Earnings (Loss) Per Common Share - Computation of Basic and Diluted Earnings Per Common Share (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Earnings
Net income	$ 442	$ 905	$ 887	$ 1,154
Less: Preferred stock dividends	5	5	10	10
Net income available to common stockholders	$ 437	$ 900	$ 877	$ 1,144
Shares
Weighted average common shares outstanding, basic	327.4	353.7	329.9	356.0
Dilutive effect of stock-based awards under compensation plans	4.4	4.8	4.7	4.4
Weighted average common shares outstanding and dilutive potential common shares	331.8	358.5	334.6	360.4
Earnings Per Share, Basic [Abstract]
Net income available to common stockholders	$ 1.33	$ 2.54	$ 2.66	$ 3.21
Earnings Per Share, Diluted [Abstract]
Net income available to common stockholders	$ 1.32	$ 2.51	$ 2.62	$ 3.17