Fair Value of Financial Instruments (Carrying Value and Estimated Fair Value) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Investments
Available-for-sale securities	$ 3,003,259		$ 2,985,205
Fair Value [Member]
Investments
Mortgage loans	4,800		5,037
Policy loans	6,566		6,671
Other long-term investments	30,646		30,028
Short-term investments	800		800
Cash and cash equivalents	101,948		107,466
Accrued investment income	30,079		30,375
Policy reserves
Annuity (accumulations)	1,022,644	[1]	1,043,866	[1]
Annuity (benefit payments)	139,757		139,213
Fair Value [Member] | Fixed Maturities [Member]
Investments
Held-to-maturity fixed maturities	1,668		1,681
Available-for-sale securities	2,807,582		2,808,078
Trading securities	13,738		13,353
Fair Value [Member] | Equity Securities [Member]
Investments
Available-for-sale securities	195,677		177,127
Trading securities	2,131		2,018
Carrying Value [Member]
Investments
Mortgage loans	4,581		4,633
Policy loans	6,566		6,671
Other long-term investments	30,646		30,028
Short-term investments	800		800
Cash and cash equivalents	101,948		107,466
Accrued investment income	30,079		30,375
Policy reserves
Annuity (accumulations)	963,017	[1]	983,579	[1]
Annuity (benefit payments)	93,170		93,701
Carrying Value [Member] | Fixed Maturities [Member]
Investments
Held-to-maturity fixed maturities	1,638		1,655
Available-for-sale securities	2,807,582		2,808,078
Trading securities	13,738		13,353
Carrying Value [Member] | Equity Securities [Member]
Investments
Available-for-sale securities	195,677		177,127
Trading securities	$ 2,131		$ 2,018

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