Significant Accounting Policies (Narratives) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Feb. 29, 2016
Significant Accounting Policies Details [Abstract]
Outstanding debt obligations				$ 3,760,000,000
Senior Notes Ultra Petroleum Corp Due 2018	$ 450,000,000			450,000,000
Senior Notes Ultra Petroleum Corp Due 2024	850,000,000			850,000,000
Bank indebtedness current	630,000,000	$ 0		999,000,000
Senior Notes Ultra Resources Inc	$ 1,460,000,000			1,460,000,000
Bank loan borrowings				$ 266,000,000
Restrictive covenants Ultra Resources debt	3.5 to 1.0
Restrictive covenants present value Ultra Resources revolving credit facility	1.5 to 1.0
Restrictive covenants Ultra Petroleum Corp	2.25 to 1.00
Interest payment due Senior Notes Ultra Resources Inc	$ 40,000,000
Principal payment due Senior Notes Ultra Resources Inc	62,000,000
Interest payment due Senior Notes Ultra PetroleumCorp Due 2024	$ 26,000,000
Discount rate future net revenues	10.00%
Ceiling test limitation	$ 3,100,000,000	0	$ 0
Inventory	4,269,000	10,216,000
Valuation allowance	1,300,000,000	161,500,000
Natural gas imbalance liability	$ 1,300,000	$ 3,000,000