Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Earnings Per Share [Abstract]
Net income applicable to common shareholders	$ 152	$ 222	$ 448	$ 384
Weighted Average Shares
Weighted average common shares outstanding (in shares)	52,862,288	57,032,746	52,767,923	56,827,171
Effect of dilutive securities
Stock-based awards (in shares)	797,134	347,063	731,366	404,518
Weighted average diluted common shares (in shares)	53,659,422	57,379,809	53,499,289	57,231,689
Earnings per common share
Basic earnings per common share (in dollars per share)	$ 2.87	$ 3.90	$ 8.48	$ 6.76
Effect of dilutive securities
Stock-based awards (in dollars per share)	(0.04)	(0.02)	(0.11)	(0.05)
Diluted earnings per common share (in dollars per share)	$ 2.83	$ 3.88	$ 8.37	$ 6.71