F.N.B. (FNB) 10-K 25 Feb 21 2020 FY Annual report Financial data

Cover Page

Cover Page - USD ($)	12 Months Ended
	Dec. 31, 2020	Jan. 31, 2021	Jun. 30, 2020
Entity Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	001-31940
Entity Registrant Name	FNB CORP/PA/
Entity Incorporation, State or Country Code	PA
Entity Tax Identification Number	25-1255406
Entity Address, Address Line One	One North Shore Center,
Entity Address, Address Line Two	12 Federal Street,
Entity Address, City or Town	Pittsburgh,
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	15212
City Area Code	800
Local Phone Number	555-5455
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 2,364,996,210
Entity Common Stock, Shares Outstanding		321,523,121
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE Portions of F.N.B. Corporation’s definitive proxy statement to be filed pursuant to Regulation 14A for the Annual Meeting of Stockholders to be held on May 11, 2021 are incorporated by reference into Part III, Items 10, 11, 12, 13 and 14, of this Annual Report on Form 10-K. F.N.B. Corporation will file its definitive proxy statement with the Securities and Exchange Commission on or before April 15, 2021.
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Entity Central Index Key	0000037808
NEW YORK STOCK EXCHANGE, INC. | Common Stock, par value $0.01 per share
Entity Information [Line Items]
Title of 12(b) Security	Common Stock, par value $0.01 per share
Trading Symbol	FNB
Security Exchange Name	NYSE
NEW YORK STOCK EXCHANGE, INC. | Depositary Shares each representing 1/40th interest in a share of Fixed-to-Floating Rate Non-Cumulative Perpetual Preferred Stock, Series E
Entity Information [Line Items]
Title of 12(b) Security	Depositary Shares each representing 1/40th interest in a share of Fixed-to-Floating Rate Non-Cumulative Perpetual Preferred Stock, Series E
Trading Symbol	FNBPrE
Security Exchange Name	NYSE

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions		Dec. 31, 2020	Dec. 31, 2019
Assets
Cash and due from banks		$ 369	$ 407
Interest-bearing deposits with banks		1,014	192
Cash and Cash Equivalents		1,383	599
Debt securities available for sale (amortized cost of $3,380 and $3,275; allowance for credit losses of $0)		3,463	3,289
Debt securities held to maturity (fair value of $2,973 and $3,305; allowance for credit losses of $0)		2,868	3,275
Loans held for sale (includes $144 and $41 measured at fair value)	[1]	154	51
Loans and leases, net of unearned income of $77 and $1		25,459	23,289
Allowance for credit losses		(363)	(196)
Net Loans and Leases		25,096	23,093
Premises and equipment, net		332	333
Goodwill		2,262	2,262
Core deposit and other intangible assets, net		54	67
Bank owned life insurance		549	544
Other assets		1,193	1,102
Total Assets		37,354	34,615
Deposits:
Non-interest-bearing demand		9,042	6,384
Interest-bearing demand		13,157	11,049
Savings		3,261	2,625
Certificates and other time deposits		3,662	4,728
Total Deposits		29,122	24,786
Short-term borrowings		1,804	3,216
Long-term borrowings		1,095	1,340
Other liabilities		374	390
Total Liabilities		32,395	29,732
Stockholders’ Equity
Preferred stock - $0.01 par value; liquidation preference of $1,000 per share Authorized – 20,000,000 shares Issued – 110,877 shares		107	107
Common stock - $0.01 par value Authorized – 500,000,000 shares Issued – 328,057,368 and 327,242,364 shares		3	3
Additional paid-in capital		4,087	4,067
Retained earnings		869	798
Accumulated other comprehensive loss		(39)	(65)
Treasury stock – 6,427,839 and 2,227,804 shares at cost		(68)	(27)
Total Stockholders’ Equity		4,959	4,883
Total Liabilities and Stockholders’ Equity		$ 37,354	$ 34,615
[1]	Amount represents loans for which we have elected the fair value option. See Note 25.

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($)		Dec. 31, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Debt securities available for sale, amortized cost		$ 3,380,000,000	$ 3,275,000,000
Debt securities available for sale, allowance for credit losses		0
Debt securities held-to-maturity, fair value		2,973,000,000	3,305,000,000
Debt securities held to maturity, allowance for credit losses		40,000
Loans held for sale	[1]	144,000,000	41,000,000
Unearned income on loans		$ 77,000,000	$ 1,000,000
Preferred stock, par value (USD per Share)		$ 0.01	$ 0.01
Preferred stock, liquidation preference per share (USD per Share)		$ 1,000	$ 1,000
Preferred stock, shares authorized (in shares)		20,000,000	20,000,000
Preferred stock, shares issued (in shares)		110,877	110,877
Common stock, par value (USD per Share)		$ 0.01	$ 0.01
Common stock, shares authorized (in shares)		500,000,000	500,000,000
Common stock, shares issued (in shares)		328,057,368	327,242,364
Treasury stock, shares (in shares)		6,427,839	2,227,804
[1]	Amount represents loans for which we have elected the fair value option. See Note 25.

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Interest Income
Loans and leases, including fees	$ 990	$ 1,085	$ 1,022
Securities:
Taxable	106	126	119
Tax-exempt	32	32	28
Other	2	4	1
Total Interest Income	1,130	1,247	1,170
Interest Expense
Deposits	133	217	142
Short-term borrowings	38	80	75
Long-term borrowings	37	33	21
Total Interest Expense	208	330	238
Net Interest Income	922	917	932
Provision for credit losses	123	44	61
Net Interest Income After Provision for Credit Losses	799	873	871
Non-Interest Income
Service charges	108	124	126
Trust services	31	28	26
Insurance commissions and fees	24	20	18
Securities commissions and fees	17	17	18
Capital markets income	39	33	21
Mortgage banking operations	50	32	22
Dividends on non-marketable equity securities	14	19	16
Bank owned life insurance	14	12	13
Loss on debt extinguishment	(17)	0	0
Other	14	9	16
Total Non-Interest Income	294	294	276
Non-Interest Expense
Salaries and employee benefits	406	375	370
Net occupancy	71	59	60
Equipment	66	62	55
Amortization of intangibles	13	14	16
Outside services	69	64	66
FDIC insurance	20	23	33
Bank shares and franchise taxes	14	12	12
Other	91	87	83
Total Non-Interest Expense	750	696	695
Income Before Income Taxes	343	471	452
Income taxes	57	84	79
Net Income	286	387	373
Preferred stock dividends	8	8	8
Net Income Available to Common Stockholders	$ 278	$ 379	$ 365
Earnings per Common Share
Basic (in usd per share)	$ 0.86	$ 1.17	$ 1.13
Diluted (in usd per share)	$ 0.85	$ 1.16	$ 1.12

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 286	$ 387	$ 373
Securities available for sale:
Unrealized gains (losses) arising during the period, net of tax expense (benefit) of $15, $16 and $(5)	54	57	(17)
Derivative instruments:
Unrealized losses arising during the period, net of tax benefit of $(11), $(5) and $(1)	(40)	(17)	(2)
Reclassification adjustment for gains (losses) included in net income, net of tax expense (benefit) of $3, $0 and $0	18	(2)	(2)
Pension and postretirement benefit obligations:
Unrealized gains (losses) arising during the period, net of tax expense (benefit) of $2, $(1) and $1	(6)	3	(2)
Other Comprehensive Income (Loss)	26	41	(23)
Comprehensive Income	$ 312	$ 428	$ 350

Consolidated Statements of Co_2

Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Unrealized gains (losses) arising during the period, tax expense (benefit)	$ 15	$ 16	$ (5)
Unrealized losses arising during the period, tax benefit	(11)	(5)	(1)
Reclassification adjustment for gains (losses) included in net income, tax of expense (benefit)	3	0	0
Unrealized gains (losses) arising during the period, net of tax expense (benefit)	$ 2	$ (1)	$ 1

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Millions	Total	Adoption of New Accounting Standard	Preferred Stock	Common Stock	Additional Paid-In Capital	Retained Earnings	Retained EarningsAdoption of New Accounting Standard	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Balance at beginning of period at Dec. 31, 2017	$ 4,409		$ 107	$ 3	$ 4,033	$ 368		$ (83)	$ (19)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income (loss)	350					373		(23)
Dividends declared:
Preferred stock	(8)					(8)
Common stock	(157)					(157)
Issuance of common stock	4				6				(2)
Restricted stock compensation	10				10
Balance at end of period at Dec. 31, 2018	4,608		107	3	4,049	576		(106)	(21)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income (loss)	428					387		41
Dividends declared:
Preferred stock	(8)					(8)
Common stock	(157)					(157)
Issuance of common stock	0				6				(6)
Restricted stock compensation	12				12
Balance at end of period at Dec. 31, 2019	4,883	$ (50)	107	3	4,067	798	$ (50)	(65)	(27)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income (loss)	312					286		26
Dividends declared:
Preferred stock	(8)					(8)
Common stock	(157)					(157)
Issuance of common stock	1				4				(3)
Repurchase of common stock	(38)								(38)
Restricted stock compensation	16				16
Balance at end of period at Dec. 31, 2020	$ 4,959		$ 107	$ 3	$ 4,087	$ 869		$ (39)	$ (68)

Consolidated Statements of St_2

Consolidated Statements of Stockholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Stockholders' Equity [Abstract]
Preferred stock dividends per share (in usd per share)	$ 72.52	$ 72.52	$ 72.52
Common stock dividends per share (in usd per share)	$ 0.48	$ 0.48	$ 0.48

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating Activities
Net income	$ 286	$ 387	$ 373
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion	(3)	45	109
Provision for credit losses	123	44	61
Deferred tax expense (benefit)	(18)	33	33
Loans originated for sale	(1,886)	(1,481)	(1,117)
Loans sold	1,830	1,495	1,210
Net gain on sale of loans	(47)	(25)	(22)
Net change in:
Interest receivable	19	(8)	(6)
Interest payable	(8)	1	7
Bank owned life insurance, excluding purchases	(6)	(7)	(10)
Other, net	(177)	(225)	(27)
Net cash flows provided by operating activities	113	259	611
Investing Activities
Net change in loans and leases, excluding sales and transfers	(2,604)	(1,427)	(1,394)
Debt securities available for sale:
Purchases	(2,360)	(655)	(1,200)
Maturities/payments	2,244	770	592
Debt securities held to maturity:
Purchases	(301)	(494)	(387)
Maturities/payments	703	468	370
Increase in premises and equipment	(41)	(46)	(35)
Net cash received in business combinations and divestitures	0	0	134
Loans sold, not originated for sale	537	262	0
Other, net	0	(9)	0
Net cash flows used in investing activities	(1,822)	(1,131)	(1,920)
Financing Activities
Demand (non-interest-bearing and interest-bearing) and savings accounts	5,402	1,873	406
Time deposits	(1,065)	(539)	653
Short-term borrowings	(1,412)	(913)	450
Proceeds from issuance of long-term borrowings	328	954	37
Repayment of long-term borrowings	(574)	(239)	(77)
Repurchases of common stock	(38)	0	0
Cash dividends paid:
Preferred stock	(8)	(8)	(8)
Common stock	(157)	(157)	(157)
Other, net	17	12	14
Net cash flows provided by financing activities	2,493	983	1,318
Net Increase in Cash and Cash Equivalents	784	111	9
Cash and cash equivalents at beginning of year	599	488	479
Cash and Cash Equivalents at End of Year	$ 1,383	$ 599	$ 488

Nature of Operations

Nature of Operations	12 Months Ended
	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Operations	NATURE OF OPERATIONS F.N.B. Corporation, headquartered in Pittsburgh, Pennsylvania, is a diversified financial services company operating in seven states and the District of Columbia. Our market coverage spans several major metropolitan areas including: Pittsburgh, Pennsylvania; Baltimore, Maryland; Cleveland, Ohio; Washington, D.C.; and Charlotte, Raleigh, Durham and the Piedmont Triad (Winston-Salem, Greensboro and High Point) in North Carolina. As of December 31, 2020, we had 358 banking offices throughout Pennsylvania, Ohio, Maryland, West Virginia, North Carolina, South Carolina and Virginia. We provide a full range of commercial banking, consumer banking, and wealth management solutions through our subsidiary network which is led by our largest affiliate, FNBPA, founded in 1864. Commercial banking solutions include corporate banking, small business banking, investment real estate financing, government banking, business credit, capital markets and lease financing. Consumer banking provides a full line of consumer banking products and services including deposit products, mortgage lending, consumer lending and a complete suite of mobile and online banking services. Wealth management services include asset management, private banking and insurance.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation Our accompanying Consolidated Financial Statements and these Notes to Consolidated Financial Statements include subsidiaries in which we have a controlling financial interest. We own and operate FNBPA, FNTC, First National Investment Services Company, LLC, FNBIA, FNIA, Bank Capital Services, LLC, and F.N.B. Capital Corporation, LLC, and include results for each of these entities in the accompanying Consolidated Financial Statements. Companies in which we hold a controlling financial interest, or are a VIE in which we have the power to direct the activities of an entity that most significantly impact the entity’s economic performance and have an obligation to absorb losses or the right to receive benefits which could potentially be significant to the VIE, are consolidated. For a voting interest entity, a controlling financial interest is generally where we hold more than 50% of the outstanding voting shares. VIEs in which we do not hold the power to direct the activities of the entity that most significantly impact the entity’s economic performance or an obligation to absorb losses or the right to receive benefits which could potentially be significant to the VIE are not consolidated. Investments in companies that are not consolidated are accounted for using the equity method when we have the ability to exert significant influence. Investments in private investment partnerships that are accounted for under the equity method or the cost method are included in other assets and our proportional interest in the equity investments’ earnings are included in other non-interest income. Investment interests accounted for under the cost and equity methods are periodically evaluated for impairment. The accompanying Consolidated Financial Statements include all adjustments that are necessary, in the opinion of management, to fairly reflect our financial position and results of operations in accordance with GAAP. All significant intercompany balances and transactions have been eliminated. Certain prior period amounts have been reclassified to conform to the current period presentation. Such reclassifications had no impact on our net income and stockholders’ equity. Events occurring subsequent to December 31, 2020 have been evaluated for potential recognition or disclosure in the Consolidated Financial Statements through the date of the filing of the Consolidated Financial Statements with the SEC. Use of Estimates Our accounting and reporting policies conform with GAAP. The preparation of financial statements in conformity with GAAP requires us to make estimates and assumptions that affect the amounts reported in the Consolidated Financial Statements and accompanying Notes to Consolidated Financial Statements. Actual results could materially differ from those estimates. Material estimates that are particularly susceptible to significant changes include the ACL, accounting for loans acquired in a business combination prior to January 1, 2020, fair value of financial instruments, goodwill and other intangible assets, income taxes and DTAs. Adoption of New Accounting Standards Current Expected Credit Losses. On January 1, 2020, we adopted ASU 2016-13, Financial Instruments-Credit Losses (Topic 326), which replaces the incurred credit loss impairment methodology with a methodology that reflects lifetime current expected credit losses (commonly referred to as CECL) for most financial assets measured at amortized cost, including loans, HTM debt securities, net investment in leases and certain off-balance sheet credit exposure. We adopted CECL using the modified retrospective method for financial assets measured at amortized cost, net investments in leases and off-balance sheet credit exposures. As a result, we recorded a reduction of $50.6 million in retained earnings as of January 1, 2020 for the cumulative effect of the adoption. The transition adjustment was primarily driven by longer duration commercial and consumer real estate loans. Results for reporting periods prior to January 1, 2020 continue to be reported in accordance with previously applicable GAAP. We used the prospective transition method for PCD financial assets that were previously classified as PCI and accounted for under ASC 310-30, including loans accounted for by analogy under ASC 310-30. In accordance with the transition guidance, we did not reassess whether PCI assets met the criteria for PCD assets nor did we reassess whether modifications to individual acquired financial assets previously accounted for in pools were TDRs as of the date of adoption. We discontinued the use of pools beyond transition accounting and account for these loans on an individual loan basis. After transition, loans previously accounted for in pools are grouped with other loans with similar risk characteristics for purposes of estimating expected credit losses. As a result, beginning in 2020 certain credit metrics and ratios which previously excluded PCI loans now include PCD loans. On January 1, 2020, the amortized cost basis of the PCD assets was adjusted to reflect the addition of an ACL for $50.3 million. The net noncredit discount, after the adjustment for the ACL, is accreted into interest income at the loan’s effective interest rate over the remaining contractual life. We made an accounting policy election to write-off accrued interest receivable balances by reversing interest income in accordance with our non-accrual policies instead of measuring an ACL for accrued interest receivable for all classes of financing receivables and major security types. We do not hold any securities at adoption for which OTTI had been recognized prior to January 1, 2020. The following table illustrates the impact of the adoption of ASC 326: TABLE 1.1 January 1, 2020 (in millions) As Reported Under ASC 326 Pre-ASC 326 Adoption Impact of ASC 326 Adoption Assets: Allowance for credit losses on debt securities held-to-maturity States of the U.S. and political subdivisions (municipals) $ — $ — $ — Loans Commercial real estate $ 138 $ 60 $ 78 Commercial and industrial 65 53 12 Commercial leases 11 11 — Commercial other — 9 (9) Direct installment 24 13 11 Residential mortgages 32 22 10 Indirect installment 21 19 2 Consumer lines of credit 10 9 1 Allowance for credit losses on loans $ 301 $ 196 $ 105 Liabilities: Allowance for credit losses on off-balance sheet credit exposures $ 13 $ 3 $ 10 Reference Rate Reform. In March 2020, the FASB issued ASU 2020-04, Reference Rate Reform: Facilitation of the Effects of Reference Rate Reform on Financial Reporting (Topic 848), as amended, which provides optional guidance for a limited period of time to ease the potential burden in accounting for changes in financial reporting brought about by RRR for affected contractual modifications of floating rate financial instruments indexed to interbank offering rates and hedge accounting relationships. The expedients, exceptions and elections provided by RRR are permitted to be adopted any time through December 31, 2022 and do not apply to contract modifications made and hedging relationships entered into or evaluated after December 31, 2022, except for certain optional expedients elected for certain hedging relationships existing as of December 31, 2022. In general, RRR provides, when certain criteria are met, optional expedients and exceptions regarding the accounting for contract modifications, hedging relationships and other transactions affected by RRR. It also allows for a one-time transfer or sale of qualifying HTM securities. We adopted RRR on October 1, 2020, and the guidance will be followed until the Update terminates on December 31, 2022. The adoption did not have a material impact on our consolidated financial position or results of operations. We have not yet elected certain optional expedients, exceptions and elections related to RRR, however, we plan to elect these provisions in the future. While RRR is not expected to have a material accounting impact on our consolidated financial position or results of operations, it will ease the administrative burden in accounting for future effects of RRR. Revenue from Contracts with Customers We earn certain revenues from contracts with customers. These revenues are recognized when control of the promised services is transferred to the customers in an amount that reflects the consideration we expect to be entitled to in an exchange for those services. In determining the appropriate revenue recognition for our contracts with customers, we consider whether the contract has commercial substance and is approved by both parties with identifiable contractual rights, payment terms, and the collectability of consideration is probable. Generally, we satisfy our performance obligations upon the completion of services at the amount to which we have the right to invoice or charge under contracts with an original expected duration of one year or less. We apply this guidance on a portfolio basis to contracts with similar characteristics and for which we believe the results would not differ materially from applying this guidance to individual contracts. Our services provided under contracts with customers are transferred at the point in time when the services are rendered. Generally, we do not defer incremental direct costs to obtain contracts with customers that would be amortized in one year or less under the practical expedient. These costs are recognized as expense, primarily salary and benefit expense, in the period incurred. Deposit Services . We recognize revenue on deposit services based on published fees for services provided. Demand and savings deposit customers have the right to cancel their depository arrangements and withdraw their deposited funds at any time without prior notice. When services involve deposited funds that can be retrieved by customers without penalties, we consider the service contract term to be day-to-day, where each day represents the renewal of the contract. The contract does not extend beyond the services performed and revenue is recognized at the end of the contract term (daily) as the performance obligation is satisfied. No deposit services fees exist for long-term deposit products beyond early withdrawal penalties, which are earned on these products at the time of early termination. Revenue from deposit services fees are reduced where we have a history of waived or reduced fees by customer request or due to a customer service issue, by historical experience, or another acceptable method in the same period as the related revenues. Revenues from deposit services are reported in the Consolidated Statements of Income as service charges and in the Community Banking segment as non-interest income. Wealth Management Services. Wealth advisory and trust services are provided on a month-to-month basis and invoiced as services are rendered. Fees are based on a fixed amount or a scale based on the level of services provided or assets under management. The customer has the right to terminate their services agreement at any time. We determine the value of services performed based on the fee schedule in effect at the time the services are performed. Revenues from wealth advisory and trust services are reported in the Consolidated Statements of Income as trust services and securities commissions and fees, and in the Wealth segment as non-interest income. Insurance Services. Insurance services include full-service insurance brokerage services offering numerous lines of commercial and personal insurance through major carriers to businesses and individuals within our geographic markets. We recognize revenue on insurance contracts in effect based on contractually specified commission payments on premiums that are paid by the customer to the insurance carrier. Contracts are cancellable at any time and we have no performance obligation to the customers beyond the time the insurance is placed into effect. Revenues from insurance services are reported in the Consolidated Statements of Income as insurance commissions and fees, and in the Insurance segment as non-interest income. Business Combinations Business combinations are accounted for by applying the acquisition method . Under the acquisition method, identifiable assets acquired and liabilities assumed, and any non-controlling interest in the acquiree at the acquisition date are measured at their fair values as of that date, and are recognized separately from goodwill. Results of operations of the acquired entities are included in the Consolidated Statements of Income from the date of acquisition. Cash and Cash Equivalents Cash and cash equivalents include cash on hand, cash items in transit and amounts due from the FRB and other depository institutions (including interest-bearing deposits). Debt Securities Debt securities can be classified as trading securities can be classified as trading, HTM or AFS. As of December 31, 2020 and 2019, we did not hold any trading debt securities. Interest income on debt securities includes amortization of purchase premiums or accretion of discounts. Premiums and discounts on debt securities are generally amortized on the level-yield method without anticipating prepayments, except for mortgage-backed securities where prepayments are anticipated. Premiums on callable debt securities are amortized to their earliest call date. A debt security is placed on non-accrual when principal or interest becomes greater than 90 days delinquent. Interest accrued but not received for a security placed on non-accrual is reversed against interest income. Gains and losses on the sale of securities are recorded on the trade date and are determined using the specific identification method. HTM debt securities are securities that management has the positive intent and ability to hold until their maturity. Such securities are carried at amortized cost. Beginning in 2020, for certain HTM securities we have an expectation of zero expected credit losses. Based on a long history with no credit losses, high credit ratings, guarantees, and/or implied risk-free characteristics, we expect the nonpayment of our UST, Fannie Mae, Freddie Mac, FHLB, Ginnie Mae, and the SBA securities to be zero, and accordingly, have no ACL on those securities. We believe that these qualitative factors are indicators that historical credit loss information should be nominally impacted, if at all, by current conditions and R&S forecasts. As such, we believe that without a change in these indicators, we may continue to assume zero credit losses on securities concluded to exhibit those factors. We also have a portfolio of HTM debt securities where we do not expect credit losses to be zero. This portfolio consists of high-grade municipal securities. To calculate the expected credit losses on these securities we group securities by major security type, rating and maturity and apply respective cumulative default rates from a third party data provider. The baseline credit loss estimate is adjusted using a qualitative approach to account for potential variability in probabilities of default data for current conditions and R&S forecasts. Where available, expected credit losses take into consideration any enhancement a security has such as insurance, a guarantee or state aid. Debt securities that are not classified as trading or HTM are classified as AFS and are carried at fair value. AFS debt securities in unrealized loss positions are evaluated for impairment related to credit losses at least quarterly. Impairment may result from credit deterioration of the issuer or collateral underlying the security. In performing an assessment of whether any decline in fair value is due to a credit loss, all relevant information is considered at the individual security level. Beginning in 2020, for AFS debt securities in an unrealized loss position, we first determine whether we have the intent to sell, or it is more likely than not that we will be required to sell, the security before recovery of its amortized cost basis. If the criteria for intent or requirement to sell is met, the security’s amortized cost is written down to fair value and the write down is charged against the ACL with any incremental impairment reported in earnings in the Provision for Credit Losses line on the Consolidated Statements of Income. For AFS debt securities that do not meet the criteria for intent or requirement to sell, we evaluate whether the decline in fair value has resulted from credit losses or other factors. We first qualitatively evaluate each security to assess whether a potential credit loss exists. If as a result of this qualitative analysis we expect to get all of our principal back, then we conclude that the present value of expected cash flows equals or exceeds its amortized cost and no credit loss exists. If it was determined a potential credit loss exists, we compare the present value of cash flows expected to be collected with our amortized cost basis to measure its value. The credit loss is recorded through the ACL and limited to the amount the fair value is less than the amortized cost basis. We have made an accounting policy election for each major security type of AFS debt securities to adjust the effective interest rate used to discount expected cash flows to consider the timing of expected cash flows resulting from expected prepayments. Impairment for noncredit-related factors is recorded in OCI, net of income taxes. Changes in the ACL are recorded as a provision for credit loss expense. Losses are charged against the ACL when an AFS debt security is not collectible or when we believe the criteria regarding the intent or requirement to sell is met. Prior to 2020, we evaluated our debt securities in a loss position for OTTI on a quarterly basis at the individual security level based on our intent to sell. If we intended to sell the debt security of if it was more likely than not we would have been required to sell the security before recovery of its amortized cost basis, OTTI was recognized in earnings equal to the entire difference between the investments' amortized cost basis and its fair value. If we did not intend to sell the debt security and if it was not more likely than not that we would be required to sell the security before recovery of its amortized cost basis, the OTTI was separated into the amount representing credit loss and the amount related to all other market factors. The amount of credit loss would have been recognized in earnings and the amount related to other market factors would be recognized in OCI, net of tax. We did not recognize any OTTI during 2019 and 2018. Securities Sold Under Agreements to Repurchase Securities sold under agreements to repurchase are accounted for as collateralized financing transactions and are recorded at the amounts at which the securities were sold plus accrued interest. Securities, generally U.S. government and federal agency securities, pledged as collateral under these financing arrangements cannot be sold or repledged by the secured party. The fair value of collateral either received from or provided to a third party is continually monitored and additional collateral is obtained or is requested to be returned to us as deemed appropriate. Derivative Instruments and Hedging Activities From time to time, we may enter into derivative transactions principally to protect against the risk of adverse price or interest rate movements on the value of certain assets and liabilities and on future cash flows. Foreign exchange derivatives are entered into to accommodate the needs of customers. All derivative instruments are carried at fair value on the Consolidated Balance Sheets as either an asset or liability. Accounting for the changes in fair value of a derivative is dependent upon whether it has been designated in a formal, qualifying hedging relationship. For derivatives in qualifying hedging relationships, we formally document all relationships between hedging instruments and hedged items, as well as our risk management objective and strategy for undertaking each hedge transaction. Cash flows from hedging activities are classified in the same category as the items hedged. Beginning in the first quarter of 2019, we adopted ASU 2017-12 which provides targeted improvements to the hedge accounting model that more closely aligns the accounting and reporting for hedging relationships with risk management activities. In addition, ASU 2017-12 provides administrative relief by easing documentation requirements, simplifying the application of hedge accounting by expanding the application of the shortcut method, eliminating the separate measurement and reporting of hedge ineffectiveness and generally requiring the entire effect of the hedging instrument and the hedged item to be presented in the same income statement line item. We believe these changes will provide users with more useful information about the effect of our risk management activities on the financial statements. Changes in fair value of a derivative instrument that has been designated and qualifies as a cash flow hedge, including any ineffectiveness, are recorded in AOCI, net of tax. Amounts are reclassified from AOCI to the consolidated statements of income in the same line item used to present the earnings effect of the hedged item in the period or periods in which the hedged transaction affects earnings. Prior to 2019, the ineffective portion, if any, was reported in earnings immediately. At the hedge’s inception, a formal assessment is performed to determine whether changes in the fair values or cash flows of the derivative instruments have been highly effective in offsetting changes in fair values or cash flows of the hedged items and whether they are expected to be highly effective in the future. At each reporting period thereafter, a statistical regression or qualitative analysis is performed to evaluate hedge effectiveness. If it is determined a derivative instrument has not been or will not continue to be highly effective as a hedge, hedge accounting is discontinued. We also enter into interest rate swap agreements to meet the interest rate risk management needs of qualifying commercial loan customers. These agreements provide the customer the ability to convert from variable to fixed interest rates. We then enter into positions with a derivative counterparty in order to offset our exposure on the fixed components of the customer agreements. The credit risk associated with derivatives executed with customers is essentially the same as that involved in extending loans and is subject to normal credit policies and monitoring. We seek to minimize counterparty credit risk by entering into transactions with only high-quality institutions and using collateral agreements and other contract provisions. These arrangements meet the definition of derivatives, but are not designated as qualifying hedging relationships. The interest rate swap agreement with the loan customer and with the counterparty are reported at fair value in other assets and other liabilities on the Consolidated Balance Sheets with any resulting gain or loss recorded in current period earnings as other income. Loans Held for Sale and Loan Commitments Certain of our residential mortgage loans are originated or purchased for sale in the secondary mortgage loan market. We make an automatic election to account for all originated or purchased residential mortgage loans held for sale under the FVO. The FVO election is intended to better reflect the underlying economics and better facilitate the economic hedging of the loans. The FVO is applied on an instrument by instrument basis and is an irrevocable election. Additionally, with the election of the FVO, fees and costs associated with the origination and acquisition of residential mortgage loans held for sale are expensed as incurred, rather than deferred. Changes in fair value under the FVO are recorded in mortgage banking operations non-interest income on the consolidated statements of income. Fair value is determined on the basis of rates obtained in the respective secondary market for the type of loan held for sale. Gain or loss on the sale of loans is recorded in mortgage banking operations non-interest income. Interest income on loans held for sale is recorded in interest income. We routinely IRLCs for residential mortgage loans that we intend to sell. These IRLCs are considered derivatives. We also enter into loan sale commitments to sell these loans when funded to mitigate the risk that the market value of residential mortgage loans may decline between the time the rate commitment is issued to the customer and the time we sell the loan. These loan sale commitments are also derivatives. Both types of derivatives are recorded at fair value on the Consolidated Balance Sheets with changes in fair value recorded in mortgage banking operations non-interest income. We also originate loans guaranteed by the SBA for the purchase of businesses, business startups, business expansion, equipment, and working capital. All SBA loans are underwritten and documented as prescribed by the SBA. SBA loans originated with the intention to sell on the secondary market are classified as held for sale and carried at the lower of cost or fair value. At the time of the sale, we allocate the carrying value of the entire loan between the guaranteed portion sold and the unguaranteed portion retained based on their relative fair value which results in a discount recorded on the retained portion of the loan. The guaranteed portion is typically sold at a premium and the gain is recognized in other income for any net premium received in excess of the relative fair value of the portion of the loan transferred. The net carrying value of the retained portion of the loans is included in the appropriate commercial loan classification for disclosure purposes. Loans Loans we intend to hold for the foreseeable future or until maturity or payoff are reported at amortized cost, net of the ACL. Amortized cost primarily consists of the principal balances outstanding, deferred origination fees or costs and premiums or discounts on purchased loans. Interest income on loans is computed over the term of the loans using the effective interest method. Loan origination fees or costs, premiums or discounts are deferred and amortized over the term of the loan or loan commitment period as an adjustment to the related loan yield. Non-performing Loans We place loans on non-accrual status and discontinue interest accruals on loans generally when principal or interest is due and has remained unpaid for a certain number of days, unless the loan is both well secured and in the process of collection. Commercial loans and leases are placed on non-accrual at 90 days, installment loans are placed on non-accrual at 120 days and residential mortgages and consumer lines of credit are generally placed on non-accrual at 180 days, though we may place a loan on non-accrual prior to these past due thresholds as warranted. When a loan is placed on non-accrual status, all unpaid accrued interest is reversed against interest income and the amortization of deferred fees and costs is suspended. Non-accrual loans may not be restored to accrual status until all delinquent principal and interest have been paid and the ultimate ability to collect the remaining principal and interest is reasonably assured. Loans are charged-off against the ACL and recoveries of amounts previously charged-off are credited to the ACL when realized. Prior to 2020, PCI loans were not classified as non-performing assets as the loans were considered to be performing. Beginning in 2020, PCI loans previously accounted for in pools are grouped with other loans with similar risk characteristics for purposes of estimating expected credit losses and non-performing classification. Troubled Debt Restructured Loans Debt restructurings or loan modifications for a borrower occur in the normal course of business and do not necessarily constitute TDRs. In general, the modification or restructuring of a debt constitutes a TDR, including reasonably expected TDR, if, for economic or legal reasons related to the borrower’s financial difficulties, we grant a concession to the borrower that we would not otherwise consider under current market conditions or once we have determined that a loan modification for a financially troubled borrower is the most appropriate strategy. Additionally, a loan designated as a TDR does not necessarily result in the automatic placement of the loan on non-accrual status. When the full collection of principal and interest is reasonably assured on a loan designated as a TDR and where the borrower would not otherwise meet the criteria for non-accrual status, we will continue to accrue interest on the loan. Prior to 2020, we did not consider a restructured acquired loan as a TDR if the loan was accounted for as a component of a pool. TDR classification does not include short-term assistance to borrowers who are current at the time of a natural disaster or other extreme event (e.g. floods, hurricanes and pandemics). These borrowers are considered to not be experiencing financial difficulty at the time of modification, therefore not meeting the criteria for determining TDR status. For modifications of leases related to the effects of the COVID-19 pandemic that do not result in a substantial increase in our rights as lessor or the obligations of the lessee, we elect to account for these lease concessions as though enforceable rights and obligations for those concessions existed in the original contracts. We account for these concessions as if no changes were made to the lease contract. Allowance for Credit Losses on Loans and Leases Beginning January 1, 2020, we estimate the ACL on loans and leases using relevant available information, from internal and external sources, relating to past events, current conditions, and R&S forecasts under the CECL methodology. The ACL is measured on a collective (pool) basis when similar risk characteristics exist. Our portfolio segmentation is characterized by similarities in initial measurement, risk attributes, and the manner in which we monitor and assess credit risk and is comprised of commercial real estate, commercial and industrial, commercial leases, commercial - other, direct installment, residential mortgages, indirect installment and consumer lines of credit. The ACL on loans and leases represents our current estimate of lifetime credit losses in our loan portfolio at the balance sheet date. In determining the ACL, we estimate expected future losses for the loan's entire contractual term adjusted for expected prepayments when appropriate. The contractual term excludes expected extensions, renewals, and modifications. The ACL is the sum of three components: quantitative (formulaic or pooled) reserves; asset specific / individual loan reserves; and qualitative (judgmental) reserves. Quantitative Component We use a non-discounted cash flow factor-based approach to estimate expected credit losses that include component PD/LGD/EAD models as well as less complex estimation methods for smaller loan portfolios. • PD: This component model is used to estimate the likelihood that a borrower will cease making payments as agreed. The major contributors to this are the borrower credit attributes and macro-economic trends. • LGD: This component model is used to estimate the loss on a loan once a loan is in default. • EAD: Estimates the loan balance at the time the borrower stops making payments. For all term loans, an amortization based formulaic approach is used for account level EAD estimates. We calculate EAD using a portfolio specific method in each of our revolving product portfolios. Asset Specific / Individual Component Loans that do not share risk characteristics are generally evaluated on an individual basis. Loans evaluated individually are not included in the collective evaluation. We have elected to apply the practical expedient to measure expected credit losses of a collateral dependent asset using the fair value of the collateral, less any costs to sell. Individual reserves are determined as follows: • For commercial loans in default which are greater than or equal to $1.0 million, individual reserves are determined based on an analysis of the present value of the loan's expected future cash flows, the loan's observable market value, or the fair value of the collateral less costs to sell. • For commercial and consumer loans in default wh

New Accounting Standards

New Accounting Standards	12 Months Ended
	Dec. 31, 2020
Accounting Changes and Error Corrections [Abstract]
New Accounting Standards	NEW ACCOUNTING STANDARDS The following table summarizes accounting pronouncements issued by the FASB that we recently adopted. TABLE 2.1 Standard Description Financial Statements Impact Credit Losses ASU 2016-13 , Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments ASU 2018-19, Codification Improvements to Topic 326, Financial Instruments - Credit Losses ASU 2019-04, Codification Improvements to Topic 326, Financial Instruments-Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments ASU 2019-05, Financial Instruments-Credit Losses, (Topic 326): Targeted Transition Relief ASU 2019-11, Codification Improvements to Topic 326, Financial Instruments - Credit Losses These Updates replace the current long-standing incurred loss impairment methodology with a methodology that reflects current expected credit losses (commonly referred to as CECL) for most financial assets measured at amortized cost and certain other instruments, including loans, HTM debt securities, net investments in leases and off-balance sheet credit exposures except for unconditionally cancellable commitments. CECL requires loss estimates for the remaining life of the financial asset at the time the asset is originated or acquired, considering historical experience, current conditions and R&S forecasts. In addition, the Update will require the use of a modified AFS debt security impairment model and eliminate the current accounting for PCI loans and debt securities. On January 1, 2020, we adopted CECL using the modified retrospective method for financial assets measured at amortized cost, net investments in leases and off-balance sheet credit exposures. While these Updates change the measurement of the ACL, it does not change the credit risk of our lending portfolios or the ultimate losses in those portfolios. However, the CECL ACL methodology will produce higher volatility in the quarterly provision for credit losses than our prior reserve process. We created a cross-functional management steering group to govern implementation and the Audit and Risk Committees and the Board of Directors received regular updates. For financial assets measured at amortized cost we have implemented a new modeling platform and integrated other auxiliary models to support a calculation of expected credit losses under CECL. We have made decisions on segmentation, a R&S forecast period, a reversion method and period and a historical loss forecast covering the remaining contractual life, adjusted for prepayments as well as other criteria. Based on our portfolio composition and forecasts of relatively stable macroeconomic conditions over the next two years at the adoption date, we recorded an overall ACL of $301 million. This reflected an increase on the originated portfolio of $55 million, primarily driven by our longer duration commercial and consumer real estate loans and a "gross-up" for PCI loans of $50 million. There is no capital impact related to the PCI loans at adoption. The impact for the adoption of CECL was a reduction to retained earnings of $51 million, which included a $10 million increase to the AULC. The impact upon adoption was dependent on the portfolio composition and credit quality, as well as historical experience, current conditions and forecasts of economic conditions and interest rates at the time of adoption. The impact to our AFS and HTM debt securities was immaterial. Model development, as well as the development of policies and procedures and, internal controls were complete at the time of adoption. Standard Description Financial Statements Impact Reference Rate Reform ASU 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting ASU 2021-01, Reference Rate Reform (Topic 848): Scope These Updates provide temporary optional expedients and exceptions for applying GAAP to financial contracts, hedging relationships and other transactions affected by RRR if certain criteria are met. The following optional expedients, exceptions and elections are permitted for certain contracts that are modified because of RRR and meet certain scope guidance: • Contract modifications may be accounted for prospectively as a continuation of existing contracts rather than a new contract without remeasurement or reassessment of significant contract amendments • modifications of leases to be accounted for as a continuation of the existing contracts without reassessment of lease classification and discount rate or remeasurement of lease payments • to not reassess the original conclusion about whether a contract contains an embedded derivative that is clearly and closely related to the host contract • changes to critical terms of hedging relationships, on a hedge-by-hedge basis, without designation of the hedging relationship and various practical expedients and elections designed to allow hedge accounting to continue uninterrupted • modifications of certain derivatives modified to change the rate used for margining, discounting or contract price alignment. The Updates also allow an entity to make a one-time election to sell and/or transfer to HTM securities that are affected by RRR and were classified as HTM before January 1, 2020. RRR Updates are effective for all entities from the beginning of an interim period that includes or is subsequent to March 12, 2020 and terminates on December 31, 2022 on a full retrospective or prospective basis. Although we do not expect RRR to have a material accounting impact on our consolidated financial position or results of operations, the Updates will ease the administrative burden in accounting for the effects of RRR. We adopted these updates on October 1, 2020 by retrospective application. The adoption did not have a material impact on our consolidated financial position or results of operations. We will continue to assess the impact of adoption through the termination date of these Updates on December 31, 2022.

Securities

Securities	12 Months Ended
	Dec. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Securities	SECURITIES The amortized cost and fair value of AFS debt securities for the current period are presented in the table below. There was no ACL in the AFS portfolio during 2020. Accrued interest receivable on AFS debt securities totaled $6.2 million at December 31, 2020 and is excluded from the estimate of credit losses and recorded separately in other assets in the Consolidated Balance Sheets. Accordingly, we have excluded accrued interest receivable from both the fair value and the amortized cost basis of AFS debt securities. TABLE 3.1 (in millions) Amortized Gross Gross Fair Debt Securities AFS: December 31, 2020 U.S. Treasury $ 600 $ — $ — $ 600 U.S. government agencies 172 — — 172 U.S. government-sponsored entities 160 1 — 161 Residential mortgage-backed securities: Agency mortgage-backed securities 959 35 — 994 Agency collateralized mortgage obligations 1,094 31 (1) 1,124 Commercial mortgage-backed securities 361 17 — 378 States of the U.S. and political subdivisions (municipals) 32 — — 32 Other debt securities 2 — — 2 Total debt securities AFS $ 3,380 $ 84 $ (1) $ 3,463 The amortized cost and fair value of debt securities AFS for December 31, 2019 are as follows: TABLE 3.2 (in millions) Amortized Gross Gross Fair Debt Securities AFS: December 31, 2019 U.S. government agencies $ 152 $ — $ (1) $ 151 U.S. government-sponsored entities 225 1 — 226 Residential mortgage-backed securities: Agency mortgage-backed securities 1,310 7 (3) 1,314 Agency collateralized mortgage obligations 1,234 10 (4) 1,240 Commercial mortgage-backed securities 341 6 (2) 345 States of the U.S. and political subdivisions (municipals) 11 — — 11 Other debt securities 2 — — 2 Total debt securities AFS $ 3,275 $ 24 $ (10) $ 3,289 The amortized cost and fair value of HTM debt securities for the current period are presented in the table below. The ACL for the HTM municipal bond portfolio was $0.04 million at December 31, 2020. Accrued interest receivable on HTM debt securities totaled $12.5 million at December 31, 2020 and is excluded from the estimate of credit losses and recorded separately in other assets in the Consolidated Balance Sheets. TABLE 3.3 (in millions) Amortized Gross Gross Fair Debt Securities HTM: December 31, 2020 U.S. Treasury $ 1 $ — $ — $ 1 U.S. government agencies 1 — — 1 U.S. government-sponsored entities 120 1 — 121 Residential mortgage-backed securities: Agency mortgage-backed securities 769 29 — 798 Agency collateralized mortgage obligations 562 17 — 579 Commercial mortgage-backed securities 307 10 — 317 States of the U.S. and political subdivisions (municipals) 1,108 48 — 1,156 Total debt securities HTM $ 2,868 $ 105 $ — $ 2,973 The amortized cost and fair value of HTM debt securities for December 31, 2019 are as follows: TABLE 3.4 (in millions) Amortized Gross Gross Fair Debt Securities HTM: December 31, 2019 U.S. Treasury $ 1 $ — $ — $ 1 U.S. government agencies 1 — — 1 U.S. government-sponsored entities 175 — — 175 Residential mortgage-backed securities: Agency mortgage-backed securities 949 8 (2) 955 Agency collateralized mortgage obligations 721 5 (6) 720 Commercial mortgage-backed securities 308 3 (2) 309 States of the U.S. and political subdivisions (municipals) 1,120 26 (2) 1,144 Total debt securities HTM $ 3,275 $ 42 $ (12) $ 3,305 We did not have any sales during 2020 or 2019. There were no significant gross gains or gross losses realized on securities during the twelve months ended December 31, 2020, 2019 or 2018. As of December 31, 2020, the amortized cost and fair value of debt securities, by contractual maturities, were as follows: TABLE 3.5 Available for Sale Held to Maturity (in millions) Amortized Fair Amortized Fair Due in one year or less $ 642 $ 642 $ 122 $ 123 Due after one year but within five years 113 114 20 20 Due after five years but within ten years 124 125 151 155 Due after ten years 87 86 937 981 966 967 1,230 1,279 Residential mortgage-backed securities: Agency mortgage-backed securities 959 994 769 798 Agency collateralized mortgage obligations 1,094 1,124 562 579 Commercial mortgage-backed securities 361 378 307 317 Total debt securities $ 3,380 $ 3,463 $ 2,868 $ 2,973 Maturities may differ from contractual terms because borrowers may have the right to call or prepay obligations with or without penalties. Periodic payments are received on residential mortgage-backed securities based on the payment patterns of the underlying collateral. Following is information relating to securities pledged: TABLE 3.6 December 31 2020 2019 (dollars in millions) Securities pledged (carrying value): To secure public deposits, trust deposits and for other purposes as required by law $ 5,384 $ 4,494 As collateral for short-term borrowings 402 285 Securities pledged as a percent of total securities 91.4 % 72.8 % At December 31, 2020, there were no holdings of securities of any one issuer, other than U.S. government and its agencies, in any amount greater than 10% of stockholders’ equity. Following are summaries of the fair values of AFS debt securities in an unrealized loss position for which an ACL has not been recorded, segregated by security type and length of continuous loss position: TABLE 3.7 Less than 12 Months 12 Months or More Total (dollars in millions) # Fair Unrealized # Fair Unrealized # Fair Unrealized Debt Securities AFS December 31, 2020 U.S. government agencies 1 $ 13 $ — 16 $ 69 $ — 17 $ 82 $ — U.S. government-sponsored entities 1 25 — — — — 1 25 — Residential mortgage-backed securities: Agency collateralized mortgage obligations 5 130 (1) — — — 5 130 (1) Other debt securities — — — 1 2 — 1 2 — Total 7 $ 168 $ (1) 17 $ 71 $ — 24 $ 239 $ (1) Less than 12 Months 12 Months or More Total (dollars in millions) # Fair Unrealized # Fair Unrealized # Fair Unrealized Debt Securities AFS December 31, 2019 U.S. government agencies 5 $ 48 $ — 15 $ 61 $ (1) 20 $ 109 $ (1) U.S. government-sponsored entities — — — 6 130 — 6 130 — Residential mortgage-backed securities: Agency mortgage-backed securities 13 200 (1) 24 314 (2) 37 514 (3) Agency collateralized mortgage obligations 11 323 (1) 32 205 (3) 43 528 (4) Non-agency collateralized mortgage obligations — — — — — — — — — Commercial mortgage-backed securities 3 114 (2) — — — 3 114 (2) States of the U.S. and political subdivisions (municipals) — — — — — — — — — Other debt securities — — — 1 2 — 1 2 — Total temporarily impaired debt securities AFS 32 $ 685 $ (4) 78 $ 712 $ (6) 110 $ 1,397 $ (10) We evaluated the AFS debt securities that were in an unrealized loss position at December 31, 2020. Based on the credit ratings and implied government guarantee for these securities, we concluded the loss position is temporary and caused by the movement of interest rates. We do not intend to sell the AFS debt securities and it is not more likely than not that we will be required to sell the securities before the recovery of their amortized cost basis. Credit Quality Indicators We use credit ratings to help evaluate the credit quality of our HTM municipal bond portfolio. The ratings are updated quarterly with the last update on December 31, 2020. The remainder of the HTM portfolio is backed by the UST, Fannie Mae, Freddie Mac, FHLB, Ginnie Mae, and the SBA and we have designated these securities as having zero expected credit loss, and therefore, are not subject to an estimate of expected credit loss under CECL. Our municipal bond portfolio with a carrying amount of $1.1 billion as of December 31, 2020 is highly rated with an average rating of AA and 100% of the portfolio rated A or better, while 99% have stand-alone ratings of A or better. All of the securities in the municipal portfolio are general obligation bonds. Geographically, municipal bonds support our primary footprint as 65% of the securities are from municipalities located in the primary states within which we conduct business. The average holding size of the securities in the municipal bond portfolio is $3.5 million. In addition to the strong stand-alone ratings, 62% of the municipalities have some formal credit enhancement insurance that strengthens the creditworthiness of their issue. Management reviews the credit profile of each issuer on a quarterly basis. The credit analysis on the municipal bond portfolio is completed on each bond using: • The bond’s credit rating; • Credit enhancements that improve the bond’s credit rating, for example insurance; and • Moody’s U.S. Bond Defaults and Recoveries, 1970-2019. By using these components, we derive the expected credit loss on the general obligation bond portfolio. We further refine the expected credit loss by factoring in economic forecast data using our Commercial and Industrial Non-Manufacturing PD adjustment as derived through our assessment of the loan portfolio. For the year-to-date period ending December 31, 2020, we had a provision expense of $0.004 million, with no charge-offs or recoveries. The ACL on the HTM portfolio as of December 31, 2020 was $0.04 million. No other securities portfolios had an ACL. At December 31, 2020, there were no securities that were past due or on non-accrual.

