Income Taxes Textuals (Details) $ in Millions, $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Apr. 01, 2017 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2019 AUD ($)	Dec. 22, 2017
Investments, Owned, Federal Income Tax Note [Line Items]
Alternative Minimum Tax Refund				$ 45.7
Remeasurement due to the Tax Cuts and Jobs Act	$ 0.0	$ 473.5		0.0	$ 9.5
Global intangible low-taxed income	0.0	0.0		6.1	68.2
Deferred Tax Assets, Operating Loss Carryforwards, Foreign				14.5
Deferred Tax Assets, Operating Loss Carryforwards, Domestic				2,500.0
Tax Credit Carryforward, Amount				1,500.0
Deferred Tax Assets, Operating Loss Carryforwards, Domestic, Net				530.6
Deferred Tax Assets, Operating Loss Carryforwards, State and Local				81.5
Deferred Tax Assets, Tax Credit Carryforwards, Alternative Minimum Tax				23.4
Deferred Tax Assets, Tax Credit Carryforwards, General Business				112.6
Valuation allowance, income tax				(2,068.4)	(2,094.3)
Unrecognized Tax Benefits, Period Increase (Decrease)				2.5
Net Unrecognized Tax Benefit				16.5	14.0
Unrecognized Tax Benefits, Interest and penalties on Income Taxes Expense	2.1	4.8		0.4	0.4
Unrecognized Tax Benefits, Interest on Income Taxes Accrued				5.8	5.4
Deferred Income Taxes and Tax Credits	(262.3)	(99.6)		39.4	35.5
Income tax provision (benefit)	$ (263.8)	$ (161.0)		46.0	$ 18.4
Australia
Investments, Owned, Federal Income Tax Note [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, Foreign						$ 3,200.0
Deferred Tax Assets, Operating Loss Carryforwards, Foreign, Net				766.4
US and Australia Deferred Tax Assets [Domain]
Investments, Owned, Federal Income Tax Note [Line Items]
Valuation allowance, income tax				(2,100.0)
US Deferred Tax Assets
Investments, Owned, Federal Income Tax Note [Line Items]
Valuation allowance, income tax				(900.0)
Australia Deferred Tax Assets
Investments, Owned, Federal Income Tax Note [Line Items]
Valuation allowance, income tax				$ (1,200.0)
Before Corporate Tax Rate Change
Investments, Owned, Federal Income Tax Note [Line Items]
Federal Corporate Tax Rate							35.00%
After Corporate Tax Rate Change
Investments, Owned, Federal Income Tax Note [Line Items]
Federal Corporate Tax Rate							21.00%
Scenario, Forecast
Investments, Owned, Federal Income Tax Note [Line Items]
Alternative Minimum Tax Refund			$ 23.4
Unrecognized Tax Benefits, Period Increase (Decrease)			$ 5.3