Long-Term Debt - Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Long-Term Debt
Coupon interest at 3.75%	$ 3,047	$ 3,047	$ 6,094	$ 6,094
Amortization of debt issuance costs	356	356	712	712
Total interest expense on the Notes	$ 3,403	$ 3,403	$ 6,806	$ 6,806
Coupon interest rate	3.75%	3.75%	3.75%	3.75%

Amount of amortization expense attributable to debt issuance costs.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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-Name Accounting Standards Codification
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-Section 45
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-URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
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- References

No definition available.

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
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- Definition

Represents the portion of interest incurred in the period on debt arrangements that was charged against earnings, excluding amortization of debt discount (premium) and financing costs.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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The interest rate applicable to the portion of the carrying amount of long-term borrowings outstanding as of the balance sheet date, including current maturities, which accrues interest at a set, unchanging rate.

+ References

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