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

12 Months Ended

Dec. 31, 2017

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,
	2017			2016
Laboratory equipment ⁽¹⁾	$	19,777		$	18,849
Leasehold improvements	10,327			10,395
Computer equipment and software	3,695			3,267
Office equipment and furniture	1,185			1,171
Construction in progress ⁽²⁾	85			124
Property and equipment	35,069			33,806
Less: accumulated depreciation and amortization	(32,254		)	(31,651		)
Property and equipment, net	$	2,815		$	2,155

⁽¹⁾ Fully depreciated laboratory equipment with a cost of $0.2 million and $2.3 million were retired during 2017 and 2016, respectively.

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