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Loans Receivable - Loan Origination and Risk Management (Details) - USD ($) | 12 Months Ended |
--- | --- | ---
Dec. 31, 2018 | Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Loans and leases, amount | $ 1,331,194,000 | $ 1,321,751,000
Maximum [Member] | Finance Leases Financing Receivable [Member] | Investment Grade [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Outstanding credit exposure | 20,000,000 |
Multi-family mortgage loans [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Loans and leases, amount | $ 619,870,000 | 588,383,000
Multi-family mortgage loans [Member] | Collateralized Loan [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Collateralized Loan Receivable, Percentage Of Collateral Located Outside Primary Market Area | 55.00% |
Multi-family mortgage loans [Member] | Collateralized Loan [Member] | Mortgage loans above $400,000 [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Projected Cash Flow To Loan Debt Service Requirement | 120.00% |
Multi-family mortgage loans [Member] | Minimum [Member] | Collateralized Loan [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Loans and leases, amount | $ 500,000 |
Multi-family mortgage loans [Member] | Maximum [Member] | Collateralized Loan [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Loans and leases, amount | $ 5,000,000.0 |
Loan amount as a percentage to value of property collateralized | 0.8 |
Nonresidential real estate loans [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Loans and leases, amount | $ 152,442,000 | 169,971,000
Nonresidential real estate loans [Member] | Collateralized Loan [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Projected Cash Flow To Loan Debt Service Requirement | 120.00% |
Nonresidential real estate loans [Member] | Collateralized Loan [Member] | Fixed Rate Nonresidential Mortgage [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Amortization period | 15 years |
Nonresidential real estate loans [Member] | Minimum [Member] | Collateralized Loan [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Loans and leases, amount | $ 500,000 |
Maturity period | 3 years |
Balloon maturity | 3 years |
Amortization period | 20 years |
Nonresidential real estate loans [Member] | Maximum [Member] | Collateralized Loan [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Loans and leases, amount | $ 5,000,000.0 |
Loan amount as a percentage to value of property collateralized | 0.8 |
Maturity period | 5 years |
Balloon maturity | 5 years |
Amortization period | 30 years |
Residential mortgage [Member] | Maximum [Member] | Adjustable Rate And Fixed Rate Residential Mortgage [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Maturity period | 30 years |
Residential mortgage [Member] | Maximum [Member] | $2,500,000 [Member] | Adjustable Rate And Fixed Rate Residential Mortgage [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate, Face Amount of Mortgages | $ 2,500,000 |
Residential mortgage [Member] | Maximum [Member] | $2,500,000 [Member] | Conforming Loans [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate, Face Amount of Mortgages | 424,000 |
Finance Leases Financing Receivable [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Loans and leases, amount | $ 299,394,000 | $ 310,076,000
Finance Leases Financing Receivable [Member] | Maximum [Member] | No Public Rating [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Commercial Leases, Maturity | 5 years |
Outstanding credit exposure | $ 10,000,000 |
Finance Leases Financing Receivable [Member] | Maximum [Member] | Investment Grade [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Outstanding credit exposure | $ 10,000,000 |

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- Definition Amount of contractual principal due at origination of mortgage loan within investment in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 12 -Paragraph Column F -Subsection 29 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 948 -SubTopic 310 -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-29(Column F)) -URI http://asc.fasb.org/extlink&oid=6589523&loc=d3e617274-123014 + Details
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- Definition Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=82891408&loc=d3e4428-111522 + Details
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