Allowance for Loan Losses - Allowance For Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, beginning of period	$ 20,108	$ 20,061	$ 21,461	$ 19,697
Charge-Offs	(9)	(1,203)	(1,213)	(1,689)
Recoveries	61	106	212	256
Provision (benefit)	0	2,500	(300)	3,200
Balance, end of period	20,160	21,464	20,160	21,464
Balance, end of period: Individually evaluated for impairment	372	1,514	372	1,514
Balance, end of period: collectively evaluated for impairment	19,788	19,950	19,788	19,950
Commercial
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, beginning of period	5,626	5,822	6,172	5,535
Charge-Offs	0	(1,118)	(1,042)	(1,582)
Recoveries	57	102	200	246
Provision (benefit)	254	2,210	607	2,817
Balance, end of period	5,937	7,016	5,937	7,016
Balance, end of period: Individually evaluated for impairment	323	1,514	323	1,514
Balance, end of period: collectively evaluated for impairment	5,614	5,502	5,614	5,502
Real estate construction one-to-four family
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, beginning of period	596	521	629	550
Charge-Offs	0	0	0	0
Recoveries	0	0	0	0
Provision (benefit)	79	79	46	50
Balance, end of period	675	600	675	600
Balance, end of period: Individually evaluated for impairment	0	0	0	0
Balance, end of period: collectively evaluated for impairment	675	600	675	600
Real estate construction other
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, beginning of period	1,086	1,517	1,566	1,465
Charge-Offs	0	0	0	0
Recoveries	0	0	0	0
Provision (benefit)	34	261	(446)	313
Balance, end of period	1,120	1,778	1,120	1,778
Balance, end of period: Individually evaluated for impairment	0	0	0	0
Balance, end of period: collectively evaluated for impairment	1,120	1,778	1,120	1,778
Real estate term owner occupied
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, beginning of period	2,170	2,354	2,194	2,358
Charge-Offs	0	0	0	0
Recoveries	0	0	0	0
Provision (benefit)	(43)	(10)	(67)	(14)
Balance, end of period	2,127	2,344	2,127	2,344
Balance, end of period: Individually evaluated for impairment	0	0	0	0
Balance, end of period: collectively evaluated for impairment	2,127	2,344	2,127	2,344
Real estate term non-owner occupied
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, beginning of period	6,219	7,075	6,043	6,853
Charge-Offs	0	0	0	0
Recoveries	0	0	0	0
Provision (benefit)	(11)	(60)	165	162
Balance, end of period	6,208	7,015	6,208	7,015
Balance, end of period: Individually evaluated for impairment	0	0	0	0
Balance, end of period: collectively evaluated for impairment	6,208	7,015	6,208	7,015
Real estate term other
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, beginning of period	1,001	774	725	819
Charge-Offs	0	0	0	(5)
Recoveries	1	0	3	0
Provision (benefit)	(291)	10	(17)	(30)
Balance, end of period	711	784	711	784
Balance, end of period: Individually evaluated for impairment	0	0	0	0
Balance, end of period: collectively evaluated for impairment	711	784	711	784
Consumer secured by 1st deeds of trust
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, beginning of period	352	327	315	313
Charge-Offs	0	(85)	(91)	(85)
Recoveries	1	0	2	2
Provision (benefit)	21	93	148	105
Balance, end of period	374	335	374	335
Balance, end of period: Individually evaluated for impairment	49	0	49	0
Balance, end of period: collectively evaluated for impairment	325	335	325	335
Consumer other
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, beginning of period	396	362	307	408
Charge-Offs	(9)	0	(80)	(17)
Recoveries	2	4	7	8
Provision (benefit)	27	(2)	182	(35)
Balance, end of period	416	364	416	364
Balance, end of period: Individually evaluated for impairment	0	0	0	0
Balance, end of period: collectively evaluated for impairment	416	364	416	364
Unallocated
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, beginning of period	2,662	1,309	3,510	1,396
Charge-Offs	0	0	0	0
Recoveries	0	0	0	0
Provision (benefit)	(70)	(81)	(918)	(168)
Balance, end of period	2,592	1,228	2,592	1,228
Balance, end of period: Individually evaluated for impairment	0	0	0	0
Balance, end of period: collectively evaluated for impairment	$ 2,592	$ 1,228	$ 2,592	$ 1,228