Income Taxes - Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets
Unearned premium reserve reduction	$ 12,103	$ 12,112
Compensation accruals	8,866	6,866
Reinsurance commissions	6,804
Impaired securities	1,245	1,295
Other comprehensive income - net funded status of benefit plans	2,875	3,254
Discounting of unpaid claims and claim expense tax reserves	2,530	2,772
Postretirement benefits other than pensions	285	302
Charitable contributions carryforwards	0	89
Net operating loss carryforwards	3,803	10,969
Total gross deferred tax assets	38,511	37,659
Deferred tax liabilities
Other comprehensive income - net unrealized gains on securities	74,645	32,897
Deferred policy acquisition costs	49,326	60,330
Life insurance future policy benefit reserve	38,210	9,304
Life insurance future policy benefit reserve (transitional rule)	12,786	14,910
Discounting of unpaid claims and claim expense tax reserves (transitional rule)	947	1,203
Investment related adjustments	15,718	17,531
Intangibles	2,021	2,557
Other, net	5,482	2,613
Total gross deferred tax liabilities	199,135	141,345
Net deferred tax liability	$ 160,624	$ 103,686