Other Securities

Other Securities	12 Months Ended
	Dec. 31, 2020
Banking and Thrift, Interest [Abstract]
Other Securities	OTHER SECURITIES Following is a summary of non-marketable equity securities: TABLE 4.1 December 31 2020 2019 (in millions) Federal Home Loan Bank stock $ 154 $ 256 Federal Reserve Bank stock 124 123 Other non-marketable equity securities — 1 Total non-marketable equity securities $ 278 $ 380

Loans and Leases

Loans and Leases	12 Months Ended
	Dec. 31, 2020
Receivables [Abstract]
Loans and Leases	LOANS AND LEASES The loan and lease portfolio categories were generally unchanged with the CECL adoption. Accrued interest receivable on loans and leases, which totaled $62.9 million at December 31, 2020, is excluded from the estimate of credit losses and recorded separately in other assets in the Consolidated Balance Sheets for both periods and not included in the tables below. Upon adoption of CECL, PCD assets were adjusted to reflect the addition of a $50.3 million ACL and a remaining noncredit discount of $110.0 million included in the amortized cost. At December 31, 2020, the remaining noncredit discount was $50.9 million. Loans and Leases by Portfolio Segment Following is a summary of total loans and leases, net of unearned income: TABLE 5.1 December 31 2020 2019 (in millions) Commercial real estate $ 9,731 $ 8,960 Commercial and industrial 7,214 5,308 Commercial leases 485 432 Other 40 21 Total commercial loans and leases 17,470 14,721 Direct installment 2,020 1,821 Residential mortgages 3,433 3,374 Indirect installment 1,218 1,922 Consumer lines of credit 1,318 1,451 Total consumer loans 7,989 8,568 Total loans and leases, net of unearned income $ 25,459 $ 23,289 The loans and leases portfolio categories are comprised of the following types of loans, where in each case the LGD is dependent on the nature and value of the respective collateral: • Commercial real estate includes both owner-occupied and non-owner-occupied loans secured by commercial properties where operational cash flows on owner-occupied properties or rents received by our borrowers from their tenant(s) on both a property and global basis are the primary default risk drivers, including rents paid by stand-alone business customers for owner-occupied properties; • Commercial and industrial includes loans to businesses that are not secured by real estate where the borrower's leverage and cash flows from operations are the primary default risk drivers. PPP loans are included in the commercial and industrial category and comprise $2.2 billion of this category's outstanding balance at December 31, 2020. The PPP loans are 100% guaranteed by the SBA, which provides a reduced risk of loss to us on these loans; • Commercial leases consist of leases for new or used equipment where the borrower's cash flow from operations is the primary default risk driver; • Other is comprised primarily of credit cards and mezzanine loans where the borrower's cash flow from operations is the primary default risk driver; • Direct installment is comprised of fixed-rate, closed-end consumer loans for personal, family or household use, such as home equity loans and automobile loans where the primary default risk driver is the borrower's employment status and income; • Residential mortgages consist of conventional and jumbo mortgage loans for 1-4 family properties where the primary default risk driver is the borrower's employment status and income; • Indirect installment is comprised of loans originated by approved third parties and underwritten by us, primarily automobile loans where the primary default risk driver is the borrower's employment status and income; and • Consumer lines of credit include home equity lines of credit and consumer lines of credit that are either unsecured or secured by collateral other than home equity where the primary default risk driver is the borrower's employment status and income. The loans and leases portfolio consists principally of loans to individuals and small- and medium-sized businesses within our primary market in seven states and the District of Columbia. Our primary market coverage spans several major metropolitan areas including: Pittsburgh, Pennsylvania; Baltimore, Maryland; Cleveland, Ohio; Washington, D.C.; and Charlotte, Raleigh, Durham and the Piedmont Triad (Winston-Salem, Greensboro and High Point) in North Carolina. During the fourth quarter of 2020, we sold $0.5 billion of indirect installment loans that were previously transferred to loans held for sale. The following table shows occupancy information relating to commercial real estate loans: TABLE 5.2 December 31 2020 2019 (dollars in millions) Commercial real estate: Percent owner-occupied 28.1 % 30.6 % Percent non-owner-occupied 71.9 69.4 We have extended credit to certain directors and executive officers and their related interests. These related-party loans were made in the ordinary course of business under normal credit terms and do not involve more than a normal risk of collection. Following is a summary of the activity for these related-party loans during 2020: TABLE 5.3 (in millions) Balance at beginning of period $ 7 New loans 2 Repayments (2) Balance at end of period $ 7 Credit Quality Management monitors the credit quality of our loan portfolio using several performance measures based on payment activity and borrower performance. We use an internal risk rating assigned to a commercial loan or lease, summarized below. TABLE 5.4 Rating Category Definition Pass in general, the condition of the borrower and the performance of the loan is satisfactory or better Special Mention in general, the condition of the borrower has deteriorated, requiring an increased level of monitoring Substandard in general, the condition of the borrower has significantly deteriorated and the performance of the loan could further deteriorate if deficiencies are not corrected Doubtful in general, the condition of the borrower has significantly deteriorated and the collection in full of both principal and interest is highly questionable or improbable The use of these internally assigned credit quality categories within the commercial loan and lease portfolio permits management’s use of transition matrices to establish the basis for the R&S forecast portion of the credit risk. Our internal credit risk grading system is based on past experiences with similarly graded loans and leases and conforms to regulatory categories. In general, loan and lease risk ratings within each category are reviewed on an ongoing basis according to our policy for each class of loans and leases. Each quarter, management analyzes the resulting ratings, as well as other external statistics and factors such as delinquency, to track the migration performance of the commercial loan and lease portfolio. Loans and leases within the Pass credit category or that migrate toward the Pass credit category generally have a lower risk of loss compared to loans and leases that migrate toward the Substandard or Doubtful credit categories. Accordingly, management applies higher risk factors to Substandard and Doubtful credit categories. The following table summarizes the designated loan rating category by loan class including term loans on an amortized cost basis by origination year: TABLE 5.5 December 31, 2020 2020 2019 2018 2017 2016 Prior Revolving Loans Amortized Cost Basis Total (in millions) COMMERCIAL Commercial Real Estate: Risk Rating: Pass $ 1,879 $ 1,854 $ 1,135 $ 927 $ 888 $ 1,911 $ 163 $ 8,757 Special Mention 9 30 80 158 70 163 4 514 Substandard 4 32 29 81 116 192 6 460 Total commercial real estate 1,892 1,916 1,244 1,166 1,074 2,266 173 9,731 Commercial and Industrial: Risk Rating: Pass 3,286 1,007 590 304 120 311 1,095 6,713 Special Mention 30 23 13 28 10 35 79 218 Substandard 8 26 65 44 6 37 97 283 Total commercial and industrial 3,324 1,056 668 376 136 383 1,271 7,214 Commercial Leases: Risk Rating: Pass 178 134 83 56 5 3 — 459 Special Mention 1 1 4 4 1 2 — 13 Substandard 7 2 2 1 1 — — 13 Total commercial leases 186 137 89 61 7 5 — 485 Other Commercial: Risk Rating: Pass — — — — — 4 35 39 Substandard — — — — — 1 — 1 Total other commercial — — — — — 5 35 40 Total commercial 5,402 3,109 2,001 1,603 1,217 2,659 1,479 17,470 December 31, 2020 2020 2019 2018 2017 2016 Prior Revolving Loans Amortized Cost Basis Total (in millions) CONSUMER Direct Installment: Current 706 337 200 143 171 442 1 2,000 Past due — 1 2 1 2 14 — 20 Total direct installment 706 338 202 144 173 456 1 2,020 Residential Mortgages: Current 1,079 707 283 378 330 603 1 3,381 Past due 1 5 7 4 6 29 — 52 Total residential mortgages 1,080 712 290 382 336 632 1 3,433 Indirect Installment: Current 372 260 332 147 67 27 — 1,205 Past due 1 3 4 2 2 1 — 13 Total indirect installment 373 263 336 149 69 28 — 1,218 Consumer Lines of Credit: Current 4 7 8 3 5 127 1,146 1,300 Past due — — — — — 15 3 18 Total consumer lines of credit 4 7 8 3 5 142 1,149 1,318 Total consumer 2,163 1,320 836 678 583 1,258 1,151 7,989 Total loans and leases $ 7,565 $ 4,429 $ 2,837 $ 2,281 $ 1,800 $ 3,917 $ 2,630 $ 25,459 We use delinquency transition matrices within the consumer and other loan classes to establish the basis for the R&S forecast portion of the credit risk. Each month, management analyzes payment and volume activity, FICO scores and Debt-to-Income (DTI) scores and other external factors such as unemployment, to determine how consumer loans are performing. The following tables present the December 31, 2019 summary of our commercial loans and leases by credit quality category segregated by loans and leases originated and loans acquired, prior to the adoption of CECL: TABLE 5.6 Commercial Loan and Lease Credit Quality Categories (in millions) Pass Special Substandard Doubtful Total Originated Loans and Leases December 31, 2019 Commercial real estate $ 6,821 $ 171 $ 121 $ 1 $ 7,114 Commercial and industrial 4,768 149 144 2 5,063 Commercial leases 423 3 6 — 432 Other 20 — 1 — 21 Total originated commercial loans and leases $ 12,032 $ 323 $ 272 $ 3 $ 12,630 Loans Acquired in a Business Combination December 31, 2019 Commercial real estate $ 1,603 $ 116 $ 127 $ — $ 1,846 Commercial and industrial 201 19 25 — 245 Total commercial loans acquired in a business combination $ 1,804 $ 135 $ 152 $ — $ 2,091 Following is a table showing the December 31, 2019 consumer loans by payment status: TABLE 5.7 Consumer Loan Credit Quality by Payment Status (in millions) Performing Non-Performing Total Originated Loans December 31, 2019 Direct installment $ 1,745 $ 13 $ 1,758 Residential mortgages 2,978 17 2,995 Indirect installment 1,919 3 1,922 Consumer lines of credit 1,086 6 1,092 Total originated consumer loans $ 7,728 $ 39 $ 7,767 Loans Acquired in a Business Combination December 31, 2019 Direct installment $ 63 $ — $ 63 Residential mortgages 379 — 379 Consumer lines of credit 358 1 359 Total consumer loans acquired in a business combination $ 800 $ 1 $ 801 Non-Performing and Past Due The following tables provide an analysis of the aging of loans by class. TABLE 5.8 (in millions) 30-89 Days ≥ 90 Days Non- Total Current Total Non-accrual with No ACL Loans and Leases December 31, 2020 Commercial real estate $ 13 $ — $ 85 $ 98 $ 9,633 $ 9,731 $ 36 Commercial and industrial 8 — 44 52 7,162 7,214 16 Commercial leases 2 — 2 4 481 485 — Other — — 1 1 39 40 — Total commercial loans and leases 23 — 132 155 17,315 17,470 52 Direct installment 7 2 11 20 2,000 2,020 — Residential mortgages 23 11 18 52 3,381 3,433 — Indirect installment 10 1 2 13 1,205 1,218 — Consumer lines of credit 9 2 7 18 1,300 1,318 — Total consumer loans 49 16 38 103 7,886 7,989 — Total loans and leases $ 72 $ 16 $ 170 $ 258 $ 25,201 $ 25,459 $ 52 (in millions) 30-89 Days > 90 Days Non- Total Current Total Originated Loans and Leases December 31, 2019 Commercial real estate $ 10 $ — $ 26 $ 36 $ 7,078 $ 7,114 Commercial and industrial 9 — 28 37 5,026 5,063 Commercial leases 5 — 1 6 426 432 Other — — 1 1 20 21 Total commercial loans and leases 24 — 56 80 12,550 12,630 Direct installment 7 1 7 15 1,743 1,758 Residential mortgages 12 2 8 22 2,973 2,995 Indirect installment 15 1 3 19 1,903 1,922 Consumer lines of credit 5 1 3 9 1,083 1,092 Total consumer loans 39 5 21 65 7,702 7,767 Total originated loans and leases $ 63 $ 5 $ 77 $ 145 $ 20,252 $ 20,397 (in millions) 30-89 Days ≥ 90 Days Non- Total Current (Discount)/ Total Loans Acquired in a Business Combination December 31, 2019 Commercial real estate $ 12 $ 28 $ 3 $ 43 $ 1,942 $ (139) $ 1,846 Commercial and industrial 2 3 — 5 259 (19) 245 Total commercial loans 14 31 3 48 2,201 (158) 2,091 Direct installment 3 — — 3 60 — 63 Residential mortgages 8 4 — 12 382 (15) 379 Consumer lines of credit 7 2 1 10 357 (8) 359 Total consumer loans 18 6 1 25 799 (23) 801 Total loans acquired in a business combination $ 32 $ 37 $ 4 $ 73 $ 3,000 $ (181) $ 2,892 (1) Prior to the adoption of CECL on January 1, 2020, loans acquired in a business combination were considered performing upon acquisition, regardless of whether the customer was contractually delinquent, if we could reasonably estimate the timing and amount of expected cash flows on such loans. In these instances, we did not consider acquired contractually delinquent loans to be non-accrual or non-performing and continued to recognize interest income on these loans using the accretion method. After the adoption of CECL on January 1, 2020 loans acquired in a business combination are considered non-accrual or non-performing when, due to credit deterioration or other factors, we determine we are no longer able to reasonably estimate the timing and amount of expected cash flows on such loans. We do not recognize interest income on loans acquired in a business combination considered non-accrual or non-performing. (2) Past due information for loans acquired in a business combination is based on the contractual balance outstanding at December 31, 2019. Following is a summary of non-performing assets: TABLE 5.9 December 31 2020 2019 (dollars in millions) Non-accrual loans $ 170 $ 81 Troubled debt restructurings — 22 Total non-performing loans 170 103 Other real estate owned 10 26 Total non-performing assets $ 180 $ 129 Asset quality ratios: Non-performing loans / total loans and leases 0.67 % 0.44 % Non-performing loans assets + 90 days past due + OREO / total loans and leases + OREO 0.77 0.73 The carrying value of residential-secured consumer OREO held as a result of obtaining physical possession upon completion of a foreclosure or through completion of a deed in lieu of foreclosure amounted to $2.5 million at December 31, 2020 and $3.3 million at December 31, 2019. The recorded investment of residential-secured consumer OREO for which formal foreclosure proceedings are in process at December 31, 2020 and December 31, 2019 totaled $8.2 million and $9.2 million, respectively. During 2020, we extended the residential mortgage foreclosure moratorium beyond the requirements for government-backed loans, under the CARES Act, to all residential mortgage loan customers. Approximately $91.4 million of commercial loans are collateral dependent at December 31, 2020. Repayment is expected to be substantially through the operation or sale of the collateral on the loan. These loans are primarily secured by business assets or commercial real estate. Troubled Debt Restructurings TDRs are loans whose contractual terms have been modified in a manner that grants a concession to a borrower experiencing financial difficulties. TDRs typically result from loss mitigation activities and could include the extension of a maturity date, interest rate reduction, principal forgiveness, deferral or decrease in payments for a period of time and other actions intended to minimize the economic loss and to avoid foreclosure or repossession of collateral. Consistent with the CARES Act and interagency bank regulatory guidance which allows temporary relief for current borrowers affected by COVID-19, we are working with borrowers and granting certain modifications through programs related to COVID-19 relief. As of December 31, 2020, we had $397 million in loans that have been granted short-term modifications as a result of financial disruptions associated with the COVID-19 pandemic. Also, consistent with the CARES Act and the interagency bank regulatory guidelines, such modifications are not included in our TDR totals. Following is a summary of the composition of total TDRs: TABLE 5.10 December 31 2020 2019 (in millions) Accruing $ 58 $ 41 Non-accrual 33 15 Total TDRs $ 91 $ 56 TDRs that are accruing and performing include loans that met the criteria for non-accrual of interest prior to restructuring for which we can reasonably estimate the timing and amount of the expected cash flows on such loans and for which we expect to fully collect the new carrying value of the loans. During 2020, we returned to accruing status $7.7 million in restructured residential mortgage loans that have consistently met their modified obligations for more than six months. TDRs that are on non-accrual are not placed on accruing status until all delinquent principal and interest have been paid and the ultimate collectability of the remaining principal and interest is reasonably assured. Some loan modifications classified as TDRs may not ultimately result in the full collection of principal and interest, as modified, and may result in potential incremental losses which are factored into the ACL. Commercial loans over $1.0 million whose terms have been modified in a TDR are generally placed on non-accrual, individually analyzed and measured based on the fair value of the underlying collateral. Our ACL includes specific reserves for commercial TDRs of $2.8 million at December 31, 2020, compared to less than $0.5 million at December 31, 2019, and pooled reserves for individual loans of $2.5 million and $0.8 million for those same periods, respectively, based on loan segment LGD. Upon default, the amount of the recorded investment in the TDR in excess of the fair value of the collateral, less estimated selling costs, is generally considered a confirmed loss and is charged-off against the ACL. All other classes of loans whose terms have been modified in a TDR are pooled and measured based on the loan segment LGD. Our ACL included pooled reserves for these classes of loans of $4.1 million for both December 31, 2020 and 2019. Upon default of an individual loan, our charge-off policy is followed for that class of loan. Following is a summary of TDR loans, by class, for loans that were modified during the periods indicated: TABLE 5.11 Year Ended December 31 2020 2019 (dollars in millions) Number Pre-Modification Post- Number Pre-Modification Post- Commercial real estate 30 $ 18 $ 8 20 $ 5 $ 5 Commercial and industrial 19 2 1 23 5 3 Other 1 — — — — — Total commercial loans 50 20 9 43 10 8 Direct installment 68 4 4 65 3 3 Residential mortgages 24 3 3 18 3 3 Consumer lines of credit 45 2 1 27 2 1 Total consumer loans 137 9 8 110 8 7 Total 187 $ 29 $ 17 153 $ 18 $ 15 The items in the above tables have been adjusted for loans that have been paid off and/or sold. Following is a summary of TDRs, by class, for which there was a payment default, excluding loans that have been paid off and/or sold. Default occurs when a loan is 90 days or more past due and is within 12 months of restructuring. TABLE 5.12 Year Ended December 31 2020 (dollars in millions) Number Recorded Commercial real estate 8 $ 3 Commercial and industrial 2 — Total commercial loans 10 3 Direct installment 12 — Residential mortgages 4 — Consumer lines of credit 4 — Total consumer loans 20 — Total 30 $ 3 Following is a summary of originated TDRs, by class, for which there was a payment default, excluding loans that have been paid off and/or sold. TABLE 5.13 Year Ended December 31 2019 (dollars in millions) Number Recorded Commercial real estate 5 $ 1 Commercial and industrial 1 — Total commercial loans 6 1 Direct installment 5 — Residential mortgages 2 — Consumer lines of credit 1 — Total consumer loans 8 — Total 14 $ 1 Loans Acquired in a Business Combination Prior to January 1, 2020, all loans acquired in a business combination were initially recorded at fair value at the acquisition date with no associated ACL. Refer to the Loans Acquired in a Business Combination section in Note 1 to the Consolidated Financial Statements.

Allowance for Credit Losses on

Allowance for Credit Losses on Loans and Leases	12 Months Ended
	Dec. 31, 2020
Receivables [Abstract]
Allowance for Credit Losses on Loans and Leases	ALLOWANCE FOR CREDIT LOSSES ON LOANS AND LEASESBeginning January 1, 2020, the former incurred loss method was replaced with the CECL method to calculate estimated loan loss. The ACL addresses credit losses expected in the existing loan and lease portfolio and is presented as a reserve against loans and leases on the Consolidated Balance Sheets. Loan and lease losses are charged off against the ACL, with recoveries of amounts previously charged off credited to the ACL. Provisions for credit losses are charged to operations based on management’s periodic evaluation of the appropriate level of the ACL. Included in Table 6.1 is the impact to the ACL from our CECL (ASC 326) adoption on January 1, 2020. All prior periods are presented using the incurred loss method which was the accounting method in place at the time of the respective financial statements. Following is a summary of changes in the ACL, by loan and lease class: TABLE 6.1 (in millions) Balance at Charge- Recoveries Net Provision ASC 326 Adoption Impact Initial ACL on PCD Loans Balance at Year Ended December 31, 2020 Commercial real estate $ 60 $ (31) $ 7 $ (24) $ 67 $ 38 $ 40 $ 181 Commercial and industrial 53 (32) 7 (25) 41 8 4 81 Commercial leases 11 (1) — (1) 7 — — 17 Other 9 (4) 1 (3) 4 (9) — 1 Total commercial loans and leases 133 (68) 15 (53) 119 37 44 280 Direct installment 13 (1) 1 — 2 10 1 26 Residential mortgages 22 (2) 1 (1) 3 6 4 34 Indirect installment 19 (8) 4 (4) (6) 2 — 11 Consumer lines of credit 9 (2) — (2) 4 — 1 12 Total consumer loans 63 (13) 6 (7) 3 18 6 83 Total allowance for credit losses on loans and leases $ 196 $ (81) $ 21 $ (60) $ 122 $ 55 $ 50 $ 363 Allowance for unfunded loan commitments 3 — — — 1 10 — 14 Total allowance for credit losses on loans and leases and allowance for unfunded loan commitments $ 199 $ (81) $ 21 $ (60) $ 123 $ 65 $ 50 $ 377 Following is a summary of changes in the AULC by portfolio segment: TABLE 6.2 Year Ended December 31 2020 (in millions) Balance at beginning of period $ 3 Provision for unfunded loan commitments and letters of credit: Commercial portfolio 1 Consumer portfolio — ASC 326 adoption impact: Commercial portfolio 8 Consumer portfolio 2 Balance at end of period $ 14 This expected loss model takes into consideration the expected credit losses over the expected life of the loan compared to the incurred loss model under the prior standard. At the time of CECL adoption, we recorded a one-time cumulative-effect adjustment of $50.6 million as a reduction to Retained Earnings. The ACL balance increased by $105 million and included a “gross-up" to PCI loan balances and the ACL of $50 million. Included in the CECL adoption impact was a Day 1 increase to our AULC of $10 million. The model used to calculate the ACL is dependent on the portfolio composition and credit quality, as well as historical experience, current conditions and forecasts of economic conditions and interest rates. Specifically, the following considerations are incorporated into the ACL calculation: • a third-party macroeconomic forecast scenario; • a 24-month R&S forecast period for macroeconomic factors with a reversion to the historical mean on a straight-line basis over a 12-month period; and • the historical through the cycle mean was calculated using an expanded period to include a prior recessionary period. COVID-19 Impacts on the ACL Beginning in March 2020, the broader economy experienced a significant deterioration in the macroeconomic environment driven by the COVID-19 pandemic resulting in notable adverse changes to forecasted economic variables utilized in our ACL modeling process. Based on these changes, we utilized a third-party pandemic recessionary scenario through September 30, 2020 for ACL modeling purposes. For December 31, 2020, we utilized a third-party consensus macroeconomic forecast due to the improving macroeconomic environment. This scenario captures forecasted macroeconomic variables as of mid-December to ensure our ACL calculation considers the most recently available macroeconomic data in a quickly evolving environment at quarter-end. Macroeconomic variables that we utilized from this scenario for our ACL calculation as of December 31, 2020 included but were not limited to: (i) gross domestic product, which reflects growth of 4% in 2021, (ii) the Dow Jones Total Stock Market Index, which grows steadily throughout the R&S forecast period, (iii) unemployment, which steadily declines and averages 6% over the R&S forecast period and (iv) the Volatility Index, which remains stable over the R&S. The ACL of $363.1 million at December 31, 2020 increased $167.2 million, or 85.4%, from December 31, 2019 and reflects the Day 1 CECL adoption increase to the ACL of $105.3 million on January 1, 2020. The additional increase was primarily attributed to qualitative adjustments such as economic modeling uncertainty given the COVID-related environment and loan deferral activity as prescribed in the CARES Act and by the banking regulators. Our ending ACL coverage ratio at December 31, 2020 was 1.43%. Total provision for credit losses for the year ended December 31, 2020 was $122.8 million. Net charge-offs were $59.8 million during 2020, compared to $28.3 million during 2019, with the increase primarily due to commercial charge-offs within portfolios and industries most impacted by COVID-19 such as retail or hospitality-related commercial real estate. While elevated from 2019, net charge-offs of 24 basis points of average loans for 2020 remained at historically reasonable levels. Following is a summary of changes in the ACL, by loan and lease class: TABLE 6.3 (in millions) Balance at Charge- Recoveries Net Provision Balance at Year Ended December 31, 2019 Commercial real estate $ 55 $ (4) $ 4 $ — $ 5 $ 60 Commercial and industrial 49 (10) 4 (6) 10 53 Commercial leases 8 — — — 3 11 Other 2 (3) — (3) 3 2 Total commercial loans and leases 114 (17) 8 (9) 21 126 Direct installment 14 (1) — (1) — 13 Residential mortgages 20 (2) — (2) 4 22 Indirect installment 15 (11) 4 (7) 11 19 Consumer lines of credit 10 (2) — (2) 1 9 Total consumer loans 59 (16) 4 (12) 16 63 Total allowance on originated loans and leases 173 (33) 12 (21) 37 189 Loans acquired in a business combination 7 (9) 2 (7) 7 7 Total allowance for credit losses $ 180 $ (42) $ 14 $ (28) $ 44 $ 196 Year Ended December 31, 2018 Commercial real estate $ 50 $ (7) $ 3 $ (4) $ 9 $ 55 Commercial and industrial 52 (20) 2 (18) 15 49 Commercial leases 5 (3) — (3) 6 8 Other 2 (4) — (4) 4 2 Total commercial loans and leases 109 (34) 5 (29) 34 114 Direct installment 21 (17) 2 (15) 8 14 Residential mortgages 16 — — — 4 20 Indirect installment 12 (9) 4 (5) 8 15 Consumer lines of credit 10 (3) — (3) 3 10 Total consumer loans 59 (29) 6 (23) 23 59 Total allowance on originated loans and leases 168 (63) 11 (52) 57 173 Loans acquired in a business combination 7 (7) 3 (4) 4 7 Total allowance for credit losses $ 175 $ (70) $ 14 $ (56) $ 61 $ 180 Following is a summary of the individual and collective ACL and corresponding loan and lease balances by class: TABLE 6.4 Allowance for Credit Losses Loans and Leases Outstanding (in millions) Individually Collectively Loans and Individually Collectively December 31, 2019 Commercial real estate $ 2 $ 58 $ 7,114 $ 13 $ 7,101 Commercial and industrial 2 51 5,063 17 5,046 Commercial leases — 11 432 — 432 Other — 2 21 — 21 Total commercial loans and leases 4 122 12,630 30 12,600 Direct installment — 13 1,758 — 1,758 Residential mortgages — 22 2,995 — 2,995 Indirect installment — 19 1,922 — 1,922 Consumer lines of credit — 9 1,092 — 1,092 Total consumer loans — 63 7,767 — 7,767 Total $ 4 $ 185 $ 20,397 $ 30 $ 20,367 The above table excludes loans acquired in a business combination that were pooled into groups of loans for evaluating impairment.

Loan Servicing

Loan Servicing	12 Months Ended
	Dec. 31, 2020
Transfers and Servicing [Abstract]
Loan Servicing	LOAN SERVICING Mortgage Loan Servicing We retain the servicing rights on certain mortgage loans sold. The unpaid principal balance of mortgage loans serviced for others is listed below: TABLE 7.1 December 31 2020 2019 (in millions) Mortgage loans sold with servicing retained $ 4,653 $ 4,686 The following table summarizes activity relating to mortgage loans sold with servicing retained: TABLE 7.2 Year Ended December 31 2020 2019 2018 (in millions) Mortgage loans sold with servicing retained $ 1,636 $ 1,381 $ 1,060 Pretax gains resulting from above loan sales (1) 70 32 19 Mortgage servicing fees (1) 12 11 9 (1) Recorded in mortgage banking operations on the Consolidated Statements of Income. Following is a summary activity relating to MSRs: TABLE 7.3 Year Ended December 31 2020 2019 2018 (in millions) Balance at beginning of period $ 42.6 $ 36.8 $ 29.1 Additions 16.0 14.3 12.5 Payoffs and curtailments (14.8) (5.0) (1.8) (Impairment) charge / recovery (5.8) (1.0) (0.5) Amortization (2.4) (2.5) (2.5) Balance at end of period $ 35.6 $ 42.6 $ 36.8 Fair value, beginning of period $ 45.2 $ 41.1 $ 32.4 Fair value, end of period 35.6 45.2 41.1 The fair value of MSRs is highly sensitive to changes in assumptions and is determined by estimating the present value of the asset’s future cash flows utilizing market-based prepayment rates, discount rates and other assumptions validated through comparison to trade information, industry surveys and with the use of independent third-party valuations. Changes in prepayment speed assumptions have the most significant impact on the fair value of MSRs. Generally, as interest rates decline, mortgage loan prepayments accelerate due to increased refinance activity, which results in a decrease in the fair value of MSRs and as interest rates increase, mortgage loan prepayments decline, which results in an increase in the fair value of MSRs. Measurement of fair value is limited to the conditions existing and the assumptions utilized as of a particular point in time, and those assumptions may not be appropriate if they are applied at a different time. Following is a summary of the sensitivity of the fair value of MSRs to changes in key assumptions: TABLE 7.4 December 31 2020 2019 (dollars in millions) Weighted average life (months) 66.6 78.9 Constant prepayment rate (annualized) 13.4 % 10.6 % Discount rate 9.5 % 9.7 % Effect on fair value due to change in interest rates: +0.25% $ 2 $ 3 +0.50% 4 5 -0.25% (2) (3) -0.50% (3) (5) The sensitivity calculations above are hypothetical and should not be considered to be predictive of future performance. Changes in fair value based on adverse changes in assumptions generally cannot be extrapolated because the relationship of the changes in assumptions to fair value may not be linear. Also, in this table, the effects of an adverse variation in a particular assumption on the fair value of MSRs is calculated without changing any other assumptions, while in reality, changes in one factor may result in changing another, which may magnify or contract the effect of the change. We had a $7.3 million valuation allowance for MSRs as of December 31, 2020, compared to $1.5 million at December 31, 2019. SBA-Guaranteed Loan Servicing We retain the servicing rights on SBA-guaranteed loans sold to investors. The standard sale structure under the SBA Secondary Participation Guaranty Agreement provides for us to retain a portion of the cash flow from the interest payment received on the SBA guaranteed portion of the loan, which is commonly known as a servicing spread. The unpaid principal balance of SBA-guaranteed loans serviced for investors was as follows: TABLE 7.5 December 31 2020 2019 (in millions) SBA loans sold to investors with servicing retained $ 217 $ 225 The following table summarizes activity relating to SBA loans sold with servicing retained: TABLE 7.6 Year Ended December 31 2020 2019 2018 (in millions) SBA loans sold with servicing retained $ 33 $ 23 $ 41 Pretax gains resulting from above loan sales (1) 3 2 4 SBA servicing fees (1) 2 2 3 (1) Recorded in non-interest income. Following is a summary of the activity in SBA servicing rights: TABLE 7.7 Year Ended December 31 2020 2019 2018 (in millions) Balance at beginning of period $ 3 $ 4 $ 5 Additions 1 — 1 Payoffs, curtailments and amortization (1) (1) (1) Impairment charge — — (1) Balance at end of period $ 3 $ 3 $ 4 Fair value, beginning of period $ 3 $ 4 $ 5 Fair value, end of period 3 3 4 Following is a summary of key assumptions and the sensitivity of the SBA servicing rights to changes in these assumptions. The declines in fair values were immaterial in the scenarios presented. TABLE 7.8 December 31 2020 2019 (dollars in millions) Weighted average life (months) 38 42 Constant prepayment rate 17.8 % 16.8 % Discount rate 13.2 16.2 Decline in fair value due to change in interest rates: 1% adverse change $ (0.1) $ (0.1) 2% adverse change (0.1) (0.1) Decline in fair value due to change in constant prepayment rates: 10% adverse change (0.1) (0.1) 20% adverse change (0.1) (0.3) We had a valuation allowance for SBA servicing rights as of December 31, 2020 of $1.1 million, compared to $1.2 million at December 31, 2019. Other Loan Servicing During the fourth quarter of 2020, we sold $0.5 billion in indirect auto loans with servicing retained. The servicing asset totaled $0.7 million at December 31, 2020.

Premises and Equipment

Premises and Equipment	12 Months Ended
	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Premises and Equipment	PREMISES AND EQUIPMENT Following is a summary of premises and equipment: TABLE 8.1 December 31 2020 2019 (in millions) Land $ 57 $ 62 Premises 231 233 Equipment 311 276 599 571 Accumulated depreciation (267) (238) Total premises and equipment, net $ 332 $ 333 Depreciation expense for premises and equipment is presented in the following table: TABLE 8.2 December 31 2020 2019 2018 (in millions) Depreciation expense for premises and equipment $ 43 $ 42 $ 39

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets	12 Months Ended
	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangible Assets	GOODWILL AND OTHER INTANGIBLE ASSETS The following table shows a rollforward of goodwill by line of business: TABLE 9.1 (in millions) Community Wealth Insurance Total Balance at January 1, 2019 $ 2,231 $ 8 $ 16 $ 2,255 Goodwill (deductions) additions — — 7 7 Balance at December 31, 2019 2,231 8 23 2,262 Goodwill (deductions) additions — — — — Balance at December 31, 2020 $ 2,231 $ 8 $ 23 $ 2,262 There were no changes to goodwill during 2020. The addition of goodwill for the Insurance segment in 2019 was the result of the FNIA acquisitions of a Maryland-based insurance agency on December 17, 2018 and a North Carolina-based insurance agency on June 17, 2019. The following table shows a summary of core deposit intangibles and customer renewal lists: TABLE 9.2 (in millions) Core Customer Total December 31, 2020 Gross carrying amount $ 197 $ 18 $ 215 Accumulated amortization (149) (12) (161) Net carrying amount $ 48 $ 6 $ 54 December 31, 2019 Gross carrying amount $ 196 $ 18 $ 214 Accumulated amortization (136) (11) (147) Net carrying amount $ 60 $ 7 $ 67 Core deposit intangibles are being amortized primarily over 10 years using accelerated methods. Customer renewal lists are being amortized over their estimated useful lives, which range from eight The following table summarizes amortization expense recognized: TABLE 9.3 December 31 2020 2019 2018 (in millions) Amortization expense $ 13 $ 14 $ 16 Following is a summary of the expected amortization expense on finite-lived intangible assets, assuming no new additions, for each of the five years following December 31, 2020: TABLE 9.4 (in millions) 2021 $ 12 2022 10 2023 10 2024 8 2025 7 Total $ 47

Operating Leases

Operating Leases	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Operating Leases	OPERATING LEASES We have operating leases primarily for certain branches, office space, land, and office equipment. Our operating leases expire at various dates through the year 2046 and generally include one or more options to renew. The exercise of lease renewal options is at our sole discretion. As of December 31, 2020, we had operating lease right-of-use assets and operating lease liabilities of $126.7 million and $134.4 million, respectively. Our operating lease agreements do not contain any material residual value guarantees or material restrictive covenants. As of December 31, 2020, we have certain operating lease agreements, primarily for administrative office space, that have not yet commenced. At commencement, it is expected that these leases will add approximately $18.2 million in right-of-use assets and other liabilities. These operating leases are currently expected to commence in 2021 with lease terms of 16 years. The components of lease expense were as follows: TABLE 10.1 Twelve Months Ended (dollars in millions) 2020 2019 Operating lease cost $ 27 $ 27 Short-term lease cost 1 1 Variable lease cost 3 4 Total lease cost $ 31 $ 32 Rental expense totaled $33.2 million for 2018. Other information related to leases is as follows: TABLE 10.2 Twelve Months Ended (dollars in millions) 2020 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 26 $ 26 Right-of-use assets obtained in exchange for lease obligations: Operating leases 20 25 Weighted average remaining lease term (years): Operating leases 9.45 9.61 Weighted average discount rate: Operating leases 2.6 % 3.0 % Maturities of operating lease liabilities were as follows: TABLE 10.3 (in millions) December 31, 2021 $ 25 2022 21 2023 17 2024 15 2025 12 Later years 64 Total lease payments 154 Less: imputed interest (20) Present value of lease liabilities $ 134 As a lessor we offer commercial leasing services to customers in need of new or used equipment primarily within our market areas of Pennsylvania, Ohio, Maryland, North Carolina, South Carolina and West Virginia. Additional information relating to commercial leasing is provided in Note 5, “Loans and Leases” in the Notes to Consolidated Financial Statements.

Variable Interest Entities

Variable Interest Entities	12 Months Ended
	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Variable Interest Entities	VARIABLE INTEREST ENTITIESWe evaluate our interest in certain entities to determine if these entities meet the definition of a VIE and whether we are the primary beneficiary and required to consolidate the entity based on the variable interest we held both at inception and when there is a change in circumstances that requires a reconsideration. Unconsolidated VIEs The following tables provide a summary of the assets and liabilities included in our Consolidated Financial Statements, as well as the maximum exposure to losses, associated with our interests related to VIEs for which we hold an interest, but are not the primary beneficiary, at December 31, 2020 and December 31, 2019. TABLE 11.1 (in millions) Total Assets Total Liabilities Maximum Exposure to Loss December 31, 2020 Trust preferred securities (1) $ 1 $ 66 $ — Affordable housing tax credit partnerships 119 45 119 Other investments 26 8 26 Total $ 146 $ 119 $ 145 December 31, 2019 Trust preferred securities (1) $ 1 $ 66 $ — Affordable housing tax credit partnerships 120 60 120 Other investments 33 10 33 Total $ 154 $ 136 $ 153 (1) Represents our investment in unconsolidated subsidiaries. Trust-Preferred Securities We have certain wholly-owned trusts whose assets, liabilities, equity, income and expenses are not included within our Consolidated Financial Statements. These trusts have been formed for the sole purpose of issuing TPS, from which the proceeds are then invested in our junior subordinated debentures, which are reflected in our Consolidated Balance Sheets as subordinated notes. The TPS are the obligations of the trusts, and as such, are not consolidated within our Consolidated Financial Statements. See the Borrowings footnote for additional information relating to our TPS. Each issue of the junior subordinated debentures has an interest rate equal to the corresponding TPS distribution rate. We have the right to defer payment of interest on the debentures at any time, or from time-to-time for a period not exceeding five years provided that no extension period may extend beyond the stated maturity of the related debentures. During any such extension period, distributions to the TPS will also be deferred and our ability to pay dividends on our common stock will be restricted. Periodic cash payments and payments upon liquidation or redemption with respect to TPS are guaranteed by us to the extent of funds held by the trusts. The guarantee ranks subordinate and junior in right of payment to all of our indebtedness to the same extent as the junior subordinated debt. The guarantee does not place a limitation on the amount of additional indebtedness that may be incurred by us. Affordable Housing Tax Credit Partnerships We make equity investments as a limited partner in various partnerships that sponsor affordable housing projects utilizing the LIHTC pursuant to Section 42 of the Internal Revenue Code. The purpose of these investments is to support initiatives associated with the CRA while earning a satisfactory return. The activities of these LIHTC partnerships include the development and operation of multi-family housing that is leased to qualifying residential tenants. These partnerships are generally located in communities where we have a banking presence and meet the definition of a VIE; however, we are not the primary beneficiary of the entities, as the general partner or managing member has both the power to direct the activities that most significantly impact the economic performance of the entities and the obligation to absorb losses beyond our own equity investment. We record our investment in LIHTC partnerships as a component of other assets. We use the proportional amortization method to account for a majority of our investments in LIHTC partnerships. Investments that do not meet the requirements of the proportional amortization method are recognized using the equity method. Amortization related to investments under the proportional amortization method are recorded on a net basis as a component of the provision of income taxes on the Consolidated Statements of Income, while write-downs and losses related to investments under the equity method are included in non-interest expense. The following table presents the balances of our affordable housing tax credit investments and related unfunded commitments: TABLE 11.2 December 31 2020 2019 (in millions) Proportional amortization method investments included in other assets $ 71 $ 55 Equity method investments included in other assets 3 5 Total LIHTC investments included in other assets $ 74 $ 60 Unfunded LIHTC commitments $ 45 $ 60 The following table summarizes the impact of these LIHTC investments on specific line items of our Consolidated Statements of Income: TABLE 11.3 Year Ended December 31 (in millions) 2020 2019 2018 Non-interest income: Amortization of tax credit investments under equity method, net of tax benefit $ 1 $ 1 $ 2 Provision for income taxes: Amortization of LIHTC investments under proportional method $ 11 $ 8 $ 5 Low-income housing tax credits (12) (9) (6) Other tax benefits related to tax credit investments (2) (2) (1) Total provision for income taxes $ (3) $ (3) $ (2) Other Investments Other investments we also consider to be unconsolidated VIE’s include investments in Small Business Investment Companies, Historic Tax Credit Investments, and other equity method investments.

Deposits

Deposits	12 Months Ended
	Dec. 31, 2020
Deposits [Abstract]
Deposits	DEPOSITS Following is a summary of deposits: TABLE 12.1 December 31 2020 2019 (in millions) Non-interest-bearing demand $ 9,042 $ 6,384 Interest-bearing demand 13,157 11,049 Savings 3,261 2,625 Certificates and other time deposits: Less than $100,000 1,895 2,262 $100,000 through $250,000 1,173 1,494 Greater than $250,000 594 972 Total certificates and other time deposits 3,662 4,728 Total deposits $ 29,122 $ 24,786 Following is a summary of the scheduled maturities of certificates and other time deposits for the years following December 31, 2020: TABLE 12.2 (in millions) 2021 $ 2,464 2022 683 2023 236 2024 124 2025 99 Later years 56 Total $ 3,662

Short-Term Borrowings

Short-Term Borrowings	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Short-Term Borrowings	SHORT-TERM BORROWINGS Following is a summary of short-term borrowings: TABLE 13.1 December 31 2020 2019 (in millions) Securities sold under repurchase agreements $ 403 $ 278 Federal Home Loan Bank advances 1,280 2,255 Federal funds purchased — 575 Subordinated notes 121 108 Total short-term borrowings $ 1,804 $ 3,216 Borrowings with original maturities of one year or less are classified as short-term. Securities sold under repurchase agreements are comprised of customer repurchase agreements, which are sweep accounts with next-day maturities utilized by larger commercial customers to earn interest on their funds. Securities are pledged to these customers in an amount at least equal to the outstanding balance. We did not have any short-term FHLB advances with overnight maturities as of December 31, 2020 or December 31, 2019. At December 31, 2020, $1.3 billion, or 100.0%, of the short-term FHLB advances were swapped to a fixed rate with maturities in 2021. This compares to $1.5 billion, or 64.5%, as of December 31, 2019. During the second half of 2020, we terminated hedges related to $225.0 million of higher-rate short-term FHLB borrowings, which resulted in hedge termination costs of $8.9 million reported in other non-interest income on the Consolidated Statements of Income. The following represents weighted average interest rates on short-term borrowings: TABLE 13.2 December 31 2020 2019 2018 Year-to-date average 1.53 % 2.24 % 1.89 % Period-end 1.57 1.76 2.49

Long-Term Borrowings

Long-Term Borrowings	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Long-Term Borrowings	LONG-TERM BORROWINGS Following is a summary of long-term borrowings: TABLE 14.1 December 31 2020 2019 (in millions) Federal Home Loan Bank advances $ 400 $ 935 Senior notes 299 — Subordinated notes 81 90 Junior subordinated debt 66 66 Other subordinated debt 249 249 Total long-term borrowings $ 1,095 $ 1,340 Scheduled annual maturities for the long-term borrowings for the years following December 31, 2020 are as follows: TABLE 14.2 (in millions) 2021 $ 427 2022 16 2023 334 2024 1 2025 104 Later years 213 Total $ 1,095 Federal Home Loan Bank advances Our banking affiliate has available credit with the FHLB of $8.3 billion, of which $1.7 billion was utilized as of December 31, 2020. These advances are secured by loans collateralized by residential mortgages, home equity lines of credit, commercial real estate and FHLB stock and are scheduled to mature in various amounts periodically through the year 2021. Effective interest rates paid on the long-term advances ranged from 0.30% to 0.34% for the year ended December 31, 2020 and 1.62% to 2.71% for the year ended December 31, 2019. During the second half of 2020, we reduced higher-rate outstanding long-term FHLB borrowings by $490.0 million, which resulted in a loss on early debt extinguishment of $16.7 million reported in other non-interest income on the Consolidated Statements of Income. Subordinated notes Subordinated notes are unsecured and subordinated to our other indebtedness. The subordinated notes mature in various amounts periodically through the year 2029. At December 31, 2020, all of the subordinated notes are redeemable by the holders prior to maturity at a discount equal to three TABLE 14.3 December 31 2020 2019 2018 Subordinated notes weighted average interest rate 3.23 % 3.33 % 3.08 % Junior subordinated debt The junior subordinated debt is comprised of the debt securities issued by FNB in relation to our three unconsolidated subsidiary trusts (collectively, the Trusts), which are unconsolidated VIEs and are included on the Consolidated Balance Sheets in long-term borrowings. One hundred percent of the common equity of each Trust is owned by FNB. The Trusts were formed for the purpose of issuing FNB-obligated mandatorily redeemable capital securities, or TPS to third-party investors. The proceeds from the sale of TPS and the issuance of common equity by the Trusts were invested in junior subordinated debt securities issued by FNB, which are the sole assets of each Trust. Since third-party investors are the primary beneficiaries, the Trusts are not consolidated in our Financial Statements. The Trusts pay dividends on the TPS at the same rate as the distributions paid by us on the junior subordinated debt held by the Trusts. F.N.B. Statutory Trust II was formed by us, and the other two statutory trusts were assumed through acquisitions. The acquired statutory trusts were adjusted to fair value in conjunction with the various acquisitions. We record the distributions on the junior subordinated debt issued to the Trusts as interest expense. The TPS are subject to mandatory redemption, in whole or in part, upon repayment of the junior subordinated debt. The TPS are eligible for redemption, at any time, at our discretion. Under capital guidelines, the junior subordinated debt, net of our investments in the Trusts, is included in tier 2 capital. We have entered into agreements which, when taken collectively, fully and unconditionally guarantee the obligations under the TPS subject to the terms of each of the guarantees. The following table provides information relating to the Trusts as of December 31, 2020: TABLE 14.4 (dollars in millions) Trust Common Junior Stated Interest Rate Reset Factor F.N.B. Statutory Trust II $ 22 $ 1 $ 22 6/15/2036 1.87 % LIBOR + 165 basis points (bps) Yadkin Valley Statutory Trust I 25 1 22 12/15/2037 1.54 % LIBOR + 132 bps FNB Financial Services Capital Trust I 25 1 22 9/30/2035 1.70 % LIBOR + 146 bps Total $ 72 $ 3 $ 66 During the first half of 2019, we redeemed $44.0 million of TPS that we previously assumed through various acquisitions. Other senior and subordinated debt During the first quarter of 2020, we completed a debt offering in which we issued $300 million aggregate principal amount of senior notes due in 2023. The net proceeds of the debt offering after deducting underwriting discounts and commissions and offering costs were $297.9 million. These proceeds were used for general corporate purposes, which included investments at the holding company level, capital to support the growth of FNBPA, repurchase of our common shares and refinancing of outstanding indebtedness. The following table provides information relating to our senior debt and other subordinated debt as of December 31, 2020. These debt issuances are fixed-rate, with the exception of the debt offering in 2019, which is fixed-to-floating rate after February 14, 2024, at which time the floating rate will be LIBOR plus 240 basis points, or an alternative rate that may replace LIBOR, as specified in the prospectus for this offering. The subordinated notes are eligible for treatment as tier 2 capital for regulatory capital purposes. TABLE 14.5 (dollars in millions) Aggregate Principal Amount Issued Net Proceeds (2) Carrying Value Stated Maturity Date Interest 2.20% Senior Notes due February 24, 2023 $ 300 $ 298 $ 299 2/24/2023 2.20 % 4.95% Fixed-To-Floating Rate Subordinated Notes due 2029 120 118 119 2/14/2029 4.95 % 4.875% Subordinated Notes due 2025 100 98 99 10/2/2025 4.875 % 7.625% Subordinated Notes due August 12, 2023 (1) 38 46 31 8/12/2023 7.625 % Total $ 558 $ 560 $ 548 (1) Assumed from YDKN and adjusted to fair value at the time of acquisition. (2) After deducting underwriting discounts and commissions and offering costs. For the debt assumed from YDKN, this is the fair value of the debt at the time of the acquisition. During the first half of 2019, we repurchased and retired $9.5 million and redeemed $15.5 million in higher interest rate other subordinated debt assumed in the 2017 YDKN acquisition.

Derivative Instruments and Hedg

Derivative Instruments and Hedging Activities	12 Months Ended
	Dec. 31, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments and Hedging Activities	DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES We are exposed to certain risks arising from both our business operations and economic conditions. We principally manage our exposures to a wide variety of business and operational risks through management of our core business activities. We manage economic risks, including interest rate risk, primarily by managing the amount, source, and duration of our assets and liabilities, and through the use of derivative instruments. Derivative instruments are used to reduce the effects that changes in interest rates may have on net income and cash flows. We also use derivative instruments to facilitate transactions on behalf of our customers. All derivatives are carried on the Consolidated Balance Sheets at fair value and do not take into account the effects of master netting arrangements we have with other financial institutions. Credit risk is included in the determination of the estimated fair value of derivatives. Derivative assets are reported in the Consolidated Balance Sheets in other assets and derivative liabilities are reported in other liabilities. Changes in fair value are recognized in earnings except for certain changes related to derivative instruments designated as part of a cash flow hedging relationship. The following table presents notional amounts and gross fair values of our derivative assets and derivative liabilities which are not offset in the Consolidated Balance Sheets: TABLE 15.1 December 31 2020 2019 Notional Fair Value Notional Fair Value (in millions) Asset Liability Asset Liability Gross Derivatives Subject to master netting arrangements: Interest rate contracts – designated $ 1,430 $ 3 $ — $ 1,655 $ 1 $ — Interest rate swaps – not designated 4,791 — 37 3,640 — 23 Total subject to master netting arrangements 6,221 3 37 5,295 1 23 Not subject to master netting arrangements: Interest rate swaps – not designated 4,791 349 — 3,640 149 1 Interest rate lock commitments – not designated 531 24 — 163 3 — Forward delivery commitments – not designated 500 — 2 195 1 1 Credit risk contracts – not designated 437 — 1 265 — — Total not subject to master netting arrangements 6,259 373 3 4,263 153 2 Total $ 12,480 $ 376 $ 40 $ 9,558 $ 154 $ 25 Certain derivative exchanges have enacted a rule change which in effect results in the legal characterization of variation margin payments for certain derivative contracts as settlement of the derivatives mark-to-market exposure and not collateral. Accordingly, we have changed our reporting of certain derivatives to record variation margin on trades cleared through these exchanges as settled. The daily settlement of the derivative exposure does not change or reset the contractual terms of the instrument. The fair value of interest rate swaps - not designated has increased from December 31, 2019 primarily due to the significantly lower interest rate environment since year-end. We adopted RRR on October 1, 2020, and the guidance will be followed until the Update terminates on December 31, 2022. As of October 16, 2020, we changed our valuation methodology to reflect changes made by central clearinghouses that changed the discounting methodology and interest calculation of cash migration from overnight index swap (OIS) to SOFR for U.S. dollar cleared interest rate swaps to better reflect prices obtainable in the markets in which we transact. Certain of these valuation methodology changes were applied to eligible hedging relationships. Accordingly, we have updated our hedge documentation to reflect the election of certain expedients and exceptions related to our cash flow hedging programs. The change in valuation methodology was applied prospectively as a change in accounting estimate and did not have a material impact on our consolidated financial position or results of operations. Derivatives Designated as Hedging Instruments under GAAP Interest Rate Contracts. We entered into interest rate derivative agreements to modify the interest rate characteristics of certain commercial loans and certain of our FHLB advances from variable rate to fixed rate in order to reduce the impact of changes in future cash flows due to market interest rate changes. These agreements are designated as cash flow hedges, hedging the exposure to variability in expected future cash flows. The derivative’s gain or loss, including any ineffectiveness, is initially reported as a component of OCI and subsequently reclassified into earnings in the same line item associated with the forecasted transaction when the forecasted transaction affects earnings. Prior to 2019, any ineffective portion of the gain or loss was reported in earnings immediately. The following table shows amounts reclassified from AOCI: TABLE 15.2 Amount of Gain (Loss) Recognized in OCI on Derivatives Location of Gain (Loss) Reclassified from AOCI into Income Amount of Gain (Loss) Reclassified from AOCI into Income Year Ended Year Ended (in millions) 2020 2019 2018 2020 2019 2018 Derivatives in cash flow hedging relationships: Interest rate contracts $ (51) $ (22) $ (3) Interest income (expense) $ (14) $ 2 $ 2 Other income (9) — — The following table represents gains (losses) recognized in the Consolidated Statements of Income on cash flow hedging relationships: TABLE 15.3 Year Ended December 31, 2020 2019 2018 (in millions) Interest Income - Loans and Leases Interest Expense - Short-Term Borrowings Interest Income - Loans and Leases Interest Expense - Short-Term Borrowings Interest Income - Loans and Leases Interest Expense - Short-Term Borrowings Total amounts of income and expense line items presented in the Consolidated Statements of Income (the effects of cash flow hedges are included in these line items) $ 990 $ 38 $ 1,085 $ 80 $ 1,022 $ 75 The effects of cash flow hedging: Gain (loss) on cash flow hedging Interest rate contracts: Amount of gain (loss) reclassified from AOCI into net income (1) (7) (16) (1) 3 (1) 3 Amount of gain (loss) reclassified — — — — — — (1) For 2020, the amount of loss reclassified from AOCI into net income relating to interest income on loans and leases included an $8.9 million loss reflected in other non-interest income. As of December 31, 2020, the maximum length of time over which forecasted interest cash flows are hedged is 3.9 years. In the twelve months that follow December 31, 2020, we expect to reclassify from the amount currently reported in AOCI net derivative losses of $18.8 million ($14.7 million net of tax), in association with interest on the hedged loans and FHLB advances. This amount could differ from amounts actually recognized due to changes in interest rates, hedge de-designations, and the addition of other hedges subsequent to December 31, 2020. During the third quarter of 2020, we voluntarily terminated $225.0 million of interest rate contracts associated with cash flow hedge programs to take advantage of strong deposit growth and reduce higher-cost debt. There were no components of derivative gains or losses excluded from the assessment of hedge effectiveness related to these cash flow hedges. Also, during the years ended December 31, 2020 and 2019, there were no gains or losses from cash flow hedge derivatives reclassified to earnings because it became probable that the original forecasted transactions would not occur. Derivatives Not Designated as Hedging Instruments under GAAP Interest Rate Swaps. We enter into interest rate swap agreements to meet the financing, interest rate and equity risk management needs of qualifying commercial loan customers. These agreements provide the customer the ability to convert from variable to fixed interest rates. The credit risk associated with derivatives executed with customers is essentially the same as that involved in extending loans and is subject to normal credit policies and monitoring. Swap derivative transactions with customers are not subject to enforceable master netting arrangements and are generally secured by rights to non-financial collateral, such as real and personal property. We enter into positions with a derivative counterparty in order to offset our exposure on the fixed components of the customer interest rate swap agreements. We seek to minimize counterparty credit risk by entering into transactions only with high-quality financial dealer institutions. Interest rate swap agreements with loan customers and with the offsetting counterparties are reported at fair value in other assets and other liabilities on the Consolidated Balance Sheets with any resulting gain or loss recorded in current period earnings as other income or other expense. Interest Rate Lock Commitments . IRLCs an agreement to extend credit to a mortgage loan borrower, or an agreement to purchase a loan from a third-party originator, whereby the interest rate on the loan is set prior to funding. We are bound to fund the loan at a specified rate, regardless of whether interest rates have changed between the commitment date and the loan funding date, subject to the loan approval process. The borrower is not obligated to perform under the commitment. As such, outstanding IRLCs subject us to interest rate risk and related price risk during the period from the commitment to the borrower through the loan funding date, or commitment expiration. The IRLCs generally range between 30 to 270 days. The IRLCs are reported at fair value in other assets and other liabilities on the Consolidated Balance Sheets with any resulting gain or loss recorded in current period earnings as mortgage banking operations non-interest income. Forward Delivery Commitments . Forward delivery commitments on mortgage-backed securities are used to manage the interest rate and price risk of our IRLCs and mortgage loan held for sale inventory by fixing the forward sale price that will be realized upon sale of the mortgage loans into the secondary market. Historical commitment-to-closing ratios are considered to estimate the quantity of mortgage loans that will fund within the terms of the IRLCs. The forward delivery contracts are reported at fair value in other assets and other liabilities on the Consolidated Balance Sheets with any resulting gain or loss recorded in current period earnings as mortgage banking operations non-interest income. Credit Risk Contracts. We purchase and sell credit protection under risk participation agreements to share with other counterparties some of the credit exposure related to interest rate derivative contracts or to take on credit exposure to generate revenue. We will make/receive payments under these agreements if a customer defaults on their obligation to perform under certain derivative swap contracts. Risk participation agreements sold with notional amounts totaling $294.4 million as of December 31, 2020 have remaining terms ranging from one month to twenty years. Under these agreements, our maximum exposure assuming a customer defaults on their obligation to perform under certain derivative swap contracts with third parties would be $0.6 million and $0.3 million at December 31, 2020 and 2019, respectively. The fair values of risk participation agreements purchased and sold were $0.2 million and $0.6 million, respectively, at December 31, 2020 and $0.1 million and $0.3 million, respectively, at December 31, 2019. The following table presents the effect of certain derivative financial instruments on the Consolidated Statements of Income: TABLE 15.4 Year Ended December 31, (in millions) Consolidated Statements of Income Location 2020 2019 2018 Interest rate swaps Non-interest income - other $ — $ — $ 1 Interest rate lock commitments Mortgage banking operations — — — Forward delivery contracts Mortgage banking operations (2) (1) 1 Credit risk contracts Non-interest income - other — — — Counterparty Credit Risk We are party to master netting arrangements with most of our swap derivative dealer counterparties. Collateral, usually marketable securities and/or cash, is exchanged between FNB and our counterparties, and is generally subject to thresholds and transfer minimums. For swap transactions that require central clearing, we post cash to our clearing agency. Collateral positions are settled or valued daily, and adjustments to amounts received and pledged by us are made as appropriate to maintain proper collateralization for these transactions. Certain master netting agreements contain provisions that, if violated, could cause the counterparties to request immediate settlement or demand full collateralization under the derivative instrument. If we had breached our agreements with our derivative counterparties we would be required to settle our obligations under the agreements at the termination value and would be required to pay an additional $0.3 million and $0.1 million as of December 31, 2020 and 2019, respectively, in excess of amounts previously posted as collateral with the respective counterparty. The following table presents a reconciliation of the net amounts of derivative assets and derivative liabilities presented in the Consolidated Balance Sheets to the net amounts that would result in the event of offset: TABLE 15.5 Amount Not Offset in the (in millions) Net Amount Financial Cash Net December 31, 2020 Derivative Assets Interest rate contracts: Designated $ 3 $ — $ 3 $ — Total $ 3 $ — $ 3 $ — Derivative Liabilities Interest rate contracts: Not designated $ 37 $ — $ 37 $ — Total $ 37 $ — $ 37 $ — December 31, 2019 Derivative Assets Interest rate contracts: Designated $ 1 $ 1 $ — $ — Total $ 1 $ 1 $ — $ — Derivative Liabilities Interest rate contracts: Not designated $ 23 $ 23 $ — $ — Total $ 23 $ 23 $ — $ —

Commitments, Credit Risk and Co

Commitments, Credit Risk and Contingencies	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments, Credit Risk and Contingencies	COMMITMENTS, CREDIT RISK AND CONTINGENCIES We have commitments to extend credit and standby letters of credit that involve certain elements of credit risk in excess of the amount stated in the Consolidated Balance Sheets. Our exposure to credit loss in the event of non-performance by the customer is represented by the contractual amount of those instruments. The credit risk associated with commitments to extend credit and standby letters of credit is essentially the same as that involved in extending loans and leases to customers and is subject to normal credit policies. Since many of these commitments expire without being drawn upon, the total commitment amounts do not necessarily represent future cash flow requirements. Following is a summary of off-balance sheet credit risk information: TABLE 16.1 December 31 2020 2019 (in millions) Commitments to extend credit $ 9,285 $ 8,089 Standby letters of credit 158 150 At December 31, 2020, funding of 75.2% of the commitments to extend credit was dependent on the financial condition of the customer. We have the ability to withdraw such commitments at our discretion. Commitments generally have fixed expiration dates or other termination clauses and may require payment of a fee. Based on management’s credit evaluation of the customer, collateral may be deemed necessary. Collateral requirements vary and may include accounts receivable, inventory, property, plant and equipment and income-producing commercial properties. Standby letters of credit are conditional commitments issued by us that may require payment at a future date. The credit risk involved in issuing letters of credit is actively monitored through review of the historical performance of our portfolios. Our AULC for commitments that are not unconditionally cancellable, which is included in other liabilities on the Consolidated Balance Sheets was $13.7 million at December 31, 2020. In addition to the above commitments, subordinated notes issued by FNB Financial Services, LP, a wholly-owned finance subsidiary, are fully and unconditionally guaranteed by FNB. These subordinated notes are included in the summaries of short-term borrowings and long-term borrowings in Notes 13 and 14. Other Legal Proceedings In the ordinary course of business, we may assert claims in legal proceedings against another party or parties, and we are routinely named as defendants in, or made parties to, pending and potential legal actions. Also, as regulated entities, we are subject to governmental and regulatory examinations, information-gathering requests, and may be subject to investigations and proceedings (both formal and informal). Such threatened claims, litigation, investigations, regulatory and administrative proceedings typically entail matters that are considered incidental to the normal conduct of business. Claims for significant monetary damages may be asserted in many of these types of legal actions, while claims for disgorgement, restitution, penalties and/or other remedial actions or sanctions may be sought in regulatory matters. In these instances, if we determine that we have meritorious defenses, we will engage in an aggressive defense. However, if management determines, in consultation with counsel, that settlement of a matter is in the best interest of FNB and our shareholders, we may do so. It is inherently difficult to predict the eventual outcomes of such matters given their complexity and the particular facts and circumstances at issue in each of these matters. However, on the basis of current knowledge and understanding, and advice of counsel, we do not believe that judgments, sanctions, settlements or orders, if any, that may arise from these matters (either individually or in the aggregate, after giving effect to applicable reserves and insurance coverage) will have a material adverse effect on our financial position or liquidity, although they could have a material effect on net income in a given period. In view of the inherent unpredictability of outcomes in litigation and governmental and regulatory matters, particularly where (i) the damages sought are indeterminate, (ii) the proceedings are in the early stages, or (iii) the matters involve novel legal theories or a large number of parties, as a matter of course, there is considerable uncertainty surrounding the timing or ultimate resolution of litigation and governmental and regulatory matters, including a possible eventual loss, fine, penalty, business or adverse reputational impact, if any, associated with each such matter. In accordance with applicable accounting guidance, we establish accruals for litigation and governmental and regulatory matters when those matters proceed to a stage where they present loss contingencies that are both probable and reasonably estimable. In such cases, there may be a possible exposure to loss in excess of any amounts accrued. We will continue to monitor such matters for developments that could affect the amount of the accrual, and will adjust the accrual amount as appropriate. If the loss contingency in question is not both probable and reasonably estimable, we do not establish an accrual and the matter will continue to be monitored for any developments that would make the loss contingency both probable and reasonably estimable. We believe that our accruals for legal proceedings are appropriate and, in the aggregate, are not material to our consolidated financial position, although future accruals could have a material effect on net income in a given period.

