Stock-Based Compensation 7 (Details) (USD $)	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Share-based Compensation Arrangement by Share-based Payment Award [Abstract]
Outstanding	460,857	447,130	563,650	548,639
Granted	270,835	175,043	268,027
Vested	(239,714)	(237,219)	(204,937)
Forfeited	(17,394)	(54,344)	(48,079)
Weighted-average exercise price - Outstanding	$ 34.29	$ 20.56	$ 18.38	$ 17.31
Weighted-average exercise price - Granted	$ 42.01	$ 24.67	$ 21.06
Weighted-average exercise price - Vested	$ 18.53	$ 18.82	$ 19.38
Weighted-average exercise price - Forfeited	$ 18.86	$ 18.77	$ 16.87

The weighted average grant date fair value of restricted stock units vested during the period.

No definition available.

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Data Type:	num:perShareItemType
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Period Type:	duration

The number of restricted stock units forfeited during the period.

No definition available.

Name:	sug_RestrictedStockUnitsForfeited
Namespace Prefix:	sug_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

The weighted average grant date fair value of restricted stock units forfeited during the period.

No definition available.

Name:	sug_RestrictedStockUnitsForfeitedWeightedAverageGrantDateFairValue
Namespace Prefix:	sug_
Data Type:	num:perShareItemType
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Period Type:	duration

The number of restricted stock units granted during the period.

No definition available.

Name:	sug_RestrictedStockUnitsGranted
Namespace Prefix:	sug_
Data Type:	xbrli:sharesItemType
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Period Type:	duration

The weighted average grant date fair value of restricted stock granted during the period.

No definition available.

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Namespace Prefix:	sug_
Data Type:	num:perShareItemType
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Period Type:	duration

The number of resticted stock units outstanding.

No definition available.

Name:	sug_RestrictedStockUnitsOustanding
Namespace Prefix:	sug_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

The weighted average grant date fair value of restricted stock units outstanding.

No definition available.

Name:	sug_RestrictedStockUnitsOutstandingWeightedAverageGrantDateFairValue
Namespace Prefix:	sug_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

The number of restricted stock units vested during the period.

No definition available.

Name:	sug_RestrictedStockUnitsVested
Namespace Prefix:	sug_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

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