Business Segment Information (Schedule of Financial Information About Business Segments) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Revenues	$ 424,927	$ 416,254	$ 1,240,335	$ 1,226,660
Expenses	295,550	279,380	865,044	829,481
Operating profit (loss)	129,377	136,874	375,291	397,179
Private Banks
Segment Reporting Information [Line Items]
Revenues	114,792	117,250	335,739	351,601
Expenses	113,066	110,788	331,442	329,540
Operating profit (loss)	1,726	6,462	4,297	22,061
Investment Advisors
Segment Reporting Information [Line Items]
Revenues	103,189	103,033	299,218	297,916
Expenses	51,519	51,509	154,100	154,569
Operating profit (loss)	51,670	51,524	145,118	143,347
Institutional Investors
Segment Reporting Information [Line Items]
Revenues	79,583	80,337	235,309	241,559
Expenses	37,812	37,268	113,016	115,383
Operating profit (loss)	41,771	43,069	122,293	126,176
Investment Managers
Segment Reporting Information [Line Items]
Revenues	123,846	112,186	359,815	326,037
Expenses	79,838	71,889	228,795	209,326
Operating profit (loss)	44,008	40,297	131,020	116,711
Investments In New Businesses
Segment Reporting Information [Line Items]
Revenues	3,517	3,448	10,254	9,547
Expenses	13,315	7,926	37,691	20,663
Operating profit (loss)	$ (9,798)	$ (4,478)	$ (27,437)	$ (11,116)