Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 item	Sep. 30, 2012
Segment Information
Number of reportable segments			3
Revenue:
Premium income	$ 137,401	$ 140,032	$ 382,080	$ 343,510
Fee income	152,343	132,202	453,596	394,305
Other revenue			7,355
Net investment income	375,041	299,675	909,006	892,942
Realized investment gains (losses), net	(55,820)	59,041	(65,395)	112,581
Total revenues	608,965	630,950	1,686,642	1,743,338
Benefits and expenses:
Policyholder benefits	334,464	333,722	944,329	928,489
Operating expenses	169,243	177,856	540,401	520,653
Total benefits and expenses, net	503,707	511,578	1,484,730	1,449,142
Income before income taxes	105,258	119,372	201,912	294,196
Income tax expense (benefit)	33,287	48,797	67,159	107,673
Net income	71,971	70,575	134,753	186,523
Individual Markets
Revenue:
Premium income	120,489	112,109	303,073	257,868
Fee income	20,018	17,909	67,393	54,806
Other revenue			7,355
Net investment income	201,727	184,977	551,167	547,791
Realized investment gains (losses), net	(12,797)	23,679	3,957	44,469
Total revenues	329,437	338,674	932,945	904,934
Benefits and expenses:
Policyholder benefits	261,716	250,666	715,691	685,510
Operating expenses	33,768	32,007	107,178	98,540
Total benefits and expenses, net	295,484	282,673	822,869	784,050
Income before income taxes	33,953	56,001	110,076	120,884
Income tax expense (benefit)	10,716	18,787	38,349	40,605
Net income	23,237	37,214	71,727	80,279
Retirement Services
Revenue:
Premium income	1,484	1,742	2,669	3,608
Fee income	131,103	113,083	382,809	335,864
Net investment income	159,547	102,831	320,179	309,635
Realized investment gains (losses), net	(43,023)	35,362	(69,365)	68,078
Total revenues	249,111	253,018	636,292	717,185
Benefits and expenses:
Policyholder benefits	53,201	52,392	146,562	154,770
Operating expenses	123,810	128,707	385,039	370,064
Total benefits and expenses, net	177,011	181,099	531,601	524,834
Income before income taxes	72,100	71,919	104,691	192,351
Income tax expense (benefit)	22,866	23,731	33,509	63,588
Net income	49,234	48,188	71,182	128,763
Other
Revenue:
Premium income	15,428	26,181	76,338	82,034
Fee income	1,222	1,210	3,394	3,635
Net investment income	13,767	11,867	37,660	35,516
Realized investment gains (losses), net			13	34
Total revenues	30,417	39,258	117,405	121,219
Benefits and expenses:
Policyholder benefits	19,547	30,664	82,076	88,209
Operating expenses	11,665	17,142	48,184	52,049
Total benefits and expenses, net	31,212	47,806	130,260	140,258
Income before income taxes	(795)	(8,548)	(12,855)	(19,039)
Income tax expense (benefit)	(295)	6,279	(4,699)	3,480
Net income	$ (500)	$ (14,827)	$ (8,156)	$ (22,519)