Fair Value Measurements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities	$ 150,997	$ 206,323
Real estate fund investments	574,761	513,973
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities	150,997	206,323
Real estate fund investments	574,761	513,973
Deferred compensation plan assets (included in other assets)	117,475	117,284
Total assets	843,233	837,580
Mandatorily redeemable instruments (included in other liabilities)	50,561	55,097
Interest rate swap (included in other liabilities)	19,600	25,797
Total liabilities	$ 70,161	$ 80,894
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	$ 0	$ 4,848
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	150,997	206,323
Real estate fund investments	0	0
Deferred compensation plan assets (included in other assets)	58,289	53,969
Total assets	209,286	260,292
Mandatorily redeemable instruments (included in other liabilities)	50,561	55,097
Interest rate swap (included in other liabilities)	0	0
Total liabilities	50,561	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
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 (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)	19,600	25,797
Total liabilities	19,600	25,797
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
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	574,761	513,973
Deferred compensation plan assets (included in other assets)	59,186	63,315
Total assets	633,947	577,288
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		$ 4,848