Basis of Presentation and Accounting Policies (Details)	9 Months Ended
	Sep. 30, 2017 segment	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Accounting Policies [Abstract]
Number of operating segments | segment	1
Accounting Standards Update 2016-09, Excess Tax Benefit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating loss carryforwards		$ 410,800,000	$ 410,800,000
Deferred income tax assets, net			3,400,000
Accounting Standards Update 2016-09, Forfeiture Rate Component | Accumulated Deficit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle in period of adoption			9,371,000
Accounting Standards Update 2016-09, Forfeiture Rate Component | Additional Paid-in Capital
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle in period of adoption			(9,371,000)
Accounting Standards Update 2016-09 | Accumulated Deficit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle in period of adoption			$ 0
Domestic Tax Authority | Accounting Standards Update 2016-09, Excess Tax Benefit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating loss carryforwards		404,700,000
State and Local Jurisdiction | Accounting Standards Update 2016-09, Excess Tax Benefit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating loss carryforwards		$ 6,100,000