Financial Instruments and Fair Value Measurements - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset impairment charges	$ 714,000	$ 357,000	$ 0
Retained interest investments	11,147,000	10,635,000
Debt principal amount				$ 180,000,000.0
Debt interest rate				4.80%
Senior Notes held by special purpose entity	176,537,000	176,310,000
Northwest Florida Timber Finance, LLC
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior Notes held by special purpose entity	176,500,000
Debt unamortized discount	3,500,000
Special Purpose Entities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Expected amount to receive upon maturity of note after payment of note and any other liabilities	$ 16,800,000
Promissory notes maturity period	15 years
Retained interest investments	$ 11,100,000	$ 10,600,000
Special Purpose Entities | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notes maturity year	2022
Special Purpose Entities | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notes maturity year	2024
Short-term bond | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment term	0 years
Short-term bond | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment term	3 years
AgReserves Sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notes received in sale of real estate				$ 200,000,000
Maturity of notes receivables				15 years
Special Purpose Entities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Time deposits	$ 200,000,000.0
U.S. Treasury securities	7,600,000
Cash	$ 400,000
Notes Receivable | Subsidiaries
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Issue price of senior secured notes				98.50%
Notes Receivable | Special Purpose Entities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt interest rate	4.00%