Property, plant and equipment

12 Months Ended

Dec. 31, 2016

Property Plant And Equipment [Abstract]

3.	Property, plant and equipment

Property, plant and equipment is stated at cost less accumulated depreciation. Costs include all expenditures necessary to place the asset in service, including freight and sales and use taxes. Property, plant and equipment includes instrumentation held by customers, which is generally used to facilitate the implantation of the Company’s products. The useful lives of these assets are as follows:

		Years
Buildings		25 to 33
Plant and equipment		1 to 10
Instrumentation		3 to 4
Computer software		3 to 7
Furniture and fixtures		4 to 8

The Company evaluates the useful lives of these assets on an annual basis. Depreciation is computed on a straight-line basis over the useful lives of the assets. Depreciation of leasehold improvements is computed over the shorter of the lease term or the useful life of the asset. Total depreciation expense was $19.0 million, $19.2 million and $20.6 million for the years ended December 31, 2016, 2015 and 2014, respectively.

Expenditures for maintenance and repairs and minor renewals and improvements, which do not extend the lives of the respective assets, are expensed as incurred. All other expenditures for renewals and improvements are capitalized. The assets and related accumulated depreciation are adjusted for property retirements and disposals, with the resulting gain or loss included in earnings. Fully depreciated assets remain in the accounts until retired from service.

	December 31,
(U.S. Dollars, in thousands)	2016			2015
Cost
Buildings	$	3,225		$	3,328
Plant and equipment		43,745			44,063
Instrumentation		71,962			62,282
Computer software		44,720			24,920
Furniture and fixtures		8,308			5,711
Construction in progress		1,907			19,101
		173,867			159,405
Accumulated depreciation		(124,951	)		(107,099	)
	$	48,916		$	52,306

The Company capitalizes system development costs related to its internal use software during the application development stage. Costs related to preliminary project activities and post implementation activities are expensed as incurred. Internal-use software is amortized on a straight-line basis over its estimated useful life, generally three to seven years. The Company has capitalized computer software, net of accumulated amortization, of $21.3 million and $7.6 million as of December 31, 2016 and 2015, respectively. Amortization of computer software, which is included within total depreciation expense for property, plant and equipment, was $6.4 million, $4.4 million and $3.0 million for the years ended December 31, 2016, 2015 and 2014, respectively.

Long-lived assets are evaluated for impairment whenever events or changes in circumstances have occurred that would indicate impairment. For purposes of the evaluation, the Company groups its long-lived assets with other assets and liabilities at the lowest level of identifiable cash flows if the asset does not generate cash flows independent of other assets and liabilities. If the carrying value of the asset (asset group) exceeds the undiscounted cash flows expected to result from the use and eventual disposition of the asset (asset group), the Company will write the carrying value down to the fair value in the period identified.

The Company generally determines fair value of long-lived assets as the present value of estimated future cash flows. In determining the estimated future cash flows associated with the assets, the Company uses estimates and assumptions about future revenue contributions, cost structures and remaining useful lives of the asset (asset group). The use of alternative assumptions, including estimated cash flows, discount rates, and alternative estimated remaining useful lives could result in different calculations of impairment.