Pension and Other Postretirement Benefit Costs - Narrative - USD ($) $ in Millions	6 Months Ended
Jun. 30, 2021	Jun. 30, 2020
Pension and Other Postretirement Benefits Cost (Reversal of Cost) [Abstract]
Employer contributions	$ 4.7	$ 4.4
Defined benefit pension plan cash contributions	$ 9.6

Amount of cash outflow for pension and other postretirement benefits. Includes, but is not limited to, employer contribution to fund plan asset and payment to retiree.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 25
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3536-108585

Name:	us-gaap_PensionAndOtherPostretirementBenefitContributions
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration