Fair Value Measurements (Details - Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities	$ 198,165	$ 150,997
Real estate fund investments	519,386	574,761
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities	198,165	150,997
Real estate fund investments	519,386	574,761
Deferred compensation plan assets (included in other assets)	118,359	117,475
Interest rate swap (included in other assets)	3,064
Total assets	838,974	843,233
Mandatorily redeemable instruments (included in other liabilities)	50,561	50,561
Interest rate swaps (included in other liabilities)	23,646	19,600
Total liabilities	74,207	70,161
Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities	198,165	150,997
Real estate fund investments	0	0
Deferred compensation plan assets (included in other assets)	61,444	58,289
Interest rate swap (included in other assets)	0
Total assets	259,609	209,286
Mandatorily redeemable instruments (included in other liabilities)	50,561	50,561
Interest rate swaps (included in other liabilities)	0	0
Total liabilities	50,561	50,561
Fair Value Inputs Level 2 | Fair Value, Measurements, Recurring
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
Interest rate swap (included in other assets)	3,064
Total assets	3,064	0
Mandatorily redeemable instruments (included in other liabilities)	0	0
Interest rate swaps (included in other liabilities)	23,646	19,600
Total liabilities	23,646	19,600
Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities	0	0
Real estate fund investments	519,386	574,761
Deferred compensation plan assets (included in other assets)	56,915	59,186
Interest rate swap (included in other assets)	0
Total assets	576,301	633,947
Mandatorily redeemable instruments (included in other liabilities)	0	0
Interest rate swaps (included in other liabilities)	0	0
Total liabilities	$ 0	$ 0