Income Taxes - Reconciliation of Effective Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Expected federal tax on income	$ 49,654	$ 4,103	$ 31,041
Add (deduct) tax effects of:
Tax-exempt interest	(4,159)	(3,726)	(5,335)
Dividend received deduction	(1,392)	(412)	(4,810)
Goodwill impairment	5,885	0	0
Tax Act DTL re-measurement	0	0	(98,988)
Employee share-based compensation	272	(1,134)	(3,258)
Compensation deduction limitation	680	1,754	326
Prior year adjustments	(716)	300	(293)
Other, net	1,782	309	545
Total income tax expense (benefit)	$ 52,006	$ 1,194	$ (80,772)

Effective Tax Rate Reconciliation, Nondeductible Expense, Compensation Deduction Limitation, Amount

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Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Change In Tax Rate, Deferred Tax Liability, Provisional Income Tax (Expense) Benefit

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