Stock-Based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2017	Dec. 31, 2016
Number of Stock Options
Outstanding, beginning of period (in shares)	350,186
Granted (in shares)	32,750
Exercised (in shares)	(25,580)
Outstanding, end of period (in shares)	357,356	350,186
Exercisable (in shares)	307,108
Weighted Average Exercise Price
Outstanding, beginning of period (in USD per share)	$ 19.45
Granted (in USD per share)	28.15
Exercised (in USD per share)	20.19
Outstanding, end of period (in USD per share)	20.19	$ 19.45
Exercisable (in USD per share)	$ 19.19
Weighted Average Remaining Contractual Life (years)
Outstanding	4 years 1 month 34 days	4 years 2 months 29 days
Exercisable	3 years 4 months 38 days
Aggregate Intrinsic Value
Outstanding, beginning of period	$ 4,453
Exercised	271
Outstanding, end of period	3,050	$ 4,453
Exercisable	$ 2,946

Share-based Compensation Arrangements by Share-based Payment Award, Options, Intrinsic Value [Abstract]

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Share-based Compensation Arrangements by Share-based Payment Award, Options, Weighted Average Remaining Contractual Term [Abstract]

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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iii)
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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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Gross number of share options (or share units) granted during the period.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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Number of options outstanding, including both vested and non-vested options.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Number of share options (or share units) exercised during the current period.

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