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Pension and Other Postretirement Benefit Plans - Recurring Fair Value Measures (Details) - USD ($) $ in Millions | Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
--- | --- | --- | ---
Pension [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | $ 745.7 |  | $ 759.4 |  | $ 699.6
Pension [Member] | Level 1 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 12.2 |  | 3.2 |  |
Pension [Member] | Level 2 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 711.9 |  | 731.2 |  |
Pension [Member] | Level 3 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 21.6 |  | 25.0 |  |
Pension [Member] | U.S. Large-cap [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 113.8 | [1] | 91.7 | [2] |
Pension [Member] | U.S. Large-cap [Member] | Level 1 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 0.0 | [1] | 0.0 | [2] |
Pension [Member] | U.S. Large-cap [Member] | Level 2 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 113.8 | [1] | 91.7 | [2] |
Pension [Member] | U.S. Large-cap [Member] | Level 3 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 0.0 | [1] | 0.0 | [2] |
Pension [Member] | U.S. Mid-cap Growth [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 47.6 | [1] | 40.0 | [2] |
Pension [Member] | U.S. Mid-cap Growth [Member] | Level 1 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 0.0 | [1] | 0.0 | [2] |
Pension [Member] | U.S. Mid-cap Growth [Member] | Level 2 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 47.6 | [1] | 40.0 | [2] |
Pension [Member] | U.S. Mid-cap Growth [Member] | Level 3 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 0.0 | [1] | 0.0 | [2] |
Pension [Member] | U.S. Small-cap [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 46.2 | [1] | 40.7 | [2] |
Pension [Member] | U.S. Small-cap [Member] | Level 1 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 0.0 | [1] | 0.0 | [2] |
Pension [Member] | U.S. Small-cap [Member] | Level 2 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 46.2 | [1] | 40.7 | [2] |
Pension [Member] | U.S. Small-cap [Member] | Level 3 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 0.0 | [1] | 0.0 | [2] |
Pension [Member] | International [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 158.2 |  | 97.1 |  |
Pension [Member] | International [Member] | Level 1 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 0.0 |  | 0.0 |  |
Pension [Member] | International [Member] | Level 2 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 158.2 |  | 97.1 |  |
Pension [Member] | International [Member] | Level 3 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 0.0 |  | 0.0 |  |
Pension [Member] | Fixed Income [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 346.1 | [1] | 461.7 | [2] |
Pension [Member] | Fixed Income [Member] | Level 1 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 0.0 | [1] | 0.0 | [2] |
Pension [Member] | Fixed Income [Member] | Level 2 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 346.1 | [1] | 461.7 | [2] |
Pension [Member] | Fixed Income [Member] | Level 3 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 0.0 | [1] | 0.0 | [2] |
Pension [Member] | Cash and Cash Equivalents [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 12.2 |  | 3.2 |  |
Pension [Member] | Cash and Cash Equivalents [Member] | Level 1 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 12.2 |  | 3.2 |  |
Pension [Member] | Cash and Cash Equivalents [Member] | Level 2 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 0.0 |  | 0.0 |  |
Pension [Member] | Cash and Cash Equivalents [Member] | Level 3 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 0.0 |  | 0.0 |  |
Pension [Member] | Private Equity [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 0.0 |  | 7.0 |  |
Pension [Member] | Private Equity [Member] | Level 1 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 0.0 |  | 0.0 |  |
Pension [Member] | Private Equity [Member] | Level 2 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 0.0 |  | 0.0 |  |
Pension [Member] | Private Equity [Member] | Level 3 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 0.0 |  | 7.0 |  | 8.0
Pension [Member] | Real Estate [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 21.6 |  | 18.0 |  |
Pension [Member] | Real Estate [Member] | Level 1 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 0.0 |  | 0.0 |  |
Pension [Member] | Real Estate [Member] | Level 2 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 0.0 |  | 0.0 |  |
Pension [Member] | Real Estate [Member] | Level 3 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 21.6 |  | 18.0 |  | 18.0
Postretirement Health and Life [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 201.8 |  | 186.0 |  | 173.7
Postretirement Health and Life [Member] | Level 1 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 198.0 |  | 182.1 |  |
Postretirement Health and Life [Member] | Level 2 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 1.8 |  | 2.2 |  |
Postretirement Health and Life [Member] | Level 3 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 2.0 |  | 1.7 |  |
Postretirement Health and Life [Member] | U.S. Large-cap [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 40.1 | [3] | 34.2 | [4] |
Postretirement Health and Life [Member] | U.S. Large-cap [Member] | Level 1 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 40.1 | [3] | 34.2 | [4] |
Postretirement Health and Life [Member] | U.S. Large-cap [Member] | Level 2 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 0.0 | [3] | 0.0 | [4] |
