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		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Basic:
Net income	$ 240	$ 175	$ 916	$ 255
Less common and preferred dividends	68	64	197	193
Less impact from redemption of preferred stock	0	0	3	0
Undistributed earnings	172	111	716	62
Less undistributed earnings applicable to nonvested shares	1	1	6	1
Undistributed earnings applicable to common shares	171	110	710	61
Distributed earnings applicable to common shares	61	56	172	168
Total earnings applicable to common shares	$ 232	$ 166	$ 882	$ 229
Weighted average common shares outstanding (in shares)	160,221	163,608	162,159	163,764
Net earnings per common share (in dollars per share)	$ 1.45	$ 1.01	$ 5.44	$ 1.40
Diluted:
Dilutive effect of common stock warrants (in shares)	0	0	0	2,027
Dilutive effect of stock options (in shares)	259	171	301	238
Weighted average diluted common shares outstanding (in shares)	160,480	163,779	162,460	166,029
Net earnings per common share (in dollars per share)	$ 1.45	$ 1.01	$ 5.43	$ 1.38