Fair Value of Financial Instruments (Carrying Value and Estimated Fair Value) (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Investments
Held-to-maturity securities	$ 196	$ 199
Available-for-sale securities	3,207,872	3,168,542
Trading securities	21,154	20,034
Fair Value
Investments
Mortgage loans	3,817	3,895
Policy loans	5,396	5,366
Other long-term investments	67,024	67,639
Short-term investments	175	175
Cash and cash equivalents	93,656	110,853
Corporate-owned life insurance	3,000	2,592
Policy reserves
Annuity (accumulations)	640,973	646,764
Annuity (benefit payments)	142,968	144,283
Fair Value \| Fixed maturities:
Investments
Held-to-maturity securities	196	199
Available-for-sale securities	2,932,188	2,898,126
Trading securities	14,971	14,390
Fair Value \| Equity securities:
Investments
Available-for-sale securities	275,684	270,416
Trading securities	6,183	5,644
Carrying Value
Investments
Mortgage loans	3,640	3,706
Policy loans	5,396	5,366
Other long-term investments	67,024	67,639
Short-term investments	175	175
Cash and cash equivalents	93,656	110,853
Corporate-owned life insurance	3,000	2,592
Policy reserves
Annuity (accumulations)	649,395	666,711
Annuity (benefit payments)	94,385	95,129
Carrying Value \| Fixed maturities:
Investments
Held-to-maturity securities	195	198
Available-for-sale securities	2,932,188	2,898,126
Trading securities	14,971	14,390
Carrying Value \| Equity securities:
Investments
Available-for-sale securities	275,684	270,416
Trading securities	$ 6,183	$ 5,644

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