Tax Benefit Preservation Plan / Preferred Stock Rights (Details) - USD ($) $ / shares in Units, $ in Millions	Dec. 31, 2017	Feb. 13, 2014
Class of Stock [Line Items]
Acquired beneficial ownership	50.00%	4.99%
Number of securities called by each right (in shares)		0.001
Exercise price of right (USD per share)		$ 3,000
Series B preferred stock, par value (in usd per share)	$ 0.001
Exercisable rights (in shares)	0
Series B Preferred Stock
Class of Stock [Line Items]
Series B preferred stock, par value (in usd per share)	$ 0.001
Domestic Tax Authority
Class of Stock [Line Items]
Operating loss carryforwards	$ 103.0
State and Local Jurisdiction
Class of Stock [Line Items]
Operating loss carryforwards	$ 26.0