Fair Value of Financial Instruments (Carrying Value and Estimated Fair Value) (Details) - USD ($) $ in Thousands		Sep. 30, 2016	Dec. 31, 2015
Investments
Held-to-maturity securities		$ 655	$ 675
Available-for-sale securities		3,167,565	3,061,208
Trading securities		17,898	16,975
Fair Value
Investments
Mortgage loans		4,063	4,237
Policy loans		5,300	5,618
Other long-term investments		57,787	54,151
Short-term investments		175	175
Cash and cash equivalents		140,944	106,449
Corporate-owned life insurance		2,406	1,716
Policy reserves
Annuity (accumulations)	[1]	702,251	707,190
Annuity (benefit payments)		142,013	131,899
Fair Value | Fixed maturities:
Investments
Held-to-maturity securities		655	675
Available-for-sale securities		2,916,464	2,824,961
Trading securities		13,253	12,622
Fair Value | Equity securities:
Investments
Available-for-sale securities		251,101	236,247
Trading securities		4,645	4,353
Carrying Value
Investments
Mortgage loans		3,772	3,961
Policy loans		5,300	5,618
Other long-term investments		57,787	54,151
Short-term investments		175	175
Cash and cash equivalents		140,944	106,449
Corporate-owned life insurance		2,406	1,716
Policy reserves
Annuity (accumulations)	[1]	685,591	744,931
Annuity (benefit payments)		95,798	95,467
Carrying Value | Fixed maturities:
Investments
Held-to-maturity securities		652	672
Available-for-sale securities		2,916,464	2,824,961
Trading securities		13,253	12,622
Carrying Value | Equity securities:
Investments
Available-for-sale securities		251,101	236,247
Trading securities		$ 4,645	$ 4,353

[1] Annuity accumulations represent deferred annuity contracts that are currently earning interest.