Loans Receivable and Allowance for Loan Losses - Impaired Financing Receivables (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Impaired Loans, Recorded Investment
Recorded Investment, With related allowance	$ 38,199		$ 38,199		$ 36,047
Recorded Investment, With no related allowance	67,771		67,771		67,960
Related Allowance	5,933		5,933		4,791
Impaired Loans, net of allowance	100,037		100,037		99,216
Total recorded investment	105,970		105,970		104,007
Impaired Loans, Unpaid Principal Balance
Unpaid Contractual Principal Balance, With related allowance	44,697		44,697		39,560
Unpaid Contractual Principal Balance, With no related allowance	91,642		91,642		93,141
Impaired Financing Receivable, Unpaid Principal Balance	136,339		136,339		132,701
Impaired Loans, Average Recorded Investment
Average Recorded Investment, With related allowance	41,137	$ 53,642	39,430	$ 46,314
Average Recorded Investment, With no related allowance	77,954	69,272	74,623	69,230
Average Recorded Investment, Total	119,091	122,914	114,053	115,544
Impaired Loans, Interest Income Recognized during Impairment
Interest Income Recognized during Impairment, With related allowance	243	343	492	662
Interest Income Recognized during Impairment, With no related allowance	350	338	697	669
Interest Income Recognized during Impairment, Total	593	681	$ 1,189	1,331
Threshold period for loans to be placed on nonaccrual status			90 days
Acquired Loans
Impaired Loans, Recorded Investment
Recorded Investment, With related allowance	3,718		$ 3,718		8,474
Recorded Investment, With no related allowance	24,217		24,217		19,605
Related Allowance	1,115		1,115		391
Total recorded investment	27,935		27,935		28,079
Impaired Loans, Unpaid Principal Balance
Unpaid Contractual Principal Balance, With related allowance	7,797		7,797		10,566
Unpaid Contractual Principal Balance, With no related allowance	31,401		31,401		26,593
Impaired Financing Receivable, Unpaid Principal Balance	39,198		39,198		37,159
Impaired Loans, Average Recorded Investment
Average Recorded Investment, With related allowance	5,050	15,802	6,676	11,538
Average Recorded Investment, With no related allowance	25,384	22,495	23,462	21,855
Average Recorded Investment, Total	30,434	38,297	30,138	33,393
Impaired Loans, Interest Income Recognized during Impairment
Interest Income Recognized during Impairment, With related allowance	26	101	52	195
Interest Income Recognized during Impairment, With no related allowance	180	162	359	306
Interest Income Recognized during Impairment, Total	206	263	411	501
Real estate \| Residential
Impaired Loans, Recorded Investment
Recorded Investment, With related allowance	0		0		0
Recorded Investment, With no related allowance	0		0		0
Related Allowance	0		0		0
Impaired Loans, Unpaid Principal Balance
Unpaid Contractual Principal Balance, With related allowance	0		0		0
Unpaid Contractual Principal Balance, With no related allowance	0		0		0
Impaired Loans, Average Recorded Investment
Average Recorded Investment, With related allowance	0	125	0	84
Average Recorded Investment, With no related allowance	0	0	0	0
Impaired Loans, Interest Income Recognized during Impairment
Interest Income Recognized during Impairment, With related allowance	0	0	0	0
Interest Income Recognized during Impairment, With no related allowance	0	0	0	0
Real estate \| Residential \| Acquired Loans
Impaired Loans, Recorded Investment
Recorded Investment, With related allowance	0		0		0
Recorded Investment, With no related allowance	0		0		0
Related Allowance	0		0		0
Impaired Loans, Unpaid Principal Balance
Unpaid Contractual Principal Balance, With related allowance	0		0		0
Unpaid Contractual Principal Balance, With no related allowance	0		0		0
Impaired Loans, Average Recorded Investment
Average Recorded Investment, With related allowance	0	125	0	84
Average Recorded Investment, With no related allowance	0	0	0	0
Impaired Loans, Interest Income Recognized during Impairment
Interest Income Recognized during Impairment, With related allowance	0	0	0	0
Interest Income Recognized during Impairment, With no related allowance	0	0	0	0
Real estate \| Commercial
Impaired Loans, Recorded Investment
Related Allowance	319		319		437
Real estate \| Commercial \| Retail
Impaired Loans, Recorded Investment
Recorded Investment, With related allowance	2,222		2,222		1,375
