Income Taxes Components of Deferred Tax asset/ liability (Textual) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($)
State and Local Jurisdiction [Member]
Components of deferred tax assets and liabilities [Line Items]
Operating Loss Carryforwards	$ 107.3
State and Local Jurisdiction [Member] | Research Tax Credit Carryforward [Member]
Components of deferred tax assets and liabilities [Line Items]
Tax Credit Carryforward, Amount	16.5
Domestic Tax Authority [Member]
Components of deferred tax assets and liabilities [Line Items]
Operating Loss Carryforwards	$ 261.2
Operating Loss Carryforwards, Expiration Dates	Dec. 31, 2037
Domestic Tax Authority [Member] | Research Tax Credit Carryforward [Member]
Components of deferred tax assets and liabilities [Line Items]
Tax Credit Carryforward, Amount	$ 11.4
Tax Credit Carryforward, Expiration Date	Dec. 31, 2037