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Property, Plant, and Equipment
 12 Months Ended
Dec. 31, 2019
Property, Plant and Equipment [Abstract]  
Property, Plant, and Equipment Property, Plant, and Equipment
The following table summarizes the components of property, plant, and equipment as of December 31, 2019 and 2018.
 
December 31,
2019
 
December 31,
2018
 
(in millions)
Land(1)
$
331.4

 
$
316.5

Buildings and improvements
280.5

 
267.5

Machinery and other
755.7

 
715.9

Construction in progress
38.6

 
28.8

 
1,406.2

 
1,328.7

Less accumulated depreciation and depletion
(590.0
)
 
(525.7
)
 
$
816.2

 
$
803.0


(1) Includes depletable land of $211.0 million as of December 31, 2019 and $201.9 million as of December 31, 2018.
We did not capitalize any interest expense as part of the construction of facilities and equipment during 2019 or 2018.
We estimate the fair market value of properties no longer in use based on the location and condition of the properties, the fair market value of similar properties in the area, and the Company's experience selling similar properties in the past. As of December 31, 2019, the Company had non-operating plants with a net book value of $47.4 million. Our estimated fair value of these assets exceeds their book value.