Stock-Based Plans and Stock-Based Compensation - Stock Option Activity (Details) - Stock options - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2018
Stock Option Activity [Roll Forward]
Outstanding at beginning of period (in shares)	359,713
Granted (in shares)	0
Exercised (in shares)	(43,734)
Cancelled (in shares)	(9,489)
Outstanding at end of period (in shares)	306,490
Weighted Average Exercise Price [Roll Forward]
Outstanding at beginning of period (usd per share)	$ 9.88
Granted (usd per share)	0.00
Exercised (usd per share)	10.29
Cancelled (usd per share)	10.18
Outstanding at end of period (usd per share)	$ 9.82
Options, Additional Disclosures [Abstract]
Options outstanding, Number (in shares)	359,713	306,490
Options exercisable, Number (in shares)		224,714
Options outstanding, Weighted average exercise price (usd per share)	$ 9.88	$ 9.82
Options exercisable, Weighted average exercise price (usd per share)		$ 9.92
Options outstanding, Aggregate intrinsic value		$ 1,384,000
Options exercisable, aggregate intrinsic value		$ 992,000
Options outstanding, Weighted average remaining contractual term	5 years 7 months 47 days
Options exercisable, Weighted average remaining contractual term	5 years 2 months 83 days

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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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Weighted average price of options that were either forfeited or expired.

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The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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

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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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Amount by which current fair value of underlying stock exceeds exercise price of fully vested and expected to vest options outstanding. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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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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