Loans Receivable - Impaired Loans By Segment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Recorded Investment
Recorded Investment, No Allowance Recorded	$ 1,637		$ 1,833
Recorded Investment, Allowance Recorded	4,666		4,556
Recorded Investment	6,303		6,389
Unpaid Principal Balance
Unpaid Principal Balance, No Allowance Recorded	2,122		2,343
Unpaid Principal Balance, Allowance Recorded	5,050		4,929
Unpaid Principal Balance	7,172		7,272
Related Allowance	109		202
Average Recorded Investment
Average Recorded Investment, No Allowance Recorded	1,480	$ 1,924
Average Recorded Investment, Allowance Recorded	4,852	4,548
Average Recorded Investment	6,332	6,472
Interest Income Recognized
Interest Income Recognized, No Allowance Recorded	29	34
Interest Income Recognized, Allowance Recorded	89	97
Interest Income Recognized	118	131
Real Estate | Real estate loans | One-to-four family
Recorded Investment
Recorded Investment, No Allowance Recorded	72		297
Recorded Investment, Allowance Recorded	2,669		2,691
Recorded Investment	2,741		2,988
Unpaid Principal Balance
Unpaid Principal Balance, No Allowance Recorded	99		332
Unpaid Principal Balance, Allowance Recorded	2,884		2,911
Unpaid Principal Balance	2,983		3,243
Related Allowance	33		31
Average Recorded Investment
Average Recorded Investment, No Allowance Recorded	108	304
Average Recorded Investment, Allowance Recorded	2,676	2,831
Average Recorded Investment	2,784	3,135
Interest Income Recognized
Interest Income Recognized, No Allowance Recorded	1	5
Interest Income Recognized, Allowance Recorded	64	68
Interest Income Recognized	65	73
Real Estate | Real estate loans | Multi-family
Recorded Investment
Recorded Investment, No Allowance Recorded	296		0
Recorded Investment, Allowance Recorded	107		107
Recorded Investment	403		107
Unpaid Principal Balance
Unpaid Principal Balance, No Allowance Recorded	296		0
Unpaid Principal Balance, Allowance Recorded	107		107
Unpaid Principal Balance	403		107
Related Allowance	1		1
Average Recorded Investment
Average Recorded Investment, No Allowance Recorded	99
Average Recorded Investment, Allowance Recorded	305	110
Average Recorded Investment	404	110
Interest Income Recognized
Interest Income Recognized, No Allowance Recorded	0
Interest Income Recognized, Allowance Recorded	0	1
Interest Income Recognized	0	1
Real Estate | Commercial real estate
Recorded Investment
Recorded Investment, No Allowance Recorded	1,227		1,240
Recorded Investment, Allowance Recorded	643		643
Recorded Investment	1,870		1,883
Unpaid Principal Balance
Unpaid Principal Balance, No Allowance Recorded	1,310		1,320
Unpaid Principal Balance, Allowance Recorded	643		643
Unpaid Principal Balance	1,953		1,963
Related Allowance	9		8
Average Recorded Investment
Average Recorded Investment, No Allowance Recorded	1,231	1,296
Average Recorded Investment, Allowance Recorded	643	663
Average Recorded Investment	1,874	1,959
Interest Income Recognized
Interest Income Recognized, No Allowance Recorded	15	12
Interest Income Recognized, Allowance Recorded	0	7
Interest Income Recognized	15	19
Real Estate | Construction and land
Recorded Investment
Recorded Investment, No Allowance Recorded	0		0
Recorded Investment, Allowance Recorded	28		29
Recorded Investment	28		29
Unpaid Principal Balance
Unpaid Principal Balance, No Allowance Recorded	32		33
Unpaid Principal Balance, Allowance Recorded	28		29
Unpaid Principal Balance	60		62
Related Allowance	1		0
Average Recorded Investment
Average Recorded Investment, No Allowance Recorded		0
Average Recorded Investment, Allowance Recorded	28	53
Average Recorded Investment	28	53
Interest Income Recognized
Interest Income Recognized, No Allowance Recorded		0
Interest Income Recognized, Allowance Recorded	2	2
Interest Income Recognized	2	2
Consumer | Home equity
Recorded Investment
Recorded Investment, No Allowance Recorded	42		45
Recorded Investment, Allowance Recorded	247		226
Recorded Investment	289		271
Unpaid Principal Balance
Unpaid Principal Balance, No Allowance Recorded	114		110
Unpaid Principal Balance, Allowance Recorded	307		286
Unpaid Principal Balance	421		396
Related Allowance	6		15
Average Recorded Investment
Average Recorded Investment, No Allowance Recorded	42	324
Average Recorded Investment, Allowance Recorded	248	300
Average Recorded Investment	290	624
Interest Income Recognized
Interest Income Recognized, No Allowance Recorded	3	10
Interest Income Recognized, Allowance Recorded	6	7
Interest Income Recognized	9	17
Consumer | Auto and other consumer
Recorded Investment
Recorded Investment, No Allowance Recorded	0		251
Recorded Investment, Allowance Recorded	709		597
Recorded Investment	709		848
Unpaid Principal Balance
Unpaid Principal Balance, No Allowance Recorded	271		548
Unpaid Principal Balance, Allowance Recorded	818		690
Unpaid Principal Balance	1,089		1,238
Related Allowance	54		142
Average Recorded Investment
Average Recorded Investment, No Allowance Recorded	0	0
Average Recorded Investment, Allowance Recorded	689	263
Average Recorded Investment	689	263
Interest Income Recognized
Interest Income Recognized, No Allowance Recorded	10	7
Interest Income Recognized, Allowance Recorded	17	7
Interest Income Recognized	27	14
Commercial business
Recorded Investment
Recorded Investment, No Allowance Recorded	0		0
Recorded Investment, Allowance Recorded	263		263
Recorded Investment	263		263
Unpaid Principal Balance
Unpaid Principal Balance, No Allowance Recorded	0		0
Unpaid Principal Balance, Allowance Recorded	263		263
Unpaid Principal Balance	263		263
Related Allowance	5		$ 5
Average Recorded Investment
Average Recorded Investment, No Allowance Recorded	0
Average Recorded Investment, Allowance Recorded	263	328
Average Recorded Investment	263	328
Interest Income Recognized
Interest Income Recognized, No Allowance Recorded	0
Interest Income Recognized, Allowance Recorded	0	5
Interest Income Recognized	$ 0	$ 5