Condensed Consolidated Statements of Financial Position (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Fixed maturity, bonds held-to-maturity, at amortized cost	$ 21,385	$ 21,664
Fair value of bonds held-to-maturity	8,501,656	8,968,690
Amortized cost of bonds available-for-sale	6,447,577	6,435,670
Cost of equity securities	693,708	663,058
Mortgage loans on real estate	59,445	19,160
Accumulated depreciation of investment real estate	260,893	256,757
Reinsurance recoverables	17,713
Property and equipment, net of accumulated depreciation	$ 263,857	$ 257,907
Common stock, par value (in usd per share)	$ 1.00	$ 1.00
Common stock, shares authorized (in shares)	50,000,000	50,000,000
Common stock, shares issued (in shares)	30,832,449	30,832,449
Common stock, shares outstanding (in shares)	26,887,200	26,887,200