Derivative and Other Fair Value Instruments - Summary of Fair Value Measurements for Each Major Category of Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Fair Value Of SERP Investments	$ 140,432	$ 140,159
Assets, Fair Value Disclosure	157,163	145,302
Other Liabilities, Fair Value Disclosure	140,432	140,159
Liabilities, Fair Value Disclosure	145,411	141,756
Redeemable Noncontrolling Interests - Operating Partnership/Redeemable Limited Partners	366,483	366,955
Fair Value Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, fair value	3,748	1,597
Forward Starting Swaps [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	16,731	5,143
Other Liabilities, Forward Starting Swaps	1,231
Fair Value, Inputs, Level 1 [Member]
Derivatives, Fair Value [Line Items]
Fair Value Of SERP Investments	140,432	140,159
Assets, Fair Value Disclosure	140,432	140,159
Other Liabilities, Fair Value Disclosure	140,432	140,159
Liabilities, Fair Value Disclosure	140,432	140,159
Redeemable Noncontrolling Interests - Operating Partnership/Redeemable Limited Partners	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, fair value	0	0
Fair Value, Inputs, Level 1 [Member] | Forward Starting Swaps [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	0	0
Other Liabilities, Forward Starting Swaps	0
Fair Value, Inputs, Level 2 [Member]
Derivatives, Fair Value [Line Items]
Fair Value Of SERP Investments	0	0
Assets, Fair Value Disclosure	16,731	5,143
Other Liabilities, Fair Value Disclosure	0	0
Liabilities, Fair Value Disclosure	4,979	1,597
Redeemable Noncontrolling Interests - Operating Partnership/Redeemable Limited Partners	366,483	366,955
Fair Value, Inputs, Level 2 [Member] | Fair Value Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, fair value	3,748	1,597
Fair Value, Inputs, Level 2 [Member] | Forward Starting Swaps [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	16,731	5,143
Other Liabilities, Forward Starting Swaps	1,231
Fair Value, Inputs, Level 3 [Member]
Derivatives, Fair Value [Line Items]
Fair Value Of SERP Investments	0	0
Assets, Fair Value Disclosure	0	0
Other Liabilities, Fair Value Disclosure	0	0
Liabilities, Fair Value Disclosure	0	0
Redeemable Noncontrolling Interests - Operating Partnership/Redeemable Limited Partners	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, fair value	0	0
Fair Value, Inputs, Level 3 [Member] | Forward Starting Swaps [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	0	$ 0
Other Liabilities, Forward Starting Swaps	$ 0