Our History and Summary of Various Transactions (Details) (Voting common stock) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Apr. 27, 2012
Voting common stock
Going private and merger immediately thereafter
Number of SGS shares contributed by Parent to MergerSub, as a percentage of all outstanding SGS shares		73,094
SGS shares contributed by Parent to MergerSub, as a percentage of all outstanding SGS shares (as a percent)		96.20%
Voting ownership percentage in each entity held by Sponsors, minimum	50.00%

The outstanding shares in the entity, expressed as a percentage of all outstanding shares in the entity, that were contributed by the parent of the entity for the purpose of going private.

No definition available.

Name:	sgs_GoingPrivateTransactionPercentageOfOutstandingSharesInEntityContributedByParentOfEntity
Namespace Prefix:	sgs_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant