Goodwill and Intangible Assets - Finite-lived Intangible Assets (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	$ 14.2	$ 15.8	$ 42.8	$ 51.7
Accumulated Amortization	312.0	299.4	312.0	299.4	$ 314.0
Policies in force
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	256.2	256.2	256.2	256.2	256.2
Accumulated Amortization	201.3	164.7	201.3	164.7	173.9
Net Carrying Amount	54.9	91.5	54.9	91.5	82.3
Agency relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	159.2	159.2	159.2	159.2	159.2
Accumulated Amortization	62.6	51.2	62.6	51.2	54.0
Net Carrying Amount	96.6	108.0	96.6	108.0	105.2
Software rights
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	69.1	79.1	69.1	79.1	79.1
Accumulated Amortization	47.5	48.1	47.5	48.1	50.7
Net Carrying Amount	21.6	31.0	21.6	31.0	28.4
Trade name
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	0.0	34.8	0.0	34.8	34.8
Accumulated Amortization	0.0	34.8	0.0	34.8	34.8
Net Carrying Amount	0.0	0.0	0.0	0.0	0.0
Finite-Lived Intangible Assets
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	484.5	529.3	484.5	529.3	529.3
Accumulated Amortization	311.4	298.8	311.4	298.8	313.4
Net Carrying Amount	$ 173.1	$ 230.5	$ 173.1	$ 230.5	$ 215.9

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

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