Basis of Presentation and Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2018

Schedule of estimated ranges of useful lives of property and equipment

Property, equipment and leasehold improvements are stated at cost less accumulated depreciation and amortization and depreciated using the straight-line method over their estimated useful lives as follows:



	Asset classification	Estimated useful life
	Laboratory equipment	5 years
	Computer equipment and software	3 to 5 years
	Office equipment and furniture	5 years
	Leasehold improvements	Lesser of useful life or lease term

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



	December 31,
	2018			2017
Laboratory equipment ⁽¹⁾	$	21,328		$	19,777
Leasehold improvements	10,359			10,327
Computer equipment and software	3,954			3,695
Office equipment and furniture	1,272			1,185
Construction in progress ⁽²⁾	939			85
Property and equipment	37,852			35,069
Less: accumulated depreciation and amortization	(33,093		)	(32,254		)
Property and equipment, net	$	4,759		$	2,815

⁽¹⁾ Fully depreciated laboratory equipment with a cost of $0.3 million and $0.2 million were retired during 2018 and 2017, respectively.

⁽²⁾ Construction in progress includes equipment received but not yet placed into service pending installation.