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Commitments and Contingencies (Lease Commitments) (Details) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2020 USD ($) lease | Dec. 31, 2019 USD ($) | Dec. 31, 2018 USD ($)
Lease Commitments |  |  |
Number of operating leases | lease | 3 |  |
Operating lease expense | $ 3.0 | $ 2.7 | $ 2.7
Corporate headquarters |  |  |
Lease Commitments |  |  |
Lease cost | $ 2.9 |  |
New Corporate Headquarters Location |  |  |
Lease Commitments |  |  |
Term of lease | 15 years |  |
Renewal term | 5 years |  |
Operating lease, liability | $ 4.6 |  |

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- Definition Amount of lease cost recognized by lessee for lease contract. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=121609121&loc=SL77918686-209980 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 55 -Paragraph 53 -URI http://asc.fasb.org/extlink&oid=121568110&loc=SL77918982-209971 + Details
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- Definition Term of lessee's operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=121609121&loc=SL77918673-209980 + Details
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- Definition Amount of operating lease expense. Excludes sublease income. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 45 -Paragraph 4 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121603541&loc=SL77918638-209977 + Details
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