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Summary of Significant Accounting Policies (Narrative) (Details)
a in Millions
 12 Months Ended
Dec. 31, 2020
USD ($)
a
Dec. 31, 2019
USD ($)
Dec. 31, 2018
USD ($)
Principle Accounting Policies [Line Items]      
Timber And Timberlands Acres Owned | a 1.8    
Loss on disposal of property $ 0 $ 900,000 $ 700,000
Gross carrying amount of long-lived intangible assets 8,400,000 8,400,000  
Accumulated amortization 2,300,000 1,500,000  
Amortization expense 800,000 800,000 800,000
Intangible assets estimated amortization expense, year one 800,000    
Intangible assets estimated amortization expense, year two 800,000    
Intangible assets estimated amortization expense, year three 800,000    
Intangible assets estimated amortization expense, year four 800,000    
Intangible assets estimated amortization expense, year five 800,000    
Indefinite-lived intangible assets $ 10,200,000 10,200,000  
Defined benefit obligation of plan assets description   • amortization of cumulative unrecognized net actuarial gains and losses – generally in excess of 10 percent of the greater of the benefit obligation or market-related value of plan assets at the beginning of the year – over the average remaining service period of the active employee group covered by the plan.    
ASU 2018-15 [Member]      
Principle Accounting Policies [Line Items]      
Change in accounting principle, accounting standards update, adopted true    
Change in accounting principle, accounting standards update, adoption date Jan. 01, 2020    
Change in accounting principle, accounting standards update, immaterial effect true    
Change in accounting principle, accounting standards update, transition option elected us-gaap:AccountingStandardsUpdate201815ProspectiveMember    
ASU 2018-14 [Member]      
Principle Accounting Policies [Line Items]      
Change in accounting principle, accounting standards update, adopted true    
Change in accounting principle, accounting standards update, adoption date Jan. 01, 2020    
Change in accounting principle, accounting standards update, immaterial effect true    
ASU 2018-13 [Member]      
Principle Accounting Policies [Line Items]      
Change in accounting principle, accounting standards update, adopted true    
Change in accounting principle, accounting standards update, adoption date Jan. 01, 2020    
Change in accounting principle, accounting standards update, immaterial effect true    
Designated as Hedging Instrument [Member]      
Principle Accounting Policies [Line Items]      
Derivative fair value $ 0 $ 0 $ 0
Intangible Assets, Amortization Period [Member] | Customer Relationships [Member]      
Principle Accounting Policies [Line Items]      
Finite-lived intangible asset, useful life 10 years    
Intangible Assets, Amortization Period [Member] | Trade Names [Member]      
Principle Accounting Policies [Line Items]      
Finite-lived intangible asset, useful life 20 years    
Maximum [Member]      
Principle Accounting Policies [Line Items]      
Business combination measurement period 1 year    
Operating leases, options to extend leases term 5 years    
Maximum [Member] | Timber and Timberlands [Member]      
Principle Accounting Policies [Line Items]      
Timber volume estimate, review period 10 years    
Property, plant and equipment, useful life 20 years    
Minimum [Member]      
Principle Accounting Policies [Line Items]      
Operating leases, options to extend leases term 1 year    
Minimum [Member] | Timber and Timberlands [Member]      
Principle Accounting Policies [Line Items]      
Timber volume estimate, review period 5 years    
Property, plant and equipment, useful life 5 years