Stock Incentive Plans

Stock Incentive Plans	12 Months Ended
	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
Stock Incentive Plans	STOCK INCENTIVE PLANS Restricted Stock We issue restricted stock awards to key employees under our Incentive Compensation Plan (Plan). We issue time-based awards and performance-based awards under this Plan, both of which are based on a three The unvested restricted stock unit awards are eligible to receive cash dividends or dividend equivalents which are ultimately used to purchase additional shares of stock and are subject to forfeiture if the requisite service period is not completed or the specified performance criteria are not met. These awards are subject to certain accelerated vesting provisions upon retirement, death, disability or in the event of a change of control as defined in the award agreements. The following table summarizes the activity relating to restricted stock units during the periods indicated: TABLE 17.1 2020 2019 2018 Units Weighted Units Weighted Units Weighted Unvested units outstanding at beginning of year 2,858,357 $ 12.56 2,556,174 $ 13.51 1,975,862 $ 13.64 Granted 2,004,895 6.95 1,182,197 10.94 962,799 13.21 Net adjustment due to performance 47,290 13.00 — — — — Vested (613,581) 14.41 (655,208) 13.15 (258,031) 13.19 Forfeited/expired (203,058) 12.54 (332,814) 12.72 (214,743) 13.39 Dividend reinvestment 228,212 8.14 108,008 11.84 90,287 12.61 Unvested units outstanding at end of year 4,322,115 9.46 2,858,357 12.56 2,556,174 13.51 The following table provides certain information related to restricted stock units: TABLE 17.2 Year Ended December 31 2020 2019 2018 (in millions) Stock-based compensation expense $ 16 $ 12 $ 10 Tax benefit related to stock-based compensation expense 3 2 2 Fair value of units vested 5 7 3 As of December 31, 2020, there was $11.0 million of unrecognized compensation cost related to unvested restricted stock units including $0.6 million that is subject to accelerated vesting under the Plan’s immediate vesting upon retirement. Stock-based compensation expense increased $5.0 million, or 44%, compared to 2019 as we made a change to long-term stock-based compensation retirement vesting that resulted in accelerated grant date expense recognition for certain 2020 awards, with full expense recognition on grant date instead of recognizing the same expense amount over a 36-month vesting period. These awards are not released until the three three The components of the restricted stock units as of December 31, 2020 are as follows: TABLE 17.3 (dollars in millions) Service- Performance- Total Unvested restricted stock units 2,983,059 1,339,056 4,322,115 Unrecognized compensation expense $ 9 $ 2 $ 11 Intrinsic value $ 28 $ 13 $ 41 Weighted average remaining life (in years) 1.72 1.16 1.54 Stock Options All outstanding stock options were assumed from acquisitions and are fully vested. Upon consummation of our acquisitions, all outstanding stock options issued by the acquired companies were converted into equivalent FNB stock options. We issue shares of treasury stock or authorized but unissued shares to satisfy stock options exercised. The following table summarizes the activity relating to stock options during the periods indicated: TABLE 17.4 2020 Weighted 2019 Weighted 2018 Weighted Options outstanding at beginning of year 246,084 $ 8.14 458,354 $ 7.99 722,650 $ 7.96 Exercised (33,945) 5.74 (183,566) 7.86 (253,899) 7.77 Forfeited/expired (16,053) 7.38 (28,704) 7.65 (10,397) 11.98 Options outstanding and exercisable at end of year 196,086 8.61 246,084 8.14 458,354 7.99 The following table summarizes information about stock options outstanding at December 31, 2020: TABLE 17.5 Range of Exercise Prices Options Weighted Average Weighted Average $3.57 - $5.36 26,216 0.72 $ 4.93 $5.37 - $8.05 39,667 2.12 6.91 $8.06 - $11.37 130,203 3.80 9.87 196,086 The intrinsic value of outstanding and exercisable stock options at December 31, 2020 was $0.3 million . The aggregate intrinsic value represents the amount by which the fair value of underlying stock exceeds the option exercise price. Warrants As of December 31, 2020, there were no longer any outstanding warrants. The warrants that were previously issued have been exercised or expired in 2018 and 2019.

Retirement Plans

Retirement Plans	12 Months Ended
	Dec. 31, 2020
Retirement Benefits [Abstract]
Retirement Plans	RETIREMENT PLANS We sponsor the Retirement Income Plan (RIP), a qualified noncontributory defined benefit pension plan that has been frozen. The RIP covered employees who satisfied minimum age and length of service requirements. Although not required, during 2020, we made a $5.0 million contribution to the RIP. We also sponsor two supplemental non-qualified retirement plans that have been frozen. The ERISA Excess Retirement Plan provides retirement benefits equal to the difference, if any, between the maximum benefit allowable under the Internal Revenue Code and the amount that would be provided under the RIP, if no limits were applied. The Basic Retirement Plan (BRP) is applicable to certain officers whom the Board of Directors designates. Officers participating in the BRP receive a benefit based on a target benefit percentage based on years of service at retirement and a designated tier as determined by the Board of Directors. When a participant retires, the benefit under the BRP is a monthly benefit equal to the participant's aggregate target benefit percentage multiplied by the participant’s highest average monthly cash compensation, including bonuses, during five ten the monthly benefit the participant receives from the Social Security Administration, the RIP, the ERISA Excess Retirement Plan and the annuity equivalent of the automatic contributions paid to participants under the qualified 401(k) defined contribution plan and the ERISA Excess Lost Match Plan. The following tables provide information relating to the accumulated benefit obligation, change in benefit obligation, change in plan assets, the plans’ funded status and the amount included in the Consolidated Balance Sheets for the qualified and non-qualified plans described above (collectively, the Plans): TABLE 18.1 December 31 2020 2019 Qualified Non-Qualified Total Qualified Non-Qualified Total (in millions) Accumulated benefit obligation $ 167 $ 20 $ 187 $ 156 $ 19 $ 175 Projected benefit obligation at beginning of year $ 156 $ 19 $ 175 $ 145 $ 18 $ 163 Interest cost 5 1 6 6 1 7 Actuarial loss (gain) 15 2 17 15 2 17 Benefits paid (9) (2) (11) (10) (2) (12) Projected benefit obligation at end of year $ 167 $ 20 $ 187 $ 156 $ 19 $ 175 Fair value of plan assets at beginning of year $ 173 $ — $ 173 $ 150 $ — $ 150 Actual return on plan assets 20 — 20 28 — 28 Corporation contribution 5 2 7 5 2 7 Benefits paid (9) (2) (11) (10) (2) (12) Fair value of plan assets at end of year $ 189 $ — $ 189 $ 173 $ — $ 173 Funded status of plans $ 22 $ (20) $ 2 $ 17 $ (19) $ (2) The unrecognized actuarial loss, prior service cost and net transition obligation are required to be recognized into earnings over the average remaining participant life due to the freezing of the RIP, which may, on a net basis reduce future earnings. Actuarial assumptions used in the determination of the projected benefit obligation in the Plans are as follows: TABLE 18.2 Assumptions at December 31 2020 2019 Weighted average discount rate 2.31 % 3.17 % Rates of average increase in compensation levels 3.50 3.50 The discount rate assumption at December 31, 2020 and 2019 was determined using a yield-curve based approach. A yield curve was produced for a universe containing the majority of U.S.-issued Aa-graded corporate bonds, all of which were non-callable (or callable with make-whole provisions), and after excluding the 10% of the bonds with the highest and lowest yields. The discount rate was developed as the level equivalent rate that would produce the same present value as that using spot rates aligned with the projected benefit payments. The net periodic pension cost and OCI for the Plans included the following components: TABLE 18.3 Year Ended December 31 2020 2019 2018 (in millions) Interest cost $ 6 $ 7 $ 6 Expected return on plan assets (13) (11) (11) Actuarial loss amortization 3 2 2 Total pension income (4) (2) (3) Other changes in plan assets and benefit obligations recognized in other comprehensive income: Current year actuarial loss 10 1 6 Amortization of actuarial loss (3) (2) (2) Total amount recognized in other comprehensive income 7 (1) 4 Total amount recognized in net periodic benefit cost and other comprehensive income $ 3 $ (3) $ 1 The plans have an actuarial measurement date of December 31. Actuarial assumptions used in the determination of the net periodic pension cost in the Plans are as follows: TABLE 18.4 Assumptions for the Year Ended December 31 2020 2019 2018 Weighted average discount rate 3.17 % 4.16 % 4.19 % Rates of increase in compensation levels 3.50 3.50 3.50 Expected long-term rate of return on assets 7.25 7.25 7.25 The expected long-term rate of return on plan assets has been established by considering historical and anticipated expected returns on the asset classes invested in by the pension trust and the allocation strategy currently in place among those classes. The expected long-term rate of return on plan assets was reduced to 6.75% effective January 1, 2021. The change in plan assets reflects benefits paid from the qualified pension plans of $10.0 million and $10.0 million for 2020 and 2019, respectively. We made contributions to the RIP of $5.0 million, $5.0 million and $4.0 million during 2020, 2019 and 2018, respectively . For the non-qualified pension plans, the change in plan assets reflects benefits paid from and contributions made to the plans in the same amount. This amount represents the actual benefit payments paid from general assets of $1.5 million for 2020 and $1.5 million for 2019. The following table provides information regarding estimated future cash flows relating to the Plans at December 31, 2020: TABLE 18.5 (in millions) Expected employer contributions: 2021 $ 1 Expected benefit payments: 2021 10 2022 10 2023 11 2024 11 2025 11 2026 – 2030 52 The qualified pension plan contributions are deposited into a trust and the qualified benefit payments are made from trust assets. For the non-qualified plans, the contributions and the benefit payments are the same and reflect expected benefit amounts, which we pay from general assets. Our subsidiaries participate in a qualified 401(k) defined contribution plan under which employees may contribute a percentage of their salary. Employees are eligible to participate upon their first day of employment. Under this plan, we match 100% of the first 6% that the employee defers. During the second quarter of 2018, we made a one-time discretionary contribution of $0.9 million to the vast majority of our employees following the tax reform that was enacted in December 2017. Additionally, we may provide a performance-based company contribution of up to 3% if we exceed annual financial goals. Our contribution expense is presented in the following table: TABLE 18.6 Year Ended December 31 2020 2019 2018 (in millions) 401(k) contribution expense $ 17 $ 15 $ 15 We also sponsor an ERISA Excess Lost Match Plan for certain officers. This plan provides retirement benefits equal to the difference, if any, between the maximum benefit allowable under the Internal Revenue Code and the amount that would have been provided under the qualified 401(k) defined contribution plan, if no limits were applied. Pension Plan Investment Policy and Strategy Our investment strategy for the RIP is to diversify plan assets between a wide mix of securities within the equity and debt markets to allow the account the opportunity to meet the expected long-term rate of return requirements while minimizing short-term volatility. In this regard, the plan has targeted allocations within the equity securities category for domestic large cap, domestic mid cap, domestic small cap, real estate investment trusts, emerging market and international securities. Within the debt securities category, the plan has targeted allocation levels for U.S. Treasury, U.S. agency, domestic investment-grade bonds, high-yield bonds, inflation-protected securities and international bonds. The following table presents asset allocations for our pension plans as of December 31, 2020 and 2019, and the target allocation for 2021, by asset category: TABLE 18.7 Target Percentage of Plan Assets December 31 2021 2020 2019 Asset Category Equity securities 45 - 65 63 % 60 % Debt securities 30 - 50 36 37 Cash equivalents 0 - 10 1 3 At December 31, 2020 and 2019, equity securities included 450,000 and 469,000 shares, respectively, of our common stock, representing 2.1% and 3.5% of total plan assets at December 31, 2020 and 2019, respectively. Dividends received on our common stock held by the Plan were $0.2 million for both 2020 and 2019. The fair values of our pension plan assets by asset category are as follows: TABLE 18.8 (in millions) Level 1 Level 2 Level 3 Total December 31, 2020 Asset Class Cash $ 2 $ — $ — $ 2 Equity securities: F.N.B. Corporation 4 — — 4 Other large-cap U.S. financial services companies 3 — — 3 Other large-cap U.S. companies 60 — — 60 Other equity 1 — — 1 Mutual fund equity investments: U.S. equity index funds: U.S. large-cap equity index funds — — — — U.S. small-cap equity index funds 5 — — 5 U.S. mid-cap equity index funds 6 — — 6 Non-U.S. equities growth fund 16 — — 16 U.S. equity funds: U.S. mid-cap 13 — — 13 U.S. small-cap 5 — — 5 Other 5 — — 5 Fixed income securities: U.S. government agencies — 45 — 45 Corporate bonds — — — — Fixed income mutual funds: U.S. investment-grade fixed income securities 24 — — 24 Total $ 144 $ 45 $ — $ 189 (in millions) Level 1 Level 2 Level 3 Total December 31, 2019 Asset Class Cash $ 5 $ — $ — $ 5 Equity securities: F.N.B. Corporation 6 — — 6 Other large-cap U.S. financial services companies 4 — — 4 Other large-cap U.S. companies 54 — — 54 Other equity 1 — — 1 Mutual fund equity investments: U.S. equity index funds: U.S. large-cap equity index funds 1 — — 1 U.S. small-cap equity index funds 3 — — 3 U.S. mid-cap equity index funds 5 — — 5 Non-U.S. equities growth fund 9 — — 9 U.S. equity funds: U.S. mid-cap 12 — — 12 U.S. small-cap 4 — — 4 Other 5 — — 5 Fixed income securities: U.S. government agencies — 51 — 51 Corporate bonds — 1 — 1 Fixed income mutual funds: U.S. investment-grade fixed income securities 12 — — 12 Total $ 121 $ 52 $ — $ 173 The classifications for Level 1, Level 2 and Level 3 are discussed in Note 25, “Fair Value Measurements.”

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	INCOME TAXES Income Tax Expense Federal and state income tax expense consist of the following: TABLE 19.1 Year Ended December 31 2020 2019 2018 (in millions) Current income taxes: Federal taxes $ 71 $ 47 $ 41 State taxes 5 4 6 Total current income taxes 76 51 47 Deferred income taxes: Federal taxes (20) 30 32 State taxes 1 3 — Total deferred income taxes (19) 33 32 Total income taxes $ 57 $ 84 $ 79 The following table provides a reconciliation between the statutory tax rate and the actual effective tax rate: TABLE 19.2 Year Ended December 31 2020 2019 2018 Statutory federal tax rate 21.0 % 21.0 % 21.0 % State taxes, net of federal benefit 1.6 1.1 1.1 Tax-exempt interest (2.8) (2.2) (2.1) Cash surrender value on BOLI (0.8) (0.5) (0.5) Tax credits (6.3) (4.2) (2.8) Affordable housing cost amortization, net of tax benefits 2.5 1.4 0.7 Tax Cuts and Jobs Act revaluation of net deferred tax assets — — (0.4) Other items 1.5 1.1 0.6 Effective tax rate 16.7 % 17.7 % 17.6 % The effective tax rates in 2020, 2019 and 2018, respectively, were lower than the 21% statutory federal tax rate primarily due to the tax benefits resulting from renewable energy investment and historic tax credits, tax-exempt income on investments and loans and income from BOLI. For the years ended December 31, 2020, 2019 and 2018, we recognized net investment tax credits of $8.3 million, $7.9 million and $6.5 million, respectively, using the flow-through method of accounting for income tax credits. Deferred Income Taxes Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and tax purposes. DTAs and DTLs are measured based on the enacted tax rates that will apply in the years in which the temporary differences are expected to be recovered or paid. The following table presents the tax effects of significant temporary differences that give rise to federal and state DTAs and DTLs: TABLE 19.3 December 31 2020 2019 (in millions) Deferred tax assets: Allowance for credit losses $ 80 $ 43 Discounts on loans acquired in a business combination 16 41 Net operating loss/tax credit carryforwards 38 38 Deferred compensation 12 11 Securities impairments 1 1 Pension and other defined benefit plans 2 3 Lease liability 30 29 Net unrealized securities losses — 2 Other 14 8 Total 193 176 Valuation allowance (33) (28) Total deferred tax assets 160 148 Deferred tax liabilities: Loan costs (6) (15) Depreciation (12) (19) Prepaid expenses (1) (1) Amortizable intangibles (13) (15) Lease financing (32) (35) Mortgage servicing rights (8) (9) Lease ROU asset (28) (27) Net unrealized securities gains (7) — Other (2) (2) Total deferred tax liabilities (109) (123) Net deferred tax assets $ 51 $ 25 We establish a valuation allowance when it is more likely than not that we will not be able to realize the benefit of the DTAs or when future deductibility is uncertain. Periodically, the valuation allowance is reviewed and adjusted based on management’s assessment of realizable DTAs. As of December 31, 2020, the valuation allowance of $32.6 million primarily includes unused federal and state net operating loss carryforwards expiring from 2021 to 2040 and $3.3 million of state tax credit carryforwards. We anticipate that neither the state net operating loss and state tax credit carryforwards nor the other net DTAs at certain of our subsidiaries will be utilized and, as such, have recorded a valuation allowance against the DTAs related to these items. As of December 31, 2020, we had approximately $22.0 million of federal net operating loss and built-in loss carryforwards and $3.5 million of state tax credit carryforwards, net of valuation allowances. The utilization of these tax attributes is subject to annual limitations under Section 382 of the Internal Revenue Code, or a similar state-level statute, which will cause the utilization of these attributes to be deferred over a number of years, not to exceed beyond 2036. We have determined that we will likely have sufficient taxable income in the years during which these tax attributes are available to be utilized and, consequently, have determined that no additional valuation allowance against the recorded DTA is warranted. Uncertain Tax Positions We account for uncertainties in income taxes in accordance with ASC 740, Income Taxes . At December 31, 2020 and 2019, we have approximately $2.0 million and $1.6 million, respectively, of unrecognized tax benefits related to uncertain tax positions. As of December 31, 2020, $1.8 million of these tax benefits would affect the effective tax rate if recognized. We recognize potential accrued interest and penalties related to unrecognized tax benefits in income tax expense. To the extent interest is not assessed with respect to uncertain tax positions, amounts accrued will be reduced and reflected as a reduction of the overall income tax provision. We file numerous income tax returns in the U.S. federal jurisdiction and in several state jurisdictions. We are no longer subject to U.S. federal income tax examinations for years prior to 2017. With limited exception, we are no longer subject to state income tax examinations for years prior to 2017. We anticipate that a reduction in the unrecognized tax benefit of up to $0.07 million may occur in the next twelve months from the expiration of statutes of limitations which would result in a reduction in income taxes.

Other Comprehensive Income

Other Comprehensive Income	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
Other Comprehensive Income	OTHER COMPREHENSIVE INCOME The following table presents changes in AOCI, net of tax, by component: TABLE 20.1 (in millions) Unrealized Unrealized Net Unrecognized Total Year Ended December 31, 2020 Balance at beginning of period $ 11 $ (18) $ (58) $ (65) Other comprehensive (loss) income before reclassifications 54 (40) (6) 8 Amounts reclassified from AOCI — 18 — 18 Net current period other comprehensive (loss) income 54 (22) (6) 26 Balance at end of period $ 65 $ (40) $ (64) $ (39) The amounts reclassified from AOCI related to debt securities AFS are included in net securities gains on the Consolidated Statements of Income, while the amounts reclassified from AOCI related to derivative instruments in cash flow hedge programs are generally included in interest income on loans and leases on the Consolidated Statements of Income. However, due to the voluntary termination of a few cash flow hedges in 2020, a portion of the amount reclassified from AOCI is included in non-interest income on the Consolidated Statements of Income. The tax (benefit) expense amounts reclassified from AOCI in connection with the debt securities AFS and derivative instruments reclassifications are included in income taxes on the Consolidated Statements of Income.

Earnings per Common Share

Earnings per Common Share	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Earnings per Common Share	EARNINGS PER COMMON SHARE The following table sets forth the computation of basic and diluted earnings per common share: TABLE 21.1 Year Ended December 31 2020 2019 2018 (dollars in millions, except per share data) Net income $ 286 $ 387 $ 373 Less: Preferred stock dividends 8 8 8 Net income available to common stockholders $ 278 $ 379 $ 365 Basic weighted average common shares outstanding 323,368,639 324,938,720 324,207,198 Net effect of dilutive stock options, warrants and restricted stock 2,119,325 1,122,418 1,416,405 Diluted weighted average common shares outstanding 325,487,964 326,061,138 325,623,603 Earnings per common share: Basic $ 0.86 $ 1.17 $ 1.13 Diluted $ 0.85 $ 1.16 $ 1.12 The following table shows the average shares excluded from the above calculation as their effect would have been anti-dilutive: TABLE 21.2 Year Ended December 31 2020 2019 2018 Average shares excluded from the diluted earnings per common share calculation 22,375 — 81

Regulatory Matters

Regulatory Matters	12 Months Ended
	Dec. 31, 2020
Banking and Thrift, Other Disclosures [Abstract]
Regulatory Matters	REGULATORY MATTERS FNB and FNBPA are subject to various regulatory capital requirements administered by the federal banking agencies. Quantitative measures established by regulators to ensure capital adequacy require FNB and FNBPA to maintain minimum amounts and ratios of total, tier 1 and CET1 capital (as defined in the regulations) to risk-weighted assets (as defined) and of leverage ratio (as defined). Failure to meet minimum capital requirements could lead to initiation of certain mandatory, and possibly additional discretionary actions by regulators that, if undertaken, could have a direct material effect on our Consolidated Financial Statements, dividends and future business and corporate strategies. Under capital adequacy guidelines and the regulatory framework for prompt corrective action, FNB and FNBPA must meet specific capital guidelines that involve quantitative measures of assets, liabilities and certain off-balance sheet items as calculated under regulatory accounting practices. FNB’s and FNBPA’s capital amounts and classifications are also subject to qualitative judgments by the regulators about components, risk weightings and other factors. As of December 31, 2020, the most recent notification from the federal banking agencies categorized FNB and FNBPA as “well-capitalized” under the respective regulatory frameworks. There are no conditions or events since the notification which management believes have changed this categorization. Following are the capital ratios for FNB and FNBPA: TABLE 22.1 Actual Well-Capitalized Requirements (1) Minimum Capital (dollars in millions) Amount Ratio Amount Ratio Amount Ratio As of December 31, 2020 F.N.B. Corporation: Total capital $ 3,324 12.33 % $ 2,695 10.00 % $ 2,830 10.50 % Tier 1 capital 2,759 10.24 1,617 6.00 2,291 8.50 Common equity tier 1 2,652 9.84 n/a n/a 1,886 7.00 Leverage 2,759 7.83 n/a n/a 1,410 4.00 Risk-weighted assets 26,948 FNBPA: Total capital 3,400 12.64 2,690 10.00 2,825 10.50 Tier 1 capital 2,882 10.71 2,152 8.00 2,287 8.50 Common equity tier 1 2,802 10.42 1,749 6.50 1,883 7.00 Leverage 2,882 8.19 1,760 5.00 1,408 4.00 Risk-weighted assets 26,902 As of December 31, 2019 F.N.B. Corporation: Total capital $ 3,174 11.81 % $ 2,687 10.00 % $ 2,821 10.50 % Tier 1 capital 2,632 9.79 1,612 6.00 2,284 8.50 Common equity tier 1 2,525 9.40 n/a n/a 1,881 7.00 Leverage 2,632 8.20 n/a n/a 1,283 4.00 Risk-weighted assets 26,866 FNBPA: Total capital 3,039 11.34 2,681 10.00 2,815 10.50 Tier 1 capital 2,841 10.60 2,144 8.00 2,279 8.50 Common equity tier 1 2,761 10.30 1,742 6.50 1,876 7.00 Leverage 2,841 8.87 1,601 5.00 1,281 4.00 Risk-weighted assets 26,806 (1) Reflects the well-capitalized standard under Regulation Y for F.N.B. Corporation and the prompt corrective action framework for FNBPA. Due to usable vault cash, FNBPA was not required to maintain aggregate cash reserves with the FRB at December 31, 2020. Although, we do maintain deposits for various services such as check clearing. Certain limitations exist under applicable law and regulations by regulatory agencies regarding dividend distributions to a parent by our subsidiaries. As of December 31, 2020, our subsidiaries had $477.6 million of retained earnings available for distribution to us without prior regulatory approval. Under current FRB regulations, FNBPA is limited in the amount it may lend to non-bank affiliates, including FNB. Such loans must be secured by specified collateral. In addition, any such loans to a non-bank affiliate may not exceed 10% of FNBPA’s capital and surplus and the aggregate of loans to all such affiliates may not exceed 20% of FNBPA’s capital and surplus. The maximum amount that may be borrowed by FNB affiliates under these provisions was $677.4 million at December 31, 2020.

Cash Flow Information

Cash Flow Information	12 Months Ended
	Dec. 31, 2020
Supplemental Cash Flow Elements [Abstract]
Cash Flow Information	CASH FLOW INFORMATION Following is a summary of supplemental cash flow information: TABLE 23.1 Year Ended December 31 2020 2019 2018 (in millions) Interest paid on deposits and other borrowings $ 216 $ 329 $ 230 Income taxes paid 57 40 19 Transfers of loans to other real estate owned 3 15 12 Loans transferred to held for sale from portfolio 537 389 — Loans transferred to portfolio from held for sale — 110 —

Business Segments

Business Segments	12 Months Ended
	Dec. 31, 2020
Segment Reporting [Abstract]
Business Segments	BUSINESS SEGMENTS We operate in three reportable segments: Community Banking, Wealth Management and Insurance. • The Community Banking segment provides commercial and consumer banking services. Commercial banking solutions include corporate banking, small business banking, investment real estate financing, business credit, capital markets and lease financing. Consumer banking products and services include deposit products, mortgage lending, consumer lending and a complete suite of mobile and online banking services. • The Wealth Management segment provides a broad range of personal and corporate fiduciary services including the administration of decedent and trust estates. In addition, it offers various alternative products, including securities brokerage and investment advisory services, mutual funds and annuities. • The Insurance segment includes a full-service insurance brokerage service offering all lines of commercial and personal insurance through major carriers. The Insurance segment also includes a reinsurer. We also previously operated a Consumer Finance segment, which is no longer a reportable segment. This segment primarily made installment loans to individuals and purchased installment sales finance contracts from retail merchants. On August 31, 2018, as part of our strategy to enhance the overall positioning of our consumer banking operations, we sold 100 percent of the issued and outstanding capital stock of Regency to Mariner Finance, LLC. This transaction was completed to accomplish several strategic objectives, including enhancing the credit risk profile of the consumer loan portfolio, offering additional liquidity and selling a non-strategic business segment that no longer fits with our core business. Regency's financial information is included in the Consumer Finance segment in the 2018 table that follows. The following tables provide financial information for these segments of FNB. The information provided under the caption “Parent and Other” represents operations not considered to be reportable segments and/or general operating expenses of FNB, and includes the parent company, other non-bank subsidiaries and eliminations and adjustments to reconcile to the Consolidated Financial Statements. TABLE 24.1 (in millions) Community Wealth Insurance Parent Consolidated At or for the Year Ended December 31, 2020 Interest income $ 1,129 $ — $ — $ 1 $ 1,130 Interest expense 188 — — 20 208 Net interest income 941 — — (19) 922 Provision for credit losses 123 — — — 123 Non-interest income 233 49 22 (10) 294 Non-interest expense (1) 675 35 19 8 737 Amortization of intangibles 12 — 1 — 13 Income tax expense (benefit) 61 3 — (7) 57 Net income (loss) 303 11 2 (30) 286 Total assets 37,245 38 35 36 37,354 Total intangibles 2,279 9 28 — 2,316 At or for the Year Ended December 31, 2019 Interest income $ 1,245 $ — $ — $ 2 $ 1,247 Interest expense 310 — — 20 330 Net interest income 935 — — (18) 917 Provision for credit losses 44 — — — 44 Non-interest income 237 46 20 (9) 294 Non-interest expense (1) 621 34 17 10 682 Amortization of intangibles 13 — 1 — 14 Income tax expense (benefit) 88 3 — (7) 84 Net income (loss) 406 9 2 (30) 387 Total assets 34,491 32 35 57 34,615 Total intangibles 2,291 10 28 — 2,329 (in millions) Community Wealth Insurance Consumer Parent Consolidated At or for the Year Ended December 31, 2018 Interest income $ 1,145 $ — $ — $ 25 $ — $ 1,170 Interest expense 219 — — 2 17 238 Net interest income 926 — — 23 (17) 932 Provision for credit losses 54 — — 6 1 61 Non-interest income 213 44 16 2 1 276 Non-interest expense (1) 609 33 17 15 5 679 Amortization of intangibles 15 1 — — — 16 Income tax expense (benefit) 82 2 — 1 (6) 79 Net income (loss) 379 8 (1) 3 (16) 373 Total assets 32,997 26 25 — 54 33,102 Total intangibles 2,304 10 20 — — 2,334 (1) Excludes amortization of intangibles, which is presented separately .

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	FAIR VALUE MEASUREMENTS We use fair value measurements to record fair value adjustments to certain financial assets and liabilities and to determine fair value disclosures. Securities AFS, mortgage loans held for sale accounted for under FVO and derivatives are recorded at fair value on a recurring basis. Additionally, from time to time, we may be required to record at fair value other assets on a non-recurring basis, such as certain impaired loans, OREO and certain other assets. Fair value is defined as an exit price, representing the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. Fair value measurements are not adjusted for transaction costs. Fair value is a market-based measure considered from the perspective of a market participant who holds the asset or owes the liability rather than an entity-specific measure. In determining fair value, we use various valuation approaches, including market, income and cost approaches. We follow an established hierarchy for inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that observable inputs be used when available. Observable inputs are inputs that market participants would use in pricing the asset or liability, which are developed based on market data obtained from independent sources. Unobservable inputs reflect our assumptions about the assumptions that market participants would use in pricing an asset or liability, which are developed based on the best information available in the circumstances. The fair value hierarchy gives the highest priority to unadjusted quoted market prices in active markets for identical assets or liabilities (Level 1 measurement) and the lowest priority to unobservable inputs (Level 3 measurement). The fair value hierarchy is broken down into three levels based on the reliability of inputs as follows: TABLE 25.1 Measurement Definition Level 1 Valuation is based upon unadjusted quoted market prices for identical instruments traded in active markets. Level 2 Valuation is based upon quoted market prices for similar instruments traded in active markets, quoted market prices for identical or similar instruments traded in markets that are not active and model-based valuation techniques for which all significant assumptions are observable in the market or can be corroborated by market data. Level 3 Valuation is derived from other valuation methodologies including discounted cash flow models and similar techniques that use significant assumptions not observable in the market. These unobservable assumptions reflect estimates of assumptions that market participants would use in determining fair value. A financial instrument’s level within the fair value hierarchy is based on the lowest level of input that is significant to the fair value measurement. Following is a description of the valuation methodologies we use for financial instruments recorded at fair value on either a recurring or non-recurring basis: Securities Available For Sale These securities are recorded at fair value on a recurring basis. At December 31, 2020, 100.0% of AFS securities used valuation methodologies involving market-based or market-derived information, collectively Level 1 and Level 2 measurements, to measure fair value. We closely monitor market conditions involving assets that have become less actively traded. If the fair value measurement is based upon recent observable market activity of such assets or comparable assets (other than forced or distressed transactions) that occur in sufficient volume, and do not require significant adjustment using unobservable inputs, those assets are classified as Level 1 or Level 2; if not, they are classified as Level 3. Making this assessment requires significant judgment. We use prices from independent pricing services and, to a lesser extent, indicative (non-binding) quotes from independent brokers, to measure the fair value of AFS securities. We validate prices received from pricing services or brokers using a variety of methods, including, but not limited to, comparison to secondary pricing services, corroboration of pricing by reference to other independent market data such as secondary broker quotes and relevant benchmark indices, and review of pricing information by corporate personnel familiar with market liquidity and other market-related conditions. Derivative Financial Instruments We determine fair value for derivatives using widely accepted valuation techniques including discounted cash flow analysis on the expected cash flows of each derivative. This analysis reflects contractual terms of the derivative, including the period to maturity and uses observable market based inputs, including interest rate curves and implied volatilities. We incorporate credit valuation adjustments to appropriately reflect both our own non-performance risk and the respective counterparty’s non-performance risk in the fair value measurements. In adjusting the fair value of our derivative contracts for the effect of non-performance risk, we consider the impact of netting and any applicable credit enhancements, such as collateral postings, thresholds, mutual puts and guarantees. Although we have determined that the majority of the inputs used to value our derivatives fall within Level 2 of the fair value hierarchy, the credit valuation adjustments associated with our derivatives and IRLCs utilize Level 3 inputs. Credit valuation estimates of current credit spreads are used to evaluate the likelihood of our default and the default of our counterparties. However, as of December 31, 2020 and 2019, we have assessed the significance of the impact of the credit valuation adjustments on the overall valuation of our non-IRLC derivative positions and have determined that the credit valuation adjustments are not significant to the overall valuation of our derivatives. As a result, we have determined that our derivative valuations in their entirety are classified in Level 2 of the fair value hierarchy. The fair value of IRLCs is based upon the estimated fair value of the underlying mortgage loan, including the expected cash flows related to MSRs and the estimated percentage of IRLCs that will result in a closed mortgage loan, and is classified as Level 3. Loans Held For Sale Residential mortgage loans held for sale are carried at fair value under the FVO. Fair value for residential mortgage loans held for sale, when recorded, is based on independent quoted market prices and is classified as Level 2. SBA loans held for sale are carried under lower of cost or fair value, for which, periodically, it may be necessary to record non-recurring fair value adjustments. Fair value for SBA loans held for sale, when recorded, is based on independent quoted market prices and is classified as Level 2. Collateral Dependent Loans For commercial loans in default which are greater than or equal to $1.0 million, individual reserves are determined based on an analysis of the present value of the loan's expected future cash flows, the loan's observable market value, or the fair value of the collateral less costs to sell. For commercial and consumer loans in default which are below $1.0 million, an established LGD percentage is multiplied by the loan balance and the results are aggregated for purposes of measuring specific reserve. Collateral may be real estate and/or business assets including equipment, inventory and accounts receivable. We determine the fair value of real estate based on appraisals by licensed or certified appraisers. The value of business assets is generally based on amounts reported on the business’ financial statements. Management must rely on the financial statements prepared and certified by the borrower or their accountants in determining the value of these business assets on an ongoing basis, which may be subject to significant change over time. Based on the quality of information or statements provided, management may require the use of business asset appraisals and site-inspections to better value these assets. We may discount appraised and reported values based on management’s historical knowledge, changes in market conditions from the time of valuation or management’s knowledge of the borrower and the borrower’s business. Since not all valuation inputs are observable, we classify these non-recurring fair value determinations as Level 2 or Level 3 based on the lowest level of input that is significant to the fair value measurement. We review and evaluate these loans no less frequently than quarterly for additional write-down based on the same factors identified above. Other Real Estate Owned OREO is comprised principally of commercial and residential real estate properties obtained in partial or total satisfaction of loan obligations. OREO acquired in settlement of indebtedness is recorded at fair value less costs to sell. Subsequently, these assets are carried at the lower of carrying value or fair value less costs to sell. Accordingly, it may be necessary to record non-recurring fair value adjustments. Fair value is generally based upon appraisals by licensed or certified appraisers and other market information and is classified as Level 3. Other Assets - MSRs and SBA Servicing Assets We carry MSRs at the lower of cost or fair value, and therefore, they are subject to fair value measurements on a non-recurring basis. Since sales of MSRs tend to occur in private transactions and the precise terms and conditions of the sales are typically not readily available, there is a limited market to refer to in determining the fair value of MSRs. As such we rely primarily on a discounted cash flow model, incorporating assumptions about loan prepayment rates, discount rates, servicing costs and other economic factors, to estimate the fair value of our MSRs. We utilize a third-party vendor to perform the modeling to estimate the fair value of our MSRs. Since the valuation model uses significant unobservable inputs, we classify MSRs within Level 3. We retain the servicing rights on SBA-guaranteed loans sold to investors. The standard sale structure under the SBA Secondary Participation Guaranty Agreement provides for us to retain a portion of the cash flow from the interest payment received on the SBA guaranteed portion of the loan, which is commonly known as a servicing spread. We utilize a third-party vendor to perform the modeling to estimate the fair value of our SBA servicing asset. Since the valuation model uses significant unobservable inputs, we classify SBA servicing assets within Level 3. The following table presents the balances of assets and liabilities measured at fair value on a recurring basis: TABLE 25.2 (in millions) Level 1 Level 2 Level 3 Total December 31, 2020 Assets Measured at Fair Value Debt securities available for sale U.S. Treasury $ 600 $ — $ — $ 600 U.S. government agencies — 172 — 172 U.S. government-sponsored entities — 161 — 161 Residential mortgage-backed securities Agency mortgage-backed securities — 994 — 994 Agency collateralized mortgage obligations — 1,124 — 1,124 Commercial mortgage-backed securities — 378 — 378 States of the U.S. and political subdivisions (municipals) — 32 — 32 Other debt securities — 2 — 2 Total debt securities available for sale 600 2,863 — 3,463 Loans held for sale — 144 — 144 Derivative financial instruments Trading — 349 — 349 Not for trading — 3 24 27 Total derivative financial instruments — 352 24 376 Total assets measured at fair value on a recurring basis $ 600 $ 3,359 $ 24 $ 3,983 Liabilities Measured at Fair Value Derivative financial instruments Trading $ — $ 37 $ — $ 37 Not for trading — 3 — 3 Total derivative financial instruments — 40 — 40 Total liabilities measured at fair value on a recurring basis $ — $ 40 $ — $ 40 (in millions) Level 1 Level 2 Level 3 Total December 31, 2019 Assets Measured at Fair Value Debt securities available for sale U.S. government agencies $ — $ 151 $ — $ 151 U.S. government-sponsored entities — 226 — 226 Residential mortgage-backed securities Agency mortgage-backed securities — 1,314 — 1,314 Agency collateralized mortgage obligations — 1,240 — 1,240 Commercial mortgage-backed securities — 345 — 345 States of the U.S. and political subdivisions (municipals) — 11 — 11 Other debt securities — 2 — 2 Total debt securities available for sale — 3,289 — 3,289 Loans held for sale — 41 — 41 Derivative financial instruments Trading — 149 — 149 Not for trading — 2 3 5 Total derivative financial instruments — 151 3 154 Total assets measured at fair value on a recurring basis $ — $ 3,481 $ 3 $ 3,484 Liabilities Measured at Fair Value Derivative financial instruments Trading $ — $ 24 $ — $ 24 Not for trading — 1 — 1 Total derivative financial instruments — 25 — 25 Total liabilities measured at fair value on a recurring basis $ — $ 25 $ — $ 25 The following table presents additional information about assets measured at fair value on a recurring basis and for which we have utilized Level 3 inputs to determine fair value: TABLE 25.3 (in millions) Interest Total Year Ended December 31, 2020 Balance at beginning of period $ 3 $ 3 Purchases, issuances, sales and settlements: Issuances 24 24 Settlements (3) (3) Balance at end of period $ 24 $ 24 Year Ended December 31, 2019 Balance at beginning of period $ 1 $ 1 Purchases, issuances, sales and settlements: Issuances 3 3 Settlements (1) (1) Balance at end of period $ 3 $ 3 We review fair value hierarchy classifications on a quarterly basis. Changes in the observability of the valuation attributes may result in reclassification of certain financial assets or liabilities. Such reclassifications are reported as transfers in/out of Level 3 at fair value at the beginning of the period in which the changes occur. See the “Securities Available for Sale” discussion within this footnote for information relating to determining Level 3 fair values. There were no transfers of assets or liabilities between the hierarchy levels during 2020 or 2019. From time to time, we measure certain assets at fair value on a non-recurring basis. These adjustments to fair value usually result from the application of the lower of cost or fair value accounting or write-downs of individual assets. Valuation methodologies used to measure these fair value adjustments were previously described. For assets measured at fair value on a non-recurring basis still held at the Balance Sheet date, the following table provides the hierarchy level and the fair value of the related assets or portfolios: TABLE 25.4 (in millions) Level 1 Level 2 Level 3 Total December 31, 2020 Collateral dependent loans $ — $ — $ 45 $ 45 Other real estate owned — — 3 3 Other assets - SBA servicing asset — — 3 3 Other assets - MSRs — — 36 36 December 31, 2019 Impaired loans $ — $ — $ 5 $ 5 Other real estate owned — — 4 4 Other assets - SBA servicing asset — — 3 3 Other assets - MSRs — — 30 30 The fair value amounts for collateral dependent loans and OREO in the table above were estimated at a date during the twelve months ended December 31, 2020 and 2019. Consequently, the fair value information presented is not necessarily as of the period’s end. MSRs measured at fair value on a non-recurring basis of $42.9 million had a valuation allowance of $7.3 million, bringing the December 31, 2020 carrying value to $35.6 million. The valuation allowance includes a provision expense included in 2020 earnings of $5.8 million. SBA servicing assets measured at fair value on a non-recurring basis of $4.0 million had a valuation allowance of $1.1 million, bringing the December 31, 2020 carrying value to $2.9 million. The valuation allowance includes provision income included in 2020 earnings of $0.1 million. Collateral dependent loans measured or re-measured at fair value on a non-recurring basis during 2020 had a carrying amount of $44.9 million which includes an allocated ACL of $13.2 million. The ACL includes a provision applicable to the current period fair value measurements of $36.0 million, which was included in provision for credit losses for 2020. OREO measured at fair value on a non-recurring basis during 2020 had a carrying amount of $4.4 million and was written down to $2.8 million, resulting in a loss of $1.6 million, which was included in earnings for 2020. Fair Value of Financial Instruments The following methods and assumptions were used to estimate the fair value of each financial instrument: Cash and Cash Equivalents, Accrued Interest Receivable and Accrued Interest Payable. For these short-term instruments, the carrying amount is a reasonable estimate of fair value. Securities. For both securities AFS and securities HTM, fair value equals the quoted market price from an active market, if available, and is classified within Level 1. If a quoted market price is not available, fair value is estimated using quoted market prices for similar securities or pricing models, and is classified as Level 2. Where there is limited market activity or significant valuation inputs are unobservable, securities are classified within Level 3. Under current market conditions, assumptions used to determine the fair value of Level 3 securities have greater subjectivity due to the lack of observable market transactions. Loans and Leases. The fair value of fixed rate loans and leases is estimated by discounting the future cash flows using the current rates at which similar loans and leases would be made to borrowers with similar credit ratings and for the same remaining maturities less an illiquidity discount, as the fair value measurement represents an exit price from a market participants' viewpoint. The fair value of variable and adjustable rate loans and leases approximates the carrying amount. Due to the significant judgment involved in evaluating credit quality, loans and leases are classified within Level 3 of the fair value hierarchy. Loan Servicing Rights . For both MSRs and SBA servicing rights, both classified as Level 3 assets, fair value is determined using a discounted cash flow valuation method. These models use significant unobservable inputs including discount rates, prepayment rates and cost to service which have greater subjectivity due to the lack of observable market transactions. Derivative Assets and Liabilities. See the “Derivative Financial Instruments” discussion included within this footnote . Deposits. The estimated fair value of demand deposits, savings accounts and certain money market deposits is the amount payable on demand at the reporting date because of the customers’ ability to withdraw funds immediately. The fair value of fixed-maturity deposits is estimated by discounting future cash flows using rates currently offered for deposits of similar remaining maturities. Short-Term Borrowings. The carrying amounts for short-term borrowings approximate fair value for amounts that mature in 90 days or less. The fair value of subordinated notes is estimated by discounting future cash flows using rates currently offered. Long-Term Borrowings. The fair value of long-term borrowings is estimated by discounting future cash flows based on the market prices for the same or similar issues or on the current rates offered to us for debt of the same remaining maturities. Loan Commitments and Standby Letters of Credit. Estimates of the fair value of these off-balance sheet items were not made because of the short-term nature of these arrangements and the credit standing of the counterparties. Also, unfunded loan commitments relate principally to variable rate commercial loans, typically are non-binding, and fees are not normally assessed on these balances. Nature of Estimates . Many of the estimates presented herein are based upon the use of highly subjective information and assumptions and, accordingly, the results may not be precise. Management believes that fair value estimates may not be comparable to other financial institutions due to the wide range of permitted valuation techniques and numerous estimates which must be made. Further, because the disclosed fair value amounts were estimated as of the Balance Sheet date, the amounts actually realized or paid upon maturity or settlement of the various financial instruments could be significantly different. The fair values of our financial instruments are as follows: TABLE 25.5 Fair Value Measurements (in millions) Carrying Fair Level 1 Level 2 Level 3 December 31, 2020 Financial Assets Cash and cash equivalents $ 1,383 $ 1,383 $ 1,383 $ — $ — Debt securities available for sale 3,463 3,463 600 2,863 — Debt securities held to maturity 2,868 2,973 — 2,973 — Net loans and leases, including loans held for sale 25,250 25,012 — 144 24,868 Loan servicing rights 39 39 — — 39 Derivative assets 376 376 — 352 24 Accrued interest receivable 90 90 90 — — Financial Liabilities Deposits 29,122 29,158 25,460 3,698 — Short-term borrowings 1,804 1,809 1,809 — — Long-term borrowings 1,095 1,068 — — 1,068 Derivative liabilities 40 40 — 40 — Accrued interest payable 13 13 13 — — December 31, 2019 Financial Assets Cash and cash equivalents $ 599 $ 599 $ 599 $ — $ — Debt securities available for sale 3,289 3,289 — 3,289 — Debt securities held to maturity 3,275 3,305 — 3,305 — Net loans and leases, including loans held for sale 23,144 22,930 — 41 22,889 Loan servicing rights 46 48 — — 48 Derivative assets 154 154 — 151 3 Accrued interest receivable 109 109 109 — — Financial Liabilities Deposits 24,786 24,797 20,058 4,739 — Short-term borrowings 3,216 3,219 3,219 — — Long-term borrowings 1,340 1,355 — — 1,355 Derivative liabilities 25 25 — 25 — Accrued interest payable 21 21 21 — —

Parent Company Financial Statem

Parent Company Financial Statements	12 Months Ended
	Dec. 31, 2020
Condensed Financial Information Disclosure [Abstract]
Parent Company Financial Statements	PARENT COMPANY FINANCIAL STATEMENTS The following is condensed financial information of F.N.B. Corporation (parent company only). In this information, the parent company’s investments in subsidiaries are stated at cost plus equity in undistributed earnings of subsidiaries since acquisition. This information should be read in conjunction with the Consolidated Financial Statements. TABLE 26.1 Balance Sheets (in millions) December 31 2020 2019 Assets Cash and cash equivalents $ 380 $ 251 Other assets 10 18 Investment in bank subsidiary 5,064 5,072 Investments in and advances to non-bank subsidiaries 371 104 Total Assets $ 5,825 $ 5,445 Liabilities Other liabilities $ 40 $ 34 Advances from affiliates 197 197 Long-term borrowings 621 323 Subordinated notes: Short-term 7 7 Long-term 1 1 Total Liabilities 866 562 Stockholders’ Equity 4,959 4,883 Total Liabilities and Stockholders’ Equity $ 5,825 $ 5,445 TABLE 26.2 Statements of Income (in millions) Year Ended December 31 2020 2019 2018 Income Dividend income from subsidiaries: Bank $ 300 $ 179 $ 162 Non-bank 4 2 8 304 181 170 Interest income 6 — 4 Other income — — 5 Total Income 310 181 179 Expenses Interest expense 25 19 20 Other expenses 18 18 15 Total Expenses 43 37 35 Income Before Taxes and Equity in Undistributed Income of Subsidiaries 267 144 144 Income tax benefit 7 7 6 274 151 150 Equity in undistributed income (loss) of subsidiaries: Bank 15 236 225 Non-bank (3) — (2) Net Income $ 286 $ 387 $ 373 TABLE 26.3 Statements of Cash Flows (in millions) Year Ended December 31 2020 2019 2018 Operating Activities Net income $ 286 $ 387 $ 373 Adjustments to reconcile net income to net cash flows from operating activities: Undistributed earnings from subsidiaries (12) (236) (222) Other, net 13 2 (13) Net cash flows provided by operating activities 287 153 138 Investing Activities Proceeds from sale of securities available for sale — — 1 Net decrease in advances to subsidiaries — — 20 Payment for further investment in subsidiaries (270) (47) (22) Net cash received in business combinations — — 123 Net cash flows (used in) provided by investing activities (270) (47) 122 Financing Activities Net decrease in advance from affiliate — — (19) Net decrease in short-term borrowings — — (1) Decrease in long-term debt (4) (77) (2) Increase in long-term debt 302 121 1 Other, net (21) 12 14 Cash dividends paid: Preferred stock (8) (8) (8) Common stock (157) (157) (157) Net cash flows provided by (used in) financing activities 112 (109) (172) Net Increase (Decrease) in Cash and Cash Equivalents 129 (3) 88 Cash and cash equivalents at beginning of year 251 254 166 Cash and Cash Equivalents at End of Year $ 380 $ 251 $ 254 Cash paid during the year for: Interest $ 26 $ 20 $ 17

