Debt - Settlement of debt (Details) - USD ($) $ in Millions	3 Months Ended
Jun. 30, 2021	Jun. 30, 2020
Debt Instrument [Line Items]
Cash Paid	$ 1,000.0	$ 0.0
Loss on settlement of debt	(0.3)	$ (26.8)
3.922% 2021 Notes \| Senior Indebtedness
Debt Instrument [Line Items]
Principal Amount Settled	1,000.0
Cash Paid	1,000.0
Total consideration, extinguishment of debt	1,000.0
Loss on settlement of debt	$ 0.3

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 50
-Section 40
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=117329964&loc=d3e12355-112629

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
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-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585

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