Supplementary Balance Sheet Information (Tables)

12 Months Ended

Dec. 31, 2017

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Aggregate Fair Value and Unrealized Holding Gains and Losses by Major Security Type

The amortized cost basis, aggregate fair value and unrealized holding gains and losses by major security type were as follows:

Available-for-sale securities:

	December 31, 2017
	Amortized cost		Aggregate fair value		Unrealized gains		Unrealized losses
	$ in thousands
Government and corporate bonds:
Classified as long-term*		7,969		7,888		9		(90	)

	December 31, 2016
	Amortized cost		Aggregate fair value		Unrealized gains		Unrealized losses
	$ in thousands
Government and corporate bonds:
Classified as long-term*		7,146		7,012		9		(143	)

* Mature in less than five years.

Balance and Changes in Allowance

Trade accounts receivable are presented net of an allowance for doubtful accounts, the balance and the changes in the allowance are comprised as follows:

	Year ended December 31
	2017			2016			2015
	$ in thousands
Balance at beginning of year		3,708			2,893			3,432
Increase (decrease) during the year		962			1,174			(206	)
Bad debt written off		(1,556	)		(359	)		(333	)
Balance at end of year		3,114			3,708			2,893

Accounts Payable and Accruals Other

d. Accounts payable and accruals - other

	December 31
	2017		2016
	$ in thousands
Employees and employee institutions		44,637		35,832
Government departments and agencies		17,760		25,492
Derivative liabilities		1,214		9,619
Accrued expenses		59,627		43,392
Sundry		272		357
		123,510		114,692

Schedule of Deferred Revenue

e. Deferred income

	December 31
	2017		2016
	$ in thousands
Deferred income relating to warranty and installations commitments*		32,084		24,177
Other deferred income		5,361		4,399
		37,445		28,576

* The changes in deferred income relating to warranty and installation commitments:

Changes in Deferred Revenues

	December 31
	2017			2016
	$ in thousands
Balance at beginning of year		24,177			22,221
Revenue recognized during the year		(34,849	)		(35,901	)
Deferred income acquired					321
Deferred income relating to new sales		42,756			37,536
Balance at end of year		32,084			24,177

Accumulated Other Comprehensive Income (Loss)

f. Accumulated other comprehensive income (loss)

	December 31
	2017			2016			2015
	$ in thousands
Accumulated loss in respect of derivative instruments designated for cash flows hedge, net of tax		333			(9,087	)		(1,477	)
Accumulated realized and unrealized loss on available-for-sale securities, net of tax		(81	)		(134	)		(29	)
		252			(9,221	)		(1,506	)