Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Contingency [Line Items]
Net tax charge/(benefit) recorded directly to consolidated shareholders' equity	$ 16,200	$ 7,100	$ 3,200
Valuation allowance	3,597	2,460
Base year reserves included in retained earnings	18,200
Unrecognized deferred federal income tax liability	4,800
Amount related to unrecognized tax benefits that if reversed would impact effective tax rate	5,400	6,100
Accrued interest and penalties related to the liability for unrecognized tax benefits	1,500	1,400
Maximum
Income Tax Contingency [Line Items]
Interest and penalties expense/(benefit) related to the liability for unrecognized tax benefits	$ 100	$ 500	$ 100