Deferred Revenue - Additional Information (Detail) (Maximum [Member])	3 Months Ended
Mar. 31, 2013
Maximum [Member]
Deferred Revenue Arrangement [Line Items]
Recognition period for current portion of deferred revenue	12 months

Expected recognition period for deferred revenue current.

No definition available.

Name:	bsft_ExpectedRecognitionPeriodForDeferredRevenueCurrent
Namespace Prefix:	bsft_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration