Earnings Per Share - Calculation of Earnings Per Share and the Reconciliation of Earnings Per Share to Earnings Per Diluted Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Earnings Per Share:
Net income available to common shareholders	$ 562	$ 530	$ 754	$ 1,718
Less: Income allocated to participating securities	2	4	3	16
Net income allocated to common shareholders	$ 560	$ 526	$ 751	$ 1,702
Average shares	715,102,136	726,715,542	714,477,089	708,848,535
Earnings per share (in dollars per share)	$ 0.78	$ 0.72	$ 1.05	$ 2.40
Earnings Per Diluted Share:
Net income available to common shareholders	$ 562	$ 530	$ 754	$ 1,718
Stock-based awards	0	0	0	0
Less: Income allocated to participating securities	2	4	3	16
Net income allocated to common shareholders	$ 560	$ 526	$ 751	$ 1,702
Average shares, stock based awards	4,000,000	9,000,000	5,000,000	9,000,000
Average shares	718,893,892	736,086,399	718,942,648	718,413,237
Earnings per diluted share (in dollars per share)	$ 0.78	$ 0.71	$ 1.04	$ 2.37