CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (DEFICIT) AND COMPREHENSIVE INCOME (Parenthetical) (Common Stock, USD $)	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Common Stock
Common Stock, par	$ 0.01	$ 0.01	$ 0.01

Face amount or stated value per share; generally not indicative of the fair market value per share.

No definition available.

Name:	musa_ParOrStatedValuePerShare
Namespace Prefix:	musa_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant