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Stock-Based Compensation (Stock Options by Exercise Price Range) (Details)	12 Months Ended
	Dec. 31, 2017 $ / shares shares
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options outstanding, shares | shares	327,270
Options outstanding, weighted average remaining contractual life	4 years 2 months 43 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 20.21
Options exercisable, shares | shares	278,689
Options exercisable, weighted average exercise price (in dollars per share)	$ 19.12
Range of Exercise Prices: $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 dollars per share)	0.01
Range of exercise prices, upper limit (in dollars per share)	$ 15.70
Options outstanding, shares | shares	65,852
Options outstanding, weighted average remaining contractual life	1 year 5 months 52 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 9.82
Options exercisable, shares | shares	65,852
Options exercisable, weighted average exercise price (in dollars per share)	$ 9.82
Range of Exercise Prices: $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 dollars per share)	15.71
Range of exercise prices, upper limit (in dollars per share)	$ 17.81
Options outstanding, shares | shares	72,750
Options outstanding, weighted average remaining contractual life	1 year 7 months 75 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 17.53
Options exercisable, shares | shares	72,750
Options exercisable, weighted average exercise price (in dollars per share)	$ 17.53
Range of Exercise Prices: $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 dollars per share)	17.82
Range of exercise prices, upper limit (in dollars per share)	$ 20.48
Options outstanding, shares | shares	56,750
Options outstanding, weighted average remaining contractual life	3 years 5 months 45 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 19.36
Options exercisable, shares | shares	56,750
Options exercisable, weighted average exercise price (in dollars per share)	$ 19.36
Range of Exercise Prices: $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 dollars per share)	20.49
Range of exercise prices, upper limit (in dollars per share)	$ 33.36
Options outstanding, shares | shares	131,918
Options outstanding, weighted average remaining contractual life	7 years 3 months 33 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 27.23
Options exercisable, shares | shares	83,337
Options exercisable, weighted average exercise price (in dollars per share)	$ 27.70

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(iii)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(i)-(ii)
-URI http://asc.fasb.org/extlink&oid=6415400&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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iii)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(i)-(ii)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (e)(1)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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