Noncontrolling Interest (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012 item	Dec. 31, 2011	Dec. 31, 2010
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	$ 41,112	$ 44,643	$ 45,676
Redeemable noncontrolling interest
Balance, beginning of period	44,643	45,676	51,381
Net income	1,084	1,956	1,779
Distributions to redeemable noncontrolling interest	(1,451)	(2,061)	(2,105)
Additions and redemptions, net	(2,811)	(5,304)	(6,231)
Adjustments to fair value	(353)	5,003	852
Other		(627)
Balance, end of period	$ 41,112	$ 44,643	$ 45,676