Commitments and Contingencies - Summary of Aggregate Non-Cancelable Future Minimum Rental Payments Under Operating Leases (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013
Commitments And Contingencies Disclosure [Abstract]
2014	$ 332
2015	114
Total rental payments	$ 446

Operating leases future minimum payments including effect of lease extension executed due current.

No definition available.

Name:	snss_OperatingLeasesFutureMinimumPaymentsIncludingEffectOfLeaseExtensionExecutedDueCurrent
Namespace Prefix:	snss_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant