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Transfers of Assets between Level 1 and Level 2 (Detail) - First Quarter - USD ($) $ in Millions | Mar. 31, 2018 | Mar. 31, 2017
--- | --- | ---
Transfers Between Level 1 and Level 2 |  |
Level 1 from Level 2 | $ 5,843.5 | $ 7,475.4
Level 2 from Level 1 | 1,015.3 | 1,312.8
United States Government and Government Agencies and Authorities |  |
Transfers Between Level 1 and Level 2 |  |
Level 1 from Level 2 | 40.1 | 54.5
Level 2 from Level 1 | 0.0 | 180.0
Public Utilities |  |
Transfers Between Level 1 and Level 2 |  |
Level 1 from Level 2 | 528.5 | 1,103.9
Level 2 from Level 1 | 62.0 | 57.5
All Other Corporate Bonds |  |
Transfers Between Level 1 and Level 2 |  |
Level 1 from Level 2 | 5,274.9 | 6,317.0
Level 2 from Level 1 | 953.3 | 1,075.3
Equity Securities |  |
Transfers Between Level 1 and Level 2 |  |
Level 1 from Level 2 | 24.2 | 0.0
Level 2 from Level 1 | $ 14.9 | $ 0.0

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- Definition Amount of transfers of assets measured on a recurring basis out of Level 1 of the fair value hierarchy into Level 2. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (bb) -URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258 + Details
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