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Loans and Allowance for Loan Losses - Summary of Loans By Classification (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2015
Loans and Allowance for Loan Losses
Loans	$ 1,209,152		$ 941,796
Allowance for loan losses	7,457	$ 6,865	6,250	$ 6,010	$ 5,902	$ 5,422
Loans and Leases Receivable, Net Amount, Total	1,201,695		935,546
Mortgage warehouse lines of credit
Loans and Allowance for Loan Losses
Loans	233,466		275,039
Allowance for loan losses	273	281	373	514	770	704
Residential real estate
Loans and Allowance for Loan Losses
Loans	307,643		235,759
Allowance for loan losses	1,524	1,938	2,170	1,725	1,839	2,212
Multi-family and healthcare financing
Loans and Allowance for Loan Losses
Loans	393,581		261,031
Allowance for loan losses	2,702	2,426	1,962	1,896	1,737	1,308
Commercial and commercial real estate
Loans and Allowance for Loan Losses
Loans	210,421		113,812
Allowance for loan losses	2,533	1,845	1,374	1,527	1,243	908
Agricultural production and real estate
Loans and Allowance for Loan Losses
Loans	51,925		46,763
Allowance for loan losses	307	271	269	244	223	222
Consumer and margin loans
Loans and Allowance for Loan Losses
Loans	12,116		9,392
Allowance for loan losses	$ 118	$ 104	$ 102	$ 104	$ 90	$ 68