Recoverable from Reinsurers (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Ceded Credit Risk [Line Items]
Amount	$ 958.4	$ 953.7
Percentage of Total, Reinsurance recoverable | Reinsurer Concentration Risk
Ceded Credit Risk [Line Items]
Percentage of total	100.00%	100.00%
Hannover Life Reassurance Company of America | A+
Ceded Credit Risk [Line Items]
Amount	$ 320.6	$ 323.3
Hannover Life Reassurance Company of America | A+ | Percentage of Total, Reinsurance recoverable | Reinsurer Concentration Risk
Ceded Credit Risk [Line Items]
Percentage of total	33.50%	33.90%
Munich American Reassurance Company | A+
Ceded Credit Risk [Line Items]
Amount	$ 354.3	$ 347.6
Munich American Reassurance Company | A+ | Percentage of Total, Reinsurance recoverable | Reinsurer Concentration Risk
Ceded Credit Risk [Line Items]
Percentage of total	37.00%	36.40%
ManhattanLife Assurance Company of America | B+
Ceded Credit Risk [Line Items]
Amount	$ 46.2	$ 47.0
ManhattanLife Assurance Company of America | B+ | Percentage of Total, Reinsurance recoverable | Reinsurer Concentration Risk
Ceded Credit Risk [Line Items]
Percentage of total	4.80%	4.90%
Loyal American Life Insurance Company | A
Ceded Credit Risk [Line Items]
Amount	$ 148.6	$ 147.5
Loyal American Life Insurance Company | A | Percentage of Total, Reinsurance recoverable | Reinsurer Concentration Risk
Ceded Credit Risk [Line Items]
Percentage of total	15.50%	15.50%
Great American Life Insurance Company | A
Ceded Credit Risk [Line Items]
Amount	$ 57.2	$ 56.2
Great American Life Insurance Company | A | Percentage of Total, Reinsurance recoverable | Reinsurer Concentration Risk
Ceded Credit Risk [Line Items]
Percentage of total	6.00%	5.90%
Other
Ceded Credit Risk [Line Items]
Amount	$ 31.5	$ 32.1
Other | Percentage of Total, Reinsurance recoverable | Reinsurer Concentration Risk
Ceded Credit Risk [Line Items]
Percentage of total	3.20%	3.40%