|**Statement of Cash Flows (Tables)**                               | 12 Months Ended                                                                                                                                                                                                                                                                                                                                                                                    
|------------------------------------------------------------------ | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|
|**Supplemental Cash Flow Elements [Abstract]**                     |                                                                                                                                                                                                                                                                                                                                                                                                    
|Schedule of Supplemental Cash Flow Information                     | Supplemental cash flow information is as follows:Years ended December 31 (dollars in millions)202120202019Net change in current assets and liabilities, net of acquisitions:Receivables$(25.5)$4.5$62.4Inventories(109.5)2.96.3Other current assets4.94.7(4.8)Trade payables142.985.6(35.4)Accrued liabilities, including payroll and benefits56.329.314.2Income taxes21.73.4(10.1)$90.8$130.4$32.6
|                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                    
|Years ended December 31 (dollars in millions)                      | 2021                                                                                                                                                                                                                                                                                                                                                                                               
|Net change in current assets and liabilities, net of acquisitions: |                                                                                                                                                                                                                                                                                                                                                                                                    
|Receivables                                                        | $                                                                                                                                                                                                                                                                                                                                                                                                  
|Inventories                                                        | (109.5)                                                                                                                                                                                                                                                                                                                                                                                            
|Other current assets                                               | 4.9                                                                                                                                                                                                                                                                                                                                                                                                
|Trade payables                                                     | 142.9                                                                                                                                                                                                                                                                                                                                                                                              
|Accrued liabilities, including payroll and benefits                | 56.3                                                                                                                                                                                                                                                                                                                                                                                               
|Income taxes                                                       | 21.7                                                                                                                                                                                                                                                                                                                                                                                               
|                                                                   | $                                                                                                                                                                                                                                                                                                                                                                                                  

X- DefinitionTabular disclosure of supplemental cash flow information for the periods presented.
+ ReferencesNo definition available.
+ Details**Name:**
us-gaap_ScheduleOfCashFlowSupplementalDisclosuresTableTextBlock**Namespace Prefix:**
us-gaap_**Data Type:**
dtr-types:textBlockItemType**Balance Type:**
na**Period Type:**
duration X- ReferencesNo definition available.
+ Details**Name:**
us-gaap_SupplementalCashFlowElementsAbstract**Namespace Prefix:**
us-gaap_**Data Type:**
xbrli:stringItemType**Balance Type:**
na**Period Type:**
duration