Quarterly Earnings Summary (Una

Quarterly Earnings Summary (Unaudited)	12 Months Ended
	Dec. 31, 2020
Quarterly Earnings Summary (Unaudited) [Abstract]
Quarterly Earnings Summary (Unaudited)	QUARTERLY EARNINGS SUMMARY (UNAUDITED) TABLE 27.1 (Dollars in millions, except per share data) Quarter Ended 2020 Dec. 31 Sept. 30 June 30 Mar. 31 Total interest income $ 270 $ 273 $ 281 $ 306 Total interest expense 36 46 52 74 Net interest income 234 227 229 232 Provision for credit losses 18 27 30 48 Total non-interest income 68 80 77 69 Total non-interest expense 199 180 176 195 Net income 72 83 84 47 Net income available to common stockholders 70 81 82 45 Per Common Share Basic earnings per share $ 0.22 $ 0.25 $ 0.25 $ 0.14 Diluted earnings per share 0.22 0.25 0.25 0.14 Quarter Ended 2019 Total interest income $ 306 $ 314 $ 317 $ 310 Total interest expense 80 84 87 79 Net interest income 226 230 230 231 Provision for credit losses 7 12 11 14 Other non-interest income 74 80 75 65 Total non-interest expense 177 178 175 166 Net income 95 103 95 94 Net income available to common stockholders 93 101 93 92 Per Common Share Basic earnings per share $ 0.29 $ 0.31 $ 0.29 $ 0.28 Diluted earnings per share 0.29 0.31 0.29 0.28

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation Our accompanying Consolidated Financial Statements and these Notes to Consolidated Financial Statements include subsidiaries in which we have a controlling financial interest. We own and operate FNBPA, FNTC, First National Investment Services Company, LLC, FNBIA, FNIA, Bank Capital Services, LLC, and F.N.B. Capital Corporation, LLC, and include results for each of these entities in the accompanying Consolidated Financial Statements. Companies in which we hold a controlling financial interest, or are a VIE in which we have the power to direct the activities of an entity that most significantly impact the entity’s economic performance and have an obligation to absorb losses or the right to receive benefits which could potentially be significant to the VIE, are consolidated. For a voting interest entity, a controlling financial interest is generally where we hold more than 50% of the outstanding voting shares. VIEs in which we do not hold the power to direct the activities of the entity that most significantly impact the entity’s economic performance or an obligation to absorb losses or the right to receive benefits which could potentially be significant to the VIE are not consolidated. Investments in companies that are not consolidated are accounted for using the equity method when we have the ability to exert significant influence. Investments in private investment partnerships that are accounted for under the equity method or the cost method are included in other assets and our proportional interest in the equity investments’ earnings are included in other non-interest income. Investment interests accounted for under the cost and equity methods are periodically evaluated for impairment. The accompanying Consolidated Financial Statements include all adjustments that are necessary, in the opinion of management, to fairly reflect our financial position and results of operations in accordance with GAAP. All significant intercompany balances and transactions have been eliminated. Certain prior period amounts have been reclassified to conform to the current period presentation. Such reclassifications had no impact on our net income and stockholders’ equity. Events occurring subsequent to December 31, 2020 have been evaluated for potential recognition or disclosure in the Consolidated Financial Statements through the date of the filing of the Consolidated Financial Statements with the SEC.
Use of Estimates	Use of Estimates Our accounting and reporting policies conform with GAAP. The preparation of financial statements in conformity with GAAP requires us to make estimates and assumptions that affect the amounts reported in the Consolidated Financial Statements and accompanying Notes to Consolidated Financial Statements. Actual results could materially differ from those estimates. Material estimates that are particularly susceptible to significant changes include the ACL, accounting for loans acquired in a business combination prior to January 1, 2020, fair value of financial instruments, goodwill and other intangible assets, income taxes and DTAs.
New Accounting Standards	Adoption of New Accounting Standards Current Expected Credit Losses. On January 1, 2020, we adopted ASU 2016-13, Financial Instruments-Credit Losses (Topic 326), which replaces the incurred credit loss impairment methodology with a methodology that reflects lifetime current expected credit losses (commonly referred to as CECL) for most financial assets measured at amortized cost, including loans, HTM debt securities, net investment in leases and certain off-balance sheet credit exposure. We adopted CECL using the modified retrospective method for financial assets measured at amortized cost, net investments in leases and off-balance sheet credit exposures. As a result, we recorded a reduction of $50.6 million in retained earnings as of January 1, 2020 for the cumulative effect of the adoption. The transition adjustment was primarily driven by longer duration commercial and consumer real estate loans. Results for reporting periods prior to January 1, 2020 continue to be reported in accordance with previously applicable GAAP. We used the prospective transition method for PCD financial assets that were previously classified as PCI and accounted for under ASC 310-30, including loans accounted for by analogy under ASC 310-30. In accordance with the transition guidance, we did not reassess whether PCI assets met the criteria for PCD assets nor did we reassess whether modifications to individual acquired financial assets previously accounted for in pools were TDRs as of the date of adoption. We discontinued the use of pools beyond transition accounting and account for these loans on an individual loan basis. After transition, loans previously accounted for in pools are grouped with other loans with similar risk characteristics for purposes of estimating expected credit losses. As a result, beginning in 2020 certain credit metrics and ratios which previously excluded PCI loans now include PCD loans. On January 1, 2020, the amortized cost basis of the PCD assets was adjusted to reflect the addition of an ACL for $50.3 million. The net noncredit discount, after the adjustment for the ACL, is accreted into interest income at the loan’s effective interest rate over the remaining contractual life. We made an accounting policy election to write-off accrued interest receivable balances by reversing interest income in accordance with our non-accrual policies instead of measuring an ACL for accrued interest receivable for all classes of financing receivables and major security types. We do not hold any securities at adoption for which OTTI had been recognized prior to January 1, 2020. The following table illustrates the impact of the adoption of ASC 326: TABLE 1.1 January 1, 2020 (in millions) As Reported Under ASC 326 Pre-ASC 326 Adoption Impact of ASC 326 Adoption Assets: Allowance for credit losses on debt securities held-to-maturity States of the U.S. and political subdivisions (municipals) $ — $ — $ — Loans Commercial real estate $ 138 $ 60 $ 78 Commercial and industrial 65 53 12 Commercial leases 11 11 — Commercial other — 9 (9) Direct installment 24 13 11 Residential mortgages 32 22 10 Indirect installment 21 19 2 Consumer lines of credit 10 9 1 Allowance for credit losses on loans $ 301 $ 196 $ 105 Liabilities: Allowance for credit losses on off-balance sheet credit exposures $ 13 $ 3 $ 10 Reference Rate Reform. In March 2020, the FASB issued ASU 2020-04, Reference Rate Reform: Facilitation of the Effects of Reference Rate Reform on Financial Reporting (Topic 848), as amended, which provides optional guidance for a limited period of time to ease the potential burden in accounting for changes in financial reporting brought about by RRR for affected contractual modifications of floating rate financial instruments indexed to interbank offering rates and hedge accounting relationships. The expedients, exceptions and elections provided by RRR are permitted to be adopted any time through December 31, 2022 and do not apply to contract modifications made and hedging relationships entered into or evaluated after December 31, 2022, except for certain optional expedients elected for certain hedging relationships existing as of December 31, 2022. In general, RRR provides, when certain criteria are met, optional expedients and exceptions regarding the accounting for contract modifications, hedging relationships and other transactions affected by RRR. It also allows for a one-time transfer or sale of qualifying HTM securities. We adopted RRR on October 1, 2020, and the guidance will be followed until the Update terminates on December 31, 2022. The adoption did not have a material impact on our consolidated financial position or results of operations. We have not yet elected certain optional expedients, exceptions and elections related to RRR, however, we plan to elect these provisions in the future. While RRR is not expected to have a material accounting impact on our consolidated financial position or results of operations, it will ease the administrative burden in accounting for future effects of RRR. The following table summarizes accounting pronouncements issued by the FASB that we recently adopted. TABLE 2.1 Standard Description Financial Statements Impact Credit Losses ASU 2016-13 , Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments ASU 2018-19, Codification Improvements to Topic 326, Financial Instruments - Credit Losses ASU 2019-04, Codification Improvements to Topic 326, Financial Instruments-Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments ASU 2019-05, Financial Instruments-Credit Losses, (Topic 326): Targeted Transition Relief ASU 2019-11, Codification Improvements to Topic 326, Financial Instruments - Credit Losses These Updates replace the current long-standing incurred loss impairment methodology with a methodology that reflects current expected credit losses (commonly referred to as CECL) for most financial assets measured at amortized cost and certain other instruments, including loans, HTM debt securities, net investments in leases and off-balance sheet credit exposures except for unconditionally cancellable commitments. CECL requires loss estimates for the remaining life of the financial asset at the time the asset is originated or acquired, considering historical experience, current conditions and R&S forecasts. In addition, the Update will require the use of a modified AFS debt security impairment model and eliminate the current accounting for PCI loans and debt securities. On January 1, 2020, we adopted CECL using the modified retrospective method for financial assets measured at amortized cost, net investments in leases and off-balance sheet credit exposures. While these Updates change the measurement of the ACL, it does not change the credit risk of our lending portfolios or the ultimate losses in those portfolios. However, the CECL ACL methodology will produce higher volatility in the quarterly provision for credit losses than our prior reserve process. We created a cross-functional management steering group to govern implementation and the Audit and Risk Committees and the Board of Directors received regular updates. For financial assets measured at amortized cost we have implemented a new modeling platform and integrated other auxiliary models to support a calculation of expected credit losses under CECL. We have made decisions on segmentation, a R&S forecast period, a reversion method and period and a historical loss forecast covering the remaining contractual life, adjusted for prepayments as well as other criteria. Based on our portfolio composition and forecasts of relatively stable macroeconomic conditions over the next two years at the adoption date, we recorded an overall ACL of $301 million. This reflected an increase on the originated portfolio of $55 million, primarily driven by our longer duration commercial and consumer real estate loans and a "gross-up" for PCI loans of $50 million. There is no capital impact related to the PCI loans at adoption. The impact for the adoption of CECL was a reduction to retained earnings of $51 million, which included a $10 million increase to the AULC. The impact upon adoption was dependent on the portfolio composition and credit quality, as well as historical experience, current conditions and forecasts of economic conditions and interest rates at the time of adoption. The impact to our AFS and HTM debt securities was immaterial. Model development, as well as the development of policies and procedures and, internal controls were complete at the time of adoption. Standard Description Financial Statements Impact Reference Rate Reform ASU 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting ASU 2021-01, Reference Rate Reform (Topic 848): Scope These Updates provide temporary optional expedients and exceptions for applying GAAP to financial contracts, hedging relationships and other transactions affected by RRR if certain criteria are met. The following optional expedients, exceptions and elections are permitted for certain contracts that are modified because of RRR and meet certain scope guidance: • Contract modifications may be accounted for prospectively as a continuation of existing contracts rather than a new contract without remeasurement or reassessment of significant contract amendments • modifications of leases to be accounted for as a continuation of the existing contracts without reassessment of lease classification and discount rate or remeasurement of lease payments • to not reassess the original conclusion about whether a contract contains an embedded derivative that is clearly and closely related to the host contract • changes to critical terms of hedging relationships, on a hedge-by-hedge basis, without designation of the hedging relationship and various practical expedients and elections designed to allow hedge accounting to continue uninterrupted • modifications of certain derivatives modified to change the rate used for margining, discounting or contract price alignment. The Updates also allow an entity to make a one-time election to sell and/or transfer to HTM securities that are affected by RRR and were classified as HTM before January 1, 2020. RRR Updates are effective for all entities from the beginning of an interim period that includes or is subsequent to March 12, 2020 and terminates on December 31, 2022 on a full retrospective or prospective basis. Although we do not expect RRR to have a material accounting impact on our consolidated financial position or results of operations, the Updates will ease the administrative burden in accounting for the effects of RRR. We adopted these updates on October 1, 2020 by retrospective application. The adoption did not have a material impact on our consolidated financial position or results of operations. We will continue to assess the impact of adoption through the termination date of these Updates on December 31, 2022.
Revenue from Contracts with Customers	Revenue from Contracts with Customers We earn certain revenues from contracts with customers. These revenues are recognized when control of the promised services is transferred to the customers in an amount that reflects the consideration we expect to be entitled to in an exchange for those services. In determining the appropriate revenue recognition for our contracts with customers, we consider whether the contract has commercial substance and is approved by both parties with identifiable contractual rights, payment terms, and the collectability of consideration is probable. Generally, we satisfy our performance obligations upon the completion of services at the amount to which we have the right to invoice or charge under contracts with an original expected duration of one year or less. We apply this guidance on a portfolio basis to contracts with similar characteristics and for which we believe the results would not differ materially from applying this guidance to individual contracts. Our services provided under contracts with customers are transferred at the point in time when the services are rendered. Generally, we do not defer incremental direct costs to obtain contracts with customers that would be amortized in one year or less under the practical expedient. These costs are recognized as expense, primarily salary and benefit expense, in the period incurred. Deposit Services . We recognize revenue on deposit services based on published fees for services provided. Demand and savings deposit customers have the right to cancel their depository arrangements and withdraw their deposited funds at any time without prior notice. When services involve deposited funds that can be retrieved by customers without penalties, we consider the service contract term to be day-to-day, where each day represents the renewal of the contract. The contract does not extend beyond the services performed and revenue is recognized at the end of the contract term (daily) as the performance obligation is satisfied. No deposit services fees exist for long-term deposit products beyond early withdrawal penalties, which are earned on these products at the time of early termination. Revenue from deposit services fees are reduced where we have a history of waived or reduced fees by customer request or due to a customer service issue, by historical experience, or another acceptable method in the same period as the related revenues. Revenues from deposit services are reported in the Consolidated Statements of Income as service charges and in the Community Banking segment as non-interest income. Wealth Management Services. Wealth advisory and trust services are provided on a month-to-month basis and invoiced as services are rendered. Fees are based on a fixed amount or a scale based on the level of services provided or assets under management. The customer has the right to terminate their services agreement at any time. We determine the value of services performed based on the fee schedule in effect at the time the services are performed. Revenues from wealth advisory and trust services are reported in the Consolidated Statements of Income as trust services and securities commissions and fees, and in the Wealth segment as non-interest income. Insurance Services. Insurance services include full-service insurance brokerage services offering numerous lines of commercial and personal insurance through major carriers to businesses and individuals within our geographic markets. We recognize revenue on insurance contracts in effect based on contractually specified commission payments on premiums that are paid by the customer to the insurance carrier. Contracts are cancellable at any time and we have no performance obligation to the customers beyond the time the insurance is placed into effect. Revenues from insurance services are reported in the Consolidated Statements of Income as insurance commissions and fees, and in the Insurance segment as non-interest income.
Business Combinations	Business Combinations Business combinations are accounted for by applying the acquisition method . Under the acquisition method, identifiable assets acquired and liabilities assumed, and any non-controlling interest in the acquiree at the acquisition date are measured at their fair values as of that date, and are recognized separately from goodwill. Results of operations of the acquired entities are included in the Consolidated Statements of Income from the date of acquisition.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents include cash on hand, cash items in transit and amounts due from the FRB and other depository institutions (including interest-bearing deposits).
Debt Securities	Debt Securities Debt securities can be classified as trading securities can be classified as trading, HTM or AFS. As of December 31, 2020 and 2019, we did not hold any trading debt securities. Interest income on debt securities includes amortization of purchase premiums or accretion of discounts. Premiums and discounts on debt securities are generally amortized on the level-yield method without anticipating prepayments, except for mortgage-backed securities where prepayments are anticipated. Premiums on callable debt securities are amortized to their earliest call date. A debt security is placed on non-accrual when principal or interest becomes greater than 90 days delinquent. Interest accrued but not received for a security placed on non-accrual is reversed against interest income. Gains and losses on the sale of securities are recorded on the trade date and are determined using the specific identification method. HTM debt securities are securities that management has the positive intent and ability to hold until their maturity. Such securities are carried at amortized cost. Beginning in 2020, for certain HTM securities we have an expectation of zero expected credit losses. Based on a long history with no credit losses, high credit ratings, guarantees, and/or implied risk-free characteristics, we expect the nonpayment of our UST, Fannie Mae, Freddie Mac, FHLB, Ginnie Mae, and the SBA securities to be zero, and accordingly, have no ACL on those securities. We believe that these qualitative factors are indicators that historical credit loss information should be nominally impacted, if at all, by current conditions and R&S forecasts. As such, we believe that without a change in these indicators, we may continue to assume zero credit losses on securities concluded to exhibit those factors. We also have a portfolio of HTM debt securities where we do not expect credit losses to be zero. This portfolio consists of high-grade municipal securities. To calculate the expected credit losses on these securities we group securities by major security type, rating and maturity and apply respective cumulative default rates from a third party data provider. The baseline credit loss estimate is adjusted using a qualitative approach to account for potential variability in probabilities of default data for current conditions and R&S forecasts. Where available, expected credit losses take into consideration any enhancement a security has such as insurance, a guarantee or state aid. Debt securities that are not classified as trading or HTM are classified as AFS and are carried at fair value. AFS debt securities in unrealized loss positions are evaluated for impairment related to credit losses at least quarterly. Impairment may result from credit deterioration of the issuer or collateral underlying the security. In performing an assessment of whether any decline in fair value is due to a credit loss, all relevant information is considered at the individual security level. Beginning in 2020, for AFS debt securities in an unrealized loss position, we first determine whether we have the intent to sell, or it is more likely than not that we will be required to sell, the security before recovery of its amortized cost basis. If the criteria for intent or requirement to sell is met, the security’s amortized cost is written down to fair value and the write down is charged against the ACL with any incremental impairment reported in earnings in the Provision for Credit Losses line on the Consolidated Statements of Income. For AFS debt securities that do not meet the criteria for intent or requirement to sell, we evaluate whether the decline in fair value has resulted from credit losses or other factors. We first qualitatively evaluate each security to assess whether a potential credit loss exists. If as a result of this qualitative analysis we expect to get all of our principal back, then we conclude that the present value of expected cash flows equals or exceeds its amortized cost and no credit loss exists. If it was determined a potential credit loss exists, we compare the present value of cash flows expected to be collected with our amortized cost basis to measure its value. The credit loss is recorded through the ACL and limited to the amount the fair value is less than the amortized cost basis. We have made an accounting policy election for each major security type of AFS debt securities to adjust the effective interest rate used to discount expected cash flows to consider the timing of expected cash flows resulting from expected prepayments. Impairment for noncredit-related factors is recorded in OCI, net of income taxes. Changes in the ACL are recorded as a provision for credit loss expense. Losses are charged against the ACL when an AFS debt security is not collectible or when we believe the criteria regarding the intent or requirement to sell is met. Prior to 2020, we evaluated our debt securities in a loss position for OTTI on a quarterly basis at the individual security level based on our intent to sell. If we intended to sell the debt security of if it was more likely than not we would have been required to sell the security before recovery of its amortized cost basis, OTTI was recognized in earnings equal to the entire difference between the investments' amortized cost basis and its fair value. If we did not intend to sell the debt security and if it was not more likely than not that we would be required to sell the security before recovery of its amortized cost basis, the OTTI was separated into the amount representing credit loss and the amount related to all other market factors. The amount of credit loss would have been recognized in earnings and the amount related to other market factors would be recognized in OCI, net of tax. We did not recognize any OTTI during 2019 and 2018.
Securities Sold Under Agreements to Repurchase	Securities Sold Under Agreements to Repurchase Securities sold under agreements to repurchase are accounted for as collateralized financing transactions and are recorded at the amounts at which the securities were sold plus accrued interest. Securities, generally U.S. government and federal agency securities, pledged as collateral under these financing arrangements cannot be sold or repledged by the secured party. The fair value of collateral either received from or provided to a third party is continually monitored and additional collateral is obtained or is requested to be returned to us as deemed appropriate.
Derivative Instruments and Hedging Activities	Derivative Instruments and Hedging Activities From time to time, we may enter into derivative transactions principally to protect against the risk of adverse price or interest rate movements on the value of certain assets and liabilities and on future cash flows. Foreign exchange derivatives are entered into to accommodate the needs of customers. All derivative instruments are carried at fair value on the Consolidated Balance Sheets as either an asset or liability. Accounting for the changes in fair value of a derivative is dependent upon whether it has been designated in a formal, qualifying hedging relationship. For derivatives in qualifying hedging relationships, we formally document all relationships between hedging instruments and hedged items, as well as our risk management objective and strategy for undertaking each hedge transaction. Cash flows from hedging activities are classified in the same category as the items hedged. Beginning in the first quarter of 2019, we adopted ASU 2017-12 which provides targeted improvements to the hedge accounting model that more closely aligns the accounting and reporting for hedging relationships with risk management activities. In addition, ASU 2017-12 provides administrative relief by easing documentation requirements, simplifying the application of hedge accounting by expanding the application of the shortcut method, eliminating the separate measurement and reporting of hedge ineffectiveness and generally requiring the entire effect of the hedging instrument and the hedged item to be presented in the same income statement line item. We believe these changes will provide users with more useful information about the effect of our risk management activities on the financial statements. Changes in fair value of a derivative instrument that has been designated and qualifies as a cash flow hedge, including any ineffectiveness, are recorded in AOCI, net of tax. Amounts are reclassified from AOCI to the consolidated statements of income in the same line item used to present the earnings effect of the hedged item in the period or periods in which the hedged transaction affects earnings. Prior to 2019, the ineffective portion, if any, was reported in earnings immediately. At the hedge’s inception, a formal assessment is performed to determine whether changes in the fair values or cash flows of the derivative instruments have been highly effective in offsetting changes in fair values or cash flows of the hedged items and whether they are expected to be highly effective in the future. At each reporting period thereafter, a statistical regression or qualitative analysis is performed to evaluate hedge effectiveness. If it is determined a derivative instrument has not been or will not continue to be highly effective as a hedge, hedge accounting is discontinued.
Loans Held for Sale and Loan Commitments	Loans Held for Sale and Loan Commitments Certain of our residential mortgage loans are originated or purchased for sale in the secondary mortgage loan market. We make an automatic election to account for all originated or purchased residential mortgage loans held for sale under the FVO. The FVO election is intended to better reflect the underlying economics and better facilitate the economic hedging of the loans. The FVO is applied on an instrument by instrument basis and is an irrevocable election. Additionally, with the election of the FVO, fees and costs associated with the origination and acquisition of residential mortgage loans held for sale are expensed as incurred, rather than deferred. Changes in fair value under the FVO are recorded in mortgage banking operations non-interest income on the consolidated statements of income. Fair value is determined on the basis of rates obtained in the respective secondary market for the type of loan held for sale. Gain or loss on the sale of loans is recorded in mortgage banking operations non-interest income. Interest income on loans held for sale is recorded in interest income. We routinely IRLCs for residential mortgage loans that we intend to sell. These IRLCs are considered derivatives. We also enter into loan sale commitments to sell these loans when funded to mitigate the risk that the market value of residential mortgage loans may decline between the time the rate commitment is issued to the customer and the time we sell the loan. These loan sale commitments are also derivatives. Both types of derivatives are recorded at fair value on the Consolidated Balance Sheets with changes in fair value recorded in mortgage banking operations non-interest income. We also originate loans guaranteed by the SBA for the purchase of businesses, business startups, business expansion, equipment, and working capital. All SBA loans are underwritten and documented as prescribed by the SBA. SBA loans originated with the intention to sell on the secondary market are classified as held for sale and carried at the lower of cost or fair value. At the time of the sale, we allocate the carrying value of the entire loan between the guaranteed portion sold and the unguaranteed portion retained based on their relative fair value which results in a discount recorded on the retained portion of the loan. The guaranteed portion is typically sold at a premium and the gain is recognized in other income for any net premium received in excess of the relative fair value of the portion of the loan transferred. The net carrying value of the retained portion of the loans is included in the appropriate commercial loan classification for disclosure purposes.
Loans	Loans Loans we intend to hold for the foreseeable future or until maturity or payoff are reported at amortized cost, net of the ACL. Amortized cost primarily consists of the principal balances outstanding, deferred origination fees or costs and premiums or discounts on purchased loans. Interest income on loans is computed over the term of the loans using the effective interest method. Loan origination fees or costs, premiums or discounts are deferred and amortized over the term of the loan or loan commitment period as an adjustment to the related loan yield.
Non-performing Loans	Non-performing Loans We place loans on non-accrual status and discontinue interest accruals on loans generally when principal or interest is due and has remained unpaid for a certain number of days, unless the loan is both well secured and in the process of collection. Commercial loans and leases are placed on non-accrual at 90 days, installment loans are placed on non-accrual at 120 days and residential mortgages and consumer lines of credit are generally placed on non-accrual at 180 days, though we may place a loan on non-accrual prior to these past due thresholds as warranted. When a loan is placed on non-accrual status, all unpaid accrued interest is reversed against interest income and the amortization of deferred fees and costs is suspended. Non-accrual loans may not be restored to accrual status until all delinquent principal and interest have been paid and the ultimate ability to collect the remaining principal and interest is reasonably assured. Loans are charged-off against the ACL and recoveries of amounts previously charged-off are credited to the ACL when realized. Prior to 2020, PCI loans were not classified as non-performing assets as the loans were considered to be performing. Beginning in 2020, PCI loans previously accounted for in pools are grouped with other loans with similar risk characteristics for purposes of estimating expected credit losses and non-performing classification. Troubled Debt Restructured Loans Debt restructurings or loan modifications for a borrower occur in the normal course of business and do not necessarily constitute TDRs. In general, the modification or restructuring of a debt constitutes a TDR, including reasonably expected TDR, if, for economic or legal reasons related to the borrower’s financial difficulties, we grant a concession to the borrower that we would not otherwise consider under current market conditions or once we have determined that a loan modification for a financially troubled borrower is the most appropriate strategy. Additionally, a loan designated as a TDR does not necessarily result in the automatic placement of the loan on non-accrual status. When the full collection of principal and interest is reasonably assured on a loan designated as a TDR and where the borrower would not otherwise meet the criteria for non-accrual status, we will continue to accrue interest on the loan. Prior to 2020, we did not consider a restructured acquired loan as a TDR if the loan was accounted for as a component of a pool. TDR classification does not include short-term assistance to borrowers who are current at the time of a natural disaster or other extreme event (e.g. floods, hurricanes and pandemics). These borrowers are considered to not be experiencing financial difficulty at the time of modification, therefore not meeting the criteria for determining TDR status. For modifications of leases related to the effects of the COVID-19 pandemic that do not result in a substantial increase in our rights as lessor or the obligations of the lessee, we elect to account for these lease concessions as though enforceable rights and obligations for those concessions existed in the original contracts. We account for these concessions as if no changes were made to the lease contract.
Allowance for Credit Losses on Loans and Leases	Allowance for Credit Losses on Loans and Leases Beginning January 1, 2020, we estimate the ACL on loans and leases using relevant available information, from internal and external sources, relating to past events, current conditions, and R&S forecasts under the CECL methodology. The ACL is measured on a collective (pool) basis when similar risk characteristics exist. Our portfolio segmentation is characterized by similarities in initial measurement, risk attributes, and the manner in which we monitor and assess credit risk and is comprised of commercial real estate, commercial and industrial, commercial leases, commercial - other, direct installment, residential mortgages, indirect installment and consumer lines of credit. The ACL on loans and leases represents our current estimate of lifetime credit losses in our loan portfolio at the balance sheet date. In determining the ACL, we estimate expected future losses for the loan's entire contractual term adjusted for expected prepayments when appropriate. The contractual term excludes expected extensions, renewals, and modifications. The ACL is the sum of three components: quantitative (formulaic or pooled) reserves; asset specific / individual loan reserves; and qualitative (judgmental) reserves. Quantitative Component We use a non-discounted cash flow factor-based approach to estimate expected credit losses that include component PD/LGD/EAD models as well as less complex estimation methods for smaller loan portfolios. • PD: This component model is used to estimate the likelihood that a borrower will cease making payments as agreed. The major contributors to this are the borrower credit attributes and macro-economic trends. • LGD: This component model is used to estimate the loss on a loan once a loan is in default. • EAD: Estimates the loan balance at the time the borrower stops making payments. For all term loans, an amortization based formulaic approach is used for account level EAD estimates. We calculate EAD using a portfolio specific method in each of our revolving product portfolios. Asset Specific / Individual Component Loans that do not share risk characteristics are generally evaluated on an individual basis. Loans evaluated individually are not included in the collective evaluation. We have elected to apply the practical expedient to measure expected credit losses of a collateral dependent asset using the fair value of the collateral, less any costs to sell. Individual reserves are determined as follows: • For commercial loans in default which are greater than or equal to $1.0 million, individual reserves are determined based on an analysis of the present value of the loan's expected future cash flows, the loan's observable market value, or the fair value of the collateral less costs to sell. • For commercial and consumer loans in default which are below $1.0 million, an established LGD percentage is multiplied by the loan balance and the results are aggregated for purposes of measuring specific reserve impairment. Qualitative Component The ACL also includes identified qualitative factors related to distinctive risk factors, changes in current economic conditions that may not be reflected in quantitatively derived results, and other relevant factors to ensure the ACL reflects our best estimate of CECL. While our reserve methodologies strive to reflect all relevant risk factors, there continues to be uncertainty associated with, but not limited to, potential imprecision in the estimation process due to the inherent time lag of obtaining information and normal variations between estimates and actual outcomes. We provide additional reserves that are designed to provide coverage for losses attributable to such risks. The ACL also includes factors that may not be directly measured in the determination of individual or collective reserves. Such qualitative factors may include: • Lending policies and procedures, including changes in policies and underwriting standards and practices for collections, write-offs, and recoveries; • The experience, ability, and depth of lending, investment, collection, and other relevant personnel; • The quality of the institution’s credit review function; • Concentrations of credit or changes in the level of such concentration; • The effect of other external factors such as the regulatory, legal and technological environments; competition; and events such as natural disasters and other relevant factors; and • Forecast uncertainty and imprecision. Prior to 2020, the allowance for credit losses was established as losses were estimated to have occurred. Loan losses were charged-off against the allowance for credit losses when management believed the uncollectability of a loan balance was confirmed. Subsequent recoveries, if any, were credited to the allowance for credit losses. Allowances for impaired commercial loans over $1.0 million were generally determined based on collateral values or the present value of estimated cash flows. All other impaired loans were evaluated in the aggregate based on loan segment loss given default. Changes in the allowance for credit losses related to impaired loans were charged or credited to the provision for credit losses. Liability for Credit Losses on Unfunded Lending-Related Commitments The AULC is management's estimate of credit losses inherent in our unfunded loan commitments, such as letters of credit and home equity lines of credit, and is included in other liabilities on the Consolidated Balance Sheets. The AULC is estimated over the contractual period in which we are exposed to credit risk for obligations which are not unconditionally cancellable by us. The AULC is adjusted through provision for credit losses. The estimate includes consideration of the likelihood that funding will occur and an estimate of expected credit losses on commitments expected to be funded over its estimated useful life. Consistent with our estimation process on our loan and lease portfolio, we use a non-discounted cash flow factor-based approach to estimate expected credit losses that include component PD/LGD/EAD models as well as less complex estimation methods for smaller portfolios.
Purchased Credit Deteriorated Loans and Leases	Purchased Credit Deteriorated Loans and Leases We have purchased loans and leases, some of which have experienced more than insignificant credit deterioration since origination. Beginning in 2020, we have established criteria to assess whether a purchased financial asset, or group of assets, should be accounted for as PCD on the acquisition date. The selection of which criteria to apply, or the addition of new criteria, to a specific acquisition will be based on the facts and circumstances at the time of review, as well as the availability of information supplied by the acquiree. Generally, more-than-insignificant deterioration in credit quality since origination would include risk ratings of special mention or below, inconsistency of loan payments, non-accrual status at the time of acquisition, or loans modified in a TDR, in bankruptcy or for regulatory purposes. PCD loans are recorded at the amount paid. The initial ACL is determined using the same methodology as other loans held for investment on a collective basis and is allocated to individual loans. The sum of the loan’s purchase price and the ACL becomes the initial amortized cost basis. The difference between the initial amortized cost basis and the par value of the loan is a noncredit discount or premium, which is amortized or accreted into interest income over the life of the loan. Subsequent changes to the ACL are recorded through the provision credit losses. Prior to 2020, loans acquired in a business combination (impaired and non-impaired) were initially recorded at their acquisition-date fair values. Fair values were based on a discounted cash flow methodology that involved assumptions and judgments as to credit risk, default rates, loss severity, collateral values, discount rates, payment speeds, prepayment risk, and liquidity risk. The carryover of allowance for credit losses related to loans acquired in a business combination was prohibited as any credit losses in the loans were included in the determination of the fair value of the loans at the acquisition date. The allowance for credit losses on loans acquired in a business combination reflected only those losses incurred after acquisition and represents the present value of cash flows expected at acquisition that is no longer expected to be collected. At acquisition, we considered certain factors as indicators that an acquired loan has evidence of deterioration in credit quality and is therefore impaired. Any loans acquired in a business combination that were not individually impaired were pooled into groups of similar loans based on various factors including borrower type, loan purpose, and collateral type. For these pools, we used certain loan information, including outstanding principal balance, estimated expected losses, weighted average maturity, weighted average margin, and weighted average interest rate along with estimated prepayment rates, probability of default and loss given default to estimate the expected cash flow for each loan pool. We believe analogizing to impaired loans was a more appropriate option to follow in accounting for discount accretion on nonimpaired loans acquired in a business combination other than revolving loans and therefore account for such loans in accordance with the guidance for impaired loans, excluding revolving loans. The excess of cash flows expected to be collected at acquisition over recorded fair value is referred to as the accretable yield. The accretable yield was recognized into income over the remaining life of the loan, or pool of loans, using an effective yield method, if the timing and/or amount of cash flows expected to be collected can be reasonably estimated (the accretion model). The difference between the loan’s total scheduled principal and interest payments over all cash flows expected at acquisition is referred to as the non-accretable difference. The non-accretable difference represents contractually required principal and interest payments which we do not expect to collect. Loans acquired in a business combination that met the criteria for non-accrual of interest prior to acquisition were considered performing upon acquisition, regardless of whether the customer was contractually delinquent, if we could reasonably estimate the timing and amount of expected cash flows on such loans. Accordingly, we did not consider contractually delinquent purchased credit impaired loans to be non-accrual or non-performing and we continued to recognize interest income on these loans using the accretion model.
Premises and Equipment	Premises and Equipment Premises and equipment are stated at cost less accumulated depreciation. Depreciation is computed using the straight-line method over the asset’s estimated useful life. Leasehold improvements are expensed over the lesser of the asset’s estimated useful life or the term of the lease including renewal periods when reasonably assured. Useful lives are dependent upon the nature and condition of the asset and range from 3 to 39 years. Maintenance and repairs are charged to expense as incurred, while major improvements are capitalized and amortized to expense over the identified useful life.
Cloud Computing Arrangements	Cloud Computing Arrangements W e evaluate fees paid for cloud computing arrangements to determine if those arrangements include the purchase of or license to use software that should be accounted for separately as internal-use software. If a contract includes the purchase or license to use software that should be accounted for separately as internal-use software, the contract is amortized over the software’s identified useful life in amortization of intangibles. For contracts that do not include a software license, the contract is accounted for as a service contract with fees paid recorded in other non-interest expense.
Other Real Estate Owned	Other Real Estate Owned OREO is comprised principally of commercial and residential real estate properties obtained in partial or total satisfaction of loan obligations. OREO acquired in settlement of indebtedness is included in other assets initially at fair value of the asset less estimated selling costs. Subsequent to acquisition, OREO is accounted for at the lower of amortized cost or fair value less estimated selling costs. Changes to the value subsequent to transfer are recorded in non-interest expense along with direct operating expenses. Gains or losses not previously recognized resulting from sales of OREO are recognized in non-interest income on the date of sale.
Goodwill and Other Intangible Assets	Goodwill and Other Intangible Assets Goodwill represents the excess of the cost of an acquisition over the fair value of the net assets acquired. Other intangible assets represent purchased assets that lack physical substance but can be distinguished from goodwill because of contractual or other legal rights. Intangible assets that have finite lives, such as core deposit intangibles, customer relationship intangibles and renewal lists, are amortized over their estimated useful lives and subject to periodic impairment testing. Core deposit intangibles are primarily amortized over ten years using accelerated methods. Customer renewal lists are amortized over their estimated useful lives which range from eight Goodwill and other intangibles are subject to impairment testing at the reporting unit level, which must be conducted at least annually. We perform impairment testing during the fourth quarter of each year, or more frequently if impairment indicators exist. We also continue to monitor other intangibles for impairment and to evaluate carrying amounts, as necessary. Quarterly, we perform a goodwill impairment assessment. We first assess qualitative factors to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying value. Qualitative factors include, among other things, macroeconomic conditions, industry and market considerations, financial performance of the respective reporting unit and other relevant entity- and reporting-unit specific considerations. If we conclude it is more likely than not that the fair value of a reporting unit is less than its carrying value, a quantitative assessment is performed. If the quantitative assessment results in the fair value of the reporting unit exceeding its carrying value, goodwill of the reporting unit is considered not impaired; however, if the carrying value of the reporting unit exceeds its fair value an impairment charge is recorded for the excess, limited to the amount of goodwill assigned to a reporting unit.
Loan Servicing Rights	Loan Servicing Rights We have two primary classes of servicing rights, residential mortgage loan servicing and SBA-guaranteed loan servicing. We recognize the right to service residential mortgage loans and SBA-guaranteed loans for others as an asset whether we purchase the servicing rights or as a result from a sale of loans that we originated or purchased when the servicing is contractually separated from the underlying loan and retained by us. We initially record servicing rights at fair value in other assets on the Consolidated Balance Sheets. Subsequently, servicing rights are measured at the lower of cost or fair value. Servicing rights are amortized in proportion to, and over the period of, estimated net servicing income in mortgage banking operations non-interest income for residential mortgage loans and other non-interest income for SBA-guaranteed loans. The amount and timing of estimated future net cash flows are updated based on actual results and updated projections. MSRs are separated into pools based on common risk characteristics of the underlying loans and evaluated for impairment at least quarterly. SBA-guaranteed servicing rights are evaluated for impairment at least quarterly on an aggregate basis. Impairment, if any, is recognized when carrying value exceeds the fair value as determined by calculating the present value of
Bank-Owned Life Insurance (BOLI)	Bank Owned Life Insurance We have purchased life insurance policies on certain current and former directors, officers and employees for which the Corporation is the owner and beneficiary. These policies are recorded in the Consolidated Balance Sheets at their cash surrender value, or the amount that could be realized by surrendering the policies. Tax-exempt income from death benefits and changes in the net cash surrender value are recorded in BOLI non-interest income.
Low Income Housing Tax Credit Partnerships	Low Income Housing Tax Credit Partnerships We invest in various affordable housing projects that qualify for LIHTCs. The net investments are recorded in other assets on the Consolidated Balance Sheets. These investments generate a return through the realization of federal tax credits. We use the proportional amortization method to account for a majority of our investments in these entities. LIHTCs that do not meet the requirements of the proportional amortization method are recognized using the equity method.
Leases, lessee	Leases We determine if an arrangement is, or contains, a lease at inception of the contract. As a lessee, we consider a contract to be, or contain, a lease if the contract conveys the right to control the use of an identified asset in exchange for consideration. We recognize in our Consolidated Balance Sheets the obligation to make lease payments and a right-of-use asset representing our right to use the underlying asset for the lease term. For an operating lease, the right-of-use asset and lease liability are included in other assets and other liabilities, respectively. Finance leases are included in premises and equipment, and other liabilities. We do not record leases with an initial term of 12 months or less on the Consolidated Balance Sheets, instead we recognize lease expense for these leases on a straight-line basis over the lease term. For leases that commenced before January 1, 2019, we have applied the modified retrospective transition method which resulted in comparative information not being restated. A number of optional practical expedients were available in transition. We elected the ‘package of practical expedients’, which permits us to not reassess our prior conclusions about lease identification, lease classification and initial direct costs. Right-of-use assets and liabilities are initially measured at the present value of lease payments over the lease term, discounted using the interest rate implicit in the lease at the commencement date. Right-of-use assets are adjusted for any lease payments made prior to lease commencement, lease incentives, and accrued rent. If the rate implicit in the lease cannot be readily determined, we discount the lease using our incremental borrowing rate which is derived by reference to FNB's secured borrowing rate. Our leases may include options to extend or terminate the lease. When it is reasonably certain that we will exercise such an option, the lease term includes those periods. Lease expense for operating leases is recognized on a straight-line basis over the lease term. Lease expense for finance leases is recognized using the effective interest method. Certain of our lease agreements include variable rental payments based on a percentage of transactions and others include variable rental payments that periodically adjust to rates and charges stated in the agreements. Variable costs, such as maintenance expenses, property taxes, property insurance, transaction-based lease payments and index-based rate increases, are expensed as incurred. Right-of-use assets are reviewed for impairment when events or circumstances indicate that the carrying amount may not be recoverable. For operating leases, if deemed impaired, the right-of-use asset is written down and the remaining balance is subsequently amortized on a straight-line basis. We have real estate lease agreements with lease and non-lease components, which are generally accounted for as a single lease component.
Leases, lessor	As a lessor, when a lease meets certain criteria indicating that we effectively have transferred control of the underlying asset to the customer, the lease is classified as a sales-type lease. When a lease does not meet the criteria for a sales-type lease but meets the criteria of a direct financing lease, the lease is classified as a direct financing lease. When none of the required criteria for sales-type lease or direct-financing lease are met, the lease is classified as an operating lease. Both sales-type leases and direct financing leases are recognized as a net investment in the lease on the Consolidated Balance Sheets. The net investment comprises the lease receivable including any residual value of the underlying asset that is guaranteed by the customer or any other third party unrelated to us and the unguaranteed residual value of the underlying asset. Operating lease income is recognized over the lease term on a straight-line basis. We do not evaluate whether sales taxes and similar taxes imposed by a governmental authority on lease transactions and collected by us are our primary obligation as owner of the underlying leased asset and exclude from lease income all taxes collected.
Income Taxes	Income Taxes We file a consolidated federal income tax return. The provision for federal and state income taxes is based on income reported on the Consolidated Financial Statements, rather than the amounts reported on the respective income tax returns. DTAs and DTLs are computed using tax rates expected to apply to taxable income in the years in which those assets and liabilities are expected to be realized. The effect on DTAs and DTLs resulting from a change in tax rates is recognized as income or expense in the period that the change in tax rates is enacted. We make certain estimates and judgments in determining income tax expense for financial statement purposes. These estimates and judgments are applied in the calculation of certain tax credits and in the calculation of the deferred income tax expense or benefit associated with certain DTAs and DTLs. Significant changes to these estimates may result in an increase or decrease to our tax provision in a subsequent period. We recognize interest and/or penalties related to income tax matters in income tax expense. We assess the likelihood that we will be able to recover our DTAs. If recovery is not likely, we will increase our valuation allowance against the DTAs that are unlikely to be recovered by recording a provision for income taxes. We believe that we will ultimately recover the DTAs recorded on our Consolidated Balance Sheets. We periodically review the tax positions we take on our tax return and apply a more likely than not recognition threshold for all tax positions that are uncertain. The amount recognized in the Consolidated Financial Statements is the largest amount of tax benefit that is greater than 50% likely of being realized on examination. For tax positions not meeting the more likely than not test, no tax benefit is recorded.
Marketing Costs	Marketing Costs Marketing costs are generally expensed as incurred. Marketing expense totaled $12.6 million, $13.1 million and $12.8 million for 2020, 2019 and 2018, respectively.
Per Share Amounts	Per Share Amounts Earnings per common share is computed using net income available to common stockholders, which is net income adjusted for preferred stock dividends. Basic earnings per common share is calculated by dividing net income available to common stockholders by the weighted average number of shares of common stock outstanding, net of unvested shares of restricted stock. Diluted earnings per common share is calculated by dividing net income available to common stockholders by the weighted average number of shares of common stock outstanding, adjusted for the dilutive effect of potential common shares issuable for stock options, warrants and restricted shares, as calculated using the treasury stock method. Adjustments to net income available to common stockholders and the weighted average number of shares of common stock outstanding are made only when such adjustments dilute earnings per common share. The assumed proceeds from applying the treasury stock method when computing diluted earnings per share excludes the amount of excess tax benefits that would have been recognized in accumulated paid-in capital.
Retirement Plans	Retirement Plans We sponsor retirement plans for our employees. The calculation of the obligations and related expenses under these plans requires use of actuarial valuation methods and assumptions. The plans utilize assumptions and methods including reflecting trust assets at their fair value for the qualified pension plans and recognizing the overfunded and underfunded status of the plans on our Consolidated Balance Sheets. Gains and losses, prior service costs and credits are recognized in AOCI, net of tax, until they are amortized, or immediately upon curtailment.
Stock Based Compensation	Stock-Based Compensation Our stock-based compensation awards require the measurement and recognition of compensation expense, based on estimated fair values, for all stock-based awards, including stock options and restricted stock units, made to employees and stock awards made to directors. Generally, these restricted stock unit awards to employees vest over a three We are required to estimate the fair value of stock-based awards on the date of grant. For time-based awards, the value of the award is recognized as expense in our Consolidated Statements of Income over the shorter of requisite service periods or the period through the date that the employee first becomes eligible to retire. We granted restricted stock unit awards with multiple-conditions, both performance and market conditions. These awards are accounted for by considering the market condition in the grant date fair value and recognizing compensation expense over the service period based on the grant date fair value and the probability that the performance condition will be met. We account for forfeitures as they occur.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Schedule of New Accounting Pronouncements and Changes in Accounting Principles	The following table illustrates the impact of the adoption of ASC 326: TABLE 1.1 January 1, 2020 (in millions) As Reported Under ASC 326 Pre-ASC 326 Adoption Impact of ASC 326 Adoption Assets: Allowance for credit losses on debt securities held-to-maturity States of the U.S. and political subdivisions (municipals) $ — $ — $ — Loans Commercial real estate $ 138 $ 60 $ 78 Commercial and industrial 65 53 12 Commercial leases 11 11 — Commercial other — 9 (9) Direct installment 24 13 11 Residential mortgages 32 22 10 Indirect installment 21 19 2 Consumer lines of credit 10 9 1 Allowance for credit losses on loans $ 301 $ 196 $ 105 Liabilities: Allowance for credit losses on off-balance sheet credit exposures $ 13 $ 3 $ 10 The following table summarizes accounting pronouncements issued by the FASB that we recently adopted. TABLE 2.1 Standard Description Financial Statements Impact Credit Losses ASU 2016-13 , Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments ASU 2018-19, Codification Improvements to Topic 326, Financial Instruments - Credit Losses ASU 2019-04, Codification Improvements to Topic 326, Financial Instruments-Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments ASU 2019-05, Financial Instruments-Credit Losses, (Topic 326): Targeted Transition Relief ASU 2019-11, Codification Improvements to Topic 326, Financial Instruments - Credit Losses These Updates replace the current long-standing incurred loss impairment methodology with a methodology that reflects current expected credit losses (commonly referred to as CECL) for most financial assets measured at amortized cost and certain other instruments, including loans, HTM debt securities, net investments in leases and off-balance sheet credit exposures except for unconditionally cancellable commitments. CECL requires loss estimates for the remaining life of the financial asset at the time the asset is originated or acquired, considering historical experience, current conditions and R&S forecasts. In addition, the Update will require the use of a modified AFS debt security impairment model and eliminate the current accounting for PCI loans and debt securities. On January 1, 2020, we adopted CECL using the modified retrospective method for financial assets measured at amortized cost, net investments in leases and off-balance sheet credit exposures. While these Updates change the measurement of the ACL, it does not change the credit risk of our lending portfolios or the ultimate losses in those portfolios. However, the CECL ACL methodology will produce higher volatility in the quarterly provision for credit losses than our prior reserve process. We created a cross-functional management steering group to govern implementation and the Audit and Risk Committees and the Board of Directors received regular updates. For financial assets measured at amortized cost we have implemented a new modeling platform and integrated other auxiliary models to support a calculation of expected credit losses under CECL. We have made decisions on segmentation, a R&S forecast period, a reversion method and period and a historical loss forecast covering the remaining contractual life, adjusted for prepayments as well as other criteria. Based on our portfolio composition and forecasts of relatively stable macroeconomic conditions over the next two years at the adoption date, we recorded an overall ACL of $301 million. This reflected an increase on the originated portfolio of $55 million, primarily driven by our longer duration commercial and consumer real estate loans and a "gross-up" for PCI loans of $50 million. There is no capital impact related to the PCI loans at adoption. The impact for the adoption of CECL was a reduction to retained earnings of $51 million, which included a $10 million increase to the AULC. The impact upon adoption was dependent on the portfolio composition and credit quality, as well as historical experience, current conditions and forecasts of economic conditions and interest rates at the time of adoption. The impact to our AFS and HTM debt securities was immaterial. Model development, as well as the development of policies and procedures and, internal controls were complete at the time of adoption. Standard Description Financial Statements Impact Reference Rate Reform ASU 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting ASU 2021-01, Reference Rate Reform (Topic 848): Scope These Updates provide temporary optional expedients and exceptions for applying GAAP to financial contracts, hedging relationships and other transactions affected by RRR if certain criteria are met. The following optional expedients, exceptions and elections are permitted for certain contracts that are modified because of RRR and meet certain scope guidance: • Contract modifications may be accounted for prospectively as a continuation of existing contracts rather than a new contract without remeasurement or reassessment of significant contract amendments • modifications of leases to be accounted for as a continuation of the existing contracts without reassessment of lease classification and discount rate or remeasurement of lease payments • to not reassess the original conclusion about whether a contract contains an embedded derivative that is clearly and closely related to the host contract • changes to critical terms of hedging relationships, on a hedge-by-hedge basis, without designation of the hedging relationship and various practical expedients and elections designed to allow hedge accounting to continue uninterrupted • modifications of certain derivatives modified to change the rate used for margining, discounting or contract price alignment. The Updates also allow an entity to make a one-time election to sell and/or transfer to HTM securities that are affected by RRR and were classified as HTM before January 1, 2020. RRR Updates are effective for all entities from the beginning of an interim period that includes or is subsequent to March 12, 2020 and terminates on December 31, 2022 on a full retrospective or prospective basis. Although we do not expect RRR to have a material accounting impact on our consolidated financial position or results of operations, the Updates will ease the administrative burden in accounting for the effects of RRR. We adopted these updates on October 1, 2020 by retrospective application. The adoption did not have a material impact on our consolidated financial position or results of operations. We will continue to assess the impact of adoption through the termination date of these Updates on December 31, 2022.

New Accounting Standards (Table

New Accounting Standards (Tables)	12 Months Ended
	Dec. 31, 2020
Accounting Changes and Error Corrections [Abstract]
Schedule of New Accounting Pronouncements and Changes in Accounting Principles	The following table illustrates the impact of the adoption of ASC 326: TABLE 1.1 January 1, 2020 (in millions) As Reported Under ASC 326 Pre-ASC 326 Adoption Impact of ASC 326 Adoption Assets: Allowance for credit losses on debt securities held-to-maturity States of the U.S. and political subdivisions (municipals) $ — $ — $ — Loans Commercial real estate $ 138 $ 60 $ 78 Commercial and industrial 65 53 12 Commercial leases 11 11 — Commercial other — 9 (9) Direct installment 24 13 11 Residential mortgages 32 22 10 Indirect installment 21 19 2 Consumer lines of credit 10 9 1 Allowance for credit losses on loans $ 301 $ 196 $ 105 Liabilities: Allowance for credit losses on off-balance sheet credit exposures $ 13 $ 3 $ 10 The following table summarizes accounting pronouncements issued by the FASB that we recently adopted. TABLE 2.1 Standard Description Financial Statements Impact Credit Losses ASU 2016-13 , Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments ASU 2018-19, Codification Improvements to Topic 326, Financial Instruments - Credit Losses ASU 2019-04, Codification Improvements to Topic 326, Financial Instruments-Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments ASU 2019-05, Financial Instruments-Credit Losses, (Topic 326): Targeted Transition Relief ASU 2019-11, Codification Improvements to Topic 326, Financial Instruments - Credit Losses These Updates replace the current long-standing incurred loss impairment methodology with a methodology that reflects current expected credit losses (commonly referred to as CECL) for most financial assets measured at amortized cost and certain other instruments, including loans, HTM debt securities, net investments in leases and off-balance sheet credit exposures except for unconditionally cancellable commitments. CECL requires loss estimates for the remaining life of the financial asset at the time the asset is originated or acquired, considering historical experience, current conditions and R&S forecasts. In addition, the Update will require the use of a modified AFS debt security impairment model and eliminate the current accounting for PCI loans and debt securities. On January 1, 2020, we adopted CECL using the modified retrospective method for financial assets measured at amortized cost, net investments in leases and off-balance sheet credit exposures. While these Updates change the measurement of the ACL, it does not change the credit risk of our lending portfolios or the ultimate losses in those portfolios. However, the CECL ACL methodology will produce higher volatility in the quarterly provision for credit losses than our prior reserve process. We created a cross-functional management steering group to govern implementation and the Audit and Risk Committees and the Board of Directors received regular updates. For financial assets measured at amortized cost we have implemented a new modeling platform and integrated other auxiliary models to support a calculation of expected credit losses under CECL. We have made decisions on segmentation, a R&S forecast period, a reversion method and period and a historical loss forecast covering the remaining contractual life, adjusted for prepayments as well as other criteria. Based on our portfolio composition and forecasts of relatively stable macroeconomic conditions over the next two years at the adoption date, we recorded an overall ACL of $301 million. This reflected an increase on the originated portfolio of $55 million, primarily driven by our longer duration commercial and consumer real estate loans and a "gross-up" for PCI loans of $50 million. There is no capital impact related to the PCI loans at adoption. The impact for the adoption of CECL was a reduction to retained earnings of $51 million, which included a $10 million increase to the AULC. The impact upon adoption was dependent on the portfolio composition and credit quality, as well as historical experience, current conditions and forecasts of economic conditions and interest rates at the time of adoption. The impact to our AFS and HTM debt securities was immaterial. Model development, as well as the development of policies and procedures and, internal controls were complete at the time of adoption. Standard Description Financial Statements Impact Reference Rate Reform ASU 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting ASU 2021-01, Reference Rate Reform (Topic 848): Scope These Updates provide temporary optional expedients and exceptions for applying GAAP to financial contracts, hedging relationships and other transactions affected by RRR if certain criteria are met. The following optional expedients, exceptions and elections are permitted for certain contracts that are modified because of RRR and meet certain scope guidance: • Contract modifications may be accounted for prospectively as a continuation of existing contracts rather than a new contract without remeasurement or reassessment of significant contract amendments • modifications of leases to be accounted for as a continuation of the existing contracts without reassessment of lease classification and discount rate or remeasurement of lease payments • to not reassess the original conclusion about whether a contract contains an embedded derivative that is clearly and closely related to the host contract • changes to critical terms of hedging relationships, on a hedge-by-hedge basis, without designation of the hedging relationship and various practical expedients and elections designed to allow hedge accounting to continue uninterrupted • modifications of certain derivatives modified to change the rate used for margining, discounting or contract price alignment. The Updates also allow an entity to make a one-time election to sell and/or transfer to HTM securities that are affected by RRR and were classified as HTM before January 1, 2020. RRR Updates are effective for all entities from the beginning of an interim period that includes or is subsequent to March 12, 2020 and terminates on December 31, 2022 on a full retrospective or prospective basis. Although we do not expect RRR to have a material accounting impact on our consolidated financial position or results of operations, the Updates will ease the administrative burden in accounting for the effects of RRR. We adopted these updates on October 1, 2020 by retrospective application. The adoption did not have a material impact on our consolidated financial position or results of operations. We will continue to assess the impact of adoption through the termination date of these Updates on December 31, 2022.

Securities (Tables)

Securities (Tables)	12 Months Ended
	Dec. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Schedule of Amortized Cost and Fair Value of Securities Available for Sale	TABLE 3.1 (in millions) Amortized Gross Gross Fair Debt Securities AFS: December 31, 2020 U.S. Treasury $ 600 $ — $ — $ 600 U.S. government agencies 172 — — 172 U.S. government-sponsored entities 160 1 — 161 Residential mortgage-backed securities: Agency mortgage-backed securities 959 35 — 994 Agency collateralized mortgage obligations 1,094 31 (1) 1,124 Commercial mortgage-backed securities 361 17 — 378 States of the U.S. and political subdivisions (municipals) 32 — — 32 Other debt securities 2 — — 2 Total debt securities AFS $ 3,380 $ 84 $ (1) $ 3,463 The amortized cost and fair value of debt securities AFS for December 31, 2019 are as follows: TABLE 3.2 (in millions) Amortized Gross Gross Fair Debt Securities AFS: December 31, 2019 U.S. government agencies $ 152 $ — $ (1) $ 151 U.S. government-sponsored entities 225 1 — 226 Residential mortgage-backed securities: Agency mortgage-backed securities 1,310 7 (3) 1,314 Agency collateralized mortgage obligations 1,234 10 (4) 1,240 Commercial mortgage-backed securities 341 6 (2) 345 States of the U.S. and political subdivisions (municipals) 11 — — 11 Other debt securities 2 — — 2 Total debt securities AFS $ 3,275 $ 24 $ (10) $ 3,289
Schedule of Amortized Cost and Fair Value of Securities Held to Maturity	TABLE 3.3 (in millions) Amortized Gross Gross Fair Debt Securities HTM: December 31, 2020 U.S. Treasury $ 1 $ — $ — $ 1 U.S. government agencies 1 — — 1 U.S. government-sponsored entities 120 1 — 121 Residential mortgage-backed securities: Agency mortgage-backed securities 769 29 — 798 Agency collateralized mortgage obligations 562 17 — 579 Commercial mortgage-backed securities 307 10 — 317 States of the U.S. and political subdivisions (municipals) 1,108 48 — 1,156 Total debt securities HTM $ 2,868 $ 105 $ — $ 2,973 The amortized cost and fair value of HTM debt securities for December 31, 2019 are as follows: TABLE 3.4 (in millions) Amortized Gross Gross Fair Debt Securities HTM: December 31, 2019 U.S. Treasury $ 1 $ — $ — $ 1 U.S. government agencies 1 — — 1 U.S. government-sponsored entities 175 — — 175 Residential mortgage-backed securities: Agency mortgage-backed securities 949 8 (2) 955 Agency collateralized mortgage obligations 721 5 (6) 720 Commercial mortgage-backed securities 308 3 (2) 309 States of the U.S. and political subdivisions (municipals) 1,120 26 (2) 1,144 Total debt securities HTM $ 3,275 $ 42 $ (12) $ 3,305
Amortized Cost and Fair Value of Securities, by Contractual Maturities	As of December 31, 2020, the amortized cost and fair value of debt securities, by contractual maturities, were as follows: TABLE 3.5 Available for Sale Held to Maturity (in millions) Amortized Fair Amortized Fair Due in one year or less $ 642 $ 642 $ 122 $ 123 Due after one year but within five years 113 114 20 20 Due after five years but within ten years 124 125 151 155 Due after ten years 87 86 937 981 966 967 1,230 1,279 Residential mortgage-backed securities: Agency mortgage-backed securities 959 994 769 798 Agency collateralized mortgage obligations 1,094 1,124 562 579 Commercial mortgage-backed securities 361 378 307 317 Total debt securities $ 3,380 $ 3,463 $ 2,868 $ 2,973
Schedule of Securities Pledged as Collateral	Following is information relating to securities pledged: TABLE 3.6 December 31 2020 2019 (dollars in millions) Securities pledged (carrying value): To secure public deposits, trust deposits and for other purposes as required by law $ 5,384 $ 4,494 As collateral for short-term borrowings 402 285 Securities pledged as a percent of total securities 91.4 % 72.8 %
Summaries of Fair Values and Unrealized Losses of Securities, Segregated by Length of Impairment	Following are summaries of the fair values of AFS debt securities in an unrealized loss position for which an ACL has not been recorded, segregated by security type and length of continuous loss position: TABLE 3.7 Less than 12 Months 12 Months or More Total (dollars in millions) # Fair Unrealized # Fair Unrealized # Fair Unrealized Debt Securities AFS December 31, 2020 U.S. government agencies 1 $ 13 $ — 16 $ 69 $ — 17 $ 82 $ — U.S. government-sponsored entities 1 25 — — — — 1 25 — Residential mortgage-backed securities: Agency collateralized mortgage obligations 5 130 (1) — — — 5 130 (1) Other debt securities — — — 1 2 — 1 2 — Total 7 $ 168 $ (1) 17 $ 71 $ — 24 $ 239 $ (1) Less than 12 Months 12 Months or More Total (dollars in millions) # Fair Unrealized # Fair Unrealized # Fair Unrealized Debt Securities AFS December 31, 2019 U.S. government agencies 5 $ 48 $ — 15 $ 61 $ (1) 20 $ 109 $ (1) U.S. government-sponsored entities — — — 6 130 — 6 130 — Residential mortgage-backed securities: Agency mortgage-backed securities 13 200 (1) 24 314 (2) 37 514 (3) Agency collateralized mortgage obligations 11 323 (1) 32 205 (3) 43 528 (4) Non-agency collateralized mortgage obligations — — — — — — — — — Commercial mortgage-backed securities 3 114 (2) — — — 3 114 (2) States of the U.S. and political subdivisions (municipals) — — — — — — — — — Other debt securities — — — 1 2 — 1 2 — Total temporarily impaired debt securities AFS 32 $ 685 $ (4) 78 $ 712 $ (6) 110 $ 1,397 $ (10)

Other Securities (Tables)

Other Securities (Tables)	12 Months Ended
	Dec. 31, 2020
Banking and Thrift, Interest [Abstract]
Schedule of Other Securities	Following is a summary of non-marketable equity securities: TABLE 4.1 December 31 2020 2019 (in millions) Federal Home Loan Bank stock $ 154 $ 256 Federal Reserve Bank stock 124 123 Other non-marketable equity securities — 1 Total non-marketable equity securities $ 278 $ 380

Loans and Leases (Tables)

Loans and Leases (Tables)	12 Months Ended
	Dec. 31, 2020
Receivables [Abstract]
Summary of Loans and Leases, Net of Unearned Income	Following is a summary of total loans and leases, net of unearned income: TABLE 5.1 December 31 2020 2019 (in millions) Commercial real estate $ 9,731 $ 8,960 Commercial and industrial 7,214 5,308 Commercial leases 485 432 Other 40 21 Total commercial loans and leases 17,470 14,721 Direct installment 2,020 1,821 Residential mortgages 3,433 3,374 Indirect installment 1,218 1,922 Consumer lines of credit 1,318 1,451 Total consumer loans 7,989 8,568 Total loans and leases, net of unearned income $ 25,459 $ 23,289
Certain Information Relating to Commercial Real Estate Loans	The following table shows occupancy information relating to commercial real estate loans: TABLE 5.2 December 31 2020 2019 (dollars in millions) Commercial real estate: Percent owner-occupied 28.1 % 30.6 % Percent non-owner-occupied 71.9 69.4
Summary of Loans to Related Parties	Following is a summary of the activity for these related-party loans during 2020: TABLE 5.3 (in millions) Balance at beginning of period $ 7 New loans 2 Repayments (2) Balance at end of period $ 7
Summary of Loan, Credit Quality Indicators	We use an internal risk rating assigned to a commercial loan or lease, summarized below. TABLE 5.4 Rating Category Definition Pass in general, the condition of the borrower and the performance of the loan is satisfactory or better Special Mention in general, the condition of the borrower has deteriorated, requiring an increased level of monitoring Substandard in general, the condition of the borrower has significantly deteriorated and the performance of the loan could further deteriorate if deficiencies are not corrected Doubtful in general, the condition of the borrower has significantly deteriorated and the collection in full of both principal and interest is highly questionable or improbable
Schedule of Financing Receivables, Originated Year	The following table summarizes the designated loan rating category by loan class including term loans on an amortized cost basis by origination year: TABLE 5.5 December 31, 2020 2020 2019 2018 2017 2016 Prior Revolving Loans Amortized Cost Basis Total (in millions) COMMERCIAL Commercial Real Estate: Risk Rating: Pass $ 1,879 $ 1,854 $ 1,135 $ 927 $ 888 $ 1,911 $ 163 $ 8,757 Special Mention 9 30 80 158 70 163 4 514 Substandard 4 32 29 81 116 192 6 460 Total commercial real estate 1,892 1,916 1,244 1,166 1,074 2,266 173 9,731 Commercial and Industrial: Risk Rating: Pass 3,286 1,007 590 304 120 311 1,095 6,713 Special Mention 30 23 13 28 10 35 79 218 Substandard 8 26 65 44 6 37 97 283 Total commercial and industrial 3,324 1,056 668 376 136 383 1,271 7,214 Commercial Leases: Risk Rating: Pass 178 134 83 56 5 3 — 459 Special Mention 1 1 4 4 1 2 — 13 Substandard 7 2 2 1 1 — — 13 Total commercial leases 186 137 89 61 7 5 — 485 Other Commercial: Risk Rating: Pass — — — — — 4 35 39 Substandard — — — — — 1 — 1 Total other commercial — — — — — 5 35 40 Total commercial 5,402 3,109 2,001 1,603 1,217 2,659 1,479 17,470 December 31, 2020 2020 2019 2018 2017 2016 Prior Revolving Loans Amortized Cost Basis Total (in millions) CONSUMER Direct Installment: Current 706 337 200 143 171 442 1 2,000 Past due — 1 2 1 2 14 — 20 Total direct installment 706 338 202 144 173 456 1 2,020 Residential Mortgages: Current 1,079 707 283 378 330 603 1 3,381 Past due 1 5 7 4 6 29 — 52 Total residential mortgages 1,080 712 290 382 336 632 1 3,433 Indirect Installment: Current 372 260 332 147 67 27 — 1,205 Past due 1 3 4 2 2 1 — 13 Total indirect installment 373 263 336 149 69 28 — 1,218 Consumer Lines of Credit: Current 4 7 8 3 5 127 1,146 1,300 Past due — — — — — 15 3 18 Total consumer lines of credit 4 7 8 3 5 142 1,149 1,318 Total consumer 2,163 1,320 836 678 583 1,258 1,151 7,989 Total loans and leases $ 7,565 $ 4,429 $ 2,837 $ 2,281 $ 1,800 $ 3,917 $ 2,630 $ 25,459
Summary of Commercial Loans by Credit Quality	The following tables present the December 31, 2019 summary of our commercial loans and leases by credit quality category segregated by loans and leases originated and loans acquired, prior to the adoption of CECL: TABLE 5.6 Commercial Loan and Lease Credit Quality Categories (in millions) Pass Special Substandard Doubtful Total Originated Loans and Leases December 31, 2019 Commercial real estate $ 6,821 $ 171 $ 121 $ 1 $ 7,114 Commercial and industrial 4,768 149 144 2 5,063 Commercial leases 423 3 6 — 432 Other 20 — 1 — 21 Total originated commercial loans and leases $ 12,032 $ 323 $ 272 $ 3 $ 12,630 Loans Acquired in a Business Combination December 31, 2019 Commercial real estate $ 1,603 $ 116 $ 127 $ — $ 1,846 Commercial and industrial 201 19 25 — 245 Total commercial loans acquired in a business combination $ 1,804 $ 135 $ 152 $ — $ 2,091
Summary of Consumer Loans by Payment Status	Following is a table showing the December 31, 2019 consumer loans by payment status: TABLE 5.7 Consumer Loan Credit Quality by Payment Status (in millions) Performing Non-Performing Total Originated Loans December 31, 2019 Direct installment $ 1,745 $ 13 $ 1,758 Residential mortgages 2,978 17 2,995 Indirect installment 1,919 3 1,922 Consumer lines of credit 1,086 6 1,092 Total originated consumer loans $ 7,728 $ 39 $ 7,767 Loans Acquired in a Business Combination December 31, 2019 Direct installment $ 63 $ — $ 63 Residential mortgages 379 — 379 Consumer lines of credit 358 1 359 Total consumer loans acquired in a business combination $ 800 $ 1 $ 801
Age Analysis of Past Due Loans, by Class	The following tables provide an analysis of the aging of loans by class. TABLE 5.8 (in millions) 30-89 Days ≥ 90 Days Non- Total Current Total Non-accrual with No ACL Loans and Leases December 31, 2020 Commercial real estate $ 13 $ — $ 85 $ 98 $ 9,633 $ 9,731 $ 36 Commercial and industrial 8 — 44 52 7,162 7,214 16 Commercial leases 2 — 2 4 481 485 — Other — — 1 1 39 40 — Total commercial loans and leases 23 — 132 155 17,315 17,470 52 Direct installment 7 2 11 20 2,000 2,020 — Residential mortgages 23 11 18 52 3,381 3,433 — Indirect installment 10 1 2 13 1,205 1,218 — Consumer lines of credit 9 2 7 18 1,300 1,318 — Total consumer loans 49 16 38 103 7,886 7,989 — Total loans and leases $ 72 $ 16 $ 170 $ 258 $ 25,201 $ 25,459 $ 52 (in millions) 30-89 Days > 90 Days Non- Total Current Total Originated Loans and Leases December 31, 2019 Commercial real estate $ 10 $ — $ 26 $ 36 $ 7,078 $ 7,114 Commercial and industrial 9 — 28 37 5,026 5,063 Commercial leases 5 — 1 6 426 432 Other — — 1 1 20 21 Total commercial loans and leases 24 — 56 80 12,550 12,630 Direct installment 7 1 7 15 1,743 1,758 Residential mortgages 12 2 8 22 2,973 2,995 Indirect installment 15 1 3 19 1,903 1,922 Consumer lines of credit 5 1 3 9 1,083 1,092 Total consumer loans 39 5 21 65 7,702 7,767 Total originated loans and leases $ 63 $ 5 $ 77 $ 145 $ 20,252 $ 20,397 (in millions) 30-89 Days ≥ 90 Days Non- Total Current (Discount)/ Total Loans Acquired in a Business Combination December 31, 2019 Commercial real estate $ 12 $ 28 $ 3 $ 43 $ 1,942 $ (139) $ 1,846 Commercial and industrial 2 3 — 5 259 (19) 245 Total commercial loans 14 31 3 48 2,201 (158) 2,091 Direct installment 3 — — 3 60 — 63 Residential mortgages 8 4 — 12 382 (15) 379 Consumer lines of credit 7 2 1 10 357 (8) 359 Total consumer loans 18 6 1 25 799 (23) 801 Total loans acquired in a business combination $ 32 $ 37 $ 4 $ 73 $ 3,000 $ (181) $ 2,892 (1) Prior to the adoption of CECL on January 1, 2020, loans acquired in a business combination were considered performing upon acquisition, regardless of whether the customer was contractually delinquent, if we could reasonably estimate the timing and amount of expected cash flows on such loans. In these instances, we did not consider acquired contractually delinquent loans to be non-accrual or non-performing and continued to recognize interest income on these loans using the accretion method. After the adoption of CECL on January 1, 2020 loans acquired in a business combination are considered non-accrual or non-performing when, due to credit deterioration or other factors, we determine we are no longer able to reasonably estimate the timing and amount of expected cash flows on such loans. We do not recognize interest income on loans acquired in a business combination considered non-accrual or non-performing.
Summary of Non-Performing Assets	Following is a summary of non-performing assets: TABLE 5.9 December 31 2020 2019 (dollars in millions) Non-accrual loans $ 170 $ 81 Troubled debt restructurings — 22 Total non-performing loans 170 103 Other real estate owned 10 26 Total non-performing assets $ 180 $ 129 Asset quality ratios: Non-performing loans / total loans and leases 0.67 % 0.44 % Non-performing loans assets + 90 days past due + OREO / total loans and leases + OREO 0.77 0.73
Summary of Composition of Total TDRs	Following is a summary of the composition of total TDRs: TABLE 5.10 December 31 2020 2019 (in millions) Accruing $ 58 $ 41 Non-accrual 33 15 Total TDRs $ 91 $ 56
Summary of Troubled Debt Restructurings by Class of Loans	Following is a summary of TDR loans, by class, for loans that were modified during the periods indicated: TABLE 5.11 Year Ended December 31 2020 2019 (dollars in millions) Number Pre-Modification Post- Number Pre-Modification Post- Commercial real estate 30 $ 18 $ 8 20 $ 5 $ 5 Commercial and industrial 19 2 1 23 5 3 Other 1 — — — — — Total commercial loans 50 20 9 43 10 8 Direct installment 68 4 4 65 3 3 Residential mortgages 24 3 3 18 3 3 Consumer lines of credit 45 2 1 27 2 1 Total consumer loans 137 9 8 110 8 7 Total 187 $ 29 $ 17 153 $ 18 $ 15
Summary of Troubled Debt Restructurings by Class of Loans and Leases, Payment Default	Following is a summary of TDRs, by class, for which there was a payment default, excluding loans that have been paid off and/or sold. Default occurs when a loan is 90 days or more past due and is within 12 months of restructuring. TABLE 5.12 Year Ended December 31 2020 (dollars in millions) Number Recorded Commercial real estate 8 $ 3 Commercial and industrial 2 — Total commercial loans 10 3 Direct installment 12 — Residential mortgages 4 — Consumer lines of credit 4 — Total consumer loans 20 — Total 30 $ 3
Summary of Originated Troubled Debt Restructurings by Class of Loans and Leases, Payment Default	Following is a summary of originated TDRs, by class, for which there was a payment default, excluding loans that have been paid off and/or sold. TABLE 5.13 Year Ended December 31 2019 (dollars in millions) Number Recorded Commercial real estate 5 $ 1 Commercial and industrial 1 — Total commercial loans 6 1 Direct installment 5 — Residential mortgages 2 — Consumer lines of credit 1 — Total consumer loans 8 — Total 14 $ 1

Allowance for Credit Losses o_2

Allowance for Credit Losses on Loans and Leases (Tables)	12 Months Ended
	Dec. 31, 2020
Receivables [Abstract]
Summary of Changes in Allowance for Credit Losses by Loan and Lease Class	Following is a summary of changes in the ACL, by loan and lease class: TABLE 6.1 (in millions) Balance at Charge- Recoveries Net Provision ASC 326 Adoption Impact Initial ACL on PCD Loans Balance at Year Ended December 31, 2020 Commercial real estate $ 60 $ (31) $ 7 $ (24) $ 67 $ 38 $ 40 $ 181 Commercial and industrial 53 (32) 7 (25) 41 8 4 81 Commercial leases 11 (1) — (1) 7 — — 17 Other 9 (4) 1 (3) 4 (9) — 1 Total commercial loans and leases 133 (68) 15 (53) 119 37 44 280 Direct installment 13 (1) 1 — 2 10 1 26 Residential mortgages 22 (2) 1 (1) 3 6 4 34 Indirect installment 19 (8) 4 (4) (6) 2 — 11 Consumer lines of credit 9 (2) — (2) 4 — 1 12 Total consumer loans 63 (13) 6 (7) 3 18 6 83 Total allowance for credit losses on loans and leases $ 196 $ (81) $ 21 $ (60) $ 122 $ 55 $ 50 $ 363 Allowance for unfunded loan commitments 3 — — — 1 10 — 14 Total allowance for credit losses on loans and leases and allowance for unfunded loan commitments $ 199 $ (81) $ 21 $ (60) $ 123 $ 65 $ 50 $ 377 Following is a summary of changes in the AULC by portfolio segment: TABLE 6.2 Year Ended December 31 2020 (in millions) Balance at beginning of period $ 3 Provision for unfunded loan commitments and letters of credit: Commercial portfolio 1 Consumer portfolio — ASC 326 adoption impact: Commercial portfolio 8 Consumer portfolio 2 Balance at end of period $ 14 Following is a summary of changes in the ACL, by loan and lease class: TABLE 6.3 (in millions) Balance at Charge- Recoveries Net Provision Balance at Year Ended December 31, 2019 Commercial real estate $ 55 $ (4) $ 4 $ — $ 5 $ 60 Commercial and industrial 49 (10) 4 (6) 10 53 Commercial leases 8 — — — 3 11 Other 2 (3) — (3) 3 2 Total commercial loans and leases 114 (17) 8 (9) 21 126 Direct installment 14 (1) — (1) — 13 Residential mortgages 20 (2) — (2) 4 22 Indirect installment 15 (11) 4 (7) 11 19 Consumer lines of credit 10 (2) — (2) 1 9 Total consumer loans 59 (16) 4 (12) 16 63 Total allowance on originated loans and leases 173 (33) 12 (21) 37 189 Loans acquired in a business combination 7 (9) 2 (7) 7 7 Total allowance for credit losses $ 180 $ (42) $ 14 $ (28) $ 44 $ 196 Year Ended December 31, 2018 Commercial real estate $ 50 $ (7) $ 3 $ (4) $ 9 $ 55 Commercial and industrial 52 (20) 2 (18) 15 49 Commercial leases 5 (3) — (3) 6 8 Other 2 (4) — (4) 4 2 Total commercial loans and leases 109 (34) 5 (29) 34 114 Direct installment 21 (17) 2 (15) 8 14 Residential mortgages 16 — — — 4 20 Indirect installment 12 (9) 4 (5) 8 15 Consumer lines of credit 10 (3) — (3) 3 10 Total consumer loans 59 (29) 6 (23) 23 59 Total allowance on originated loans and leases 168 (63) 11 (52) 57 173 Loans acquired in a business combination 7 (7) 3 (4) 4 7 Total allowance for credit losses $ 175 $ (70) $ 14 $ (56) $ 61 $ 180
Summary of Individual and Collective Allowance for Credit Losses and Loan and Lease Balances by Class	Following is a summary of the individual and collective ACL and corresponding loan and lease balances by class: TABLE 6.4 Allowance for Credit Losses Loans and Leases Outstanding (in millions) Individually Collectively Loans and Individually Collectively December 31, 2019 Commercial real estate $ 2 $ 58 $ 7,114 $ 13 $ 7,101 Commercial and industrial 2 51 5,063 17 5,046 Commercial leases — 11 432 — 432 Other — 2 21 — 21 Total commercial loans and leases 4 122 12,630 30 12,600 Direct installment — 13 1,758 — 1,758 Residential mortgages — 22 2,995 — 2,995 Indirect installment — 19 1,922 — 1,922 Consumer lines of credit — 9 1,092 — 1,092 Total consumer loans — 63 7,767 — 7,767 Total $ 4 $ 185 $ 20,397 $ 30 $ 20,367 The above table excludes loans acquired in a business combination that were pooled into groups of loans for evaluating impairment.

Loan Servicing (Tables)

Loan Servicing (Tables)	12 Months Ended
	Dec. 31, 2020
Mortgage Servicing Rights
Servicing Assets at Fair Value [Line Items]
Servicing Asset at Amortized Cost	The unpaid principal balance of mortgage loans serviced for others is listed below: TABLE 7.1 December 31 2020 2019 (in millions) Mortgage loans sold with servicing retained $ 4,653 $ 4,686 The following table summarizes activity relating to mortgage loans sold with servicing retained: TABLE 7.2 Year Ended December 31 2020 2019 2018 (in millions) Mortgage loans sold with servicing retained $ 1,636 $ 1,381 $ 1,060 Pretax gains resulting from above loan sales (1) 70 32 19 Mortgage servicing fees (1) 12 11 9 (1) Recorded in mortgage banking operations on the Consolidated Statements of Income. Following is a summary activity relating to MSRs: TABLE 7.3 Year Ended December 31 2020 2019 2018 (in millions) Balance at beginning of period $ 42.6 $ 36.8 $ 29.1 Additions 16.0 14.3 12.5 Payoffs and curtailments (14.8) (5.0) (1.8) (Impairment) charge / recovery (5.8) (1.0) (0.5) Amortization (2.4) (2.5) (2.5) Balance at end of period $ 35.6 $ 42.6 $ 36.8 Fair value, beginning of period $ 45.2 $ 41.1 $ 32.4 Fair value, end of period 35.6 45.2 41.1
Schedule of Assumptions for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement	Following is a summary of the sensitivity of the fair value of MSRs to changes in key assumptions: TABLE 7.4 December 31 2020 2019 (dollars in millions) Weighted average life (months) 66.6 78.9 Constant prepayment rate (annualized) 13.4 % 10.6 % Discount rate 9.5 % 9.7 % Effect on fair value due to change in interest rates: +0.25% $ 2 $ 3 +0.50% 4 5 -0.25% (2) (3) -0.50% (3) (5)
SBA-Guaranteed Loan Servicing
Servicing Assets at Fair Value [Line Items]
Servicing Asset at Amortized Cost	The unpaid principal balance of SBA-guaranteed loans serviced for investors was as follows: TABLE 7.5 December 31 2020 2019 (in millions) SBA loans sold to investors with servicing retained $ 217 $ 225 The following table summarizes activity relating to SBA loans sold with servicing retained: TABLE 7.6 Year Ended December 31 2020 2019 2018 (in millions) SBA loans sold with servicing retained $ 33 $ 23 $ 41 Pretax gains resulting from above loan sales (1) 3 2 4 SBA servicing fees (1) 2 2 3 (1) Recorded in non-interest income. Following is a summary of the activity in SBA servicing rights: TABLE 7.7 Year Ended December 31 2020 2019 2018 (in millions) Balance at beginning of period $ 3 $ 4 $ 5 Additions 1 — 1 Payoffs, curtailments and amortization (1) (1) (1) Impairment charge — — (1) Balance at end of period $ 3 $ 3 $ 4 Fair value, beginning of period $ 3 $ 4 $ 5 Fair value, end of period 3 3 4
Schedule of Assumptions for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement	Following is a summary of key assumptions and the sensitivity of the SBA servicing rights to changes in these assumptions. The declines in fair values were immaterial in the scenarios presented. TABLE 7.8 December 31 2020 2019 (dollars in millions) Weighted average life (months) 38 42 Constant prepayment rate 17.8 % 16.8 % Discount rate 13.2 16.2 Decline in fair value due to change in interest rates: 1% adverse change $ (0.1) $ (0.1) 2% adverse change (0.1) (0.1) Decline in fair value due to change in constant prepayment rates: 10% adverse change (0.1) (0.1) 20% adverse change (0.1) (0.3)

Premises and Equipment (Tables)

Premises and Equipment (Tables)	12 Months Ended
	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Summary of Premises and Equipment	Following is a summary of premises and equipment: TABLE 8.1 December 31 2020 2019 (in millions) Land $ 57 $ 62 Premises 231 233 Equipment 311 276 599 571 Accumulated depreciation (267) (238) Total premises and equipment, net $ 332 $ 333
Depreciation Expense for Premises and Equipment	Depreciation expense for premises and equipment is presented in the following table: TABLE 8.2 December 31 2020 2019 2018 (in millions) Depreciation expense for premises and equipment $ 43 $ 42 $ 39

Goodwill and Other Intangible_2

Goodwill and Other Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Rollforward of Goodwill	The following table shows a rollforward of goodwill by line of business: TABLE 9.1 (in millions) Community Wealth Insurance Total Balance at January 1, 2019 $ 2,231 $ 8 $ 16 $ 2,255 Goodwill (deductions) additions — — 7 7 Balance at December 31, 2019 2,231 8 23 2,262 Goodwill (deductions) additions — — — — Balance at December 31, 2020 $ 2,231 $ 8 $ 23 $ 2,262
Summary of Core Deposit Intangibles, Customer Renewal Lists and Mortgage Servicing Rights	The following table shows a summary of core deposit intangibles and customer renewal lists: TABLE 9.2 (in millions) Core Customer Total December 31, 2020 Gross carrying amount $ 197 $ 18 $ 215 Accumulated amortization (149) (12) (161) Net carrying amount $ 48 $ 6 $ 54 December 31, 2019 Gross carrying amount $ 196 $ 18 $ 214 Accumulated amortization (136) (11) (147) Net carrying amount $ 60 $ 7 $ 67
Schedule of Amortization Expense Recognized	The following table summarizes amortization expense recognized: TABLE 9.3 December 31 2020 2019 2018 (in millions) Amortization expense $ 13 $ 14 $ 16
Schedule of Expected Amortization Expenses on Finite-Lived Intangible Assets	Following is a summary of the expected amortization expense on finite-lived intangible assets, assuming no new additions, for each of the five years following December 31, 2020: TABLE 9.4 (in millions) 2021 $ 12 2022 10 2023 10 2024 8 2025 7 Total $ 47

Operating Leases (Tables)

Operating Leases (Tables)	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Lease, Cost	The components of lease expense were as follows: TABLE 10.1 Twelve Months Ended (dollars in millions) 2020 2019 Operating lease cost $ 27 $ 27 Short-term lease cost 1 1 Variable lease cost 3 4 Total lease cost $ 31 $ 32
Leases, Other Information	Other information related to leases is as follows: TABLE 10.2 Twelve Months Ended (dollars in millions) 2020 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 26 $ 26 Right-of-use assets obtained in exchange for lease obligations: Operating leases 20 25 Weighted average remaining lease term (years): Operating leases 9.45 9.61 Weighted average discount rate: Operating leases 2.6 % 3.0 %
Lessor, Operating Lease, Payments to be Received, Maturity	Maturities of operating lease liabilities were as follows: TABLE 10.3 (in millions) December 31, 2021 $ 25 2022 21 2023 17 2024 15 2025 12 Later years 64 Total lease payments 154 Less: imputed interest (20) Present value of lease liabilities $ 134

Variable Interest Entities (Tab

Variable Interest Entities (Tables)	12 Months Ended
	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Variable Interest Entities, Assets and Liabilities	The following tables provide a summary of the assets and liabilities included in our Consolidated Financial Statements, as well as the maximum exposure to losses, associated with our interests related to VIEs for which we hold an interest, but are not the primary beneficiary, at December 31, 2020 and December 31, 2019. TABLE 11.1 (in millions) Total Assets Total Liabilities Maximum Exposure to Loss December 31, 2020 Trust preferred securities (1) $ 1 $ 66 $ — Affordable housing tax credit partnerships 119 45 119 Other investments 26 8 26 Total $ 146 $ 119 $ 145 December 31, 2019 Trust preferred securities (1) $ 1 $ 66 $ — Affordable housing tax credit partnerships 120 60 120 Other investments 33 10 33 Total $ 154 $ 136 $ 153 (1) Represents our investment in unconsolidated subsidiaries.
Low Income Housing Tax Credits, Balances Of Affordable Housing Tax Credit Investments And Related Unfunded Commitments	The following table presents the balances of our affordable housing tax credit investments and related unfunded commitments: TABLE 11.2 December 31 2020 2019 (in millions) Proportional amortization method investments included in other assets $ 71 $ 55 Equity method investments included in other assets 3 5 Total LIHTC investments included in other assets $ 74 $ 60 Unfunded LIHTC commitments $ 45 $ 60
Low Income Housing Tax Credits, Income Statement Effect	The following table summarizes the impact of these LIHTC investments on specific line items of our Consolidated Statements of Income: TABLE 11.3 Year Ended December 31 (in millions) 2020 2019 2018 Non-interest income: Amortization of tax credit investments under equity method, net of tax benefit $ 1 $ 1 $ 2 Provision for income taxes: Amortization of LIHTC investments under proportional method $ 11 $ 8 $ 5 Low-income housing tax credits (12) (9) (6) Other tax benefits related to tax credit investments (2) (2) (1) Total provision for income taxes $ (3) $ (3) $ (2)

Deposits (Tables)

Deposits (Tables)	12 Months Ended
	Dec. 31, 2020
Deposits [Abstract]
Summary of Deposits	Following is a summary of deposits: TABLE 12.1 December 31 2020 2019 (in millions) Non-interest-bearing demand $ 9,042 $ 6,384 Interest-bearing demand 13,157 11,049 Savings 3,261 2,625 Certificates and other time deposits: Less than $100,000 1,895 2,262 $100,000 through $250,000 1,173 1,494 Greater than $250,000 594 972 Total certificates and other time deposits 3,662 4,728 Total deposits $ 29,122 $ 24,786
Summary of Scheduled Maturities of Certificates and Other Time Deposits	Following is a summary of the scheduled maturities of certificates and other time deposits for the years following December 31, 2020: TABLE 12.2 (in millions) 2021 $ 2,464 2022 683 2023 236 2024 124 2025 99 Later years 56 Total $ 3,662

Short-Term Borrowings (Tables)

Short-Term Borrowings (Tables)	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Summary of Short-Term Borrowings	Following is a summary of short-term borrowings: TABLE 13.1 December 31 2020 2019 (in millions) Securities sold under repurchase agreements $ 403 $ 278 Federal Home Loan Bank advances 1,280 2,255 Federal funds purchased — 575 Subordinated notes 121 108 Total short-term borrowings $ 1,804 $ 3,216
Schedule of Weighted Average Interest Rates on Short-Term Borrowings	The following represents weighted average interest rates on short-term borrowings: TABLE 13.2 December 31 2020 2019 2018 Year-to-date average 1.53 % 2.24 % 1.89 % Period-end 1.57 1.76 2.49

Long-Term Borrowings (Tables)

Long-Term Borrowings (Tables)	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Summary of Long-Term Borrowings	Following is a summary of long-term borrowings: TABLE 14.1 December 31 2020 2019 (in millions) Federal Home Loan Bank advances $ 400 $ 935 Senior notes 299 — Subordinated notes 81 90 Junior subordinated debt 66 66 Other subordinated debt 249 249 Total long-term borrowings $ 1,095 $ 1,340
Scheduled Annual Maturities for Long-Term Borrowings	Scheduled annual maturities for the long-term borrowings for the years following December 31, 2020 are as follows: TABLE 14.2 (in millions) 2021 $ 427 2022 16 2023 334 2024 1 2025 104 Later years 213 Total $ 1,095
Schedule of Weighted Average Interest Rate on Subordinated Notes	The weighted average interest rate on the subordinated notes are presented in the following table: TABLE 14.3 December 31 2020 2019 2018 Subordinated notes weighted average interest rate 3.23 % 3.33 % 3.08 %
Schedule of Junior Subordinated Debt Trusts	The following table provides information relating to the Trusts as of December 31, 2020: TABLE 14.4 (dollars in millions) Trust Common Junior Stated Interest Rate Reset Factor F.N.B. Statutory Trust II $ 22 $ 1 $ 22 6/15/2036 1.87 % LIBOR + 165 basis points (bps) Yadkin Valley Statutory Trust I 25 1 22 12/15/2037 1.54 % LIBOR + 132 bps FNB Financial Services Capital Trust I 25 1 22 9/30/2035 1.70 % LIBOR + 146 bps Total $ 72 $ 3 $ 66
Schedule of Other Subordinated Debt	The following table provides information relating to our senior debt and other subordinated debt as of December 31, 2020. These debt issuances are fixed-rate, with the exception of the debt offering in 2019, which is fixed-to-floating rate after February 14, 2024, at which time the floating rate will be LIBOR plus 240 basis points, or an alternative rate that may replace LIBOR, as specified in the prospectus for this offering. The subordinated notes are eligible for treatment as tier 2 capital for regulatory capital purposes. TABLE 14.5 (dollars in millions) Aggregate Principal Amount Issued Net Proceeds (2) Carrying Value Stated Maturity Date Interest 2.20% Senior Notes due February 24, 2023 $ 300 $ 298 $ 299 2/24/2023 2.20 % 4.95% Fixed-To-Floating Rate Subordinated Notes due 2029 120 118 119 2/14/2029 4.95 % 4.875% Subordinated Notes due 2025 100 98 99 10/2/2025 4.875 % 7.625% Subordinated Notes due August 12, 2023 (1) 38 46 31 8/12/2023 7.625 % Total $ 558 $ 560 $ 548 (1) Assumed from YDKN and adjusted to fair value at the time of acquisition. (2) After deducting underwriting discounts and commissions and offering costs. For the debt assumed from YDKN, this is the fair value of the debt at the time of the acquisition.

Derivative Instruments and He_2

Derivative Instruments and Hedging Activities (Tables)	12 Months Ended
	Dec. 31, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Notional Amounts and Gross Fair Values of Derivative Assets and Derivative Liabilities	The following table presents notional amounts and gross fair values of our derivative assets and derivative liabilities which are not offset in the Consolidated Balance Sheets: TABLE 15.1 December 31 2020 2019 Notional Fair Value Notional Fair Value (in millions) Asset Liability Asset Liability Gross Derivatives Subject to master netting arrangements: Interest rate contracts – designated $ 1,430 $ 3 $ — $ 1,655 $ 1 $ — Interest rate swaps – not designated 4,791 — 37 3,640 — 23 Total subject to master netting arrangements 6,221 3 37 5,295 1 23 Not subject to master netting arrangements: Interest rate swaps – not designated 4,791 349 — 3,640 149 1 Interest rate lock commitments – not designated 531 24 — 163 3 — Forward delivery commitments – not designated 500 — 2 195 1 1 Credit risk contracts – not designated 437 — 1 265 — — Total not subject to master netting arrangements 6,259 373 3 4,263 153 2 Total $ 12,480 $ 376 $ 40 $ 9,558 $ 154 $ 25
Summary of Amounts Reclassified from Accumulated Other Comprehensive Income (AOCI)	The following table shows amounts reclassified from AOCI: TABLE 15.2 Amount of Gain (Loss) Recognized in OCI on Derivatives Location of Gain (Loss) Reclassified from AOCI into Income Amount of Gain (Loss) Reclassified from AOCI into Income Year Ended Year Ended (in millions) 2020 2019 2018 2020 2019 2018 Derivatives in cash flow hedging relationships: Interest rate contracts $ (51) $ (22) $ (3) Interest income (expense) $ (14) $ 2 $ 2 Other income (9) — —
Schedule of Cash Flow Hedges Included in Accumulated Other Comprehensive Income (Loss)	The following table represents gains (losses) recognized in the Consolidated Statements of Income on cash flow hedging relationships: TABLE 15.3 Year Ended December 31, 2020 2019 2018 (in millions) Interest Income - Loans and Leases Interest Expense - Short-Term Borrowings Interest Income - Loans and Leases Interest Expense - Short-Term Borrowings Interest Income - Loans and Leases Interest Expense - Short-Term Borrowings Total amounts of income and expense line items presented in the Consolidated Statements of Income (the effects of cash flow hedges are included in these line items) $ 990 $ 38 $ 1,085 $ 80 $ 1,022 $ 75 The effects of cash flow hedging: Gain (loss) on cash flow hedging Interest rate contracts: Amount of gain (loss) reclassified from AOCI into net income (1) (7) (16) (1) 3 (1) 3 Amount of gain (loss) reclassified — — — — — — (1) For 2020, the amount of loss reclassified from AOCI into net income relating to interest income on loans and leases included an $8.9 million loss reflected in other non-interest income.
Schedule of Derivative Financial Instruments on the Consolidated Statements of Income	The following table presents the effect of certain derivative financial instruments on the Consolidated Statements of Income: TABLE 15.4 Year Ended December 31, (in millions) Consolidated Statements of Income Location 2020 2019 2018 Interest rate swaps Non-interest income - other $ — $ — $ 1 Interest rate lock commitments Mortgage banking operations — — — Forward delivery contracts Mortgage banking operations (2) (1) 1 Credit risk contracts Non-interest income - other — — —
Schedule of Offsetting Assets and Liabilities	The following table presents a reconciliation of the net amounts of derivative assets and derivative liabilities presented in the Consolidated Balance Sheets to the net amounts that would result in the event of offset: TABLE 15.5 Amount Not Offset in the (in millions) Net Amount Financial Cash Net December 31, 2020 Derivative Assets Interest rate contracts: Designated $ 3 $ — $ 3 $ — Total $ 3 $ — $ 3 $ — Derivative Liabilities Interest rate contracts: Not designated $ 37 $ — $ 37 $ — Total $ 37 $ — $ 37 $ — December 31, 2019 Derivative Assets Interest rate contracts: Designated $ 1 $ 1 $ — $ — Total $ 1 $ 1 $ — $ — Derivative Liabilities Interest rate contracts: Not designated $ 23 $ 23 $ — $ — Total $ 23 $ 23 $ — $ —

Commitments, Credit Risk and _2

Commitments, Credit Risk and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Summary of Off-Balance Sheet Credit Risk Information	Following is a summary of off-balance sheet credit risk information: TABLE 16.1 December 31 2020 2019 (in millions) Commitments to extend credit $ 9,285 $ 8,089 Standby letters of credit 158 150

Stock Incentive Plans (Tables)

Stock Incentive Plans (Tables)	12 Months Ended
	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
Summary of Activity Relating to Restricted Stock Units	The following table summarizes the activity relating to restricted stock units during the periods indicated: TABLE 17.1 2020 2019 2018 Units Weighted Units Weighted Units Weighted Unvested units outstanding at beginning of year 2,858,357 $ 12.56 2,556,174 $ 13.51 1,975,862 $ 13.64 Granted 2,004,895 6.95 1,182,197 10.94 962,799 13.21 Net adjustment due to performance 47,290 13.00 — — — — Vested (613,581) 14.41 (655,208) 13.15 (258,031) 13.19 Forfeited/expired (203,058) 12.54 (332,814) 12.72 (214,743) 13.39 Dividend reinvestment 228,212 8.14 108,008 11.84 90,287 12.61 Unvested units outstanding at end of year 4,322,115 9.46 2,858,357 12.56 2,556,174 13.51
Schedule of Certain Information Related to Restricted Stock Units	The following table provides certain information related to restricted stock units: TABLE 17.2 Year Ended December 31 2020 2019 2018 (in millions) Stock-based compensation expense $ 16 $ 12 $ 10 Tax benefit related to stock-based compensation expense 3 2 2 Fair value of units vested 5 7 3
Components of Restricted Stock Units	The components of the restricted stock units as of December 31, 2020 are as follows: TABLE 17.3 (dollars in millions) Service- Performance- Total Unvested restricted stock units 2,983,059 1,339,056 4,322,115 Unrecognized compensation expense $ 9 $ 2 $ 11 Intrinsic value $ 28 $ 13 $ 41 Weighted average remaining life (in years) 1.72 1.16 1.54
Summary of Activity Related to Stock Options Units	The following table summarizes the activity relating to stock options during the periods indicated: TABLE 17.4 2020 Weighted 2019 Weighted 2018 Weighted Options outstanding at beginning of year 246,084 $ 8.14 458,354 $ 7.99 722,650 $ 7.96 Exercised (33,945) 5.74 (183,566) 7.86 (253,899) 7.77 Forfeited/expired (16,053) 7.38 (28,704) 7.65 (10,397) 11.98 Options outstanding and exercisable at end of year 196,086 8.61 246,084 8.14 458,354 7.99
Summary of Stock Options Outstanding	The following table summarizes information about stock options outstanding at December 31, 2020: TABLE 17.5 Range of Exercise Prices Options Weighted Average Weighted Average $3.57 - $5.36 26,216 0.72 $ 4.93 $5.37 - $8.05 39,667 2.12 6.91 $8.06 - $11.37 130,203 3.80 9.87 196,086

Retirement Plans (Tables)

Retirement Plans (Tables)	12 Months Ended
	Dec. 31, 2020
Retirement Benefits [Abstract]
Schedule of Accumulated Benefit Obligation, Change in Benefit Obligation, Change in Plan Assets, Plans' Funded Status and Amount Included in Consolidated Balance Sheets	The following tables provide information relating to the accumulated benefit obligation, change in benefit obligation, change in plan assets, the plans’ funded status and the amount included in the Consolidated Balance Sheets for the qualified and non-qualified plans described above (collectively, the Plans): TABLE 18.1 December 31 2020 2019 Qualified Non-Qualified Total Qualified Non-Qualified Total (in millions) Accumulated benefit obligation $ 167 $ 20 $ 187 $ 156 $ 19 $ 175 Projected benefit obligation at beginning of year $ 156 $ 19 $ 175 $ 145 $ 18 $ 163 Interest cost 5 1 6 6 1 7 Actuarial loss (gain) 15 2 17 15 2 17 Benefits paid (9) (2) (11) (10) (2) (12) Projected benefit obligation at end of year $ 167 $ 20 $ 187 $ 156 $ 19 $ 175 Fair value of plan assets at beginning of year $ 173 $ — $ 173 $ 150 $ — $ 150 Actual return on plan assets 20 — 20 28 — 28 Corporation contribution 5 2 7 5 2 7 Benefits paid (9) (2) (11) (10) (2) (12) Fair value of plan assets at end of year $ 189 $ — $ 189 $ 173 $ — $ 173 Funded status of plans $ 22 $ (20) $ 2 $ 17 $ (19) $ (2)
Schedule of Actuarial Assumptions Used in Determination of Projected Benefit Obligation	Actuarial assumptions used in the determination of the projected benefit obligation in the Plans are as follows: TABLE 18.2 Assumptions at December 31 2020 2019 Weighted average discount rate 2.31 % 3.17 % Rates of average increase in compensation levels 3.50 3.50
Schedule of Net Periodic Pension Cost and Other Comprehensive Income	The net periodic pension cost and OCI for the Plans included the following components: TABLE 18.3 Year Ended December 31 2020 2019 2018 (in millions) Interest cost $ 6 $ 7 $ 6 Expected return on plan assets (13) (11) (11) Actuarial loss amortization 3 2 2 Total pension income (4) (2) (3) Other changes in plan assets and benefit obligations recognized in other comprehensive income: Current year actuarial loss 10 1 6 Amortization of actuarial loss (3) (2) (2) Total amount recognized in other comprehensive income 7 (1) 4 Total amount recognized in net periodic benefit cost and other comprehensive income $ 3 $ (3) $ 1
Schedule of Actuarial Assumptions Used in Determination of Net Periodic Pension Cost	The plans have an actuarial measurement date of December 31. Actuarial assumptions used in the determination of the net periodic pension cost in the Plans are as follows: TABLE 18.4 Assumptions for the Year Ended December 31 2020 2019 2018 Weighted average discount rate 3.17 % 4.16 % 4.19 % Rates of increase in compensation levels 3.50 3.50 3.50 Expected long-term rate of return on assets 7.25 7.25 7.25
Schedule of Estimated Future Cash Flows	The following table provides information regarding estimated future cash flows relating to the Plans at December 31, 2020: TABLE 18.5 (in millions) Expected employer contributions: 2021 $ 1 Expected benefit payments: 2021 10 2022 10 2023 11 2024 11 2025 11 2026 – 2030 52
Schedule of Contribution Expense	Our contribution expense is presented in the following table: TABLE 18.6 Year Ended December 31 2020 2019 2018 (in millions) 401(k) contribution expense $ 17 $ 15 $ 15
Schedule of Asset Allocations for Pension Plans	The following table presents asset allocations for our pension plans as of December 31, 2020 and 2019, and the target allocation for 2021, by asset category: TABLE 18.7 Target Percentage of Plan Assets December 31 2021 2020 2019 Asset Category Equity securities 45 - 65 63 % 60 % Debt securities 30 - 50 36 37 Cash equivalents 0 - 10 1 3
Schedule of Fair Values of Pension Plan Assets by Asset Category	The fair values of our pension plan assets by asset category are as follows: TABLE 18.8 (in millions) Level 1 Level 2 Level 3 Total December 31, 2020 Asset Class Cash $ 2 $ — $ — $ 2 Equity securities: F.N.B. Corporation 4 — — 4 Other large-cap U.S. financial services companies 3 — — 3 Other large-cap U.S. companies 60 — — 60 Other equity 1 — — 1 Mutual fund equity investments: U.S. equity index funds: U.S. large-cap equity index funds — — — — U.S. small-cap equity index funds 5 — — 5 U.S. mid-cap equity index funds 6 — — 6 Non-U.S. equities growth fund 16 — — 16 U.S. equity funds: U.S. mid-cap 13 — — 13 U.S. small-cap 5 — — 5 Other 5 — — 5 Fixed income securities: U.S. government agencies — 45 — 45 Corporate bonds — — — — Fixed income mutual funds: U.S. investment-grade fixed income securities 24 — — 24 Total $ 144 $ 45 $ — $ 189 (in millions) Level 1 Level 2 Level 3 Total December 31, 2019 Asset Class Cash $ 5 $ — $ — $ 5 Equity securities: F.N.B. Corporation 6 — — 6 Other large-cap U.S. financial services companies 4 — — 4 Other large-cap U.S. companies 54 — — 54 Other equity 1 — — 1 Mutual fund equity investments: U.S. equity index funds: U.S. large-cap equity index funds 1 — — 1 U.S. small-cap equity index funds 3 — — 3 U.S. mid-cap equity index funds 5 — — 5 Non-U.S. equities growth fund 9 — — 9 U.S. equity funds: U.S. mid-cap 12 — — 12 U.S. small-cap 4 — — 4 Other 5 — — 5 Fixed income securities: U.S. government agencies — 51 — 51 Corporate bonds — 1 — 1 Fixed income mutual funds: U.S. investment-grade fixed income securities 12 — — 12 Total $ 121 $ 52 $ — $ 173

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Summary of Income Tax Expense Allocated Based on Separate Tax Return Basis	Federal and state income tax expense consist of the following: TABLE 19.1 Year Ended December 31 2020 2019 2018 (in millions) Current income taxes: Federal taxes $ 71 $ 47 $ 41 State taxes 5 4 6 Total current income taxes 76 51 47 Deferred income taxes: Federal taxes (20) 30 32 State taxes 1 3 — Total deferred income taxes (19) 33 32 Total income taxes $ 57 $ 84 $ 79
Summary of Reconciliation Between the Statutory Tax Rate and Actual Effective Tax Rate	The following table provides a reconciliation between the statutory tax rate and the actual effective tax rate: TABLE 19.2 Year Ended December 31 2020 2019 2018 Statutory federal tax rate 21.0 % 21.0 % 21.0 % State taxes, net of federal benefit 1.6 1.1 1.1 Tax-exempt interest (2.8) (2.2) (2.1) Cash surrender value on BOLI (0.8) (0.5) (0.5) Tax credits (6.3) (4.2) (2.8) Affordable housing cost amortization, net of tax benefits 2.5 1.4 0.7 Tax Cuts and Jobs Act revaluation of net deferred tax assets — — (0.4) Other items 1.5 1.1 0.6 Effective tax rate 16.7 % 17.7 % 17.6 %
Summary of Deferred Tax Assets and Liabilities from Tax Effects of Temporary Differences	The following table presents the tax effects of significant temporary differences that give rise to federal and state DTAs and DTLs: TABLE 19.3 December 31 2020 2019 (in millions) Deferred tax assets: Allowance for credit losses $ 80 $ 43 Discounts on loans acquired in a business combination 16 41 Net operating loss/tax credit carryforwards 38 38 Deferred compensation 12 11 Securities impairments 1 1 Pension and other defined benefit plans 2 3 Lease liability 30 29 Net unrealized securities losses — 2 Other 14 8 Total 193 176 Valuation allowance (33) (28) Total deferred tax assets 160 148 Deferred tax liabilities: Loan costs (6) (15) Depreciation (12) (19) Prepaid expenses (1) (1) Amortizable intangibles (13) (15) Lease financing (32) (35) Mortgage servicing rights (8) (9) Lease ROU asset (28) (27) Net unrealized securities gains (7) — Other (2) (2) Total deferred tax liabilities (109) (123) Net deferred tax assets $ 51 $ 25

Other Comprehensive Income (Tab

Other Comprehensive Income (Tables)	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
Changes in AOCI, net of tax, by component	The following table presents changes in AOCI, net of tax, by component: TABLE 20.1 (in millions) Unrealized Unrealized Net Unrecognized Total Year Ended December 31, 2020 Balance at beginning of period $ 11 $ (18) $ (58) $ (65) Other comprehensive (loss) income before reclassifications 54 (40) (6) 8 Amounts reclassified from AOCI — 18 — 18 Net current period other comprehensive (loss) income 54 (22) (6) 26 Balance at end of period $ 65 $ (40) $ (64) $ (39)

Earnings per Common Share (Tabl

Earnings per Common Share (Tables)	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Computation of Basic and Diluted Earnings Per Common Share	The following table sets forth the computation of basic and diluted earnings per common share: TABLE 21.1 Year Ended December 31 2020 2019 2018 (dollars in millions, except per share data) Net income $ 286 $ 387 $ 373 Less: Preferred stock dividends 8 8 8 Net income available to common stockholders $ 278 $ 379 $ 365 Basic weighted average common shares outstanding 323,368,639 324,938,720 324,207,198 Net effect of dilutive stock options, warrants and restricted stock 2,119,325 1,122,418 1,416,405 Diluted weighted average common shares outstanding 325,487,964 326,061,138 325,623,603 Earnings per common share: Basic $ 0.86 $ 1.17 $ 1.13 Diluted $ 0.85 $ 1.16 $ 1.12
Schedule of Average Shares Excluded from Diluted Earnings Per Common Share Calculation	The following table shows the average shares excluded from the above calculation as their effect would have been anti-dilutive: TABLE 21.2 Year Ended December 31 2020 2019 2018 Average shares excluded from the diluted earnings per common share calculation 22,375 — 81

Regulatory Matters (Tables)

Regulatory Matters (Tables)	12 Months Ended
	Dec. 31, 2020
Banking and Thrift, Other Disclosures [Abstract]
Schedule of Capital Ratios	Following are the capital ratios for FNB and FNBPA: TABLE 22.1 Actual Well-Capitalized Requirements (1) Minimum Capital (dollars in millions) Amount Ratio Amount Ratio Amount Ratio As of December 31, 2020 F.N.B. Corporation: Total capital $ 3,324 12.33 % $ 2,695 10.00 % $ 2,830 10.50 % Tier 1 capital 2,759 10.24 1,617 6.00 2,291 8.50 Common equity tier 1 2,652 9.84 n/a n/a 1,886 7.00 Leverage 2,759 7.83 n/a n/a 1,410 4.00 Risk-weighted assets 26,948 FNBPA: Total capital 3,400 12.64 2,690 10.00 2,825 10.50 Tier 1 capital 2,882 10.71 2,152 8.00 2,287 8.50 Common equity tier 1 2,802 10.42 1,749 6.50 1,883 7.00 Leverage 2,882 8.19 1,760 5.00 1,408 4.00 Risk-weighted assets 26,902 As of December 31, 2019 F.N.B. Corporation: Total capital $ 3,174 11.81 % $ 2,687 10.00 % $ 2,821 10.50 % Tier 1 capital 2,632 9.79 1,612 6.00 2,284 8.50 Common equity tier 1 2,525 9.40 n/a n/a 1,881 7.00 Leverage 2,632 8.20 n/a n/a 1,283 4.00 Risk-weighted assets 26,866 FNBPA: Total capital 3,039 11.34 2,681 10.00 2,815 10.50 Tier 1 capital 2,841 10.60 2,144 8.00 2,279 8.50 Common equity tier 1 2,761 10.30 1,742 6.50 1,876 7.00 Leverage 2,841 8.87 1,601 5.00 1,281 4.00 Risk-weighted assets 26,806

Cash Flow Information (Tables)

Cash Flow Information (Tables)	12 Months Ended
	Dec. 31, 2020
Supplemental Cash Flow Elements [Abstract]
Summary of Cash Flow Information	Following is a summary of supplemental cash flow information: TABLE 23.1 Year Ended December 31 2020 2019 2018 (in millions) Interest paid on deposits and other borrowings $ 216 $ 329 $ 230 Income taxes paid 57 40 19 Transfers of loans to other real estate owned 3 15 12 Loans transferred to held for sale from portfolio 537 389 — Loans transferred to portfolio from held for sale — 110 —

Business Segments (Tables)

Business Segments (Tables)	12 Months Ended
	Dec. 31, 2020
Segment Reporting [Abstract]
Financial Information for Segments of FNB	The following tables provide financial information for these segments of FNB. The information provided under the caption “Parent and Other” represents operations not considered to be reportable segments and/or general operating expenses of FNB, and includes the parent company, other non-bank subsidiaries and eliminations and adjustments to reconcile to the Consolidated Financial Statements. TABLE 24.1 (in millions) Community Wealth Insurance Parent Consolidated At or for the Year Ended December 31, 2020 Interest income $ 1,129 $ — $ — $ 1 $ 1,130 Interest expense 188 — — 20 208 Net interest income 941 — — (19) 922 Provision for credit losses 123 — — — 123 Non-interest income 233 49 22 (10) 294 Non-interest expense (1) 675 35 19 8 737 Amortization of intangibles 12 — 1 — 13 Income tax expense (benefit) 61 3 — (7) 57 Net income (loss) 303 11 2 (30) 286 Total assets 37,245 38 35 36 37,354 Total intangibles 2,279 9 28 — 2,316 At or for the Year Ended December 31, 2019 Interest income $ 1,245 $ — $ — $ 2 $ 1,247 Interest expense 310 — — 20 330 Net interest income 935 — — (18) 917 Provision for credit losses 44 — — — 44 Non-interest income 237 46 20 (9) 294 Non-interest expense (1) 621 34 17 10 682 Amortization of intangibles 13 — 1 — 14 Income tax expense (benefit) 88 3 — (7) 84 Net income (loss) 406 9 2 (30) 387 Total assets 34,491 32 35 57 34,615 Total intangibles 2,291 10 28 — 2,329 (in millions) Community Wealth Insurance Consumer Parent Consolidated At or for the Year Ended December 31, 2018 Interest income $ 1,145 $ — $ — $ 25 $ — $ 1,170 Interest expense 219 — — 2 17 238 Net interest income 926 — — 23 (17) 932 Provision for credit losses 54 — — 6 1 61 Non-interest income 213 44 16 2 1 276 Non-interest expense (1) 609 33 17 15 5 679 Amortization of intangibles 15 1 — — — 16 Income tax expense (benefit) 82 2 — 1 (6) 79 Net income (loss) 379 8 (1) 3 (16) 373 Total assets 32,997 26 25 — 54 33,102 Total intangibles 2,304 10 20 — — 2,334 (1) Excludes amortization of intangibles, which is presented separately .

