Consolidated Statement of Changes in Equity (Unaudited) (USD $) In Thousands, unless otherwise specified	Total	Common Stock	Limited Voting Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit	Noncontrolling Interests
Balance at Dec. 31, 2013	$ 1,335,521	$ 87	$ 4	$ 1,428,026	$ (2,179)	$ (409,338)	$ 318,921
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	503					1,000	(497)
Change in fair value of interest rate swaps	(4,151)				(4,225)	0	74
Common dividends declared-$0.375 per share	(39,449)					(37,498)	(1,951)
Share-based compensation	4,735			4,735
Issuance of 16,481 shares to Directors	309			309
Issuance of 11,996,800 shares of common stock, net of offering costs	208,429	12		208,417
Issuance of 12,878 shares pursuant to TPG Management Services Agreement	250			250
Issuance of 85,649 operating partnership units	1,546						1,546
Exercise of Madison International Realty's put option related to merger with Thomas Properties Group, Inc.	(41,539)			(10,522)			(31,017)
Contribution of capital by noncontrolling interests	459						459
Purchase of noncontrolling interest's share of office and parking properties owned by Parkway Properties Office Fund II, L.P.	(1,963)						(1,963)
Balance at Jun. 30, 2014	$ 1,464,650	$ 99	$ 4	$ 1,631,215	$ (6,404)	$ (445,836)	$ 285,572