Postretirement Health and Life [Member] | U.S. Large-cap [Member] | Level 3 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 0.0 | [3] | 0.0 | [4] |
Postretirement Health and Life [Member] | U.S. Mid-cap Growth [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 37.3 | [3] | 31.4 | [4] |
Postretirement Health and Life [Member] | U.S. Mid-cap Growth [Member] | Level 1 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 37.3 | [3] | 31.4 | [4] |
Postretirement Health and Life [Member] | U.S. Mid-cap Growth [Member] | Level 2 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 0.0 | [3] | 0.0 | [4] |
Postretirement Health and Life [Member] | U.S. Mid-cap Growth [Member] | Level 3 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 0.0 | [3] | 0.0 | [4] |
Postretirement Health and Life [Member] | U.S. Small-cap [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 19.3 | [3] | 16.6 | [4] |
Postretirement Health and Life [Member] | U.S. Small-cap [Member] | Level 1 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 19.3 | [3] | 16.6 | [4] |
Postretirement Health and Life [Member] | U.S. Small-cap [Member] | Level 2 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 0.0 | [3] | 0.0 | [4] |
Postretirement Health and Life [Member] | U.S. Small-cap [Member] | Level 3 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 0.0 | [3] | 0.0 | [4] |
Postretirement Health and Life [Member] | International [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 43.7 | [3] | 41.5 | [4] |
Postretirement Health and Life [Member] | International [Member] | Level 1 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 43.7 | [3] | 41.5 | [4] |
Postretirement Health and Life [Member] | International [Member] | Level 2 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 0.0 | [3] | 0.0 | [4] |
Postretirement Health and Life [Member] | International [Member] | Level 3 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 0.0 | [3] | 0.0 | [4] |
Postretirement Health and Life [Member] | Mutual Funds [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 56.7 |  | 57.3 |  |
Postretirement Health and Life [Member] | Mutual Funds [Member] | Level 1 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 56.7 |  | 57.3 |  |
Postretirement Health and Life [Member] | Mutual Funds [Member] | Level 2 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 0.0 |  | 0.0 |  |
Postretirement Health and Life [Member] | Mutual Funds [Member] | Level 3 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 0.0 |  | 0.0 |  |
Postretirement Health and Life [Member] | Fixed Income [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 1.8 |  | 2.2 |  |
Postretirement Health and Life [Member] | Fixed Income [Member] | Level 1 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 0.0 |  | 0.0 |  |
Postretirement Health and Life [Member] | Fixed Income [Member] | Level 2 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 1.8 |  | 2.2 |  |
Postretirement Health and Life [Member] | Fixed Income [Member] | Level 3 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 0.0 |  | 0.0 |  |
Postretirement Health and Life [Member] | Cash and Cash Equivalents [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 0.9 |  | 1.1 |  |
Postretirement Health and Life [Member] | Cash and Cash Equivalents [Member] | Level 1 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 0.9 |  | 1.1 |  |
Postretirement Health and Life [Member] | Cash and Cash Equivalents [Member] | Level 2 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 0.0 |  | 0.0 |  |
Postretirement Health and Life [Member] | Cash and Cash Equivalents [Member] | Level 3 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 0.0 |  | 0.0 |  |
Postretirement Health and Life [Member] | Private Equity [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 2.0 |  | 1.7 |  |
Postretirement Health and Life [Member] | Private Equity [Member] | Level 1 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 0.0 |  | 0.0 |  |
Postretirement Health and Life [Member] | Private Equity [Member] | Level 2 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | 0.0 |  | 0.0 |  |
Postretirement Health and Life [Member] | Private Equity [Member] | Level 3 [Member] |  |  |  |  |
Recurring Fair Value Measures [Line Items] |  |  |  |  |
Fair Value of Assets | $ 2.0 |  | $ 1.7 |  | $ 1.7
[1] | The underlying investments consist of actively-managed funds managed to achieve the returns of certain U.S. equity and fixed income securities indexes.
[2] | The underlying investments consist of actively-managed funds managed to achieve the returns of certain U.S. equity and fixed income securities indexes.
[3] | The underlying investments consist of mutual funds (Level 1).
[4] | The underlying investments consist of mutual funds (Level 1).

X
- Definition Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee. + 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 (d)(iv)(01) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(iv)(01) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(ii) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 Reference 4: 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 5: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(iv)(02) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 Reference 7: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(ii) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
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