Loans Receivable, Part IV (Details) - USD ($) | 9 Months Ended | |
Sep. 30, 2020 | Sep. 30, 2019 | Dec. 31, 2019 |
Loans and Leases Receivable [Abstract] | | | |
At December 31, 2016 | $ 1,434,132,000 | | $ 1,388,031,000 |
Loans requiring an officers' loans committee review and approval, minimum | 500,000 | | |
Minimum amount of potential loan exposure to be reviewed by credit management personnel | $ 1,000,000 | | |
Maximum period of time loan is reviewed if renewed | 1 year | | |
Period of time sales of real estate owned fair value is based | 2 years | | |
Impaired Loans Receivable, Recorded Investment [Abstract] | | | |
Total Impaired, with Reserve, Recorded Investment | $ 210,000 | | 224,000 |
Total Impaired, with no Reserve, Recorded Investment | 14,553,000 | | 9,833,000 |
Total Impaired, Recorded Investment | 14,763,000 | | 10,057,000 |
Impaired Loans Receivable, Unpaid Principal Balance [Abstract] | | | |
Total Impaired with Reserve, Unpaid Principal Balance | 210,000 | | 633,000 |
Total Impaired with no Reserve, Unpaid Principal Balance | 16,359,000 | | 11,680,000 |
Total Impaired, Unpaid Principal Balance, Total | 16,569,000 | | 12,313,000 |
Impaired Loans Receivable, Reserve [Abstract] | | | |
Total Impaired with Reserve, Reserve | 24,000 | | 39,000 |
Total Impaired with no Reserve, Reserve | 0 | | 0 |
Impaired Loans, Reserve | 24,000 | | 39,000 |
Impaired Loans Receivable, Cumulative Charge Offs [Abstract] | | | |
Total Impaired with Reserve, Cumulative Charge-offs | 0 | | 409,000 |
Total Impaired with no Reserve, Cumulative Charge-offs | 1,806,000 | | 1,847,000 |
Total Impaired, Cumulative Charge-offs | 1,806,000 | | 2,256,000 |
Impaired Loans Receivable, Average Recorded Investment [Abstract] | | | |
Total Impaired with Reserve, Average Recorded Investment | 214,000 | $ 276,000 | |
Total Impaired with no Reserve, Average Recorded Investment | 14,766,000 | 9,283,000 | |
Total Impaired, Average Recorded Investment, Total | 14,980,000 | 9,559,000 | |
Impaired Loans Receivable, Interest Paid YTD [Abstract] | | | |
Total Impaired with Reserve, Interest Paid YTD | 12,000 | 11,000 | |
Total Impaired with no Reserve, Interest Paid YTD | 625,000 | 443,000 | |
Total Impaired, Interest Paid YTD | 637,000 | 454,000 | |
Charge-offs recorded to reduce the unpaid principal balance | 1,800,000 | | |
Total impaired loans including troubled debt restructurings | 9,558,000 | | 4,018,000 |
Substandard [Member] | | | |
Loans and Leases Receivable [Abstract] | | | |
At December 31, 2016 | 9,958,000 | | 11,013,000 |
Watch [Member] | | | |
Loans and Leases Receivable [Abstract] | | | |
At December 31, 2016 | 27,754,000 | | 8,237,000 |
Pass [Member] | | | |
Loans and Leases Receivable [Abstract] | | | |
At December 31, 2016 | 1,396,420,000 | | 1,368,781,000 |
Residential Real Estate [Member] | One-to-Four Family [Member] | | | |
Loans and Leases Receivable [Abstract] | | | |
At December 31, 2016 | 452,491,000 | | 480,280,000 |
Impaired Loans Receivable, Recorded Investment [Abstract] | | | |
Total Impaired, with Reserve, Recorded Investment | 210,000 | | 217,000 |
Total Impaired, with no Reserve, Recorded Investment | 7,825,000 | | 8,508,000 |
Total Impaired, Recorded Investment | 8,035,000 | | 8,725,000 |
Impaired Loans Receivable, Unpaid Principal Balance [Abstract] | | | |
Total Impaired with Reserve, Unpaid Principal Balance | 210,000 | | 217,000 |
Total Impaired with no Reserve, Unpaid Principal Balance | 8,820,000 | | 9,531,000 |
Total Impaired, Unpaid Principal Balance, Total | 9,030,000 | | 9,748,000 |
Impaired Loans Receivable, Reserve [Abstract] | | | |
Total Impaired with Reserve, Reserve | 24,000 | | 32,000 |
