Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018
Assets
Cash and cash equivalents		$ 32.9	$ 62.6
Investments, at fair value		1,957.9	1,576.2
Other receivables		29.3	46.6
Assets of consolidated investment entities	[1]	2,020.1	1,685.4
Liabilities
Collateralized loan obligation notes, at fair value		1,603.1	1,316.7
Other liabilities		83.9	138.4
Liabilities of consolidated investment entities	[1]	1,687.0	1,455.1
Fixed maturity securities available for sale, amortized cost		$ 11,064.8	$ 10,834.0
Preferred stock, dividend rate		6.50%	6.50%
Preferred stock, par value (in dollars per share)		$ 1.00	$ 1.0
Preferred stock, shares authorized (in shares)		2,875,000	2,875,000
Preferred stock, shares issued (in shares)		2,875,000	2,875,000
Preferred stock, shares outstanding (in shares)		2,875,000	2,875,000
Common stock, par value (in dollars per share)		$ 0.01	$ 0.01
Common stock, shares authorized (in shares)		800,000,000	800,000,000
Common stock shares issued (in shares)		161,607,866	161,153,454
Common stock, shares outstanding (in shares)		59,945,893	61,908,979
Treasury stock, at cost (in shares)		101,661,973	99,244,475

[1] The following table presents information on assets and liabilities related to consolidated investment entities as of December 31, 2019 and 2018.   December 31,   2019   2018   (in millions) Assets       Cash and cash equivalents $ 32.9
  $ 62.6
Investments, at fair value 1,957.9
  1,576.2
Other receivables 29.3
  46.6
Total assets $ 2,020.1
  $ 1,685.4
Liabilities       Collateralized loan obligation notes, at fair value $ 1,603.1
  $ 1,316.7
Other liabilities 83.9
  138.4
Total liabilities $ 1,687.0
  $ 1,455.1