Leases - Lease Cost (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020
Lease cost
Operating lease cost	$ 11.7	$ 12.1
Finance lease cost:
Amortization of right-of-use assets	1.5	1.5
Interest on finance lease liabilities	0.1	0.2
Short-term lease cost	0.1	0.1
Sublease (income)	0.2	0.2
Variable lease cost	2.8	2.6
Total lease cost	$ 16.0	$ 16.3

Amount of interest expense on finance lease liability.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 4
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-URI http://asc.fasb.org/extlink&oid=123408670&loc=SL77918686-209980

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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Amount of amortization expense attributable to right-of-use asset from finance lease.

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- Definition

Amount of lease cost recognized by lessee for lease contract.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Amount of single lease cost, calculated by allocation of remaining cost of lease over remaining lease term. Includes, but is not limited to, single lease cost, after impairment of right-of-use asset, calculated by amortization of remaining right-of-use asset and accretion of lease liability.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
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-SubTopic 20
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-Paragraph 53
-URI http://asc.fasb.org/extlink&oid=123414884&loc=SL77918982-209971

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- Definition

Amount of short-term lease cost, excluding expense for lease with term of one month or less.

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- Definition

Amount of sublease income excluding finance and operating lease expense.

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- Definition

Amount of variable lease cost, excluded from lease liability, recognized when obligation for payment is incurred for finance and operating leases.

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