Fair Value (Tables)

9 Months Ended

Sep. 30, 2017

Fair Value Disclosures [Abstract]

Composition of Investment Portfolio by Major Security Type

The composition of the investment portfolio by major security type and our outstanding debt was:

	Fair Value
(millions)	Level 1		Level 2		Level 3		Total		Cost
September 30, 2017
Fixed maturities:
U.S. government obligations	$	4,595.0	$	0	$	0	$	4,595.0	$	4,612.2
State and local government obligations	0		2,364.2		0		2,364.2		2,332.2
Foreign government obligations	24.2		0		0		24.2		24.2
Corporate debt securities	0		5,225.6		0		5,225.6		5,195.7
Subtotal	4,619.2		7,589.8		0		12,209.0		12,164.3
Asset-backed securities:
Residential mortgage-backed	0		920.3		0		920.3		911.3
Agency residential pass-through obligations	0		35.3		0		35.3		35.7
Commercial mortgage-backed	0		2,767.9		0		2,767.9		2,763.7
Other asset-backed	0		2,490.2		0		2,490.2		2,485.6
Subtotal asset-backed securities	0		6,213.7		0		6,213.7		6,196.3
Redeemable preferred stocks:
Financials	0		63.8		0		63.8		61.4
Utilities	0		31.9		0		31.9		30.5
Industrials	0		141.6		0		141.6		130.6
Subtotal redeemable preferred stocks	0		237.3		0		237.3		222.5
Total fixed maturities	4,619.2		14,040.8		0		18,660.0		18,583.1
Equity securities:
Nonredeemable preferred stocks:
Financials	82.2		726.5		0		808.7		695.6
Industrials	0		0		5.0		5.0		5.0
Subtotal nonredeemable preferred stocks	82.2		726.5		5.0		813.7		700.6
Common equities:
Common stocks	3,209.2		0		0		3,209.2		1,485.2
Other risk investments	0		0		0.3		0.3		0.3
Subtotal common equities	3,209.2		0		0.3		3,209.5		1,485.5
Total fixed maturities and equity securities	7,910.6		14,767.3		5.3		22,683.2		20,769.2
Short-term investments	3,175.4		1,136.1		0		4,311.5		4,311.5
Total portfolio	$	11,086.0	$	15,903.4	$	5.3	$	26,994.7	$	25,080.7
Debt	$	0	$	3,574.6	$	43.3	$	3,617.9	$	3,312.2

	Fair Value
(millions)	Level 1		Level 2		Level 3		Total		Cost
September 30, 2016
Fixed maturities:
U.S. government obligations	$	734.6	$	0	$	0	$	734.6	$	726.0
State and local government obligations	0		2,566.0		0		2,566.0		2,508.9
Foreign government obligations	25.4		0		0		25.4		25.4
Corporate debt securities	0		4,403.3		0		4,403.3		4,327.5
Subtotal	760.0		6,969.3		0		7,729.3		7,587.8
Asset-backed securities:
Residential mortgage-backed	0		1,594.2		0		1,594.2		1,582.6
Agency residential pass-through obligations	0		44.1		0		44.1		43.6
Commercial mortgage-backed	0		2,277.8		0.6		2,278.4		2,249.4
Other asset-backed	0		2,045.4		0		2,045.4		2,037.5
Subtotal asset-backed securities	0		5,961.5		0.6		5,962.1		5,913.1
Redeemable preferred stocks:
Financials	0		95.7		0		95.7		77.1
Utilities	0		30.4		0		30.4		30.6
Industrials	0		99.4		0		99.4		99.4
Subtotal redeemable preferred stocks	0		225.5		0		225.5		207.1
Total fixed maturities	760.0		13,156.3		0.6		13,916.9		13,708.0
Equity securities:
Nonredeemable preferred stocks:
Financials	154.6		705.5		0		860.1		726.6
Industrials	0		0		0		0		0
Subtotal nonredeemable preferred stocks	154.6		705.5		0		860.1		726.6
Common equities:
Common stocks	2,867.6		0		0		2,867.6		1,575.7
Other risk investments	0		0		0.4		0.4		0.4
Subtotal common equities	2,867.6		0		0.4		2,868.0		1,576.1
Total fixed maturities and equity securities	3,782.2		13,861.8		1.0		17,645.0		16,010.7
Short-term investments	5,051.5		824.7		0		5,876.2		5,876.2
Total portfolio	$	8,833.7	$	14,686.5	$	1.0	$	23,521.2	$	21,886.9
Debt	$	0	$	3,371.6	$	133.6	$	3,505.2	$	3,153.9

