Fair Value of Financial Instruments - Carrying values and estimated fair values of financial instruments (Details) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Dec. 31, 2013
Carrying values and estimated fair values of financial instruments:
Prepayments of principal amount of loans assumed	$ 0
Financial assets:
Cash and cash equivalents	25,135	$ 30,077	$ 62,509	$ 39,843
Certificates of deposit with other banks	13,150	11,907
Securities available-for-sale	68,158	68,213
Securities held-to-maturity	53,923	55,871
Financial liabilities:
FHLB and other borrowings	102,468	101,287
Level I
Financial assets:
Cash and cash equivalents	25,135	30,077
Securities available-for-sale	88	77
Level II
Financial assets:
Certificates of deposit with other banks	13,341	12,035
Securities available-for-sale	68,070	68,136
Securities held-to-maturity	53,923	55,871
Loans held for sale	73,047	69,527
Accrued interest receivable	800	728
Financial liabilities:
Deposits	1,019,968	824,078
Repurchase agreements	26,562	32,673
FHLB and other borrowings	102,476	101,338
Accrued interest payable	458	376
Subordinated debt	31,172	31,172
Level III
Financial assets:
Loans, net	1,000,857	803,036
Mortgage servicing rights	1,155	1,423
Accrued interest receivable	2,450	1,659
Carrying Value
Financial assets:
Cash and cash equivalents	25,135	30,077
Certificates of deposit with other banks	13,150	11,907
Securities available-for-sale	68,158	68,213
Securities held-to-maturity	52,969	54,538
Loans held for sale	73,047	69,527
Loans, net	994,833	792,074
Mortgage servicing rights	1,155	1,423
Accrued interest receivable	3,250	2,387
Financial liabilities:
Deposits	1,018,255	823,227
Repurchase agreements	26,562	32,673
FHLB and other borrowings	102,468	101,287
Accrued interest payable	458	376
Subordinated debt	33,524	33,524
Total
Financial assets:
Cash and cash equivalents	25,135	30,077
Certificates of deposit with other banks	13,341	12,035
Securities available-for-sale	68,158	68,213
Securities held-to-maturity	53,923	55,871
Loans held for sale	73,047	69,527
Loans, net	1,000,857	803,036
Mortgage servicing rights	1,155	1,423
Accrued interest receivable	3,250	2,387
Financial liabilities:
Deposits	1,019,968	824,078
Repurchase agreements	26,562	32,673
FHLB and other borrowings	102,476	101,338
Accrued interest payable	458	376
Subordinated debt	31,172	31,172
Interest rate lock commitment | Level III
Financial assets:
Derivative asset	1,758	1,020
Interest rate lock commitment | Carrying Value
Financial assets:
Derivative asset	1,758	1,020
Interest rate lock commitment | Total
Financial assets:
Derivative asset	1,758	1,020
Interest rate swap | Level II
Financial assets:
Derivative asset	580
Financial liabilities:
Derivative Liability	580
Interest rate swap | Carrying Value
Financial assets:
Derivative asset	580
Financial liabilities:
Derivative Liability	580
Interest rate swap | Total
Financial assets:
Derivative asset	580
Financial liabilities:
Derivative Liability	580
Interest rate cap | Level II
Financial assets:
Derivative asset	443	1,423
Interest rate cap | Carrying Value
Financial assets:
Derivative asset	443	1,423
Interest rate cap | Total
Financial assets:
Derivative asset	443	1,423
Forward sales commitments | Level II
Financial liabilities:
Derivative Liability	417	431
Forward sales commitments | Carrying Value
Financial liabilities:
Derivative Liability	417	431
Forward sales commitments | Total
Financial liabilities:
Derivative Liability	$ 417	$ 431