Stock Incentive Plans (Details 3)	6 Months Ended
Jun. 30, 2020 shares
Share-based Payment Arrangement [Abstract]
Non-vested restricted stock, Beginning balance
Granted
Vested
Non-vested restricted stock, Ending balance

The number of non-vested equity-based payment instruments are outstanding as of the balance sheet date.

No definition available.

Name:	rbcn_ShareBasedCompensationArrangementByShareBasedPaymentAwardRestrictedStockNonvestedNumbers
Namespace Prefix:	rbcn_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration