Valuation and qualifying accounts (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Allowance for doubtful accounts
Valuation and qualifying accounts
Balance at the beginning of the year	$ 1,051	$ 600	$ 1,247
Additions charged to earnings	577	329	259
Changes to net	39	122	(906)
Balance at the end of the year	1,667	1,051	600
Reserves for inventory
Valuation and qualifying accounts
Balance at the beginning of the year	1,599	1,199	1,288
Additions charged to earnings	1,752	757	715
Changes to net	(899)	(357)	(804)
Balance at the end of the year	2,452	1,599	1,199
Valuation of deferred tax assets
Valuation and qualifying accounts
Balance at the beginning of the year	1,395	1,374	830
Changes to net	205	21	544
Balance at the end of the year	$ 1,600	$ 1,395	$ 1,374

Total of the deductions, net of recoveries, of amounts that had previously been written off as uncollectible, in a given period to allowances and reserves, the valuation and qualifying accounts that are netted against the cost of an asset (in order to value it at its carrying value).

No definition available.

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- Definition

Total of allowances and reserves, the valuation and qualifying accounts that are either netted against the cost of an asset (in order to value it at its carrying value) or that reflect a liability established to represent expected future costs.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24092-122690

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 09

-Article 12

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