People's United Financial (PBCT) 10-K 2 Mar 20 2019 FY Annual report Financial data

Cover Page

Cover Page - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Feb. 14, 2020	Jun. 30, 2019
Entity Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
Document Transition Report	false
Entity Registrant Name	People's United Financial, Inc.
Entity File Number	001-33326
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	20-8447891
Entity Address, Address Line One	850 Main Street
Entity Address, City or Town	Bridgeport
Entity Address, State or Province	CT
Entity Address, Postal Zip Code	06604
City Area Code	(203)
Local Phone Number	338-7171
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
Entity Shell Company	false
Entity Public Float			$ 6,690
Entity Common Stock, Shares Outstanding		433,739,103
Documents Incorporated by Reference	Portions of the Proxy Statement for the Annual Meeting of Shareholders to be held on May 21, 2020, are incorporated by reference into Part III.
Amendment Flag	false
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Entity Central Index Key	0001378946
Current Fiscal Year End Date	--12-31
Common Stock [Member]
Entity Information [Line Items]
Title of 12(b) Security	Common Stock, $0.01 par value per share
Trading Symbol	PBCT
Security Exchange Name	NASDAQ
Series A Preferred Stock [Member]
Entity Information [Line Items]
Title of 12(b) Security	Fixed-to-Floating Rate Non-Cumulative Perpetual Preferred Stock, Series A, $0.01 par value per share
Trading Symbol	PBCTP
Security Exchange Name	NASDAQ

Consolidated Statements of Cond

Consolidated Statements of Condition - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Assets
Cash and due from banks	$ 484.2	$ 665.7
Short-term investments	316.8	266.3
Total cash and cash equivalents (note 3)	801	932
Securities (note 4):
Trading debt securities, at fair value	7.1	8.4
Equity securities, at fair value	8.2	8.1
Debt securities available-for-sale, at fair value	3,564.3	3,121
Debt securities held-to-maturity, at amortized cost (fair value of $4.02 billion and $3.78 billion)	3,869.2	3,792.3
Federal Home Loan Bank and Federal Reserve Bank stock, at cost	341.1	303.4
Total securities	7,789.9	7,233.2
Loans held-for-sale (note 5)	511.3	19.5
Loans (notes 5 and 6):
Financing Receivable	43,596.1	35,241.4
Less allowance for loan losses	(246.6)	(240.4)
Total loans, net	43,349.5	35,001
Goodwill (notes 2 and 7)	3,065.5	2,685.7
Bank-owned life insurance	705	467
Premises and equipment, net (note 8)	305.5	267.3
Other acquisition-related intangible assets (notes 2 and 7)	209.1	180
Other assets (notes 6, 9 and 22)	1,853	1,091.6
Total assets	58,589.8	47,877.3
Deposits (note 10):
Non-interest-bearing	9,803.7	8,543
Savings	4,987.7	4,116.5
Interest-bearing checking and money market	19,592.6	16,583.3
Time	9,205.5	6,916.2
Total deposits	43,589.5	36,159
Borrowings (note 11):
Federal Home Loan Bank advances	3,125.4	2,404.5
Federal funds purchased	1,620	845
Customer repurchase agreements	409.1	332.9
Other borrowings	0	11
Total borrowings	5,154.5	3,593.4
Notes and debentures (note 12)	993.1	895.8
Other liabilities (notes 6, 9 and 22)	905.5	695.2
Total liabilities	50,642.6	41,343.4
Commitments and contingencies (notes 6, 21 and 22)
Stockholders’ Equity (notes 2, 14, 17, 18 and 19)
Preferred stock ($0.01 par value; 50.0 million shares authorized; 10.0 million shares issued and outstanding at both dates)	244.1	244.1
Common stock ($0.01 par value; 1.95 billion shares authorized; 532.8 million shares and 466.3 million shares issued)	5.3	4.7
Additional paid-in capital	7,639.4	6,549.3
Retained earnings	1,512.8	1,284.8
Unallocated common stock of Employee Stock Ownership Plan, at cost (5.9 million shares and 6.3 million shares)	(122.9)	(130.1)
Accumulated other comprehensive loss	(166.9)	(256.8)
Treasury stock, at cost (89.2 million shares and 89.0 million shares)	(1,164.6)	(1,162.1)
Total stockholders’ equity	7,947.2	6,533.9
Total liabilities and stockholders’ equity	58,589.8	47,877.3
Commercial [Member]
Loans (notes 5 and 6):
Financing Receivable	30,714.3	25,077.7
Less allowance for loan losses	(217.9)	(209.5)
Retail Loans [Member]
Loans (notes 5 and 6):
Financing Receivable	12,881.8	10,163.7
Less allowance for loan losses	(28.7)	(30.9)
Commercial Real Estate Loan [Member] | Commercial [Member]
Loans (notes 5 and 6):
Financing Receivable	14,762.3	11,649.6
Commercial and Industrial [Member]
Securities (note 4):
Loans held-for-sale (note 5)	157.9
Commercial and Industrial [Member] | Commercial [Member]
Loans (notes 5 and 6):
Financing Receivable	11,041.6	9,088.9
Equipment Financing [Member] | Commercial [Member]
Loans (notes 5 and 6):
Financing Receivable	4,910.4	4,339.2
Residential Mortgage Loan [Member] | Retail Loans [Member]
Loans (notes 5 and 6):
Financing Receivable	10,318.1	8,154.2
Home Equity and Other Consumer [Member] | Retail Loans [Member]
Loans (notes 5 and 6):
Financing Receivable	$ 2,563.7	$ 2,009.5

