Noncontrolling Interest (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013 item	Mar. 31, 2012
Redeemable Noncontrolling Interest
Number of firms in which entity holds majority ownership interest	5
Fair value of noncontrolling owners equity interests	$ 41,113
Redeemable noncontrolling interest
Balance, beginning of period	41,112
Net income	585	243
Balance, end of period	41,113
Redeemable Noncontrolling Interest
Redeemable Noncontrolling Interest
Number of firms in which entity holds majority ownership interest	5
Fair value of noncontrolling owners equity interests	41,113	43,436
Redeemable noncontrolling interest
Balance, beginning of period	41,112	44,643
Net income	585	243
Distributions to redeemable noncontrolling interest	(319)	(289)
Additions and redemptions, net	(324)	(1,272)
Adjustments to fair value	59	111
Balance, end of period	$ 41,113	$ 43,436