Segment Information - Schedule of Results by Segment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Sep. 30, 2023
Segment Reporting Information [Line Items]
Total revenues	$ 506,974	$ 553,430
Operating Segments
Segment Reporting Information [Line Items]
Total revenues	503,800	551,427
Less segment expenses:
Segment Operating EBITDA	49,580	67,570
Purchase of property, plant and equipment	20,041	18,426
Operating Segments \| Market Pulp
Segment Reporting Information [Line Items]
Total revenues	381,080	432,404	$ 381,080
Less segment expenses:
Segment Operating EBITDA	49,872	68,465
Purchase of property, plant and equipment	13,760	9,421
Operating Segments \| Solid Wood
Segment Reporting Information [Line Items]
Total revenues	122,720	119,023
Less segment expenses:
Segment Operating EBITDA	(292)	(895)
Purchase of property, plant and equipment	6,281	9,005
Operating Segments \| Fiber \| Market Pulp
Less segment expenses:
Segment Expenses	138,284	150,786
Operating Segments \| Fiber \| Solid Wood
Less segment expenses:
Segment Expenses	66,368	63,603
Operating Segments \| Maintenance \| Market Pulp
Less segment expenses:
Segment Expenses	41,966	22,718
Operating Segments \| Maintenance \| Solid Wood
Less segment expenses:
Segment Expenses	9,193	11,036
Operating Segments \| Freight \| Market Pulp
Less segment expenses:
Segment Expenses	35,432	43,684
Operating Segments \| Freight \| Solid Wood
Less segment expenses:
Segment Expenses	13,324	13,381
Operating Segments \| Labor \| Market Pulp
Less segment expenses:
Segment Expenses	24,193	22,720
Operating Segments \| Labor \| Solid Wood
Less segment expenses:
Segment Expenses	14,647	14,122
Operating Segments \| Chemicals \| Market Pulp
Less segment expenses:
Segment Expenses	28,061	33,398
Operating Segments \| Chemicals \| Solid Wood
Less segment expenses:
Segment Expenses	0	0
Operating Segments \| Energy \| Market Pulp
Less segment expenses:
Segment Expenses	14,407	20,464
Operating Segments \| Energy \| Solid Wood
Less segment expenses:
Segment Expenses	8,424	6,792
Operating Segments \| Purchase of pulp from CPP \| Market Pulp
Less segment expenses:
Segment Expenses		19,707
Operating Segments \| Purchase of pulp from CPP \| Solid Wood
Less segment expenses:
Segment Expenses		0
Operating Segments \| Other \| Market Pulp
Less segment expenses:
Segment Expenses	49,209	50,622
Operating Segments \| Other \| Solid Wood
Less segment expenses:
Segment Expenses	21,077	20,706
Intersegment Eliminations
Segment Reporting Information [Line Items]
Total revenues	10,365	9,882
Intersegment Eliminations \| Market Pulp
Segment Reporting Information [Line Items]
Total revenues	344	160
Intersegment Eliminations \| Solid Wood
Segment Reporting Information [Line Items]
Total revenues	10,021	9,722
Segment Excluding Corporate
Segment Reporting Information [Line Items]
Total revenues	514,165	561,309
Segment Excluding Corporate \| Market Pulp
Segment Reporting Information [Line Items]
Total revenues	381,424	432,564
Segment Excluding Corporate \| Solid Wood
Segment Reporting Information [Line Items]
Total revenues	132,741	128,745
Corporate and Other
Segment Reporting Information [Line Items]
Total revenues	$ 3,174	$ 2,003

MERCER INTERNATIONAL INC. 10-Q