Stock-Based Compensation - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award
Stock compensation expense	$ 4,376	$ 3,959	$ 3,634
Tax benefits from stock-based compensation	$ 2,146	$ 1,443	2,193
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	0	0
Stock Option
Share-based Compensation Arrangement by Share-based Payment Award
Stock compensation expense	$ 39	$ 481	905
Tax benefits from stock-based compensation	15	184	346
Intrinsic value of fully-vested stock options outstanding	24,255
Total intrinsic value of options exercised	5,572	3,931	7,363
Tax benefit realized from stock option exercises	2,131	1,504	2,594
Proceeds from stock options exercised	4,683	3,369	6,299
Common stock redeemed for payment of stock option exercises, aggregate value	3,117	2,507	6,829
Share-Based CompensationaArrangement By Share Based Payment Award, Options, Vested In Period, Fair Value	411
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award
Stock compensation expense	3,864	2,888	2,109
Tax benefits from stock-based compensation	$ 1,478	$ 1,104	$ 807
Unrecognized compensation cost related to nonvested restricted stock to be recognized over weighted average period (in years)	1 year 9 months 10 days
Stock issued during period, shares, restricted stock award	190,239
Unrecognized compensation cost related to nonvested restricted stock awards	$ 4,835
Restricted Stock \| Upon Achievement of Performance Goals
Share-based Compensation Arrangement by Share-based Payment Award
Stock issued during period, shares, restricted stock award	98,352
Restricted Stock \| Upon Achievement of Defined Return on Asset Performance Goals
Share-based Compensation Arrangement by Share-based Payment Award
Stock issued during period, shares, restricted stock award	30,424
Restricted Stock \| Upon Achievement of Defined Return on Equity Performance Goals
Share-based Compensation Arrangement by Share-based Payment Award
Stock issued during period, shares, restricted stock award	30,424
Restricted Stock \| Upon Achievement of Defined Total Return to Shareholder Goals
Share-based Compensation Arrangement by Share-based Payment Award
Stock issued during period, shares, restricted stock award	30,424
Restricted Stock \| Upon One-Third Annual Anniversary
Share-based Compensation Arrangement by Share-based Payment Award
Stock issued during period, shares, restricted stock award	91,385
2006 Plan \| Stock Option
Share-based Compensation Arrangement by Share-based Payment Award
Shares available for grant	1,954,792

Common Stock Redeemed For Payment of Stock Option Exercises, Aggregate Value

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Share-Based CompensationaArrangement By Share Based Payment Award, Options, Vested In Period, Fair Value

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Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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

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The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period.

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Disclosure of the aggregate tax benefit realized from the exercise of stock options and the conversion of similar instruments during the annual period.

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The cash inflow associated with the amount received from holders exercising their stock options. This item inherently excludes any excess tax benefit, which the entity may have realized and reported separately.

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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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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 fully vested and expected to vest options outstanding.

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Number of shares issued during the period related to Restricted Stock Awards, net of any shares forfeited.

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