Stockholders' Equity and Stock Plans - Dividends (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Equity [Abstract]
Cash dividends to common stockholders	$ 8,860	$ 6,896
Cash dividends per common share (usd per share)	$ 0.64	$ 0.56
Retained earnings	$ 179,944	$ 155,544
Stockholders' equity	$ 316,407	$ 297,025	$ 230,563
Period used to determine amount available for payment of dividends based on restriction (in years)	3 years
Amount of retained earnings available for payment of dividends based on restriction	$ 24,900
Cash held	$ 19,100

Dividends, Cash Dividend, Amount Retained Earnings Available for Dividend Payments Under Restriction

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- Definition

Dividends, Cash Dividend, Period Restricted Payment Amount is Determined

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- Definition

Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Excludes cash and cash equivalents within disposal group and discontinued operation.

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- Definition

Aggregate dividends paid during the period for each share of common stock outstanding.

+ References

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Amount of paid and unpaid common stock dividends declared with the form of settlement in cash.

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- Definition

The cumulative amount of the reporting entity's undistributed earnings or deficit.

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Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

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