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Fair Value Measurements (Narrative) (Details) | 12 Months Ended
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Dec. 31, 2021 USD ($) | Dec. 31, 2020 USD ($) broker
Fair Value Measurement [Line Items] |  |
Percentage of portfolio of unadjusted fair values obtained | 97.90% |
Number of knowledgeable outside security brokers consulted to determine fair value | broker |  | 1
Three Private Equity Funds using NAV | $ 107,700,000 |
One Private Equity Fund using NAV | 700,000 |
Fair Value, Assets, Level 1 to Level 2 to Level 3 Transfers, Amount | 0 | $ 0
Unsecured Debt |  |
Fair Value Measurement [Line Items] |  |
Debt instrument, face amount | $ 375,000,000 | 375,000,000
Minimum |  |
Fair Value Measurement [Line Items] |  |
Liquidating investment, remaining period | 1 year |
Maximum |  |
Fair Value Measurement [Line Items] |  |
Liquidating investment, remaining period | 9 years |
Private Equity Funds |  |
Fair Value Measurement [Line Items] |  |
Unfunded commitments | $ 32,000,000 |
Level 2 | Commercial Mortgage Backed Securities |  |
Fair Value Measurement [Line Items] |  |
Holings in mortgage backed securities | $ 25,200,000 | $ 17,600,000

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- Definition Face (par) amount of debt instrument at time of issuance. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 50 -Paragraph 1B -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=124435984&loc=d3e28551-108399 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=124429444&loc=SL124452920-239629 Reference 5: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 55 -Paragraph 69C -URI http://asc.fasb.org/extlink&oid=123466577&loc=SL123495737-112612 Reference 6: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 55 -Paragraph 69B -URI http://asc.fasb.org/extlink&oid=123466577&loc=SL123495735-112612 + Details
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