Reportable Segments 2 Parentheticals (Details) (USD $) In Millions, unless otherwise specified	0 Months Ended	3 Months Ended
Mar. 31, 2012	Mar. 25, 2012	Mar. 31, 2011
Capital Expenditures [Abstract]
Net reduction in capital accruals	$ 0.3	$ 13.7	$ 15.6

The increase or decrease in capital accrued for plant, property, and equipment.

No definition available.

Name:	sug_IncreaseDecreaseCapitalAccruals
Namespace Prefix:	sug_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration