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Property and Equipment
 12 Months Ended
Dec. 31, 2020
Property, Plant and Equipment [Abstract]  
Property and Equipment Property and Equipment
Property and equipment consisted of the following at December 31:
(dollars in thousands)Estimated
Useful Life
in Years		20202019
Land—$9,301 $9,301 
Buildings and improvements
3 to 39
33,452 29,747 
Construction equipment
3 to 12
420,002 403,217 
Office equipment
3 to 10
16,725 15,944 
479,480 458,209 
Less: accumulated depreciation and amortization(294,366)(272,865)
$185,114 $185,344 
Construction equipment includes assets under finance leases — see additional information provided in Note 4 — Lease Obligations to the Financial Statements.
Depreciation and amortization expense of property and equipment for the years ended December 31, 2020, 2019 and 2018 was $42.9 million, $40.7 million and $38.1 million, respectively.