XML 64 R51.htm IDEA: XBRL DOCUMENT v3.10.0.1

Guarantor Subsidiaries (Additional Information) (Details) - Senior Notes	Sep. 30, 2018	Apr. 25, 2017	Aug. 14, 2013
6% Senior Notes Due 2023
Debt Instrument [Line Items]
Interest rate	6.00%		6.00%
5.625% Senior Notes Due 2027
Debt Instrument [Line Items]
Interest rate	5.625%	5.625%

X

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	us-gaap_DebtInstrumentAxis=musa_SeniorNotes6PercentDue2023Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SeniorNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DebtInstrumentAxis=musa_SeniorNotes5.625PercentDue2027Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: