Investments (Tables)

6 Months Ended

Jun. 30, 2018

Investments Debt And Equity Securities [Abstract]

Schedule of Available-for-sale Securities Reconciliation

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

	June 30, 2018
			Gross		Gross				OTTI
	Amortized		Unrealized		Unrealized				Unrealized
(in millions)	Cost		Gains		Losses		Fair Value		Losses
U.S. Treasury and government agencies	$	595.1	$	1.7	$	16.3	$	580.5	$	—
Foreign government		209.6		2.1		2.2		209.5		—
Municipal		1,035.3		17.9		15.5		1,037.7		—
Corporate		4,278.7		38.9		101.3		4,216.3		6.6
Residential mortgage-backed		1,026.7		1.8		31.5		997.0		—
Commercial mortgage-backed		624.0		1.0		13.4		611.6		—
Asset-backed		78.4		-		1.1		77.3		—
Total fixed maturities	$	7,847.8	$	63.4	$	181.3	$	7,729.9	$	6.6

	December 31, 2017
			Gross		Gross				OTTI
	Amortized		Unrealized		Unrealized				Unrealized
(in millions)	Cost		Gains		Losses		Fair Value		Losses
U.S. Treasury and government agencies	$	513.6	$	3.4	$	5.6	$	511.4	$	—
Foreign government		240.8		3.2		1.3		242.7		—
Municipal		1,053.3		29.8		7.1		1,076.0		—
Corporate		4,238.9		95.0		26.4		4,307.5		6.9
Residential mortgage-backed		990.6		6.5		11.1		986.0		—
Commercial mortgage-backed		591.7		7.2		2.5		596.4		—
Asset-backed		59.9		0.1		0.3		59.7		—
Total fixed maturities	$	7,688.8	$	145.2	$	54.3	$	7,779.7	$	6.9

Investments Classified by Contractual Maturity Date

The amortized cost and fair value by maturity periods for fixed maturities are shown below. 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.

	June 30, 2018
	Amortized		Fair
(in millions)	Cost		Value
Due in one year or less	$	408.2	$	409.7
Due after one year through five years		2,789.5		2,784.6
Due after five years through ten years		2,589.6		2,515.2
Due after ten years		331.4		334.5
		6,118.7		6,044.0
Mortgage-backed and asset-backed securities		1,729.1		1,685.9
Total fixed maturities	$	7,847.8	$	7,729.9

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 June 30, 2018 and December 31, 2017 including the length of time the securities have been in an unrealized loss position:

	June 30, 2018
	12 months or less				Greater than 12 months				Total
	Gross				Gross				Gross
	Unrealized		Fair		Unrealized		Fair		Unrealized		Fair
(in millions)	Losses		Value		Losses		Value		Losses		Value
Investment grade:
U.S. Treasury and government    agencies	$	10.0	$	393.6	$	6.3	$	103.2	$	16.3	$	496.8
Foreign governments		1.3		86.6		0.9		52.5		2.2		139.1
Municipal		8.5		390.7		7.0		126.6		15.5		517.3
Corporate		57.2		2,343.5		33.1		480.1		90.3		2,823.6
Residential mortgage-backed		13.1		512.5		18.4		347.4		31.5		859.9
Commercial mortgage-backed		10.4		445.6		3.0		61.2		13.4		506.8
Asset-backed		1.0		56.6		0.1		1.6		1.1		58.2
Total investment grade		101.5		4,229.1		68.8		1,172.6		170.3		5,401.7
Below investment grade:
Municipal		—		0.9		—		—		—		0.9
Corporate		4.6		151.0		6.4		38.1		11.0		189.1
Total below investment grade		4.6		151.9		6.4		38.1		11.0		190.0
Total fixed maturities	$	106.1	$	4,381.0	$	75.2	$	1,210.7	$	181.3	$	5,591.7

	December 31, 2017
	12 months or less				Greater than 12 months				Total
	Gross				Gross				Gross
	Unrealized		Fair		Unrealized		Fair		Unrealized		Fair
(in millions)	Losses		Value		Losses		Value		Losses		Value
Investment grade:
U.S. Treasury and government    agencies	$	2.1	$	282.1	$	3.5	$	103.1	$	5.6	$	385.2
Foreign governments		0.9		99.4		0.4		22.8		1.3		122.2
Municipal		2.1		257.5		5.0		133.1		7.1		390.6
Corporate		5.6		799.6		12.3		481.3		17.9		1,280.9
Residential mortgage-backed		2.0		272.9		9.1		362.4		11.1		635.3
Commercial mortgage-backed		0.9		139.3		1.6		63.2		2.5		202.5
Asset-backed		0.3		34.5		—		2.5		0.3		37.0
Total investment grade		13.9		1,885.3		31.9		1,168.4		45.8		3,053.7
Below investment grade:
Corporate		1.7		53.2		6.8		43.5		8.5		96.7
Total fixed maturities	$	15.6	$	1,938.5	$	38.7	$	1,211.9	$	54.3	$	3,150.4

Schedule of Realized Gain (Loss)

The proceeds from sales of available-for-sale securities and gross realized gains and gross realized losses on those sales were as follows:

	Three Months Ended June 30,
	2018						2017
	Proceeds from		Gross		Gross		Proceeds from		Gross		Gross
(in millions)	Sales		Gains		Losses		Sales		Gains		Losses
Fixed maturities	$	164.6	$	1.7	$	2.5	$	132.5	$	3.1	$	0.4

	Six Months Ended June 30,
	2018						2017
	Proceeds from		Gross		Gross		Proceeds from		Gross		Gross
(in millions)	Sales		Gains		Losses		Sales		Gains		Losses
Fixed maturities	$	292.4	$	2.3	$	4.8	$	230.1	$	5.2	$	1.4

Rollforward of Cumulative Amounts Related to Credit Loss Portion of OTTI Losses

The following table provides rollforwards of the cumulative amounts related to the Company’s credit loss portion of the OTTI losses on fixed maturity securities for which the non-credit portion of the loss is included in other comprehensive income.

	Three Months Ended June 30,						Six Months Ended June 30,
(in millions)	2018			2017			2018			2017
Credit losses at beginning of period	$	3.3		$	9.9		$	3.9		$	10.0
Credit losses for which an OTTI was not previously recognized		0.7			0.2			0.9			0.2
Additional credit losses on securities for which an OTTI was    previously recognized		0.1			0.1			0.1			0.1
Reductions for securities sold, matured or called		(0.1	)		(0.6	)		(0.9	)		(0.7	)
Credit losses at end of period	$	4.0		$	9.6		$	4.0		$	9.6

Schedule of Pre-tax Realized and Unrealized Gains and Losses on Equity Securities Recognized in Net Income

The following table provides pre-tax realized and unrealized gains (losses) on equity securities recognized in net income during the three and six months ended June 30, 2018:

(in millions)	Three Months Ended			Six Months Ended
Net gains (losses) recognized during the period	$	6.0		$	(17.0	)
Less: net losses recognized on equity securities sold during the period		(1.3	)		(0.8	)
Net unrealized gains (losses) recognized during the period on equity securities still held	$	7.3		$	(16.2	)