Stock Option Plans - Summary of Options Outstanding (Details)	12 Months Ended
Dec. 31, 2018 $ / shares shares
Number outstanding \| shares	1,434,280
Number exercisable \| shares	918,405
$7.30-$10.74
Range of exercise prices, lower range	$ 7.30
Range of exercise prices, upper range	$ 10.74
Number outstanding \| shares	299,180
Options outstanding weighted-average remaining contractual life (years)	3 years
Options outstanding weighted-average exercise price	$ 9.88
Number exercisable \| shares	299,180
Options exercisable weighted-average exercise price	$ 9.88
$10.75-$16.82
Range of exercise prices, lower range	10.75
Range of exercise prices, upper range	$ 16.82
Number outstanding \| shares	262,750
Options outstanding weighted-average remaining contractual life (years)	4 years
Options outstanding weighted-average exercise price	$ 13.62
Number exercisable \| shares	262,750
Options exercisable weighted-average exercise price	$ 13.62
$16.83-$22.08
Range of exercise prices, lower range	16.83
Range of exercise prices, upper range	$ 22.08
Number outstanding \| shares	337,875
Options outstanding weighted-average remaining contractual life (years)	7 years
Options outstanding weighted-average exercise price	$ 19.41
Number exercisable \| shares	244,625
Options exercisable weighted-average exercise price	$ 18.75
$22.09-$23.97
Range of exercise prices, lower range	22.09
Range of exercise prices, upper range	$ 23.97
Number outstanding \| shares	228,200
Options outstanding weighted-average remaining contractual life (years)	10 years
Options outstanding weighted-average exercise price	$ 22.79
Number exercisable \| shares	20,000
Options exercisable weighted-average exercise price	$ 22.66
$23.98-$28.2
Range of exercise prices, lower range	23.98
Range of exercise prices, upper range	$ 28.20
Number outstanding \| shares	306,275
Options outstanding weighted-average remaining contractual life (years)	9 years
Options outstanding weighted-average exercise price	$ 24.87
Number exercisable \| shares	91,850
Options exercisable weighted-average exercise price	$ 25.41

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.

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)
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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.

+ References

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-Publisher FASB
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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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
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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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- Definition

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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