Condensed Consolidated Balance Sheets - USD ($) $ in Thousands		Sep. 30, 2017	Dec. 31, 2016
Assets
Land		$ 1,016,097	$ 967,375
Buildings and improvements		6,269,561	5,967,023
Real estate assets, at cost, total		7,285,658	6,934,398
Accumulated depreciation		(2,080,989)	(1,890,656)
Net operating real estate assets		5,204,669	5,043,742
Properties under development, including land		363,481	442,292
Investments in joint ventures		28,420	30,254
Total real estate assets		5,596,570	5,516,288
Accounts receivable – affiliates		23,620	24,028
Other assets, net		189,253	142,010
Short-term Investments		0	100,000
Cash and cash equivalents		350,274	237,364
Restricted cash		9,178	8,462
Total assets		6,168,895	6,028,152
Liabilities
Unsecured notes payable		1,338,117	1,583,236
Secured notes payable	[1]	866,134	897,352
Accounts payable and accrued expenses		127,557	137,813
Accrued real estate taxes		70,027	49,041
Distributions payable		72,962	69,161
Other liabilities		154,506	118,959
Total liabilities		2,629,303	2,855,562
Commitments and contingencies (Note 10)
Non-qualified deferred compensation share awards		73,015	77,037
Equity
Common shares of beneficial interest; $0.01 par value per share; 175,000 shares authorized; 105,491 and 100,694 issued; 102,767 and 97,818 outstanding at September 30, 2017 and December 31, 2016, respectively		1,028	978
Additional paid-in capital		4,134,206	3,678,277
Distributions in excess of net income attributable to common shareholders		(383,584)	(289,180)
Treasury shares, at cost (10,092 and 10,330 common shares at September 30, 2017 and December 31, 2016, respectively)		(364,736)	(373,339)
Accumulated other comprehensive loss		(7)	(1,863)
Total common equity		3,386,907	3,014,873
Non-controlling interests		79,670	80,680
Total equity		3,466,577	3,095,553
Total liabilities and equity		$ 6,168,895	$ 6,028,152

[1] Unamortized debt discounts and debt issuance costs of $13.0 million and $15.7 million are included in senior unsecured and secured notes payable as of September 30, 2017 and December 31, 2016, respectively.