Consolidated Statements of Shareholders' Equity (Parenthetical) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2019
Cash dividends declared
Common stock, dividend per share (in dollars per share)	$ 0.43	$ 0.43
Cumulative Effect, Period of Adoption, Adjustment
Cash dividends declared
Impact of new accounting guidance, net of tax			$ 1,170
Impact of new accounting guidance, tax			$ 288
Series B Preferred Stock
Cash dividends declared
Preferred stock, dividend per share (in dollars per share)	12.43	14.09
Series C Preferred Stock
Cash dividends declared
Preferred stock, dividend per share (in dollars per share)	$ 10.30	$ 24.50