General (Details) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Aug. 31, 2017 USD ($) a	Sep. 30, 2017 USD ($) shares	Sep. 30, 2016 USD ($) shares	Sep. 30, 2017 USD ($) shares	Sep. 30, 2016 USD ($) shares
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Potentially dilutive securities (in shares) | shares		0	22,000	0	29,000
Deferred policy acquisition cost amortization		$ 136,290	$ 140,203	$ 416,728	$ 421,685
Advertising expenses				32,000	34,100
Property, Plant and Equipment [Line Items]
Sale of land, gain				$ 3,307	$ 0
Brea, California [Member]
Property, Plant and Equipment [Line Items]
Area of land (in acres) | a	6
Sale of land, sales price	$ 12,200
Sale of land, Promissory note receivable	5,700
Sale of land, gain	$ 3,300
Brea, California [Member] | Note Receivable [Member]
Property, Plant and Equipment [Line Items]
Interest rate	3.50%