Warrants, Restricted Stock, Restricted Stock Units, Options and Option Matching Rights Warrants, Restricted Stock, Restricted Stock Units, Options and Option Matching Rights - Option Matching Rights (Details) - $ / shares	Aug. 19, 2009	Jan. 24, 2018	Dec. 31, 2017	Dec. 31, 2016	Feb. 17, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of securities declined to exercise (in shares)						204,706
Class of warrant or right, outstanding (in shares)				133,000
Number of shares that may be purchased by warrants (shares)			60,000	83,334
Exercise price of right (usd per right)			$ 81.50	$ 30.00
Option Matching Rights [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Class of Warrant or Right, Number of Securities Exercised to Trigger Option Matching Rights	200,000
Class of Warrant or Right, Option Exercise Notice	5 days
Class of Warrant or Right, Option Exercise, Second Notice	10 days
Number of securities declined to exercise (in shares)					204,706
Class of Warrant or Right, Option Cancellation Notice	10 days
Class of warrant or right, outstanding (in shares)			3,000
Subsequent Event | Option Matching Rights [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of securities declined to exercise (in shares)		1,666
Number of shares that may be purchased by warrants (shares)		1,666
Exercise price of right (usd per right)		$ 14.95