Document and Entity Information (USD $)	6 Months Ended
	Jun. 30, 2013	Jul. 23, 2013	Jun. 30, 2012
Document and Entity Information
Entity Registrant Name	Ultra Petroleum Corp.
Entity Central Index Key	0001022646
Document Type	10-Q
Document Period End Date	Jun. 30, 2013
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 3,528,103,567
Entity Common Stock, Shares Outstanding		152,976,084
Document Fiscal Year Focus	2013
Document Fiscal Period Focus	Q2