Liabilities for Outstanding Claims, Losses and Loss Adjustment Expenses (Tables)

12 Months Ended

Dec. 31, 2020

Insurance [Abstract]

Schedule of Liability for Unpaid Losses and Loss Adjustment Expenses

The table below provides a reconciliation of the gross beginning and ending reserve for unpaid losses and loss adjustment expenses.

YEARS ENDED DECEMBER 31	2020			2019			2018
(in millions)
Gross reserve for losses and LAE, beginning of year	$	5,654.4		$	5,304.1		$	5,058.5
Reinsurance recoverable on unpaid losses		1,574.8			1,472.6			1,455.0
Net loss and LAE reserves, beginning of year		4,079.6			3,831.5			3,603.5
Net incurred losses and LAE in respect of losses    occurring in:
Current year		2,877.8			2,893.0			2,733.5
Prior years		(32.6	)		(28.4	)		(8.9	)
Total incurred losses and LAE		2,845.2			2,864.6			2,724.6
Net payments of losses and LAE in respect of losses    occurring in:
Current year		1,347.7			1,315.4			1,232.3
Prior years		1,194.7			1,301.1			1,264.3
Total payments		2,542.4			2,616.5			2,496.6
Net reserve for losses and LAE, end of year		4,382.4			4,079.6			3,831.5
Reinsurance recoverable on unpaid losses		1,641.6			1,574.8			1,472.6
Gross reserve for losses and LAE, end of year	$	6,024.0		$	5,654.4		$	5,304.1

Schedule of (Favorable)/Unfavorable Loss and LAE Reserve Development

The following table provides a summary of (favorable)/unfavorable loss and LAE reserve development.

YEARS ENDED DECEMBER 31	2020			2019			2018
(in millions)
Commercial multiple peril	$	(0.2	)	$	(19.5	)	$	(4.0	)
Workers’ compensation		(36.0	)		(32.6	)		(31.0	)
Commercial automobile		15.4			5.8			23.2
Other commercial lines:
Hanover Programs		10.6			19.8			17.0
General liability		0.3			(7.8	)		(27.9	)
Marine		(17.6	)		(13.3	)		(10.7	)
Surety		(3.5	)		(4.1	)		(9.0	)
Umbrella		(1.5	)		2.8			2.3
Other lines		(5.3	)		(4.4	)		(0.8	)
Total other commercial lines		(17.0	)		(7.0	)		(29.1	)
Total Commercial Lines		(37.8	)		(53.3	)		(40.9	)
Personal automobile		5.2			21.6			14.3
Homeowners and other personal lines		(4.2	)		2.1			16.5
Total Personal Lines		1.0			23.7			30.8
Total Other Segment		4.2			1.2			1.2
Total loss and LAE reserve development, including    catastrophes	$	(32.6	)	$	(28.4	)	$	(8.9	)

Schedule of Carried Reserves

The table below summarizes the gross, ceded and net reserve for losses and LAE and reconciles to the incurred claims development in the following section. Accordingly, the commercial multiple peril, workers’ compensation, commercial automobile liability and general liability and umbrella - occurrence lines presentation includes Hanover Programs business.

YEAR ENDED DECEMBER 31,	2020							2019
(in millions)	Gross		Ceded			Net		Gross		Ceded			Net
Commercial multiple peril	$	1,429.4	$	(163.9	)	$	1,265.5	$	1,298.5	$	(126.5	)	$	1,172.0
Workers’ compensation		795.4		(182.6	)		612.8		795.3		(186.0	)		609.3
Commercial automobile liability		504.1		(30.6	)		473.5		467.7		(27.3	)		440.4
General liability and umbrella - occurrence		612.0		(176.0	)		436.0		575.9		(155.5	)		420.4
General liability - claims made		323.7		(30.5	)		293.2		268.1		(20.1	)		248.0
Other lines		451.6		(85.1	)		366.5		409.5		(89.5	)		320.0
Total Commercial Lines and other		4,116.2		(668.7	)		3,447.5		3,815.0		(604.9	)		3,210.1
Personal automobile liability		1,649.9		(968.5	)		681.4		1,626.4		(963.2	)		663.2
Homeowners		210.6		(3.0	)		207.6		172.4		(4.8	)		167.6
Other personal lines		47.3		(1.4	)		45.9		40.6		(1.9	)		38.7
Total Personal Lines		1,907.8		(972.9	)		934.9		1,839.4		(969.9	)		869.5
Total loss and LAE reserves	$	6,024.0	$	(1,641.6	)	$	4,382.4	$	5,654.4	$	(1,574.8	)	$	4,079.6

Schedule of Incurred Claims Development

Commercial multiple peril
($ in millions)																	As of
Incurred Losses and ALAE, Net of Reinsurance																	December 31, 2020
YEARS ENDED DECEMBER 31,																			Cumulative
																			Incurred
Accident	2013		2014		2015														Claim
Year	Unaudited		Unaudited		Unaudited		2016		2017		2018		2019		2020		IBNR		Count
2013	$	380.0	$	362.5	$	367.9	$	391.8	$	392.1	$	393.0	$	393.7	$	393.6	$	7.8		14,801
2014				443.9		439.6		464.8		459.4		449.1		444.4		441.0		13.1		15,881
2015						446.0		456.3		463.7		467.4		465.2		460.9		16.9		15,583
2016								447.1		449.6		448.7		447.4		449.6		25.8		15,750
2017										538.7		544.8		551.6		555.6		38.5		16,638
2018												578.2		560.9		556.1		77.8		17,123
2019														583.8		593.0		138.0		16,012
2020																628.9		245.5		13,136
Total															$	4,078.7
Cumulative Paid Losses and ALAE, Net of Reinsurance
YEARS ENDED DECEMBER 31,
Accident	2013		2014		2015
Year	Unaudited		Unaudited		Unaudited		2016		2017		2018		2019		2020
2013	$	137.6	$	221.5	$	262.3	$	306.4	$	334.6	$	355.9	$	366.3	$	373.1
2014				171.7		267.8		316.0		363.4		395.2		407.7		411.7
2015						161.9		260.1		315.6		363.2		397.0		413.6
2016								140.3		237.9		290.2		342.2		369.6
2017										170.9		296.4		370.6		422.9
2018												178.8		306.2		363.7
2019														169.3		317.2
2020																217.4
Total																2,889.2
Total reserves for 2013 – 2020 accident years (incurred - paid)																1,189.5
Total reserves for 2012 and prior accident years																51.9
Unallocated loss adjustment expense																24.1
Net reserves at December 31, 2020															$	1,265.5

Workers' compensation
($ in millions)																					As of
Incurred Losses and ALAE, Net of Reinsurance																					December 31, 2020
YEARS ENDED DECEMBER 31,																							Cumulative
																							Incurred
Accident	2011		2012		2013		2014		2015														Claim
Year	Unaudited		Unaudited		Unaudited		Unaudited		Unaudited		2016		2017		2018		2019		2020		IBNR		Count
2011	$	141.4	$	144.2	$	144.3	$	145.5	$	143.8	$	146.7	$	148.3	$	147.9	$	147.7	$	146.9	$	6.3		12,484
2012				176.3		171.1		165.2		157.2		162.9		163.7		163.7		161.9		161.4		8.4		13,083
2013						179.3		167.4		160.1		154.4		155.3		155.4		154.9		153.3		8.8		11,734
2014								182.1		172.9		154.7		152.1		150.3		148.2		145.8		11.8		10,943
2015										189.6		164.2		157.5		150.3		146.0		142.7		16.0		11,485
2016												189.6		180.5		164.6		158.2		152.8		16.1		15,894
2017														186.1		172.1		160.8		156.6		20.0		16,722
2018																187.2		182.1		172.1		24.2		17,454
2019																		187.9		182.0		30.1		17,163
2020																				182.5		76.9		12,549
Total																			$	1,596.1
Cumulative Paid Losses and ALAE, Net of Reinsurance
YEARS ENDED DECEMBER 31,
Accident	2011		2012		2013		2014		2015
Year	Unaudited		Unaudited		Unaudited		Unaudited		Unaudited		2016		2017		2018		2019		2020
2011	$	30.0	$	71.3	$	97.3	$	114.0	$	122.9	$	128.0	$	130.9	$	132.8	$	134.2	$	135.3
2012				30.4		74.8		102.6		120.1		130.7		136.0		141.4		143.7		146.6
2013						30.9		74.6		101.2		114.0		122.8		127.4		131.4		133.8
2014								30.6		70.5		92.3		105.6		112.5		117.8		121.0
2015										28.0		65.7		87.2		99.4		105.8		109.6
2016												33.9		78.1		99.5		111.1		117.1
2017														32.8		73.0		94.1		106.6
2018																35.6		80.7		103.4
2019																		33.3		83.1
2020																				30.7
Total																				1,087.2
Total reserves for 2011 – 2020 accident years (incurred - paid)																				508.9
Total reserves for 2010 and prior accident years																				84.6
Unallocated loss adjustment expense and other																				19.3
Net reserves at December 31, 2020																			$	612.8

