Stockholders' Equity (Deficit) - Common Stock and Unvested Share Liability (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Equity [Abstract]
Unvested share liability	$ 24,000	$ 54,000

Liability for unvested cash settled share based payment transactions.

No definition available.

Name:	onct_LiabilityForUnvestedCashSettledShareBasedPaymentTransactions
Namespace Prefix:	onct_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant