Segment Information (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) segment	Jun. 30, 2017 USD ($)
Segment Reporting [Abstract]
Number of reportable segments | segment			3
Revenues
Premium income	$ 78,155	$ 67,663	$ 222,836	$ 219,904
Fee income	286,696	267,338	562,660	522,453
Other revenue	3,077	3,661	6,062	6,045
Net investment income	327,471	297,221	665,612	610,691
Investment gains (losses), net	40,256	22,064	(3,487)	10,310
Total revenues	735,655	657,947	1,453,683	1,369,403
Benefits and expenses:
Policyholder benefits	260,686	269,544	599,270	608,971
Operating expenses	349,090	312,411	666,323	632,494
Total benefits and expenses	609,776	581,955	1,265,593	1,241,465
Income before income taxes	125,879	75,992	188,090	127,938
Income tax expense	27,251	26,168	40,804	43,286
Net income	98,628	49,824	147,286	84,652
Individual Markets
Revenues
Premium income	49,955	44,701	173,540	176,260
Fee income	33,167	29,199	64,795	55,180
Other revenue	0	0	0	0
Net investment income	197,403	192,788	394,732	376,993
Investment gains (losses), net	32,117	4,037	15,447	4,622
Total revenues	312,642	270,725	648,514	613,055
Benefits and expenses:
Policyholder benefits	201,554	198,171	473,562	468,259
Operating expenses	58,422	47,420	101,024	85,807
Total benefits and expenses	259,976	245,591	574,586	554,066
Income before income taxes	52,666	25,134	73,928	58,989
Income tax expense	10,135	8,531	14,033	20,182
Net income	42,531	16,603	59,895	38,807
Empower Retirement
Revenues
Premium income	1,086	1,052	1,675	1,143
Fee income	251,845	236,573	494,302	463,892
Other revenue	3,077	3,661	6,062	6,045
Net investment income	117,289	92,756	246,297	210,375
Investment gains (losses), net	8,138	18,011	(18,984)	5,695
Total revenues	381,435	352,053	729,352	687,150
Benefits and expenses:
Policyholder benefits	53,968	50,702	105,247	98,330
Operating expenses	258,871	249,178	518,752	504,941
Total benefits and expenses	312,839	299,880	623,999	603,271
Income before income taxes	68,596	52,173	105,353	83,879
Income tax expense	16,009	17,996	24,777	28,421
Net income	52,587	34,177	80,576	55,458
Other
Revenues
Premium income	27,114	21,910	47,621	42,501
Fee income	1,684	1,566	3,563	3,381
Other revenue	0	0	0	0
Net investment income	12,779	11,677	24,583	23,323
Investment gains (losses), net	1	16	50	(7)
Total revenues	41,578	35,169	75,817	69,198
Benefits and expenses:
Policyholder benefits	5,164	20,671	20,461	42,382
Operating expenses	31,797	15,813	46,547	41,746
Total benefits and expenses	36,961	36,484	67,008	84,128
Income before income taxes	4,617	(1,315)	8,809	(14,930)
Income tax expense	1,107	(359)	1,994	(5,317)
Net income	$ 3,510	$ (956)	$ 6,815	$ (9,613)