Financing Arrangements (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2018	Dec. 31, 2015
Line of Credit Facility [Line Items]
Percentage ownership	100.00%
Finance lease agreement, amount					$ 50,000,000
Finance lease obligations		$ 15,200,000	$ 18,700,000
Southwest Steel Processing LLC | Arkansas Development Finance Authority
Line of Credit Facility [Line Items]
Maximum borrowing capacity					$ 11,000,000
Borrowings outstanding		6,100,000
Machinery and Equipment
Line of Credit Facility [Line Items]
Finance lease obligations		$ 15,200,000
Senior Notes Due 2027 | Senior Notes | Park-Ohio Industries, Inc.
Line of Credit Facility [Line Items]
Aggregate principal amount	$ 350,000,000
Stated interest rate	6.625%
Revolving credit facility
Line of Credit Facility [Line Items]
Stated interest rate		1.30%
Revolving credit facility | Seventh Amendment Credit Agreement | Park-Ohio Industries, Inc.
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 350,000,000
Revolving credit facility | Amendment No. 1 to Seventh Amended and Restated Credit Agreement | Park-Ohio Industries, Inc.
Line of Credit Facility [Line Items]
Maximum borrowing capacity				$ 375,000,000
Increase in additional borrowing capacity				100,000,000
Bank guarantees and letters of credit outstanding		$ 35,300,000	$ 34,900,000
Revolving credit facility | Financing Agreement | Line of Credit | Banco Bolbao Vizcaya Argentaria, S.A.
Line of Credit Facility [Line Items]
Maximum borrowing capacity		11,600,000
Borrowings outstanding		0
Revolving Credit Facility Canadian Sub-Limit | Seventh Amendment Credit Agreement | Park-Ohio Industries, Inc.
Line of Credit Facility [Line Items]
Maximum borrowing capacity	35,000,000
Revolving Credit Facility Canadian Sub-Limit | Amendment No. 1 to Seventh Amended and Restated Credit Agreement | Park-Ohio Industries, Inc.
Line of Credit Facility [Line Items]
Maximum borrowing capacity				40,000,000
Revolving Credit Facility European Sub-Limit | Seventh Amendment Credit Agreement | Park-Ohio Industries, Inc.
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 25,000,000
Revolving Credit Facility European Sub-Limit | Amendment No. 1 to Seventh Amended and Restated Credit Agreement | Park-Ohio Industries, Inc.
Line of Credit Facility [Line Items]
Maximum borrowing capacity				$ 30,000,000
Industrial Equipment Group European Facilities | Line of Credit | Banco Bolbao Vizcaya Argentaria, S.A.
Line of Credit Facility [Line Items]
Maximum borrowing capacity		$ 28,900,000