Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended	12 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Interest and Debt Expense [Abstract]
Interest incurred on debt	$ 31,389	$ 22,554	$ 63,509	$ 35,473
Related-party Promissory Note interest expense	0	5,090	0	5,090
Senior Note redemption premium	0	0	0	4,782
Accretion of fair value adjustment on Senior Notes	0	0	0	19,414
Accretion of original issue discount on 2018 Term Loans	549	268	1,098	357
Amortization of debt issuance costs	1,031	755	2,062	1,416
Total interest expense	$ 32,969	$ 28,667	$ 66,669	66,532
Effective interest rate, revolving credit facility			5.90%		4.57%
Stated interest rate						6.375%
Accelerated Accretion				18,700
Accelerated Amortization of Debt Issuance Costs				$ 300

Accelerated Accretion on Extinguished Debt

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- Definition

Accelerated Amortization of Debt Issuance Costs

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Accretion Expense on Extinguished Debt

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Amount recognized for the passage of time, typically for liabilities, that have been discounted to their net present values. Excludes accretion associated with asset retirement obligations.

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Amount of amortization expense attributable to debt issuance costs.

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

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Amount of the cost of borrowed funds accounted for as interest expense.

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Amount of the cost of borrowed funds accounted for as interest expense for debt.

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Amount of interest expense incurred on a debt or other obligation to related party.

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The effective interest rate during the reporting period.

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The excess of the (1) fair value of consideration transferred to the holders of a security in excess of (2) the carrying amount of the security reported on the registrant's balance sheet, which will be deducted from net earnings to derive net earnings available to common shareholders. This amount is generally an adjustment considered in the computation of earnings per share.

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