CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash flows from operating activities:
Non-cash impairments	$ 0	$ 0	$ 1,891

The loss (gain) resulting from the write-down of the carrying value of assets classified as a discontinued operation, to fair value less cost to sell.

No definition available.

Name:	useg_DiscontinuedOperationLossGainOnWriteDown
Namespace Prefix:	useg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration