Fair Value Measurements, Measured On Recurring Basis Significant Unobservable Inputs (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Available-for-sale Securities [Member] | Municipal and Other Tax-exempt Securities [Member]
Fair Value Assets Measured on Recurring Basis Unobservable Reconciliation [Roll Forward]
Balance at beginning of period	$ 41,662	$ 43,658	$ 42,353	$ 47,093
Purchases and capital calls	0	0	0	7,520
Redemptions and distributions	1	(100)	(462)	(10,075)
Gain (loss) recognized in earnings [Abstract]
Brokerage and trading revenue		0		(576)
Gain on other assets, net	0	0	0	0
Gain on available for sale securities, net	0	1	1	19
Other-than-temporary impairment losses	0	0	0	(521)
Other comprehensive gain (loss)	(384)	153	(613)	252
Balance at end of period	41,279	43,712	41,279	43,712
Available-for-sale Securities [Member] | Other Debt Obligations [Member]
Fair Value Assets Measured on Recurring Basis Unobservable Reconciliation [Roll Forward]
Balance at beginning of period	5,388	5,893	5,900	6,400
Purchases and capital calls	0	0	0	0
Redemptions and distributions	0	0	(500)	(500)
Gain (loss) recognized in earnings [Abstract]
Brokerage and trading revenue		0		0
Gain on other assets, net	0	0	0	0
Gain on available for sale securities, net	0	0	0	0
Other-than-temporary impairment losses	0	0	0	0
Other comprehensive gain (loss)	12	7	0	0
Balance at end of period	5,400	5,900	5,400	5,900
Other Assets [Member] | Private Equity Funds [Member]
Fair Value Assets Measured on Recurring Basis Unobservable Reconciliation [Roll Forward]
Balance at beginning of period	31,492	28,313	30,902	25,436
Purchases and capital calls	476	813	2,385	2,465
Redemptions and distributions	(3,906)	(714)	(7,072)	(2,899)
Gain (loss) recognized in earnings [Abstract]
Brokerage and trading revenue		0		0
Gain on other assets, net	730	701	2,577	4,111
Gain on available for sale securities, net	0	0	0	0
Other-than-temporary impairment losses	0	0	0	0
Other comprehensive gain (loss)	0	0	0	0
Balance at end of period	$ 28,792	$ 29,113	$ 28,792	$ 29,113