Acquisitions and Divestitures - Purchase Price Allocation (Details) - USD ($) $ in Millions	Jul. 17, 2020	Jul. 01, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Consideration paid:
Goodwill			$ 1,511	$ 1,433	$ 1,433	$ 1,387
IBERIABANK (IBKC)
Assets:
Cash and due from banks		$ 395
Interest-bearing deposits with banks		1,683
Securities available for sale at fair value		3,544
Loans held for sale		320
Loans and leases		25,921	25,900
Allowance for loan and lease losses		(284)
Other intangible assets		240
Premises and equipment		311
OREO		9
Other assets		1,153
Total assets acquired		33,292
Liabilities:
Deposits		28,232
Short-term borrowings		209
Term borrowings		1,200
Other liabilities		616
Total liabilities assumed		30,257
Net assets acquired		3,035
Consideration paid:
Consideration for outstanding common stock		28
Total consideration paid		2,502
Goodwill		(533)
IBERIABANK (IBKC) | Sales-Type And Direct Financing Leases | Commercial
Assets:
Loans and leases			1,300
IBERIABANK (IBKC) | Common Sock
Consideration paid:
Consideration for outstanding common stock		2,243
IBERIABANK (IBKC) | Preferred Stock
Consideration paid:
Consideration for outstanding common stock		$ 231
SunTrust Banks, Inc. Branches
Assets:
Cash and due from banks	$ 2,202
Loans and leases	423
Allowance for loan and lease losses	(2)
Other intangible assets	7
Premises and equipment	11
Other assets	27
Total assets acquired	2,668
Liabilities:
Deposits	2,195
Other liabilities	30
Total liabilities assumed	2,225
Net assets acquired	443
Consideration paid:
Cash in lieu of fractional shares	521
Total consideration paid	521
Goodwill	$ 78		$ 78