Property and Equipment

12 Months Ended

Dec. 31, 2015

4. Property and Equipment

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


	As of December 31,				Estimated
	2015		2014		Useful Lives
Land	$	31.6	$	17.7	Indefinite
Buildings and leasehold improvements		41.2		43.7	3 - 40 years
Office equipment, furniture and fixtures		14.1		13.6	3 - 10 years
Computer equipment and software costs		118.9		102.7	3 - 10 years
Machinery, equipment and vehicles		160.1		132.5	3 - 40 years
		365.9		310.2
Accumulated depreciation and amortization		140.3		106.8
	$	225.6	$	203.4

For 2015, 2014 and 2013, we recorded depreciation expense of $35.1 million, $30.3 million and $22.0 million, respectively.

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


	As of December 31,
	2015		2014
Computer software costs	$	91.4	$	76.8
Accumulated amortization		55.8		45.2
Computer software costs, net	$	35.6	$	31.6

Included in capitalized computer software costs are costs incurred in connection with software development in progress of $7.0 million and $4.7 million as of December 31, 2015 and 2014, respectively. For 2015, 2014 and 2013, we recorded amortization expense related to computer software costs of $10.7 million, $9.8 million and $7.8 million, respectively.

The assets and accumulated amortization recorded under capital leases are as follows (in millions):


	As of December 31,
	2015		2014
Capital leases	$	23.0	$	17.7
Accumulated amortization		11.0		5.5
Capital leases, net	$	12.0	$	12.2