Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities	$ 184,154	$ 191,917
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities	184,154	191,917
Real Estate Fund investments (75% of which is attributable to noncontrolling interests)	495,392	667,710
Deferred compensation plan assets (included in other assets)	113,549	116,515
Total assets	793,095	976,142
Mandatorily redeemable instruments (included in other liabilities)	55,096	55,097
Interest rate swap (included in other liabilities)	26,036	31,882
Total liabilities	81,132	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	1,328	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	184,154	191,917
Real Estate Fund investments (75% of which is attributable to noncontrolling interests)	0	0
Deferred compensation plan assets (included in other assets)	50,366	47,733
Total assets	234,520	239,650
Mandatorily redeemable instruments (included in other liabilities)	55,096	55,097
Interest rate swap (included in other liabilities)	0	0
Total liabilities	55,096	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	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)	26,036	31,882
Total liabilities	26,036	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	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)	495,392	667,710
Deferred compensation plan assets (included in other assets)	63,183	68,782
Total assets	558,575	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	1,328	83,224
Total Assets, Nonrecurring		$ 437,575