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Fair Value Measurement (Narrative) (Details) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2022	Dec. 31, 2021
Credit Derivatives [Line Items]
Fair value of funded deferred compensation assets	$ 27,700,000	$ 39,500,000
Fair Value
Credit Derivatives [Line Items]
Deferred compensation liabilities	27,600,000	52,300,000
Fair Value, Nonrecurring
Credit Derivatives [Line Items]
Fair value, net asset (liability)	$ 0	0
NORCAL Group
Credit Derivatives [Line Items]
Fair value of funded deferred compensation assets		5,200,000
NORCAL Group | Fair Value
Credit Derivatives [Line Items]
Deferred compensation liabilities		$ 18,400,000
Other asset-backed securities | NRSRO, Rating A
Credit Derivatives [Line Items]
Credit quality percentage	71.00%
Other asset-backed securities | NRSRO, Rating BBB
Credit Derivatives [Line Items]
Credit quality percentage		100.00%

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+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(17))
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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