Summary of Significant Accounting Policies - Revenue Recognition (Details)	12 Months Ended
	Dec. 31, 2018 method
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Number of primary methods or sales channels	2
Contract duration (or less)	1 year
Stumpage Pay-as-Cut
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Payment period after satisfaction of obligation	10 days
Stumpage Pay-as-Cut | Minimum
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Initial payment, percentage of estimated contract value	5.00%
Stumpage Pay-as-Cut | Maximum
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Initial payment, percentage of estimated contract value	20.00%
Domestic | Total Delivered
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Payment period after satisfaction of obligation	30 days
Payment period after satisfaction of obligation, letter of credit	30 days