Loans Receivable and Allowance For Loan Losses - Financing Receivables, Related Allowance Recorded and No Related Allowance Recorder (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Unpaid Principal Balance, with no related allowance recorded	$ 2,563		$ 2,685
Unpaid Principal Balance, with related allowance recorded	720		537
Impaired Financing Receivable, Unpaid Principal Balance, Total	3,283		3,222
Impaired Financing Receivable, Recorded Investment [Abstract]
Recorded Investment, with no related allowance recorded	2,473		2,592
Recorded Investment, with related allowance recorded	719		536
Recorded Investment	3,192		3,128
Impaired Financing Receivable Related Allowance Abstract
Related Allowance, with no related allowance recorded	0		0
Related Allowance, with related allowance recorded	246		182
Related Allowance	246		182
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Average Recorded Investment, with no related allowance recorded	2,539	$ 1,528
Average Recorded Investment, with related allowance recorded	650	2,767
Impaired Financing Receivable, Average Recorded Investment	3,189	4,295
Impaired Financing Receivable, Interest Income [Abstract]
Interest Income Recognized, with no related allowance recorded	13	15
Interest Income Recognized, with related allowance recorded	13	16
Interest Income Recognized	26	31
Commercial
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Unpaid Principal Balance, with no related allowance recorded	1,094		1,097
Impaired Financing Receivable, Recorded Investment [Abstract]
Recorded Investment, with no related allowance recorded	1,083		1,086
Impaired Financing Receivable Related Allowance Abstract
Related Allowance, with no related allowance recorded	0		0
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Average Recorded Investment, with no related allowance recorded	1,084	0
Impaired Financing Receivable, Interest Income [Abstract]
Interest Income Recognized, with no related allowance recorded	8	0
Home equity.
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Unpaid Principal Balance, with no related allowance recorded	271		278
Impaired Financing Receivable, Recorded Investment [Abstract]
Recorded Investment, with no related allowance recorded	220		225
Impaired Financing Receivable Related Allowance Abstract
Related Allowance, with no related allowance recorded	0		0
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Average Recorded Investment, with no related allowance recorded	220	267
Impaired Financing Receivable, Interest Income [Abstract]
Interest Income Recognized, with no related allowance recorded	0	0
One-to-four-family
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Unpaid Principal Balance, with no related allowance recorded	1,193		1,293
Unpaid Principal Balance, with related allowance recorded	61		61
Impaired Financing Receivable, Recorded Investment [Abstract]
Recorded Investment, with no related allowance recorded	1,165		1,264
Recorded Investment, with related allowance recorded	60		60
Impaired Financing Receivable Related Allowance Abstract
Related Allowance, with no related allowance recorded	0		0
Related Allowance, with related allowance recorded	15		15
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Average Recorded Investment, with no related allowance recorded	1,230	830
Average Recorded Investment, with related allowance recorded	60	1,156
Impaired Financing Receivable, Interest Income [Abstract]
Interest Income Recognized, with no related allowance recorded	5	15
Interest Income Recognized, with related allowance recorded	0	0
Indirect home improvement
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Unpaid Principal Balance, with related allowance recorded	533		468
Impaired Financing Receivable, Recorded Investment [Abstract]
Recorded Investment, with related allowance recorded	533		468
Impaired Financing Receivable Related Allowance Abstract
Related Allowance, with related allowance recorded	187		164
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Average Recorded Investment, with related allowance recorded	548	441
Impaired Financing Receivable, Interest Income [Abstract]
Interest Income Recognized, with related allowance recorded	13	9
Marine
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Unpaid Principal Balance, with related allowance recorded	124
Impaired Financing Receivable, Recorded Investment [Abstract]
Recorded Investment, with related allowance recorded	124
Impaired Financing Receivable Related Allowance Abstract
Related Allowance, with related allowance recorded	43
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Average Recorded Investment, with related allowance recorded	41	13
Impaired Financing Receivable, Interest Income [Abstract]
Interest Income Recognized, with related allowance recorded	0	0
Other consumer loans
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Unpaid Principal Balance, with no related allowance recorded	5		17
Unpaid Principal Balance, with related allowance recorded	2		8
Impaired Financing Receivable, Recorded Investment [Abstract]
Recorded Investment, with no related allowance recorded	5		17
Recorded Investment, with related allowance recorded	2		8
Impaired Financing Receivable Related Allowance Abstract
Related Allowance, with no related allowance recorded	0		0
Related Allowance, with related allowance recorded	1		$ 3
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Average Recorded Investment, with no related allowance recorded	5	0
Average Recorded Investment, with related allowance recorded	1	5
Impaired Financing Receivable, Interest Income [Abstract]
Interest Income Recognized, with no related allowance recorded	0	0
Interest Income Recognized, with related allowance recorded	0	0
Commercial and industrial
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Average Recorded Investment, with no related allowance recorded	0	431
Average Recorded Investment, with related allowance recorded	0	1,152
Impaired Financing Receivable, Interest Income [Abstract]
Interest Income Recognized, with no related allowance recorded	0	0
Interest Income Recognized, with related allowance recorded	$ 0	$ 7

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-Publisher FASB
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-Topic 310
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