Stock-Based Compensation - Employee Stock Purchase Plan (Details) - USD ($)	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense (less than .1 million in 2016)	$ 1,313,000	$ 852,000
Employee stock purchase plan \| Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for future grant	1,616,342
Shares reserved for grant, annual increase period	9 years
Annual automatic increase in shares available, percentage of each class of common stock outstanding	1.00%
Annual automatic increase in shares available, shares	1,500,000
Purchase price of shares as a percentage of fair market value	90.00%
Maximum number of shares participant may purchase, fair market value (not to exceed)	$ 15,000
Maximum number of shares participant may purchase as a percentage of base compensation (not to exceed)	10.00%
Shares purchased by employees	13,584	18,705
Stock-based compensation expense (less than .1 million in 2016)	$ 100,000	$ 100,000
Employee stock purchase plan \| Employee Stock \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Discount of the market value on the date of purchase (not to exceed) (percentage)	10.00%

Common Stock, Capital Shares Reserved for Future Issuance, Annual Increase, Percentage of Each Class Outstanding

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Common Stock, Capital Shares Reserved for Future Issuance, Annual Increase, Shares

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Common Stock, Capital Shares Reserved for Future Issuance, Annual Increase, Term

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- Definition

Share-based Compensation Arrangement by Share-based Payment Award, Maximum Fair Market Value of Shares Per Employee

+ References

No definition available.

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- Definition

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.F)
-URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
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-Name Accounting Standards Codification
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- Definition

Aggregate number of common shares reserved for future issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.29)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

Discount rate from fair value on purchase date that participants pay for shares.

+ 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=6415400&loc=d3e5070-113901

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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 highest percentage of annual salary that an employee is permitted to utilize with respect to the plan.

+ References

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- Definition

Purchase price of common stock expressed as a percentage of its fair value.

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- Definition

Number of shares issued during the period as a result of an employee stock purchase plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
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-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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-Name Accounting Standards Codification
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