Details of Selected Balance Sheet Accounts

Accounts Receivable



A summary of accounts receivable follows (in thousands):	December 31,
	2016			2015
Accounts receivable, principally trade	$	22,214		$	49,284
Less allowance for doubtful accounts	(1,444		)	(4,919		)
Accounts receivable, net	$	20,770		$	44,365

Inventories



A summary of inventories follows (in thousands):	December 31,
	2016			2015
Raw materials and purchased subassemblies	$	21,454		$	34,949
Work-in-process	2,255			8,478
Finished goods	6,581			13,769
Reserve for excess and obsolete inventories	(15,049		)	(24,475		)
Total ^(a)	$	15,241		$	32,721


(a)	For 2016, inventories, net, decreased primarily due to the transfer of $17.7 million of inventory to property, plant, equipment and seismic rental equipment, net, primarily related to ocean bottom equipment to be used on future Ocean Bottom Services contracts.

The Company provides for estimated obsolescence or excess inventory in amounts equal to the difference between the cost of inventory and market based upon assumptions about future demand for the Company’s products and market conditions and risk of obsolescence. In 2016, the reserve for excess and obsolete inventory decreased due to the transfer of reserved ocean bottom equipment inventory to be used in Ocean Bottom Services contracts, partially offset by the increase in the Company’s reserve for excess and obsolete inventories by $0.4 million.

Property, Plant, Equipment and Seismic Rental Equipment

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



	December 31,
	2016			2015
Buildings	$	17,424		$	24,181
Machinery and equipment ^(a)	157,618			152,358
Seismic rental equipment	1,557			1,904
Furniture and fixtures	3,905			4,334
Other	30,049			31,821
Total	210,553			214,598
Less accumulated depreciation	(143,065		)	(142,571		)
Property, plant, equipment and seismic rental equipment, net	$	67,488		$	72,027


(a)	In 2016, the company transferred $17.7 million of Ocean Bottom equipment from inventory to machinery and equipment.

Total depreciation expense, including amortization of assets recorded under capital leases, for 2016, 2015 and 2014 was $20.3 million, $24.6 million and $25.1 million, respectively.

Intangible Assets



A summary of intangible assets, net, follows (in thousands):	December 31, 2016
	Gross Amount		Accumulated Amortization			Net
Customer relationships	$	36,934	$	(33,831	)	$	3,103
Total	$	36,934	$	(33,831	)	$	3,103



	December 31, 2015
	Gross Amount		Accumulated Amortization			Net
Customer relationships	$	37,469	$	(32,659	)	$	4,810
Total	$	37,469	$	(32,659	)	$	4,810

Total amortization expense for intangible assets for 2016, 2015 and 2014 was $1.7 million, $1.9 million and $2.5 million, respectively. A summary of the estimated amortization expense for the next three years follows (in thousands):



Years Ended December 31,
2017	$	1,436
2018	$	1,169
2019	$	498

Accrued Expenses



A summary of accrued expenses follows (in thousands):	December 31,
	2016		2015
Compensation, including compensation-related taxes and commissions	$	14,935	$	19,126
Accrued multi-client data library acquisition costs	567		1,600
Income tax payable	1,306		—
Other	9,432		13,561
Total	$	26,240	$	34,287

Other Long-term Liabilities



A summary of other long-term liabilities follows (in thousands):	December 31,
	2016		2015
Accrual for loss contingency related to legal proceedings (Footnote 7)	$	—	$	22,000
Deferred lease liabilities	13,955		13,394
Facility restructuring accrual	1,765		3,006
Deferred income tax liability	3,679		4,734
Other	1,128		1,231
Total	$	20,527	$	44,365