Significant Accounting Policies - Investments in Unconsolidated Joint Ventures/Deferred Lease Costs/Revenue Recognition/Income Taxes (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Deferred Lease Costs [Abstract]
Portion of compensation capitalized	$ 5,400	$ 6,300	$ 15,700
Estimated average lease term (in years)	8 years
Additions to allowances charged against operations	$ 35,298	0	6,839
Write-offs charged against allowance	$ 37,033	4,000	1,089
Days past due for income recognition on debt and preferred equity investments to be suspended	90 days
Income taxes
Federal, state and local tax provision	$ 1,200	$ 1,500	$ 2,800
Dividends per share paid (in dollars per share)	$ 5.54	$ 3.40	$ 3.25
Tenant Receivables And Deferred Rent
Deferred Lease Costs [Abstract]
Additions to allowances charged against operations			$ 4,200
Tenant and other receivables, allowance			31,200
Write-offs charged against allowance			$ 8,900
Ordinary Income Dividend
Income taxes
Dividends per share paid (in dollars per share)	1.84	2.59	$ 1.46
Capital Gains Dividend
Income taxes
Dividends per share paid (in dollars per share)	$ 3.06	$ 0.81	$ 1.79