Stock Incentive Plans - Summary of Stock Incentive Plans (Details) - USD ($)			1 Months Ended	6 Months Ended		12 Months Ended
	Jan. 01, 2019	May 12, 2015	Feb. 28, 2019	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Shares Available for Grant
Beginning balance (in shares)	2,327			2,327
Ending balance (in shares)				13,622		2,327
Stock Options Outstanding
Beginning balance (in shares)	42,979			42,979
Ending balance (in shares)				39,481		42,979
RSUs Outstanding
Beginning balance (in shares)	5,613			5,613
Ending balance (in shares)				5,613		5,613
Options vested, exercisable and expected to vest
Weighted average grant date fair value of stock options granted (in dollars per share)				$ 17.05	$ 119.00
Number of options vested (in shares)				10,598	5,648
Weighted average fair value of options vested on grant date				$ 2,388,019	$ 177,862
Inducement options issued and outstanding
Stock Options Outstanding
Beginning balance (in shares)	2,985			2,985
Options granted (in shares)						2,993
Ending balance (in shares)				906		2,985
Options vested, exercisable and expected to vest
Weighted average grant date fair value of stock options granted (in dollars per share)						$ 93.80
Common Stock
Options vested, exercisable and expected to vest
Share Price				$ 4.70
2013 Plan
Stock Based Compensation
Option shares outstanding				5,613
2013 Plan | Stock options
Stock Options Outstanding
Options granted (in shares)				0
2014 Plan
Stock Based Compensation
Option shares outstanding				39,481
Shares Available for Grant
Beginning balance (in shares)	2,327			2,327
Additional shares authorized (in shares)				7,797
Options granted (in shares)				(69)
Options cancelled (in shares)				3,567
Ending balance (in shares)				13,622		2,327
Stock Options Outstanding
Beginning balance (in shares)	42,979			42,979
Options granted (in shares)				69
Options cancelled (in shares)				(3,567)
Ending balance (in shares)				39,481		42,979
RSUs Outstanding
Beginning balance (in shares)	5,613			5,613
Ending balance (in shares)				5,613		5,613
Weighted Average Stock Option Exercise Price
Beginning balance (in dollars per share)	$ 406.36			$ 406.36
Options granted (in dollars per share)				17.24
Options cancelled (in dollars per share)				122.50
Ending balance (in dollars per share)				$ 431.51		$ 406.36
Weighted Average Remaining Contractual Life (Years)
Weighted Average Remaining Contractual Life (Years)				8 years 8 months 27 days		9 years 2 months 27 days
Options vested, exercisable and expected to vest
Options vested and exercisable (in shares)				18,073
Options vested and exercisable (in dollars per share)				$ 597.95
Options vested and exercisable (in years)				8 years 7 months 2 days
Options vested and expected to vest (in shares)				38,753
Options vested and expected to vest (in dollars per share)				$ 431.51
Options vested and expected to vest (in years)				8 years 8 months 27 days
Options exercised (in shares)				0	0
2014 Plan | Stock options
Stock Based Compensation
Increase in share reserve based on outstanding number of shares (as a percent)		2.00%
Shares Available for Grant
Additional shares authorized (in shares)	7,797
Options vested, exercisable and expected to vest
Extension period			5 years