Investments (Tables)

12 Months Ended

Dec. 31, 2020

Investments Debt And Equity Securities [Abstract]

Schedule of Available-for-sale Fixed Maturities Reconciliation

The amortized cost and fair value of available-for-sale fixed maturities were as follows:

DECEMBER 31, 2020
(in millions)
	Amortized Cost		Allowance for Credit Losses			Amortized Cost, Net of Allowance for Credit Losses		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
U.S. Treasury and government agencies	$	376.4	$	—		$	376.4	$	17.6	$	2.0	$	392.0
Foreign government		2.2		—			2.2		0.5		—		2.7
Municipal		1,042.1		—			1,042.1		61.7		0.1		1,103.7
Corporate		3,770.0		(0.1	)		3,769.9		341.8		0.4		4,111.3
Residential mortgage-backed		978.2		—			978.2		33.1		0.6		1,010.7
Commercial mortgage-backed		705.4		—			705.4		54.8		0.2		760.0
Asset-backed		71.4		—			71.4		2.6		—		74.0
Total fixed maturities	$	6,945.7	$	(0.1	)	$	6,945.6	$	512.1	$	3.3	$	7,454.4

DECEMBER 31, 2019
(in millions)			Gross		Gross				OTTI
	Amortized		Unrealized		Unrealized				Unrealized
	Cost		Gains		Losses		Fair Value		Losses(1)
U.S. Treasury and government agencies	$	342.0	$	9.1	$	1.3	$	349.8	$	—
Foreign government		15.7		0.4		—		16.1		—
Municipal		807.1		27.6		1.2		833.5		—
Corporate		3,653.5		161.6		3.9		3,811.2		3.0
Residential mortgage-backed		905.4		17.1		1.1		921.4		—
Commercial mortgage-backed		666.4		25.6		0.1		691.9		—
Asset-backed		62.1		1.1		—		63.2		—
Total fixed maturities	$	6,452.2	$	242.5	$	7.6	$	6,687.1	$	3.0

(1) Other-than-temporary impairments (“OTTI”) unrealized losses represents OTTI recognized in accumulated other comprehensive income. This amount excludes net unrealized gains on impaired securities relating to changes in the value of such securities subsequent to the impairment measurement date through December 31, 2019 of $4.2 million.

Investments Classified by Contractual Maturity Date

The amortized cost and fair value by maturity periods for fixed maturities are shown in the following table. Actual maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties, or the Company may have the right to put or sell the obligations back to the issuers.

DECEMBER 31	2020
(in millions)	Amortized Cost, net of Allowance for Credit Losses		Fair Value
Due in one year or less	$	334.1	$	339.1
Due after one year through five years		1,774.6		1,913.3
Due after five years through ten years		2,306.3		2,548.2
Due after ten years		775.6		809.1
		5,190.6		5,609.7
Mortgage-backed and asset-backed securities		1,755.0		1,844.7
Total fixed maturities	$	6,945.6	$	7,454.4

Unrealized Gains and Losses on Available-for-Sale and Other Securities

Unrealized gains and losses on available-for-sale and other securities are summarized in the following table.

YEARS ENDED DECEMBER 31
(in millions)				Equity
	Fixed			Securities and
2020	Maturities			Other			Total
Net appreciation, beginning of year	$	216.0		$	—		$	216.0
Net appreciation on available-for-sale securities		280.2			—			280.2
Provision for deferred income taxes		(68.1	)		—			(68.1	)
		212.1			—			212.1
Net appreciation, end of year	$	428.1		$	—		$	428.1
2019
Net depreciation, beginning of year	$	(27.2	)	$	—		$	(27.2	)
Net appreciation on available-for-sale securities		324.7			—			324.7
Provision for deferred income taxes		(83.0	)		—			(83.0	)
Cumulative effect adjustment for ASU 2017-08, net of tax		1.5			—			1.5
		243.2			—			243.2
Net appreciation, end of year	$	216.0		$	—		$	216.0
2018
Net appreciation, beginning of year	$	110.1		$	95.3		$	205.4
Net depreciation on available-for-sale securities		(203.7	)		—			(203.7	)
Provision for deferred income taxes		33.6			—			33.6
Amount realized with sale of Chaucer, net of tax		19.1			—			19.1
Cumulative effect adjustment for ASUs 2016-01 and 2018-02, net of tax		13.7			(95.3	)		(81.6	)
		(137.3	)		(95.3	)		(232.6	)
Net depreciation, end of year	$	(27.2	)	$	—		$	(27.2	)

Schedule of Unrealized Loss on Investments

The following tables provide information about the Company’s available-for-sale fixed maturity securities that were in an unrealized loss position at December 31, 2020 and 2019 including the length of time the securities have been in an unrealized loss position:

DECEMBER 31, 2020	12 months or less				Greater than 12 months				Total
(in millions)	Gross				Gross				Gross
	Unrealized		Fair		Unrealized		Fair		Unrealized		Fair
	Losses		Value		Losses		Value		Losses		Value
Investment grade:
U.S. Treasury and government agencies	$	2.0	$	140.7	$	—	$	—	$	2.0	$	140.7
Municipal		0.1		19.3		—		0.7		0.1		20.0
Corporate		0.4		53.4		—		—		0.4		53.4
Residential mortgage-backed		0.6		94.4		—		—		0.6		94.4
Commercial mortgage-backed		0.2		33.2		—		—		0.2		33.2
Total investment grade		3.3		341.0		—		0.7		3.3		341.7
Below investment grade:
Corporate		—		4.6		—		—		—		4.6
Total fixed maturities	$	3.3	$	345.6	$	—	$	0.7	$	3.3	$	346.3

DECEMBER 31, 2019	12 months or less				Greater than 12 months				Total
(in millions)	Gross				Gross				Gross
	Unrealized		Fair		Unrealized		Fair		Unrealized		Fair
	Losses		Value		Losses		Value		Losses		Value
Investment grade:
U.S. Treasury and government agencies	$	1.3	$	73.0	$	—	$	9.3	$	1.3	$	82.3
Municipal		1.1		72.5		0.1		5.6		1.2		78.1
Corporate		0.7		86.5		0.1		4.7		0.8		91.2
Residential mortgage-backed		0.7		69.2		0.4		34.4		1.1		103.6
Commercial mortgage-backed		0.1		40.6		—		0.9		0.1		41.5
Asset-backed		—		—		—		1.7		—		1.7
Total investment grade		3.9		341.8		0.6		56.6		4.5		398.4
Below investment grade:
Corporate		2.2		27.1		0.9		9.0		3.1		36.1
Total fixed maturities	$	6.1	$	368.9	$	1.5	$	65.6	$	7.6	$	434.5

Schedule of Other Investments

Mortgage participations and other mortgage loans were comprised of the following property types and geographic locations

DECEMBER 31	2020			2019
(in millions)
Property Type:
Office	$	160.4		$	138.2
Apartments		128.3			125.1
Retail		68.5			66.5
Hotel		62.7			62.1
Industrial		55.6			50.6
Valuation allowance		(7.9	)		(1.3	)
Total	$	467.6		$	441.2

DECEMBER 31	2020			2019
(in millions)
Geographic Region:
Pacific	$	117.0		$	102.3
South Atlantic		108.3			95.9
Mid-Atlantic		73.8			53.3
West South Central		70.8			71.2
New England		43.5			42.5
East North Central		27.8			27.8
Mountain		12.5			12.5
Other		21.8			37.0
Valuation allowance		(7.9	)		(1.3	)
Total	$	467.6		$	441.2