Shareholders' Equity - Warrants Accounted for As Equity (Details) - $ / shares	1 Months Ended		3 Months Ended	5 Months Ended	6 Months Ended	12 Months Ended
	Oct. 31, 2012	Jan. 31, 2012	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2017	Dec. 31, 2016	Jan. 31, 2017	Aug. 31, 2016	Aug. 12, 2016
2016 Underwritten Public Offering | Pre-funded Warrant | Maxim Group, LLC
Class of Stock [Line Items]
Warrants to purchase common stock (in shares)								311,250
Exercise price of warrants (in USD per share)								$ 0.40
Life of warrants					10 years
Warrants exercised (in shares)			102,500	208,750		208,750
Warrants outstanding (in shares)			102,500		102,500
Warrant | 2012 Underwritten Public Offering
Class of Stock [Line Items]
Warrants to purchase common stock (in shares)	112,500	118,618
Exercise price of warrants (in USD per share)	$ 106.00	$ 56.40
Life of warrants	5 years	5 years
Remaining warrants to purchase common stock (in shares)			111,119		111,119		35,454
Warrant | 2016 Underwritten Public Offering | Maxim Group, LLC
Class of Stock [Line Items]
Warrants to purchase common stock (in shares)			993,115		993,115			993,115
Exercise price of warrants (in USD per share)			$ 0.02		$ 0.02				$ 2.30