Net income (loss) per common share - Anti-dilutive securities (Details) - shares shares in Millions			3 Months Ended	9 Months Ended
Mar. 26, 2021	Mar. 22, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Net income (loss) per common share
Common stock, shares issued	10	10
Antidilutive securities excluded from computation of earnings per share (in shares)			2	1	4	1

Number of new stock issued during the period.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
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-Section S99
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
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-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration