Revenues from contracts with customers (Contract Assets and Liabilities) (Details) - USD ($)	Sep. 30, 2019	Jan. 01, 2019
Capitalized Contract Cost [Line Items]
Contract assets	$ 25,195,000	$ 23,680,000
Deferred income, IRA fees	1,722,000	318,000
Commission
Capitalized Contract Cost [Line Items]
Contract assets	3,295,000	3,738,000
Mutual Fund Income
Capitalized Contract Cost [Line Items]
Contract assets	6,836,000	7,241,000
Advisory fees
Capitalized Contract Cost [Line Items]
Contract assets	1,013,000	1,214,000
Bank Deposit Sweep Income
Capitalized Contract Cost [Line Items]
Contract assets	3,911,000	4,622,000
Investment Banking Fees
Capitalized Contract Cost [Line Items]
Contract assets	7,688,000	3,996,000
Other Income [Member]
Capitalized Contract Cost [Line Items]
Contract assets	2,452,000	2,869,000
Investment Banking Fees
Capitalized Contract Cost [Line Items]
Deferred income, IRA fees	1,055,000	318,000
IRA fees (7)
Capitalized Contract Cost [Line Items]
Deferred income, IRA fees	$ 667,000	$ 0