Debt (Principal Payments On Mortgage Payable, Notes Payable, Senior Notes and Debentures) (Details) - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
2018		$ 291,734
2019		26,383
2020		107,163
2021		281,235
2022		367,789
Thereafter		2,157,276
Long-term debt	[1]	3,231,580
Mortgages Payable
Debt Instrument [Line Items]
Principal balance		491,561	$ 466,305
2018		16,228
2019		25,820
2020		65,539
2021		30,541
2022		117,018
Thereafter		236,415
Long-term debt		491,561
Notes Payable
Debt Instrument [Line Items]
2018		275,506
2019	[2]	563
2020		41,624
2021	[3]	694
2022		771
Thereafter		1,661
Long-term debt		320,819
Senior Notes and Debentures
Debt Instrument [Line Items]
Principal balance		2,419,200	1,994,200
2018		0
2019		0
2020		0
2021		250,000
2022		250,000
Thereafter		1,919,200
Long-term debt		2,419,200
Revolving credit facility
Debt Instrument [Line Items]
Line of credit facility, annual facility fee		1,000
Revolving credit facility | Notes Payable
Debt Instrument [Line Items]
Revolving credit facility		41,000	0
Term Loan | Notes Payable
Debt Instrument [Line Items]
Other Notes Payable		$ 275,000	$ 275,000

[1] The total debt maturities differ from the total reported on the consolidated balance sheet as of December 31, 2017 due to the unamortized premium/(discount) and debt issuance costs on mortgage loans, notes payable, and senior notes.

[2] Our $275.0 million unsecured term loan matures on November 21, 2018, subject to a one-year extension at our option.

[3] Our $800.0 million revolving credit facility matures on April 20, 2020, subject to two six-month extensions at our option. As of December 31, 2017, there was $41.0 million outstanding under this credit facility.