Property and Equipment

12 Months Ended

Dec. 31, 2019

Property, Plant and Equipment [Abstract]

The amount of property and equipment and their respective estimated useful lives are as follows (in millions):



	As of December 31,				Estimated
	2019		2018		Useful Lives
Land	$	22.3	$	27.3	Indefinite
Buildings and leasehold improvements	84.8		81.0		3 - 40 years
Office equipment, furniture and fixtures	16.9		20.6		3 - 7 years
Computer equipment and software costs	261.4		194.7		3 - 9 years
Machinery, equipment and vehicles	269.3		276.7		3 - 40 years
	654.8		600.3
Accumulated depreciation and amortization	293.9		249.9
	$	360.9	$	350.3

For 2019, 2018 and 2017, we recorded depreciation expense of $54.5 million, $45.6 million and $44.1 million, respectively.

The amount of computer software costs, including capitalized internally developed software costs are as follows (in millions):



	As of December 31,
	2019		2018
Computer software costs	$	169.9	$	115.6
Accumulated amortization	110.0		91.2
Computer software costs, net	$	59.9	$	24.5

Included in capitalized computer software costs are costs incurred in connection with software development in progress of $22.5 million and $46.2 million as of December 31, 2019 and 2018, respectively. For 2019, 2018 and 2017, we recorded amortization expense related to computer software costs of $17.8 million, $10.9 million and $11.0 million, respectively.