Recorded Investment, With no related allowance	11,035		11,035		8,005
Related Allowance	63		63		156
Impaired Loans, Unpaid Principal Balance
Unpaid Contractual Principal Balance, With related allowance	2,492		2,492		1,487
Unpaid Contractual Principal Balance, With no related allowance	11,865		11,865		11,234
Impaired Loans, Average Recorded Investment
Average Recorded Investment, With related allowance	2,133	7,088	1,880	4,902
Average Recorded Investment, With no related allowance	17,808	10,917	14,540	11,209
Impaired Loans, Interest Income Recognized during Impairment
Interest Income Recognized during Impairment, With related allowance	6	7	11	15
Interest Income Recognized during Impairment, With no related allowance	35	36	70	71
Real estate \| Commercial \| Retail \| Acquired Loans
Impaired Loans, Recorded Investment
Recorded Investment, With related allowance	810		810		198
Recorded Investment, With no related allowance	7,155		7,155		3,285
Related Allowance	22		22		118
Impaired Loans, Unpaid Principal Balance
Unpaid Contractual Principal Balance, With related allowance	843		843		220
Unpaid Contractual Principal Balance, With no related allowance	7,246		7,246		4,151
Impaired Loans, Average Recorded Investment
Average Recorded Investment, With related allowance	692	800	527	621
Average Recorded Investment, With no related allowance	7,344	3,108	5,991	3,209
Impaired Loans, Interest Income Recognized during Impairment
Interest Income Recognized during Impairment, With related allowance	0	0	0	0
Interest Income Recognized during Impairment, With no related allowance	30	31	60	61
Real estate \| Commercial \| Hotel & motel
Impaired Loans, Recorded Investment
Recorded Investment, With related allowance	1,789		1,789		1,949
Recorded Investment, With no related allowance	10,136		10,136		10,877
Related Allowance	103		103		119
Impaired Loans, Unpaid Principal Balance
Unpaid Contractual Principal Balance, With related allowance	2,658		2,658		2,310
Unpaid Contractual Principal Balance, With no related allowance	20,811		20,811		22,590
Impaired Loans, Average Recorded Investment
Average Recorded Investment, With related allowance	1,812	2,792	1,857	2,838
Average Recorded Investment, With no related allowance	9,946	3,713	10,256	3,423
Impaired Loans, Interest Income Recognized during Impairment
Interest Income Recognized during Impairment, With related allowance	0	0	0	0
Interest Income Recognized during Impairment, With no related allowance	0	0	0	0
Real estate \| Commercial \| Hotel & motel \| Acquired Loans
Impaired Loans, Recorded Investment
Recorded Investment, With related allowance	73		73		72
Recorded Investment, With no related allowance	5,350		5,350		5,428
Related Allowance	3		3		4
Impaired Loans, Unpaid Principal Balance
Unpaid Contractual Principal Balance, With related allowance	345		345		345
Unpaid Contractual Principal Balance, With no related allowance	6,790		6,790		6,874
Impaired Loans, Average Recorded Investment
Average Recorded Investment, With related allowance	73	79	73	81
Average Recorded Investment, With no related allowance	5,371	1,029	5,390	847
Impaired Loans, Interest Income Recognized during Impairment
Interest Income Recognized during Impairment, With related allowance	0	0	0	0
Interest Income Recognized during Impairment, With no related allowance	0	0	0	0
Real estate \| Commercial \| Gas station & car wash
Impaired Loans, Recorded Investment
Recorded Investment, With related allowance	61		61		0
Recorded Investment, With no related allowance	456		456		545
Related Allowance	0		0		0
Impaired Loans, Unpaid Principal Balance
Unpaid Contractual Principal Balance, With related allowance	1,967		1,967		0
Unpaid Contractual Principal Balance, With no related allowance	1,660		1,660		3,653
Impaired Loans, Average Recorded Investment
Average Recorded Investment, With related allowance	61	0	31	0
Average Recorded Investment, With no related allowance	494	542	511	558
Impaired Loans, Interest Income Recognized during Impairment
Interest Income Recognized during Impairment, With related allowance	0	0	0	0
Interest Income Recognized during Impairment, With no related allowance	4	0	9	0
Real estate \| Commercial \| Gas station & car wash \| Acquired Loans
Impaired Loans, Recorded Investment
Recorded Investment, With related allowance	61		61		0
Recorded Investment, With no related allowance	183		183		247
Related Allowance	0		0		0
