PROPERTY, PLANT, AND EQUIPMENT

6 Months Ended

Jun. 30, 2020

Property, Plant and Equipment [Abstract]

PROPERTY, PLANT, AND EQUIPMENT

PROPERTY, PLANT AND EQUIPMENT

The estimated useful lives of property, plant and equipment are as follows:

(In thousands)	Estimated Useful Life	June 30, 2020		December 31, 2019
Property, plant and equipment	​	​		​
Land	n/a	$	4,466	$	4,466
Leasehold and building improvements	(1)	111,778		80,352
Land improvements	15 years	2,399		1,766
Buildings	30 - 40 years	165,926		112,815
Computer equipment and computer software	3 years	74,447		65,323
Laboratory equipment	3 - 10 years	130,323		104,008
Furniture and fixtures	3 - 10 years	22,698		14,539
Assets under construction	n/a	61,628		149,687
Property, plant and equipment, at cost	​	573,665		532,956
Accumulated depreciation	​	(110,228)		(77,631)
Property, plant and equipment, net	​	$	463,437	$	455,325

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(1)Lesser of remaining lease term, building life, or estimated useful life.

Depreciation expense for the three months ended June 30, 2020 and 2019 was $17.6 million and $7.1 million, respectively. Depreciation expense for the six months ended June 30, 2020 and 2019 was $33.4 million and $13.4 million, respectively.

At June 30, 2020, the Company had $61.6 million of assets under construction which consisted of $11.5 million in laboratory equipment, $43.9 million of building and leasehold improvements, $5.6 million in capitalized costs related to software projects, and $0.6 million related to furniture and fixtures. Depreciation will begin on these assets once they are placed into service. The Company expects to incur an additional $2.9 million to complete the laboratory equipment, $6.7 million to complete the building projects and leasehold improvements, $2.0 million to complete the software projects, and minimal costs to complete the furniture and fixtures. These projects are expected to be completed throughout 2020 and 2021.