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		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Earnings per share:
Net income (loss) available to common shareholders	$ 563	$ 344	$ 1,252	$ 634
Less: Income allocated to participating securities	6	4	15	7
Earnings per share - basic	557	340	1,237	627
Earnings per diluted share:
Net income available to common shareholders	563	344	1,252	634
Stock-based awards	0	0
Net income available to common shareholders plus assumed conversions	563	344	1,252	634
Less: Income allocated to participating securities	6	4	14	7
Net income allocated to common shareholders	$ 557	$ 340	$ 1,238	$ 627
Earnings per share:
Net income allocated to common shareholders	683,344,844	741,400,700	686,564,682	744,516,799
Effect of dilutive securities:
Stock-based awards	13,000,000	11,000,000	13,000,000	12,000,000
Net income allocated to common shareholders	696,209,943	752,328,298	700,133,642	756,545,341
Earnings per share:
Earnings per share - basic	$ 0.81	$ 0.46	$ 1.8	$ 0.84
Earnings per diluted share:
Earnings per share - diluted	$ 0.8	$ 0.45	$ 1.77	$ 0.83