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, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Fair Value Of SERP Investments	$ 145,577	$ 134,088
Assets, Fair Value Disclosure	145,577	136,088
Other Liabilities, Fair Value Disclosure	145,577	134,088
Liabilities, Fair Value Disclosure	145,601	146,216
Redeemable Noncontrolling Interests - Operating Partnership/Redeemable Limited Partners	436,035	379,106	$ 366,483	$ 366,955
Forward Starting Swaps [Member]
Derivatives, Fair Value [Line Items]
Forward Starting Swaps		2,000
Forward Starting Swaps		9,851
Fair Value Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, fair value	24	2,277
Fair Value, Inputs, Level 1 [Member]
Derivatives, Fair Value [Line Items]
Fair Value Of SERP Investments	145,577	134,088
Assets, Fair Value Disclosure	145,577	134,088
Other Liabilities, Fair Value Disclosure	145,577	134,088
Liabilities, Fair Value Disclosure	145,577	134,088
Redeemable Noncontrolling Interests - Operating Partnership/Redeemable Limited Partners	0	0
Fair Value, Inputs, Level 1 [Member] | Forward Starting Swaps [Member]
Derivatives, Fair Value [Line Items]
Forward Starting Swaps		0
Forward Starting Swaps		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 2 [Member]
Derivatives, Fair Value [Line Items]
Fair Value Of SERP Investments	0	0
Assets, Fair Value Disclosure	0	2,000
Other Liabilities, Fair Value Disclosure	0	0
Liabilities, Fair Value Disclosure	24	12,128
Redeemable Noncontrolling Interests - Operating Partnership/Redeemable Limited Partners	436,035	379,106
Fair Value, Inputs, Level 2 [Member] | Forward Starting Swaps [Member]
Derivatives, Fair Value [Line Items]
Forward Starting Swaps		2,000
Forward Starting Swaps		9,851
Fair Value, Inputs, Level 2 [Member] | Fair Value Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, fair value	24	2,277
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] | Forward Starting Swaps [Member]
Derivatives, Fair Value [Line Items]
Forward Starting Swaps		0
Forward Starting Swaps		0
Fair Value, Inputs, Level 3 [Member] | Fair Value Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, fair value	$ 0	$ 0