Commercial automobile liability
($ in millions)														As of
Incurred Losses and ALAE, Net of Reinsurance														December 31, 2020
YEARS ENDED DECEMBER 31,																Cumulative
																Incurred
Accident	2014	2015														Claim
Year	Unaudited	Unaudited		2016		2017		2018		2019		2020		IBNR		Count
2014	168.5	$	163.3	$	177.3	$	181.7	$	185.1	$	185.0	$	183.5	$	1.7		13,477
2015			163.4		168.3		166.9		167.8		167.6		170.3		1.2		12,829
2016					157.0		157.7		163.0		174.3		172.5		4.3		11,660
2017							159.5		170.1		182.1		188.5		7.6		11,504
2018									182.8		176.1		182.9		25.5		11,181
2019											180.5		192.0		57.0		10,210
2020													171.6		115.9		5,772
Total												$	1,261.3
Cumulative Paid Losses and ALAE, Net of Reinsurance
YEARS ENDED DECEMBER 31,
Accident	2014	2015
Year	Unaudited	Unaudited		2016		2017		2018		2019		2020
2014	33.1	$	70.8	$	102.7	$	137.1	$	168.2	$	176.3	$	178.2
2015			32.2		63.8		96.4		129.3		144.5		152.5
2016					27.8		60.7		98.3		134.0		147.2
2017							26.9		71.2		105.9		137.7
2018									29.2		59.7		92.5
2019											29.5		75.8
2020													23.4
Total													807.3
Total reserves for 2014 – 2020 accident years (incurred - paid)													454.0
Total reserves for 2013 and prior accident years													13.7
Unallocated loss adjustment expense													5.8
Net reserves at December 31, 2020												$	473.5

General liability and umbrella - occurrence
($ in millions)																					As of
Incurred Losses and ALAE, Net of Reinsurance																					December 31, 2020
YEARS ENDED DECEMBER 31,																							Cumulative
																							Incurred
Accident	2011		2012		2013		2014		2015														Claim
Year	Unaudited		Unaudited		Unaudited		Unaudited		Unaudited		2016		2017		2018		2019		2020		IBNR		Count
2011	$	47.6	$	43.8	$	38.2	$	42.2	$	51.0	$	55.6	$	55.4	$	57.5	$	58.8	$	59.3	$	2.4		1,393
2012				77.2		59.3		62.2		64.3		71.1		74.2		69.1		71.2		72.8		2.5		1,774
2013						84.1		67.4		71.5		88.6		84.4		81.2		80.4		79.1		4.1		2,001
2014								100.9		82.3		98.6		101.4		98.3		99.8		98.4		6.4		2,108
2015										104.2		99.3		99.6		97.0		98.3		99.7		9.9		2,448
2016												95.6		100.7		101.5		100.8		98.7		15.7		1,913
2017														97.7		107.6		109.2		110.7		24.9		1,806
2018																99.8		106.4		104.0		35.2		1,823
2019																		104.2		105.7		55.8		1,605
2020																				99.8		81.0		1,213
Total																			$	928.2
Cumulative Paid Losses and ALAE, Net of Reinsurance
YEARS ENDED DECEMBER 31,
Accident	2011		2012		2013		2014		2015
Year	Unaudited		Unaudited		Unaudited		Unaudited		Unaudited		2016		2017		2018		2019		2020
2011		1.6	$	6.7	$	19.4	$	31.1	$	39.8	$	45.8	$	47.8	$	50.6	$	52.9	$	54.8
2012				2.2		12.6		29.8		43.8		52.1		60.6		63.0		64.5		65.0
2013						2.4		11.0		26.8		43.1		56.1		63.5		67.6		70.1
2014								3.1		14.5		31.4		52.8		70.4		83.6		87.3
2015										3.3		15.2		30.8		48.5		65.7		77.3
2016												3.1		15.0		31.6		52.5		63.4
2017														4.4		17.0		34.5		49.8
2018																4.1		15.6		35.7
2019																		7.5		16.7
2020																				3.9
Total																				524.0
Total reserves for 2011 – 2020 accident years (incurred - paid)																				404.2
Total reserves for 2010 and prior accident years																				18.1
Unallocated loss adjustment expense and other																				13.7
Net reserves at December 31, 2020																			$	436.0

