Shareholders' Equity - Shares of Class A common stock reserved for future issuance (Details)	Mar. 31, 2018 shares
Schedule Of Stockholders' Equity [Line Items]
Total shares reserved for future issuance	7,582,009
Common stock warrants outstanding | Derivative liability
Schedule Of Stockholders' Equity [Line Items]
Total shares reserved for future issuance	43,015
Common stock warrants outstanding | Equity security
Schedule Of Stockholders' Equity [Line Items]
Total shares reserved for future issuance	7,538,846
Stock options and grants outstanding under incentive plans
Schedule Of Stockholders' Equity [Line Items]
Total shares reserved for future issuance	148