Total Impaired with no Reserve, Reserve | 0 | | 0 |
Impaired Loans, Reserve | 24,000 | | 32,000 |
Impaired Loans Receivable, Cumulative Charge Offs [Abstract] | | | |
Total Impaired with Reserve, Cumulative Charge-offs | 0 | | 0 |
Total Impaired with no Reserve, Cumulative Charge-offs | 995,000 | | 1,023,000 |
Total Impaired, Cumulative Charge-offs | 995,000 | | 1,023,000 |
Impaired Loans Receivable, Average Recorded Investment [Abstract] | | | |
Total Impaired with Reserve, Average Recorded Investment | 214,000 | 265,000 | |
Total Impaired with no Reserve, Average Recorded Investment | 7,986,000 | 7,779,000 | |
Total Impaired, Average Recorded Investment, Total | 8,200,000 | 8,044,000 | |
Impaired Loans Receivable, Interest Paid YTD [Abstract] | | | |
Total Impaired with Reserve, Interest Paid YTD | 12,000 | 11,000 | |
Total Impaired with no Reserve, Interest Paid YTD | 353,000 | 358,000 | |
Total Impaired, Interest Paid YTD | 365,000 | 369,000 | |
Total impaired loans including troubled debt restructurings | 3,300,000 | | 3,425,000 |
Residential Real Estate [Member] | One-to-Four Family [Member] | Substandard [Member] | | | |
Loans and Leases Receivable [Abstract] | | | |
At December 31, 2016 | 8,035,000 | | 8,725,000 |
Residential Real Estate [Member] | One-to-Four Family [Member] | Watch [Member] | | | |
Loans and Leases Receivable [Abstract] | | | |
At December 31, 2016 | 6,983,000 | | 5,975,000 |
Residential Real Estate [Member] | One-to-Four Family [Member] | Pass [Member] | | | |
Loans and Leases Receivable [Abstract] | | | |
At December 31, 2016 | 437,473,000 | | 465,580,000 |
Residential Real Estate [Member] | Multi Family [Member] | | | |
Loans and Leases Receivable [Abstract] | | | |
At December 31, 2016 | 599,637,000 | | 584,859,000 |
Impaired Loans Receivable, Recorded Investment [Abstract] | | | |
Total Impaired, with Reserve, Recorded Investment | 0 | | 0 |
Total Impaired, with no Reserve, Recorded Investment | 616,000 | | 667,000 |
Total Impaired, Recorded Investment | 616,000 | | 667,000 |
Impaired Loans Receivable, Unpaid Principal Balance [Abstract] | | | |
Total Impaired with Reserve, Unpaid Principal Balance | 0 | | 0 |
Total Impaired with no Reserve, Unpaid Principal Balance | 1,427,000 | | 1,491,000 |
Total Impaired, Unpaid Principal Balance, Total | 1,427,000 | | 1,491,000 |
Impaired Loans Receivable, Reserve [Abstract] | | | |
Total Impaired with Reserve, Reserve | 0 | | 0 |
Total Impaired with no Reserve, Reserve | 0 | | 0 |
Impaired Loans, Reserve | 0 | | 0 |
Impaired Loans Receivable, Cumulative Charge Offs [Abstract] | | | |
Total Impaired with Reserve, Cumulative Charge-offs | 0 | | 0 |
Total Impaired with no Reserve, Cumulative Charge-offs | 811,000 | | 824,000 |
Total Impaired, Cumulative Charge-offs | 811,000 | | 824,000 |
Impaired Loans Receivable, Average Recorded Investment [Abstract] | | | |
Total Impaired with Reserve, Average Recorded Investment | 0 | 0 | |
Total Impaired with no Reserve, Average Recorded Investment | 643,000 | 715,000 | |
Total Impaired, Average Recorded Investment, Total | 643,000 | 715,000 | |
Impaired Loans Receivable, Interest Paid YTD [Abstract] | | | |
Total Impaired with Reserve, Interest Paid YTD | 0 | 0 | |
Total Impaired with no Reserve, Interest Paid YTD | 61,000 | 60,000 | |
Total Impaired, Interest Paid YTD | 61,000 | 60,000 | |
Total impaired loans including troubled debt restructurings | 272,000 | | 308,000 |
Residential Real Estate [Member] | Multi Family [Member] | Substandard [Member] | | | |
Loans and Leases Receivable [Abstract] | | | |
At December 31, 2016 | 616,000 | | 668,000 |
