Costs And Estimated Earnings On Uncompleted Contracts (Narrative) (Details) - customer	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Costs And Estimated Earnings On Uncompleted Contracts [Abstract]
Costs and estimated earnings in excess of billings on uncompleted contracts, net of billings in excess of costs and estimated earnings, percentage comprised by significant customers	87.90%	81.60%
Number of significant customers	8	8

Costs and estimated earnings in excess of billings on uncompleted contracts net percentage comprised by significant customers.

No definition available.

Name:	sbac_CostsAndEstimatedEarningsInExcessOfBillingsOnUncompletedContractsNetPercentageComprisedBySignificantCustomers
Namespace Prefix:	sbac_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant