Commitments And Contingencies (Narrative) (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Long-term Purchase Commitment [Line Items]
Shares issued in exchange of interests	$ 0
Notes receivable from real estate joint ventures and partnerships			16,100,000
Receipt of cash and real property			19,100,000
Increase in noncontrolling interests	(10,932,000)	0	16,200,000
Total assets	3,869,172,000		4,223,929,000
DownREIT [Member]
Long-term Purchase Commitment [Line Items]
Number of real estate joint ventures	3		3
Shares issued in exchange of interests	0	0
Aggregate redemption value	45,000,000		41,000,000
Consoldiated Real Estate Joint Ventures [Member]
Long-term Purchase Commitment [Line Items]
Number of real estate joint ventures			2
Unconsolidated Real Estate Joint Ventures [Member]
Long-term Purchase Commitment [Line Items]
Number of real estate joint ventures			2
Total assets	1,273,580,000		1,283,166,000
Unconsolidated Real Estate Joint Ventures [Member] | Sheridan, Colorado [Member]
Long-term Purchase Commitment [Line Items]
Total assets			23,200,000
Capital Additions [Member]
Long-term Purchase Commitment [Line Items]
Construction contract, commitment	$ 58,600,000
Capital Additions [Member] | Minimum [Member]
Long-term Purchase Commitment [Line Items]
Construction contract, period (in months)	12
Capital Additions [Member] | Maximum [Member]
Long-term Purchase Commitment [Line Items]
Construction contract, period (in months)	36