Allowance for Loan Losses - Allowance For Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, beginning of period	$ 20,449	$ 19,893	$ 21,461	$ 19,697
Charge-Offs	(100)	(207)	(1,204)	(486)
Recoveries	59	75	151	150
Provision (benefit)	(300)	300	(300)	700
Balance, end of period	20,108	20,061	20,108	20,061
Balance, end of period: Individually evaluated for impairment	73	394	73	394
Balance, end of period: collectively evaluated for impairment	20,035	19,667	20,035	19,667
Commercial
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, beginning of period	5,684	5,701	6,172	5,535
Charge-Offs	(77)	(202)	(1,042)	(464)
Recoveries	54	71	143	144
Provision (benefit)	(35)	252	353	607
Balance, end of period	5,626	5,822	5,626	5,822
Balance, end of period: Individually evaluated for impairment	73	394	73	394
Balance, end of period: collectively evaluated for impairment	5,553	5,428	5,553	5,428
Real estate construction one-to-four family
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, beginning of period	608	549	629	550
Charge-Offs	0	0	0	0
Recoveries	0	0	0	0
Provision (benefit)	(12)	(28)	(33)	(29)
Balance, end of period	596	521	596	521
Balance, end of period: Individually evaluated for impairment	0	0	0	0
Balance, end of period: collectively evaluated for impairment	596	521	596	521
Real estate construction other
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, beginning of period	1,069	1,383	1,566	1,465
Charge-Offs	0	0	0	0
Recoveries	0	0	0	0
Provision (benefit)	17	134	(480)	52
Balance, end of period	1,086	1,517	1,086	1,517
Balance, end of period: Individually evaluated for impairment	0	0	0	0
Balance, end of period: collectively evaluated for impairment	1,086	1,517	1,086	1,517
Real estate term owner occupied
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, beginning of period	2,174	2,372	2,194	2,358
Charge-Offs	0	0	0	0
Recoveries	0	0	0	0
Provision (benefit)	(4)	(18)	(24)	(4)
Balance, end of period	2,170	2,354	2,170	2,354
Balance, end of period: Individually evaluated for impairment	0	0	0	0
Balance, end of period: collectively evaluated for impairment	2,170	2,354	2,170	2,354
Real estate term non-owner occupied
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, beginning of period	6,379	7,207	6,043	6,853
Charge-Offs	0	(5)	0	0
Recoveries	0	0	0	0
Provision (benefit)	(160)	(127)	176	222
Balance, end of period	6,219	7,075	6,219	7,075
Balance, end of period: Individually evaluated for impairment	0	0	0	0
Balance, end of period: collectively evaluated for impairment	6,219	7,075	6,219	7,075
Real estate term other
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, beginning of period	1,025	774	725	819
Charge-Offs	0	0	0	(5)
Recoveries	1	0	2	0
Provision (benefit)	(25)	0	274	(40)
Balance, end of period	1,001	774	1,001	774
Balance, end of period: Individually evaluated for impairment	0	0	0	0
Balance, end of period: collectively evaluated for impairment	1,001	774	1,001	774
Consumer secured by 1st deeds of trust
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, beginning of period	305	311	315	313
Charge-Offs	(2)	0	(91)	0
Recoveries	0	2	1	2
Provision (benefit)	49	14	127	12
Balance, end of period	352	327	352	327
Balance, end of period: Individually evaluated for impairment	0	0	0	0
Balance, end of period: collectively evaluated for impairment	352	327	352	327
Consumer other
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, beginning of period	315	391	307	408
Charge-Offs	(21)	0	(71)	(17)
Recoveries	4	2	5	4
Provision (benefit)	98	(31)	155	(33)
Balance, end of period	396	362	396	362
Balance, end of period: Individually evaluated for impairment	0	0	0	0
Balance, end of period: collectively evaluated for impairment	396	362	396	362
Unallocated
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, beginning of period	2,890	1,205	3,510	1,396
Charge-Offs	0	0	0	0
Recoveries	0	0	0	0
Provision (benefit)	(228)	104	(848)	(87)
Balance, end of period	2,662	1,309	2,662	1,309
Balance, end of period: Individually evaluated for impairment	0	0	0	0
Balance, end of period: collectively evaluated for impairment	$ 2,662	$ 1,309	$ 2,662	$ 1,309