Long-Term Debt (Tables)

6 Months Ended

Jun. 30, 2019

Debt Disclosure [Abstract]

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 July 23, 2019, June 30, 2019, and December 31, 2018:

	As of July 23, 2019		As of June 30, 2019		As of December 31, 2018
	(in thousands)
Credit facility balance (1)	$	126,000	$	118,000	$	—
Letters of credit (2)	—		—		200
Available borrowing capacity	1,074,000		1,082,000		999,800
Total aggregate lender commitment amount	$	1,200,000	$	1,200,000	$	1,000,000

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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 $6.4 million as of June 30, 2019, and December 31, 2018, 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. The letter of credit outstanding as of December 31, 2018, was released during the three months ended March 31, 2019.

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 June 30, 2019, and December 31, 2018, consisted of the following:

	As of June 30, 2019						As of December 31, 2018
	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)
6.125% Senior Notes due 2022	$	476,796	$	3,420	$	473,376	$	476,796	$	3,921	$	472,875
5.0% Senior Notes due 2024	500,000		4,227		495,773		500,000		4,688		495,312
5.625% Senior Notes due 2025	500,000		5,356		494,644		500,000		5,808		494,192
6.75% Senior Notes due 2026	500,000		5,989		494,011		500,000		6,407		493,593
6.625% Senior Notes due 2027	500,000		7,067		492,933		500,000		7,533		492,467
Total	$	2,476,796	$	26,059	$	2,450,737	$	2,476,796	$	28,357	$	2,448,439

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 June 30, 2019, and December 31, 2018, consisted of the following:

	As of June 30, 2019			As of December 31, 2018
	(in thousands)
Principal amount of Senior Convertible Notes	$	172,500		$	172,500
Unamortized debt discount	(18,162		)	(22,313		)
Unamortized deferred financing costs	(1,835		)	(2,293		)
Senior Convertible Notes, net of unamortized discount and deferred financing costs	$	152,503		$	147,894