Consolidated Statements of Co_2

Consolidated Statements of Condition (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Securities held to maturity, at fair value	$ 4,020	$ 3,775.9
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	50,000,000	50,000,000
Preferred stock, shares issued (in shares)	10,000,000	10,000,000
Preferred stock, shares outstanding (in shares)	10,000,000	10,000,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	1,950,000,000	1,950,000,000
Common stock, shares issued (in shares)	532,800,000	466,300,000
Unallocated common stock of Employee Stock Ownership Plan (in shares)	5,923,692	6,300,000
Treasury stock (in shares)	89,200,000	89,000,000

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Interest and dividend income:
Commercial real estate	$ 556.4	$ 463.4	$ 405.7
Commercial and industrial	443.6	365.7	298.8
Equipment financing	253.8	212.3	152.1
Residential mortgage	329.1	236.2	207.5
Home equity and other consumer	106.1	88.6	80
Interest and Fee Income, Loans and Leases Held-in-portfolio, Total	1,689	1,366.2	1,144.1
Securities	186.5	184.2	153.7
Short-term investments	4.8	5	3.7
Loans held-for-sale	0.8	0.9	0.9
Total interest and dividend income	1,881.1	1,556.3	1,302.4
Interest expense:
Deposits (note 10)	356.9	216.1	130.7
Borrowings (note 11)	77	70.9	41.3
Notes and debentures	34.9	33.3	29.9
Total interest expense	468.8	320.3	201.9
Net interest income	1,412.3	1,236	1,100.5
Provision for loan losses (note 5)	28.3	30	26
Net interest income after provision for loan losses	1,384	1,206	1,074.5
Non-interest income:
Operating lease income (note 6)	51.2
Operating lease income (note 6)		44.9	43.8
Cash management fees	28.4	27.1	26.1
Net security gains (losses) (note 4)	0.2	(9.8)	(25.4)
Other non-interest income (notes 4 and 6)	85.9	50.9	62.6
Total non-interest income	431.1	366.4	352.9
Non-interest expense:
Compensation and benefits (notes 18 and 19)	646.2	562.9	522.7
Occupancy and equipment (note 8)	185.9	168.2	159.6
Professional and outside services	98.2	77.6	81.5
Regulatory assessments	26.1	37.9	41.7
Operating lease expense	38.8	36.4	35.2
Amortization of other acquisition-related intangible assets (note 7)	32.5	21.8	30
Other non-interest expense	135	91.3	89.6
Total non-interest expense	1,162.7	996.1	960.3
Income before income tax expense	652.4	576.3	467.1
Income tax expense (benefit)	132	108.2	129.9
Net income	520.4	468.1	337.2
Preferred stock dividend	14.1	14.1	14.1
Net income available to common shareholders	$ 506.3	$ 454	$ 323.1
Earnings per common share (note 16):
Basic (in dollars per share)	$ 1.28	$ 1.30	$ 0.98
Diluted (in dollars per share)	$ 1.27	$ 1.29	$ 0.97
Bank Service Charges [Member]
Non-interest income:
Revenue from contract with customer	$ 107.5	$ 99.9	$ 98.5
Investment Management Fees [Member]
Non-interest income:
Revenue from contract with customer	67.6	68.7	66.5
Commercial Banking Lending Fees [Member]
Non-interest income:
Revenue from contract with customer	42.7	37.3	35.5
Insurance Revenue [Member]
Non-interest income:
Revenue from contract with customer	37	34.6	33.2
Brokerage Commissions [Member]
Non-interest income:
Revenue from contract with customer	$ 10.6	$ 12.8	$ 12.1

