Fair Value of Financial Instruments (Carrying Value and Estimated Fair Value) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Investments
Held-to-maturity securities	$ 192	$ 199
Available-for-sale securities	3,231,385	3,168,542
Trading securities	22,440	20,034
Fair Value
Investments
Mortgage loans	3,765	3,895
Policy loans	5,499	5,366
Other long-term investments	65,664	67,639
Short-term investments	175	175
Cash and cash equivalents	130,421	110,853
Corporate-owned life insurance	3,244	2,592
Policy reserves
Annuity (accumulations)	629,169	646,764
Annuity (benefit payments)	143,925	144,283
Fair Value \| Fixed maturities:
Investments
Held-to-maturity securities	192	199
Available-for-sale securities	2,955,079	2,898,126
Trading securities	15,828	14,390
Fair Value \| Equity securities:
Investments
Available-for-sale securities	276,306	270,416
Trading securities	6,612	5,644
Carrying Value
Investments
Mortgage loans	3,573	3,706
Policy loans	5,499	5,366
Other long-term investments	65,664	67,639
Short-term investments	175	175
Cash and cash equivalents	130,421	110,853
Corporate-owned life insurance	3,244	2,592
Policy reserves
Annuity (accumulations)	631,070	666,711
Annuity (benefit payments)	94,323	95,129
Carrying Value \| Fixed maturities:
Investments
Held-to-maturity securities	192	198
Available-for-sale securities	2,955,079	2,898,126
Trading securities	15,828	14,390
Carrying Value \| Equity securities:
Investments
Available-for-sale securities	276,306	270,416
Trading securities	$ 6,612	$ 5,644

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