Shareholders' Equity, Noncontrolling Interests and Other Comprehensive Income - Preferred OP Units (Details)	3 Months Ended	12 Months Ended		27 Months Ended	231 Months Ended
	Mar. 31, 2018 USD ($) $ / Units shares	Dec. 31, 2016 $ / shares shares	Dec. 31, 1999 shares	Mar. 31, 2018 USD ($) $ / Units shares	Mar. 31, 2018 USD ($) $ / Units shares	Dec. 31, 2017 shares
Class of Stock [Line Items]
Denominator for Series A Preferred OP Unit conversion | $	$ 7.50			$ 7.50	$ 7.50
Preferred OP Units
Class of Stock [Line Items]
Issuance of common shares, net of issuance costs (in Shares)	0
Series A Preferred Stock
Class of Stock [Line Items]
Issuance of common shares, net of issuance costs (in Shares)			1,580
Preferred stock, stated value per unit | $ / Units	1,000
Per unit conversion amount, Series A Preferred OP Units (in dollars per unit) | $ / Units	22.50			22.50	22.50
Per unit conversion annual rate, Preferred OP Units	9.00%			9.00%	9.00%
Number of preferred OP Units converted (in shares)					1,392
Units converted from Preferred OP Units (in shares)					185,600
Operating Partnership, as General Partner or Managing Member
Class of Stock [Line Items]
Preferred OP Units (in shares)	3,328,873			3,328,873	3,328,873	3,328,873
Operating Partnership, as General Partner or Managing Member | Series A Preferred Stock
Class of Stock [Line Items]
Preferred OP Units (in shares)	188			188	188	188
Operating Partnership, as General Partner or Managing Member | Series C Preferred Stock
Class of Stock [Line Items]
Preferred OP Units (in shares)	136,593			136,593	136,593	136,593
Gotham Plaza | Preferred OP Units
Class of Stock [Line Items]
Issuance of common shares, net of issuance costs (in Shares)		141,593
Gotham Plaza | Series C Preferred Stock
Class of Stock [Line Items]
Number of preferred OP Units converted (in shares)				5,000
Units converted from Preferred OP Units (in shares)				17,165
Gotham Plaza | Common Shares
Class of Stock [Line Items]
Issuance of common shares, net of issuance costs (in Shares)		442,478
Share price (in dollars per share) | $ / shares		$ 100.00
Preferred quarterly distribution per share price | $ / shares		$ 0.9375
Number of convertible units if share price falls below $28.80 (in shares)		3.4722
Number of convertible units of share price falls above $35.20 (in Shares)		2.8409
Minimum | Gotham Plaza | Preferred OP Units
Class of Stock [Line Items]
Share price at conversion date | $ / shares		$ 28.80
Maximum | Gotham Plaza | Preferred OP Units
Class of Stock [Line Items]
Share price at conversion date | $ / shares		$ 35.20