	Fair Value
(millions)	Level 1		Level 2		Level 3		Total		Cost
December 31, 2016
Fixed maturities:
U.S. government obligations	$	2,870.1	$	0	$	0	$	2,870.1	$	2,899.2
State and local government obligations	0		2,502.6		0		2,502.6		2,509.5
Foreign government obligations	24.5		0		0		24.5		24.5
Corporate debt securities	0		4,550.9		0		4,550.9		4,557.8
Subtotal	2,894.6		7,053.5		0		9,948.1		9,991.0
Asset-backed securities:
Residential mortgage-backed	0		1,458.7		0		1,458.7		1,448.5
Agency residential pass-through obligations	0		40.6		0		40.6		41.2
Commercial mortgage-backed	0		2,253.1		0.3		2,253.4		2,266.9
Other asset-backed	0		2,351.1		0		2,351.1		2,350.7
Subtotal asset-backed securities	0		6,103.5		0.3		6,103.8		6,107.3
Redeemable preferred stocks:
Financials	0		59.5		0		59.5		59.8
Utilities	0		30.9		0		30.9		30.5
Industrials	0		101.5		0		101.5		98.5
Subtotal redeemable preferred stocks	0		191.9		0		191.9		188.8
Total fixed maturities	2,894.6		13,348.9		0.3		16,243.8		16,287.1
Equity securities:
Nonredeemable preferred stocks:
Financials	138.1		715.4		0		853.5		734.2
Industrials	0		0		0		0		0
Subtotal nonredeemable preferred stocks	138.1		715.4		0		853.5		734.2
Common equities:
Common stocks	2,812.0		0		0		2,812.0		1,437.1
Other risk investments	0		0		0.4		0.4		0.4
Subtotal common equities	2,812.0		0		0.4		2,812.4		1,437.5
Total fixed maturities and equity securities	5,844.7		14,064.3		0.7		19,909.7		18,458.8
Short-term investments	3,009.3		563.6		0		3,572.9		3,572.9
Total portfolio	$	8,854.0	$	14,627.9	$	0.7	$	23,482.6	$	22,031.7
Debt	$	0	$	3,188.5	$	127.3	$	3,315.8	$	3,148.2

Summary of Changes in Fair Value Associated With Level 3 Assets

The following tables provide a summary of changes in fair value associated with Level 3 assets for the three and nine months ended September 30, 2017 and 2016:

	Level 3 Fair Value
	Three Months Ended September 30, 2017
(millions)	Fair Value at June 30, 2017		Calls/ Maturities/ Paydowns			Purchases		Sales		Net Realized (Gain) Loss on Sales		Change in Valuation		Net Transfers In (Out)		Fair Value at September 30, 2017
Fixed maturities:
Asset-backed securities:
Commercial mortgage-backed	$	0	$	0		$	0	$	0	$	0	$	0	$	0	$	0
Total fixed maturities	0		0			0		0		0		0		0		0
Equity securities:
Nonredeemable preferred stocks:
Industrials	0		0			5.0		0		0		0		0		5.0
Common equities:
Other risk investments	0.3		0			0		0		0		0		0		0.3
Total Level 3 securities	$	0.3	$	0		$	5.0	$	0	$	0	$	0	$	0	$	5.3
	Level 3 Fair Value
	Nine months ended September 30, 2017
(millions)	Fair Value at Dec. 31, 2016		Calls/ Maturities/ Paydowns			Purchases		Sales		Net Realized (Gain) Loss on Sales		Change in Valuation		Net Transfers In (Out)		Fair Value at September 30, 2017
Fixed maturities:
Asset-backed securities:
Commercial mortgage-backed	$	0.3	$	(0.3	)	$	0	$	0	$	0	$	0	$	0	$	0
Total fixed maturities	0.3		(0.3		)	0		0		0		0		0		0
Equity securities:
Nonredeemable preferred stocks:
Industrials	0		0			5.0		0		0		0		0		5.0
Common equities:
Other risk investments	0.4		(0.1		)	0		0		0		0		0		0.3
Total Level 3 securities	$	0.7	$	(0.4	)	$	5.0	$	0	$	0	$	0	$	0	$	5.3

