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	Sep. 30, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Fair Value Of SERP Investments	$ 136,774	$ 124,420
Assets, Fair Value Disclosure	141,139	126,277
Other Liabilities, Fair Value Disclosure	136,774	124,420
Liabilities, Fair Value Disclosure	136,774	124,420
Redeemable Noncontrolling Interests – Operating Partnership/Redeemable Limited Partners	380,541	442,092
Fair Value Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	444	1,857
Forward Starting Swaps [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	3,921
Fair Value, Inputs, Level 1 [Member]
Derivatives, Fair Value [Line Items]
Fair Value Of SERP Investments	136,774	124,420
Assets, Fair Value Disclosure	136,774	124,420
Other Liabilities, Fair Value Disclosure	136,774	124,420
Liabilities, Fair Value Disclosure	136,774	124,420
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 Asset	0	0
Fair Value, Inputs, Level 1 [Member] | Forward Starting Swaps [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	0
Fair Value, Inputs, Level 2 [Member]
Derivatives, Fair Value [Line Items]
Fair Value Of SERP Investments	0	0
Assets, Fair Value Disclosure	4,365	1,857
Other Liabilities, Fair Value Disclosure	0	0
Liabilities, Fair Value Disclosure	0	0
Redeemable Noncontrolling Interests – Operating Partnership/Redeemable Limited Partners	380,541	442,092
Fair Value, Inputs, Level 2 [Member] | Fair Value Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	444	1,857
Fair Value, Inputs, Level 2 [Member] | Forward Starting Swaps [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	3,921
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 Asset	0	$ 0
Fair Value, Inputs, Level 3 [Member] | Forward Starting Swaps [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	$ 0