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Employee Benefits - Additional Information (Details) - USD ($) | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items] |  |  |
Number of consecutive years of employee's compensation | 5 years |  |
Number of total years of employee's compensation | 10 years |  |
Service cost | $ 0 |  |
Expected long-term rate of return on plan assets | 3.45% | 4.80% | 7.50%
Accumulated benefit obligation | $ 117,500,000 | $ 113,700,000 |
Projected benefit obligation | 117,506,000 | 113,679,000 | $ 95,200,000
Net periodic benefit cost | 1,783,000 | 867,000 | (250,000)
Amounts before tax reflected in accumulated other comprehensive income (loss) | 19,572,000 | 23,106,000 |
Settlement charge | 833,000 | 0 | 0
Purchases of level 3 plan assets | 0 | 0 |
Transfers of level 3 plan assets | 0 | 0 |
Supplemental Executive Retirement Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Projected benefit obligation | 5,600,000 | 5,300,000 |
Net periodic benefit cost | 700,000 | 400,000 | 500,000
Amounts before tax reflected in accumulated other comprehensive income (loss) | 2,400,000 | 2,400,000 | 1,900,000
Settlement charge | $ 200,000 |  |
Thrift Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Contributions to the Thrift Plan | 3.50% |  |
Compensation expense | $ 2,400,000 | $ 2,000,000.0 | $ 1,700,000
Equities and alternatives | Minimum |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Targeted asset allocation percentage | 5.00% |  |
Equities and alternatives | Maximum |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Targeted asset allocation percentage | 15.00% |  |
Fixed income | Minimum |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Targeted asset allocation percentage | 85.00% |  |
Fixed income | Maximum |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Targeted asset allocation percentage | 95.00% |  |

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- Definition Number Of Periods Used To Determine Defined Benefit Pension Plan Benefits + References No definition available. + Details
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- Definition Amount of actuarial present value of benefits attributed to employee service rendered, excluding assumptions about future compensation level. + 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 (e) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details
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- Definition Amount, before tax, of accumulated other comprehensive (income) loss for defined benefit plan, that has not been recognized in net periodic benefit cost (credit). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 10A -Subparagraph (i-k) -URI http://asc.fasb.org/extlink&oid=121641772&loc=SL7669646-108580 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI http://asc.fasb.org/extlink&oid=121641772&loc=SL7669686-108580 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (j) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details
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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=118255775&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=118255775&loc=d3e2919-114920 + Details
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- Definition Amount of gain (loss) recognized in net periodic benefit (cost) credit from irrevocable action relieving primary responsibility for benefit obligation and eliminating risk related to obligation and assets used to effect settlement. + 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 (h)(7) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 45 -Paragraph 3A -URI http://asc.fasb.org/extlink&oid=109237824&loc=SL108413299-114919 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (a)(7) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e2709-114920 + Details
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