Long-Term Debt (Tables)

3 Months Ended

Mar. 31, 2016

Debt Disclosure [Abstract]

Schedule of Borrowing Base Utilization, Credit Facility [Table Text Block]

Effective as of April 8, 2016, the revised borrowing base utilization grid under the Amended Credit Agreement is as follows:

Borrowing Base Utilization Grid

Borrowing Base Utilization Percentage	<25%		≥25% <50%		≥50% <75%		≥75% <90%		≥90%
Eurodollar Loans	1.750	%	2.000	%	2.250	%	2.500	%	2.750	%
ABR Loans or Swingline Loans	0.750	%	1.000	%	1.250	%	1.500	%	1.750	%
Commitment Fee Rate	0.300	%	0.300	%	0.350	%	0.375	%	0.375	%

Schedule of Line of Credit Facilities [Table Text Block]

The following table presents the outstanding balance, total amount of letters of credit outstanding, and available borrowing capacity under the Amended Credit Agreement as of April 27, 2016, and under the Credit Agreement as of March 31, 2016, and December 31, 2015:

	As of April 27, 2016		As of March 31, 2016		As of December 31, 2015
	(in thousands)
Credit facility balance (1)	$	294,500	$	293,000	$	202,000
Letters of credit (2)	$	200	$	200	$	200
Available borrowing capacity	$	955,300	$	1,206,800	$	1,297,800

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⁽¹⁾ Deferred financing costs attributable to the credit facility are presented as a component of other noncurrent assets on the accompanying balance sheets and thus are not deducted from the credit facility balance.

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

Schedule of Long-term Debt Instruments [Table Text Block]

The Senior Notes, net of unamortized deferred financing costs, line on the accompanying balance sheets as of March 31, 2016, and December 31, 2015, consisted of the following:

	As of March 31, 2016						As of December 31, 2015
	Senior Notes		Unamortized Deferred Financing Costs		Senior Notes, Net of Unamortized Deferred Financing Costs		Senior Notes		Unamortized Deferred Financing Costs		Senior Notes, Net of Unamortized Deferred Financing Costs
	(in thousands)
6.50% Senior Notes due 2021	$	346,955	$	3,896	$	343,059	$	350,000	$	4,106	$	345,894
6.125% Senior Notes due 2022	561,796		7,863		553,933		600,000		8,714		591,286
6.50% Senior Notes due 2023	394,985		4,983		390,002		400,000		5,231		394,769
5.0% Senior Notes due 2024	500,000		7,224		492,776		500,000		7,455		492,545
5.625% Senior Notes due 2025	500,000		8,298		491,702		500,000		8,524		491,476
Total	$	2,303,736	$	32,264	$	2,271,472	$	2,350,000	$	34,030	$	2,315,970