Acquisition - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	May 31, 2017	Dec. 31, 2017	Dec. 31, 2016
Noncash Or Part Noncash Acquisitions [Line Items]
Deferred tax assets		$ 21,100
Deferred tax liabilities		100
Deferred credit		$ 11,468	$ 0
NephroGenex, Inc.
Noncash Or Part Noncash Acquisitions [Line Items]
Bankruptcy proceedings unsecured claim in exchange of common stock percentage	100.00%
Consideration paid	$ 1,200
Intangible assets	500
Deferred tax assets	22,200
Tax effected net operating losses	13,500
Tax effected capitalized research and development expenses	8,500
Tax effected federal tax credits	200
Deferred tax liabilities	100
Deferred credit	$ 21,400