Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2014	Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities	$ 206,917	$ 191,917
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities	206,917	191,917
Real Estate Fund investments (75% of which is attributable to noncontrolling interests)	549,091	667,710
Deferred compensation plan assets (included in other assets)	111,858	116,515
Total assets	867,866	976,142
Mandatorily redeemable instruments (included in other liabilities)	55,097	55,097
Interest rate swap (included in other liabilities)	30,817	31,882
Total liabilities	85,914	86,979
Other Partners Ownership Interest In Real Estate Fund (in percentage)	75.00%	75.00%
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Real Estate, Net at Fair Value		354,351
Investments in Partially Owned Entities at Fair Value		83,224
Total Assets, Nonrecurring		437,575
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities	206,917	191,917
Real Estate Fund investments (75% of which is attributable to noncontrolling interests)	0	0
Deferred compensation plan assets (included in other assets)	47,249	47,733
Total assets	254,166	239,650
Mandatorily redeemable instruments (included in other liabilities)	55,097	55,097
Interest rate swap (included in other liabilities)	0	0
Total liabilities	55,097	55,097
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Real Estate, Net at Fair Value		0
Investments in Partially Owned Entities at Fair Value		0
Total Assets, Nonrecurring		0
Fair Value Inputs Level 2 Member | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities	0	0
Real Estate Fund investments (75% of which is attributable to noncontrolling interests)	0	0
Deferred compensation plan assets (included in other assets)	0	0
Total assets	0	0
Mandatorily redeemable instruments (included in other liabilities)	0	0
Interest rate swap (included in other liabilities)	30,817	31,882
Total liabilities	30,817	31,882
Fair Value Inputs Level 2 Member | Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Real Estate, Net at Fair Value		0
Investments in Partially Owned Entities at Fair Value		0
Total Assets, Nonrecurring		0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities	0	0
Real Estate Fund investments (75% of which is attributable to noncontrolling interests)	549,091	667,710
Deferred compensation plan assets (included in other assets)	64,609	68,782
Total assets	613,700	736,492
Mandatorily redeemable instruments (included in other liabilities)	0	0
Interest rate swap (included in other liabilities)	0	0
Total liabilities	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Real Estate, Net at Fair Value		354,351
Investments in Partially Owned Entities at Fair Value		83,224
Total Assets, Nonrecurring		$ 437,575