Commitments and Contingencies (Details) $ in Millions	Dec. 31, 2021 USD ($)
Unfunded commitments
Leasehold improvement allowance, unfunded, pending milestone achievement	$ 165.5
Future funding obligation, amount	$ 363.9

Real Estate, Leasehold Improvement Allowance, Unfunded, Pending Milestone Achievement

No definition available.

Name:	safe_RealEstateLeaseholdImprovementAllowanceUnfundedPendingMilestoneAchievement
Namespace Prefix:	safe_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant