Commitments and Contingencies (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
300 properties designed and built in violation of accessibility requirements	300
Projects in various stages of development	15
Units in various stages of development	4,917
Consolidated Project Under Development Commitment Fund	$ 1,200,000,000
Various stages of development with estimated completion dates ranging through June 30, 2016	Sep. 30, 2017
Number Of Unconsolidated Projects	1
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets	498,640,000	108,000,000
Investment in Joint Venture	336,900,000
Noncontrolling Interests - Partially Owned Properties	124,909,000	126,583,000
Number Of Operating Properties Under Long Term Ground Leases	13
Total operating lease payments	14,700,000	13,200,000	8,100,000
Compensation expense, Recognized	500,000	500,000	1,000,000
Number Of Operating Properties and Land Parcels Under Long Term Ground Leases	14
Operating Leases:
Minimum Rent Payments Due, Year 1	(15,268,000)
Minimum Rent Payments Due, Year 2	(15,385,000)
Minimum Rent Payments Due, Year 3	(15,318,000)
Minimum Rent Payments Due, Year 4	(15,298,000)
Minimum Rent Payments Due, Year 5	(15,224,000)
Minimum Rent Payments Due, Thereafter	(860,071,000)
Minimum Rent Payments Due, Total	(936,564,000)
Other Long-Term Liabilities:
Deferred Compensation Due, Year 1	(1,382,000)
Deferred Compensation Due, Year 2	(1,714,000)
Deferred Compensation Due, Year 3	(1,714,000)
Deferred Compensation Due, Year 4	(1,714,000)
Deferred Compensation Due, Year 5	(1,120,000)
Defined Benefit Plan, Expected Future Benefit Payments in Five Fiscal Years Thereafter	(5,149,000)
Deferred Compensation Due, Total	(12,793,000)
Loss Contingency Accrual, Period Increase (Decrease)	4,000,000
Loss Contingency Accrual	6,000,000
Company's Portion [Member]
Land purchase price	76,100,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets	102,500,000
Joint Venture Partner [Member]
Land purchase price	57,900,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets	75,700,000
Noncontrolling Interests - Partially Owned Properties	117,400,000
531190 Lessors of Other Real Estate Property [Member]
Operating Leases:
Minimum Rent Payments Due, Year 1	(65,087,000)
Minimum Rent Payments Due, Year 2	(58,860,000)
Minimum Rent Payments Due, Year 3	(53,448,000)
Minimum Rent Payments Due, Year 4	(43,987,000)
Minimum Rent Payments Due, Year 5	(37,545,000)
Minimum Rent Payments Due, Thereafter	(192,455,000)
Minimum Rent Payments Due, Total	$ (451,382,000)