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, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Earnings Per Share:
Net income available to common shareholders	$ 684	$ 562	$ 2,032	$ 754
Less: Income allocated to participating securities	1	2	5	3
Net income allocated to common shareholders	$ 683	$ 560	$ 2,027	$ 751
Average shares	697,457,483	715,102,136	706,845,513	714,477,089
Earnings per share (in dollars per share)	$ 0.98	$ 0.78	$ 2.87	$ 1.05
Earnings Per Diluted Share:
Net income available to common shareholders	$ 684	$ 562	$ 2,032	$ 754
Stock-based awards	0	0	0	0
Less: Income allocated to participating securities	1	2	5	3
Net income allocated to common shareholders	$ 683	$ 560	$ 2,027	$ 751
Average shares, stock based awards	9,000,000	4,000,000	9,000,000	5,000,000
Average shares	706,089,674	718,893,892	715,803,010	718,942,648
Earnings per diluted share (in dollars per share)	$ 0.97	$ 0.78	$ 2.83	$ 1.04