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Debt Instrument Liquidation Amount Per Share

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Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Amount of the required periodic payments applied to principal.

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Face (par) amount of the original debt instrument that was repurchased.

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Nominal or face amount used to calculate payment on derivative.

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Gross amount of debt extinguished.

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Amount of cash paid for interest, including, but not limited to, capitalized interest and payment to settle zero-coupon bond attributable to accreted interest of debt discount and debt instrument with insignificant coupon interest rate in relation to effective interest rate of borrowing attributable to accreted interest of debt discount; classified as operating and investing activities.

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The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

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The fee, expressed as a percentage of the line of credit facility, for the line of credit facility regardless of whether the facility has been used.

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Amount of long-term debt payable, sinking fund requirement, and other securities issued that are redeemable by holder at fixed or determinable price and date, maturing after fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of long-term debt payable, sinking fund requirement, and other securities issued that are redeemable by holder at fixed or determinable price and date, maturing in fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of long-term debt payable, sinking fund requirement, and other securities issued that are redeemable by holder at fixed or determinable price and date, maturing in fourth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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The cash inflow during the period from additional borrowings in aggregate debt. Includes proceeds from short-term and long-term debt.

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The cash inflow from a borrowing with the highest claim on the assets of the entity in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle, if longer).

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Debt - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2007	Dec. 31, 1998	Dec. 31, 2018
Debt Additional Information
Repayments of Principal in 2023	$ 2.0
Repayments of Principal in 2024	350.0
Repayments of Principal in 2025	275.0
Repayments of Principal Thereafter	$ 2,847.5
Unum Group Percentage Ownership of Provident Financing Trust	100.00%
Interest Paid, Including Capitalized Interest, Operating and Investing Activities	$ 181.6	$ 178.1	$ 172.9
Notional Amount Of Derivatives Terminations	1,314.3	257.3	471.5
Derivative, Notional Amount	970.5	744.4	881.4			$ 799.2
Parent Company
Debt Additional Information
Repayments of Principal in 2023	2.0
Repayments of Principal in 2024	350.0
Repayments of Principal in 2025	275.0
Repayments of Principal Thereafter	$ 2,847.5
Unum Group Percentage Ownership of Provident Financing Trust	100.00%
Interest Paid, Including Capitalized Interest, Operating and Investing Activities	$ 181.6	176.6	168.4
Parent Company \| Five-year Unsecured Revolving Credit Facility
Debt Additional Information
Letters of Credit Outstanding	0.0
Line of Credit Facility, Maximum Borrowing Capacity	500.0
Parent Company \| Three-year Unsecured Revolving Credit Facility
Debt Additional Information
Letters of Credit Outstanding	0.0
Parent Company \| Facility agreement for contingent issuance of senior notes
Debt Additional Information
Line of Credit Facility, Maximum Borrowing Capacity	$ 400.0
Line of Credit Facility, Commitment Fee Percentage	2.225%
Debt Instrument, Covenant Description	2.0 billion
Medium Term Notes Payable Due 2028
Debt Additional Information
Costs Related to Early Retirement of Debt			27.3
Notes Issued in 1998 with 2028 Maturity Date
Debt Additional Information
Costs Related to Early Retirement of Debt			27.3
Senior Notes Payable due 2021
Debt Additional Information
Costs Related to Early Retirement of Debt			27.3
Notes Issued in 2019 due 2049 \| Senior Notes
Debt Additional Information
Proceeds from Issuance of Debt			$ 450.0
Stated Interest Rate of Debt			4.50%
Notes Issued in 2019 \| Senior Notes
Debt Additional Information
Proceeds from Issuance of Debt			$ 400.0
Stated Interest Rate of Debt			4.00%
Notes Issued in 1998 with 2038 Maturity Date \| Junior Subordinated Debt
Debt Additional Information
Stated Interest Rate of Debt	7.405%
Proceeds from Issuance of Senior Long-term Debt					$ 300.0
Liquidation value per capital security	$ 1,000
Notes Issued in 1998 with 2038 Maturity Date \| Junior Subordinated Debt \| Parent Company
Debt Additional Information
Proceeds from Issuance of Debt					$ 300.0
Stated Interest Rate of Debt	7.405%		7.405%
Liquidation value per capital security	$ 1,000
Capital Securities Notes Payable Due 2038
Debt Additional Information
Stated Interest Rate of Debt			7.405%
Extinguishment of Debt, Amount			$ 22.8
Capital Securities Notes Payable Due 2038 \| Parent Company
Debt Additional Information
Extinguishment of Debt, Amount			$ 22.8
Notes 5.625 Due 2020
Debt Additional Information
Debt Instrument, Repurchased Face Amount		400.0
4.500% Senior Notes due 2025
Debt Additional Information
Costs Related to Early Retirement of Debt	$ 67.3
4.500% Senior Notes due 2025 \| Senior Notes
Debt Additional Information
Proceeds from Issuance of Debt		500.0
Secured Notes Issued in 2007 \| Senior Notes
Debt Additional Information
Extinguishment of Debt, Amount		$ 35.0
4.125% Senior Notes due 2051 \| Senior Notes
Debt Additional Information
Proceeds from Issuance of Debt	$ 600.0
Stated Interest Rate of Debt	4.125%
Medium-term Notes \| Medium Term Notes Payable Due 2028
Debt Additional Information
Stated Interest Rate of Debt			7.19%
Extinguishment of Debt, Amount			$ 30.3
Senior Notes \| Notes Issued in 1998 with 2028 Maturity Date
Debt Additional Information
Stated Interest Rate of Debt			7.25%
Extinguishment of Debt, Amount			$ 30.0
Senior Notes \| Senior Notes Payable due 2021
Debt Additional Information
Stated Interest Rate of Debt			3.00%
Extinguishment of Debt, Amount			$ 350.0
Senior Notes \| Notes Issued in 2010
Debt Additional Information
Stated Interest Rate of Debt		5.625%
Senior Notes \| Notes Issued in 2020 due 2025
Debt Additional Information
Stated Interest Rate of Debt		4.50%
Junior Subordinated Debt \| Junior Subordinated Notes Payable Due 2038
Debt Additional Information
Stated Interest Rate of Debt			7.405%
Extinguishment of Debt, Amount			$ 22.8
Junior Subordinated Debt \| Junior Subordinated Notes Payable Due 2038 \| Parent Company
Debt Additional Information
Stated Interest Rate of Debt			7.405%
Extinguishment of Debt, Amount			$ 22.8
Receive Fixed/Pay Variable \| Interest Rate Swaps
Debt Additional Information
Notional Amount Of Derivatives Terminations	$ 0.0	$ 250.0	0.0
Derivative, Notional Amount	$ 0.0	0.0	250.0			$ 250.0
Receive Fixed/Pay Variable \| Interest Rate Swaps \| Parent Company
Debt Additional Information
Derivative, Notional Amount			250.0
Northwind Holdings LLC
Debt Additional Information
Proceeds from Issuance of Senior Long-term Debt				$ 800.0
Periodic Principal Payments		$ 45.0	$ 60.0
Basis Spread on LIBOR				0.78%