Basis of Presentation and Significant Accounting Policies - Deferred Policy Acquisition Costs (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Deferred policy acquisition costs	$ 229,828	$ 276,668
Property and Casualty
Segment Reporting Information [Line Items]
Deferred policy acquisition costs	26,153	28,616
Supplemental
Segment Reporting Information [Line Items]
Deferred policy acquisition costs	4,270	1,967
Retirement
Segment Reporting Information [Line Items]
Deferred policy acquisition costs	137,735	185,294
Life
Segment Reporting Information [Line Items]
Deferred policy acquisition costs	$ 61,670	$ 60,791