Loss and Loss Adjustment Expense Reserves - TPC Participation (Details)	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Ark | Amount attributable to TPC Providers
Liability for Claims and Claims Adjustment Expense [Line Items]
Percent of underwriting capital provided by third parties	0.00%	42.80%	58.30%	57.60%	60.00%	59.60%	70.00%	66.20%	0.00%	0.00%