Summary of Significant Accounting Policies (Details 3) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Income Taxes
State and local income, excise and franchise taxes	$ 0.1	$ 0.1	$ 0.3	$ 0.1
Liabilities for uncertain tax positions	$ 0		$ 0

Represents the current and noncurrent portion of the amount recognized for uncertain tax positions as of the balance sheet date.

No definition available.

Name:	stag_LiabilityForUncertainTaxPositionsCurrentAndNoncurrent
Namespace Prefix:	stag_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant