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Fair Value Measurements (Change in Fair Value of Securities Using Level 3 Inputs) (Details) - Available-for-sale Securities [Member] - USD ($) $ in Thousands | 3 Months Ended
--- | ---
Mar. 31, 2020 | Mar. 31, 2019
US States and Political Subdivisions Debt Securities [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Fair value, December 31, | $ 0 |
Total net (losses) gains for the period included in OCI | 0 |
Total net (losses) gains for the period included in net income | 0 |
Purchases | 0 |
Sales | 0 |
Issuances | 0 |
Settlements | 0 |
Transfers into Level 3 | 2,890 |
Transfers out of Level 3 | 0 |
Fair value, March 31 | 2,890 |
Period change unrealized gains (losses) in earnings | 0 |
Period change unrealized gains (losses) in OCI | 0 |
Corporate Securities [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Fair value, December 31, | 17,051 | $ 0
Total net (losses) gains for the period included in OCI | 1 | 0
Total net (losses) gains for the period included in net income | (61) | 0
Purchases | 3,002 | 0
Sales | 0 | 0
Issuances | 0 | 0
Settlements | 0 | 0
Transfers into Level 3 | 4,192 | 16,419
Transfers out of Level 3 | 0 | 0
Fair value, March 31 | 24,185 | 16,419
Period change unrealized gains (losses) in earnings | (61) | 0
Period change unrealized gains (losses) in OCI | 1 |
Collateralized Loan Obligations and Other Asset Backed Securities [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Fair value, December 31, | 17,034 | 7,409
Total net (losses) gains for the period included in OCI | (1,756) | (225)
Total net (losses) gains for the period included in net income | (214) | 0
Purchases | 4,831 | 12,434
Sales | 0 | 0
Issuances | 0 | 0
Settlements | 0 | 0
Transfers into Level 3 | 20,107 | 11,674
Transfers out of Level 3 | (3,630) | 0
Fair value, March 31 | 36,372 | 31,292
Period change unrealized gains (losses) in earnings | (214) | 0
Period change unrealized gains (losses) in OCI | (1,756) |
Investments [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Fair value, December 31, | 34,085 | 7,409
Total net (losses) gains for the period included in OCI | (1,755) | (225)
Total net (losses) gains for the period included in net income | (275) | 0
Purchases | 7,833 | 12,434
Sales | 0 | 0
Issuances | 0 | 0
Settlements | 0 | 0
Transfers into Level 3 | 27,189 | 28,093
Transfers out of Level 3 | (3,630) | 0
Fair value, March 31 | 63,447 | 47,711
Period change unrealized gains (losses) in earnings | (275) | $ 0
Period change unrealized gains (losses) in OCI | $ (1,755) |

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- Definition Amount of gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 + Details
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- Definition Amount of gain (loss) recognized in other comprehensive income (OCI) from asset measured at fair value on recurring basis using unobservable input (level 3). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1a) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 + Details
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- Definition Amount of purchases of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 + Details
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