Capital Stock - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Class of Stock [Line Items]
Common stock cash dividends paid	$ 0	$ 37
Dividends, share-based compensation		1
Common Stock
Class of Stock [Line Items]
Common stock cash dividends paid		$ 37
Common Stock | Payments for Share Repurchases Related to Employee Stock Based Compensation
Class of Stock [Line Items]
Common stock repurchased (in shares)	0