Parent Company Financial Statements - Consolidated Balance Sheet of Parent Company Only (Detail) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	$ 3,493	$ 1,383
Other assets	1,017	1,193
Total Assets	39,513	37,354	$ 34,615
Other liabilities	419	374
Long-term borrowings	682	1,095
Long-term	68	81
Total Liabilities	34,363	32,395
Stockholders' equity attributable to parent	5,150	4,959	$ 4,883	$ 4,608
Total Liabilities and Stockholders’ Equity	39,513	37,354
Parent Company
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	295	380
Other assets	15	10
Total Assets	6,017	5,825
Other liabilities	41	40
Advances from affiliates	197	197
Long-term borrowings	621	621
Short-term	7	7
Long-term	1	1
Total Liabilities	867	866
Stockholders' equity attributable to parent	5,150	4,959
Total Liabilities and Stockholders’ Equity	6,017	5,825
Parent Company | Bank Subsidiary
Condensed Balance Sheet Statements, Captions [Line Items]
Investment in and advances to subsidiaries	5,246	5,064
Parent Company | Non-bank Subsidiaries
Condensed Balance Sheet Statements, Captions [Line Items]
Investment in and advances to subsidiaries	$ 461	$ 371