Residential Real Estate [Member] | Multi Family [Member] | Watch [Member] | | | |
Loans and Leases Receivable [Abstract] | | | |
At December 31, 2016 | 0 | | 0 |
Residential Real Estate [Member] | Multi Family [Member] | Pass [Member] | | | |
Loans and Leases Receivable [Abstract] | | | |
At December 31, 2016 | 599,021,000 | | 584,191,000 |
Residential Real Estate [Member] | Home Equity [Member] | | | |
Loans and Leases Receivable [Abstract] | | | |
At December 31, 2016 | 15,410,000 | | 18,071,000 |
Impaired Loans Receivable, Recorded Investment [Abstract] | | | |
Total Impaired, with Reserve, Recorded Investment | 0 | | 0 |
Total Impaired, with no Reserve, Recorded Investment | 75,000 | | 84,000 |
Total Impaired, Recorded Investment | 75,000 | | 84,000 |
Impaired Loans Receivable, Unpaid Principal Balance [Abstract] | | | |
Total Impaired with Reserve, Unpaid Principal Balance | 0 | | 0 |
Total Impaired with no Reserve, Unpaid Principal Balance | 75,000 | | 84,000 |
Total Impaired, Unpaid Principal Balance, Total | 75,000 | | 84,000 |
Impaired Loans Receivable, Reserve [Abstract] | | | |
Total Impaired with Reserve, Reserve | 0 | | 0 |
Total Impaired with no Reserve, Reserve | 0 | | 0 |
Impaired Loans, Reserve | 0 | | 0 |
Impaired Loans Receivable, Cumulative Charge Offs [Abstract] | | | |
Total Impaired with Reserve, Cumulative Charge-offs | 0 | | 0 |
Total Impaired with no Reserve, Cumulative Charge-offs | 0 | | 0 |
Total Impaired, Cumulative Charge-offs | 0 | | 0 |
Impaired Loans Receivable, Average Recorded Investment [Abstract] | | | |
Total Impaired with Reserve, Average Recorded Investment | 0 | 0 | |
Total Impaired with no Reserve, Average Recorded Investment | 78,000 | 129,000 | |
Total Impaired, Average Recorded Investment, Total | 78,000 | 129,000 | |
Impaired Loans Receivable, Interest Paid YTD [Abstract] | | | |
Total Impaired with Reserve, Interest Paid YTD | 0 | 0 | |
Total Impaired with no Reserve, Interest Paid YTD | 3,000 | 6,000 | |
Total Impaired, Interest Paid YTD | 3,000 | 6,000 | |
Residential Real Estate [Member] | Home Equity [Member] | Substandard [Member] | | | |
Loans and Leases Receivable [Abstract] | | | |
At December 31, 2016 | 261,000 | | 285,000 |
Residential Real Estate [Member] | Home Equity [Member] | Watch [Member] | | | |
Loans and Leases Receivable [Abstract] | | | |
At December 31, 2016 | 6,000 | | 3,000 |
Residential Real Estate [Member] | Home Equity [Member] | Pass [Member] | | | |
Loans and Leases Receivable [Abstract] | | | |
At December 31, 2016 | 15,143,000 | | 17,783,000 |
Construction and Land [Member] | | | |
Loans and Leases Receivable [Abstract] | | | |
At December 31, 2016 | 66,726,000 | | 37,033,000 |
Impaired Loans Receivable, Recorded Investment [Abstract] | | | |
Total Impaired, with Reserve, Recorded Investment | 0 | | 0 |
Total Impaired, with no Reserve, Recorded Investment | 0 | | 0 |
Total Impaired, Recorded Investment | 0 | | 0 |
Impaired Loans Receivable, Unpaid Principal Balance [Abstract] | | | |
Total Impaired with Reserve, Unpaid Principal Balance | 0 | | 0 |
Total Impaired with no Reserve, Unpaid Principal Balance | 0 | | 0 |
Total Impaired, Unpaid Principal Balance, Total | 0 | | 0 |
Impaired Loans Receivable, Reserve [Abstract] | | | |
Total Impaired with Reserve, Reserve | 0 | | 0 |
Total Impaired with no Reserve, Reserve | 0 | | 0 |
Impaired Loans, Reserve | 0 | | 0 |
Impaired Loans Receivable, Cumulative Charge Offs [Abstract] | | | |
Total Impaired with Reserve, Cumulative Charge-offs | 0 | | 0 |
Total Impaired with no Reserve, Cumulative Charge-offs | 0 | | 0 |
Total Impaired, Cumulative Charge-offs | 0 | | 0 |
