Fair Value Measurements (Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis
Marketable Securities	$ 203,704	$ 150,997
Real estate fund investments	462,132	574,761
Recurring
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis
Marketable Securities	203,704	150,997
Real estate fund investments	462,132	574,761
Deferred compensation plan assets (included in other assets)	121,374	117,475
Interest rate swap (included in other assets)	21,816
Total assets	809,026	843,233
Mandatorily redeemable instruments (included in other liabilities)	50,561	50,561
Interest rate swap (included in other liabilities)	10,122	19,600
Total liabilities	$ 60,683	$ 70,161
Other Partners Ownership Interest In Real Estate Fund (in percentage)	75.00%	75.00%
Recurring | Level 1
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis
Marketable Securities	$ 203,704	$ 150,997
Real estate fund investments	0	0
Deferred compensation plan assets (included in other assets)	63,930	58,289
Interest rate swap (included in other assets)	0
Total assets	267,634	209,286
Mandatorily redeemable instruments (included in other liabilities)	50,561	50,561
Interest rate swap (included in other liabilities)	0	0
Total liabilities	50,561	50,561
Recurring | Level 2
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis
Marketable Securities	0	0
Real estate fund investments	0	0
Deferred compensation plan assets (included in other assets)	0	0
Interest rate swap (included in other assets)	21,816
Total assets	21,816	0
Mandatorily redeemable instruments (included in other liabilities)	0	0
Interest rate swap (included in other liabilities)	10,122	19,600
Total liabilities	10,122	19,600
Recurring | Level 3
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis
Marketable Securities	0	0
Real estate fund investments	462,132	574,761
Deferred compensation plan assets (included in other assets)	57,444	59,186
Interest rate swap (included in other assets)	0
Total assets	519,576	633,947
Mandatorily redeemable instruments (included in other liabilities)	0	0
Interest rate swap (included in other liabilities)	0	0
Total liabilities	$ 0	$ 0