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurement Inputs and Valuation Techniques	The fair value hierarchy is broken down into three levels based on the reliability of inputs as follows: TABLE 25.1 Measurement Definition Level 1 Valuation is based upon unadjusted quoted market prices for identical instruments traded in active markets. Level 2 Valuation is based upon quoted market prices for similar instruments traded in active markets, quoted market prices for identical or similar instruments traded in markets that are not active and model-based valuation techniques for which all significant assumptions are observable in the market or can be corroborated by market data. Level 3 Valuation is derived from other valuation methodologies including discounted cash flow models and similar techniques that use significant assumptions not observable in the market. These unobservable assumptions reflect estimates of assumptions that market participants would use in determining fair value.
Balances of Assets and Liabilities Measured at Fair Value on Recurring Basis	The following table presents the balances of assets and liabilities measured at fair value on a recurring basis: TABLE 25.2 (in millions) Level 1 Level 2 Level 3 Total December 31, 2020 Assets Measured at Fair Value Debt securities available for sale U.S. Treasury $ 600 $ — $ — $ 600 U.S. government agencies — 172 — 172 U.S. government-sponsored entities — 161 — 161 Residential mortgage-backed securities Agency mortgage-backed securities — 994 — 994 Agency collateralized mortgage obligations — 1,124 — 1,124 Commercial mortgage-backed securities — 378 — 378 States of the U.S. and political subdivisions (municipals) — 32 — 32 Other debt securities — 2 — 2 Total debt securities available for sale 600 2,863 — 3,463 Loans held for sale — 144 — 144 Derivative financial instruments Trading — 349 — 349 Not for trading — 3 24 27 Total derivative financial instruments — 352 24 376 Total assets measured at fair value on a recurring basis $ 600 $ 3,359 $ 24 $ 3,983 Liabilities Measured at Fair Value Derivative financial instruments Trading $ — $ 37 $ — $ 37 Not for trading — 3 — 3 Total derivative financial instruments — 40 — 40 Total liabilities measured at fair value on a recurring basis $ — $ 40 $ — $ 40 (in millions) Level 1 Level 2 Level 3 Total December 31, 2019 Assets Measured at Fair Value Debt securities available for sale U.S. government agencies $ — $ 151 $ — $ 151 U.S. government-sponsored entities — 226 — 226 Residential mortgage-backed securities Agency mortgage-backed securities — 1,314 — 1,314 Agency collateralized mortgage obligations — 1,240 — 1,240 Commercial mortgage-backed securities — 345 — 345 States of the U.S. and political subdivisions (municipals) — 11 — 11 Other debt securities — 2 — 2 Total debt securities available for sale — 3,289 — 3,289 Loans held for sale — 41 — 41 Derivative financial instruments Trading — 149 — 149 Not for trading — 2 3 5 Total derivative financial instruments — 151 3 154 Total assets measured at fair value on a recurring basis $ — $ 3,481 $ 3 $ 3,484 Liabilities Measured at Fair Value Derivative financial instruments Trading $ — $ 24 $ — $ 24 Not for trading — 1 — 1 Total derivative financial instruments — 25 — 25 Total liabilities measured at fair value on a recurring basis $ — $ 25 $ — $ 25
Additional Information about Assets Measured at Fair Value on Recurring Basis	The following table presents additional information about assets measured at fair value on a recurring basis and for which we have utilized Level 3 inputs to determine fair value: TABLE 25.3 (in millions) Interest Total Year Ended December 31, 2020 Balance at beginning of period $ 3 $ 3 Purchases, issuances, sales and settlements: Issuances 24 24 Settlements (3) (3) Balance at end of period $ 24 $ 24 Year Ended December 31, 2019 Balance at beginning of period $ 1 $ 1 Purchases, issuances, sales and settlements: Issuances 3 3 Settlements (1) (1) Balance at end of period $ 3 $ 3
Additional Information about Assets Measured at Fair Value on Non-Recurring Basis	For assets measured at fair value on a non-recurring basis still held at the Balance Sheet date, the following table provides the hierarchy level and the fair value of the related assets or portfolios: TABLE 25.4 (in millions) Level 1 Level 2 Level 3 Total December 31, 2020 Collateral dependent loans $ — $ — $ 45 $ 45 Other real estate owned — — 3 3 Other assets - SBA servicing asset — — 3 3 Other assets - MSRs — — 36 36 December 31, 2019 Impaired loans $ — $ — $ 5 $ 5 Other real estate owned — — 4 4 Other assets - SBA servicing asset — — 3 3 Other assets - MSRs — — 30 30
Fair Values of Financial Instruments	The fair values of our financial instruments are as follows: TABLE 25.5 Fair Value Measurements (in millions) Carrying Fair Level 1 Level 2 Level 3 December 31, 2020 Financial Assets Cash and cash equivalents $ 1,383 $ 1,383 $ 1,383 $ — $ — Debt securities available for sale 3,463 3,463 600 2,863 — Debt securities held to maturity 2,868 2,973 — 2,973 — Net loans and leases, including loans held for sale 25,250 25,012 — 144 24,868 Loan servicing rights 39 39 — — 39 Derivative assets 376 376 — 352 24 Accrued interest receivable 90 90 90 — — Financial Liabilities Deposits 29,122 29,158 25,460 3,698 — Short-term borrowings 1,804 1,809 1,809 — — Long-term borrowings 1,095 1,068 — — 1,068 Derivative liabilities 40 40 — 40 — Accrued interest payable 13 13 13 — — December 31, 2019 Financial Assets Cash and cash equivalents $ 599 $ 599 $ 599 $ — $ — Debt securities available for sale 3,289 3,289 — 3,289 — Debt securities held to maturity 3,275 3,305 — 3,305 — Net loans and leases, including loans held for sale 23,144 22,930 — 41 22,889 Loan servicing rights 46 48 — — 48 Derivative assets 154 154 — 151 3 Accrued interest receivable 109 109 109 — — Financial Liabilities Deposits 24,786 24,797 20,058 4,739 — Short-term borrowings 3,216 3,219 3,219 — — Long-term borrowings 1,340 1,355 — — 1,355 Derivative liabilities 25 25 — 25 — Accrued interest payable 21 21 21 — —

Parent Company Financial Stat_2

Parent Company Financial Statements (Tables)	12 Months Ended
	Dec. 31, 2020
Condensed Financial Information Disclosure [Abstract]
Consolidated Balance Sheet of Parent Company Only	Balance Sheets (in millions) December 31 2020 2019 Assets Cash and cash equivalents $ 380 $ 251 Other assets 10 18 Investment in bank subsidiary 5,064 5,072 Investments in and advances to non-bank subsidiaries 371 104 Total Assets $ 5,825 $ 5,445 Liabilities Other liabilities $ 40 $ 34 Advances from affiliates 197 197 Long-term borrowings 621 323 Subordinated notes: Short-term 7 7 Long-term 1 1 Total Liabilities 866 562 Stockholders’ Equity 4,959 4,883 Total Liabilities and Stockholders’ Equity $ 5,825 $ 5,445
Statements of Income of Parent Company Only	Statements of Income (in millions) Year Ended December 31 2020 2019 2018 Income Dividend income from subsidiaries: Bank $ 300 $ 179 $ 162 Non-bank 4 2 8 304 181 170 Interest income 6 — 4 Other income — — 5 Total Income 310 181 179 Expenses Interest expense 25 19 20 Other expenses 18 18 15 Total Expenses 43 37 35 Income Before Taxes and Equity in Undistributed Income of Subsidiaries 267 144 144 Income tax benefit 7 7 6 274 151 150 Equity in undistributed income (loss) of subsidiaries: Bank 15 236 225 Non-bank (3) — (2) Net Income $ 286 $ 387 $ 373
Statements of Cash Flows of Parent Company Only	Statements of Cash Flows (in millions) Year Ended December 31 2020 2019 2018 Operating Activities Net income $ 286 $ 387 $ 373 Adjustments to reconcile net income to net cash flows from operating activities: Undistributed earnings from subsidiaries (12) (236) (222) Other, net 13 2 (13) Net cash flows provided by operating activities 287 153 138 Investing Activities Proceeds from sale of securities available for sale — — 1 Net decrease in advances to subsidiaries — — 20 Payment for further investment in subsidiaries (270) (47) (22) Net cash received in business combinations — — 123 Net cash flows (used in) provided by investing activities (270) (47) 122 Financing Activities Net decrease in advance from affiliate — — (19) Net decrease in short-term borrowings — — (1) Decrease in long-term debt (4) (77) (2) Increase in long-term debt 302 121 1 Other, net (21) 12 14 Cash dividends paid: Preferred stock (8) (8) (8) Common stock (157) (157) (157) Net cash flows provided by (used in) financing activities 112 (109) (172) Net Increase (Decrease) in Cash and Cash Equivalents 129 (3) 88 Cash and cash equivalents at beginning of year 251 254 166 Cash and Cash Equivalents at End of Year $ 380 $ 251 $ 254 Cash paid during the year for: Interest $ 26 $ 20 $ 17

Quarterly Earnings Summary (U_2

Quarterly Earnings Summary (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2020
Quarterly Earnings Summary (Unaudited) [Abstract]
Quarterly Financial Information	TABLE 27.1 (Dollars in millions, except per share data) Quarter Ended 2020 Dec. 31 Sept. 30 June 30 Mar. 31 Total interest income $ 270 $ 273 $ 281 $ 306 Total interest expense 36 46 52 74 Net interest income 234 227 229 232 Provision for credit losses 18 27 30 48 Total non-interest income 68 80 77 69 Total non-interest expense 199 180 176 195 Net income 72 83 84 47 Net income available to common stockholders 70 81 82 45 Per Common Share Basic earnings per share $ 0.22 $ 0.25 $ 0.25 $ 0.14 Diluted earnings per share 0.22 0.25 0.25 0.14 Quarter Ended 2019 Total interest income $ 306 $ 314 $ 317 $ 310 Total interest expense 80 84 87 79 Net interest income 226 230 230 231 Provision for credit losses 7 12 11 14 Other non-interest income 74 80 75 65 Total non-interest expense 177 178 175 166 Net income 95 103 95 94 Net income available to common stockholders 93 101 93 92 Per Common Share Basic earnings per share $ 0.29 $ 0.31 $ 0.29 $ 0.28 Diluted earnings per share 0.29 0.31 0.29 0.28

Nature of Operations - Addition

Nature of Operations - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2020StateOffice
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of states, company operating financial services | State	7
Number of banking offices | Office	358

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	Jan. 01, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Summary Of Significant Accounting Policies [Line Items]
Increase (decrease) in stockholders' equity attributable to parent		$ 4,959,000,000	$ 4,883,000,000	$ 4,608,000,000	$ 4,409,000,000
Initial ACL on PCD Loans	$ 50,300,000	$ 50,300,000
Other than temporary impairment losses			0	0
Allowances for impaired commercial loans			1,000,000
Core deposit intangibles amortization period, years		10 years
Largest amount recognized in the financial statement of tax benefit threshold, minimum		greater than 50%
Marketing expense		$ 12,600,000	13,100,000	12,800,000
Vesting period of awards issued, years		3 years
Retained Earnings
Summary Of Significant Accounting Policies [Line Items]
Increase (decrease) in stockholders' equity attributable to parent		$ 869,000,000	798,000,000	$ 576,000,000	$ 368,000,000
Accounting Standards Update 2016-13 | Retained Earnings
Summary Of Significant Accounting Policies [Line Items]
Increase (decrease) in stockholders' equity attributable to parent	(51,000,000)
Impact of ASC 326 Adoption
Summary Of Significant Accounting Policies [Line Items]
Increase (decrease) in stockholders' equity attributable to parent			(50,000,000)
Impact of ASC 326 Adoption | Retained Earnings
Summary Of Significant Accounting Policies [Line Items]
Increase (decrease) in stockholders' equity attributable to parent			$ (50,000,000)
Impact of ASC 326 Adoption | Accounting Standards Update 2016-13 | Retained Earnings
Summary Of Significant Accounting Policies [Line Items]
Increase (decrease) in stockholders' equity attributable to parent	$ (50,600,000)
Restricted Stock Units (RSUs)
Summary Of Significant Accounting Policies [Line Items]
Vesting period of awards issued, years		3 years
Commercial loan
Summary Of Significant Accounting Policies [Line Items]
Threshold period past due for non-accrual loans		90 days
Installment Loans
Summary Of Significant Accounting Policies [Line Items]
Threshold period past due for non-accrual loans		120 days
Residential Mortgages and Consumer Lines of Credit
Summary Of Significant Accounting Policies [Line Items]
Threshold period past due for non-accrual loans		180 days
Minimum
Summary Of Significant Accounting Policies [Line Items]
Useful life of the asset, years		3 years
Estimated useful life of intangibles, years		8 years
Minimum | Commercial loan
Summary Of Significant Accounting Policies [Line Items]
Financing receivable, individual reserves in default, threshold		$ 1,000,000
Maximum
Summary Of Significant Accounting Policies [Line Items]
Useful life of the asset, years		39 years
Estimated useful life of intangibles, years		13 years
Maximum | Commercial and Consumer Loans
Summary Of Significant Accounting Policies [Line Items]
Financing receivable, individual reserves in default, threshold		$ 1,000,000

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Impact of Adoption (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Jan. 01, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Debt securities held to maturity, allowance for credit losses	$ 40
Allowance for credit loss	363,000	$ 196,000	$ 196,000	$ 180,000	$ 175,000
Allowance for credit losses on off-balance sheet credit exposures		3,000
As Reported Under ASC 326
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit loss		301,000
Allowance for credit losses on off-balance sheet credit exposures		13,000
Impact of ASC 326 Adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit loss		105,000
Allowance for credit losses on off-balance sheet credit exposures		10,000
States of the U.S. and political subdivisions (municipals)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Debt securities held to maturity, allowance for credit losses	40	0
States of the U.S. and political subdivisions (municipals) | As Reported Under ASC 326
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Debt securities held to maturity, allowance for credit losses		0
States of the U.S. and political subdivisions (municipals) | Impact of ASC 326 Adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Debt securities held to maturity, allowance for credit losses		0
Commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit loss	181,000	60,000	60,000
Commercial real estate | As Reported Under ASC 326
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit loss		138,000
Commercial real estate | Impact of ASC 326 Adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit loss		78,000
Commercial and industrial
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit loss	81,000	53,000	53,000
Commercial and industrial | As Reported Under ASC 326
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit loss		65,000
Commercial and industrial | Impact of ASC 326 Adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit loss		12,000
Commercial leases
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit loss	17,000	11,000	11,000
Commercial leases | As Reported Under ASC 326
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit loss		11,000
Commercial leases | Impact of ASC 326 Adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit loss		0
Other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit loss	1,000	9,000	9,000
Other | As Reported Under ASC 326
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit loss		0
Other | Impact of ASC 326 Adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit loss		(9,000)
Direct installment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit loss	26,000	13,000	13,000
Direct installment | As Reported Under ASC 326
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit loss		24,000
Direct installment | Impact of ASC 326 Adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit loss		11,000
Residential mortgages
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit loss	34,000	22,000	22,000
Residential mortgages | As Reported Under ASC 326
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit loss		32,000
Residential mortgages | Impact of ASC 326 Adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit loss		10,000
Indirect installment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit loss	11,000	19,000	19,000
Indirect installment | As Reported Under ASC 326
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit loss		21,000
Indirect installment | Impact of ASC 326 Adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit loss		2,000
Consumer lines of credit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit loss	$ 12,000	9,000	$ 9,000
Consumer lines of credit | As Reported Under ASC 326
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit loss		10,000
Consumer lines of credit | Impact of ASC 326 Adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit loss		$ 1,000

New Accounting Standards (Detai

New Accounting Standards (Details) - USD ($) $ in Millions	Jan. 01, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit loss	$ 196	$ 363	$ 196	$ 180	$ 175
Financing receivable, allowance for credit loss, period increase (decrease)	105.3	167.2
Stockholders' equity attributable to parent		4,959	4,883	4,608	4,409
Accounting Standards Update 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit loss	301
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' equity attributable to parent		$ 869	$ 798	$ 576	$ 368
Retained Earnings | Accounting Standards Update 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' equity attributable to parent	(51)
Financing Receivables, Originated Loans And Leases | Accounting Standards Update 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Financing receivable, allowance for credit loss, period increase (decrease)	55
Longer Duration Loans and Gross Up | Accounting Standards Update 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Financing receivable, allowance for credit loss, period increase (decrease)	50
Unfunded Loan Commitment | Accounting Standards Update 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit loss	10
Financing receivable, allowance for credit loss, period increase (decrease)	$ 10

Securities - Additional Informa

Securities - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2020	Jan. 01, 2020
Schedule Of Securities [Line Items]
Debt securities available for sale, allowance for credit losses	$ 0
Debt securities held to maturity, allowance for credit losses	40,000
Municipal bond portfolio, value	$ 1,100,000,000
Percentage of formal credit enhancement insurance of municipalities	62.00%
Debt securities, held-to-maturity, provision expense	$ 4,000
Available-for-sale debt securities
Schedule Of Securities [Line Items]
Accrued investment income receivable	6,200,000
States of the U.S. and political subdivisions (municipals)
Schedule Of Securities [Line Items]
Debt securities held to maturity, allowance for credit losses	40,000	$ 0
Held-to-maturity securities
Schedule Of Securities [Line Items]
Accrued investment income receivable	12,500,000
Municipal Bonds | Weighted Average
Schedule Of Securities [Line Items]
Average holding size of securities in bond portfolio	$ 3,500,000
Municipal Bonds | Credit Concentration Risk | General Obligation Bonds | A Rating | Minimum
Schedule Of Securities [Line Items]
Percentage of portfolio	100.00%
Municipal Bonds | Credit Concentration Risk | General Obligation Bonds | A Rating or Better
Schedule Of Securities [Line Items]
Percentage of portfolio	99.00%
Municipal Bonds | Geographic Concentration Risk | Pennsylvania, Ohio and Maryland
Schedule Of Securities [Line Items]
Percentage of portfolio	65.00%

Securities - Schedule of Amorti

Securities - Schedule of Amortized Cost and Fair Value of Securities Available for Sale (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Schedule of Investments [Line Items]
Amortized Cost	$ 3,380	$ 3,275
Gross Unrealized Gains	84	24
Gross Unrealized Losses	(1)	(10)
Fair Value	3,463	3,289
U.S. Treasury
Schedule of Investments [Line Items]
Amortized Cost	600
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Fair Value	600
U.S. government agencies
Schedule of Investments [Line Items]
Amortized Cost	172	152
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	(1)
Fair Value	172	151
U.S. government-sponsored entities
Schedule of Investments [Line Items]
Amortized Cost	160	225
Gross Unrealized Gains	1	1
Gross Unrealized Losses	0	0
Fair Value	161	226
Agency mortgage-backed securities
Schedule of Investments [Line Items]
Amortized Cost	959	1,310
Gross Unrealized Gains	35	7
Gross Unrealized Losses	0	(3)
Fair Value	994	1,314
Agency collateralized mortgage obligations
Schedule of Investments [Line Items]
Amortized Cost	1,094	1,234
Gross Unrealized Gains	31	10
Gross Unrealized Losses	(1)	(4)
Fair Value	1,124	1,240
Commercial mortgage-backed securities
Schedule of Investments [Line Items]
Amortized Cost	361	341
Gross Unrealized Gains	17	6
Gross Unrealized Losses	0	(2)
Fair Value	378	345
States of the U.S. and political subdivisions (municipals)
Schedule of Investments [Line Items]
Amortized Cost	32	11
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	32	11
Other debt securities
Schedule of Investments [Line Items]
Amortized Cost	2	2
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	$ 2	$ 2

Securities - Schedule of Amor_2

Securities - Schedule of Amortized Cost and Fair Value of Securities Held to Maturity (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity, total	$ 2,868	$ 3,275
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	105	42
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	0	(12)
Debt securities held-to-maturity, fair value	2,973	3,305
U.S. Treasury
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity, total	1	1
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	0	0
Debt securities held-to-maturity, fair value	1	1
U.S. government agencies
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity, total	1	1
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	0	0
Debt securities held-to-maturity, fair value	1	1
U.S. government-sponsored entities
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity, total	120	175
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	1	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	0	0
Debt securities held-to-maturity, fair value	121	175
Agency mortgage-backed securities
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity, total	769	949
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	29	8
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	0	(2)
Debt securities held-to-maturity, fair value	798	955
Agency collateralized mortgage obligations
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity, total	562	721
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	17	5
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	0	(6)
Debt securities held-to-maturity, fair value	579	720
Commercial mortgage-backed securities
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity, total	307	308
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	10	3
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	0	(2)
Debt securities held-to-maturity, fair value	317	309
States of the U.S. and political subdivisions (municipals)
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity, total	1,108	1,120
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	48	26
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	0	(2)
Debt securities held-to-maturity, fair value	$ 1,156	$ 1,144

Securities - Amortized Cost and

Securities - Amortized Cost and Fair Value of Securities, by Contractual Maturities (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Schedule Of Securities [Line Items]
Available for sale, due in one year or less, amortized cost	$ 642
Available for sale, due after one year but within five years, amortized cost	113
Available for sale, due after five year but within ten years, amortized cost	124
Available for sale, due after ten years, amortized cost	87
Available for sale, with contractual maturities, amortized cost	966
Amortized Cost	3,380	$ 3,275
Available for sale, due in one year or less, fair value	642
Available for sale, due after one year but within five years, fair value	114
Available for sale, due after five year but within ten years, fair value	125
Available for sale, due after ten years, fair value	86
Available for sale, with contractual maturities, amortized cost	967
Total securities available for sale, fair value	3,463	3,289
Held to maturity, due in one year or less, amortized cost	122
Held to maturity, due after one year but within five years, amortized cost	20
Held to maturity, due after five year but within ten years, amortized cost	151
Held to maturity, due after ten years, amortized cost	937
Held to maturity, with contractual maturities, amortized cost	1,230
Held-to-maturity, total	2,868	3,275
Held to maturity, due in one year or less, fair value	123
Held to maturity, due after one year but within five years, fair value	20
Held to maturity, due after five year but within ten years, fair value	155
Held to maturity, due after ten years, fair value	981
Held to maturity, with contractual maturities, amortized cost	1,279
Held-to-maturity, fair value, net	2,973	3,305
Agency mortgage-backed securities
Schedule Of Securities [Line Items]
Available-for-sale, amortized cost	959
Amortized Cost	959	1,310
Available for sale, fair value	994
Total securities available for sale, fair value	994	1,314
Held-to-maturity, amortized cost	769
Held-to-maturity, total	769	949
Held-to-maturity, fair value	798
Held-to-maturity, fair value, net	798	955
Agency collateralized mortgage obligations
Schedule Of Securities [Line Items]
Available-for-sale, amortized cost	1,094
Amortized Cost	1,094	1,234
Available for sale, fair value	1,124
Total securities available for sale, fair value	1,124	1,240
Held-to-maturity, amortized cost	562
Held-to-maturity, total	562	721
Held-to-maturity, fair value	579
Held-to-maturity, fair value, net	579	720
Commercial mortgage-backed securities
Schedule Of Securities [Line Items]
Available-for-sale, amortized cost	361
Amortized Cost	361	341
Available for sale, fair value	378
Total securities available for sale, fair value	378	345
Held-to-maturity, amortized cost	307
Held-to-maturity, total	307	308
Held-to-maturity, fair value	317
Held-to-maturity, fair value, net	$ 317	$ 309

Securities - Schedule of Securi

Securities - Schedule of Securities Pledged as Collateral (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
To secure public deposits, trust deposits and for other purposes as required by law	$ 5,384	$ 4,494
As collateral for short-term borrowings	$ 402	$ 285
Securities pledged as a percent of total securities	91.40%	72.80%

Securities - Summaries of Fair

Securities - Summaries of Fair Values and Unrealized Losses of Securities, Segregated by Length of Impairment (Detail) $ in Millions	Dec. 31, 2020USD ($)Security	Dec. 31, 2019USD ($)Security
Schedule Of Securities [Line Items]
Debt securities, available-for-sale, less than 12 months, number of positions | Security	7	32
Debt securities, available-for-sale, 12 months or longer, number of positions | Security	17	78
Debt securities, available-for-sale, number of positions | Security	24	110
Debt securities, available-for-sale, less than 12 months	$ 168	$ 685
Debt securities, available-for-sale, 12 months or longer	71	712
Debt securities, available-for-sale, unrealized loss position	239	1,397
Debt securities, available-for-sale, less than 12 months, accumulated loss	(1)	(4)
Debt securities, available-for-sale, 12 months or longer, accumulated loss	0	(6)
Debt securities, available-for-sale, accumulated loss	$ (1)	$ (10)
U.S. government agencies
Schedule Of Securities [Line Items]
Debt securities, available-for-sale, less than 12 months, number of positions | Security	1	5
Debt securities, available-for-sale, 12 months or longer, number of positions | Security	16	15
Debt securities, available-for-sale, number of positions | Security	17	20
Debt securities, available-for-sale, less than 12 months	$ 13	$ 48
Debt securities, available-for-sale, 12 months or longer	69	61
Debt securities, available-for-sale, unrealized loss position	82	109
Debt securities, available-for-sale, less than 12 months, accumulated loss	0	0
Debt securities, available-for-sale, 12 months or longer, accumulated loss	0	(1)
Debt securities, available-for-sale, accumulated loss	$ 0	$ (1)
U.S. government-sponsored entities
Schedule Of Securities [Line Items]
Debt securities, available-for-sale, less than 12 months, number of positions | Security	1	0
Debt securities, available-for-sale, 12 months or longer, number of positions | Security	0	6
Debt securities, available-for-sale, number of positions | Security	1	6
Debt securities, available-for-sale, less than 12 months	$ 25	$ 0
Debt securities, available-for-sale, 12 months or longer	0	130
Debt securities, available-for-sale, unrealized loss position	25	130
Debt securities, available-for-sale, less than 12 months, accumulated loss	0	0
Debt securities, available-for-sale, 12 months or longer, accumulated loss	0	0
Debt securities, available-for-sale, accumulated loss	$ 0	$ 0
Agency mortgage-backed securities
Schedule Of Securities [Line Items]
Debt securities, available-for-sale, less than 12 months, number of positions | Security		13
Debt securities, available-for-sale, 12 months or longer, number of positions | Security		24
Debt securities, available-for-sale, number of positions | Security		37
Debt securities, available-for-sale, less than 12 months		$ 200
Debt securities, available-for-sale, 12 months or longer		314
Debt securities, available-for-sale, unrealized loss position		514
Debt securities, available-for-sale, less than 12 months, accumulated loss		(1)
Debt securities, available-for-sale, 12 months or longer, accumulated loss		(2)
Debt securities, available-for-sale, accumulated loss		$ (3)
Agency collateralized mortgage obligations
Schedule Of Securities [Line Items]
Debt securities, available-for-sale, less than 12 months, number of positions | Security	5	11
Debt securities, available-for-sale, 12 months or longer, number of positions | Security	0	32
Debt securities, available-for-sale, number of positions | Security	5	43
Debt securities, available-for-sale, less than 12 months	$ 130	$ 323
Debt securities, available-for-sale, 12 months or longer	0	205
Debt securities, available-for-sale, unrealized loss position	130	528
Debt securities, available-for-sale, less than 12 months, accumulated loss	(1)	(1)
Debt securities, available-for-sale, 12 months or longer, accumulated loss	0	(3)
Debt securities, available-for-sale, accumulated loss	$ (1)	$ (4)
Non-agency collateralized mortgage obligations
Schedule Of Securities [Line Items]
Debt securities, available-for-sale, less than 12 months, number of positions | Security		0
Debt securities, available-for-sale, 12 months or longer, number of positions | Security		0
Debt securities, available-for-sale, number of positions | Security		0
Debt securities, available-for-sale, less than 12 months		$ 0
Debt securities, available-for-sale, 12 months or longer		0
Debt securities, available-for-sale, unrealized loss position		0
Debt securities, available-for-sale, less than 12 months, accumulated loss		0
Debt securities, available-for-sale, 12 months or longer, accumulated loss		0
Debt securities, available-for-sale, accumulated loss		$ 0
Commercial mortgage-backed securities
Schedule Of Securities [Line Items]
Debt securities, available-for-sale, less than 12 months, number of positions | Security		3
Debt securities, available-for-sale, 12 months or longer, number of positions | Security		0
Debt securities, available-for-sale, number of positions | Security		3
Debt securities, available-for-sale, less than 12 months		$ 114
Debt securities, available-for-sale, 12 months or longer		0
Debt securities, available-for-sale, unrealized loss position		114
Debt securities, available-for-sale, less than 12 months, accumulated loss		(2)
Debt securities, available-for-sale, 12 months or longer, accumulated loss		0
Debt securities, available-for-sale, accumulated loss		$ (2)
States of the U.S. and political subdivisions (municipals)
Schedule Of Securities [Line Items]
Debt securities, available-for-sale, less than 12 months, number of positions | Security		0
Debt securities, available-for-sale, 12 months or longer, number of positions | Security		0
Debt securities, available-for-sale, number of positions | Security		0
Debt securities, available-for-sale, less than 12 months		$ 0
Debt securities, available-for-sale, 12 months or longer		0
Debt securities, available-for-sale, unrealized loss position		0
Debt securities, available-for-sale, less than 12 months, accumulated loss		0
Debt securities, available-for-sale, 12 months or longer, accumulated loss		0
Debt securities, available-for-sale, accumulated loss		$ 0
Other debt securities
Schedule Of Securities [Line Items]
Debt securities, available-for-sale, less than 12 months, number of positions | Security	0	0
Debt securities, available-for-sale, 12 months or longer, number of positions | Security	1	1
Debt securities, available-for-sale, number of positions | Security	1	1
Debt securities, available-for-sale, less than 12 months	$ 0	$ 0
Debt securities, available-for-sale, 12 months or longer	2	2
Debt securities, available-for-sale, unrealized loss position	2	2
Debt securities, available-for-sale, less than 12 months, accumulated loss	0	0
Debt securities, available-for-sale, 12 months or longer, accumulated loss	0	0
Debt securities, available-for-sale, accumulated loss	$ 0	$ 0

Other Securities - Additional I

Other Securities - Additional Information (Detail) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Banking and Thrift, Interest [Abstract]
Federal Home Loan Bank stock	$ 154,000,000	$ 256,000,000
Federal Reserve Bank stock	124,000,000	123,000,000
Other non-marketable equity securities	0	1,000,000
Total non-marketable equity securities	278,000,000	380,000,000
Other non-marketable equity securities, impairment	$ 0	$ 0

Loans and Leases - Additional I

Loans and Leases - Additional Information (Detail) $ in Millions	Jan. 01, 2020USD ($)	Dec. 31, 2020USD ($)State	Dec. 31, 2020USD ($)State	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrued interest receivable		$ 62.9	$ 62.9
Purchased with credit deterioration included with allowance for credit losses, amount	$ 50.3		50.3
Purchased with credit deterioration, discount			110
Discount remaining		$ 50.9	$ 50.9
Number of states, company operating financial services | State		7	7
Loans transferred to held for sale from portfolio through sale		$ 500	$ 537	$ 389	$ 0
Loans granted short-term modification due to COVID-19		397	397
Restructured loans returned to performing status			7.7
Allowance for credit loss	196	363	363	196	$ 180	$ 175
Pooled reserves for all other classes of loans		$ 4.1	$ 4.1	4.1
Minimum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due period for loan to be in default			90 days
Maximum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due period for loan to be in default			12 months
SBA-Guaranteed Loan Servicing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Guaranteed percentage		100.00%	100.00%
Residential Mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying value of OREO through foreclosure		$ 2.5	$ 2.5	3.3
Mortgage loans on real estate, foreclosure			8.2	9.2
Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for credit loss	$ 53	81	81	53
Commercial and industrial | Paycheck Protection Program Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans to customers		2,200	2,200
Commercial loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, collateral dependent		91.4	91.4
Commercial loan | Minimum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Threshold for loans whose terms have been modified in a trouble debt restructuring, non accrual		1	1
Total commercial loans and leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for credit loss		280	280	133
Specific reserves for commercial troubled debt restructurings | Total commercial loans and leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for credit loss		2.8	2.8
Specific reserves for commercial troubled debt restructurings | Total commercial loans and leases | Maximum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for credit loss				0.5
Pooled reserves for individual commercial loans | Total commercial loans and leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for credit loss		$ 2.5	$ 2.5	$ 0.8

Loans and Leases - Summary of L

Loans and Leases - Summary of Loans and Leases, Net of Unearned Income (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans and Leases	$ 25,459	$ 23,289
Total commercial loans and leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans and Leases	17,470	14,721
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans and Leases	9,731	8,960
Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans and Leases	7,214	5,308
Commercial leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans and Leases	485	432
Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans and Leases	40	21
Total consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans and Leases	7,989	8,568
Direct installment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans and Leases	2,020	1,821
Residential mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans and Leases	3,433	3,374
Indirect installment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans and Leases	1,218	1,922
Consumer lines of credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans and Leases	$ 1,318	$ 1,451

Loans and Leases - Certain Info

Loans and Leases - Certain Information Relating to Commercial Real Estate Loans (Detail) - Loan portfolio diversification risk - Commercial real estate loans	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Percent owner-occupied
Financing Receivable, Allowance for Credit Loss [Line Items]
Percent of total loans and leases	28.10%	30.60%
Percent non-owner-occupied
Financing Receivable, Allowance for Credit Loss [Line Items]
Percent of total loans and leases	71.90%	69.40%

Loans and Leases - Summary of_2

Loans and Leases - Summary of Loans to Related Parties (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)
Financing Receivable, Allowance For Credit Losses [Roll Foward]
Balance at beginning of period	$ 7
New loans	2
Repayments	(2)
Balance at end of period	$ 7

Loans and Leases - Origination

Loans and Leases - Origination Year (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
2020	$ 7,565
2019	4,429
2018	2,837
2017	2,281
2016	1,800
Prior	3,917
Revolving Loans Amortized Cost Basis	2,630
Total Loans and Leases	25,459	$ 23,289
Total commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,892
2019	1,916
2018	1,244
2017	1,166
2016	1,074
Prior	2,266
Revolving Loans Amortized Cost Basis	173
Total Loans and Leases	9,731
Total commercial real estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,879
2019	1,854
2018	1,135
2017	927
2016	888
Prior	1,911
Revolving Loans Amortized Cost Basis	163
Total Loans and Leases	8,757
Total commercial real estate | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	9
2019	30
2018	80
2017	158
2016	70
Prior	163
Revolving Loans Amortized Cost Basis	4
Total Loans and Leases	514
Total commercial real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	4
2019	32
2018	29
2017	81
2016	116
Prior	192
Revolving Loans Amortized Cost Basis	6
Total Loans and Leases	460
Total commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
2020	3,324
2019	1,056
2018	668
2017	376
2016	136
Prior	383
Revolving Loans Amortized Cost Basis	1,271
Total Loans and Leases	7,214	5,308
Total commercial and industrial | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	3,286
2019	1,007
2018	590
2017	304
2016	120
Prior	311
Revolving Loans Amortized Cost Basis	1,095
Total Loans and Leases	6,713
Total commercial and industrial | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	30
2019	23
2018	13
2017	28
2016	10
Prior	35
Revolving Loans Amortized Cost Basis	79
Total Loans and Leases	218
Total commercial and industrial | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	8
2019	26
2018	65
2017	44
2016	6
Prior	37
Revolving Loans Amortized Cost Basis	97
Total Loans and Leases	283
Total commercial leases
Financing Receivable, Credit Quality Indicator [Line Items]
2020	186
2019	137
2018	89
2017	61
2016	7
Prior	5
Revolving Loans Amortized Cost Basis	0
Total Loans and Leases	485	432
Total commercial leases | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	178
2019	134
2018	83
2017	56
2016	5
Prior	3
Revolving Loans Amortized Cost Basis	0
Total Loans and Leases	459
Total commercial leases | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1
2019	1
2018	4
2017	4
2016	1
Prior	2
Revolving Loans Amortized Cost Basis	0
Total Loans and Leases	13
Total commercial leases | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	7
2019	2
2018	2
2017	1
2016	1
Prior	0
Revolving Loans Amortized Cost Basis	0
Total Loans and Leases	13
Total other commercial
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	5
Revolving Loans Amortized Cost Basis	35
Total Loans and Leases	40	21
Total other commercial | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	4
Revolving Loans Amortized Cost Basis	35
Total Loans and Leases	39
Total other commercial | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	1
Revolving Loans Amortized Cost Basis	0
Total Loans and Leases	1
Total commercial
Financing Receivable, Credit Quality Indicator [Line Items]
2020	5,402
2019	3,109
2018	2,001
2017	1,603
2016	1,217
Prior	2,659
Revolving Loans Amortized Cost Basis	1,479
Total Loans and Leases	17,470	14,721
Total direct installment
Financing Receivable, Credit Quality Indicator [Line Items]
2020	706
2019	338
2018	202
2017	144
2016	173
Prior	456
Revolving Loans Amortized Cost Basis	1
Total Loans and Leases	2,020	1,821
Total direct installment | Current
Financing Receivable, Credit Quality Indicator [Line Items]
2020	706
2019	337
2018	200
2017	143
2016	171
Prior	442
Revolving Loans Amortized Cost Basis	1
Total Loans and Leases	2,000
Total direct installment | Past due
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	1
2018	2
2017	1
2016	2
Prior	14
Revolving Loans Amortized Cost Basis	0
Total Loans and Leases	20
Total residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,080
2019	712
2018	290
2017	382
2016	336
Prior	632
Revolving Loans Amortized Cost Basis	1
Total Loans and Leases	3,433	3,374
Total residential mortgages | Current
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,079
2019	707
2018	283
2017	378
2016	330
Prior	603
Revolving Loans Amortized Cost Basis	1
Total Loans and Leases	3,381
Total residential mortgages | Past due
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1
2019	5
2018	7
2017	4
2016	6
Prior	29
Revolving Loans Amortized Cost Basis	0
Total Loans and Leases	52
Total indirect installment
Financing Receivable, Credit Quality Indicator [Line Items]
2020	373
2019	263
2018	336
2017	149
2016	69
Prior	28
Revolving Loans Amortized Cost Basis	0
Total Loans and Leases	1,218	1,922
Total indirect installment | Current
Financing Receivable, Credit Quality Indicator [Line Items]
2020	372
2019	260
2018	332
2017	147
2016	67
Prior	27
Revolving Loans Amortized Cost Basis	0
Total Loans and Leases	1,205
Total indirect installment | Past due
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1
2019	3
2018	4
2017	2
2016	2
Prior	1
Revolving Loans Amortized Cost Basis	0
Total Loans and Leases	13
Total consumer lines of credit
Financing Receivable, Credit Quality Indicator [Line Items]
2020	4
2019	7
2018	8
2017	3
2016	5
Prior	142
Revolving Loans Amortized Cost Basis	1,149
Total Loans and Leases	1,318	1,451
Total consumer lines of credit | Current
Financing Receivable, Credit Quality Indicator [Line Items]
2020	4
2019	7
2018	8
2017	3
2016	5
Prior	127
Revolving Loans Amortized Cost Basis	1,146
Total Loans and Leases	1,300
Total consumer lines of credit | Past due
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	15
Revolving Loans Amortized Cost Basis	3
Total Loans and Leases	18
Total consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	2,163
2019	1,320
2018	836
2017	678
2016	583
Prior	1,258
Revolving Loans Amortized Cost Basis	1,151
Total Loans and Leases	$ 7,989	$ 8,568

Loans and Leases - Summary of C

Loans and Leases - Summary of Commercial Loans and Leases by Credit Quality (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	$ 25,459	$ 23,289
Total commercial loans and leases
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	17,470	14,721
Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	9,731	8,960
Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	7,214	5,308
Commercial leases
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	485	432
Other
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	40	21
Originated Loans And Leases
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		20,397
Originated Loans And Leases | Total commercial loans and leases
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		12,630
Originated Loans And Leases | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		7,114
Originated Loans And Leases | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		5,063
Originated Loans And Leases | Commercial leases
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		432
Originated Loans And Leases | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		21
Acquired Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		2,892
Acquired Loans | Total commercial loans and leases
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		2,091
Acquired Loans | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		1,846
Acquired Loans | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		245
Pass | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	6,713
Pass | Commercial leases
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	459
Pass | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	39
Pass | Originated Loans And Leases | Total commercial loans and leases
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		12,032
Pass | Originated Loans And Leases | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		6,821
Pass | Originated Loans And Leases | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		4,768
Pass | Originated Loans And Leases | Commercial leases
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		423
Pass | Originated Loans And Leases | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		20
Pass | Acquired Loans | Total commercial loans and leases
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		1,804
Pass | Acquired Loans | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		1,603
Pass | Acquired Loans | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		201
Special Mention | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	218
Special Mention | Commercial leases
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	13
Special Mention | Originated Loans And Leases | Total commercial loans and leases
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		323
Special Mention | Originated Loans And Leases | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		171
Special Mention | Originated Loans And Leases | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		149
Special Mention | Originated Loans And Leases | Commercial leases
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		3
Special Mention | Originated Loans And Leases | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		0
Special Mention | Acquired Loans | Total commercial loans and leases
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		135
Special Mention | Acquired Loans | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		116
Special Mention | Acquired Loans | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		19
Substandard | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	283
Substandard | Commercial leases
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	13
Substandard | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	$ 1
Substandard | Originated Loans And Leases | Total commercial loans and leases
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		272
Substandard | Originated Loans And Leases | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		121
Substandard | Originated Loans And Leases | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		144
Substandard | Originated Loans And Leases | Commercial leases
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		6
Substandard | Originated Loans And Leases | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		1
Substandard | Acquired Loans | Total commercial loans and leases
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		152
Substandard | Acquired Loans | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		127
Substandard | Acquired Loans | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		25
Doubtful | Originated Loans And Leases | Total commercial loans and leases
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		3
Doubtful | Originated Loans And Leases | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		1
Doubtful | Originated Loans And Leases | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		2
Doubtful | Originated Loans And Leases | Commercial leases
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		0
Doubtful | Originated Loans And Leases | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		0
Doubtful | Acquired Loans | Total commercial loans and leases
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		0
Doubtful | Acquired Loans | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		0
Doubtful | Acquired Loans | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases		$ 0

Loans and Leases - Summary of_3

Loans and Leases - Summary of Consumer Loans by Payment Status (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Credit Quality [Line Items]
Total Loans and Leases	$ 25,459	$ 23,289
Direct installment
Credit Quality [Line Items]
Total Loans and Leases	2,020	1,821
Residential mortgages
Credit Quality [Line Items]
Total Loans and Leases	3,433	3,374
Indirect installment
Credit Quality [Line Items]
Total Loans and Leases	$ 1,218	1,922
Originated Loans And Leases
Credit Quality [Line Items]
Total Loans and Leases		20,397
Originated Loans And Leases | Direct installment
Credit Quality [Line Items]
Total Loans and Leases		1,758
Originated Loans And Leases | Residential mortgages
Credit Quality [Line Items]
Total Loans and Leases		2,995
Originated Loans And Leases | Indirect installment
Credit Quality [Line Items]
Total Loans and Leases		1,922
Acquired Loans
Credit Quality [Line Items]
Total Loans and Leases		2,892
Acquired Loans | Direct installment
Credit Quality [Line Items]
Total Loans and Leases		63
Acquired Loans | Residential mortgages
Credit Quality [Line Items]
Total Loans and Leases		379
Total consumer loans | Originated Loans And Leases
Credit Quality [Line Items]
Total Loans and Leases		7,767
Total consumer loans | Originated Loans And Leases | Performing
Credit Quality [Line Items]
Total Loans and Leases		7,728
Total consumer loans | Originated Loans And Leases | Non-Performing
Credit Quality [Line Items]
Total Loans and Leases		39
Total consumer loans | Originated Loans And Leases | Direct installment
Credit Quality [Line Items]
Total Loans and Leases		1,758
Total consumer loans | Originated Loans And Leases | Direct installment | Performing
Credit Quality [Line Items]
Total Loans and Leases		1,745
Total consumer loans | Originated Loans And Leases | Direct installment | Non-Performing
Credit Quality [Line Items]
Total Loans and Leases		13
Total consumer loans | Originated Loans And Leases | Residential mortgages
Credit Quality [Line Items]
Total Loans and Leases		2,995
Total consumer loans | Originated Loans And Leases | Residential mortgages | Performing
Credit Quality [Line Items]
Total Loans and Leases		2,978
Total consumer loans | Originated Loans And Leases | Residential mortgages | Non-Performing
Credit Quality [Line Items]
Total Loans and Leases		17
Total consumer loans | Originated Loans And Leases | Indirect installment
Credit Quality [Line Items]
Total Loans and Leases		1,922
Total consumer loans | Originated Loans And Leases | Indirect installment | Performing
Credit Quality [Line Items]
Total Loans and Leases		1,919
Total consumer loans | Originated Loans And Leases | Indirect installment | Non-Performing
Credit Quality [Line Items]
Total Loans and Leases		3
Total consumer loans | Originated Loans And Leases | Consumer lines of credit
Credit Quality [Line Items]
Total Loans and Leases		1,092
Total consumer loans | Originated Loans And Leases | Consumer lines of credit | Performing
Credit Quality [Line Items]
Total Loans and Leases		1,086
Total consumer loans | Originated Loans And Leases | Consumer lines of credit | Non-Performing
Credit Quality [Line Items]
Total Loans and Leases		6
Total consumer loans | Acquired Loans
Credit Quality [Line Items]
Total Loans and Leases		801
Total consumer loans | Acquired Loans | Performing
Credit Quality [Line Items]
Total Loans and Leases		800
Total consumer loans | Acquired Loans | Non-Performing
Credit Quality [Line Items]
Total Loans and Leases		1
Total consumer loans | Acquired Loans | Direct installment
Credit Quality [Line Items]
Total Loans and Leases		63
Total consumer loans | Acquired Loans | Direct installment | Performing
Credit Quality [Line Items]
Total Loans and Leases		63
Total consumer loans | Acquired Loans | Direct installment | Non-Performing
Credit Quality [Line Items]
Total Loans and Leases		0
Total consumer loans | Acquired Loans | Residential mortgages
Credit Quality [Line Items]
Total Loans and Leases		379
Total consumer loans | Acquired Loans | Residential mortgages | Performing
Credit Quality [Line Items]
Total Loans and Leases		379
Total consumer loans | Acquired Loans | Residential mortgages | Non-Performing
Credit Quality [Line Items]
Total Loans and Leases		0
Total consumer loans | Acquired Loans | Consumer lines of credit
Credit Quality [Line Items]
Total Loans and Leases		359
Total consumer loans | Acquired Loans | Consumer lines of credit | Performing
Credit Quality [Line Items]
Total Loans and Leases		358
Total consumer loans | Acquired Loans | Consumer lines of credit | Non-Performing
Credit Quality [Line Items]
Total Loans and Leases		$ 1