General liability - claims made
($ in millions)															As of
Incurred Losses and ALAE, Net of Reinsurance															December 31, 2020
YEARS ENDED DECEMBER 31,																	Cumulative
																	Incurred
Accident	2014		2015														Claim
Year	Unaudited		Unaudited		2016		2017		2018		2019		2020		IBNR		Count
2014	$	61.7	$	69.9	$	83.9	$	86.2	$	82.5	$	82.9	$	82.4	$	0.9		906
2015				93.2		98.8		98.4		90.2		90.3		91.0		1.9		1,002
2016						103.6		101.7		97.1		89.7		95.2		4.7		1,011
2017								103.3		104.6		98.1		96.0		8.8		1,122
2018										120.9		127.8		132.5		14.3		1,386
2019												126.8		127.1		31.7		1,554
2020														142.8		76.3		2,514
Total													$	767.0
Cumulative Paid Losses and ALAE, Net of Reinsurance
YEARS ENDED DECEMBER 31,
Accident	2014		2015
Year	Unaudited		Unaudited		2016		2017		2018		2019		2020
2014	$	11.0	$	38.8	$	59.1	$	71.5	$	75.4	$	79.1	$	79.9
2015				10.0		43.6		64.2		76.0		81.8		83.7
2016						11.1		42.9		66.1		75.5		80.4
2017								12.3		42.3		67.2		76.5
2018										17.3		56.1		87.5
2019												17.8		56.7
2020														18.1
Total														482.8
Total reserves for 2014 – 2020 accident years (incurred - paid)														284.2
Total reserves for 2013 and prior accident years														3.8
Unallocated loss adjustment expense														5.1
Net reserves at December 31, 2020													$	293.1

Personal automobile liability
($ in millions)											As of
Incurred Losses and ALAE, Net of Reinsurance											December 31, 2020
YEARS ENDED DECEMBER 31,													Cumulative
													Incurred
Accident													Claim
Year	2016		2017		2018		2019		2020		IBNR		Count
2016		337.9		344.5		355.3		365.8	$	367.7	$	4.2		42,375
2017				363.6		362.3		383.4		392.2		9.7		42,993
2018						394.2		395.3		400.3		23.9		42,841
2019								431.2		431.8		67.0		41,703
2020										378.0		199.2		24,339
Total									$	1,970.0
Cumulative Paid Losses and ALAE, Net of Reinsurance
YEARS ENDED DECEMBER 31,
Accident
Year	2016		2017		2018		2019		2020
2016	$	112.8	$	213.1	$	288.0	$	329.4	$	346.3
2017				115.0		229.2		302.7		343.8
2018						121.7		237.2		307.4
2019								131.0		262.2
2020										95.9
Total										1,355.6
Total reserves for 2016 – 2020 accident years (incurred - paid)										614.4
Total reserves for 2015 and prior accident years										51.7
Unallocated loss adjustment expense										15.3
Net reserves at December 31, 2020									$	681.4

Homeowners
($ in millions)									As of
Incurred Losses and ALAE, Net of Reinsurance									December 31, 2020
YEARS ENDED DECEMBER 31,											Cumulative
											Incurred
Accident											Claim
Year	2017		2018		2019		2020		IBNR		Count
2017	$	291.4	$	296.5	$	297.3	$	295.2		0.6		33,474
2018				312.9		316.2		317.3		6.1		32,725
2019						344.5		345.3		14.3		33,582
2020								418.8		77.2		31,392
Total							$	1,376.6
Cumulative Paid Losses and ALAE, Net of Reinsurance
YEARS ENDED DECEMBER 31,
Accident
Year	2017		2018		2019		2020
2017	$	204.5	$	271.6	$	283.5	$	289.0
2018				213.7		290.1		300.8
2019						234.7		311.7
2020								281.5
Total								1,183.0
Total reserves for 2017 – 2020 accident years (incurred - paid)								193.6
Total reserves for 2016 and prior accident years								10.5
Unallocated loss adjustment expense								3.4
Net reserves at December 31, 2020							$	207.5

Computation of Historical Claims on Paid and Incurred Claims Data, Net of Reinsurance

The following table is information about average historical claims duration as of December 31, 2020. The table is computed based on the paid and incurred claims data, net of reinsurance, for the accident years presented in the preceding claims development tables.

Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance:
Unaudited
	1			2			3			4			5			6			7			8			9			10
Commercial multiple peril		33.3	%		22.4	%		11.4	%		10.7	%		7.0	%		4.0	%		1.8	%		1.7	%
Workers' compensation		19.9	%		27.4	%		15.4	%		9.1	%		5.2	%		3.2	%		2.5	%		1.4	%		1.3	%		0.7	%
Commercial automobile liability		16.0	%		20.4	%		18.9	%		18.9	%		11.2	%		4.5	%		1.0	%
General liability and umbrella    - occurrence		3.7	%		11.1	%		18.7	%		19.1	%		14.8	%		11.3	%		3.9	%		3.3	%		2.3	%		3.3	%
General liability - claims made		12.7	%		32.5	%		24.3	%		11.9	%		5.4	%		3.3	%		0.9	%
Personal automobile liability		29.2	%		28.9	%		18.9	%		10.9	%		4.6	%
Homeowners		68.0	%		23.0	%		3.7	%		1.8	%