Earnings Per Share (Earnings Allocable to Common Shares) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Denominator for basic and diluted earnings per share:
Weighted average common shares outstanding for basic and diluted earnings per common share (in shares)		73,984	85,541	75,522	85,519
Weighted average common shares outstanding for diluted earnings per common share (in shares)		118,510	85,541	104,431	85,519
Basic earnings per common share:
Income (loss) from continuing operations attributable to iStar Inc. and allocable to common shareholders (in dollars per share)		$ 0.52	$ (0.36)	$ 0.22	$ (0.63)
Diluted earnings per common share:
Income (loss) from continuing operations attributable to iStar Inc. and allocable to common shareholders (in dollars per share)		0.37	(0.36)	0.22	(0.63)
Net income (loss) attributable to iStar Inc. and allocable to common shareholders (in dollars per share)		$ 0.37	$ (0.36)	$ 0.22	$ (0.63)
Denominator for basic and diluted earnings per HPU share:
Weighted average High Performance Units outstanding for basic and diluted earnings per share (in shares)	[1]	0	15	0	15
Basic and diluted earnings per HPU share:
Net income (loss) attributable to iStar Inc. and allocable to HPU holders	[1]	$ 0.00	$ (68.47)	$ 0.00	$ (118.40)
Undistributed earnings (loss) allocated to participating securities, basic		$ 20
Undistributed earnings (loss) allocated to participating securities, diluted		$ 14		$ 11
Common Stock
Denominator for basic and diluted earnings per share:
Weighted average common shares outstanding for basic and diluted earnings per common share (in shares)		73,984	85,541	75,522	85,519
Add: Effect of assumed shares issued under treasury stock method for restricted shares (in shares)		34	0	52	0
Weighted average common shares outstanding for diluted earnings per common share (in shares)		118,510	85,541	104,431	85,519
Basic earnings per common share:
Income (loss) from continuing operations attributable to iStar Inc. and allocable to common shareholders (in dollars per share)		$ 0.52	$ (0.36)	$ 0.22	$ (0.63)
Net income (loss) attributable to iStar Inc. and allocable to common shareholders (in dollars per share)		0.52	(0.36)	0.22	(0.63)
Diluted earnings per common share:
Income (loss) from continuing operations attributable to iStar Inc. and allocable to common shareholders (in dollars per share)		0.37	(0.36)	0.22	(0.63)
Net income (loss) attributable to iStar Inc. and allocable to common shareholders (in dollars per share)		$ 0.37	$ (0.36)	$ 0.22	$ (0.63)
HPU's
Numerator for basic and diluted earnings per HPU share:
Net income (loss) attributable to iStar Inc. and allocable to HPU holders		$ 0
Denominator for basic and diluted earnings per HPU share:
Weighted average High Performance Units outstanding for basic and diluted earnings per share (in shares)		0	15	0	15
Basic and diluted earnings per HPU share:
Net income (loss) attributable to iStar Inc. and allocable to HPU holders		$ 0.00	$ (68.47)	$ 0.00	$ (118.40)
Basic | Common Stock
Numerator for basic earnings per share:
Income (loss) from continuing operations attributable to iStar Inc. and allocable to common shareholders		$ 38,112	$ (30,950)	$ 16,933	$ (53,502)
Net income (loss) attributable to iStar Inc. and allocable to common shareholders		38,112	(30,950)	16,933	(53,502)
Basic | HPU's
Numerator for basic and diluted earnings per HPU share:
Net income (loss) attributable to iStar Inc. and allocable to HPU holders				0
Basic and Diluted [Member] | HPU's
Numerator for basic and diluted earnings per HPU share:
Net income (loss) attributable to iStar Inc. and allocable to HPU holders			(1,027)		(1,776)
Diluted | Common Stock
Numerator for basic earnings per share:
Income (loss) from continuing operations attributable to iStar Inc. and allocable to common shareholders		43,293	(30,950)	22,774	(53,502)
Net income (loss) attributable to iStar Inc. and allocable to common shareholders		$ 43,293	$ (30,950)	$ 22,774	$ (53,502)
Joint venture shares | Common Stock
Denominator for basic and diluted earnings per share:
Add: Effect of joint venture shares (in shares)		298	0	298	0
1.50% convertible senior unsecured notes
Basic and diluted earnings per HPU share:
Stated interest rates		1.50%	1.50%	1.50%	1.50%
1.50% convertible senior unsecured notes | Common Stock
Denominator for basic and diluted earnings per share:
Add: Effect of senior unsecured notes (in shares)		11,567	0	11,567	0
3.00% convertible senior unsecured notes
Basic and diluted earnings per HPU share:
Stated interest rates		3.00%	3.00%	3.00%	3.00%
3.00% convertible senior unsecured notes | Common Stock
Denominator for basic and diluted earnings per share:
Add: Effect of senior unsecured notes (in shares)		16,992	0	16,992	0
Preferred Stock Series J | Common Stock
Denominator for basic and diluted earnings per share:
Add: Effect of series J convertible perpetual preferred stock (in shares)		15,635	0	0	0

[1] All of the Company's outstanding High Performance Units ("HPUs") were repurchased and retired on August 13, 2015 (refer to Note 15)