Subsequent Events (Details) $ / shares in Units, shares in Millions, $ in Millions		1 Months Ended	2 Months Ended	3 Months Ended		9 Months Ended
	Oct. 05, 2021 USD ($) shares	Oct. 31, 2021 USD ($) shares	Oct. 05, 2021 $ / shares shares	Dec. 31, 2021 USD ($) retiree	Sep. 30, 2021 USD ($) shares	Sep. 30, 2021 USD ($) shares
Subsequent Event [Line Items]
Number of shares repurchased | shares					73.8	73.8
Repurchases of common stock					$ 909	$ 909
August 2021 Stock Repurchase Program
Subsequent Event [Line Items]
Number of shares repurchased | shares						3.5
Repurchases of common stock						$ 45
Subsequent Event
Subsequent Event [Line Items]
Number of shares repurchased | shares		3.5
Repurchases of common stock		$ 45
Subsequent Event | August 2021 Stock Repurchase Program
Subsequent Event [Line Items]
Number of shares repurchased | shares	3.6		80.9
Repurchases of common stock	$ 46
Average purchase price (in dollars per share) | $ / shares			$ 12.36
US | Forecast
Subsequent Event [Line Items]
Pension liability				$ 1,400
Combined Pension Plan | Forecast
Subsequent Event [Line Items]
Pension settlement charges				$ 350
Combined Pension Plan | US | Forecast
Subsequent Event [Line Items]
Number of retirees | retiree				22,600