Earnings (Loss) Per Common Share Level 4 Computation of Basic and Diluted Earnings Per Common Share (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Earnings
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	$ 428	$ 303
(Loss) income from discontinued operations, net of tax	169	75
Net Income (Loss) Attributable to Parent	$ 597	$ 378
Shares
Weighted average common shares outstanding, basic	357.5	371.4
Dilutive effect of stock compensation plans	4.4	4.2
Dilutive effect of warrants	2.0	3.0
Weighted average common shares outstanding and dilutive potential common shares	363.9	378.6
Earnings Per Share, Basic [Abstract]
Income (Loss) from Continuing Operations, Per Basic Share	$ 1.20	$ 0.82
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share	0.47	0.20
Basic	1.67	1.02
Earnings Per Share, Diluted [Abstract]
Income (Loss) from Continuing Operations, Per Diluted Share	1.18	0.80
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share	0.46	0.20
Diluted	$ 1.64	$ 1.00