Investments In Unconsolidated Affiliates - Changes In Accounting Principle (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Equity in losses of unconsolidated affiliates, net of tax		$ (26.0)	$ (12.7)	$ (20.4)	$ (26.0)
Net earnings		39.1	32.6	89.2	58.6
Unrealized loss on investments in unconsolidated affiliates	[1]	$ (1.5)	$ (2.2)	$ (1.7)	$ (2.4)
Basic (in dollars per share)		$ 0.26	$ 0.22	$ 0.60	$ 0.40
Diluted (in dollars per share)		$ 0.26	$ 0.22	$ 0.60	$ 0.39
Elimination of One-Quarter Lag
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Equity in losses of unconsolidated affiliates, net of tax			$ (12.7)		$ (26.0)
Net earnings			32.6		58.6
Unrealized loss on investments in unconsolidated affiliates			$ (2.2)		$ (2.4)
Basic (in dollars per share)			$ 0.22		$ 0.40
Diluted (in dollars per share)			$ 0.22		$ 0.39
Elimination of One-Quarter Lag | As reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Equity in losses of unconsolidated affiliates, net of tax			$ (13.4)		$ (13.4)
Net earnings			31.9		71.2
Unrealized loss on investments in unconsolidated affiliates			$ (0.2)		$ (0.2)
Basic (in dollars per share)			$ 0.22		$ 0.48
Diluted (in dollars per share)			$ 0.21		$ 0.48

[1] Net of income tax benefit of $0.5 million and $0.6 million for the three and six months ended June 30, 2020, respectively, and $0.8 million and $0.9 million for the three and six months ended June 30, 2019, respectively.