Segment Information (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($) segment	Mar. 31, 2017 USD ($)
Segment Reporting [Abstract]
Number of reportable segments | segment	3
Revenues
Premium income	$ 144,682	$ 152,241
Fee income	275,964	255,116
Other revenue	2,985	2,384
Net investment income	338,141	313,471
Realized investment gains (losses), net	(43,743)	(11,754)
Total revenues	718,029	711,458
Benefits and expenses:
Policyholder benefits	338,585	339,428
Operating expenses	317,233	320,083
Total benefits and expenses	655,818	659,511
Income before income taxes	62,211	51,947
Income tax expense	13,553	17,117
Net income	48,658	34,830
Individual Markets
Revenues
Premium income	123,586	131,559
Fee income	31,628	25,981
Other revenue	0	0
Net investment income	197,329	184,205
Realized investment gains (losses), net	(16,670)	584
Total revenues	335,873	342,329
Benefits and expenses:
Policyholder benefits	272,010	270,088
Operating expenses	42,602	38,386
Total benefits and expenses	314,612	308,474
Income before income taxes	21,261	33,855
Income tax expense	3,897	11,650
Net income	17,364	22,205
Empower Retirement
Revenues
Premium income	589	91
Fee income	242,457	227,320
Other revenue	2,985	2,384
Net investment income	129,009	117,620
Realized investment gains (losses), net	(27,122)	(12,316)
Total revenues	347,918	335,099
Benefits and expenses:
Policyholder benefits	51,279	47,629
Operating expenses	259,881	255,764
Total benefits and expenses	311,160	303,393
Income before income taxes	36,758	31,706
Income tax expense	8,768	10,426
Net income	27,990	21,280
Other
Revenues
Premium income	20,507	20,591
Fee income	1,879	1,815
Other revenue	0	0
Net investment income	11,803	11,646
Realized investment gains (losses), net	49	(22)
Total revenues	34,238	34,030
Benefits and expenses:
Policyholder benefits	15,296	21,711
Operating expenses	14,750	25,933
Total benefits and expenses	30,046	47,644
Income before income taxes	4,192	(13,614)
Income tax expense	888	(4,959)
Net income	$ 3,304	$ (8,655)