Basis of Presentation and Significant Accounting Policies (Details 2) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Tax Treatment Of Dividend [Line Items]
Minimum Percentage of Taxable Income Distributed As Dividends									90.00%
Income Tax Expense Benefit Continuing Operations Income Tax Reconciliation [Line Items]
Deferred Tax Assets	$ 97,104				$ 94,100				$ 97,104	$ 94,100
Net income attributable to common shareholders	230,742	$ 198,870	$ 165,651	$ 84,593	$ 513,238	$ 131,159	$ 76,642	$ 62,349	679,856	783,388	$ 392,034
Tangible Property Regulations									(575,618)	0	0
Sale of real estate and other capital transactions									320,326	(477,061)	(324,936)
Depreciation and Amortization									227,297	219,403	155,401
Straight-line rent adjustments									(144,727)	(77,526)	(64,811)
Stock Options									(8,278)	(9,566)	4,884
Earnings of partially owned entities									(5,299)	71,960	339,376
Impairment losses on marketable equity securities									0	0	37,236
Other, net									(5,833)	1,260	36,186
Estimated Taxable Income (unaudited)									487,724	511,858	575,370
Deferred tax assets allowance, reversed			$ 90,030						90,030	0	0
Income Tax Liability Relating to Taxable REIT Subsidiaries Current									8,322	$ 10,777	$ 9,608
Net Basis Difference Of Assets And Liabilities Between Tax Basis And GAAP Basis	$ 3,400,000								$ 3,400,000
Ordinary Income [Member]
Tax Treatment Of Dividend [Line Items]
Percentage Of Taxable Income Distributed									100.00%