Summary of Significant Accounting Policies Receivables, Trade and Other Accounts Receivalbe, Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Document Fiscal Year Focus	2018
Provision for Doubtful Accounts	$ 10,100	$ 8,040
Straight Line Rent	105,677	93,284
Tenant Reimbursements (Deprecated 2018-01-31)	25,305	14,825
Billed Tenant Receivables [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts and Notes Receivable, Net	25,590	25,329
Other Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts and Notes Receivable, Net	30,953	34,472
Notes Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts and Notes Receivable, Net	0	15,803
straight line rent [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for Doubtful Accounts	5,066	4,688
Parent Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Land	4,205,445	4,235,032
Property Management Fee Revenue	28,494	26,158	$ 25,327
Accounts and Notes Receivable, Net	172,359	170,985
Land Improvements	613,847	556,140
Buildings	5,088,102	4,999,378
Building improvements	901,596	787,880
Development in Process	54,172	314,391
Real Estate Investment Property, at Cost	10,863,162	10,892,821
Asset management services [Member] | Parent Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Property Management Fee Revenue	7,213	7,090	6,746
Leasing services [Member] | Parent Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Property Management Fee Revenue	4,044	3,573	4,285
Other transaction fees [Member] | Parent Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Property Management Fee Revenue	2,574	1,578	1,221
Property management services [Member] | Parent Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Property Management Fee Revenue	$ 14,663	$ 13,917	$ 13,075