Property, Plant and Equipment

12 Months Ended

Dec. 31, 2017

Property, Plant and Equipment

Property, Plant and Equipment

4. Property, Plant and Equipment

Property, plant and equipment consisted of the following (dollars in thousands):

	December 31,
	2017		2016
Land	$	67,278	$	67,278
Buildings		120,999		115,775
Central office equipment		222,248		208,004
Outside communications plant		479,655		412,244
Other equipment, vehicles and furniture		104,846		87,849
Construction in progress		34,759		55,606
Software		90,652		78,547
Other		10,834		10,834
Property, plant and equipment cost	$	1,131,271	$	1,036,137
Less accumulated depreciation		(522,973)		(440,140)
	$	608,298	$	595,997

Depreciation expense amounted to $86.7 million, $87.8 million and $85.4 million for the years ended December 31, 2017, 2016 and 2015, respectively.