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 520.4	$ 468.1	$ 337.2
Net actuarial gains and losses on pension and other postretirement plans:
Net actuarial gains (losses) arising during the year	12.1	(32.6)	(5.5)
Reclassification adjustment for net actuarial loss included in net income	8.3	8.6	9.3
Net actuarial gains (losses)	20.4	(24)	3.8
Prior service credit on pension and other postretirement plans:
Reclassification adjustment for prior service credit included in net income	0	(0.3)	(0.8)
Net actuarial gains (losses) and prior service credit	20.4	(24.3)	3
Net unrealized gains and losses on securities available-for-sale:
Net unrealized holding gains (losses) arising during the year	89.2	(38.3)	(8.6)
Reclassification adjustment for net realized (gains) losses included in net income	(0.1)	9.9	25.4
Net unrealized gains (losses)	89.1	(28.4)	16.8
Net unrealized gains and losses on securities transferred to held-to-maturity:
Reclassification adjustment for amortization of unrealized losses on securities transferred to held-to-maturity included in net income	4.6	3.9	3.7
Net unrealized gains	4.6	3.9	3.7
Net unrealized gains and losses on derivatives accounted for as cash flow hedges:
Net unrealized gains (losses) arising during the year	1.9
Reclassification adjustment for net realized losses (gains) included in net income	1.1
Net unrealized gains (losses)	3
Net unrealized gains (losses) arising during the year		(1.7)	(1)
Reclassification adjustment for net realized losses (gains) included in net income		0.5	(0.9)
Net unrealized gains (losses)		(1.2)	(1.9)
Other comprehensive income (loss), before tax	117.1	(50)	21.6
Deferred income tax (expense) benefit related to other comprehensive income (loss)	(27.2)	12.2	(8.3)
Total other comprehensive income (loss), net of tax	89.9	(37.8)	13.3
Total comprehensive income	$ 610.3	$ 430.3	$ 350.5

