Details of Selected Balance Sheet Accounts (Tables)

12 Months Ended

Dec. 31, 2017

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Summary of accounts receivable

A summary of accounts receivable follows (in thousands):	December 31,
	2017			2016
Accounts receivable, principally trade	$	20,050		$	22,214
Less allowance for doubtful accounts	(572		)	(1,444		)
Accounts receivable, net	$	19,478		$	20,770

Summary of inventories

A summary of inventories follows (in thousands):	December 31,
	2017			2016
Raw materials and purchased subassemblies	$	20,448		$	21,454
Work-in-process	1,146			2,255
Finished goods	7,953			6,581
Reserve for excess and obsolete inventories	(15,039		)	(15,049		)
Total	$	14,508		$	15,241

Summary of Property, Plant, Equipment and Seismic Rental Equipment

Property, plant, equipment and seismic rental equipment are stated at cost. Depreciation expense is provided straight-line over the following estimated useful lives:

	Years
Machinery and equipment	3-7
Buildings	5-25
Seismic rental equipment	3-5
Leased equipment and other	3-10

A summary of property, plant, equipment and seismic rental equipment follows (in thousands):

	December 31,
	2017			2016
Buildings	$	15,822		$	17,424
Machinery and equipment	145,654			157,618
Seismic rental equipment	1,677			1,557
Furniture and fixtures	3,869			3,905
Other	28,965			30,049
Total	195,987			210,553
Less accumulated depreciation	(143,834		)	(143,065		)
Property, plant, equipment and seismic rental equipment, net	$	52,153		$	67,488

Summary of finite intangible assets, net

A summary of intangible assets, net, follows (in thousands):	December 31, 2017
	Gross Amount		Accumulated Amortization			Net
Customer relationships	$	34,400	$	(32,734	)	$	1,666
Total	$	34,400	$	(32,734	)	$	1,666

	December 31, 2016
	Gross Amount		Accumulated Amortization			Net
Customer relationships	$	36,934	$	(33,831	)	$	3,103
Total	$	36,934	$	(33,831	)	$	3,103

Estimated future amortization expense

A summary of the estimated amortization expense for the next three years follows (in thousands):

Years Ended December 31,
2018	$	1,169
2019	$	497

Summary of accrued expenses

A summary of other long-term liabilities follows (in thousands):	December 31,
	2017		2016
Deferred lease liabilities	12,811		13,955
Facility restructuring accrual	—		1,765
Deferred income tax liability	—		3,679
Other	1,115		1,128
Total	$	13,926	$	20,527

A summary of accrued expenses follows (in thousands):	December 31,
	2017		2016
Compensation, including compensation-related taxes and commissions	$	19,809	$	14,935
Accrued multi-client data library acquisition costs	5,104		567
Income tax payable	1,868		1,306
Accrual for legal proceedings (Footnote 6)	3,750		—
Other	8,166		9,432
Total	$	38,697	$	26,240