Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating Activities
Net income	$ 146,114	$ 106,778	$ 140,249
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	261,289	224,096	190,778
Loss on early extinguishment of debt	189	525	1,992
(Gain) loss on sale of real estate	(12,426)	(1,838)	121
Impairment of real estate	23,250	51,675	0
Gain on sales of real estate - land parcels	0	(6,403)	(4,824)
Equity in earnings of unconsolidated joint ventures	(1,651)	(554)	0
Distributions of earnings from unconsolidated joint ventures	873	549	0
Amortization of loan fees and costs	11,003	10,909	9,936
Amortization of debt premiums/discounts	(372)	117	529
Amortization of acquired above and below market leases	(6,118)	(2,845)	(3,316)
Deferred rent	(47,483)	(44,726)	(27,935)
Stock compensation expense	17,512	13,996	15,552
Investment gains	(35,035)	(11,613)	(7,050)
Investment losses	16,093	9,287	1,480
Changes in operating assets and liabilities:
Restricted cash	60	4,141	899
Tenant receivables	7	(673)	(1,519)
Deferred leasing costs	(65,415)	(38,282)	(54,825)
Other assets	(9,079)	(7,466)	(6,298)
Accounts payable, accrued expenses, and tenant security deposits	43,800	26,652	56,958
Net cash provided by operating activities	342,611	334,325	312,727
Investing Activities
Proceeds from sales of real estate	129,799	81,580	153,968
Additions to real estate	(564,206)	(497,773)	(593,389)
Purchase of real estate	(248,933)	(127,887)	(122,069)
Deposits for investing activities	(5,501)	(10,282)	0
Change in restricted cash related to construction projects	0	1,665	7,655
Investment in unconsolidated joint venture	(9,027)	(70,758)	(17,987)
Additions to investments	(95,945)	(60,230)	(36,078)
Proceeds from sales of investments	67,136	18,973	16,525
Proceeds from repayment of notes receivable	4,282	29,883	0
Net cash used in investing activities	(722,395)	(634,829)	(591,375)
Financing Activities
Borrowings from secured notes payable	169,754	126,215	28,489
Repayments of borrowings from secured notes payable	(89,815)	(231,051)	(36,219)
Proceeds from issuance of unsecured senior notes payable	298,872	698,908	498,561
Principal borrowings from unsecured senior line of credit and unsecured senior bank term loans	2,145,000	1,168,000	729,000
Repayments of borrowings from unsecured senior line of credit	(2,298,000)	(1,068,000)	(1,091,000)
Repayment of unsecured senior bank term loan	(25,000)	(125,000)	(250,000)
Repurchase of unsecured senior convertible notes	0	0	(384)
Redemption of Series D Cumulative Convertible Preferred Stock	0	(14,414)	0
Change in restricted cash related to financings	3,842	(1,409)	2,546
Loan fees and costs paid	(10,584)	(8,099)	(19,928)
Proceeds from common stock offerings	78,463	0	534,469
Dividends paid on common stock	(218,104)	(202,386)	(169,076)
Dividends paid on preferred stock	(24,986)	(25,885)	(25,885)
Contributions by noncontrolling interests	453,750	19,410	0
Distributions to noncontrolling interests	(64,066)	(4,977)	(3,003)
Net cash provided by financing activities	419,126	331,312	197,570
Effect of foreign exchange rate changes on cash and cash equivalents	(255)	(2,493)	(2,197)
Net (decrease) increase in cash and cash equivalents	39,087	28,315	(83,275)
Cash and cash equivalents at beginning of period	86,011	57,696	140,971
Cash and cash equivalents at end of period	125,098	86,011	57,696
Supplemental Disclosure of Cash Flow Information
Cash paid during the period for interest, net of interest capitalized	93,856	57,966	59,857
Non-Cash Investing Activities
Note receivable issued in connection with sale of real estate		2,000	38,820
Change in accrued capital expenditures	(10,070)	29,846	(21,310)
Assumption of secured notes payable in connection with purchase of properties	(82,000)	(48,329)	0
Payments to Acquire Additional Interest in Subsidiaries	$ (51,092)	$ 0	$ 0