Insurance Operations - Insurance Pool (Details) - Information pertaining to reinsurance for umbrella casualty insurance and ocean marine liability insurance.	12 Months Ended
	Dec. 31, 2019 USD ($)
Minimum
Reinsurance Retention Policy [Line Items]
Net retention per occurrence after applicable reinsurance	$ 250,000
Effective pool participation (as a percent)	11.00%
Maximum
Reinsurance Retention Policy [Line Items]
Net retention per occurrence after applicable reinsurance	$ 2,000,000
Effective pool participation (as a percent)	59.00%