Segment Information - Additional Significant Financial Information by Segment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
DAC unlocking and amortization expense	$ 99,909	$ 109,181	$ 109,889
Income tax benefit	26,268	52,006	1,194
Property and Casualty
Segment Reporting Information [Line Items]
DAC unlocking and amortization expense	74,452	79,453	79,073
Property and Casualty | Operating Segments
Segment Reporting Information [Line Items]
Income tax benefit	15,380	13,954	(6,622)
Supplemental
Segment Reporting Information [Line Items]
DAC unlocking and amortization expense	1,287	438
Income tax benefit	11,972	5,105
Retirement
Segment Reporting Information [Line Items]
DAC unlocking and amortization expense	16,718	21,446	23,186
Retirement | Operating Segments
Segment Reporting Information [Line Items]
Income tax benefit	2,105	33,772	10,000
Life
Segment Reporting Information [Line Items]
DAC unlocking and amortization expense	7,452	7,844	7,630
Life | Operating Segments
Segment Reporting Information [Line Items]
Income tax benefit	2,428	4,907	4,979
Corporate and Other | Corporate and Other
Segment Reporting Information [Line Items]
Income tax benefit	$ (5,617)	$ (5,732)	$ (7,163)