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Employee Benefit Plans - Summary of Changes in the Fair Value of Level 3 (Details) - Significant Unobservable Inputs (Level 3) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016
Changes in the fair value of Level 3 assets |  |
Fair value of plan assets — beginning of year | $ 1.0 | $ 1.0
Transfer from Level 3 to Level 2 assets | 0.0 | 0.0
Sales | 0.0 | 0.0
Fair value of plan assets — end of year | 1.0 | 1.0
Global equity common trust funds |  |
Changes in the fair value of Level 3 assets |  |
Fair value of plan assets — beginning of year | 0.0 | 0.0
Transfer from Level 3 to Level 2 assets | 0.0 | 0.0
Sales | 0.0 | 0.0
Fair value of plan assets — end of year | 0.0 | 0.0
Commingled global fund allocation |  |
Changes in the fair value of Level 3 assets |  |
Fair value of plan assets — beginning of year | 0.0 | 0.0
Transfer from Level 3 to Level 2 assets | 0.0 | 0.0
Sales | 0.0 | 0.0
Fair value of plan assets — end of year | 0.0 | 0.0
Fixed income common trust funds |  |
Changes in the fair value of Level 3 assets |  |
Fair value of plan assets — beginning of year | 0.0 | 0.0
Transfer from Level 3 to Level 2 assets | 0.0 | 0.0
Sales | 0.0 | 0.0
Fair value of plan assets — end of year | 0.0 | 0.0
Other |  |
Changes in the fair value of Level 3 assets |  |
Fair value of plan assets — beginning of year | 1.0 | 1.0
Transfer from Level 3 to Level 2 assets | 0.0 | 0.0
Sales | 0.0 | 0.0
Fair value of plan assets — end of year | $ 1.0 | $ 1.0

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- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. + References No definition available. + Details
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- Definition Fair value of assets that have been segregated and restricted to provide pension or postretirement benefits. Assets include, but are not limited to, stocks, bonds, other investments, earnings from investments, and contributions by the employer and employees. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Amount, measured using unobservable inputs, of increase (decrease) in plan assets of defined benefit plan from purchases, sales and settlements. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(5)(iv)(02)(B) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Amount, measured using unobservable inputs, of increase (decrease) in plan assets of defined benefit plan, for assets transferred into (out of) Level 3 of fair value hierarchy. Includes, but is not limited to, transfer due to change in observability of significant inputs. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(5)(iv)(02)(C) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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