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Basis of Presentation and Significant Accounting Policies Basis of Presentation and Significant Accounting Policies - Changes in Deferred Debt Issuance Costs (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Deferred Finance Costs [Roll Forward]
Balance at beginning of period	$ 4,202	$ 5,892
Additions			$ 9,443	$ 0
Interest expense	(3,273)	(850)
Balance at end of period	10,372	5,042
Recognition of debt issuance costs from Former Credit Facility	$ 2,441	$ 0

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- Definition

Deferred Finance Costs [Roll Forward]

+ References

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Amount of amortization expense attributable to debt issuance costs.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
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-Section 45
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Amount, before accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28555-108399

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Write-off of amounts previously capitalized as debt issuance cost in an extinguishment of debt.

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