Goodwill (Key Ratios Used to Measure Goodwill of Property and Casualty Insurance Reporting Unit for Impairment) (Detail) (Property And Casualty Insurance Reporting Unit [Member], Annual [Member])	May 31, 2014	May 31, 2013
Property And Casualty Insurance Reporting Unit [Member] \| Annual [Member]
Goodwill [Line Items]
Average price to book	1.34	1.15
Median price to earnings	21.1	18.1

Median price to earnings market multiple used, in part, to determine the fair value of the property and casualty insurance reporting unit.

No definition available.

Name:	susq_MedianPriceToEarningsRatioUsedToDetermineFairValueOfPropertyAndCasualtyInsuranceReportingUnit
Namespace Prefix:	susq_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant