Stock-based Compensation Plans - PSUA Activities (Detail) - Performance Shares - $ / shares		12 Months Ended
		Dec. 31, 2015		Dec. 31, 2014
Summary of Performance Share Unit Awards outstanding, Number of Units
Outstanding, Beginning Balance	[1]	134,341		0
Granted	[1]	276,204		227,929
Vested	[1]	(143,094)	[2]	(92,077)	[3]
Forfeited	[1]	(5,327)		(1,511)
Outstanding, Ending Balance	[1]	262,124		134,341
Summary of Performance Share Unit Awards outstanding, Weighted Average Grant Date Fair Value
Outstanding, Beginning Balance, weighted average grant date fair value		$ 86.11		$ 0
Granted, weighted average grant date fair value		56.78		86.14
Vested, weighted average grant date fair value		68.73	[2]	86.23	[3]
Forfeited, weighted average grant date fair value		82.60		82.60
Outstanding, Ending Balance, weighted average grant date fair value		$ 64.77		$ 86.11

[1] These amounts reflect the number of performance units granted. The actual payout of shares may be between zero percent and 150% of the performance units granted depending on the total shareholder return ranking compared to our peer companies at the vesting date.

[2] Includes PSU awards of 19,684 that were modified and fully vested effective with the closing of our Oklahoma City Office and the sale of our Virginia and West Virginia assets.

[3] Primarily represents PSU awards granted to our prior executive chairman for the 2013 calendar year while he was a Range officer.