Fair Value Disclosures (Estimated Fair Value of Notes Payable) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Real Estate Properties [Line Items]
Notes Payable, Net	$ 3,640,128	$ 3,555,228
Consolidated Properties [Member]
Real Estate Properties [Line Items]
Notes Payable, Net	3,640,128	3,555,228
Fair Value, Inputs, Level 2 [Member] | Consolidated Properties [Member]
Real Estate Properties [Line Items]
Notes Payable, Fair Value Disclosure	$ 3,550,968	$ 3,503,071
Notes Payable Fair Values Hypothetical Percent Increase In Interest Rates	1.00%
Impact Of Overall One Percent Increase In Interest Rates Decrease In Fair Values Of Notes Payable	$ 145,900
Impact Of Overall One Percent Increase In Interest Rates Decrease In Fair Values Of Notes Payable Percent	4.10%