Statutory Permitted Practice Information (Detail) - Unum Life Insurance Company of America - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Statutory Accounting Practices
Statutory Accounting Practices, Permitted Practice, Cumulative Amount	$ 1,604.0	$ 1,191.0	$ 667.0
Statutory Accounting Practices, Permitted Practice, Reserve Deficiency	$ 0.0	$ 1,660.0	$ 2,310.0

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(23)(c))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479440/944-210-S99-1

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