The interest rate for investments that have an interest rate. For fixed rate investments, this indicates the fixed interest rate. If the investment has a variable interest rate, the rate stated here may be the rate that is currently relevant. In this case the "Investment, Interest Rate is Current Rate for Variable Rate Investment Flag", "Investment, Interest Rate is Discount Rate at Purchase Flag", "Investment, Interest Rate Reflects Current Yield Flag" should be used. If one of these flags are not appropriate to explain the interest rate that is indicated, then a new flag should be added or an explanation should be included in "Investment, Additional Information".

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 12
-Sentence Column A

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Disposal Group, Including Discontinued Operation, Consideration, Notes Receivable

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- Definition

Amount of investments held by special purpose entity.

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No definition available.

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- Definition

Issue price of notes as a percent of the face value.

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No definition available.

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- Definition

Period of time between issuance and maturity of note receivable, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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No definition available.

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- Definition

Senior notes held by special purpose entity.

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- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

Amount, after accumulated amortization, of debt discount (premium).

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
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-Name Accounting Standards Codification
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-Section 45
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
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-Section 55
-Paragraph 8
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-Section 45
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-Section 45
-Paragraph 3
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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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Financial Instruments and Fair Value Measurements - Held by Special Purpose Entities (Details) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2018 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2017 USD ($)
Financial instruments and fair value measurements
Investments held by special purpose entities	$ 207,664		$ 207,989
Senior notes held by special purpose entity	176,655		$ 176,537
Panama City Timber Finance Company, LLC \| 2014 real estate sale
Financial instruments and fair value measurements
Notes received as consideration in sale of real estate		$ 200,000
Promissory notes maturity period		15 years
Panama City Timber Finance Company, LLC \| Time deposit
Financial instruments and fair value measurements
Investments held by special purpose entities	$ 200,000
Investment interest rate (as a percent)	4.00%
Panama City Timber Finance Company, LLC \| U.S. Treasury securities
Financial instruments and fair value measurements
Investments held by special purpose entities	$ 7,300
Panama City Timber Finance Company, LLC \| Cash
Financial instruments and fair value measurements
Investments held by special purpose entities	400
Northwest Florida Timber Finance, LLC
Financial instruments and fair value measurements
Loan amount		$ 180,000
Debt interest rate (as a percent)		4.80%
Issue price of senior secured notes (as a percent)		0.985
Senior notes held by special purpose entity	176,700
Unamortized discount and debt issuance costs	$ 3,300