Business Combinations - Accounting for Acquisitions (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2019	Aug. 01, 2019	Dec. 31, 2017
Amounts Recognized as of Acquisition Date
Identifiable intangible assets, customer relationships			$ 6.5
Net Assets Acquired			38.5
Goodwill	$ 1,459.7	$ 1,477.0	$ 7.5	$ 1,323.0
NACP Combination And PFP Acquisition
Amounts Recognized as of Acquisition Date
Purchase Price	1,200.8
Assumed Debt	660.0
Total Purchase Consideration	1,860.8
Receivables, Net	145.3
Inventories, Net	315.0
Other Current Assets	11.7
Property, Plant and Equipment, Net	1,274.6
Identifiable intangible assets, customer relationships	150.1
Other Assets	0.0
Total Assets Acquired	1,896.7
Accounts Payable	112.6
Compensation and Employee Benefits	15.3
Current Liabilities	17.9
Other Noncurrent Liabilities	37.0
Total Liabilities Assumed	182.8
Net Assets Acquired	1,713.9
Goodwill	146.9
Total Estimated Fair Value of Net Assets Acquired	1,860.8
Business Acquisition, Measurement Period Adjustments [Abstract]
Total Purchase Consideration	(40.9)
Receivables, Net	0.0
Inventories, Net	0.8
Other Current Assets	(9.2)
Property, Plant and Equipment, Net	32.0
Intangible Assets, Net	13.5
Other Assets	(6.0)
Total Assets Acquired	31.1
Accounts Payable	0.0
Compensation and Employee Benefits	(5.7)
Current Liabilities	(0.1)
Other Noncurrent Liabilities	(1.7)
Total Liabilities Assumed	(7.5)
Net Assets Acquired	38.6
Goodwill	(79.5)
Total Estimated Fair Value of Net Assets Acquired	$ (40.9)
Weighted average useful life of intangible assets	20 years
Acquired Finite-Lived Intangible Assets, Attrition rate	5.00%
NACP Combination And PFP Acquisition | Previously Reported
Amounts Recognized as of Acquisition Date
Purchase Price	$ 1,241.7
Assumed Debt	660.0
Total Purchase Consideration	1,901.7
Receivables, Net	145.3
Inventories, Net	314.2
Other Current Assets	20.9
Property, Plant and Equipment, Net	1,242.6
Identifiable intangible assets, customer relationships	136.6
Other Assets	6.0
Total Assets Acquired	1,865.6
Accounts Payable	112.6
Compensation and Employee Benefits	21.0
Current Liabilities	18.0
Other Noncurrent Liabilities	38.7
Total Liabilities Assumed	190.3
Net Assets Acquired	1,675.3
Goodwill	226.4
Total Estimated Fair Value of Net Assets Acquired	1,901.7
Business Acquisition, Measurement Period Adjustments [Abstract]
Purchase Price	(40.9)
NACP Combination
Amounts Recognized as of Acquisition Date
Total Purchase Consideration	1,800.0
Business Acquisition, Measurement Period Adjustments [Abstract]
Adjustment for discounting the purchase price for lack of marketability	123.5
Adjustments related to working capital tru-ups offset by pension settlements	$ 40.5