Other Asset and Other Liabilities - Intangible assets (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Finite-lived intangible assets	$ 6,647		$ 6,647
Total Intangible Assets	7,647		7,647		$ 8,309
Amortization expense	300	$ 100	700	$ 200
Total Accumulated Amortization	1,935		1,935
Future amortization of lease intangibles
2020	661		661
2021	1,295		1,295
2022	1,268		1,268
2023	1,242		1,242
2024	1,210		1,210
Thereafter	971		971
Net amount	6,647		6,647
SBA license
Indefinite-lived intangible assets	1,000		1,000		1,000
Internally developed software | Knight Capital
Finite-lived intangible assets	3,378		$ 3,378		3,694
Estimated Useful Life			6 years
Total Accumulated Amortization	422		$ 422
Future amortization of lease intangibles
Net amount	3,378		3,378		3,694
Broker network | Knight Capital
Finite-lived intangible assets	1,022		$ 1,022		1,156
Estimated Useful Life			4 years 6 months
Total Accumulated Amortization	178		$ 178
Future amortization of lease intangibles
Net amount	1,022		1,022		1,156
Trade name | Knight Capital
Finite-lived intangible assets	782		$ 782		855
Estimated Useful Life			6 years
Total Accumulated Amortization	98		$ 98
Future amortization of lease intangibles
Net amount	782		782		855
Trade name | GMFS
Finite-lived intangible assets	629		$ 629		699
Estimated Useful Life			15 years
Total Accumulated Amortization	594		$ 594
Future amortization of lease intangibles
Net amount	629		629		699
Favorable lease
Finite-lived intangible assets	836		$ 836		905
Estimated Useful Life			12 years
Total Accumulated Amortization	643		$ 643
Future amortization of lease intangibles
Net amount	$ 836		$ 836		$ 905