Reconciliation of Beginning and Ending Aggregate Carrying Amount of Asset Retirement Obligation (Parenthetical) (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012		Dec. 31, 2011
Reconciliation of Changes in Asset Retirement Obligations [Line Items]
Accretion of asset retirement obligations	$ 48,996	$ 38,361	[1],[2]	$ 33,847	[1]
Murphy USA Inc [Member]
Reconciliation of Changes in Asset Retirement Obligations [Line Items]
Accretion of asset retirement obligations		$ 980

[1] Reclassified to conform to current presentation.

[2] Includes $980 reclassified to discontinued operations associated with U.S. downstream operations.