Derivative Instruments and Hedging Activities - Gains and losses on derivatives (Details) $ in Millions	9 Months Ended
Sep. 30, 2021 USD ($)
Gains and losses on derivatives
Gain recorded in AOCI on derivatives, net	$ 6.5
Cash flow hedging \| Interest rate swaps
Gains and losses on derivatives
Gain recorded in AOCI on derivatives, before tax	8.5
Tax impact	(2.0)
Gain recorded in AOCI on derivatives, net	6.5
Gain (loss) on derivatives	$ (9.5)
Derivative, Gain (Loss), Statement of Income or Comprehensive Income	Interest Expense.

Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)(1)
-URI https://asc.fasb.org/extlink&oid=125515794&loc=SL5618551-113959

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Indicates line item in statement of income or comprehensive income that includes gain (loss) from derivative.

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Amount, after tax and reclassification, of gain (loss) from derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness, attributable to parent.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 11
-URI https://asc.fasb.org/extlink&oid=126968391&loc=d3e637-108580

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Amount, before tax and after reclassification, of gain (loss) from derivative instrument designated and qualifying cash flow hedge included in assessment of hedge effectiveness, attributable to parent.

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Amount, after reclassification, of tax expense (benefit) for gain (loss) from derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness, attributable to parent.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 12
-URI https://asc.fasb.org/extlink&oid=126968391&loc=d3e640-108580

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