Impaired Loans, Unpaid Principal Balance
Unpaid Contractual Principal Balance, With related allowance	1,967		1,967		0
Unpaid Contractual Principal Balance, With no related allowance	706		706		2,673
Impaired Loans, Average Recorded Investment
Average Recorded Investment, With related allowance	30	0	20	0
Average Recorded Investment, With no related allowance	215	193	225	129
Impaired Loans, Interest Income Recognized during Impairment
Interest Income Recognized during Impairment, With related allowance	0	0	0	0
Interest Income Recognized during Impairment, With no related allowance	0	0	0	0
Real estate \| Commercial \| Mixed use
Impaired Loans, Recorded Investment
Recorded Investment, With related allowance	836		836		881
Recorded Investment, With no related allowance	3,473		3,473		7,048
Related Allowance	25		25		43
Impaired Loans, Unpaid Principal Balance
Unpaid Contractual Principal Balance, With related allowance	924		924		947
Unpaid Contractual Principal Balance, With no related allowance	3,576		3,576		7,058
Impaired Loans, Average Recorded Investment
Average Recorded Investment, With related allowance	847	2,985	859	2,094
Average Recorded Investment, With no related allowance	5,345	2,475	5,912	2,017
Impaired Loans, Interest Income Recognized during Impairment
Interest Income Recognized during Impairment, With related allowance	2	39	3	75
Interest Income Recognized during Impairment, With no related allowance	51	50	102	100
Real estate \| Commercial \| Mixed use \| Acquired Loans
Impaired Loans, Recorded Investment
Recorded Investment, With related allowance	293		293		312
Recorded Investment, With no related allowance	194		194		3,722
Related Allowance	22		22		38
Impaired Loans, Unpaid Principal Balance
Unpaid Contractual Principal Balance, With related allowance	297		297		312
Unpaid Contractual Principal Balance, With no related allowance	285		285		3,726
Impaired Loans, Average Recorded Investment
Average Recorded Investment, With related allowance	298	2,899	303	1,976
Average Recorded Investment, With no related allowance	2,049	36	2,607	74
Impaired Loans, Interest Income Recognized during Impairment
Interest Income Recognized during Impairment, With related allowance	2	39	3	75
Interest Income Recognized during Impairment, With no related allowance	0	0	0	0
Real estate \| Commercial \| Industrial & warehouse
Impaired Loans, Recorded Investment
Recorded Investment, With related allowance	6,908		6,908		1,305
Recorded Investment, With no related allowance	11,944		11,944		12,343
Related Allowance	121		121		93
Impaired Loans, Unpaid Principal Balance
Unpaid Contractual Principal Balance, With related allowance	8,671		8,671		2,139
Unpaid Contractual Principal Balance, With no related allowance	12,531		12,531		13,467
Impaired Loans, Average Recorded Investment
Average Recorded Investment, With related allowance	7,249	2,616	5,267	2,002
Average Recorded Investment, With no related allowance	10,998	11,886	11,447	10,733
Impaired Loans, Interest Income Recognized during Impairment
Interest Income Recognized during Impairment, With related allowance	90	36	170	67
Interest Income Recognized during Impairment, With no related allowance	64	56	127	112
Real estate \| Commercial \| Industrial & warehouse \| Acquired Loans
Impaired Loans, Recorded Investment
Recorded Investment, With related allowance	328		328		230
Recorded Investment, With no related allowance	0		0		119
Related Allowance	80		80		88
Impaired Loans, Unpaid Principal Balance
Unpaid Contractual Principal Balance, With related allowance	1,920		1,920		1,050
Unpaid Contractual Principal Balance, With no related allowance	0		0		894
Impaired Loans, Average Recorded Investment
Average Recorded Investment, With related allowance	282	266	264	251
Average Recorded Investment, With no related allowance	93	491	106	342
Impaired Loans, Interest Income Recognized during Impairment
Interest Income Recognized during Impairment, With related allowance	0	0	0	1
Interest Income Recognized during Impairment, With no related allowance	0	0	0	0
Real estate \| Commercial \| Other
Impaired Loans, Recorded Investment
Recorded Investment, With related allowance	839		839		7,759
Recorded Investment, With no related allowance	16,664		16,664		5,969
Related Allowance	7		7		26
Impaired Loans, Unpaid Principal Balance
Unpaid Contractual Principal Balance, With related allowance	1,103		1,103		8,174