Loans and Leases - Age Analysis

Loans and Leases - Age Analysis of Past Due Loans, by Class (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Past Due [Line Items]
Total Loans and Leases	$ 25,459	$ 23,289
Total commercial loans and leases
Financing Receivable, Past Due [Line Items]
Total Loans and Leases	17,470	14,721
Commercial real estate
Financing Receivable, Past Due [Line Items]
Total Loans and Leases	9,731	8,960
Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total Loans and Leases	7,214	5,308
Commercial leases
Financing Receivable, Past Due [Line Items]
Total Loans and Leases	485	432
Other
Financing Receivable, Past Due [Line Items]
Total Loans and Leases	40	21
Total consumer loans
Financing Receivable, Past Due [Line Items]
Total Loans and Leases	7,989	8,568
Direct installment
Financing Receivable, Past Due [Line Items]
Total Loans and Leases	2,020	1,821
Residential mortgages
Financing Receivable, Past Due [Line Items]
Total Loans and Leases	3,433	3,374
Indirect installment
Financing Receivable, Past Due [Line Items]
Total Loans and Leases	1,218	1,922
Consumer lines of credit
Financing Receivable, Past Due [Line Items]
Total Loans and Leases	1,318	1,451
Loans and Leases
Financing Receivable, Past Due [Line Items]
Total Past Due	258
Non- Accrual	170
Current	25,201
Total Loans and Leases	25,459
Non-accrual with No ACL	52
Loans and Leases | Total commercial loans and leases
Financing Receivable, Past Due [Line Items]
Total Past Due	155
Non- Accrual	132
Current	17,315
Total Loans and Leases	17,470
Non-accrual with No ACL	52
Loans and Leases | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total Past Due	98
Non- Accrual	85
Current	9,633
Total Loans and Leases	9,731
Non-accrual with No ACL	36
Loans and Leases | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total Past Due	52
Non- Accrual	44
Current	7,162
Total Loans and Leases	7,214
Non-accrual with No ACL	16
Loans and Leases | Commercial leases
Financing Receivable, Past Due [Line Items]
Total Past Due	4
Non- Accrual	2
Current	481
Total Loans and Leases	485
Non-accrual with No ACL	0
Loans and Leases | Other
Financing Receivable, Past Due [Line Items]
Total Past Due	1
Non- Accrual	1
Current	39
Total Loans and Leases	40
Non-accrual with No ACL	0
Loans and Leases | Total consumer loans
Financing Receivable, Past Due [Line Items]
Total Past Due	103
Non- Accrual	38
Current	7,886
Total Loans and Leases	7,989
Non-accrual with No ACL	0
Loans and Leases | Direct installment
Financing Receivable, Past Due [Line Items]
Total Past Due	20
Non- Accrual	11
Current	2,000
Total Loans and Leases	2,020
Non-accrual with No ACL	0
Loans and Leases | Residential mortgages
Financing Receivable, Past Due [Line Items]
Total Past Due	52
Non- Accrual	18
Current	3,381
Total Loans and Leases	3,433
Non-accrual with No ACL	0
Loans and Leases | Indirect installment
Financing Receivable, Past Due [Line Items]
Total Past Due	13
Non- Accrual	2
Current	1,205
Total Loans and Leases	1,218
Non-accrual with No ACL	0
Loans and Leases | Consumer lines of credit
Financing Receivable, Past Due [Line Items]
Total Past Due	18
Non- Accrual	7
Current	1,300
Total Loans and Leases	1,318
Non-accrual with No ACL	0
Originated Loans And Leases
Financing Receivable, Past Due [Line Items]
Total Past Due		145
Non- Accrual		77
Current		20,252
Total Loans and Leases		20,397
Originated Loans And Leases | Total commercial loans and leases
Financing Receivable, Past Due [Line Items]
Total Past Due		80
Non- Accrual		56
Current		12,550
Total Loans and Leases		12,630
Originated Loans And Leases | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total Past Due		36
Non- Accrual		26
Current		7,078
Total Loans and Leases		7,114
Originated Loans And Leases | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total Past Due		37
Non- Accrual		28
Current		5,026
Total Loans and Leases		5,063
Originated Loans And Leases | Commercial leases
Financing Receivable, Past Due [Line Items]
Total Past Due		6
Non- Accrual		1
Current		426
Total Loans and Leases		432
Originated Loans And Leases | Other
Financing Receivable, Past Due [Line Items]
Total Past Due		1
Non- Accrual		1
Current		20
Total Loans and Leases		21
Originated Loans And Leases | Total consumer loans
Financing Receivable, Past Due [Line Items]
Total Past Due		65
Non- Accrual		21
Current		7,702
Total Loans and Leases		7,767
Originated Loans And Leases | Direct installment
Financing Receivable, Past Due [Line Items]
Total Past Due		15
Non- Accrual		7
Current		1,743
Total Loans and Leases		1,758
Originated Loans And Leases | Residential mortgages
Financing Receivable, Past Due [Line Items]
Total Past Due		22
Non- Accrual		8
Current		2,973
Total Loans and Leases		2,995
Originated Loans And Leases | Indirect installment
Financing Receivable, Past Due [Line Items]
Total Past Due		19
Non- Accrual		3
Current		1,903
Total Loans and Leases		1,922
Originated Loans And Leases | Consumer lines of credit
Financing Receivable, Past Due [Line Items]
Total Past Due		9
Non- Accrual		3
Current		1,083
Total Loans and Leases		1,092
Acquired Loans
Financing Receivable, Past Due [Line Items]
Total Past Due		73
Non- Accrual		4
Current		3,000
(Discount)/ Premium		(181)
Total Loans and Leases		2,892
Acquired Loans | Total commercial loans and leases
Financing Receivable, Past Due [Line Items]
Total Loans and Leases		2,091
Acquired Loans | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total Past Due		43
Non- Accrual		3
Current		1,942
(Discount)/ Premium		(139)
Total Loans and Leases		1,846
Acquired Loans | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total Past Due		5
Non- Accrual		0
Current		259
(Discount)/ Premium		(19)
Total Loans and Leases		245
Acquired Loans | Commercial loan
Financing Receivable, Past Due [Line Items]
Total Past Due		48
Non- Accrual		3
Current		2,201
(Discount)/ Premium		(158)
Total Loans and Leases		2,091
Acquired Loans | Total consumer loans
Financing Receivable, Past Due [Line Items]
Total Past Due		25
Non- Accrual		1
Current		799
(Discount)/ Premium		(23)
Total Loans and Leases		801
Acquired Loans | Direct installment
Financing Receivable, Past Due [Line Items]
Total Past Due		3
Non- Accrual		0
Current		60
(Discount)/ Premium		0
Total Loans and Leases		63
Acquired Loans | Residential mortgages
Financing Receivable, Past Due [Line Items]
Total Past Due		12
Non- Accrual		0
Current		382
(Discount)/ Premium		(15)
Total Loans and Leases		379
Acquired Loans | Consumer lines of credit
Financing Receivable, Past Due [Line Items]
Total Past Due		10
Non- Accrual		1
Current		357
(Discount)/ Premium		(8)
Total Loans and Leases		359
30-89 Days Past Due | Loans and Leases
Financing Receivable, Past Due [Line Items]
Total Past Due	72
30-89 Days Past Due | Loans and Leases | Total commercial loans and leases
Financing Receivable, Past Due [Line Items]
Total Past Due	23
30-89 Days Past Due | Loans and Leases | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total Past Due	13
30-89 Days Past Due | Loans and Leases | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total Past Due	8
30-89 Days Past Due | Loans and Leases | Commercial leases
Financing Receivable, Past Due [Line Items]
Total Past Due	2
30-89 Days Past Due | Loans and Leases | Other
Financing Receivable, Past Due [Line Items]
Total Past Due	0
30-89 Days Past Due | Loans and Leases | Total consumer loans
Financing Receivable, Past Due [Line Items]
Total Past Due	49
30-89 Days Past Due | Loans and Leases | Direct installment
Financing Receivable, Past Due [Line Items]
Total Past Due	7
30-89 Days Past Due | Loans and Leases | Residential mortgages
Financing Receivable, Past Due [Line Items]
Total Past Due	23
30-89 Days Past Due | Loans and Leases | Indirect installment
Financing Receivable, Past Due [Line Items]
Total Past Due	10
30-89 Days Past Due | Loans and Leases | Consumer lines of credit
Financing Receivable, Past Due [Line Items]
Total Past Due	9
30-89 Days Past Due | Originated Loans And Leases
Financing Receivable, Past Due [Line Items]
Total Past Due		63
30-89 Days Past Due | Originated Loans And Leases | Total commercial loans and leases
Financing Receivable, Past Due [Line Items]
Total Past Due		24
30-89 Days Past Due | Originated Loans And Leases | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total Past Due		10
30-89 Days Past Due | Originated Loans And Leases | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total Past Due		9
30-89 Days Past Due | Originated Loans And Leases | Commercial leases
Financing Receivable, Past Due [Line Items]
Total Past Due		5
30-89 Days Past Due | Originated Loans And Leases | Other
Financing Receivable, Past Due [Line Items]
Total Past Due		0
30-89 Days Past Due | Originated Loans And Leases | Total consumer loans
Financing Receivable, Past Due [Line Items]
Total Past Due		39
30-89 Days Past Due | Originated Loans And Leases | Direct installment
Financing Receivable, Past Due [Line Items]
Total Past Due		7
30-89 Days Past Due | Originated Loans And Leases | Residential mortgages
Financing Receivable, Past Due [Line Items]
Total Past Due		12
30-89 Days Past Due | Originated Loans And Leases | Indirect installment
Financing Receivable, Past Due [Line Items]
Total Past Due		15
30-89 Days Past Due | Originated Loans And Leases | Consumer lines of credit
Financing Receivable, Past Due [Line Items]
Total Past Due		5
30-89 Days Past Due | Acquired Loans
Financing Receivable, Past Due [Line Items]
Total Past Due		32
30-89 Days Past Due | Acquired Loans | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total Past Due		12
30-89 Days Past Due | Acquired Loans | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total Past Due		2
30-89 Days Past Due | Acquired Loans | Commercial loan
Financing Receivable, Past Due [Line Items]
Total Past Due		14
30-89 Days Past Due | Acquired Loans | Total consumer loans
Financing Receivable, Past Due [Line Items]
Total Past Due		18
30-89 Days Past Due | Acquired Loans | Direct installment
Financing Receivable, Past Due [Line Items]
Total Past Due		3
30-89 Days Past Due | Acquired Loans | Residential mortgages
Financing Receivable, Past Due [Line Items]
Total Past Due		8
30-89 Days Past Due | Acquired Loans | Consumer lines of credit
Financing Receivable, Past Due [Line Items]
Total Past Due		7
≥ 90 Days Past Due and Still Accruing | Loans and Leases
Financing Receivable, Past Due [Line Items]
Total Past Due	16
≥ 90 Days Past Due and Still Accruing | Loans and Leases | Total commercial loans and leases
Financing Receivable, Past Due [Line Items]
Total Past Due	0
≥ 90 Days Past Due and Still Accruing | Loans and Leases | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total Past Due	0
≥ 90 Days Past Due and Still Accruing | Loans and Leases | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total Past Due	0
≥ 90 Days Past Due and Still Accruing | Loans and Leases | Commercial leases
Financing Receivable, Past Due [Line Items]
Total Past Due	0
≥ 90 Days Past Due and Still Accruing | Loans and Leases | Other
Financing Receivable, Past Due [Line Items]
Total Past Due	0
≥ 90 Days Past Due and Still Accruing | Loans and Leases | Total consumer loans
Financing Receivable, Past Due [Line Items]
Total Past Due	16
≥ 90 Days Past Due and Still Accruing | Loans and Leases | Direct installment
Financing Receivable, Past Due [Line Items]
Total Past Due	2
≥ 90 Days Past Due and Still Accruing | Loans and Leases | Residential mortgages
Financing Receivable, Past Due [Line Items]
Total Past Due	11
≥ 90 Days Past Due and Still Accruing | Loans and Leases | Indirect installment
Financing Receivable, Past Due [Line Items]
Total Past Due	1
≥ 90 Days Past Due and Still Accruing | Loans and Leases | Consumer lines of credit
Financing Receivable, Past Due [Line Items]
Total Past Due	$ 2
≥ 90 Days Past Due and Still Accruing | Originated Loans And Leases
Financing Receivable, Past Due [Line Items]
Total Past Due		5
≥ 90 Days Past Due and Still Accruing | Originated Loans And Leases | Total commercial loans and leases
Financing Receivable, Past Due [Line Items]
Total Past Due		0
≥ 90 Days Past Due and Still Accruing | Originated Loans And Leases | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total Past Due		0
≥ 90 Days Past Due and Still Accruing | Originated Loans And Leases | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total Past Due		0
≥ 90 Days Past Due and Still Accruing | Originated Loans And Leases | Commercial leases
Financing Receivable, Past Due [Line Items]
Total Past Due		0
≥ 90 Days Past Due and Still Accruing | Originated Loans And Leases | Other
Financing Receivable, Past Due [Line Items]
Total Past Due		0
≥ 90 Days Past Due and Still Accruing | Originated Loans And Leases | Total consumer loans
Financing Receivable, Past Due [Line Items]
Total Past Due		5
≥ 90 Days Past Due and Still Accruing | Originated Loans And Leases | Direct installment
Financing Receivable, Past Due [Line Items]
Total Past Due		1
≥ 90 Days Past Due and Still Accruing | Originated Loans And Leases | Residential mortgages
Financing Receivable, Past Due [Line Items]
Total Past Due		2
≥ 90 Days Past Due and Still Accruing | Originated Loans And Leases | Indirect installment
Financing Receivable, Past Due [Line Items]
Total Past Due		1
≥ 90 Days Past Due and Still Accruing | Originated Loans And Leases | Consumer lines of credit
Financing Receivable, Past Due [Line Items]
Total Past Due		1
≥ 90 Days Past Due and Still Accruing | Acquired Loans
Financing Receivable, Past Due [Line Items]
Total Past Due		37
≥ 90 Days Past Due and Still Accruing | Acquired Loans | Commercial real estate
Financing Receivable, Past Due [Line Items]
Total Past Due		28
≥ 90 Days Past Due and Still Accruing | Acquired Loans | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total Past Due		3
≥ 90 Days Past Due and Still Accruing | Acquired Loans | Commercial loan
Financing Receivable, Past Due [Line Items]
Total Past Due		31
≥ 90 Days Past Due and Still Accruing | Acquired Loans | Total consumer loans
Financing Receivable, Past Due [Line Items]
Total Past Due		6
≥ 90 Days Past Due and Still Accruing | Acquired Loans | Direct installment
Financing Receivable, Past Due [Line Items]
Total Past Due		0
≥ 90 Days Past Due and Still Accruing | Acquired Loans | Residential mortgages
Financing Receivable, Past Due [Line Items]
Total Past Due		4
≥ 90 Days Past Due and Still Accruing | Acquired Loans | Consumer lines of credit
Financing Receivable, Past Due [Line Items]
Total Past Due		$ 2

Loans and Leases - Summary of N

Loans and Leases - Summary of Non-Performing Assets (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Troubled debt restructurings	$ 91	$ 56
Non-Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non- Accrual	170	81
Troubled debt restructurings	0	22
Total non-performing loans	170	103
Other real estate owned	10	26
Total non-performing assets	$ 180	$ 129
Non-performing loans / total loans and leases	0.67%	0.44%
Non-performing loans assets + 90 days past due + OREO / total loans and leases + OREO	0.77%	0.73%
Past due	90 days	90 days

Loans and Leases - Summary of P

Loans and Leases - Summary of Payment Status of Originated TDRs (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructurings ("TDRs")	$ 91	$ 56
Accruing
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructurings ("TDRs")	58	41
Non-accrual
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructurings ("TDRs")	$ 33	$ 15

Loans and Leases - Summary of T

Loans and Leases - Summary of Troubled Debt Restructurings by Class of Loans (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)Contract	Dec. 31, 2019USD ($)Contract
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | Contract	187	153
Pre-Modification Outstanding Recorded Investment	$ 29	$ 18
Post- Modification Outstanding Recorded Investment	$ 17	$ 15
Total commercial loans and leases
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | Contract	50	43
Pre-Modification Outstanding Recorded Investment	$ 20	$ 10
Post- Modification Outstanding Recorded Investment	$ 9	$ 8
Commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | Contract	30	20
Pre-Modification Outstanding Recorded Investment	$ 18	$ 5
Post- Modification Outstanding Recorded Investment	$ 8	$ 5
Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | Contract	19	23
Pre-Modification Outstanding Recorded Investment	$ 2	$ 5
Post- Modification Outstanding Recorded Investment	$ 1	$ 3
Other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | Contract	1	0
Pre-Modification Outstanding Recorded Investment	$ 0	$ 0
Post- Modification Outstanding Recorded Investment	$ 0	$ 0
Total consumer loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | Contract	137	110
Pre-Modification Outstanding Recorded Investment	$ 9	$ 8
Post- Modification Outstanding Recorded Investment	$ 8	$ 7
Direct installment
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | Contract	68	65
Pre-Modification Outstanding Recorded Investment	$ 4	$ 3
Post- Modification Outstanding Recorded Investment	$ 4	$ 3
Residential mortgages
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | Contract	24	18
Pre-Modification Outstanding Recorded Investment	$ 3	$ 3
Post- Modification Outstanding Recorded Investment	$ 3	$ 3
Consumer lines of credit
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | Contract	45	27
Pre-Modification Outstanding Recorded Investment	$ 2	$ 2
Post- Modification Outstanding Recorded Investment	$ 1	$ 1

Loans and Leases - Summary of O

Loans and Leases - Summary of Originated Troubled Debt Restructurings by Class of Loans and Leases, Payment Default (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)Contract	Dec. 31, 2019USD ($)Contract
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | Contract	30	14
Recorded Investment | $	$ 3	$ 1
Total commercial loans and leases
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | Contract	10	6
Recorded Investment | $	$ 3	$ 1
Commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | Contract	8	5
Recorded Investment | $	$ 3	$ 1
Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | Contract	2	1
Recorded Investment | $	$ 0	$ 0
Total consumer loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | Contract	20	8
Recorded Investment | $	$ 0	$ 0
Direct installment
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | Contract	12	5
Recorded Investment | $	$ 0	$ 0
Residential mortgages
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | Contract	4	2
Recorded Investment | $	$ 0	$ 0
Consumer lines of credit
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | Contract	4	1
Recorded Investment | $	$ 0	$ 0

Allowance for Credit Losses o_3

Allowance for Credit Losses on Loans and Leases - Changes in Allowance for Credit Losses (Detail) - USD ($) $ in Millions	Jan. 01, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Allowance for Loan and Lease Losses [Roll Forward]
Balance at Beginning of Period	$ 196	$ 196	$ 180	$ 175
Charge- Offs			(42)	(70)
Recoveries			14	14
Net Charge- Offs			(28)	(56)
Provision for Credit Losses			44	61
Balance at End of Period	196	363	196	180
Unfunded Loan Commitment
Allowance for Loan and Lease Losses [Roll Forward]
Balance at Beginning of Period	3	3
Charge- Offs		0
Recoveries		0
Net Charge- Offs		0
Provision for Credit Losses		1
ASC 326 Adoption Impact	10
Initial ACL on PCD Loans		0
Balance at End of Period		14	3
Originated Loans And Leases
Allowance for Loan and Lease Losses [Roll Forward]
Balance at Beginning of Period	189	189	173	168
Charge- Offs			(33)	(63)
Recoveries			12	11
Net Charge- Offs			(21)	(52)
Provision for Credit Losses			37	57
Balance at End of Period			189	173
Allowance for credit losses on loans and leases and allowance for unfunded loan commitments
Allowance for Loan and Lease Losses [Roll Forward]
Balance at Beginning of Period	199	199
Charge- Offs		(81)
Recoveries		21
Net Charge- Offs		(60)
Provision for Credit Losses		123
ASC 326 Adoption Impact	65
Initial ACL on PCD Loans		50
Balance at End of Period		377	199
Allowance for credit losses on loans and leases
Allowance for Loan and Lease Losses [Roll Forward]
Balance at Beginning of Period	196	196
Charge- Offs		(81)
Recoveries		21
Net Charge- Offs		(60)
Provision for Credit Losses		122
ASC 326 Adoption Impact	55
Initial ACL on PCD Loans		50
Balance at End of Period		363	196
Total commercial loans and leases
Allowance for Loan and Lease Losses [Roll Forward]
Balance at Beginning of Period	133	133
Charge- Offs		(68)
Recoveries		15
Net Charge- Offs		(53)
Provision for Credit Losses		119
ASC 326 Adoption Impact	37
Initial ACL on PCD Loans		44
Balance at End of Period		280	133
Total commercial loans and leases | Unfunded Loan Commitment
Allowance for Loan and Lease Losses [Roll Forward]
Provision for Credit Losses		1
ASC 326 Adoption Impact		8
Total commercial loans and leases | Originated Loans And Leases
Allowance for Loan and Lease Losses [Roll Forward]
Balance at Beginning of Period	126	126	114	109
Charge- Offs			(17)	(34)
Recoveries			8	5
Net Charge- Offs			(9)	(29)
Provision for Credit Losses			21	34
Balance at End of Period			126	114
Commercial real estate
Allowance for Loan and Lease Losses [Roll Forward]
Balance at Beginning of Period	60	60
Charge- Offs		(31)
Recoveries		7
Net Charge- Offs		(24)
Provision for Credit Losses		67
ASC 326 Adoption Impact	38
Initial ACL on PCD Loans		40
Balance at End of Period	60	181	60
Commercial real estate | Originated Loans And Leases
Allowance for Loan and Lease Losses [Roll Forward]
Balance at Beginning of Period	60	60	55	50
Charge- Offs			(4)	(7)
Recoveries			4	3
Net Charge- Offs			0	(4)
Provision for Credit Losses			5	9
Balance at End of Period			60	55
Commercial and industrial
Allowance for Loan and Lease Losses [Roll Forward]
Balance at Beginning of Period	53	53
Charge- Offs		(32)
Recoveries		7
Net Charge- Offs		(25)
Provision for Credit Losses		41
ASC 326 Adoption Impact	8
Initial ACL on PCD Loans		4
Balance at End of Period	53	81	53
Commercial and industrial | Originated Loans And Leases
Allowance for Loan and Lease Losses [Roll Forward]
Balance at Beginning of Period	53	53	49	52
Charge- Offs			(10)	(20)
Recoveries			4	2
Net Charge- Offs			(6)	(18)
Provision for Credit Losses			10	15
Balance at End of Period			53	49
Commercial leases
Allowance for Loan and Lease Losses [Roll Forward]
Balance at Beginning of Period	11	11
Charge- Offs		(1)
Recoveries		0
Net Charge- Offs		(1)
Provision for Credit Losses		7
ASC 326 Adoption Impact	0
Initial ACL on PCD Loans		0
Balance at End of Period	11	17	11
Commercial leases | Originated Loans And Leases
Allowance for Loan and Lease Losses [Roll Forward]
Balance at Beginning of Period	11	11	8	5
Charge- Offs			0	(3)
Recoveries			0	0
Net Charge- Offs			0	(3)
Provision for Credit Losses			3	6
Balance at End of Period			11	8
Other
Allowance for Loan and Lease Losses [Roll Forward]
Balance at Beginning of Period	9	9
Charge- Offs		(4)
Recoveries		1
Net Charge- Offs		(3)
Provision for Credit Losses		4
ASC 326 Adoption Impact	(9)
Initial ACL on PCD Loans		0
Balance at End of Period	9	1	9
Other | Originated Loans And Leases
Allowance for Loan and Lease Losses [Roll Forward]
Balance at Beginning of Period	2	2	2	2
Charge- Offs			(3)	(4)
Recoveries			0	0
Net Charge- Offs			(3)	(4)
Provision for Credit Losses			3	4
Balance at End of Period			2	2
Total consumer loans
Allowance for Loan and Lease Losses [Roll Forward]
Balance at Beginning of Period	63	63
Charge- Offs		(13)
Recoveries		6
Net Charge- Offs		(7)
Provision for Credit Losses		3
ASC 326 Adoption Impact	18
Initial ACL on PCD Loans		6
Balance at End of Period		83	63
Total consumer loans | Originated Loans And Leases
Allowance for Loan and Lease Losses [Roll Forward]
Balance at Beginning of Period	63	63	59	59
Charge- Offs			(16)	(29)
Recoveries			4	6
Net Charge- Offs			(12)	(23)
Provision for Credit Losses			16	23
Balance at End of Period			63	59
Direct installment
Allowance for Loan and Lease Losses [Roll Forward]
Balance at Beginning of Period	13	13
Charge- Offs		(1)
Recoveries		1
Net Charge- Offs		0
Provision for Credit Losses		2
ASC 326 Adoption Impact	10
Initial ACL on PCD Loans		1
Balance at End of Period	13	26	13
Direct installment | Originated Loans And Leases
Allowance for Loan and Lease Losses [Roll Forward]
Balance at Beginning of Period	13	13	14	21
Charge- Offs			(1)	(17)
Recoveries			0	2
Net Charge- Offs			(1)	(15)
Provision for Credit Losses			0	8
Balance at End of Period			13	14
Residential mortgages
Allowance for Loan and Lease Losses [Roll Forward]
Balance at Beginning of Period	22	22
Charge- Offs		(2)
Recoveries		1
Net Charge- Offs		(1)
Provision for Credit Losses		3
ASC 326 Adoption Impact	6
Initial ACL on PCD Loans		4
Balance at End of Period	22	34	22
Residential mortgages | Originated Loans And Leases
Allowance for Loan and Lease Losses [Roll Forward]
Balance at Beginning of Period	22	22	20	16
Charge- Offs			(2)	0
Recoveries			0	0
Net Charge- Offs			(2)	0
Provision for Credit Losses			4	4
Balance at End of Period			22	20
Indirect installment
Allowance for Loan and Lease Losses [Roll Forward]
Balance at Beginning of Period	19	19
Charge- Offs		(8)
Recoveries		4
Net Charge- Offs		(4)
Provision for Credit Losses		(6)
ASC 326 Adoption Impact	2
Initial ACL on PCD Loans		0
Balance at End of Period	19	11	19
Indirect installment | Originated Loans And Leases
Allowance for Loan and Lease Losses [Roll Forward]
Balance at Beginning of Period	19	19	15	12
Charge- Offs			(11)	(9)
Recoveries			4	4
Net Charge- Offs			(7)	(5)
Provision for Credit Losses			11	8
Balance at End of Period			19	15
Consumer lines of credit
Allowance for Loan and Lease Losses [Roll Forward]
Balance at Beginning of Period	9	9
Charge- Offs		(2)
Recoveries		0
Net Charge- Offs		(2)
Provision for Credit Losses		4
ASC 326 Adoption Impact	0
Initial ACL on PCD Loans		1
Balance at End of Period	9	12	9
Consumer lines of credit | Unfunded Loan Commitment
Allowance for Loan and Lease Losses [Roll Forward]
Provision for Credit Losses		0
ASC 326 Adoption Impact		2
Consumer lines of credit | Originated Loans And Leases
Allowance for Loan and Lease Losses [Roll Forward]
Balance at Beginning of Period	9	9	10	10
Charge- Offs			(2)	(3)
Recoveries			0	0
Net Charge- Offs			(2)	(3)
Provision for Credit Losses			1	3
Balance at End of Period			9	10
Loans acquired in a business combination | Acquired Loans
Allowance for Loan and Lease Losses [Roll Forward]
Balance at Beginning of Period	$ 7	$ 7	7	7
Charge- Offs			(9)	(7)
Recoveries			2	3
Net Charge- Offs			(7)	(4)
Provision for Credit Losses			7	4
Balance at End of Period			$ 7	$ 7

Allowance for Credit Losses o_4

Allowance for Credit Losses on Loans and Leases - Narrative (Details) - USD ($) $ in Millions	Jan. 01, 2020	Dec. 31, 2020	Dec. 31, 2019	Mar. 31, 2020	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Allowance for Credit Loss [Line Items]
Stockholders' equity attributable to parent		$ 4,959	$ 4,883		$ 4,608	$ 4,409
Financing receivable, allowance for credit loss, period increase (decrease)	$ 105.3	167.2
Allowance for credit loss	196	363	196		180	175
Percentage of growth, gross domestic product				4.00%
Percentage of increase, unemployment				6.00%
Allowance for credit loss, net		$ 363.1
Financing receivable, allowance for credit loss, period increase (decrease), percentage		85.40%
Financing receivable, allowance for credit loss, ratio		1.43%
Provision for credit losses		$ 122.8
Financing receivable, allowance for credit loss, write-off		$ 59.8	28.3
Financing receivable, allowance for credit loss, writeoff, net, basis points		0.0024
Impact of ASC 326 Adoption
Financing Receivable, Allowance for Credit Loss [Line Items]
Stockholders' equity attributable to parent			(50)
Allowance for credit loss	105
Retained Earnings
Financing Receivable, Allowance for Credit Loss [Line Items]
Stockholders' equity attributable to parent		$ 869	798		$ 576	$ 368
Retained Earnings | Impact of ASC 326 Adoption
Financing Receivable, Allowance for Credit Loss [Line Items]
Stockholders' equity attributable to parent			$ (50)
Accounting Standards Update 2016-13
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for credit loss	301
Accounting Standards Update 2016-13 | Retained Earnings
Financing Receivable, Allowance for Credit Loss [Line Items]
Stockholders' equity attributable to parent	(51)
Accounting Standards Update 2016-13 | Retained Earnings | Impact of ASC 326 Adoption
Financing Receivable, Allowance for Credit Loss [Line Items]
Stockholders' equity attributable to parent	(50.6)
Longer Duration Loans and Gross Up | Accounting Standards Update 2016-13
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing receivable, allowance for credit loss, period increase (decrease)	50
Unfunded Loan Commitment | Accounting Standards Update 2016-13
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing receivable, allowance for credit loss, period increase (decrease)	10
Allowance for credit loss	$ 10

Allowance for Credit Losses o_5

Allowance for Credit Losses on Loans and Leases - Summary of Individual and Collective Allowance for Credit Losses and Loan and Lease Balances by Class (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Valuation Allowance [Line Items]
Total Loans and Leases	$ 25,459	$ 23,289
Total commercial loans and leases
Valuation Allowance [Line Items]
Total Loans and Leases	17,470	14,721
Commercial real estate
Valuation Allowance [Line Items]
Total Loans and Leases	9,731	8,960
Commercial and industrial
Valuation Allowance [Line Items]
Total Loans and Leases	7,214	5,308
Commercial leases
Valuation Allowance [Line Items]
Total Loans and Leases	485	432
Other
Valuation Allowance [Line Items]
Total Loans and Leases	40	21
Total consumer loans
Valuation Allowance [Line Items]
Total Loans and Leases	7,989	8,568
Direct installment
Valuation Allowance [Line Items]
Total Loans and Leases	2,020	1,821
Residential mortgages
Valuation Allowance [Line Items]
Total Loans and Leases	3,433	3,374
Indirect installment
Valuation Allowance [Line Items]
Total Loans and Leases	1,218	1,922
Consumer lines of credit
Valuation Allowance [Line Items]
Total Loans and Leases	$ 1,318	1,451
Originated Loans And Leases
Valuation Allowance [Line Items]
Allowance, individually evaluated for impairment		4
Allowance, collectively evaluated for impairment		185
Total Loans and Leases		20,397
Loans and leases outstanding, individually evaluated for impairment		30
Loans and leases outstanding, collectively evaluated for impairment		20,367
Originated Loans And Leases | Total commercial loans and leases
Valuation Allowance [Line Items]
Allowance, individually evaluated for impairment		4
Allowance, collectively evaluated for impairment		122
Total Loans and Leases		12,630
Loans and leases outstanding, individually evaluated for impairment		30
Loans and leases outstanding, collectively evaluated for impairment		12,600
Originated Loans And Leases | Commercial real estate
Valuation Allowance [Line Items]
Allowance, individually evaluated for impairment		2
Allowance, collectively evaluated for impairment		58
Total Loans and Leases		7,114
Loans and leases outstanding, individually evaluated for impairment		13
Loans and leases outstanding, collectively evaluated for impairment		7,101
Originated Loans And Leases | Commercial and industrial
Valuation Allowance [Line Items]
Allowance, individually evaluated for impairment		2
Allowance, collectively evaluated for impairment		51
Total Loans and Leases		5,063
Loans and leases outstanding, individually evaluated for impairment		17
Loans and leases outstanding, collectively evaluated for impairment		5,046
Originated Loans And Leases | Commercial leases
Valuation Allowance [Line Items]
Allowance, individually evaluated for impairment		0
Allowance, collectively evaluated for impairment		11
Total Loans and Leases		432
Loans and leases outstanding, individually evaluated for impairment		0
Loans and leases outstanding, collectively evaluated for impairment		432
Originated Loans And Leases | Other
Valuation Allowance [Line Items]
Allowance, individually evaluated for impairment		0
Allowance, collectively evaluated for impairment		2
Total Loans and Leases		21
Loans and leases outstanding, individually evaluated for impairment		0
Loans and leases outstanding, collectively evaluated for impairment		21
Originated Loans And Leases | Total consumer loans
Valuation Allowance [Line Items]
Allowance, individually evaluated for impairment		0
Allowance, collectively evaluated for impairment		63
Total Loans and Leases		7,767
Loans and leases outstanding, individually evaluated for impairment		0
Loans and leases outstanding, collectively evaluated for impairment		7,767
Originated Loans And Leases | Direct installment
Valuation Allowance [Line Items]
Allowance, individually evaluated for impairment		0
Allowance, collectively evaluated for impairment		13
Total Loans and Leases		1,758
Loans and leases outstanding, individually evaluated for impairment		0
Loans and leases outstanding, collectively evaluated for impairment		1,758
Originated Loans And Leases | Residential mortgages
Valuation Allowance [Line Items]
Allowance, individually evaluated for impairment		0
Allowance, collectively evaluated for impairment		22
Total Loans and Leases		2,995
Loans and leases outstanding, individually evaluated for impairment		0
Loans and leases outstanding, collectively evaluated for impairment		2,995
Originated Loans And Leases | Indirect installment
Valuation Allowance [Line Items]
Allowance, individually evaluated for impairment		0
Allowance, collectively evaluated for impairment		19
Total Loans and Leases		1,922
Loans and leases outstanding, individually evaluated for impairment		0
Loans and leases outstanding, collectively evaluated for impairment		1,922
Originated Loans And Leases | Consumer lines of credit
Valuation Allowance [Line Items]
Allowance, individually evaluated for impairment		0
Allowance, collectively evaluated for impairment		9
Total Loans and Leases		1,092
Loans and leases outstanding, individually evaluated for impairment		0
Loans and leases outstanding, collectively evaluated for impairment		$ 1,092

Loan Servicing - Mortgage Servi

Loan Servicing - Mortgage Servicing Rights Activity (Details) - Mortgage Servicing Rights - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Servicing Assets at Fair Value [Line Items]
SBA loans sold to investors with servicing retained	$ 4,653	$ 4,686
Mortgage loans sold with servicing retained	1,636	1,381	$ 1,060
Pretax gains resulting from above loan sales	70	32	19
Mortgage banking operations	12	11	9
Valuation allowance for impairment of recognized servicing assets, balance	7.3	1.5
Servicing Asset at Amortized Cost, Balance [Roll Forward]
Balance at beginning of period	42.6	36.8	29.1
Additions	16	14.3	12.5
Payoffs and curtailments	(14.8)	(5)	(1.8)
(Impairment) charge / recovery	(5.8)	(1)	(0.5)
Amortization	(2.4)	(2.5)	(2.5)
Balance at end of period	35.6	42.6	36.8
Fair value, beginning of period	45.2	41.1	32.4
Fair value, end of period	$ 35.6	$ 45.2	$ 41.1

Loan Servicing - Sensitivity of

Loan Servicing - Sensitivity of Fair Value to Changes in key Assumptions (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Mortgage Servicing Rights
Servicing Assets at Fair Value [Line Items]
Weighted average life (months)	66 months 17 days	78 months 27 days
Constant prepayment rate (annualized)	13.40%	10.60%
Discount rate	9.50%	9.70%
Sensitivity analysis of fair value of interests continued to be held by transferor servicing assets or liabilities impact of zero point two five percent favorable change in prepayment speed	$ 2	$ 3
Sensitivity analysis of fair value of interests continued to be held by transferor servicing assets or liabilities impact of zero point five zero percent favorable change in prepayment speed	4	5
Sensitivity analysis of fair value of interests continued to be held by transferor servicing assets or liabilities impact of zero point two five percent adverse change in prepayment speed	(2)	(3)
Sensitivity analysis of fair value of interests continued to be held by transferor servicing assets or liabilities impact of zero point five zero percent adverse change in prepayment speed	$ (3)	$ (5)
SBA-Guaranteed Loan Servicing
Servicing Assets at Fair Value [Line Items]
Weighted average life (months)	38 months	42 months
Constant prepayment rate (annualized)	17.80%	16.80%
Discount rate	13.20%	16.20%
Sensitivity analysis of fair value, transferor's interests in transferred financial assets, impact of 1 percent adverse change in discount rate	$ (0.1)	$ (0.1)
Sensitivity analysis of fair value, transferor's interests in transferred financial assets, impact of 2 percent adverse change in discount rate	(0.1)	(0.1)
Sensitivity analysis of fair value, transferor's interests in transferred financial assets, impact of 10 percent adverse change in prepayment speed	(0.1)	(0.1)
Sensitivity analysis of fair value, transferor's interests in transferred financial assets, impact of 20 percent adverse change in prepayment speed	$ (0.1)	$ (0.3)

Loan Servicing - Activity in SB

Loan Servicing - Activity in SBA-Guaranteed Loan Servicing Asset (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Servicing Assets at Fair Value [Line Items]
Service charges		$ 108	$ 124	$ 126
Indirect Auto Loan
Servicing Assets at Fair Value [Line Items]
Mortgage loans sold with servicing retained	$ 500
Loan servicing rights	0.7	0.7
SBA-Guaranteed Loan Servicing
Servicing Assets at Fair Value [Line Items]
SBA loans sold to investors with servicing retained	217	217	225
Mortgage loans sold with servicing retained		33	23	41
Pretax gains resulting from above loan sales		3	2	4
Service charges		2	2	3
Valuation allowance for impairment of recognized servicing assets, balance	1.1	1.1	1.2
Servicing Asset at Fair Value, Amount [Roll Forward]
Balance at beginning of period		3	4	5
Additions		1	0	1
Payoffs, curtailments and amortization		(1)	(1)	(1)
Impairment charge		0	0	(1)
Balance at end of period	3	3	3	4
Fair value, beginning of period		3	4	5
Fair value, end of period	$ 3	$ 3	$ 3	$ 4

Premises and Equipment - Summar

Premises and Equipment - Summary of Premises and Equipment (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Land	$ 57	$ 62
Premises	231	233
Equipment	311	276
Property Plant and Equipment Gross	599	571
Accumulated depreciation	(267)	(238)
Total premises and equipment, net	$ 332	$ 333

Premises and Equipment - Deprec

Premises and Equipment - Depreciation Expense for Premises and Equipment (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Depreciation expense for premises and equipment	$ 43	$ 42	$ 39

Goodwill and Other Intangible_3

Goodwill and Other Intangible Assets - Rollforward of Goodwill (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Goodwill [Roll Forward]
Goodwill, beginning balance	$ 2,262	$ 2,255
Goodwill (deductions) additions	0	7
Goodwill, ending balance	2,262	2,262
Community Banking
Goodwill [Roll Forward]
Goodwill, beginning balance	2,231	2,231
Goodwill (deductions) additions	0	0
Goodwill, ending balance	2,231	2,231
Wealth Management
Goodwill [Roll Forward]
Goodwill, beginning balance	8	8
Goodwill (deductions) additions	0	0
Goodwill, ending balance	8	8
Insurance
Goodwill [Roll Forward]
Goodwill, beginning balance	23	16
Goodwill (deductions) additions	0	7
Goodwill, ending balance	$ 23	$ 23

Goodwill and Other Intangible_4

Goodwill and Other Intangible Assets - Summary of Core Deposit Intangibles, Customer Renewal Lists and Mortgage Servicing Rights (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 215	$ 214
Accumulated amortization	(161)	(147)
Net carrying amount	54	67
Core Deposit Intangibles
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	197	196
Accumulated amortization	(149)	(136)
Net carrying amount	48	60
Customer Renewal Lists
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	18	18
Accumulated amortization	(12)	(11)
Net carrying amount	$ 6	$ 7

Goodwill and Other Intangible_5

Goodwill and Other Intangible Assets - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2020
Minimum
Finite-Lived Intangible Assets [Line Items]
Amortization period of intangible assets, years	8 years
Maximum
Finite-Lived Intangible Assets [Line Items]
Amortization period of intangible assets, years	13 years
Core Deposit Intangibles
Finite-Lived Intangible Assets [Line Items]
Amortization period of intangible assets, years	10 years
Customer Renewal Lists | Minimum
Finite-Lived Intangible Assets [Line Items]
Amortization period of intangible assets, years	8 years
Customer Renewal Lists | Maximum
Finite-Lived Intangible Assets [Line Items]
Amortization period of intangible assets, years	13 years

Goodwill and Other Intangible_6

Goodwill and Other Intangible Assets - Schedule of Amortization Expense Recognized (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense	$ 13	$ 14	$ 16

Goodwill and Other Intangible_7

Goodwill and Other Intangible Assets - Schedule of Expected Amortization Expense on Finite-Lived Intangible Assets (Detail) $ in Millions	Dec. 31, 2020USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
2021	$ 12
2022	10
2023	10
2024	8
2025	7
Total	$ 47

Operating Leases - Other Inform

Operating Leases - Other Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2020
Leases [Abstract]
Right-of-use asset		$ 126.7
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]		us-gaap:OtherAssets
Operating lease liabilities		$ 134.4
Operating Lease, Liability, Statement of Financial Position [Extensible List]		us-gaap:OtherLiabilities
Operating lease, lease not yet commenced, expense		$ 18.2
Lessee, operating lease, lease not yet commenced, term of contract		16 years
Rental expense	$ 33.2

Operating Leases - Lease Expens

Operating Leases - Lease Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Operating lease cost	$ 27	$ 27
Short-term lease cost	1	1
Variable lease cost	3	4
Total lease cost	31	32
Operating cash flows from operating leases	26	26
Right-of-use assets obtained in exchange for lease obligations, Operating leases	$ 20	$ 25
Weighted average remaining lease term, Operating leases	9 years 5 months 12 days	9 years 7 months 9 days
Weighted average discount rate, Operating leases	2.60%	3.00%

Operating Leases - Maturities (

Operating Leases - Maturities (Details) $ in Millions	Dec. 31, 2020USD ($)
Leases [Abstract]
2021	$ 25
2022	21
2023	17
2024	15
2025	12
Later years	64
Total lease payments	154
Less: imputed interest	(20)
Present value of lease liabilities	$ 134.4

Variable Interest Entities - As

Variable Interest Entities - Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Variable Interest Entity [Line Items]
Total assets	$ 37,354	$ 34,615	$ 33,102
Liabilities	32,395	29,732
Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Total assets	146	154
Liabilities	119	136
Maximum Exposure to Loss	145	153
Trust Preferred Securities | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Total assets	1	1
Liabilities	66	66
Maximum Exposure to Loss	0	0
Affordable Housing Tax Credit Partnerships | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Total assets	119	120
Liabilities	45	60
Maximum Exposure to Loss	119	120
Other Investments | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Total assets	26	33
Liabilities	8	10
Maximum Exposure to Loss	$ 26	$ 33

Variable Interest Entities - Af

Variable Interest Entities - Affordable Housing Tax Credit Investments And Related Unfunded Commitments (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Proportional amortization method investments included in other assets	$ 71	$ 55
Equity method investments included in other assets	3	5
Total LIHTC investments included in other assets	74	60
Unfunded LIHTC commitments	$ 45	$ 60

Variable Interest Entities - In

Variable Interest Entities - Income Statement Effect (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Non-Interest Income
Amortization of tax credit investments under equity method, net of tax benefit	$ 1	$ 1	$ 2
Provision for income taxes:
Amortization of LIHTC investments under proportional method	11	8	5
Low-income housing tax credits	(12)	(9)	(6)
Other tax benefits related to tax credit investments	(2)	(2)	(1)
Total provision for income taxes	$ (3)	$ (3)	$ (2)

Deposits - Summary of Deposits

Deposits - Summary of Deposits (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Deposits [Abstract]
Non-interest-bearing demand	$ 9,042	$ 6,384
Interest-bearing demand	13,157	11,049
Savings	3,261	2,625
Less than $100,000	1,895	2,262
$100,000 through $250,000	1,173	1,494
Greater than $250,000	594	972
Total certificates and other time deposits	3,662	4,728
Total Deposits	$ 29,122	$ 24,786

Deposits - Summary of Scheduled

Deposits - Summary of Scheduled Maturities of Certificates and Other Time Deposits (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Deposits [Abstract]
2021	$ 2,464
2022	683
2023	236
2024	124
2025	99
Later years	56
Total certificates and other time deposits	$ 3,662	$ 4,728

Short-Term Borrowings - Summary

Short-Term Borrowings - Summary of Short-Term Borrowings (Detail) - USD ($)	6 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Debt Disclosure [Abstract]
Securities sold under repurchase agreements	$ 403,000,000	$ 278,000,000
Federal Home Loan Bank advances	1,280,000,000	2,255,000,000
Federal funds purchased	0	575,000,000
Subordinated notes	121,000,000	108,000,000
Total short-term borrowings	1,804,000,000	3,216,000,000
Short-term advances, overnight maturities	0	0
Short-term advances, swapped to a fixed rate	$ 1,300,000,000	$ 1,500,000,000
Short-term advances, swapped to a fixed rate, percentage bearing fixed interest rate	100.00%	64.50%
FHLB
Debt Instrument [Line Items]
Reduction of higher rate outstanding	$ 225,000,000
Hedge termination costs	$ 8,900,000

Short-Term Borrowings - Schedul

Short-Term Borrowings - Schedule of Weighted Average Interest Rates on Short-Term Borrowings (Detail)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Debt Disclosure [Abstract]
Year-to-date average	1.53%	2.24%	1.89%
Period-end	1.57%	1.76%	2.49%

Long-Term Borrowings - Summary

Long-Term Borrowings - Summary of Long-Term Borrowings (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Debt Disclosure [Abstract]
Federal Home Loan Bank advances	$ 400	$ 935
Senior notes	299	0
Subordinated notes	81	90
Junior subordinated debt	66	66
Other subordinated debt	249	249
Total long-term borrowings	$ 1,095	$ 1,340

Long-Term Borrowings - Schedule

Long-Term Borrowings - Scheduled Annual Maturities for Long-Term Borrowings (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Debt Disclosure [Abstract]
2021	$ 427
2022	16
2023	334
2024	1
2025	104
Later years	213
Total long-term borrowings	$ 1,095	$ 1,340

Long-Term Borrowings - Addition

Long-Term Borrowings - Additional Information (Detail)	3 Months Ended	6 Months Ended		12 Months Ended
	Mar. 31, 2020USD ($)	Dec. 31, 2020USD ($)Trust	Jun. 30, 2019USD ($)	Dec. 31, 2020USD ($)Trust	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Debt Instrument [Line Items]
Loss on debt extinguishment				$ (17,000,000)	$ 0	$ 0
Number of unconsolidated subsidiary trusts | Trust		3		3
Percent of the common equity of each Trust owned by the Corporation		100.00%		100.00%
Repayments of long-term debt				$ 574,000,000	$ 239,000,000	$ 77,000,000
Aggregate principal amount issued		$ 558,000,000		558,000,000
Proceeds from debt, net of issuance costs				560,000,000
Repayments of subordinated debt			$ 9,500,000
Repayments of other long-term debt			15,500,000
2.20% Senior Notes due February 24, 2023
Debt Instrument [Line Items]
Aggregate principal amount issued	$ 300,000,000	300,000,000		300,000,000
Proceeds from debt, net of issuance costs	$ 297,900,000			298,000,000
4.95% Fixed-To-Floating Rate Subordinated Notes due 2029
Debt Instrument [Line Items]
Aggregate principal amount issued		120,000,000		120,000,000
Proceeds from debt, net of issuance costs				$ 118,000,000
4.95% Fixed-To-Floating Rate Subordinated Notes due 2029 | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis points				2.40%
FHLB
Debt Instrument [Line Items]
Credit available with FHLB		8,300,000,000		$ 8,300,000,000
Credit with FHLB used		1,700,000,000		$ 1,700,000,000
Reduction of higher rate outstanding		490,000,000
Loss on debt extinguishment		$ 16,700,000
Subordinated Notes
Debt Instrument [Line Items]
Written notice for holder				30 days
Minimum | FHLB
Debt Instrument [Line Items]
Effective interest rates		0.30%		0.30%	1.62%
Minimum | Subordinated Notes
Debt Instrument [Line Items]
Months prior to maturity, interest discount				3 months
Maximum | FHLB
Debt Instrument [Line Items]
Effective interest rates		0.34%		0.34%	2.71%
Maximum | Subordinated Notes
Debt Instrument [Line Items]
Months prior to maturity, interest discount				12 months
Trust Preferred Securities
Debt Instrument [Line Items]
Repayments of long-term debt			$ 44,000,000

Long-Term Borrowings - Summar_2

Long-Term Borrowings - Summary of Weighted Average Interest Rate on Subordinated Notes (Detail)	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Debt Disclosure [Abstract]
Subordinated notes weighted average interest rate	3.23%	3.33%	3.08%

Long-Term Borrowings - Junior S

Long-Term Borrowings - Junior Subordinated Debt Trusts (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Subordinated Borrowing [Line Items]
Junior subordinated debt	$ 66	$ 66
Trust Preferred Securities
Subordinated Borrowing [Line Items]
Junior subordinated debt	72
Common Securities
Subordinated Borrowing [Line Items]
Junior subordinated debt	3
F.N.B. Statutory Trust II
Subordinated Borrowing [Line Items]
Junior subordinated debt	$ 22
Interest Rate	1.87%
Basis points	1.65%
F.N.B. Statutory Trust II | Trust Preferred Securities
Subordinated Borrowing [Line Items]
Junior subordinated debt	$ 22
F.N.B. Statutory Trust II | Common Securities
Subordinated Borrowing [Line Items]
Junior subordinated debt	1
Yadkin Valley Statutory Trust I
Subordinated Borrowing [Line Items]
Junior subordinated debt	$ 22
Interest Rate	1.54%
Basis points	1.32%
Yadkin Valley Statutory Trust I | Trust Preferred Securities
Subordinated Borrowing [Line Items]
Junior subordinated debt	$ 25
Yadkin Valley Statutory Trust I | Common Securities
Subordinated Borrowing [Line Items]
Junior subordinated debt	1
FNB Financial Services Capital Trust I
Subordinated Borrowing [Line Items]
Junior subordinated debt	$ 22
Interest Rate	1.70%
Basis points	1.46%
FNB Financial Services Capital Trust I | Trust Preferred Securities
Subordinated Borrowing [Line Items]
Junior subordinated debt	$ 25
FNB Financial Services Capital Trust I | Common Securities
Subordinated Borrowing [Line Items]
Junior subordinated debt	$ 1

Long-Term Borrowings - Schedu_2

Long-Term Borrowings - Schedule of Subordinated Debt (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2020
Debt Instrument [Line Items]
Aggregate principal amount issued		$ 558,000,000
Net proceeds		560,000,000
Carrying value		548,000,000
2.20% Senior Notes due February 24, 2023
Debt Instrument [Line Items]
Aggregate principal amount issued	$ 300,000,000	300,000,000
Net proceeds	$ 297,900,000	298,000,000
Carrying value		$ 299,000,000
Interest Rate		2.20%
4.95% Fixed-To-Floating Rate Subordinated Notes due 2029
Debt Instrument [Line Items]
Aggregate principal amount issued		$ 120,000,000
Net proceeds		118,000,000
Carrying value		$ 119,000,000
Interest Rate		4.95%
4.875% Subordinated Notes due 2025
Debt Instrument [Line Items]
Aggregate principal amount issued		$ 100,000,000
Net proceeds		98,000,000
Carrying value		$ 99,000,000
Interest Rate		4.875%
7.625% Subordinated Notes due August 12, 2013 | Yadkin Financial Corporation (YDKN)
Debt Instrument [Line Items]
Aggregate principal amount issued		$ 38,000,000
Net proceeds		46,000,000
Carrying value		$ 31,000,000
Interest Rate		7.625%

