Reinsurance and Indemnification - Michigan Catastrophic Claims Association (Details) - USD ($)	6 Months Ended	12 Months Ended	24 Months Ended
	Jun. 30, 2020	Dec. 31, 2020	Jun. 30, 2022	Jun. 30, 2020	Dec. 31, 2019
Reinsurance Retention Policy [Line Items]
Assets		$ 125,987,000,000			$ 119,950,000,000
Retained income		52,767,000,000			48,074,000,000
Michigan Catastrophic Claim Association
Reinsurance Retention Policy [Line Items]
Reinsurance and indemnification recoverables, net		5,650,000,000			$ 5,500,000,000
Program funding, per vehicle annual assessment		$ 100
Reinsurance increase, percentage		6.00%
Retention level per claim				$ 580,000
Term of catastrophe reinsurance agreement contract				2 years
Assets	$ 23,410,000,000			$ 23,410,000,000
Retained income	2,440,000,000			$ 2,440,000,000
Retained earnings accumulated deficit decrease	$ 34,730,000,000
Subsequent Event | Michigan Catastrophic Claim Association
Reinsurance Retention Policy [Line Items]
Retention level per claim			$ 600,000
Term of catastrophe reinsurance agreement contract			2 years