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Land and Development (Acquisitions, Dispositions, Impairments) (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) land_asset	Dec. 31, 2018 USD ($) a parcel land_asset	Dec. 31, 2017 USD ($) a land_asset
Real Estate Properties [Line Items]
Increase in net lease assets upon consolidation of equity method investment									$ 0	$ 844,550	$ 0
Revenue	$ 128,888	$ 145,338	$ 98,468	$ 106,802	$ 140,165	$ 122,141	$ 171,571	$ 364,245	479,496	$ 798,122	$ 679,202
Number of land parcels sold \| parcel										2
Area of land parcels sold (in acres) \| a										93
Impairment of land and development assets, expected sales proceeds									$ 5,300
Number of land and development assets impaired \| land_asset									2	5	1
Impairment of land and development assets, change in business strategy									$ 1,100
Impairment of land and development assets										$ 56,700	$ 20,500
Other Real Estate Equity Investment Dec 2016
Real Estate Properties [Line Items]
iStar's ownership percentage	50.00%								50.00%
Prince George's County, Maryland
Real Estate Properties [Line Items]
Land subject to litigation (in acres) \| a											1,250
Land
Real Estate Properties [Line Items]
Aggregate financing provided to buyers										145,000
Proceeds of notes receivable	$ 94,200								$ 94,200
Land development
Real Estate Properties [Line Items]
Revenue									119,595	409,710	$ 196,879
Cost of sales expense									109,663	350,181	180,916
Land development \| Prince George's County, Maryland
Real Estate Properties [Line Items]
Revenue											114,000
Cost of sales expense											$ 106,300
Land \| Real Estate Acquired in Satisfaction of Debt
Real Estate Properties [Line Items]
Increase in net lease assets upon consolidation of equity method investment										$ 4,600
Affiliated Entity
Real Estate Properties [Line Items]
Real estate transaction price									34,300
Payments to acquire land and develop asset									7,300
Assumption of loan in acquisition transaction									$ 27,000