Commitments and Contingencies (Details)	12 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Accrual for Environmental Loss Contingencies	$ 4,700,000
Litigation Settlement, Amount	3,200,000	$ 6,000,000	$ 2,800,000
Loss Contingency Accrual, Payments	1,500,000
Loss Contingency Accrual, Period Increase (Decrease)	(500,000)
Loss Contingency Accrual	$ 1,000,000
Projects in various stages of development	6
Units in various stages of development	2,064
Consolidated Project Under Development Commitment Fund	$ 260,600,000
Total operating lease payments	26,200,000	24,500,000	21,200,000
Compensation expense, Recognized	300,000	$ 400,000	$ 500,000
Operating Leases:
Minimum Rent Payments Due, Year 1	(15,917,000)
Minimum Rent Payments Due, Year 2	(16,027,000)
Minimum Rent Payments Due, Year 3	(15,890,000)
Minimum Rent Payments Due, Year 4	(15,489,000)
Minimum Rent Payments Due, Year 5	(15,256,000)
Minimum Rent Payments Due, Thereafter	(826,259,000)
Minimum Rent Payments Due, Total	(904,838,000)
Operating Leases, Future Minimum Payments Receivable, Current	73,171,000
Operating Leases, Future Minimum Payments Receivable, in Two Years	60,004,000
Operating Leases, Future Minimum Payments Receivable, in Three Years	54,486,000
Operating Leases, Future Minimum Payments Receivable, in Four Years	50,705,000
Operating Leases, Future Minimum Payments Receivable, in Five Years	46,634,000
Operating Leases, Future Minimum Payments Receivable, Thereafter	211,853,000
Operating Leases, Future Minimum Payments Receivable	496,853,000
Other Long-Term Liabilities:
Deferred Compensation Due, Year 1	(1,387,000)
Deferred Compensation Due, Year 2	(1,723,000)
Deferred Compensation Due, Year 3	(1,128,000)
Deferred Compensation Due, Year 4	(1,079,000)
Deferred Compensation Due, Year 5	(1,079,000)
Deferred Compensation Due, Thereafter	(4,383,000)
Deferred Compensation Due, Total	$ (10,779,000)
Partially Owned Properties – Unconsolidated
Number Of Unconsolidated Projects	2
FHA Lawsuit [Member]
Litigation Settlement, Amount	$ 3,100,000