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Subsequent Events (Narrative) (Details) - 10b5-1 Plan - Subsequent Event	1 Months Ended
	Aug. 04, 2017 USD ($) $ / shares
Subsequent Event [Line Items]
Purchase allocation (as a percent)	98.00%
Safety, Income and Growth, Inc.
Subsequent Event [Line Items]
Aggregate value of common stock purchased	$ 5,100,000
Amount authorized for purchase	$ 25,000,000.0
Purchase threshold, share price trigger (in dollars per share) | $ / shares	$ 20.00
Chief Executive Officer
Subsequent Event [Line Items]
Purchase allocation (as a percent)	1.00%
Chief Financial Officer
Subsequent Event [Line Items]
Purchase allocation (as a percent)	1.00%

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