Net Earnings Per Common Share - Basic and Diluted Net Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Basic:
Net income	$ 203	$ 322
Less common and preferred dividends	66	64
Undistributed earnings	137	258
Less undistributed earnings applicable to nonvested shares	1	2
Undistributed earnings applicable to common shares	136	256
Distributed earnings applicable to common shares	57	56
Total earnings applicable to common shares	$ 193	$ 312
Weighted average common shares outstanding (in shares)	151,285	163,551
Net earnings per common share (in dollars per share)	$ 1.27	$ 1.90
Diluted:
Dilutive effect of stock options (in shares)	402	336
Weighted average diluted common shares outstanding (in shares)	151,687	163,887
Net earnings per common share (in dollars per share)	$ 1.27	$ 1.90