Loans and Allowance for Loan Losses - Aging Analysis Of The Recorded Investment In Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Aging analysis of loan portfolio
Past due loans	$ 12,608	$ 3,217
Current loans	3,015,702	2,054,910
Loans and Leases Receivable, Net of Deferred Income, Total	3,028,310	2,058,127
30-59 Days Past Due
Aging analysis of loan portfolio
Past due loans	7,479	917
60-89 Days Past Due
Aging analysis of loan portfolio
Past due loans	928	282
Greater Than 90 Days
Aging analysis of loan portfolio
Past due loans	4,201	2,018
Mortgage warehouse lines of credit
Aging analysis of loan portfolio
Past due loans		324
Current loans	765,151	337,008
Loans and Leases Receivable, Net of Deferred Income, Total	765,151	337,332
Mortgage warehouse lines of credit | Greater Than 90 Days
Aging analysis of loan portfolio
Past due loans		324
Residential real estate
Aging analysis of loan portfolio
Past due loans	5,975	1,582
Current loans	407,860	409,289
Loans and Leases Receivable, Net of Deferred Income, Total	413,835	410,871
Residential real estate | 30-59 Days Past Due
Aging analysis of loan portfolio
Past due loans	3,089	579
Residential real estate | 60-89 Days Past Due
Aging analysis of loan portfolio
Past due loans	562	178
Residential real estate | Greater Than 90 Days
Aging analysis of loan portfolio
Past due loans	2,324	825
Multi-family and healthcare financing
Aging analysis of loan portfolio
Current loans	1,347,125	914,393
Loans and Leases Receivable, Net of Deferred Income, Total	1,347,125	914,393
Commercial and commercial real estate
Aging analysis of loan portfolio
Past due loans	4,291	550
Current loans	394,310	298,644
Loans and Leases Receivable, Net of Deferred Income, Total	398,601	299,194
Commercial and commercial real estate | 30-59 Days Past Due
Aging analysis of loan portfolio
Past due loans	2,293	245
Commercial and commercial real estate | 60-89 Days Past Due
Aging analysis of loan portfolio
Past due loans	335	52
Commercial and commercial real estate | Greater Than 90 Days
Aging analysis of loan portfolio
Past due loans	1,663	253
Agricultural production and real estate
Aging analysis of loan portfolio
Past due loans	2,242	679
Current loans	82,968	78,576
Loans and Leases Receivable, Net of Deferred Income, Total	85,210	79,255
Agricultural production and real estate | 30-59 Days Past Due
Aging analysis of loan portfolio
Past due loans	2,047	91
Agricultural production and real estate | Greater Than 90 Days
Aging analysis of loan portfolio
Past due loans	195	588
Consumer and margin loans
Aging analysis of loan portfolio
Past due loans	100	82
Current loans	18,288	17,000
Loans and Leases Receivable, Net of Deferred Income, Total	18,388	17,082
Consumer and margin loans | 30-59 Days Past Due
Aging analysis of loan portfolio
Past due loans	50	2
Consumer and margin loans | 60-89 Days Past Due
Aging analysis of loan portfolio
Past due loans	31	52
Consumer and margin loans | Greater Than 90 Days
Aging analysis of loan portfolio
Past due loans	$ 19	$ 28