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Fair Value Measurements - Changes in Level 3 (Details) - USD ($) $ in Thousands | 9 Months Ended
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Sep. 30, 2019 | Sep. 30, 2018
Changes in Level 3 |  |
Beginning balance |  | $ 2,268
Total gains or losses |  |
Included in other comprehensive income |  | 34
Purchases, issuances, sales, and settlements |  |
Settlements |  | (770)
Ending balance |  | 1,564
Changes in Level 3 (liabilities) |  |
Included in earnings (or changes in net assets) |  | 32
US States and Political Subdivisions Debt Securities [Member] |  |
Changes in Level 3 |  |
Beginning balance | $ 8,165 | 14,261
Total gains or losses |  |
Included in other comprehensive income | 898 | (805)
Purchases, issuances, sales, and settlements |  |
Purchases | 17,643 | 20,421
Settlements | (20,808) | (24,366)
Ending balance | 5,873 | 9,511
Changes in Level 3 (liabilities) |  |
Included in earnings (or changes in net assets) | (25) |
Mortgage Servicing Rights [Member] |  |
Changes in Level 3 |  |
Beginning balance | 7,357 | 6,944
Total gains or losses |  |
Included in earnings (or changes in net assets) |  | 636
Purchases, issuances, sales, and settlements |  |
Issuances | 906 | 997
Settlements | (518) | (446)
Ending balance | 5,361 | $ 8,131
Changes in Level 3 (liabilities) |  |
Included in earnings (or changes in net assets) | $ (2,384) |

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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 issuances 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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- Definition Amount of settlement 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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