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Stock-based Compensation and Other Employee Benefit Plans Stock-based Compensation: Incentive Award Plan and Employee Stock Purchase Plan (Range of Prices) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price, low end of the range (in dollars per share)	$ 4.44
Exercise price, high end of the range (in dollars per share)	$ 16.51
Options outstanding (in shares)	132,670
Options outstanding - weighted average remaining contractual life (years)	3 years 9 months 18 days	4 years 3 months 18 days
Options outstanding - weighted average exercise price (in dollars per share)	$ 12.79	$ 12.10
Options exercisable - at the end of period (in shares)	132,670
Options exercisable - weighted average exercise price (in dollars per share)	$ 12.79
$4.44 - 7.31
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price, low end of the range (in dollars per share)	4.44
Exercise price, high end of the range (in dollars per share)	$ 7.31
Options outstanding (in shares)	25,653
Options outstanding - weighted average remaining contractual life (years)	1 year 7 months 6 days
Options outstanding - weighted average exercise price (in dollars per share)	$ 6.25
Options exercisable - at the end of period (in shares)	25,653
Options exercisable - weighted average exercise price (in dollars per share)	$ 6.25
$7.39 - 7.39
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price, low end of the range (in dollars per share)	7.39
Exercise price, high end of the range (in dollars per share)	$ 7.39
Options outstanding (in shares)	3,500
Options outstanding - weighted average remaining contractual life (years)	2 years 3 months 18 days
Options outstanding - weighted average exercise price (in dollars per share)	$ 7.39
Options exercisable - at the end of period (in shares)	3,500
Options exercisable - weighted average exercise price (in dollars per share)	$ 7.39
$8.26 - 8.26
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price, low end of the range (in dollars per share)	8.26
Exercise price, high end of the range (in dollars per share)	$ 8.26
Options outstanding (in shares)	12,023
Options outstanding - weighted average remaining contractual life (years)	3 years
Options outstanding - weighted average exercise price (in dollars per share)	$ 8.26
Options exercisable - at the end of period (in shares)	12,023
Options exercisable - weighted average exercise price (in dollars per share)	$ 8.26
$10.46 - 10.46
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price, low end of the range (in dollars per share)	10.46
Exercise price, high end of the range (in dollars per share)	$ 10.46
Options outstanding (in shares)	16,494
Options outstanding - weighted average remaining contractual life (years)	3 years 10 months 24 days
Options outstanding - weighted average exercise price (in dollars per share)	$ 10.46
Options exercisable - at the end of period (in shares)	16,494
Options exercisable - weighted average exercise price (in dollars per share)	$ 10.46
$16.51 - 16.51
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price, low end of the range (in dollars per share)	16.51
Exercise price, high end of the range (in dollars per share)	$ 16.51
Options outstanding (in shares)	75,000
Options outstanding - weighted average remaining contractual life (years)	4 years 8 months 12 days
Options outstanding - weighted average exercise price (in dollars per share)	$ 16.51
Options exercisable - at the end of period (in shares)	75,000
Options exercisable - weighted average exercise price (in dollars per share)	$ 16.51

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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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- Definition

The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

+ 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=96867065&loc=d3e5070-113901

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

+ 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=96867065&loc=d3e5070-113901

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Number of options outstanding, including both vested and non-vested options.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

Reference 2: 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=96867065&loc=d3e5070-113901

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

+ 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)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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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.

+ 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=96867065&loc=d3e5070-113901

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- Definition

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=96867065&loc=d3e5070-113901

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Weighted average remaining contractual term for option awards outstanding, 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=96867065&loc=d3e5070-113901

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