EPS (Calculation of Earnings Per Share and the Reconciliation of Earnings Per Share to Earnings Per Diluted Share) (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings per share:
Net income (loss) available to common shareholders	$ 418	$ 999	$ 1,669	$ 1,633
Less: Income allocated to participating securities	5	10	18	18
Earnings per share - basic	413	989	1,651	1,615
Earnings per diluted share:
Net income available to common shareholders	418	999	1,669	1,633
Stock-based awards	0	0	0	0
Net income available to common shareholders plus assumed conversions	418	999	1,669	1,633
Less: Income allocated to participating securities	5	10	18	18
Net income allocated to common shareholders	$ 413	$ 989	$ 1,651	$ 1,615
Earnings per share:
Net income allocated to common shareholders	667,624,132	721,280,389	680,181,785	736,686,213
Effect of dilutive securities:
Stock-based awards	11,000,000	12,000,000	13,000,000	12,000,000
Net income allocated to common shareholders	679,198,715	733,284,502	693,078,647	748,706,522
Earnings per share:
Earnings per share - basic	$ 0.62	$ 1.37	$ 2.43	$ 2.19
Earnings per diluted share:
Earnings per share - diluted	$ 0.61	$ 1.35	$ 2.38	$ 2.16