Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities	$ 205,042	$ 191,917
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities	205,042	191,917
Real Estate Fund investments	682,002	667,710
Deferred Compensation Plan Assets	121,970	116,515
Total assets	1,009,014	976,142
Mandatorily redeemable instruments (included in other liabilities)	55,097	55,097
Interest rate swap (included in other liabilities)	30,272	31,882
Total liabilities	85,369	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	341,660	354,351
Investments in Partially Owned Entities at Fair Value	75,932	83,224
Total Assets, Nonrecurring	417,592	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	205,042	191,917
Real Estate Fund investments	0	0
Deferred Compensation Plan Assets	54,343	47,733
Total assets	259,385	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	0
Investments in Partially Owned Entities at Fair Value	0	0
Total Assets, Nonrecurring	0	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	0	0
Deferred Compensation Plan Assets	0	0
Total assets	0	0
Mandatorily redeemable instruments (included in other liabilities)	0	0
Interest rate swap (included in other liabilities)	30,272	31,882
Total liabilities	30,272	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	0
Investments in Partially Owned Entities at Fair Value	0	0
Total Assets, Nonrecurring	0	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	682,002	667,710
Deferred Compensation Plan Assets	67,627	68,782
Total assets	749,629	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	341,660	354,351
Investments in Partially Owned Entities at Fair Value	75,932	83,224
Total Assets, Nonrecurring	$ 417,592	$ 437,575