Loans Receivable - Allowance for Loan Losses (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
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	$ 11,347	$ 10,157	$ 11,308	$ 10,033
Provision for loan losses	677	630	798	1,145
Charge-Offs	(118)	(405)	(211)	(827)
Recoveries	7	65	18	96
Balance at end of year	11,913	10,447	11,913	10,447
Allowance for Loan Losses Ending Balance Evaluated for Impairment - Individually	377		377		$ 262
Allowance for Loan Losses Ending Balance Evaluated for Impairment - Collectively	11,536		11,536		11,046
Outstanding Loan Balances Evaluated for Impairment - Individually	6,797		6,797		4,355
Outstanding Loan Balances Evaluated for Impairment - Collectively	1,052,798		1,052,798		997,905
Consumer \| Other consumer
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	9	8	9	8
Provision for loan losses	(2)	1	(2)	1
Charge-Offs	0	0	0	0
Recoveries	0	0	0	0
Balance at end of year	7	9	7	9
Allowance for Loan Losses Ending Balance Evaluated for Impairment - Individually	0		0		0
Allowance for Loan Losses Ending Balance Evaluated for Impairment - Collectively	7		7		9
Outstanding Loan Balances Evaluated for Impairment - Individually	0		0		0
Outstanding Loan Balances Evaluated for Impairment - Collectively	1,015		1,015		1,202
Consumer \| Credit card
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	992	823	1,084	885
Provision for loan losses	295	367	287	685
Charge-Offs	(90)	(252)	(183)	(658)
Recoveries	2	60	11	86
Balance at end of year	1,199	998	1,199	998
Allowance for Loan Losses Ending Balance Evaluated for Impairment - Individually	0		0		0
Allowance for Loan Losses Ending Balance Evaluated for Impairment - Collectively	1,199		1,199		1,084
Outstanding Loan Balances Evaluated for Impairment - Individually	0		0		0
Outstanding Loan Balances Evaluated for Impairment - Collectively	40,141		40,141		34,673
Construction \| Real estate
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	2,062	1,804	2,093	1,646
Provision for loan losses	142	85	111	243
Charge-Offs	0	0	0	0
Recoveries	0	0	0	0
Balance at end of year	2,204	1,889	2,204	1,889
Allowance for Loan Losses Ending Balance Evaluated for Impairment - Individually	43		43		0
Allowance for Loan Losses Ending Balance Evaluated for Impairment - Collectively	2,161		2,161		2,093
Outstanding Loan Balances Evaluated for Impairment - Individually	2,143		2,143		0
Outstanding Loan Balances Evaluated for Impairment - Collectively	167,082		167,082		157,586
Commercial
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	1,451	1,414	1,578	1,497
Provision for loan losses	49	113	(78)	45
Charge-Offs	(28)	(131)	(28)	(147)
Recoveries	0	0	0	1
Balance at end of year	1,472	1,396	1,472	1,396
Allowance for Loan Losses Ending Balance Evaluated for Impairment - Individually	334		334		262
Allowance for Loan Losses Ending Balance Evaluated for Impairment - Collectively	1,138		1,138		1,316
Outstanding Loan Balances Evaluated for Impairment - Individually	1,002		1,002		749
Outstanding Loan Balances Evaluated for Impairment - Collectively	123,434		123,434		121,515
Commercial \| Real estate
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	2,894	2,933	3,003	2,860
Provision for loan losses	217	33	106	103
Charge-Offs	0	(22)	0	(22)
Recoveries	5	4	7	7
Balance at end of year	3,116	2,948	3,116	2,948
Allowance for Loan Losses Ending Balance Evaluated for Impairment - Individually	0		0		0
Allowance for Loan Losses Ending Balance Evaluated for Impairment - Collectively	3,116		3,116		3,003
Outstanding Loan Balances Evaluated for Impairment - Individually	1,465		1,465		1,486
Outstanding Loan Balances Evaluated for Impairment - Collectively	296,426		296,426		277,205
Residential \| Real estate
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	3,939	3,175	3,541	3,137
Provision for loan losses	(24)	31	374	68
Charge-Offs	0	0	0	0
Recoveries	0	1	0	2
Balance at end of year	3,915	$ 3,207	3,915	$ 3,207
Allowance for Loan Losses Ending Balance Evaluated for Impairment - Individually	0		0		0
Allowance for Loan Losses Ending Balance Evaluated for Impairment - Collectively	3,915		3,915		3,541
Outstanding Loan Balances Evaluated for Impairment - Individually	2,187		2,187		2,120
Outstanding Loan Balances Evaluated for Impairment - Collectively	$ 424,700		$ 424,700		$ 405,724

Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

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The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

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Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

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The balance of financing receivables that were collectively evaluated for impairment.

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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Amount of expense related to estimated loss from loan and lease transactions.

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