Capital Stock - Summary of Dividends Declared (Details) - USD ($) $ / shares in Units, $ in Millions											12 Months Ended
	Mar. 26, 2020	Feb. 13, 2020	Dec. 12, 2019	Nov. 06, 2019	Sep. 12, 2019	Jul. 24, 2019	Jun. 13, 2019	May 01, 2019	Mar. 27, 2019	Feb. 06, 2019	Dec. 31, 2020	Dec. 31, 2019
Equity [Abstract]
Dividends declared per common share (in dollars per share)		$ 0.34		$ 0.34		$ 0.34		$ 0.32		$ 0.32	$ 0.34	$ 1.32
Dividend paid (in dollars per share)	$ 0.34		$ 0.34		$ 0.34		$ 0.32		$ 0.32
Total Amount (in millions)	$ 48		$ 50		$ 50		$ 48		$ 47