Stock Incentive Plans (Details 4)	9 Months Ended
Sep. 30, 2019 shares
Share-based Payment Arrangement [Abstract]
Non-vested restricted stock, Beginning balance	2,454
Granted
Vested	(2,454)
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_ShareBasedCompensationArrangementByShareBasedPaymentAwardRestrictedStockNonvestedNumber
Namespace Prefix:	rbcn_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant