Statutory Information and Restrictions (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended												12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Reconciliations of statutory capital and surplus
Statutory capital and surplus of insurance subsidiaries	$ 809,241				$ 754,153								$ 809,241	$ 754,153
Increase (decrease) due to:
Deferred policy acquisition costs	245,355				196,885								245,355	196,885
Difference in policyholder reserves	80,459				67,582								80,459	67,582
Goodwill	47,396				47,396								47,396	47,396
Liability for postretirement benefits other than pensions	(1,130)				(2,862)								(1,130)	(2,862)
Investment fair value adjustments on fixed maturities	227,060				651,071								227,060	651,071
Difference in investment reserves	111,983				101,276								111,983	101,276
Federal income tax liability	(188,426)				(317,875)								(188,426)	(317,875)
Net funded status of pension and other postretirement benefit obligations	(18,217)				(23,862)								(18,217)	(23,862)
Non-admitted assets and other, net	11,349				10,660								11,349	10,660
Shareholders' equity (deficit) of parent company and non-insurance subsidiaries	12,109				(812)								12,109	(812)
Parent company short-term and long-term debt	(237,874)				(237,809)								(237,874)	(237,809)
Total shareholders' equity	1,099,305				1,245,803				1,055,353				1,099,305	1,245,803	1,055,353
Reconciliations of statutory net income
Statutory net income of insurance subsidiaries													98,905	93,299	63,986
Net loss of non-insurance companies													(4,583)	(4,726)	(10,164)
Interest expense													(14,236)	(14,249)	(14,007)
Tax benefit of interest expense and other parent company current tax adjustments													6,030	9,308	4,603
Combined net income													86,116	83,632	44,418
Increase (decrease) due to:
Deferred policy acquisition costs													17,177	16,595	8,989
Policyholder benefits													19,038	15,574	14,428
Federal income tax expense													(12,735)	(19,843)	(6,639)
Investment reserves													6,818	14,021	9,903
Other adjustments, net													(5,521)	(6,113)	(593)
Net income	$ 34,287	$ 23,599	$ 25,995	$ 27,012	$ 31,826	$ 32,266	$ 13,103	$ 26,671	$ 32,913	$ 23,637	$ (11,851)	$ 25,807	$ 110,893	$ 103,866	$ 70,506