Noncontrolling Interests - Narrative (Details) $ in Millions		12 Months Ended
	May. 14, 2008 USD ($) property	Dec. 31, 2015 joint_venture term_extension shares	Apr. 30, 2014	Apr. 14, 2014	Aug. 31, 2012 USD ($) parking_space
Noncontrolling Interest [Abstract]
Number of joint ventures | joint_venture		2
Real Estate Properties [Line Items]
Ownership percentage		95.90%
Thomas Properties Group, Inc.
Real Estate Properties [Line Items]
Number of common units outstanding in a business acquisition | shares		4,300,000
Florida | Office Building | Lincoln Place
Real Estate Properties [Line Items]
Number of common units issued in a business acquisition | shares		554,400
Total Fund II
Real Estate Properties [Line Items]
Target value of discretionary fund	$ 750.0
Target capital structure of equity capital	375.0
Target capital structure of non-recourse, fixed rate first mortgage debt	$ 375.0
Number of properties acquired | property	13
Increased discretionary fund capacity					$ 20.0
Number of parking spaces in garage acquired | parking_space					2,500
Cumulative preferred return threshold for pro rata cash distributions (as a percent)		9.00%
Term of the fund		7 years
Number of term extension provisions | term_extension		2
Length of extension term		1 year
Total Fund II | Parkway
Real Estate Properties [Line Items]
Target ownership percentage (as a percent)	30.00%
Distribution percentage to partners (as a percent)		44.00%
Total Fund II | TRST
Real Estate Properties [Line Items]
Target ownership percentage (as a percent)	70.00%
Distribution percentage to partners (as a percent)		56.00%
Hayden Ferry Lakeside III
Real Estate Properties [Line Items]
Ownership percentage			70.00%	70.00%