Consolidated Statements of Financial Position (Parenthetical) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Investments:
Fixed maturities available-for-sale, cost	$ 935,977,000	$ 860,473,000
Fixed maturities held-to-maturity, fair value	241,377,000	252,545,000
Available-for-sale equity securities, amortized cost basis	15,289,000	17,765,000
Real estate held for investment, accumulated depreciation	5,479,000	1,083,000
Real estate held for sale, accumulated depreciation	0	1,008,000
Due premiums, allowance for doubtful accounts	$ 1,611,000	$ 1,600,000
Common Stock Class A [Member]
Stockholders' equity:
Common stock, par value (in dollars per share)	$ 0	$ 0
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	52,215,852	52,215,852
Common stock, shares outstanding (in shares)	52,215,852	52,215,852
Common stock, shares in treasury (in shares)	3,135,738	3,135,738
Common Stock Class B [Member]
Stockholders' equity:
Common stock, par value (in dollars per share)	$ 0	$ 0
Common stock, shares authorized (in shares)	2,000,000	2,000,000
Common stock, shares issued (in shares)	1,001,714	1,001,714
Common stock, shares outstanding (in shares)	1,001,714	1,001,714