Noncontrolling Interest (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012 entity trustsubsidiaries	Mar. 31, 2011
Noncontrolling Interest
Number of real estate investment trust subsidiaries	2
Number of firms in which entity holds majority ownership interest	5
Fair value of noncontrolling owners equity interests	$ 43,436	$ 46,013
Redeemable noncontrolling interest
Balance, beginning of period	44,643	45,676
Net income	243	558
Distributions to redeemable noncontrolling interest	(289)	(484)
Additions and redemptions, net	(1,272)	(559)
Adjustments to fair value	111	822
Balance, end of period	$ 43,436	$ 46,013