Timberland Acquisition (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2018 USD ($) a Property
Business Acquisition [Line Items]
Funds held by like-kind exchange intermediaries	$ 598
Productive Land
Business Acquisition [Line Items]
Transfer of non-strategic timberland to seller, in acres | a	365
Transfer of non-strategic timberland to seller, value	$ 214
Western Washington
Business Acquisition [Line Items]
Number of acquisitions | Property	6
Acres of land acquired | a	1,342
Assets acquired	$ 7,200
Western Washington | Land
Business Acquisition [Line Items]
Assets acquired	869
Western Washington | Timber and roads
Business Acquisition [Line Items]
Assets acquired	$ 6,300