Impaired Loans Receivable, Average Recorded Investment [Abstract] | | | |
Total Impaired with Reserve, Average Recorded Investment | 0 | 0 | |
Total Impaired with no Reserve, Average Recorded Investment | 0 | 0 | |
Total Impaired, Average Recorded Investment, Total | 0 | 0 | |
Impaired Loans Receivable, Interest Paid YTD [Abstract] | | | |
Total Impaired with Reserve, Interest Paid YTD | 0 | 0 | |
Total Impaired with no Reserve, Interest Paid YTD | 0 | 0 | |
Total Impaired, Interest Paid YTD | 0 | 0 | |
Construction and Land [Member] | Substandard [Member] | | | |
Loans and Leases Receivable [Abstract] | | | |
At December 31, 2016 | 0 | | 0 |
Construction and Land [Member] | Watch [Member] | | | |
Loans and Leases Receivable [Abstract] | | | |
At December 31, 2016 | 4,330,000 | | 0 |
Construction and Land [Member] | Pass [Member] | | | |
Loans and Leases Receivable [Abstract] | | | |
At December 31, 2016 | 62,396,000 | | 37,033,000 |
Commercial Real Estate [Member] | | | |
Loans and Leases Receivable [Abstract] | | | |
At December 31, 2016 | 241,248,000 | | 236,703,000 |
Impaired Loans Receivable, Recorded Investment [Abstract] | | | |
Total Impaired, with Reserve, Recorded Investment | 0 | | 7,000 |
Total Impaired, with no Reserve, Recorded Investment | 6,037,000 | | 574,000 |
Total Impaired, Recorded Investment | 6,037,000 | | 581,000 |
Impaired Loans Receivable, Unpaid Principal Balance [Abstract] | | | |
Total Impaired with Reserve, Unpaid Principal Balance | 0 | | 416,000 |
Total Impaired with no Reserve, Unpaid Principal Balance | 6,037,000 | | 574,000 |
Total Impaired, Unpaid Principal Balance, Total | 6,037,000 | | 990,000 |
Impaired Loans Receivable, Reserve [Abstract] | | | |
Total Impaired with Reserve, Reserve | 0 | | 7,000 |
Total Impaired with no Reserve, Reserve | 0 | | 0 |
Impaired Loans, Reserve | 0 | | 7,000 |
Impaired Loans Receivable, Cumulative Charge Offs [Abstract] | | | |
Total Impaired with Reserve, Cumulative Charge-offs | 0 | | 409,000 |
Total Impaired with no Reserve, Cumulative Charge-offs | 0 | | 0 |
Total Impaired, Cumulative Charge-offs | 0 | | 409,000 |
Impaired Loans Receivable, Average Recorded Investment [Abstract] | | | |
Total Impaired with Reserve, Average Recorded Investment | 0 | 11,000 | |
Total Impaired with no Reserve, Average Recorded Investment | 6,059,000 | 660,000 | |
Total Impaired, Average Recorded Investment, Total | 6,059,000 | 671,000 | |
Impaired Loans Receivable, Interest Paid YTD [Abstract] | | | |
Total Impaired with Reserve, Interest Paid YTD | 0 | 0 | |
Total Impaired with no Reserve, Interest Paid YTD | 208,000 | 19,000 | |
Total Impaired, Interest Paid YTD | 208,000 | 19,000 | |
Total impaired loans including troubled debt restructurings | 5,986,000 | | 285,000 |
Commercial Real Estate [Member] | Substandard [Member] | | | |
Loans and Leases Receivable [Abstract] | | | |
At December 31, 2016 | 325,000 | | 581,000 |
Commercial Real Estate [Member] | Watch [Member] | | | |
Loans and Leases Receivable [Abstract] | | | |
At December 31, 2016 | 12,193,000 | | 1,412,000 |
Commercial Real Estate [Member] | Pass [Member] | | | |
Loans and Leases Receivable [Abstract] | | | |
At December 31, 2016 | 228,730,000 | | 234,710,000 |
Consumer [Member] | | | |
Loans and Leases Receivable [Abstract] | | | |
At December 31, 2016 | 783,000 | | 832,000 |
Impaired Loans Receivable, Recorded Investment [Abstract] | | | |
Total Impaired, with Reserve, Recorded Investment | 0 | | 0 |
Total Impaired, with no Reserve, Recorded Investment | 0 | | 0 |
Total Impaired, Recorded Investment | 0 | | 0 |
Impaired Loans Receivable, Unpaid Principal Balance [Abstract] | | | |
