10. Supplementary Balance Sheet Information

The following tables provide the details of selected balance sheet items as of the dates indicated (in thousands):

Inventories

	December 31,
	2017		2016
Raw materials	$	57,277	$	39,822
Work-in-process		14,847		8,012
Finished goods		16,443		9,511
Demo and consigned inventory		2,711		2,400
Total inventories	$	91,278	$	59,745

Property, Plant and Equipment, Net

	December 31,
	2017			2016
Cost:
Land, buildings and improvements	$	53,055		$	38,384
Machinery and equipment		74,122			52,136
Total cost		127,177			90,520
Accumulated depreciation		(65,459	)		(55,099	)
Property, plant and equipment, net	$	61,718		$	35,421

As of December 31, 2017 and 2016, the Company had gross assets under capital lease of $13.6 million and $13.2 million, respectively. The assets acquired under capital leases are included in land, buildings and improvements and machinery and equipment and the related amortization expense is included in depreciation expense. The Company also capitalized software development costs of $2.0 million, $2.3 million and $1.9 million in 2017, 2016 and 2015, respectively, in accordance with the guidance in ASC 350-40, “Internal-Use Software.”

The following table summarizes depreciation expense on property, plant and equipment, including demo units and assets under capital leases (in thousands):

	Year Ended December 31,
	2017		2016		2015
Depreciation expense	$	9,838	$	8,558	$	7,873

The following table summarizes total accumulated depreciation on assets under capital leases as of the dates indicated (in thousands):

	December 31,
	2017		2016
Accumulated depreciation on assets under capital leases	$	6,097	$	4,950

Accrued Expenses and Other Current Liabilities

The following table summarizes accrued expenses and other current liabilities as of the dates indicated (in thousands):

	December 31,
	2017		2016
Accrued compensation and benefits	$	17,348	$	9,647
Accrued warranty		4,835		3,142
Accrued restructuring		440		1,371
Accrued professional services		1,469		1,237
Accrued contingent considerations		2,800		2,775
Customer deposits		3,634		1,164
Other		12,788		7,612
Total	$	43,314	$	26,948

Accrued Warranty

The following table summarizes accrued warranty activities for the periods indicated (in thousands):

	Year Ended December 31,
	2017			2016			2015
Balance at beginning of year	$	3,142		$	3,335		$	3,044
Provision charged to cost of revenue		3,169			1,673			2,025
Warranty liabilities acquired from acquisitions		1,307			23			132
Use of provision		(2,857	)		(1,849	)		(1,454	)
Divestiture of JK Lasers		—			—			(389	)
Foreign currency exchange rate changes		74			(40	)		(23	)
Balance at end of year	$	4,835		$	3,142		$	3,335

Other Long Term Liabilities

The following table summarizes other long term liabilities as of the dates indicated (in thousands):

	December 31,
	2017		2016
Capital lease obligations	$	7,947	$	8,111
Accrued pension liabilities		3,853		5,957
Accrued contingent considerations		1,304		2,381
Other		2,037		2,264
Total	$	15,141	$	18,713