Basis of Presentation and Significant Accounting Policies - Property and Casualty Insurance and Reinsurance (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
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [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%