Amounts Held for Sale (Notes)	3 Months Ended
Dec. 31, 2020
Assets and Liabilities Held for Sale [Abstract]
Amounts Held for Sale	AMOUNTS HELD FOR SALE The Company had a Post Consumer Brands RTE cereal manufacturing plant in Clinton, Massachusetts (the “Clinton Plant”) with a book value of $1.4 and $3.4 classified as held for sale at December 31, 2020 and September 30, 2020, respectively. Additionally, at September 30, 2020, the Company had land and a building with a combined book value of $1.4 classified as held for sale at its Post Consumer Brands RTE cereal manufacturing facility in Asheboro, North Carolina (the “Asheboro Facility”) and land and a building with a combined book value of $2.5 classified as held for sale at one of its Weetabix manufacturing facilities, in Corby, United Kingdom (the “Corby Facility”). The Company sold a portion of the Clinton Plant, the Asheboro Facility and the Corby Facility in November 2020. These assets held for sale were reported as “Prepaid expenses and other current assets” on the Condensed Consolidated Balance Sheets.In the three months ended December 31, 2020, a net gain on assets held for sale of $0.6 was recorded consisting of (i) a gain of $0.7 related to the sale of the Corby Facility and (ii) a loss of $0.1 related to the sale of the Asheboro Facility. This held for sale net gain was included in “Other operating (income) expenses, net” in the Condensed Consolidated Statement of Operations for the three months ended December 31 2020. There were no held for sale gains or losses recorded in the three months ended December 31, 2019.

Amounts Held for Sale (Notes)

3 Months Ended

Dec. 31, 2020

Assets and Liabilities Held for Sale [Abstract]

AMOUNTS HELD FOR SALE The Company had a Post Consumer Brands RTE cereal manufacturing plant in Clinton, Massachusetts (the “Clinton Plant”) with a book value of $1.4 and $3.4 classified as held for sale at December 31, 2020 and September 30, 2020, respectively. Additionally, at September 30, 2020, the Company had land and a building with a combined book value of $1.4 classified as held for sale at its Post Consumer Brands RTE cereal manufacturing facility in Asheboro, North Carolina (the “Asheboro Facility”) and land and a building with a combined book value of $2.5 classified as held for sale at one of its Weetabix manufacturing facilities, in Corby, United Kingdom (the “Corby Facility”). The Company sold a portion of the Clinton Plant, the Asheboro Facility and the Corby Facility in November 2020. These assets held for sale were reported as “Prepaid expenses and other current assets” on the Condensed Consolidated Balance Sheets.In the three months ended December 31, 2020, a net gain on assets held for sale of $0.6 was recorded consisting of (i) a gain of $0.7 related to the sale of the Corby Facility and (ii) a loss of $0.1 related to the sale of the Asheboro Facility. This held for sale net gain was included in “Other operating (income) expenses, net” in the Condensed Consolidated Statement of Operations for the three months ended December 31 2020. There were no held for sale gains or losses recorded in the three months ended December 31, 2019.