CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 64,308	$ 134,592	$ 149,970
Adjustments to reconcile net income to net cash provided by operating activities:
Gain on disposition of properties	(48,886)	(81,965)	(89,063)
Gain on change in control	(5,571)	0	0
Depreciation and amortization	104,934	70,011	60,751
Distributions of operating income from unconsolidated affiliates	9,249	7,256	12,291
Equity in earnings and gains of unconsolidated affiliates	(23,371)	(39,449)	(37,330)
Stock compensation expense	11,155	13,695	7,438
Amortization of financing costs	5,985	3,204	3,537
Impairment charges	14,455	0	5,000
Other, net	(10,610)	(8,095)	(6,483)
Changes in assets and liabilities:
Other liabilities	(4,285)	26,532	5,354
Prepaid expenses and other assets	(6,498)	(11,677)	12,690
Rents receivable, net	(11,274)	(4,847)	(5,673)
Restricted cash	11,474	1,912	(6,168)
Accounts payable and accrued expenses	8,768	591	1,284
Net cash provided by operating activities	119,833	111,760	113,598
CASH FLOWS FROM INVESTING ACTIVITIES
Acquisition of real estate	(200,429)	(495,644)	(338,700)
Development and property improvement costs	(108,142)	(149,434)	(164,315)
Issuance of or advances on notes receivable	(10,600)	(157,352)	(48,500)
Proceeds from the disposition of properties	260,711	150,378	168,895
Investments in and advances to unconsolidated affiliates	(6,535)	(72,098)	(24,168)
Return of capital from unconsolidated affiliates	23,946	54,444	11,892
Proceeds from notes receivable	32,000	42,819	15,984
Deposits for properties under contract	(2,000)	1,424	(5,776)
Proceeds from disposition of properties of unconsolidated affiliates	26,045	24,586	38,392
Payment of deferred leasing costs	(5,202)	(7,515)	(8,207)
Change in control of previously unconsolidated (consolidated) affiliate	288	(2,578)	0
Net cash provided by (used in) investing activities	10,082	(610,970)	(354,503)
CASH FLOWS FROM FINANCING ACTIVITIES
Principal payments on mortgage and other notes	(306,119)	(394,864)	(148,423)
Principal payments on unsecured debt	(277,134)	(541,790)	(234,815)
Proceeds received on mortgage and other notes	156,344	222,071	90,234
Proceeds from unsecured debt	359,625	666,716	417,425
Proceeds from issuance of Common Shares, net of issuance costs of $0, $9,238 and $1,150, respectively	0	450,130	63,234
Capital contributions from noncontrolling interests	85,206	295,108	35,489
Distributions to noncontrolling interests	(39,942)	(105,994)	(84,610)
Dividends paid to Common Shareholders	(99,527)	(91,334)	(86,353)
Deferred financing and other costs	(6,211)	(11,678)	(4,376)
Loan proceeds held as restricted cash	861	9,874	48,676
Purchase of convertible notes payable	0	0	(380)
Net cash (used in) provided by financing activities	(126,897)	498,239	96,101
Increase (decrease) in cash and cash equivalents	3,018	(971)	(144,804)
Cash and cash equivalents, beginning of the year	71,805	72,776	217,580
Cash and cash equivalents, end of the year	74,823	71,805	72,776
Supplemental disclosure of cash flow information
Cash paid during the period for interest, net of capitalized interest of $13,509, $21,109 and $16,447, respectively	49,942	42,279	47,960
Cash paid for income taxes, net of (refunds)	875	2,036	2,038
Supplemental disclosure of non-cash investing activities
Acquisition of real estate through assumption of debt	0	120,672	91,885
Acquisition of real estate through issuance of OP Units	0	29,336	0
Acquisition of capital lease obligation	0	76,461	0
Mortgage debt financed at time of acquisition	0	63,900	0
Assumption of accounts payable and accrued expenses through acquisition of real estate	2,173	3,587	0
Assumption of prepaid expenses and other assets through acquisition of real estate		2,226	0
Disposition of air rights through issuance of notes receivable	0		(29,539)
Acquisition of real estate through assumption of restricted cash	0		(28,912)
Acquisition of real estate through conversion of note receivable	9,000	0	13,386
Acquisition of undivided interest in a property through conversion of notes receivable	60,695	0	0
Change in control of previously unconsolidated (consolidated) investment
(Increase) decrease in real estate, net	(39,322)	90,559	0
Gain on change in control	5,571	0	0
Decrease in notes receivable	32,010	0	0
Decrease (increase) in investments in and advances to unconsolidated affiliates	4,159	(21,421)	0
Decrease in noncontrolling interest	0	(75,713)	0
Change in other assets and liabilities	(2,130)	3,997	0
Increase (decrease) in cash upon change of control	$ 288	$ (2,578)	$ 0