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		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Basic:
Net income	$ 354	$ 66	$ 676	$ 80
Less common and preferred dividends	65	66	129	130
Less impact from redemption of preferred stock	3	0	3	0
Undistributed earnings	286	0	544	(50)
Less undistributed earnings applicable to nonvested shares	2	0	5	0
Undistributed earnings applicable to common shares	284	0	539	(50)
Distributed earnings applicable to common shares	56	56	111	112
Total earnings applicable to common shares	$ 340	$ 56	$ 650	$ 62
Weighted average common shares outstanding (in shares)	162,742	163,542	163,144	163,843
Net earnings per common share (in dollars per share)	$ 2.08	$ 0.34	$ 3.98	$ 0.38
Diluted:
Dilutive effect of common stock warrants (in shares)	0	723	0	4,012
Dilutive effect of stock options (in shares)	312	160	324	277
Weighted average diluted common shares outstanding (in shares)	163,054	164,425	163,468	168,132
Net earnings per common share (in dollars per share)	$ 2.08	$ 0.34	$ 3.98	$ 0.37