Real Estate Sales - AgReserves Sales (Details) - USD ($)		1 Months Ended	12 Months Ended
	Mar. 05, 2014	Apr. 30, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Other operating expenses			$ 23,019,000	$ 33,426,000	$ 26,128,000
Investments held by special purpose entities	$ 203,500,000.0		208,590,000	208,785,000
Debt principal amount		$ 180,000,000
Debt interest rate		4.75%
Accrued interest receivable for Senior Notes held by SPE			2,938,000	3,338,000
Proceeds from monetization		$ 165,000,000.0
Cost of monetization		$ 15,000,000.0
Expected amount to receive upon maturity of note after payment of note and any other liabilities			20,000,000.0
Administrative costs associated with special purpose entities			$ 0	0	3,746,000
Percent ownership in special purpose entity			0.00%
Senior Notes held by special purpose entity			$ 176,310,000	176,094,000
Investment income, net			8,202,000	8,217,000	6,116,000
Interest expense			(8,833,000)	$ (8,755,000)	(6,584,000)
Subsidiaries | Notes Receivable
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Issue price of senior secured notes		98.50%
Special Purpose Entities
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Accrued interest receivable for Senior Notes held by SPE			2,900,000
Expected amount to receive upon maturity of note after payment of note and any other liabilities			16,900,000
Debt discount and issuance costs		$ 4,300,000
Investments contributed to special purpose entity by the company		$ 7,000,000
Time deposits			200,000,000
U.S. Treasury securities			8,200,000
Cash			$ 400,000
Held-to-maturity security, term			13 years
Held-to-maturity Securities, debt maturities, within one year			$ 600,000
Held-to-maturity Securities, debt maturities, year two through five			2,500,000
Held-to-maturity Securities, debt maturities, after five through ten years			3,400,000
Held-to-maturity Securities, debt maturities, after ten years			$ 1,700,000
Special Purpose Entities | Notes Receivable
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Debt interest rate			4.00%
Northwest Florida Timber Finance, LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Accrued interest			$ 2,900,000
Senior Notes held by special purpose entity			176,300,000
Debt unamortized discount			3,700,000
Buyer Special Purpose Entity
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Assets held by special purpose entity			211,500,000
Liabilities held by special purpose entity			$ 179,200,000
AgReserves Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Consideration received for real estate sale	562,000,000
Pre-tax income on real estate sale	511,100,000
Other operating expenses					$ 1,200,000
Cash proceeds from sale of real estate	358,500,000.0
Notes received in sale of real estate	$ 200,000,000
Maturity of notes receivables	15 years