Fair Value Measurements (Details 1) (USD $) In Thousands, unless otherwise specified			3 Months Ended		9 Months Ended					3 Months Ended		9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013 Real Estate Funds [Member]	Sep. 30, 2012 Real Estate Funds [Member]	Sep. 30, 2013 Real Estate Funds [Member] Investments	Sep. 30, 2012 Real Estate Funds [Member]	Sep. 30, 2013 Real Estate Funds [Member] Minimum [Member]	Sep. 30, 2013 Real Estate Funds [Member] Maximum [Member]	Sep. 30, 2013 Real Estate Funds [Member] Weighted Average [Member]	Sep. 30, 2013 Deferred Compensation Plan Asset [Member]	Sep. 30, 2012 Deferred Compensation Plan Asset [Member]	Sep. 30, 2013 Deferred Compensation Plan Asset [Member]	Sep. 30, 2012 Deferred Compensation Plan Asset [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Number Of Investments Made By Fund					9
Real Estate Fund Nondepreciable Real Estate	$ 635,990	$ 600,786	$ 635,990		$ 635,990
Excess of fair value over cost			127,118		127,118
Fair Value Inputs Holding Period							0 years 9 months 18 days	6 years 8 months 12 days
Unobservable Quantitative Input [Abstract]
Discount rates							12.00%	17.50%	13.90%
Terminal capitalization rates							5.30%	6.00%	5.70%
Beginning Balance			622,124	388,455	600,786	346,650				66,502	58,313	62,631	56,221
Purchases			7,406	88,429	38,299	163,021				880	1,650	4,027	5,416
Sales / Returns			(14,184)	0	(70,848)	(61,052)				(873)	(276)	(5,318)	(4,287)
Net realized gains			8,184	0	8,184	0
Net unrealized gains			12,367	5,558	59,476	33,537
Realized and unrealized (loss) gains										(42)	1,080	4,094	3,349
Other, Net			93	0	93	286				58	0	1,091	68
Ending Balance			$ 635,990	$ 482,442	$ 635,990	$ 482,442				$ 66,525	$ 60,767	$ 66,525	$ 60,767