Summary of Significant Accounting Policies - Stock option equivalents (Details) - shares	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total number of common stock equivalents outstanding (in shares)	404,000	1,888,000	1,979,800
Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total number of common stock equivalents outstanding (in shares)	34,000	57,000	156,200
Warrants [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total number of common stock equivalents outstanding (in shares)	133,000	133,000	216,600
Option matching rights [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total number of common stock equivalents outstanding (in shares)	21,000	229,000	238,000
Restricted stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total number of common stock equivalents outstanding (in shares)	216,000	137,000	37,000
Shares to be issued upon conversion of convertible of long-term loan, related party [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total number of common stock equivalents outstanding (in shares)	0	1,332,000	1,332,000