Incentive Plans (Changes in Time-Lapse Restricted Stock and Restricted Stock Units Outstanding) (Details) (Restricted Stock and Restricted Stock Units [Member])	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Restricted Stock and Restricted Stock Units [Member]
Schedule of Share based Compensation Arrangements by Share based Payment Award, Equity Instruments, Other Than Options, Restricted Stock Units [Line Items]
Balance at beginning of year	112,881	98,477	116,724
Granted restricted stock	278,892	38,184	42,256
Vested and issued	(54,884)	(34,696)	(44,980)
Forfeited	(15,100)		(15,523)
Murphy USA Inc. spin-off adjustment		10,916
Balance at end of year	321,789	112,881	98,477