Unamortized Stock-Based Compensation Expenses (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-Based Compensation	$ 1,263	$ 588	$ 3,585	$ 1,656
Unamortized Stock-Based Compensation	6,539	4,072	6,539	4,072
Incentive Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-Based Compensation	80	71	$ 250	$ 252
Remaining Weighted Average Period (years)			3 months 19 days	1 year 2 months 12 days
Unamortized Stock-Based Compensation	94	497	$ 94	$ 497
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-Based Compensation	635	406	$ 2,068	$ 1,100
Remaining Weighted Average Period (years)			1 year 2 months 13 days	1 year 9 months 18 days
Unamortized Stock-Based Compensation	4,475	2,545	$ 4,475	$ 2,545
Performance Based Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-Based Compensation	299	100	$ 920	$ 240
Remaining Weighted Average Period (years)			2 years	1 year 4 months 24 days
Unamortized Stock-Based Compensation	1,901	857	$ 1,901	$ 857
Performance Based Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-Based Compensation	249	11	$ 347	$ 64
Remaining Weighted Average Period (years)			3 months 19 days	1 year 2 months 12 days
Unamortized Stock-Based Compensation	$ 69	$ 173	$ 69	$ 173

Unrecognized cost of unvested share-based compensation awards.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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- Definition

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

Unrecognized cost of unvested share-based awards, other than options, awarded to employees as compensation.

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- Definition

Unrecognized cost of unvested options awarded to employees as compensation.

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

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No definition available.

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