Number of shares of equity interests issued or issuable to acquire entity.

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Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Number of shares issued which are neither cancelled nor held in the treasury.

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The number of shares issued during the period upon the conversion of units. An example of a convertible unit is an umbrella partnership real estate investment trust unit (UPREIT unit).

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Number of shares issued during the period to an employee benefit plan, such as a defined contribution or defined benefit plan.

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Number of new stock issued during the period.

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Number of shares related to Restricted Stock Award forfeited during the period.

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Number of share options (or share units) exercised during the current period.

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Number of common and preferred shares that were previously issued and that were repurchased by the issuing entity and held in treasury on the financial statement date. This stock has no voting rights and receives no dividends.

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Shareholders' Equity - Common Stock Outstanding (Details) - shares		1 Months Ended	12 Months Ended
	Oct. 01, 2018	Oct. 31, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Treasury stock (in shares)			14,592,888	14,592,888
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Tenneco shares issued for purchase of Federal-Mogul (in shares)		29,444,846
Common Stock \| Federal-Mogul
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Tenneco shares issued for purchase of Federal-Mogul (in shares)	29,444,846
Class A
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued, beginning balance (in shares)			71,727,061	71,675,379	66,033,509
Share issuances (in shares)			0	0	5,651,177
Issuance (repurchased) pursuant to benefit plans (in shares)			640,112	113,916	19,919
Restricted stock forfeited and withheld for taxes (in shares)			(138,225)	(70,672)	(51,049)
Exercised (in shares)			0	8,438	21,823
Class B common stock converted to Class A common stock (in shares)			3,485,215	0	0
Shares issued, ending balance (in shares)			75,714,163	71,727,061	71,675,379
Treasury stock (in shares)			14,592,888	14,592,888	14,592,888
Total shares outstanding (in shares)			61,121,275	57,134,173	57,082,491
Class A \| Common Stock \| Federal-Mogul
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Tenneco shares issued for purchase of Federal-Mogul (in shares)	5,651,177
Class B
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued, beginning balance (in shares)			23,793,669	23,793,669	0
Share issuances (in shares)			0	0	23,793,669
Issuance (repurchased) pursuant to benefit plans (in shares)			0	0	0
Restricted stock forfeited and withheld for taxes (in shares)			0	0	0
Exercised (in shares)			0	0	0
Class B common stock converted to Class A common stock (in shares)			(3,485,215)	0	0
Shares issued, ending balance (in shares)			20,308,454	23,793,669	23,793,669
Treasury stock (in shares)			0	0	0
Total shares outstanding (in shares)			20,308,454	23,793,669	23,793,669