	Level 3 Fair Value
	Three Months Ended September 30, 2016
(millions)	Fair Value at June 30, 2016		Calls/ Maturities/ Paydowns			Purchases		Sales		Net Realized (Gain) Loss on Sales		Change in Valuation		Net Transfers In (Out)		Fair Value at September 30, 2016
Fixed maturities:
Asset-backed securities:
Commercial mortgage-backed	$	9.2	$	(8.7	)	$	0	$	0	$	0	$	0.1	$	0	$	0.6
Total fixed maturities	9.2		(8.7		)	0		0		0		0.1		0		0.6
Equity securities:
Nonredeemable preferred stocks:
Industrials	0		0			0		0		0		0		0		0
Common equities:
Other risk investments	0.3		0			0		0		0		0.1		0		0.4
Total Level 3 securities	$	9.5	$	(8.7	)	$	0	$	0	$	0	$	0.2	$	0	$	1.0
	Level 3 Fair Value
	Nine months ended September 30, 2016
(millions)	Fair Value at Dec. 31, 2015		Calls/ Maturities/ Paydowns			Purchases		Sales		Net Realized (Gain) Loss on Sales		Change in Valuation		Net Transfers In (Out)		Fair Value at September 30, 2016
Fixed maturities:
Asset-backed securities:
Commercial mortgage-backed	$	9.9	$	(9.3	)	$	0	$	0	$	0	$	0	$	0	$	0.6
Total fixed maturities	9.9		(9.3		)	0		0		0		0		0		0.6
Equity securities:
Nonredeemable preferred stocks:
Industrials	0		0			0		0		0		0		0		0
Common equities:
Other risk investments	0.3		0			0		0		0		0.1		0		0.4
Total Level 3 securities	$	10.2	$	(9.3	)	$	0	$	0	$	0	$	0.1	$	0	$	1.0

Summary of Quantitative Information about Level 3 Fair Value Measurements

The following tables provide a summary of the quantitative information about Level 3 fair value measurements for our applicable securities at September 30, 2017 and 2016, and December 31, 2016:

	Quantitative Information about Level 3 Fair Value Measurements
($ in millions)	Fair Value at September 30, 2017		Valuation Technique	Unobservable Input	Unobservable Input Assumption
Fixed maturities:
Asset-backed securities:
Commercial mortgage-backed	$	0	NA	NA	NA
Total fixed maturities	0
Equity securities:
Nonredeemable preferred stocks:
Industrials1	5.0		Internal price	Purchase price	3.9
Subtotal Level 3 securities	5.0
Pricing exemption securities2	0.3
Total Level 3 securities	$	5.3

NA= Not applicable, since we did not hold any commercial mortgage-backed Level 3 securities at September 30, 2017.

¹The security was internally-priced since it is privately held and it was valued at September 30, 2017 using the purchase price.

²The fair values for these securities were determined with unobservable inputs not reasonably available to us.

	Quantitative Information about Level 3 Fair Value Measurements
($ in millions)	Fair Value at September 30, 2016		Valuation Technique	Unobservable Input	Unobservable Input Assumption
Fixed maturities:
Asset-backed securities:
Commercial mortgage-backed	$	0.6	External vendor	Prepayment rate1	0	%
Total fixed maturities	0.6
Equity securities:
Nonredeemable preferred stocks:
Industrials	0		NA	NA	NA
Subtotal Level 3 securities	0.6
Pricing exemption securities2	0.4
Total Level 3 securities	$	1.0

NA= Not applicable, since we did not hold any nonredeemable preferred stock Level 3 securities at September 30, 2016.

¹Assumes that one security has 0% of the principal amount of the underlying loans that will be paid off prematurely in each year.

² The fair values for these securities were determined with unobservable inputs not reasonably available to us.

	Quantitative Information about Level 3 Fair Value Measurements
($ in millions)	Fair Value at Dec. 31, 2016		Valuation Technique	Unobservable Input	Unobservable Input Assumption
Fixed maturities:
Asset-backed securities:
Commercial mortgage-backed	$	0.3	External vendor	Prepayment rate1	0	%
Total fixed maturities	0.3
Equity securities:
Nonredeemable preferred stocks:
Industrials	0		NA	NA	NA
Subtotal Level 3 securities	0.3
Pricing exemption securities2	0.4
Total Level 3 securities	$	0.7

NA= Not applicable, since we did not hold any nonredeemable preferred stock Level 3 securities at December 31, 2016.

¹Assumes that one security has 0% of the principal amount of the underlying loans that will be paid off prematurely in each year.

² The fair values for these securities were determined with unobservable inputs not reasonably available to us.