Notes Payable - Schedule of Long Term Debt (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019	May 16, 2019	Aug. 13, 2018	Aug. 28, 2012
Debt Instrument [Line Items]
Debt	$ 2,430.0	$ 838.0
3.40% Notes, net of discount
Debt Instrument [Line Items]
Debt Instrument, interest rate, stated percentage	3.40%
Debt	$ 643.0	0.0
Term Loan
Debt Instrument [Line Items]
Debt	$ 358.0	0.0
5.50% F& G Notes
Debt Instrument [Line Items]
Debt Instrument, interest rate, stated percentage	5.50%
Debt	$ 589.0	0.0
F&G Credit Facility
Debt Instrument [Line Items]
Debt	$ 0.0	0.0
Unsecured notes | 4.50% Notes, net of discount
Debt Instrument [Line Items]
Debt Instrument, interest rate, stated percentage	4.50%		4.50%	4.50%
Debt	$ 443.0	443.0
Unsecured notes | 5.50% Notes, net of discount
Debt Instrument [Line Items]
Debt Instrument, interest rate, stated percentage	5.50%				5.50%
Debt	$ 399.0	398.0
Line of Credit | Revolving Credit Facility | Revolving Credit Facility
Debt Instrument [Line Items]
Debt	$ 2.0	$ 3.0