Costs And Estimated Earnings On Uncompleted Contracts (Narrative) (Detail)	6 Months Ended	12 Months Ended
Sep. 30, 2012	Dec. 31, 2011
Contracts In Progress Costs And Earnings [Line Items]
Costs and estimated earnings in excess of billings on uncompleted contracts, net of billings in excess of costs and estimated earnings, percentage	78.80%	91.40%
Number of significant customers	5	5

Costs And Estimated Earnings In Excess Of Billings On Uncompleted Contracts Net

No definition available.

Name:	sbac_CostsAndEstimatedEarningsInExcessOfBillingsOnUncompletedContractsNet
Namespace Prefix:	sbac_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration