Business Segment Information (Schedule of Financial Information About Business Segments) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Revenues	$ 400,646	$ 409,586	$ 815,408	$ 810,406
Expenses	282,943	272,877	569,494	550,101
Operating profit (loss)	117,703	136,709	245,914	260,305
Private Banks
Segment Reporting Information [Line Items]
Revenues	107,726	116,092	220,947	234,351
Expenses	107,723	107,790	218,376	218,752
Operating profit (loss)	3	8,302	2,571	15,599
Investment Advisors
Segment Reporting Information [Line Items]
Revenues	93,708	100,122	196,029	194,883
Expenses	50,149	50,558	102,581	103,060
Operating profit (loss)	43,559	49,564	93,448	91,823
Institutional Investors
Segment Reporting Information [Line Items]
Revenues	76,523	81,109	155,726	161,222
Expenses	36,937	39,361	75,204	78,115
Operating profit (loss)	39,586	41,748	80,522	83,107
Investment Managers
Segment Reporting Information [Line Items]
Revenues	119,340	109,202	235,969	213,851
Expenses	74,668	68,371	148,957	137,437
Operating profit (loss)	44,672	40,831	87,012	76,414
Investments In New Businesses
Segment Reporting Information [Line Items]
Revenues	3,349	3,061	6,737	6,099
Expenses	13,466	6,797	24,376	12,737
Operating profit (loss)	$ (10,117)	$ (3,736)	$ (17,639)	$ (6,638)