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Benefit Plans - Plan Assets Allocation (Details) - Pension Plan | 12 Months Ended
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Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Benefit Plans |  |  |
Asset Allocation (as a percent) | 100.00% | 100.00% |
Equity securities |  |  |
Benefit Plans |  |  |
Asset Allocation (as a percent) | 11.00% | 13.00% |
Target Allocation (as a percent) | 10.00% |  |
FHI stock |  |  |
Benefit Plans |  |  |
Asset Allocation (as a percent) | 0.00% | 0.00% |
BNP Paribas stock |  |  |
Benefit Plans |  |  |
Asset Allocation (as a percent) | 0.00% | 0.00% |
Debt securities |  |  |
Benefit Plans |  |  |
Asset Allocation (as a percent) | 85.00% | 85.00% |
Target Allocation (as a percent) | 88.00% |  |
Other securities |  |  |
Benefit Plans |  |  |
Asset Allocation (as a percent) | 4.00% | 2.00% |
Target Allocation (as a percent) | 2.00% |  |
Qualified Plan (ERP) |  |  |
Benefit Plans |  |  |
Expected long term return on plan assets (as a percent) | 2.75% | 4.40% | 4.75%

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- Definition Weighted average rate of return on plan assets, reflecting average rate of earnings expected on existing plan assets and expected contributions, used to determine net periodic benefit cost of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k)(3) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e2919-114920 + Details
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- Definition Percentage of target investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=123450688&loc=d3e4179-114921 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(i) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
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