Unpaid Contractual Principal Balance, With no related allowance	21,123		21,123		7,122
Impaired Loans, Average Recorded Investment
Average Recorded Investment, With related allowance	2,597	6,655	4,318	5,902
Average Recorded Investment, With no related allowance	15,524	13,587	12,339	15,819
Impaired Loans, Interest Income Recognized during Impairment
Interest Income Recognized during Impairment, With related allowance	5	24	11	47
Interest Income Recognized during Impairment, With no related allowance	82	112	166	233
Real estate \| Commercial \| Other \| Acquired Loans
Impaired Loans, Recorded Investment
Recorded Investment, With related allowance	0		0		3,454
Recorded Investment, With no related allowance	5,131		5,131		1,013
Related Allowance	0		0		13
Impaired Loans, Unpaid Principal Balance
Unpaid Contractual Principal Balance, With related allowance	0		0		3,454
Unpaid Contractual Principal Balance, With no related allowance	8,448		8,448		1,326
Impaired Loans, Average Recorded Investment
Average Recorded Investment, With related allowance	544	3,314	1,999	2,316
Average Recorded Investment, With no related allowance	4,749	4,475	3,504	6,027
Impaired Loans, Interest Income Recognized during Impairment
Interest Income Recognized during Impairment, With related allowance	0	19	0	37
Interest Income Recognized during Impairment, With no related allowance	67	60	133	117
Real estate \| Construction
Impaired Loans, Recorded Investment
Recorded Investment, With related allowance	0		0		0
Recorded Investment, With no related allowance	0		0		0
Related Allowance	0		0		0
Impaired Loans, Unpaid Principal Balance
Unpaid Contractual Principal Balance, With related allowance	0		0		0
Unpaid Contractual Principal Balance, With no related allowance	0		0		0
Impaired Loans, Average Recorded Investment
Average Recorded Investment, With related allowance	0	0	0	0
Average Recorded Investment, With no related allowance	0	650	0	867
Impaired Loans, Interest Income Recognized during Impairment
Interest Income Recognized during Impairment, With related allowance	0	0	0	0
Interest Income Recognized during Impairment, With no related allowance	0	0	0	0
Real estate \| Construction \| Acquired Loans
Impaired Loans, Recorded Investment
Recorded Investment, With related allowance	0		0		0
Recorded Investment, With no related allowance	0		0		0
Related Allowance	0		0		0
Impaired Loans, Unpaid Principal Balance
Unpaid Contractual Principal Balance, With related allowance	0		0		0
Unpaid Contractual Principal Balance, With no related allowance	0		0		0
Impaired Loans, Average Recorded Investment
Average Recorded Investment, With related allowance	0	0	0	0
Average Recorded Investment, With no related allowance	0	0	0	0
Impaired Loans, Interest Income Recognized during Impairment
Interest Income Recognized during Impairment, With related allowance	0	0	0	0
Interest Income Recognized during Impairment, With no related allowance	0	0	0	0
Commercial business
Impaired Loans, Recorded Investment
Recorded Investment, With related allowance	21,761		21,761		22,203
Recorded Investment, With no related allowance	8,626		8,626		13,155
Related Allowance	5,269		5,269		4,351
Impaired Loans, Unpaid Principal Balance
Unpaid Contractual Principal Balance, With related allowance	23,091		23,091		23,928
Unpaid Contractual Principal Balance, With no related allowance	14,554		14,554		17,850
Impaired Loans, Average Recorded Investment
Average Recorded Investment, With related allowance	24,019	27,487	23,414	24,435
Average Recorded Investment, With no related allowance	10,576	20,530	11,436	19,752
Impaired Loans, Interest Income Recognized during Impairment
Interest Income Recognized during Impairment, With related allowance	139	168	295	331
Interest Income Recognized during Impairment, With no related allowance	62	37	121	63
Commercial business \| Acquired Loans
Impaired Loans, Recorded Investment
Recorded Investment, With related allowance	2,022		2,022		4,064
Recorded Investment, With no related allowance	2,206		2,206		1,670
Related Allowance	987		987		130
Impaired Loans, Unpaid Principal Balance
Unpaid Contractual Principal Balance, With related allowance	2,294		2,294		5,041
Unpaid Contractual Principal Balance, With no related allowance	3,843		3,843		2,681
Impaired Loans, Average Recorded Investment
