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		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Earnings
Income from continuing operations, net of tax	$ 535	$ 427	$ 1,537	$ 1,289
Less: Preferred stock dividends	11	0	16	0
Income from discontinued operations, net of tax, available to common stockholders	524	427	1,521	1,289
Income from discontinued operations, net of tax, available to common stockholders	0	5	0	322
Net income available to common stockholders	$ 524	$ 432	$ 1,521	$ 1,611
Shares
Weighted average common shares outstanding, basic	361.4	358.6	361.0	358.1
Dilutive effect of stock-based awards under compensation plans	4.0	3.6	3.4	4.0
Dilutive effect of warrants [1]	0.0	1.9	0.7	2.0
Weighted average common shares outstanding and dilutive potential common shares	365.4	364.1	365.1	364.1
Earnings Per Share, Basic [Abstract]
Income from continuing operations, net of tax, available to common stockholders	$ 1.45	$ 1.19	$ 4.21	$ 3.60
Income from discontinued operations, net of tax, available to common stockholders	0	0.01	0	0.90
Net income available to common stockholders	1.45	1.20	4.21	4.50
Earnings Per Share, Diluted [Abstract]
Income from continuing operations, net of tax, available to common stockholders	1.43	1.17	4.17	3.54
Income from discontinued operations, net of tax, available to common stockholders	0	0.02	0	0.88
Net income available to common stockholders	$ 1.43	$ 1.19	$ 4.17	$ 4.42