Indebtedness (Tables)

12 Months Ended

Dec. 31, 2011

Indebtedness [Abstract]

Schedule of Debt [Table Text Block]

											Weighted
	Mortgages										Average
	Principal		Principal		Unsecured		Credit				Interest
	Amortization		Maturities		Notes		Facility		Total		Rate
2012	$	4,931	$	30,114	$	230,100	$	—	$	265,145	6.47	%
2013	4,582		4,510		—		—		9,092		5.73	%
2014	4,965		2,684		200,000		—		207,649		5.66	%
2015	4,511		44,469		316,000		139,400		504,380		4.15	%
2016	3,068		182,318		300,000		—		485,386		6.10	%
2017	2,318		2,349		296,543		—		301,210		6.61	%
2018	—		—		100,000		—		100,000		7.50	%
2019	—		—		—		—		—		—
2020	—		—		350,000		—		350,000		4.75	%
	$	24,375	$	266,444	$	1,792,643	$	139,400	$	2,222,862	5.58	%