets and totaled $6.7 million and $3.1 million as of September 30, 2018, and December 31, 2017, respectively. These costs are being amortized over the term of the credit facility on a straight-line basis.

⁽²⁾  Letters of credit outstanding reduce the amount available under the credit facility on a dollar-for-dollar basis.

Schedule of Senior Notes [Table Text Block]

The Senior Notes, net of unamortized deferred financing costs line item on the accompanying balance sheets as of September 30, 2018, and December 31, 2017, consisted of the following:

	As of September 30, 2018						As of December 31, 2017
	Principal Amount		Unamortized Deferred Financing Costs		Principal Amount, Net of Unamortized Deferred Financing Costs		Principal Amount		Unamortized Deferred Financing Costs		Principal Amount, Net of Unamortized Deferred Financing Costs
	(in thousands)
6.50% Senior Notes due 2021	$	—	$	—	$	—	$	344,611	$	2,656	$	341,955
6.125% Senior Notes due 2022	476,796		4,171		472,625		561,796		5,800		555,996
6.50% Senior Notes due 2023	—		—		—		394,985		3,707		391,278
5.0% Senior Notes due 2024	500,000		4,919		495,081		500,000		5,610		494,390
5.625% Senior Notes due 2025	500,000		6,035		493,965		500,000		6,714		493,286
6.75% Senior Notes due 2026	500,000		6,615		493,385		500,000		7,242		492,758
6.625% Senior Notes due 2027	500,000		7,766		492,234		—		—		—
Total	$	2,476,796	$	29,506	$	2,447,290	$	2,801,392	$	31,729	$	2,769,663

Schedule of Senior Convertible Notes [Table Text Block]

The Senior Convertible Notes, net of unamortized discount and deferred financing costs line on the accompanying balance sheets as of September 30, 2018, and December 31, 2017, consisted of the following:

	As of September 30, 2018			As of December 31, 2017
	(in thousands)
Principal amount of Senior Convertible Notes	$	172,500		$	172,500
Unamortized debt discount	(24,316		)	(30,183		)
Unamortized deferred financing costs	(2,522		)	(3,210		)
Senior Convertible Notes, net of unamortized discount and deferred financing costs	$	145,662		$	139,107