Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Operating Activities
Net income	$ 140,249	$ 105,528	$ 135,393
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	190,778	192,005	158,026
Impairment of land parcel	0	2,050	0
Loss on early extinguishment of debt	1,992	2,225	6,485
Loss (gain) on sale of real estate	121	(1,564)	0
Impairment of real estate	0	11,400	994
Gain on sale of land parcels	(4,824)	(1,864)	(46)
Amortization of loan fees and costs	9,936	9,832	9,300
Amortization of debt premiums/discounts	529	511	3,819
Amortization of acquired above and below market leases	(3,316)	(3,200)	(9,332)
Deferred rent	(27,935)	(28,456)	(26,797)
Stock compensation expense	15,552	14,160	11,755
Investment gains	(7,050)	(15,018)	(4,846)
Investment losses	1,480	2,637	1,795
Changes in operating assets and liabilities:
Restricted cash	899	(261)	(465)
Tenant receivables	(1,519)	(981)	(2,359)
Deferred leasing costs	(54,825)	(45,099)	(56,226)
Other assets	(6,298)	(4,069)	(22,359)
Accounts payable, accrued expenses, and tenant security deposits	56,958	65,697	41,823
Net cash provided by operating activities	312,727	305,533	246,960
Investing Activities
Proceeds from sale of properties	153,968	36,179	20,078
Additions to properties	(593,389)	(549,030)	(430,038)
Purchase of properties	(122,069)	(42,171)	(305,030)
Change in restricted cash related to construction projects	7,655	(9,377)	(2,183)
Distribution from unconsolidated real estate entity	0	22,250	0
Contributions to unconsolidated real estate entity	(17,987)	(6,700)	(5,256)
Additions to investments	(36,078)	(36,294)	(27,999)
Proceeds from investments	16,525	27,043	16,849
Net cash used in investing activities	(591,375)	(558,100)	(733,579)
Financing Activities
Borrowings from secured notes payable	28,489	17,810	0
Repayments of borrowings from secured notes payable	(36,219)	(26,367)	(66,849)
Proceeds from issuance of unsecured senior notes payable	498,561	544,650	0
Principal borrowings from unsecured senior line of credit and unsecured senior bank term loans	729,000	847,147	1,406,000
Repayments of borrowings from unsecured senior line of credit	(1,091,000)	(651,147)	(1,784,000)
Principal borrowings from unsecured senior bank term loans	0	0	1,350,000
Repayment of unsecured senior bank term loan	(250,000)	(250,000)	(500,000)
Repurchase of unsecured senior convertible notes	(384)	(84,801)	(221,439)
Redemption of Series C Cumulative Redeemable Preferred Stock	0	(129,638)	0
Proceeds from issuance of Series E Cumulative Redeemable Preferred Stock	0	124,868	0
Change in restricted cash related to financings	2,546	(7,428)	7,311
Deferred financing costs paid	(19,928)	(13,225)	(27,316)
Proceeds from common stock offering	534,469	97,890	451,539
Proceeds from exercise of stock options	0	155	2,117
Dividends paid on common stock	(169,076)	(126,498)	(106,889)
Dividends paid on preferred stock	(25,885)	(27,819)	(28,357)
Contributions by redeemable noncontrolling interests	0	0	9
Distributions to redeemable noncontrolling interests	(1,191)	(1,249)	(1,263)
Redemption of redeemable noncontrolling interests	0	(450)	0
Contributions by noncontrolling interests	0	1,875	1,000
Distributions to noncontrolling interests	(1,812)	(913)	(2,707)
Net cash provided by financing activities	197,570	314,860	479,156
Effect of foreign exchange rate changes on cash and cash equivalents	(2,197)	139	(5,230)
Net (decrease) increase in cash and cash equivalents	(83,275)	62,432	(12,693)
Cash and cash equivalents at beginning of period	140,971	78,539	91,232
Cash and cash equivalents at end of period	57,696	140,971	78,539
Supplemental Disclosure of Cash Flow Information
Cash paid during the period for interest, net of interest capitalized	59,857	52,561	52,324
Non-Cash Investing Activities
Note receivable from sale of real estate	38,820	6,125	0
Write-off of fully amortized improvements	0	(17,730)	0
Change in accrued capital expenditures	$ (21,310)	$ 46,087	$ 3,492