Fair Value of Financial Instruments (Carrying Value and Estimated Fair Value) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011
Investments
Available-for-sale securities	$ 2,985,205		$ 2,854,931
Fair Value [Member]
Investments
Mortgage loans	5,037		5,219
Policy loans	6,671		7,209
Other long-term investments	30,028		20,574
Short-term investments	800		1,100
Cash and cash equivalents	107,466		144,527
Accrued investment income	30,375		32,219
Policy reserves
Annuity (accumulations)	1,043,866	[1]	1,074,661	[1]
Annuity (benefit payments)	139,213		133,921
Debt	0		45,000
Fair Value [Member] | Fixed Maturities [Member]
Investments
Held-to-maturity fixed maturities	1,681		4,161
Available-for-sale securities	2,808,078		2,697,248
Trading securities	13,353		13,454
Fair Value [Member] | Equity Securities [Member]
Investments
Available-for-sale securities	177,127		157,683
Trading securities	2,018		1,768
Carrying Value [Member]
Investments
Mortgage loans	4,633		4,829
Policy loans	6,671		7,209
Other long-term investments	30,028		20,574
Short-term investments	800		1,100
Cash and cash equivalents	107,466		144,527
Accrued investment income	30,375		32,219
Policy reserves
Annuity (accumulations)	983,579	[1]	999,534	[1]
Annuity (benefit payments)	93,701		94,465
Debt	0		45,000
Carrying Value [Member] | Fixed Maturities [Member]
Investments
Held-to-maturity fixed maturities	1,655		4,143
Available-for-sale securities	2,808,078		2,697,248
Trading securities	13,353		13,454
Carrying Value [Member] | Equity Securities [Member]
Investments
Available-for-sale securities	177,127		157,683
Trading securities	$ 2,018		$ 1,768

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