Timberland Acquisitions - Summary of Timberland Acquisitions (Details) $ in Thousands	1 Months Ended	12 Months Ended
	Nov. 30, 2011 a	Dec. 31, 2017 USD ($) a	Dec. 31, 2016 USD ($) a	Dec. 31, 2015 USD ($)
Business Acquisition [Line Items]
Cost | $		$ 242,910	$ 366,481	$ 98,409
Acres | a	250,000	109,533	110,727
Florida
Business Acquisition [Line Items]
Cost | $		$ 32,334	$ 14,323
Acres | a		15,382	6,937
Georgia
Business Acquisition [Line Items]
Cost | $		$ 147,833	$ 12,485
Acres | a		68,473	5,427
Oregon
Business Acquisition [Line Items]
Cost | $		$ 0	$ 239,896
Acres | a		0	55,603
South Carolina
Business Acquisition [Line Items]
Cost | $		$ 39,884	$ 0
Acres | a		17,651	0
Texas
Business Acquisition [Line Items]
Cost | $		$ 0	$ 77,139
Acres | a		0	37,513
Washington
Business Acquisition [Line Items]
Cost | $		$ 1,483	$ 22,638
Acres | a		481	5,247
New Zealand
Business Acquisition [Line Items]
Cost | $		$ 21,376	$ 0
Acres | a		7,546	0