Parent Company Financial Statements (Condensed Statements of Income - Parent Company Only) (Parenthetical) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Dividend Received From Nonbank Companies And Related Subsidiaries	$ 2,000	$ 1,900
MB Financial, Inc.
Dividend Received From Nonbank Companies And Related Subsidiaries	200
Parent Company Only
Dividends from Bancorp's banking subsidiary to the Bancorp's non-bank subsidiary	2,000	1,900	$ 2,300
Dividend Received From Nonbank Companies And Related Subsidiaries	$ 2,155	$ 1,890	$ 2,343