Fair value measurements - Summary of Change in Fair Value of Contingent Consideration (Detail) $ in Thousands	6 Months Ended
Jun. 30, 2018 USD ($)
Business Combination Increase Decrease To Reflect Liabilities Acquired At Fair Value [Abstract]
Beginning Balance	$ 1,834
Preliminary purchase price	3,360
Fair value adjustments	(544)
Accretion in value	235
Amounts paid to sellers	(400)
Ending Balance	$ 4,485

Business combination contingent consideration arrangements payment.

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- Definition

Business combination contingent consideration fair value adjustments.

+ References

No definition available.

+ Details

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- Definition

Business Combination Increase Decrease To Reflect Liabilities Acquired At Fair Value [Abstract]

+ References

No definition available.

+ Details

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- Definition

Contingent consideration preliminary purchase price.

+ References

No definition available.

+ Details

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- Definition

Amount of increase (decrease) in the value of a contingent consideration liability, including, but not limited to, differences arising upon settlement.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 4
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e7008-128479

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- Definition

Fair value of contingent consideration in a business combination that is classified in shareholders' equity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

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