Segment Information - Additional Significant Financial Information by Segment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
DAC unlocking and amortization expense	$ 109,181	$ 109,889	$ 102,185
Income tax expense (benefit)	52,006	1,194	(80,772)
Property and Casualty
Segment Reporting Information [Line Items]
DAC unlocking and amortization expense	79,453	79,073	76,967
Supplemental
Segment Reporting Information [Line Items]
DAC unlocking and amortization expense	438
Income tax expense (benefit)	5,105
Retirement
Segment Reporting Information [Line Items]
DAC unlocking and amortization expense	21,446	23,186	17,759
Life
Segment Reporting Information [Line Items]
DAC unlocking and amortization expense	7,844	7,630	7,459
Operating Segments | Property and Casualty
Segment Reporting Information [Line Items]
Income tax expense (benefit)	13,954	(6,622)	(3,279)
Operating Segments | Retirement
Segment Reporting Information [Line Items]
Income tax expense (benefit)	33,772	10,000	(19,498)
Operating Segments | Life
Segment Reporting Information [Line Items]
Income tax expense (benefit)	4,907	4,979	(51,876)
Corporate and Other | Corporate and Other
Segment Reporting Information [Line Items]
Income tax expense (benefit)	$ (5,732)	$ (7,163)	$ (6,119)