Real estate (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended							1 Months Ended	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2012	Jun. 30, 2013 Net Lease Assets property	Jun. 30, 2012 Net Lease Assets property	Jun. 30, 2013 Commercial Operating Properties property	Jun. 30, 2012 Commercial Operating Properties property	Jun. 30, 2013 Land	Jun. 30, 2012 Land	Apr. 30, 2012 Portfolio Lease Asset Sale Net Lease Assets property	Jun. 30, 2013 Real estate equity investments Land
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Property sold, aggregate, carrying value					$ 43.2	$ 10.3	$ 5.5	$ 2.7		$ 21.4
Gain (Loss) on disposition of property, sale carve out					9.9					3.4
iStar's ownership percentage, equity method										47.50%
Number of real estate properties sold			3	2	3	5			12
Net lease assets sold, carrying value			13.5	9.8					105.7
Gain (loss) on sale of leased assets, net, operating leases, sale carve out			3.4	2.4					24.9
Impairment of long-lived assets sale carve out	$ 1.3	$ 16.6				$ (1.4)