Derivative Instruments and He_3

Derivative Instruments and Hedging Activities - Schedule of Notional Amounts and Gross Fair Values of Derivative Assets and Derivative Liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Sep. 30, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Notional amount	$ 12,480		$ 9,558
Derivative asset, fair value, amount not offset against collateral	3		1
Derivative liability, fair value, amount not offset against collateral	37		23
Derivative asset, not subject to master netting arrangement	373		153
Derivative liability, not subject to master netting arrangement	3		2
Derivative asset	376		154
Derivative liabilities	40		25
Interest rate contracts
Derivatives, Fair Value [Line Items]
Notional amount		$ 225
Derivative asset, fair value, amount not offset against collateral	3		1
Derivative liability, fair value, amount not offset against collateral	0		0
Interest Rate Swap
Derivatives, Fair Value [Line Items]
Derivative asset, fair value, amount not offset against collateral	0		0
Derivative liability, fair value, amount not offset against collateral	37		23
Derivative asset, not subject to master netting arrangement	349		149
Derivative liability, not subject to master netting arrangement	0		1
Interest Rate Lock Commitments
Derivatives, Fair Value [Line Items]
Derivative asset, not subject to master netting arrangement	24		3
Derivative liability, not subject to master netting arrangement	0		0
Forward Delivery Commitments
Derivatives, Fair Value [Line Items]
Derivative asset, not subject to master netting arrangement	0		1
Derivative liability, not subject to master netting arrangement	2		1
Credit Risk Contracts
Derivatives, Fair Value [Line Items]
Notional amount	294.4
Derivative asset, not subject to master netting arrangement	0		0
Derivative liability, not subject to master netting arrangement	1		0
Subject to Master Netting Arrangement
Derivatives, Fair Value [Line Items]
Notional amount	6,221		5,295
Subject to Master Netting Arrangement | Interest rate contracts
Derivatives, Fair Value [Line Items]
Notional amount	1,430		1,655
Subject to Master Netting Arrangement | Interest Rate Swap
Derivatives, Fair Value [Line Items]
Notional amount	4,791		3,640
Not Subject to Master Netting Arrangement
Derivatives, Fair Value [Line Items]
Notional amount	6,259		4,263
Not Subject to Master Netting Arrangement | Interest Rate Swap
Derivatives, Fair Value [Line Items]
Notional amount	4,791		3,640
Not Subject to Master Netting Arrangement | Interest Rate Lock Commitments
Derivatives, Fair Value [Line Items]
Notional amount	531		163
Not Subject to Master Netting Arrangement | Forward Delivery Commitments
Derivatives, Fair Value [Line Items]
Notional amount	500		195
Not Subject to Master Netting Arrangement | Credit Risk Contracts
Derivatives, Fair Value [Line Items]
Notional amount	$ 437		$ 265

Derivative Instruments and He_4

Derivative Instruments and Hedging Activities - Amounts Reclassified from AOCI (Details) - Interest rate contracts - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Amount of Gain (Loss) Recognized in OCI on Derivatives	$ (51,000,000)	$ (22,000,000)	$ (3,000,000)
Amount of Gain (Loss) Reclassified from AOCI into Income	0	0
Interest income (expense)
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Amount of Gain (Loss) Reclassified from AOCI into Income	(14,000,000)	2,000,000	2,000,000
Other income
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Amount of Gain (Loss) Reclassified from AOCI into Income	$ (9,000,000)	$ 0	$ 0

Derivative Instruments and He_5

Derivative Instruments and Hedging Activities - Effect of Cash Flow Hedging on Income Statement (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Loans and leases, including fees	$ 990,000,000	$ 1,085,000,000	$ 1,022,000,000
Interest Expense - Short-term borrowings	38,000,000	80,000,000	75,000,000
Interest rate contracts
Derivative [Line Items]
Amount of gain (loss) reclassified from AOCI into net income	0	0
Interest income – loans and leases | Interest rate contracts
Derivative [Line Items]
Amount of gain (loss) reclassified from AOCI into net income	(7,000,000)	(1,000,000)	(1,000,000)
Amount of gain (loss) reclassified from AOCI into income as a result that a forecasted transaction is no longer probable of occurring	0	0	0
Interest expense – short-term borrowings | Interest rate contracts
Derivative [Line Items]
Amount of gain (loss) reclassified from AOCI into net income	(16,000,000)	3,000,000	3,000,000
Amount of gain (loss) reclassified from AOCI into income as a result that a forecasted transaction is no longer probable of occurring	0	$ 0	$ 0
Interest income - other non-interest income | Interest rate contracts
Derivative [Line Items]
Amount of gain (loss) reclassified from AOCI into net income	$ 8,900,000

Derivative Instruments and He_6

Derivative Instruments and Hedging Activities - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Sep. 30, 2020
Derivative [Line Items]
Notional amount	$ 12,480,000,000	$ 9,558,000,000
Additional amount in excess of posted collateral required in case of breached agreements	$ 300,000	100,000
Interest rate contracts
Derivative [Line Items]
Maximum length of time hedged in interest rate cash flow hedge	3 years 10 months 24 days
Period to reclassification of cash flow hedge gain loss	12 months
Derivative gains to be reclassified within twelve months	$ 18,800,000
Derivative gains to be reclassified within twelve months, net of tax	14,700,000
Notional amount			$ 225,000,000
Hedge ineffectiveness	0
Amount of gain (loss) reclassified from AOCI into net income	$ 0	0
Interest Rate Lock Commitments | Minimum
Derivative [Line Items]
Lock in period for interest rates	30 days
Interest Rate Lock Commitments | Maximum
Derivative [Line Items]
Lock in period for interest rates	270 days
Credit Risk Contracts
Derivative [Line Items]
Notional amount	$ 294,400,000
Maximum exposure under credit risk agreement assuming customer default	600,000	300,000
Credit risk derivatives, purchased at fair value	200,000	100,000
Credit risk derivatives, sold at fair value	$ 600,000	$ 300,000
Credit Risk Contracts | Minimum
Derivative [Line Items]
Risk participation agreements, term	1 month
Credit Risk Contracts | Maximum
Derivative [Line Items]
Risk participation agreements, term	20 years

Derivative Instruments and He_7

Derivative Instruments and Hedging Activities - Effect of Derivative Financial Instruments on Income Statement (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Interest Rate Swap | Non-interest income - other
Derivative [Line Items]
Derivative financial instrument, net	$ 0	$ 0	$ 1
Interest Rate Lock Commitments | Mortgage banking operations
Derivative [Line Items]
Derivative financial instrument, net	0	0	0
Forward Delivery Commitments | Mortgage banking operations
Derivative [Line Items]
Derivative financial instrument, net	(2)	(1)	1
Credit Risk Contracts | Non-interest income - other
Derivative [Line Items]
Derivative financial instrument, net	$ 0	$ 0	$ 0

Derivative Instruments and He_8

Derivative Instruments and Hedging Activities - Derivative Assets (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Derivative [Line Items]
Net Amount Presented in the Balance Sheet	$ 3	$ 1
Gross amounts not offset in the consolidated balance sheets financial instruments, derivative assets	0	1
Gross amounts not offset in the consolidated balance sheets cash collateral received, derivative assets	3	0
Net Amount	0	0
Interest rate contracts
Derivative [Line Items]
Net Amount Presented in the Balance Sheet	3	1
Gross amounts not offset in the consolidated balance sheets financial instruments, derivative assets	0	1
Gross amounts not offset in the consolidated balance sheets cash collateral received, derivative assets	3	0
Net Amount	0	0
Interest rate contracts
Derivative [Line Items]
Net Amount Presented in the Balance Sheet	$ 0	$ 0

Derivative Instruments and He_9

Derivative Instruments and Hedging Activities - Derivative Liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Derivative [Line Items]
Net Amount Presented in the Balance Sheet	$ 37	$ 23
Gross amount not offset in the balance sheet financial instruments, derivative liabilities	0	23
Gross amount not offset in the balance sheet cash collateral pledged, derivative liabilities	37	0
Net Amount	0	0
Interest rate contracts
Derivative [Line Items]
Net Amount Presented in the Balance Sheet	37	23
Gross amount not offset in the balance sheet financial instruments, derivative liabilities	0	23
Gross amount not offset in the balance sheet cash collateral pledged, derivative liabilities	37	0
Net Amount	0	0
Interest rate contracts
Derivative [Line Items]
Net Amount Presented in the Balance Sheet	$ 0	$ 0

Commitments, Credit Risk and _3

Commitments, Credit Risk and Contingencies - Summary of Off-Balance Sheet Credit Risk Information (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Standby letters of credit
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Extended credit and standby letters of credit	$ 158	$ 150
Commitments to extend credit
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Extended credit and standby letters of credit	$ 9,285	$ 8,089

Commitments, Credit Risk and _4

Commitments, Credit Risk and Contingencies - Additional Information (Detail) $ in Millions	Dec. 31, 2020USD ($)
Commitments and Contingencies Disclosure [Abstract]
Percentage of commitments to extend credit dependent upon the financial condition of the customers	75.20%
Allowance for credit losses on loan commitments that are not unconditionally cancellable	$ 13.7

Stock Incentive Plans - Additio

Stock Incentive Plans - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of awards issued, years	3 years
Common stock shares available up to (in shares)	5,504,721
Common stock additional shares registered (in shares)				4,640,000
Unrecognized compensation expense	$ 11,000,000
Increase (decrease) in stock compensation expense	$ 5,000,000
Increase (decrease) in stock compensation expense, percentage	44.00%
Performance period of units, years	3 years
Intrinsic value of outstanding and exercisable stock options	$ 300,000
Warrants outstanding	$ 0
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock awards issued (in shares)	2,004,895	1,182,197	962,799
Unrecognized compensation expense	$ 11,000,000
Amount subject to accelerated vesting under Incentive Compensation Plan	$ 600,000
2020 Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of awards issued, years	36 months
Service- Based Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of awards issued, years	3 years
Unrecognized compensation expense	$ 9,000,000
Performance- Based Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense	$ 2,000,000
Performance- Based Units | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock awards issued (in shares)	571,932	353,656

Stock Incentive Plans - Summary

Stock Incentive Plans - Summary of Information Concerning Restricted Stock Units (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Units
Shares, unvested shares outstanding at end of year (in shares)	4,322,115
Restricted Stock
Units
Shares, unvested shares outstanding at beginning of year (in shares)	2,858,357	2,556,174	1,975,862
Shares, granted (in shares)	2,004,895	1,182,197	962,799
Shares, net adjustment due to performance (in shares)	47,290	0	0
Shares, vested (in shares)	(613,581)	(655,208)	(258,031)
Shares, forfeited/expired (in shares)	(203,058)	(332,814)	(214,743)
Shares, dividend reinvestment (in shares)	228,212	108,008	90,287
Shares, unvested shares outstanding at end of year (in shares)	4,322,115	2,858,357	2,556,174
Weighted Average Grant Price per Share
Weighted average grant price per share, unvested shares outstanding at beginning of year (USD per share)	$ 12.56	$ 13.51	$ 13.64
Weighted average grant price per share, granted (USD per share)	6.95	10.94	13.21
Weighted average grant price per share, net adjustment due to performance (USD per share)	13	0	0
Weighted average grant price per share, vested (USD per share)	14.41	13.15	13.19
Weighted average grant price per share, forfeited/expired (USD per share)	12.54	12.72	13.39
Weighted average grant price per share, dividend reinvestment (USD per share)	8.14	11.84	12.61
Weighted average grant price per share, unvested shares outstanding at end of year (USD per share)	$ 9.46	$ 12.56	$ 13.51

Stock Incentive Plans - Schedul

Stock Incentive Plans - Schedule of Certain Information Related to Restricted Stock Units (Detail) - Restricted Stock - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 16	$ 12	$ 10
Tax benefit related to stock-based compensation expense	3	2	2
Fair value of units vested	$ 5	$ 7	$ 3

Stock Incentive Plans - Compone

Stock Incentive Plans - Components of Restricted Stock Units (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested restricted stock awards (in shares) | shares	4,322,115
Unrecognized compensation expense	$ 11
Intrinsic value	$ 41
Weighted average remaining life (in years)	1 year 6 months 14 days
Service- Based Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested restricted stock awards (in shares) | shares	2,983,059
Unrecognized compensation expense	$ 9
Intrinsic value	$ 28
Weighted average remaining life (in years)	1 year 8 months 19 days
Performance- Based Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested restricted stock awards (in shares) | shares	1,339,056
Unrecognized compensation expense	$ 2
Intrinsic value	$ 13
Weighted average remaining life (in years)	1 year 1 month 28 days

Stock Incentive Plans - Summa_2

Stock Incentive Plans - Summary of Activity Related to Stock Options Units (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Options Outstanding and Exercisable
Shares, options outstanding at beginning of year (in shares)	246,084	458,354	722,650
Shares, exercised (in shares)	(33,945)	(183,566)	(253,899)
Shares, forfeited/expired (in shares)	(16,053)	(28,704)	(10,397)
Shares, options outstanding and exercisable at end of year (in shares)	196,086	246,084	458,354
Weighted Average Exercise Price per Share
Weighted average price per share, options outstanding at beginning of year (USD per share)	$ 8.14	$ 7.99	$ 7.96
Weighted average price per share, exercised (USD per share)	5.74	7.86	7.77
Weighted average price per share, forfeited/expired (USD per share)	7.38	7.65	11.98
Weighted average price per share, options outstanding and exercisable at end of year (USD per share)	$ 8.61	$ 8.14	$ 7.99

Stock Incentive Plans - Summa_3

Stock Incentive Plans - Summary of Stock Options Outstanding (Detail)	12 Months Ended
	Dec. 31, 2020$ / sharesshares
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Options Outstanding and Exercisable (in shares) | shares	196,086
$3.57 - $5.36
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Range of Exercise Prices, Minimum (USD per share)	$ 3.57
Range of Exercise Prices, Maximum (USD per share)	$ 5.36
Options Outstanding and Exercisable (in shares) | shares	26,216
Weighted Average Remaining Contractual Years	8 months 19 days
Weighted Average Exercise Price (USD per share)	$ 4.93
$5.37 - $8.05
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Range of Exercise Prices, Minimum (USD per share)	5.37
Range of Exercise Prices, Maximum (USD per share)	$ 8.05
Options Outstanding and Exercisable (in shares) | shares	39,667
Weighted Average Remaining Contractual Years	2 years 1 month 13 days
Weighted Average Exercise Price (USD per share)	$ 6.91
$8.06 - $11.37
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Range of Exercise Prices, Minimum (USD per share)	8.06
Range of Exercise Prices, Maximum (USD per share)	$ 11.37
Options Outstanding and Exercisable (in shares) | shares	130,203
Weighted Average Remaining Contractual Years	3 years 9 months 18 days
Weighted Average Exercise Price (USD per share)	$ 9.87

Retirement Plans - Additional I

Retirement Plans - Additional Information (Detail) $ in Millions	Jan. 01, 2021	Jun. 30, 2018USD ($)	Dec. 31, 2020USD ($)Retirement_Planshares	Dec. 31, 2019USD ($)shares	Dec. 31, 2018USD ($)	Dec. 31, 2008
Retirement Plans [Line Items]
Corporation contribution		$ 0.9	$ 7	$ 7
Number of supplemental non-qualified retirement plans sponsored by the Corporation | Retirement_Plan			2
Consecutive calendar years used to calculate BRP benefits						5 years
Term of employment for consideration of BRP						10 years
Percentage of non callable corporate bonds			A yield curve was produced for a universe containing the majority of U.S.-issued Aa-graded corporate bonds, all of which were non-callable (or callable with make-whole provisions), and after excluding the 10% of the bonds with the highest and lowest yields.
Expected long-term rate of return on assets			7.25%	7.25%	7.25%
Benefits paid			$ 11	$ 12
Percent of employer match			100.00%
Employee contribution percentage			6.00%
Additional discretionary contribution, annual financial goals, percentage			3.00%
Dividends received on common stock			$ 0.2	$ 0.2
Subsequent Event
Retirement Plans [Line Items]
Expected long-term rate of return on assets	6.75%
Common Stock
Retirement Plans [Line Items]
Common stock, shares (in shares) | shares			450,000	469,000
Percentage of common stock on total plan assets			2.10%	3.50%
Qualified Pension Plans
Retirement Plans [Line Items]
Benefits paid			$ 10	$ 10
Non Qualified Pension Plans
Retirement Plans [Line Items]
Benefits paid			1.5	1.5
Retirement Income Plan (RIP)
Retirement Plans [Line Items]
Corporation contribution			$ 5	$ 5	$ 4

Retirement Plans - Schedule of

Retirement Plans - Schedule of Accumulated Benefit Obligation, Change in Benefit Obligation, Change in Plan Assets, Plans' Funded Status and Amount Included in Consolidated Balance Sheets (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Jun. 30, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Benefit Obligation
Accumulated benefit obligation		$ 187	$ 175
Projected benefit obligation at beginning of year		175	163
Interest cost		6	7	$ 6
Actuarial loss (gain)		17	17
Benefits paid		(11)	(12)
Projected benefit obligation at end of year		187	175	163
Fair Value of Plan Assets
Fair value of plan assets at beginning of year		173	150
Actual return on plan assets		20	28
Corporation contribution	$ 0.9	7	7
Benefits paid		(11)	(12)
Fair value of plan assets at end of year		189	173	150
Funded status of plans		2	(2)
Qualified Pension Plans
Benefit Obligation
Accumulated benefit obligation		167	156
Projected benefit obligation at beginning of year		156	145
Interest cost		5	6
Actuarial loss (gain)		15	15
Benefits paid		(9)	(10)
Projected benefit obligation at end of year		167	156	145
Fair Value of Plan Assets
Fair value of plan assets at beginning of year		173	150
Actual return on plan assets		20	28
Corporation contribution		5	5
Benefits paid		(9)	(10)
Fair value of plan assets at end of year		189	173	150
Funded status of plans		22	17
Non Qualified Pension Plans
Benefit Obligation
Accumulated benefit obligation		20	19
Projected benefit obligation at beginning of year		19	18
Interest cost		1	1
Actuarial loss (gain)		2	2
Benefits paid		(2)	(2)
Projected benefit obligation at end of year		20	19	18
Fair Value of Plan Assets
Fair value of plan assets at beginning of year		0	0
Actual return on plan assets		0	0
Corporation contribution		2	2
Benefits paid		(2)	(2)
Fair value of plan assets at end of year		0	0	$ 0
Funded status of plans		$ (20)	$ (19)

Retirement Plans - Schedule o_2

Retirement Plans - Schedule of Actuarial Assumptions Used in Determination of Projected Benefit Obligation (Detail)	Dec. 31, 2020	Dec. 31, 2019
Retirement Benefits [Abstract]
Weighted average discount rate	2.31%	3.17%
Rates of average increase in compensation levels	3.50%	3.50%

Retirement Plans - Schedule o_3

Retirement Plans - Schedule of Net Periodic Pension Cost and Other Comprehensive Income (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Retirement Benefits [Abstract]
Interest cost	$ 6	$ 7	$ 6
Expected return on plan assets	(13)	(11)	(11)
Actuarial loss amortization	3	2	2
Total pension income	(4)	(2)	(3)
Current year actuarial loss	10	1	6
Amortization of actuarial loss	(3)	(2)	(2)
Total amount recognized in other comprehensive income	7	(1)	4
Total amount recognized in net periodic benefit cost and other comprehensive income	$ 3	$ (3)	$ 1

Retirement Plans - Schedule o_4

Retirement Plans - Schedule of Actuarial Assumptions Used in Determination of Net Periodic Pension Cost (Detail)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Retirement Benefits [Abstract]
Weighted average discount rate	3.17%	4.16%	4.19%
Rates of increase in compensation levels	3.50%	3.50%	3.50%
Expected long-term rate of return on assets	7.25%	7.25%	7.25%

Retirement Plans - Schedule o_5

Retirement Plans - Schedule of Estimated Future Cash Flows (Detail) $ in Millions	Dec. 31, 2020USD ($)
Retirement Benefits [Abstract]
Expected employer contributions: 2021	$ 1
Expected benefit payments: 2021	10
Expected benefit payments: 2022	10
Expected benefit payments: 2023	11
Expected benefit payments: 2024	11
Expected benefit payments: 2025	11
Expected benefit payments: 2026 - 2030	$ 52

Retirement Plans - Schedule o_6

Retirement Plans - Schedule of Contribution Expense (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Retirement Benefits [Abstract]
401(k) contribution expense	$ 17	$ 15	$ 15

Retirement Plans - Schedule o_7

Retirement Plans - Schedule of Asset Allocations for Pension Plans (Detail)	Dec. 31, 2020	Dec. 31, 2019
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Percentage of Plan Assets	63.00%	60.00%
Debt securities
Defined Benefit Plan Disclosure [Line Items]
Percentage of Plan Assets	36.00%	37.00%
Cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Percentage of Plan Assets	1.00%	3.00%
Minimum | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	45.00%
Minimum | Debt securities
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	30.00%
Minimum | Cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	0.00%
Maximum | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	65.00%
Maximum | Debt securities
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	50.00%
Maximum | Cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	10.00%

Retirement Plans - Schedule o_8

Retirement Plans - Schedule of Fair Value of Pension Plan Assets by Asset Category (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 189	$ 173	$ 150
Cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2	5
Common Stock
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4	6
Other large-cap U.S. financial services companies
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3	4
Other large-cap U.S. companies
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	60	54
Other equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1	1
U.S. large-cap equity index funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	1
U.S. small-cap equity index funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5	3
U.S. mid-cap equity index funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6	5
Non-U.S. equities growth fund
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	16	9
U.S. mid-cap
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	13	12
U.S. small-cap
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5	4
Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5	5
U.S. government agencies
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	45	51
Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	1
U.S. investment-grade fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	24	12
Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	144	121
Level 1 | Cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2	5
Level 1 | Common Stock
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4	6
Level 1 | Other large-cap U.S. financial services companies
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3	4
Level 1 | Other large-cap U.S. companies
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	60	54
Level 1 | Other equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1	1
Level 1 | U.S. large-cap equity index funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	1
Level 1 | U.S. small-cap equity index funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5	3
Level 1 | U.S. mid-cap equity index funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6	5
Level 1 | Non-U.S. equities growth fund
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	16	9
Level 1 | U.S. mid-cap
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	13	12
Level 1 | U.S. small-cap
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5	4
Level 1 | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5	5
Level 1 | U.S. government agencies
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 1 | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 1 | U.S. investment-grade fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	24	12
Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	45	52
Level 2 | Cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 2 | Common Stock
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 2 | Other large-cap U.S. financial services companies
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 2 | Other large-cap U.S. companies
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 2 | Other equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 2 | U.S. large-cap equity index funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 2 | U.S. small-cap equity index funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 2 | U.S. mid-cap equity index funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 2 | Non-U.S. equities growth fund
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 2 | U.S. mid-cap
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 2 | U.S. small-cap
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 2 | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 2 | U.S. government agencies
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	45	51
Level 2 | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	1
Level 2 | U.S. investment-grade fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 | Cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 | Common Stock
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 | Other large-cap U.S. financial services companies
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 | Other large-cap U.S. companies
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 | Other equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 | U.S. large-cap equity index funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 | U.S. small-cap equity index funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 | U.S. mid-cap equity index funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 | Non-U.S. equities growth fund
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 | U.S. mid-cap
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 | U.S. small-cap
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 | U.S. government agencies
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 | U.S. investment-grade fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0	$ 0

Income Taxes - Summary of Incom

Income Taxes - Summary of Income Tax Expense Allocated Based on Separate Tax Return Basis (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Current income taxes: Federal taxes	$ 71	$ 47	$ 41
Current income taxes: State taxes	5	4	6
Total current income taxes	76	51	47
Deferred income taxes: Federal taxes	(20)	30	32
Deferred income taxes: State taxes	1	3	0
Total deferred income taxes	(19)	33	32
Total income taxes	$ 57	$ 84	$ 79

Income Taxes - Summary of Recon

Income Taxes - Summary of Reconciliation Between the Statutory Tax Rate and Actual Effective Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Statutory tax rate	21.00%	21.00%	21.00%
State taxes, net of federal benefit	1.60%	1.10%	1.10%
Tax-exempt interest	(2.80%)	(2.20%)	(2.10%)
Cash surrender value of life insurance	(0.80%)	(0.50%)	(0.50%)
Tax credits	(6.30%)	(4.20%)	(2.80%)
TCJA deferred tax corporate rate change	2.50%	1.40%	0.70%
Tax Cuts and Jobs Act revaluation of net deferred tax assets	0	0	(0.004)
Other items	1.50%	1.10%	0.60%
Actual effective tax rate	16.70%	17.70%	17.60%

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Contingency [Line Items]
Income tax rate	16.70%	17.70%	17.60%
Investment tax credit	$ 8,300	$ 7,900	$ 6,500
Operating loss carryforwards, valuation allowance	32,600
Tax credit carryforward	3,300
Unrecognized tax benefits	2,000	$ 1,600
Unrecognized tax benefits which affect the effective tax rate if recognized	1,800
Reduction in the unrecognized tax benefit due to statutes of limitations for next twelve months	$ 70
Maximum
Income Tax Contingency [Line Items]
Income tax rate	21.00%	21.00%	21.00%
Yadkin Financial Corporation (YDKN) | Federal
Income Tax Contingency [Line Items]
Operating loss carryforwards	$ 22,000
Yadkin Financial Corporation (YDKN) | State
Income Tax Contingency [Line Items]
Operating loss carryforwards	$ 3,500

Income Taxes - Summary of Defer

Income Taxes - Summary of Deferred Tax Assets and Liabilities from Tax Effects of Temporary Differences (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Allowance for credit losses	$ 80	$ 43
Discounts on loans acquired in a business combination	16	41
Net operating loss/tax credit carryforwards	38	38
Deferred compensation	12	11
Securities impairments	1	1
Pension and other defined benefit plans	2	3
Lease liability	30	29
Net unrealized securities losses	0	2
Other	14	8
Total	193	176
Valuation allowance	(33)	(28)
Total deferred tax assets	160	148
Loan costs	(6)	(15)
Depreciation	(12)	(19)
Prepaid expenses	(1)	(1)
Amortizable intangibles	(13)	(15)
Lease financing	(32)	(35)
Mortgage servicing rights	(8)	(9)
Lease ROU asset	(28)	(27)
Net unrealized securities gains	(7)	0
Other	(2)	(2)
Total deferred tax liabilities	(109)	(123)
Net deferred tax assets	$ 51	$ 25

Other Comprehensive Income - Ch

Other Comprehensive Income - Changes in AOCI, Net of Tax, by Component (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	$ 4,883
Other comprehensive (loss) income before reclassifications	8
Amounts reclassified from AOCI	18
Net current period other comprehensive (loss) income	26
Balance at end of period	4,959
Unrealized Net Gains (Losses) on Debt Securities Available for Sale
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	11
Other comprehensive (loss) income before reclassifications	54
Amounts reclassified from AOCI	0
Net current period other comprehensive (loss) income	54
Balance at end of period	65
Unrealized Net Gains (Losses) on Derivative Instruments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(18)
Other comprehensive (loss) income before reclassifications	(40)
Amounts reclassified from AOCI	18
Net current period other comprehensive (loss) income	(22)
Balance at end of period	(40)
Unrecognized Pension and Postretirement Obligations
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(58)
Other comprehensive (loss) income before reclassifications	(6)
Amounts reclassified from AOCI	0
Net current period other comprehensive (loss) income	(6)
Balance at end of period	(64)
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(65)
Balance at end of period	$ (39)

Earnings Per Common Share - Com

Earnings Per Common Share - Computation of Basic and Diluted Earnings Per Common Share (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share [Abstract]
Net income	$ 72	$ 83	$ 84	$ 47	$ 95	$ 103	$ 95	$ 94	$ 286	$ 387	$ 373
Less: Preferred stock dividends									8	8	8
Net Income Available to Common Stockholders	$ 70	$ 81	$ 82	$ 45	$ 93	$ 101	$ 93	$ 92	$ 278	$ 379	$ 365
Basic weighted average common shares outstanding (in shares)									323,368,639	324,938,720	324,207,198
Net effect of dilutive stock options, warrants and restricted stock (in shares)									2,119,325	1,122,418	1,416,405
Diluted weighted average common shares outstanding (in shares)									325,487,964	326,061,138	325,623,603
Earnings per common share:
Basic (in usd per share)	$ 0.22	$ 0.25	$ 0.25	$ 0.14	$ 0.29	$ 0.31	$ 0.29	$ 0.28	$ 0.86	$ 1.17	$ 1.13
Diluted (in usd per share)	$ 0.22	$ 0.25	$ 0.25	$ 0.14	$ 0.29	$ 0.31	$ 0.29	$ 0.28	$ 0.85	$ 1.16	$ 1.12

Earnings Per Common Share - Sch

Earnings Per Common Share - Schedule of Average Shares Excluded from Diluted Earnings Per Common Share Calculation (Detail) - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share [Abstract]
Average shares excluded from the diluted earnings per common share calculation (in shares)	22,375	0	81

Regulatory Matters - Schedule o

Regulatory Matters - Schedule of Capital Ratios (Detail) $ in Millions	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total capital, actual amount	$ 3,324	$ 3,174
Tier 1 capital, actual amount	2,759	2,632
Common equity tier 1, actual amount	2,652	2,525
Leverage, actual amount	2,759	2,632
Risk weighted assets, actual amount	$ 26,948	$ 26,866
Total capital, actual ratio	0.1233	0.1181
Total capital, actual ratio tier 1 capital, actual ratio	0.1024	0.0979
Common equity tier 1, actual ratio	9.84%	9.40%
Leverage, actual ratio	0.0783	0.0820
Total capital, well-capitalized requirements amount	$ 2,695	$ 2,687
Tier 1 capital, well-capitalized requirements amount	$ 1,617	$ 1,612
Total capital, well-capitalized requirements ratio	0.1000	0.1000
Tier 1 capital, well-capitalized requirements ratio	0.0600	0.0600
Total capital, minimum capital requirements amount	$ 2,830	$ 2,821
Tier 1 capital, minimum capital requirements amount	2,291	2,284
Common equity tier 1, minimum capital requirements amount	1,886	1,881
Leverage, minimum capital requirements amount	$ 1,410	$ 1,283
Total capital, minimum capital requirements ratio	0.1050	0.1050
Tier 1 capital, minimum capital requirements ratio	0.0850	0.0850
Common equity tier 1, minimum capital requirements ratio	7.00%	7.00%
Leverage, minimum capital requirements ratio	0.0400	0.0400
FNBPA
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total capital, actual amount	$ 3,400	$ 3,039
Tier 1 capital, actual amount	2,882	2,841
Common equity tier 1, actual amount	2,802	2,761
Leverage, actual amount	2,882	2,841
Risk weighted assets, actual amount	$ 26,902	$ 26,806
Total capital, actual ratio	0.1264	0.1134
Total capital, actual ratio tier 1 capital, actual ratio	0.1071	0.1060
Common equity tier 1, actual ratio	10.42%	10.30%
Leverage, actual ratio	0.0819	0.0887
Total capital, well-capitalized requirements amount	$ 2,690	$ 2,681
Tier 1 capital, well-capitalized requirements amount	2,152	2,144
Common equity tier 1, well-capitalized requirements amount	1,749	1,742
Leverage, well-capitalized requirements amount	$ 1,760	$ 1,601
Total capital, well-capitalized requirements ratio	0.1000	0.1000
Tier 1 capital, well-capitalized requirements ratio	0.0800	0.0800
Common equity tier 1, well-capitalized requirements ratio	6.50%	6.50%
Leverage, well-capitalized requirements ratio	0.0500	0.0500
Total capital, minimum capital requirements amount	$ 2,825	$ 2,815
Tier 1 capital, minimum capital requirements amount	2,287	2,279
Common equity tier 1, minimum capital requirements amount	1,883	1,876
Leverage, minimum capital requirements amount	$ 1,408	$ 1,281
Total capital, minimum capital requirements ratio	0.1050	0.1050
Tier 1 capital, minimum capital requirements ratio	0.0850	0.0850
Common equity tier 1, minimum capital requirements ratio	7.00%	7.00%
Leverage, minimum capital requirements ratio	0.0400	0.0400

Regulatory Matters - Additional

Regulatory Matters - Additional Information (Detail) $ in Millions	Dec. 31, 2020USD ($)
Banking and Thrift, Other Disclosures [Abstract]
Retained earnings available for distribution	$ 477.6
Maximum amount loans that corporation can borrower under current provisions	$ 677.4

Cash Flow Information - Summary

Cash Flow Information - Summary of Cash Flow Information (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Cash Flows [Abstract]
Interest paid on deposits and other borrowings		$ 216	$ 329	$ 230
Income taxes paid		57	40	19
Transfers of loans to other real estate owned		3	15	12
Loans transferred to held for sale from portfolio	$ 500	537	389	0
Loans transferred to portfolio from held for sale		$ 0	$ 110	$ 0

Business Segments - Additional

Business Segments - Additional Information (Detail) - Segment	1 Months Ended	12 Months Ended
	Aug. 31, 2018	Dec. 31, 2020
Segment Reporting Information [Line Items]
Number of reportable segments		3
Mariner Finance, LLC
Segment Reporting Information [Line Items]
Stock purchase agreement, stock sold, percentage	100.00%

Business Segments - Financial I

Business Segments - Financial Information for Segments of FNB (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Interest income	$ 270	$ 273	$ 281	$ 306	$ 306	$ 314	$ 317	$ 310	$ 1,130	$ 1,247	$ 1,170
Interest expense	36	46	52	74	80	84	87	79	208	330	238
Net Interest Income	234	227	229	232	226	230	230	231	922	917	932
Provision for credit losses	18	27	30	48	7	12	11	14	123	44	61
Non-interest income	68	80	77	69	74	80	75	65	294	294	276
Non-interest expense									737	682	679
Amortization of intangibles									13	14	16
Income tax expense (benefit)									57	84	79
Net income (loss)	72	$ 83	$ 84	$ 47	95	$ 103	$ 95	$ 94	286	387	373
Total assets	37,354				34,615				37,354	34,615	33,102
Total intangibles	2,316				2,329				2,316	2,329	2,334
Operating Segments | Community Banking
Segment Reporting Information [Line Items]
Interest income									1,129	1,245	1,145
Interest expense									188	310	219
Net Interest Income									941	935	926
Provision for credit losses									123	44	54
Non-interest income									233	237	213
Non-interest expense									675	621	609
Amortization of intangibles									12	13	15
Income tax expense (benefit)									61	88	82
Net income (loss)									303	406	379
Total assets	37,245				34,491				37,245	34,491	32,997
Total intangibles	2,279				2,291				2,279	2,291	2,304
Operating Segments | Wealth Management
Segment Reporting Information [Line Items]
Interest income									0	0	0
Interest expense									0	0	0
Net Interest Income									0	0	0
Provision for credit losses									0	0	0
Non-interest income									49	46	44
Non-interest expense									35	34	33
Amortization of intangibles									0	0	1
Income tax expense (benefit)									3	3	2
Net income (loss)									11	9	8
Total assets	38				32				38	32	26
Total intangibles	9				10				9	10	10
Operating Segments | Insurance
Segment Reporting Information [Line Items]
Interest income									0	0	0
Interest expense									0	0	0
Net Interest Income									0	0	0
Provision for credit losses									0	0	0
Non-interest income									22	20	16
Non-interest expense									19	17	17
Amortization of intangibles									1	1	0
Income tax expense (benefit)									0	0	0
Net income (loss)									2	2	(1)
Total assets	35				35				35	35	25
Total intangibles	28				28				28	28	20
Operating Segments | Consumer Finance
Segment Reporting Information [Line Items]
Interest income											25
Interest expense											2
Net Interest Income											23
Provision for credit losses											6
Non-interest income											2
Non-interest expense											15
Amortization of intangibles											0
Income tax expense (benefit)											1
Net income (loss)											3
Total assets											0
Total intangibles											0
Parent and Other
Segment Reporting Information [Line Items]
Interest income									1	2	0
Interest expense									20	20	17
Net Interest Income									(19)	(18)	(17)
Provision for credit losses									0	0	1
Non-interest income									(10)	(9)	1
Non-interest expense									8	10	5
Amortization of intangibles									0	0	0
Income tax expense (benefit)									(7)	(7)	(6)
Net income (loss)									(30)	(30)	(16)
Total assets	36				57				36	57	54
Total intangibles	$ 0				$ 0				$ 0	$ 0	$ 0

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Fair Value Measurements Disclosure [Line Items]
Percentage of securities using market-based information	100.00%
Transfer of equity security to non-marketable equity securities, included in other assets	$ 0	$ 0
Short-term borrowings approximate fair value for amounts that mature, days, less than	90 days
Fair value, measurements, nonrecurring
Fair Value Measurements Disclosure [Line Items]
Impaired loans, carrying amount	$ 44,900,000
Allocated allowance for loan losses	13,200,000	5,000,000
Provision for fair value measurements included in allowance for loan losses	36,000,000
Carrying amount of OREO	4,400,000
Written down of OREO	2,800,000
Loss from OREO included in earnings	1,600,000
Commercial loan | Minimum
Fair Value Measurements Disclosure [Line Items]
Financing receivable, individual reserves in default, threshold	1,000,000
Commercial and Consumer Loans | Maximum
Fair Value Measurements Disclosure [Line Items]
Financing receivable, individual reserves in default, threshold	1,000,000
Mortgage Servicing Rights
Fair Value Measurements Disclosure [Line Items]
Valuation allowance for impairment of recognized servicing assets, balance	7,300,000	1,500,000
Mortgage Servicing Rights | Fair value, measurements, nonrecurring
Fair Value Measurements Disclosure [Line Items]
Servicing asset	42,900,000
Valuation allowance for impairment of recognized servicing assets, balance	7,300,000
Servicing asset, carrying value	35,600,000
Mortgage Servicing Rights | Fair value, measurements, nonrecurring | Provision Expense
Fair Value Measurements Disclosure [Line Items]
Valuation allowance for impairment of recognized servicing assets, provision expense	5,800,000
SBA-Guaranteed Loan Servicing
Fair Value Measurements Disclosure [Line Items]
Valuation allowance for impairment of recognized servicing assets, balance	1,100,000	$ 1,200,000
SBA-Guaranteed Loan Servicing | Fair value, measurements, nonrecurring
Fair Value Measurements Disclosure [Line Items]
Servicing asset	4,000,000
Valuation allowance for impairment of recognized servicing assets, balance	1,100,000
Servicing asset, carrying value	2,900,000
Valuation allowance for impairment of recognized servicing assets, provision expense	$ 100,000

Fair Value Measurements - Balan

Fair Value Measurements - Balances of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Millions		Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		$ 3,463	$ 3,289
Loans held for sale	[1]	144	41
Derivative financial instruments		376	154
Derivative financial instruments		40	25
U.S. Treasury
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		600
U.S. government agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		172	151
U.S. government-sponsored entities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		161	226
Agency collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		1,124	1,240
Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		378	345
States of the U.S. and political subdivisions (municipals)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		32	11
Other debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		2	2
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		600	0
Derivative financial instruments		0	0
Derivative financial instruments		0	0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		2,863	3,289
Derivative financial instruments		352	151
Derivative financial instruments		40	25
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		0	0
Derivative financial instruments		24	3
Derivative financial instruments		0	0
Fair value, measurements, recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		3,463	3,289
Loans held for sale		144	41
Derivative financial instruments		376	154
Total assets measured at fair value on a recurring basis		3,983	3,484
Derivative financial instruments		40	25
Total liabilities measured at fair value on a recurring basis		40	25
Fair value, measurements, recurring | U.S. Treasury
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		600
Fair value, measurements, recurring | U.S. government agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		172	151
Fair value, measurements, recurring | U.S. government-sponsored entities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		161	226
Fair value, measurements, recurring | Agency mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		994	1,314
Fair value, measurements, recurring | Agency collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		1,124	1,240
Fair value, measurements, recurring | Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		378	345
Fair value, measurements, recurring | States of the U.S. and political subdivisions (municipals)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		32	11
Fair value, measurements, recurring | Other debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		2	2
Fair value, measurements, recurring | Trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments		349	149
Fair value, measurements, recurring | Not for trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments		27	5
Fair value, measurements, recurring | Trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments		37	24
Fair value, measurements, recurring | Not for trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments		3	1
Fair value, measurements, recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		600	0
Loans held for sale		0	0
Derivative financial instruments		0	0
Total assets measured at fair value on a recurring basis		600	0
Derivative financial instruments		0	0
Total liabilities measured at fair value on a recurring basis		0	0
Fair value, measurements, recurring | Level 1 | U.S. Treasury
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		600
Fair value, measurements, recurring | Level 1 | U.S. government agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		0	0
Fair value, measurements, recurring | Level 1 | U.S. government-sponsored entities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		0	0
Fair value, measurements, recurring | Level 1 | Agency mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		0	0
Fair value, measurements, recurring | Level 1 | Agency collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		0	0
Fair value, measurements, recurring | Level 1 | Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		0	0
Fair value, measurements, recurring | Level 1 | States of the U.S. and political subdivisions (municipals)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		0	0
Fair value, measurements, recurring | Level 1 | Other debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		0	0
Fair value, measurements, recurring | Level 1 | Trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments		0	0
Fair value, measurements, recurring | Level 1 | Not for trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments		0	0
Fair value, measurements, recurring | Level 1 | Trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments		0	0
Fair value, measurements, recurring | Level 1 | Not for trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments		0	0
Fair value, measurements, recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		2,863	3,289
Loans held for sale		144	41
Derivative financial instruments		352	151
Total assets measured at fair value on a recurring basis		3,359	3,481
Derivative financial instruments		40	25
Total liabilities measured at fair value on a recurring basis		40	25
Fair value, measurements, recurring | Level 2 | U.S. Treasury
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		0
Fair value, measurements, recurring | Level 2 | U.S. government agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		172	151
Fair value, measurements, recurring | Level 2 | U.S. government-sponsored entities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		161	226
Fair value, measurements, recurring | Level 2 | Agency mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		994	1,314
Fair value, measurements, recurring | Level 2 | Agency collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		1,124	1,240
Fair value, measurements, recurring | Level 2 | Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		378	345
Fair value, measurements, recurring | Level 2 | States of the U.S. and political subdivisions (municipals)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		32	11
Fair value, measurements, recurring | Level 2 | Other debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		2	2
Fair value, measurements, recurring | Level 2 | Trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments		349	149
Fair value, measurements, recurring | Level 2 | Not for trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments		3	2
Fair value, measurements, recurring | Level 2 | Trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments		37	24
Fair value, measurements, recurring | Level 2 | Not for trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments		3	1
Fair value, measurements, recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		0	0
Loans held for sale		0	0
Derivative financial instruments		24	3
Total assets measured at fair value on a recurring basis		24	3
Derivative financial instruments		0	0
Total liabilities measured at fair value on a recurring basis		0	0
Fair value, measurements, recurring | Level 3 | U.S. Treasury
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		0
Fair value, measurements, recurring | Level 3 | U.S. government agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		0	0
Fair value, measurements, recurring | Level 3 | U.S. government-sponsored entities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		0	0
Fair value, measurements, recurring | Level 3 | Agency mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		0	0
Fair value, measurements, recurring | Level 3 | Agency collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		0	0
Fair value, measurements, recurring | Level 3 | Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		0	0
Fair value, measurements, recurring | Level 3 | States of the U.S. and political subdivisions (municipals)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		0	0
Fair value, measurements, recurring | Level 3 | Other debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available for sale		0	0
Fair value, measurements, recurring | Level 3 | Trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments		0	0
Fair value, measurements, recurring | Level 3 | Not for trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments		24	3
Fair value, measurements, recurring | Level 3 | Trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments		0	0
Fair value, measurements, recurring | Level 3 | Not for trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments		$ 0	$ 0
[1]	Amount represents loans for which we have elected the fair value option. See Note 25.

Fair Value Measurements - Add_2

Fair Value Measurements - Additional Information about Assets Measured at Fair Value on Recurring Basis (Detail) - Fair value, measurements, recurring - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	$ 3	$ 1
Issuances	24	3
Settlements	(3)	(1)
Balance at end of period	24	3
Interest Rate Lock Commitments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	3	1
Issuances	24	3
Settlements	(3)	(1)
Balance at end of period	$ 24	$ 3

Fair Value Measurements - Add_3

Fair Value Measurements - Additional Information about Assets Measured at Fair Value on Non-Recurring Basis (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fair value, measurements, nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent loans	$ 45
Impaired loans	13.2	$ 5
Other real estate owned	3	4
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	0	0
Level 1 | Fair value, measurements, nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent loans	0
Impaired loans		0
Other real estate owned	0	0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	0	0
Level 2 | Fair value, measurements, nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent loans	0
Impaired loans		0
Other real estate owned	0	0
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	39	48
Level 3 | Fair value, measurements, nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent loans	45
Impaired loans		5
Other real estate owned	3	4
SBA-Guaranteed Loan Servicing
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	3	3	$ 4	$ 5
SBA-Guaranteed Loan Servicing | Fair value, measurements, nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	3	3
SBA-Guaranteed Loan Servicing | Level 1 | Fair value, measurements, nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	0	0
SBA-Guaranteed Loan Servicing | Level 2 | Fair value, measurements, nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	0	0
SBA-Guaranteed Loan Servicing | Level 3 | Fair value, measurements, nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	3	3
Mortgage Servicing Rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	35.6	45.2	$ 41.1	$ 32.4
Mortgage Servicing Rights | Fair value, measurements, nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	36	30
Mortgage Servicing Rights | Level 1 | Fair value, measurements, nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	0	0
Mortgage Servicing Rights | Level 2 | Fair value, measurements, nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	0	0
Mortgage Servicing Rights | Level 3 | Fair value, measurements, nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	$ 36	$ 30

Fair Value Measurements - Fair

Fair Value Measurements - Fair Values of Corporation's Financial Instruments (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Financial Assets
Cash and cash equivalents	$ 1,383	$ 599
Debt securities available for sale	3,463	3,289
Securities held to maturity	2,868	3,275
Securities held to maturity	2,973	3,305
Net Loans and Leases	25,096	23,093
Derivative financial instruments	376	154
Financial Liabilities
Deposits	29,122	24,786
Short-term borrowings	1,804	3,216
Long-term borrowings	1,095	1,340
Long-term borrowings	548
Derivative liabilities	40	25
Carrying Amount
Financial Assets
Cash and cash equivalents	1,383	599
Debt securities available for sale	3,463	3,289
Securities held to maturity	2,868	3,275
Net Loans and Leases	25,250	23,144
Loan servicing rights	39	46
Derivative financial instruments	376	154
Accrued interest receivable	90	109
Financial Liabilities
Deposits	29,122	24,786
Short-term borrowings	1,804	3,216
Long-term borrowings	1,095	1,340
Derivative liabilities	40	25
Accrued interest payable	13	21
Fair Value
Financial Assets
Cash and cash equivalents	1,383	599
Debt securities available for sale	3,463	3,289
Securities held to maturity	2,973	3,305
Net loans and leases, including loans held for sale	25,012	22,930
Loan servicing rights	39	48
Derivative financial instruments	376	154
Accrued interest receivable	90	109
Financial Liabilities
Deposits	29,158	24,797
Short-term borrowings	1,809	3,219
Long-term borrowings	1,068	1,355
Derivative liabilities	40	25
Accrued interest payable	13	21
Level 1
Financial Assets
Cash and cash equivalents	1,383	599
Debt securities available for sale	600	0
Securities held to maturity	0	0
Net loans and leases, including loans held for sale	0	0
Loan servicing rights	0	0
Derivative financial instruments	0	0
Accrued interest receivable	90	109
Financial Liabilities
Deposits	25,460	20,058
Short-term borrowings	1,809	3,219
Long-term borrowings	0	0
Derivative liabilities	0	0
Accrued interest payable	13	21
Level 2
Financial Assets
Cash and cash equivalents	0	0
Debt securities available for sale	2,863	3,289
Securities held to maturity	2,973	3,305
Net loans and leases, including loans held for sale	144	41
Loan servicing rights	0	0
Derivative financial instruments	352	151
Accrued interest receivable	0	0
Financial Liabilities
Deposits	3,698	4,739
Short-term borrowings	0	0
Long-term borrowings	0	0
Derivative liabilities	40	25
Accrued interest payable	0	0
Level 3
Financial Assets
Cash and cash equivalents	0	0
Debt securities available for sale	0	0
Securities held to maturity	0	0
Net loans and leases, including loans held for sale	24,868	22,889
Loan servicing rights	39	48
Derivative financial instruments	24	3
Accrued interest receivable	0	0
Financial Liabilities
Deposits	0	0
Short-term borrowings	0	0
Long-term borrowings	1,068	1,355
Derivative liabilities	0	0
Accrued interest payable	$ 0	$ 0

Parent Company Financial Stat_3

Parent Company Financial Statements - Consolidated Balance Sheet of Parent Company Only (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	$ 1,383	$ 599
Other assets	1,193	1,102
Total Assets	37,354	34,615	$ 33,102
Other liabilities	374	390
Long-term borrowings	1,095	1,340
Long-term	81	90
Total Liabilities	32,395	29,732
Stockholders' equity attributable to parent	4,959	4,883	$ 4,608	$ 4,409
Total Liabilities and Stockholders’ Equity	37,354	34,615
Parent Company
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	380	251
Other assets	10	18
Total Assets	5,825	5,445
Other liabilities	40	34
Advances from affiliates	197	197
Long-term borrowings	621	323
Short-term	7	7
Long-term	1	1
Total Liabilities	866	562
Stockholders' equity attributable to parent	4,959	4,883
Total Liabilities and Stockholders’ Equity	5,825	5,445
Parent Company | Bank Subsidiary
Condensed Balance Sheet Statements, Captions [Line Items]
Investment in and advances to subsidiaries	5,064	5,072
Parent Company | Non-bank Subsidiaries
Condensed Balance Sheet Statements, Captions [Line Items]
Investment in and advances to subsidiaries	$ 371	$ 104

Parent Company Financial Stat_4

Parent Company Financial Statements - Statements of Income of Parent Company Only (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Condensed Income Statements, Captions [Line Items]
Interest income	$ 270	$ 273	$ 281	$ 306	$ 306	$ 314	$ 317	$ 310	$ 1,130	$ 1,247	$ 1,170
Other income									2	4	1
Interest expense	36	46	52	74	80	84	87	79	208	330	238
Income tax benefit									(57)	(84)	(79)
Net income	72	$ 83	$ 84	$ 47	95	$ 103	$ 95	$ 94	286	387	373
Parent Company
Condensed Income Statements, Captions [Line Items]
Dividend income from subsidiaries:									304	181	170
Interest income									6	0	4
Other income									0	0	5
Total Income									310	181	179
Interest expense									25	19	20
Other expenses									18	18	15
Total Expenses									43	37	35
Income Before Taxes and Equity in Undistributed Income of Subsidiaries									267	144	144
Income tax benefit									7	7	6
Income after income taxes									274	151	150
Equity in undistributed income (loss) of subsidiaries:	12				236				12	236	222
Net income									286	387	373
Parent Company | Bank
Condensed Income Statements, Captions [Line Items]
Dividend income from subsidiaries:									300	179	162
Equity in undistributed income (loss) of subsidiaries:	15				236				15	236	225
Parent Company | Non-Bank
Condensed Income Statements, Captions [Line Items]
Dividend income from subsidiaries:									4	2	8
Equity in undistributed income (loss) of subsidiaries:	$ (3)				$ 0				$ (3)	$ 0	$ (2)

Parent Company Financial Stat_5

Parent Company Financial Statements - Statements of Cash Flows of Parent Company Only (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating Activities
Net income	$ 72	$ 83	$ 84	$ 47	$ 95	$ 103	$ 95	$ 94	$ 286	$ 387	$ 373
Other, net									(177)	(225)	(27)
Net cash flows provided by operating activities									113	259	611
Investing Activities
Net cash flows used in investing activities									(1,822)	(1,131)	(1,920)
Financing Activities
Decrease in long-term debt									(574)	(239)	(77)
Increase in long-term debt									328	954	37
Other, net									17	12	14
Preferred stock									(8)	(8)	(8)
Common stock									(157)	(157)	(157)
Net cash flows provided by financing activities									2,493	983	1,318
Net Increase (Decrease) in Cash and Cash Equivalents									784	111	9
Cash and cash equivalents at beginning of year				599				488	599	488	479
Cash and Cash Equivalents at End of Year	1,383				599				1,383	599	488
Interest									216	329	230
Parent Company
Operating Activities
Net income									286	387	373
Undistributed earnings from subsidiaries	(12)				(236)				(12)	(236)	(222)
Other, net									13	2	(13)
Net cash flows provided by operating activities									287	153	138
Investing Activities
Proceeds from sale of securities available for sale									0	0	1
Net decrease in advances to subsidiaries									0	0	20
Payment for further investment in subsidiaries									(270)	(47)	(22)
Net cash received in business combinations									0	0	123
Net cash flows used in investing activities									(270)	(47)	122
Financing Activities
Net decrease in advance from affiliate									0	0	(19)
Net decrease in short-term borrowings									0	0	(1)
Decrease in long-term debt									(4)	(77)	(2)
Increase in long-term debt									302	121	1
Other, net									(21)	12	14
Preferred stock									(8)	(8)	(8)
Common stock									(157)	(157)	(157)
Net cash flows provided by financing activities									112	(109)	(172)
Net Increase (Decrease) in Cash and Cash Equivalents									129	(3)	88
Cash and cash equivalents at beginning of year				$ 251				$ 254	251	254	166
Cash and Cash Equivalents at End of Year	$ 380				$ 251				380	251	254
Interest									$ 26	$ 20	$ 17

Quarterly Earnings Summary (U_3

Quarterly Earnings Summary (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Quarterly Earnings Summary (Unaudited) [Abstract]
Interest income	$ 270	$ 273	$ 281	$ 306	$ 306	$ 314	$ 317	$ 310	$ 1,130	$ 1,247	$ 1,170
Interest expense	36	46	52	74	80	84	87	79	208	330	238
Net Interest Income	234	227	229	232	226	230	230	231	922	917	932
Provision for credit losses	18	27	30	48	7	12	11	14	123	44	61
Total non-interest income	68	80	77	69	74	80	75	65	294	294	276
Total non-interest expense	199	180	176	195	177	178	175	166	750	696	695
Net income	72	83	84	47	95	103	95	94	286	387	373
Net income available to common stockholders	$ 70	$ 81	$ 82	$ 45	$ 93	$ 101	$ 93	$ 92	$ 278	$ 379	$ 365
Earnings per Common Share
Basic (in usd per share)	$ 0.22	$ 0.25	$ 0.25	$ 0.14	$ 0.29	$ 0.31	$ 0.29	$ 0.28	$ 0.86	$ 1.17	$ 1.13
Diluted (in usd per share)	$ 0.22	$ 0.25	$ 0.25	$ 0.14	$ 0.29	$ 0.31	$ 0.29	$ 0.28	$ 0.85	$ 1.16	$ 1.12