Chapter 11 Proceedings - Costs of Reorganization (Parenthetical) (Details) $ in Millions	9 Months Ended
Sep. 30, 2017 USD ($)
Reorganization Items [Abstract]
Accrued and unpaid professional fees	$ 3.8

Amount of accrued and unpaid reorganization items related to legal and advisory professional fees related to entities in bankruptcy.

No definition available.

Name:	upl_NoncashReorganizationItemsLegalAndAdvisoryProfessionalFees
Namespace Prefix:	upl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration