Income Taxes - Additional Information (Detail)	9 Months Ended	12 Months Ended
Sep. 30, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Valuation allowance	100.00%	100.00%

Deferred tax assets valuation allowance percentage.

No definition available.

Name:	cprx_DeferredTaxAssetsValuationAllowancePercentage
Namespace Prefix:	cprx_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration