Stock-Based Compensation Plans - PSUA Activity (Detail) (Performance Shares, USD $)	9 Months Ended
	Sep. 30, 2014
Performance Shares
Summary of Performance Share Unit Awards outstanding, Number of Units
Outstanding, Beginning Balance	0
Units granted	227,929	[1]
Units vested	(69,411)	[2]
Outstanding, Ending Balance	158,518
Summary of Performance Share Unit Awards outstanding, Weighted Average Grant Date Fair Value
Outstanding, Beginning Balance	$ 0
Weighted average grant date fair value	$ 86.14	[1]
Units vested	$ 86.30	[2]
Outstanding, Ending Balance	$ 86.07

[1] Amounts granted 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 the peer companies at the vesting date.

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