Segments (Tables)

12 Months Ended

Dec. 31, 2021

Segment Reporting [Abstract]

Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Table Text Block]

	Employers		Cerity		Corporate and Other		Total
	(in millions)
Year Ended December 31, 2021
Gross premiums written	$	588.2	$	1.5	$	—	$	589.7
Net premiums written	581.6		1.5		—		583.1
Net premiums earned	573.7		0.7		—		574.4
Net investment income	69.3		2.8		0.6		72.7
Net realized and unrealized gains on investments	54.5		0.3		(0.2)		54.6
Other income	1.4		—		—		1.4
Total revenues	698.9		3.8		0.4		703.1
Losses and loss adjustment expenses	326.2		0.5		(11.5)		315.2
Commission expense	76.1		—		—		76.1
Underwriting and general and administrative expenses	131.2		12.9		16.1		160.2
Interest and financing expenses	—		—		0.5		0.5
Other expenses	4.1		—		—		4.1
Total expenses	537.6		13.4		5.1		556.1
Net income (loss) before income taxes	$	161.3	$	(9.6)	$	(4.7)	$	147.0

	Employers		Cerity		Corporate and Other		Total
	(in millions)
Year Ended December 31, 2020
Gross premiums written	$	579.8	$	0.3	$	—	$	580.1
Net premiums written	574.6		0.3		—		574.9
Net premiums earned	615.1		0.2		—		615.3
Net investment income	72.1		3.1		1.1		76.3
Net realized and unrealized gains on investments	20.9		—		(1.9)		19.0
Other income	0.8		—		—		0.8
Total revenues	708.9		3.3		(0.8)		711.4
Losses and loss adjustment expenses	314.2		0.1		(11.9)		302.4
Commission expense	78.8		—		—		78.8
Underwriting and general and administrative expenses	151.1		16.6		13.6		181.3
Interest and financing expenses	0.1		—		0.3		0.4
Other expenses	0.7		0.1		—		0.8
Total expenses	544.9		16.8		2.0		563.7
Net income (loss) before income taxes	$	164.0	$	(13.5)	$	(2.8)	$	147.7

	Employers		Cerity		Corporate and Other		Total
	(in millions)
Year Ended December 31, 2019
Gross premiums written	$	696.8	$	0.1	$	—	$	696.9
Net premiums written	691.4		0.1		—		691.5
Net premiums earned	695.8		—		—		695.8
Net investment income	84.1		0.3		3.7		88.1
Net realized and unrealized gains on investments	47.7		0.1		3.3		51.1
Other income	0.9		—		—		0.9
Total revenues	828.5		0.4		7.0		835.9
Losses and loss adjustment expenses	378.6		—		(12.7)		365.9
Commission expense	88.1		—		—		88.1
Underwriting and general and administrative expenses	153.2		16.0		18.3		187.5
Interest and financing expenses	0.6		—		—		0.6
Total expenses	620.5		16.0		5.6		642.1
Net income (loss) before income taxes	$	208.0	$	(15.6)	$	1.4	$	193.8

Revenue from External Customers by Geographic Areas [Table Text Block]

	2021			2020			2019
State	In-force Premiums		Policies In-force	In-force Premiums		Policies In-force	In-force Premiums		Policies In-force
	(dollars in millions)
California	$	258.4	40,704	$	262.0	39,610	$	329.8	43,079
Florida	41.1		7,989	37.9		6,898	36.3		5,822
New York	24.5		7,307	26.7		6,657	31.7		5,679
Other (43 states and D.C.)	247.4		55,350	251.3		50,341	266.8		44,104
Total	$	571.4	111,350	$	577.9	103,506	$	664.6	98,684