Timberland Acquisitions - Narrative (Details) shares in Thousands, $ in Thousands	1 Months Ended	12 Months Ended
	Nov. 30, 2011 a	Dec. 31, 2017 USD ($) a acquisition shares	Dec. 31, 2016 USD ($) a acquisition	Dec. 31, 2015 USD ($)	May 31, 2016 USD ($)
Business Acquisition [Line Items]
Timberlands acquired (acres) | a	250,000	109,533	110,727
Payments to acquire timberlands | $		$ 242,910	$ 366,481	$ 98,409
Georgia and Washington
Business Acquisition [Line Items]
Number of acquisitions | acquisition		5
Timberlands acquired (acres) | a		7,000
Payments to acquire timberlands | $		$ 7,200
Florida, Georgia, and South Carolina
Business Acquisition [Line Items]
Timberlands acquired (acres) | a		95,000
Timberlands acquired, leased lands (acres) | a		11,000
Shares sold (shares) | shares		5,750
Payments to acquire timberlands | $		$ 214,300
New Zealand
Business Acquisition [Line Items]
Number of acquisitions | acquisition		2
Timberlands acquired (acres) | a		7,546	0
Payments to acquire timberlands | $		$ 21,376	$ 0
Oregon and Washington
Business Acquisition [Line Items]
Timberlands acquired (acres) | a			61,000
Consideration for timberlands | $			$ 263,000
Florida, Georgia, and Texas
Business Acquisition [Line Items]
Number of acquisitions | acquisition			5
Timberlands acquired (acres) | a			50,000
Payments to acquire timberlands | $			$ 103,900
Incremental Term Loan | Oregon and Washington
Business Acquisition [Line Items]
Incremental term loan | $					$ 300,000