Stock-Based Compensation - Summary of stock options outstanding and exercisable (Details)	12 Months Ended
Dec. 31, 2018 $ / shares shares
Options Outstanding and Exercisable
Number Of Options \| shares	76,764
Weighted-Average Exercise Price	$ 22.35
Weighted-Average Remaining Contractual Term	2 years 10 months 24 days
Range Of Exercise Prices From Dollars 17.18 To 17.18
Stock options outstanding
Exercise price, low end of range	$ 17.18
Exercise price, high end of range	$ 17.18
Options Outstanding and Exercisable
Number Of Options \| shares	7,587
Weighted-Average Exercise Price	$ 17.18
Weighted-Average Remaining Contractual Term	1 year 2 months 12 days
Range Of Exercise Prices From Dollars 17.48 To 17.48
Stock options outstanding
Exercise price, low end of range	$ 17.48
Exercise price, high end of range	$ 17.48
Options Outstanding and Exercisable
Number Of Options \| shares	15,654
Weighted-Average Exercise Price	$ 17.48
Weighted-Average Remaining Contractual Term	3 years 1 month 6 days
Range Of Exercise Prices From Dollars 24.18 To 24.18
Stock options outstanding
Exercise price, low end of range	$ 24.18
Exercise price, high end of range	$ 24.18
Options Outstanding and Exercisable
Number Of Options \| shares	17,948
Weighted-Average Exercise Price	$ 24.18
Weighted-Average Remaining Contractual Term	2 years 2 months 12 days
Range Of Exercise Prices From Dollars 24.68 To 24.68
Stock options outstanding
Exercise price, low end of range	$ 24.68
Exercise price, high end of range	$ 24.68
Options Outstanding and Exercisable
Number Of Options \| shares	35,575
Weighted-Average Exercise Price	$ 24.68
Weighted-Average Remaining Contractual Term	3 years 6 months

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

+ References

No definition available.

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- Definition

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

+ References

No definition available.

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- Definition

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

+ References

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- Definition

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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

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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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