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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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Unrecognized cost of unvested share-based compensation awards.

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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 options awarded to employees as compensation.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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

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Price of a single share of a number of saleable stocks of a company.

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Number of non-vested options forfeited.

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Weighted average grant-date fair value of non-vested options forfeited.

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Amount of stock repurchase plan authorized.

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The number of shares authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan.

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Number of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

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Equity impact of the value of stock that has been repurchased during the period and has not been retired and is not held in treasury. Some state laws may mandate the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

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Total cost of shares repurchased divided by the total number of shares repurchased.

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Stockholders' Equity and Equity Compensation - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Apr. 30, 2018	Oct. 31, 2017
Stockholders' Equity and Equity Compensation (Details) [Line Items]
Share repurchase program, authorized amount	$ 30,000,000.0		$ 30,000,000.0			$ 40,000,000.0
Options forfeited (in shares)			73,897
Options forfeited (in dollars per share)			$ 26.60
Options outstanding (in shares)	52,783		52,783
Weighted average exercise price (in dollars per share)	$ 18.11		$ 18.11
Closing stock price (in dollars per share)	$ 25.38	$ 23.28	$ 25.38	$ 23.28
Stock options awarded during period (in shares)			0	0
Stock Awards
Stockholders' Equity and Equity Compensation (Details) [Line Items]
Share based compensation expense	$ 1,100,000	$ 2,200,000	$ 5,200,000	$ 7,000,000
Unrecognized share based compensation expense	12,400,000		$ 12,400,000
Weighted average recognition period			1 year 10 months 28 days
Deferred Stock Units
Stockholders' Equity and Equity Compensation (Details) [Line Items]
Share based compensation expense	100,000	$ 500,000	$ 1,000,000	1,100,000
Stock Options
Stockholders' Equity and Equity Compensation (Details) [Line Items]
Share based compensation expense			0	$ 0
Unrecognized pre-tax expense related to stock option grants	$ 0		$ 0
Stock Options \| Minimum
Stockholders' Equity and Equity Compensation (Details) [Line Items]
Award vesting period			7 years
Stock Options \| Maximum
Stockholders' Equity and Equity Compensation (Details) [Line Items]
Award vesting period			10 years
2016 Employee Plan
Stockholders' Equity and Equity Compensation (Details) [Line Items]
Stock repurchase program, number of shares authorized to be repurchased (in shares)					1,700,000
Number of shares available for issuance (in shares)	2,667,104		2,667,104
2016 Director Plan
Stockholders' Equity and Equity Compensation (Details) [Line Items]
Number of shares available for issuance (in shares)	73,532		73,532
Equity Compensation Programs
Stockholders' Equity and Equity Compensation (Details) [Line Items]
Share repurchase program, authorized amount	$ 10,000,000		$ 10,000,000
Stock repurchased during period (in shares)			224,700.0	106,164
Stock repurchased during period, value			$ 5,400,000	$ 2,400,000
Shares repurchased, average price per share (in dollars per share)			$ 24.15	$ 22.25
Open Market Repurchase Program
Stockholders' Equity and Equity Compensation (Details) [Line Items]
Stock repurchased during period (in shares)			548,198	1,346,132
Stock repurchased during period, value			$ 13,200,000	$ 29,400,000
Shares repurchased, average price per share (in dollars per share)			$ 24.07	$ 21.81