Income Taxes (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015
Operating Loss Carryforwards [Line Items]
Valuation allowance increase (decrease)	$ 3.6	$ 3.4
ASU 2016-09 [Member]
Operating Loss Carryforwards [Line Items]
Valuation allowance increase (decrease)	0.9
Federal [Member]
Operating Loss Carryforwards [Line Items]
Pre-tax net operating loss carryforwards	65.6
Federal research and development tax credits	$ 10.4
Federal [Member] \| Minimum [Member]
Operating Loss Carryforwards [Line Items]
Expiration date of pre-tax net operating loss carryforwards	Jan. 01, 2029
Expiration date of federal research and development tax credits	Jan. 01, 2023
Federal [Member] \| Maximum [Member]
Operating Loss Carryforwards [Line Items]
Expiration date of pre-tax net operating loss carryforwards	Jan. 01, 2036
Expiration date of federal research and development tax credits	Jan. 01, 2036

Amount of operating loss carryforward, before tax effects, available to reduce future taxable income under enacted tax laws.

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The amount of the tax credit carryforward, before tax effects, available to reduce future taxable income under enacted tax laws.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=65882285&loc=d3e32559-109319

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Carryforwards
-URI http://asc.fasb.org/extlink&oid=6506874

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Amount of increase (decrease) in the valuation allowance for a specified deferred tax asset.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 45
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=75116654&loc=d3e32123-109318

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