Fair Value Measurements - Summary of Fair Value Measurements for Each Major Category of Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Fair Value Of SERP Investments	$ 160,914	$ 160,293
Other Liabilities, Fair Value Disclosure	160,914	160,293
Redeemable Noncontrolling Interests - Operating Partnership/Redeemable Limited Partners	459,933	338,951	$ 293,706	$ 463,400
Fair Value, Inputs, Level 1 [Member]
Derivatives, Fair Value [Line Items]
Fair Value Of SERP Investments	160,914	160,293
Other Liabilities, Fair Value Disclosure	160,914	160,293
Redeemable Noncontrolling Interests - Operating Partnership/Redeemable Limited Partners	0	0
Fair Value, Inputs, Level 2 [Member]
Derivatives, Fair Value [Line Items]
Fair Value Of SERP Investments	0	0
Other Liabilities, Fair Value Disclosure	0	0
Redeemable Noncontrolling Interests - Operating Partnership/Redeemable Limited Partners	459,933	338,951
Fair Value, Inputs, Level 3 [Member]
Derivatives, Fair Value [Line Items]
Fair Value Of SERP Investments	0	0
Other Liabilities, Fair Value Disclosure	0	0
Redeemable Noncontrolling Interests - Operating Partnership/Redeemable Limited Partners	$ 0	$ 0