General (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Potentially dilutive securities (in shares)	0	85,000	0	71,000
Common stock dividends (in dollars per share)	$ 0.6275	$ 0.6250	$ 1.2550	$ 1.2500
Deferred policy acquisition cost amortization	$ 148,629,000	$ 141,520,000	$ 297,042,000	$ 282,504,000
Advertising expenses	10,000,000.0	8,800,000	23,600,000	22,500,000
Reinsurance policy, amount of coverage			590,000,000
Reinsurance policy, amount retained			40,000,000
Ceded premiums earned	16,000,000	12,000,000	31,000,000	25,000,000
Policyholder benefits and claims incurred, ceded	6,000,000	(2,000,000)	(52,000,000)	(1,000,000)
Revenue from contract with customer	4,200,000	4,000,000.0	8,400,000	8,300,000
Cost of goods and services sold	2,700,000	$ 2,600,000	5,400,000	$ 5,400,000
Contract with customer, asset	0		0		$ 0
Contract with customer, liability	0		0		0
Revenue, remaining performance obligation	$ 0		$ 0		$ 0