Revenues from contracts with customers (Contract Assets and Liabilities) (Details) - USD ($)	Mar. 31, 2019	Jan. 01, 2019
Capitalized Contract Cost [Line Items]
Contract assets	$ 26,210,000	$ 23,680,000
Deferred income, IRA fees	2,415,000	318,000
Commission
Capitalized Contract Cost [Line Items]
Contract assets	3,201,000	3,738,000
Mutual Fund Income
Capitalized Contract Cost [Line Items]
Contract assets	6,674,000	7,241,000
Advisory fees
Capitalized Contract Cost [Line Items]
Contract assets	863,000	1,214,000
Bank Deposit Sweep Income
Capitalized Contract Cost [Line Items]
Contract assets	4,521,000	4,622,000
Investment Banking Fees
Capitalized Contract Cost [Line Items]
Contract assets	7,610,000	3,996,000
Other Income [Member]
Capitalized Contract Cost [Line Items]
Contract assets	3,341,000	2,869,000
Investment Banking Fees
Capitalized Contract Cost [Line Items]
Deferred income, IRA fees	415,000	318,000
IRA fees
Capitalized Contract Cost [Line Items]
Deferred income, IRA fees	$ 2,000,000	$ 0