Property and Equipment, Net

3 Months Ended

Mar. 31, 2018

Property Plant And Equipment [Abstract]

4.	PROPERTY AND EQUIPMENT, NET

Property and equipment and accumulated depreciation and amortization were as follows:

	March 31,			December 31,
	2018			2017
Property and equipment
Buildings	$	60,647		$	60,441
Software and capitalized software costs		49,404			41,996
Computer equipment		30,525			27,928
Rental clocks		13,627			13,131
Furniture, fixtures and equipment		7,776			7,528
Leasehold improvements		779			767
Vehicles		50			—
		162,808			151,791
Less: accumulated depreciation and amortization		(59,540	)		(53,525	)
		103,268			98,266
Construction in progress		47,280			40,446
Land		9,013			8,993
Property and equipment, net	$	159,561		$	147,705

We capitalize computer software development costs related to software developed for internal use in accordance with ASC 350-40. For the three months ended March 31, 2018 and 2017, respectively, we capitalized $6.6 million and $2.9 million of computer software development costs related to software developed for internal use.

Rental clocks included in property and equipment, net represent time clocks issued to clients under month-to-month operating leases. As such, these items are transferred from inventory to property and equipment and depreciated over their estimated useful lives.

Included in the construction in progress balance at March 31, 2018 and December 31, 2017 is $1.6 million and $2.0 million in retainage, respectively.

We capitalize interest incurred for indebtedness related to construction of our principal executive offices. For the three months ended March 31, 2018, we incurred interest costs of $0.4 million, $0.4 million of which was capitalized. For the three months ended March 31, 2017, we incurred interest costs of $0.4 million, $0.1 million of which was capitalized.

Depreciation and amortization expense for property and equipment, net was $6.0 million and $3.9 million for the three months ended March 31, 2018 and 2017, respectively.