Basis of Presentation and Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2018

Accounting Policies [Abstract]

Estimated Depreciable Lives of Property, Plant and Equipment

Depreciation is calculated using the straight-line method over the estimated depreciable lives of the respective assets as follows:

	Depreciable Lives
Energy Servers	15-21 years
Computers, software and hardware	3-5 years
Machinery and equipment	5-10 years
Furniture and fixtures	3-5 years
Leasehold improvements	1-10 years
Buildings	35 years

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

	December 31,
	2018			2017
Energy Servers	$	511,485		$	511,153
Computers, software and hardware	16,536			19,384
Machinery and equipment	99,209			97,158
Furniture and fixtures	4,337			4,679
Leasehold improvements	18,629			22,799
Building	40,512			40,512
Construction in progress	29,084			9,898
	719,792			705,583
Less: Accumulated depreciation	(238,378		)	(207,794		)
	$	481,414		$	497,789