Total Impaired with Reserve, Unpaid Principal Balance | 0 | | 0 |
Total Impaired with no Reserve, Unpaid Principal Balance | 0 | | 0 |
Total Impaired, Unpaid Principal Balance, Total | 0 | | 0 |
Impaired Loans Receivable, Reserve [Abstract] | | | |
Total Impaired with Reserve, Reserve | 0 | | 0 |
Total Impaired with no Reserve, Reserve | 0 | | 0 |
Impaired Loans, Reserve | 0 | | 0 |
Impaired Loans Receivable, Cumulative Charge Offs [Abstract] | | | |
Total Impaired with Reserve, Cumulative Charge-offs | 0 | | 0 |
Total Impaired with no Reserve, Cumulative Charge-offs | 0 | | 0 |
Total Impaired, Cumulative Charge-offs | 0 | | 0 |
Impaired Loans Receivable, Average Recorded Investment [Abstract] | | | |
Total Impaired with Reserve, Average Recorded Investment | 0 | 0 | |
Total Impaired with no Reserve, Average Recorded Investment | 0 | 0 | |
Total Impaired, Average Recorded Investment, Total | 0 | 0 | |
Impaired Loans Receivable, Interest Paid YTD [Abstract] | | | |
Total Impaired with Reserve, Interest Paid YTD | 0 | 0 | |
Total Impaired with no Reserve, Interest Paid YTD | 0 | 0 | |
Total Impaired, Interest Paid YTD | 0 | 0 | |
Consumer [Member] | Substandard [Member] | | | |
Loans and Leases Receivable [Abstract] | | | |
At December 31, 2016 | 0 | | 0 |
Consumer [Member] | Watch [Member] | | | |
Loans and Leases Receivable [Abstract] | | | |
At December 31, 2016 | 0 | | 0 |
Consumer [Member] | Pass [Member] | | | |
Loans and Leases Receivable [Abstract] | | | |
At December 31, 2016 | 783,000 | | 832,000 |
Commercial Loans [Member] | | | |
Loans and Leases Receivable [Abstract] | | | |
At December 31, 2016 | 57,837,000 | | 30,253,000 |
Minimum amount of potential loan exposure to be reviewed by credit management personnel | 200,000 | | |
Impaired Loans Receivable, Recorded Investment [Abstract] | | | |
Total Impaired, with Reserve, Recorded Investment | 0 | | 0 |
Total Impaired, with no Reserve, Recorded Investment | 0 | | 0 |
Total Impaired, Recorded Investment | 0 | | 0 |
Impaired Loans Receivable, Unpaid Principal Balance [Abstract] | | | |
Total Impaired with Reserve, Unpaid Principal Balance | 0 | | 0 |
Total Impaired with no Reserve, Unpaid Principal Balance | 0 | | 0 |
Total Impaired, Unpaid Principal Balance, Total | 0 | | 0 |
Impaired Loans Receivable, Reserve [Abstract] | | | |
Total Impaired with Reserve, Reserve | 0 | | 0 |
Total Impaired with no Reserve, Reserve | 0 | | 0 |
Impaired Loans, Reserve | 0 | | 0 |
Impaired Loans Receivable, Cumulative Charge Offs [Abstract] | | | |
Total Impaired with Reserve, Cumulative Charge-offs | 0 | | 0 |
Total Impaired with no Reserve, Cumulative Charge-offs | 0 | | 0 |
Total Impaired, Cumulative Charge-offs | 0 | | 0 |
Impaired Loans Receivable, Average Recorded Investment [Abstract] | | | |
Total Impaired with Reserve, Average Recorded Investment | 0 | 0 | |
Total Impaired with no Reserve, Average Recorded Investment | 0 | 0 | |
Total Impaired, Average Recorded Investment, Total | 0 | 0 | |
Impaired Loans Receivable, Interest Paid YTD [Abstract] | | | |
Total Impaired with Reserve, Interest Paid YTD | 0 | 0 | |
Total Impaired with no Reserve, Interest Paid YTD | 0 | 0 | |
Total Impaired, Interest Paid YTD | 0 | $ 0 | |
Commercial Loans [Member] | Substandard [Member] | | | |
Loans and Leases Receivable [Abstract] | | | |
At December 31, 2016 | 721,000 | | 754,000 |
Commercial Loans [Member] | Watch [Member] | | | |
Loans and Leases Receivable [Abstract] | | | |
At December 31, 2016 | 4,242,000 | | 847,000 |
Commercial Loans [Member] | Pass [Member] | | | |
Loans and Leases Receivable [Abstract] | | | |
At December 31, 2016 | $ 52,874,000 | | $ 28,652,000 |