Note 4 - Cash, Cash Equivalents, and Restricted Cash - Cash, Cash Equivalents and Restricted Cash (Details) (Parentheticals)	Dec. 31, 2019	Dec. 31, 2018
Reverse Repurchase Agreements [Member]
Collateralized, percent	102.00%	102.00%

The percent of principal for collateral held for cash equivalents.

No definition available.

Name:	oxfd_CashEquivalentsCollateralPercentOfPrincipal
Namespace Prefix:	oxfd_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant