Statutory Permitted Practice Information (Detail) - Unum Life Insurance Company of America - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Statutory Accounting Practices
Statutory Accounting Practices, Permitted Practice, Cumulative Amount	$ 1,191.0	$ 667.0	$ 229.0
Statutory Accounting Practices, Permitted Practice, Reserve Deficiency	$ 1,660.0	$ 2,310.0	$ 2,061.0