Revenue Recognition (Costs to Obtain Contracts) (Details) $ in Millions	3 Months Ended
Mar. 31, 2021 USD ($)
Change in Capitalized Contract Costs [Roll Forward]
Balance at January 1, 2021	$ 8.7
Costs to obtain contracts	0.0
Amortization of costs to obtain contracts	(0.9)
Balance at March 31, 2021	$ 7.8

Amount, after accumulated amortization and accumulated impairment loss, of asset recognized from cost incurred to obtain or fulfill contract with customer.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 340
-SubTopic 40
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=68051541&loc=SL49131252-203054

Name:	us-gaap_CapitalizedContractCostNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant