EPS - Calculation of EPS and the Reconciliation of Earnings Per Share to Earnings Per Diluted Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Earnings per share:
Net income (loss) available to common shareholders	$ 427	$ 579	$ 1,187	$ 1,265
Less: Income allocated to participating securities	4	6	11	15
Earnings per share - basic	423	573	1,176	1,250
Earnings per diluted share:
Net income available to common shareholders	427	579	1,187	1,265
Stock-based awards	0	0	0	0
Net income available to common shareholders plus assumed conversions	427	579	1,187	1,265
Less: Income allocated to participating securities	4	6	11	15
Net income allocated to common shareholders	$ 423	$ 573	$ 1,176	$ 1,250
Earnings per share:
Net income allocated to common shareholders	738,051,421	683,344,844	699,766,962	686,564,682
Effect of dilutive securities:
Stock-based awards	10,000,000	13,000,000	9,000,000	13,000,000
Net income allocated to common shareholders	747,749,591	696,209,943	709,430,194	700,133,642
Earnings per share:
Earnings per share - basic	$ 0.57	$ 0.84	$ 1.68	$ 1.82
Earnings per diluted share:
Earnings per share - diluted	$ 0.57	$ 0.82	$ 1.66	$ 1.79