Significant Accounting Policies - Net Loss Per Share, Basic and Diluted (Details) - $ / shares	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016
Accounting Policies [Abstract]
Difference between basic net loss per share and diluted net loss per share (usd per share)	$ 0	$ 0

The amount of difference between basic net income (loss) per share and diluted net income (loss) per share due to the impact of anti-dilutive items during the period.

No definition available.

Name:	cerc_DifferenceBetweenBasicAndDilutedNetIncomeLossPerShare
Namespace Prefix:	cerc_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration