Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Other fee income	$ 42,597		$ 130,525
Total Fee Income	290,790	$ 264,304	853,450	$ 786,758
Customer contract receivables	247,428		247,428		$ 234,256
Deferred contract costs	45,842		45,842
Administration, recordkeeping and servicing fees
Disaggregation of Revenue [Line Items]
Fees	173,502		501,003
Investment advisory and asset management fees
Disaggregation of Revenue [Line Items]
Fees	74,691		221,922
Individual Markets
Disaggregation of Revenue [Line Items]
Other fee income	26,963		82,757
Total Fee Income	31,984	27,780	96,778	82,960
Individual Markets | Administration, recordkeeping and servicing fees
Disaggregation of Revenue [Line Items]
Fees	1,263		3,565
Individual Markets | Investment advisory and asset management fees
Disaggregation of Revenue [Line Items]
Fees	3,758		10,456
Empower Retirement
Disaggregation of Revenue [Line Items]
Other fee income	15,634		47,768
Total Fee Income	257,038	234,957	751,341	698,850
Empower Retirement | Administration, recordkeeping and servicing fees
Disaggregation of Revenue [Line Items]
Fees	172,239		497,438
Empower Retirement | Investment advisory and asset management fees
Disaggregation of Revenue [Line Items]
Fees	69,165		206,135
Other
Disaggregation of Revenue [Line Items]
Other fee income	0		0
Total Fee Income	1,768	$ 1,567	5,331	$ 4,948
Other | Administration, recordkeeping and servicing fees
Disaggregation of Revenue [Line Items]
Fees	0		0
Other | Investment advisory and asset management fees
Disaggregation of Revenue [Line Items]
Fees	$ 1,768		$ 5,331