Average Recorded Investment, With related allowance	2,998	8,243	3,353	6,158
Average Recorded Investment, With no related allowance	1,640	8,380	1,650	6,660
Impaired Loans, Interest Income Recognized during Impairment
Interest Income Recognized during Impairment, With related allowance	24	41	49	80
Interest Income Recognized during Impairment, With no related allowance	31	24	64	38
Trade finance
Impaired Loans, Recorded Investment
Recorded Investment, With related allowance	2,825		2,825		0
Recorded Investment, With no related allowance	3,318		3,318		9,011
Related Allowance	333		333		0
Impaired Loans, Unpaid Principal Balance
Unpaid Contractual Principal Balance, With related allowance	2,825		2,825		0
Unpaid Contractual Principal Balance, With no related allowance	3,318		3,318		9,011
Impaired Loans, Average Recorded Investment
Average Recorded Investment, With related allowance	1,463	3,146	975	3,384
Average Recorded Investment, With no related allowance	5,813	3,165	6,879	3,134
Impaired Loans, Interest Income Recognized during Impairment
Interest Income Recognized during Impairment, With related allowance	1	63	2	121
Interest Income Recognized during Impairment, With no related allowance	52	47	102	90
Trade finance \| Acquired Loans
Impaired Loans, Recorded Investment
Recorded Investment, With related allowance	0		0		0
Recorded Investment, With no related allowance	3,318		3,318		3,124
Related Allowance	0		0		0
Impaired Loans, Unpaid Principal Balance
Unpaid Contractual Principal Balance, With related allowance	0		0		0
Unpaid Contractual Principal Balance, With no related allowance	3,318		3,318		3,124
Impaired Loans, Average Recorded Investment
Average Recorded Investment, With related allowance	0	0	0	0
Average Recorded Investment, With no related allowance	3,192	3,165	3,169	3,104
Impaired Loans, Interest Income Recognized during Impairment
Interest Income Recognized during Impairment, With related allowance	0	0	0	0
Interest Income Recognized during Impairment, With no related allowance	52	47	102	90
Consumer and other
Impaired Loans, Recorded Investment
Recorded Investment, With related allowance	958		958		575
Recorded Investment, With no related allowance	2,119		2,119		1,007
Related Allowance	12		12		3
Impaired Loans, Unpaid Principal Balance
Unpaid Contractual Principal Balance, With related allowance	966		966		575
Unpaid Contractual Principal Balance, With no related allowance	2,204		2,204		1,156
Impaired Loans, Average Recorded Investment
Average Recorded Investment, With related allowance	956	748	829	673
Average Recorded Investment, With no related allowance	1,450	1,807	1,303	1,718
Impaired Loans, Interest Income Recognized during Impairment
Interest Income Recognized during Impairment, With related allowance	0	6	0	6
Interest Income Recognized during Impairment, With no related allowance	0	0	0	0
Consumer and other \| Acquired Loans
Impaired Loans, Recorded Investment
Recorded Investment, With related allowance	131		131		144
Recorded Investment, With no related allowance	680		680		997
Related Allowance	1		1		0
Impaired Loans, Unpaid Principal Balance
Unpaid Contractual Principal Balance, With related allowance	131		131		144
Unpaid Contractual Principal Balance, With no related allowance	765		765		1,144
Impaired Loans, Average Recorded Investment
Average Recorded Investment, With related allowance	133	76	137	51
Average Recorded Investment, With no related allowance	731	1,618	820	1,463
Impaired Loans, Interest Income Recognized during Impairment
Interest Income Recognized during Impairment, With related allowance	0	2	0	2
Interest Income Recognized during Impairment, With no related allowance	0	$ 0	0	$ 0
WIthout charge-offs
Impaired Loans, Recorded Investment
Recorded Investment, With related allowance	36,966		36,966		35,365
Recorded Investment, With no related allowance	57,249		57,249		59,607
With charge-offs
Impaired Loans, Recorded Investment
Recorded Investment, With related allowance	1,233		1,233		681
Recorded Investment, With no related allowance	$ 10,522		$ 10,522		$ 8,354

Loans Receivable and Allowance for Loan Losses - Impaired Financing Receivables (Details) - USD ($)
$ in Thousands

3 Months Ended

6 Months Ended

Jun. 30, 2019

Jun. 30, 2018

Jun. 30, 2019

Jun. 30, 2018

Dec. 31, 2018

Impaired Loans, Recorded Investment

Recorded Investment, With related allowance

$ 38,199

$ 36,047