Consolidated Statements of Cash Flows (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating activities
Net income (loss)	$ 44,208,000	$ (12,037,000)	$ (42,981,000)
Adjustments to reconcile net income (loss) to cash provided by operating activities:
Depreciation and amortization	182,955,000	118,031,000	74,626,000
Depreciation and amortization-discontinued operations	116,000	4,560,000	7,843,000
Net amortization of above (below) market leases	(13,690,000)	2,210,000	5,015,000
Net amortization of above (below) market leases-discontinued operations	0	33,000	84,000
Amortization of financing costs	2,845,000	2,448,000	1,967,000
Amortization of financing costs-discontinued operations	0	17,000	96,000
Amortization of debt premium, net	(6,374,000)	0	0
Non-cash adjustment for interest rate swaps	(19,000)	0	0
Share-based compensation expense	7,417,000	5,730,000	432,000
Deferred income tax benefit	(4,763,000)	(1,960,000)	(1,030,000)
Gain on sale of in-substance real estate	(6,289,000)	0	0
Gain on sale of real estate	(76,378,000)	0	(548,000)
Gain on sale of real estate-discontinued operations	(10,463,000)	(32,493,000)	(12,938,000)
Non-cash impairment loss on real estate	11,700,000	0	5,700,000
Non-cash impairment loss on real estate-discontinued operations	0	10,200,000	3,500,000
Non-cash impairment loss on management contracts and goodwill	4,750,000	0	41,967,000
Equity in (earnings) losses of unconsolidated joint ventures	967,000	(178,000)	0
Equity in losses of unconsolidated joint ventures-discontinued operations	0	0	19,000
Distributions of income from unconsolidated joint ventures	5,338,000	0	0
Change in fair value of contingent consideration	0	0	216,000
Increase in deferred leasing costs	(16,742,000)	(16,117,000)	(11,885,000)
Changes in operating assets and liabilities:
Change in condominium units	10,582,000	0	0
Change in receivables and other assets	(65,846,000)	(25,739,000)	(1,854,000)
Change in accounts payable and other liabilities	(17,310,000)	10,381,000	(8,656,000)
Cash provided by operating activities	53,004,000	65,086,000	61,573,000
Investing activities
Issuance of mortgage loan receivable	0	(3,523,000)	0
Proceeds from mortgage loan receivable	85,000	21,000	2,000,000
Distributions of capital from unconsolidated joint ventures	251,000	29,405,000	120,000
Investment in unconsolidated joint ventures	(3,505,000)	(86,685,000)	0
Investment in real estate	(750,004,000)	(187,442,000)	(692,911,000)
Acquisition of TPGI, net of cash received	0	(54,031,000)	0
Proceeds from sale of in-substance real estate	24,923,000	0	0
Proceeds from sale of real estate	382,912,000	191,485,000	127,867,000
Real estate development	(14,282,000)	(745,000)	0
Improvements to real estate	(52,569,000)	(35,373,000)	(25,621,000)
Cash used in investing activities	(412,189,000)	(146,888,000)	(588,545,000)
Financing activities
Principal payments on mortgage notes payable	(53,402,000)	(73,385,000)	(24,623,000)
Proceeds from mortgage notes payable	481,000	178,000,000	73,500,000
Proceeds from bank borrowings	398,590,000	542,234,000	482,266,000
Payments on bank borrowings	(220,090,000)	(501,234,000)	(352,588,000)
Debt financing costs	(3,893,000)	(2,749,000)	(3,552,000)
Purchase of Company stock	0	(49,000)	(172,000)
Dividends paid on common stock	(76,734,000)	(41,818,000)	(14,591,000)
Distributions to noncontrolling interest partners	(3,848,000)	0	0
Dividends paid on convertible preferred stock	0	0	(1,011,000)
Dividends paid on preferred stock	0	(3,433,000)	(13,553,000)
Acquisition of noncontrolling interests	(43,502,000)	0	0
Contributions from noncontrolling interest partners	4,175,000	0	17,447,000
Distributions to noncontrolling interest partners	(2,713,000)	(113,178,000)	(729,000)
Redemption of preferred stock	0	(135,532,000)	0
Proceeds from stock offerings, net of offering costs	417,684,000	209,768,000	371,251,000
Cash provided by financing activities	416,748,000	58,624,000	533,645,000
Change in cash and cash equivalents	57,563,000	(23,178,000)	6,673,000
Cash and cash equivalents at beginning of year	58,678,000	81,856,000	75,183,000
Cash and cash equivalents at end of year	116,241,000	58,678,000	81,856,000
Supplemental cash flow information:
Interest paid, net of amount capitalized	71,339,000	43,334,000	36,378,000
Cash paid for income taxes	4,792,000	56,000	1,275,000
Supplemental schedule of non-cash investing and financing activity:
Assets acquired in TPGI merger	0	1,202,732,000	0
Liabilities assumed in TPGI merger	0	122,282,000	0
Noncontrolling interests acquired in TPGI merger	0	34,230,000	0
Shares issued in TPGI merger	0	331,260,000	0
Issuance of limited voting stock in TPGI merger	0	4,000	0
Acquisition of Lincoln Place	0	68,430,000	0
Issuance of operating partnership units	1,546,000	96,409,000	18,216,000
Transfer of assets classified as held for sale	24,079,000	16,260,000	0
Mortgage notes payable transferred to purchaser	0	0	254,095,000
Restricted shares and deferred incentive share units issued (forfeited)	0	0	1,105,000
Mortgage loans assumed in purchases	301,251,000	727,451,000	58,694,000
Operating partnership units converted to common stock	0	4,302,000	18,216,000
San Jacinto Center and One Congress Plaza
Supplemental schedule of non-cash investing and financing activity:
Acquisitions	311,400,000	0	0
One Orlando Centre
Supplemental schedule of non-cash investing and financing activity:
Acquisitions	$ 54,000,000	$ 0	$ 0