Goodwill and intangible assets (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2017	Dec. 31, 2016
Indefinite-lived Intangible Assets [Line Items]
GrossCarryingAmount	$ 4,686	$ 4,686
AccumulatedAmortization	1,509	1,387
Net	$ 3,177	3,299
License Agreement Terms [Member]
Indefinite-lived Intangible Assets [Line Items]
Amortization Period(in years)	10 years
GrossCarryingAmount	$ 1,000	1,000
AccumulatedAmortization	242	217
Net	$ 758	783
Trade Names [Member]
Indefinite-lived Intangible Assets [Line Items]
Amortization Period(in years)	2 years
GrossCarryingAmount	$ 30	30
AccumulatedAmortization	30	30
Net	$ 0	0
Patents [Member]
Indefinite-lived Intangible Assets [Line Items]
Amortization Period(in years)	5 years
GrossCarryingAmount	$ 386	386
AccumulatedAmortization	369	366
Net	17	20
Noncompete Agreements [Member]
Indefinite-lived Intangible Assets [Line Items]
GrossCarryingAmount	1,270	1,270
AccumulatedAmortization	360	322
Net	$ 910	948
Noncompete Agreements [Member] \| Maximum [Member]
Indefinite-lived Intangible Assets [Line Items]
Amortization Period(in years)	10 years
Noncompete Agreements [Member] \| Minimum [Member]
Indefinite-lived Intangible Assets [Line Items]
Amortization Period(in years)	6 years
Customer Relationships [Member]
Indefinite-lived Intangible Assets [Line Items]
GrossCarryingAmount	$ 2,000	2,000
AccumulatedAmortization	508	452
Net	$ 1,492	$ 1,548
Customer Relationships [Member] \| Maximum [Member]
Indefinite-lived Intangible Assets [Line Items]
Amortization Period(in years)	10 years
Customer Relationships [Member] \| Minimum [Member]
Indefinite-lived Intangible Assets [Line Items]
Amortization Period(in years)	3 years

Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

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Amount before amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

+ References

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Amount after amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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Remaining amortization period of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

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