Noncontrolling Interest (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013 item	Jun. 30, 2012
Redeemable Noncontrolling Interest
Number of firms in which entity holds majority ownership interest	5
Fair value of noncontrolling owners equity interests	$ 39,943
Redeemable noncontrolling interest
Balance, beginning of period	41,112
Net income	1,048	652
Balance, end of period	39,943
Redeemable Noncontrolling Interest
Redeemable Noncontrolling Interest
Number of firms in which entity holds majority ownership interest	5
Fair value of noncontrolling owners equity interests	39,943	41,899
Redeemable noncontrolling interest
Balance, beginning of period	41,112	44,643
Net income	1,048	652
Distributions to redeemable noncontrolling interest	(940)	(867)
Additions and redemptions, net	(1,693)	(1,737)
Adjustments to fair value	416	(792)
Balance, end of period	$ 39,943	$ 41,899