Noncontrolling Interest (Noncontrolling Interest Activity) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Balance at beginning of period				$ 1,344				$ 1,029	$ 1,344	$ 1,029
Net income (loss)				3					(4,541)	(35)
Net income attributable to AERC	29,273	19,993	1,638	10,346	6,911	2,093	23,669	(2,081)	61,250	30,592	5,328
Noncontrolling interest cash contribution										350
Balance at end of period	350				1,344				350	1,344	1,029
Change from net income attributable to AERC and net transfers to noncontrolling interests									57,703	30,592
Bristol Development Group [Member]
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Purchase of noncontrolling interest				997				0
Noncontrolling interest cash contribution				0				350
Additional Paid-in Capital
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Net income (loss)									(3,547)
Purchase of noncontrolling interest									$ 3,547	$ 0