PROPERTY AND EQUIPMENT

12 Months Ended

Dec. 31, 2016

Property Plant And Equipment [Abstract]

PROPERTY AND EQUIPMENT

7. PROPERTY AND EQUIPMENT

Property and equipment are recorded at historical cost, net of accumulated depreciation. The following table summarizes components of property and equipment, net for each of the periods indicated:

	As of December 31,
	2016			2015
	(in thousands)
Land	$	4,158		$	4,158
Building and improvements		12,729			12,718
Software and computer equipment		6,775			6,149
Lab equipment		14,149			12,873
Office equipment		3,028			2,762
Leasehold improvements		22,872			21,723
Construction in progress		4,436			1,555
Property and equipment, gross		68,147			61,938
Less: accumulated depreciation		(30,346	)		(24,594	)
Property and equipment, net	$	37,801		$	37,344

For the years ended December 31, 2016, 2015 and 2014, depreciation expense totaled $5.0 million, $4.7 million and $3.2 million, respectively. Included in the $30.3 million accumulated depreciation as of December 31, 2016 was $0.8 million accelerated depreciation for certain assets whose expected useful lives were shortened due to the Corvallis plan (defined in Note 9).