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Stock-Based Compensation - Stock Options Outstanding (Details)	9 Months Ended
	Sep. 30, 2018 $ / shares shares
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options outstanding, shares | shares	283,686
Options outstanding, weighted average remaining contractual life (years)	3 years 9 months 29 days
Options outstanding, weighted average exercise price (in USD per share)	$ 20.46
Options exercisable, shares | shares	262,821
Options exercisable, weighted average exercise price (in USD per share)	$ 19.85
$0.01-15.70
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise prices, lower limit (in USD per share)	0.01
Range of exercise prices, upper limit (in USD per share)	$ 15.70
Options outstanding, shares | shares	64,852
Options outstanding, weighted average remaining contractual life (years)	9 months 7 days
Options outstanding, weighted average exercise price (in USD per share)	$ 9.75
Options exercisable, shares | shares	64,852
Options exercisable, weighted average exercise price (in USD per share)	$ 9.75
$15.71-17.81
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise prices, lower limit (in USD per share)	15.71
Range of exercise prices, upper limit (in USD per share)	$ 17.81
Options outstanding, shares | shares	42,000
Options outstanding, weighted average remaining contractual life (years)	1 year 9 months 25 days
Options outstanding, weighted average exercise price (in USD per share)	$ 17.54
Options exercisable, shares | shares	42,000
Options exercisable, weighted average exercise price (in USD per share)	$ 17.54
$17.82-20.48
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise prices, lower limit (in USD per share)	17.82
Range of exercise prices, upper limit (in USD per share)	$ 20.48
Options outstanding, shares | shares	50,500
Options outstanding, weighted average remaining contractual life (years)	2 years 7 months 2 days
Options outstanding, weighted average exercise price (in USD per share)	$ 19.43
Options exercisable, shares | shares	50,500
Options exercisable, weighted average exercise price (in USD per share)	$ 19.43
$20.49-33.36
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise prices, lower limit (in USD per share)	20.49
Range of exercise prices, upper limit (in USD per share)	$ 33.36
Options outstanding, shares | shares	126,334
Options outstanding, weighted average remaining contractual life (years)	6 years 6 months 25 days
Options outstanding, weighted average exercise price (in USD per share)	$ 27.35
Options exercisable, shares | shares	105,469
Options exercisable, weighted average exercise price (in USD per share)	$ 27.19

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The floor of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
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-Section 50
-Paragraph 2
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The number of shares reserved for issuance pertaining to the outstanding exercisable stock options as of the balance sheet date in the customized range of exercise prices for which the market and performance vesting condition has been satisfied.

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The number of shares reserved for issuance pertaining to the outstanding stock options as of the balance sheet date for all option plans in the customized range of exercise prices.

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The ceiling of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

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Weighted average exercise price as of the balance sheet date for those equity-based payment arrangements exercisable and outstanding.

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The weighted average price as of the balance sheet date at which grantees could acquire the underlying shares with respect to all outstanding stock options which are in the customized range of exercise prices.

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

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