Consolidated Statements of Chan

Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Millions	Total	Suffolk [Member]	First Connecticut Bancorp, Inc. [Member]	BSB Bancorp [Member]	United Financial [Member]	Preferred Stock [Member]	Common Stock [Member]	Common Stock [Member]Suffolk [Member]	Common Stock [Member]First Connecticut Bancorp, Inc. [Member]	Common Stock [Member]BSB Bancorp [Member]	Common Stock [Member]United Financial [Member]	Additional Paid-In Capital [Member]	Additional Paid-In Capital [Member]Suffolk [Member]	Additional Paid-In Capital [Member]First Connecticut Bancorp, Inc. [Member]	Additional Paid-In Capital [Member]BSB Bancorp [Member]	Additional Paid-In Capital [Member]United Financial [Member]	Retained Earnings [Member]	Unallocated ESOP Common Stock [Member]	[1]	Accumulated Other Comprehensive Loss [Member]	Treasury Stock [Member]
Beginning Balance at Dec. 31, 2016	$ 5,141.9					$ 244.1	$ 4					$ 5,446.1					$ 949.3	$ (144.6)		$ (195)	$ (1,162)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	337.2																337.2
Total other comprehensive income, net of tax (note 17)	13.3																			13.3
Common stock issued in acquisitions	484.8	$ 484.8						$ 0.2					$ 484.6
Cash dividends on common stock	(227.9)																(227.9)
Cash dividends on preferred stock	(14.1)																(14.1)
Restricted stock and performance- based share awards	14.2											14.3									(0.1)
ESOP common stock committed to be released (note 18)	6.4																(0.9)	7.3
Common stock repurchased and retired upon vesting of restricted stock awards (note 19)	(3.4)																(3.4)
Stock options and related tax benefits	67.5						0.2					67.3
Ending Balance at Dec. 31, 2017	5,819.9					244.1	4.4					6,012.3					1,040.2	(137.3)		(181.7)	(1,162.1)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	468.1																468.1
Total other comprehensive income, net of tax (note 17)	(37.8)																			(37.8)
Common stock issued in acquisitions	486.4		$ 486.4						$ 0.3					$ 486.1
Cash dividends on common stock	(243.8)																(243.8)
Cash dividends on preferred stock	(14.1)																(14.1)
Restricted stock and performance- based share awards	17.9											17.9									0
ESOP common stock committed to be released (note 18)	6.2																(1)	7.2
Common stock repurchased and retired upon vesting of restricted stock awards (note 19)	(2.5)																(2.5)
Stock options exercised	33						0					33
Ending Balance at Dec. 31, 2018	6,533.9					244.1	4.7					6,549.3					1,284.8	(130.1)		(256.8)	(1,162.1)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	520.4																520.4
Total other comprehensive income, net of tax (note 17)	89.9																			89.9
Common stock issued in acquisitions	1,045.1			$ 324.5	$ 720.6					$ 0.2	$ 0.4				$ 324.3	$ 720.2
Cash dividends on common stock	(274.8)																(274.8)
Cash dividends on preferred stock	(14.1)																(14.1)
Restricted stock and performance- based share awards	16.3											16.3
Common stock repurchased (note 14)	(2.5)																				(2.5)
ESOP common stock committed to be released (note 18)	5.7																(1.5)	7.2
Common stock repurchased and retired upon vesting of restricted stock awards (note 19)	(2)																(2)
Stock options exercised	29.3											29.3
Ending Balance at Dec. 31, 2019	$ 7,947.2					$ 244.1	$ 5.3					$ 7,639.4					$ 1,512.8	$ (122.9)		$ (166.9)	$ (1,164.6)
[1]	Employee Stock Ownership Plan

Consolidated Statements of Ch_2

Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash dividends on common stock (in dollars per share)	$ 0.7075	$ 0.6975	$ 0.6875
Retained Earnings [Member]
Cash dividends on common stock (in dollars per share)	$ 0.7075	$ 0.6975	$ 0.6875

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash Flows from Operating Activities:
Net income	$ 520.4	$ 468.1	$ 337.2
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of premises and equipment	41.7	36.3	39.1
Expense related to operating leases	38.8	36.4	35.2
Amortization of other acquisition-related intangible assets	32.5	21.8	30
Provision for loan losses	28.3	30	26
Expense related to share-based awards	24.9	22.4	19.8
Deferred income tax expense	14.3	1.9	25.8
ESOP common stock committed to be released	5.7	6.2	6.4
Net security (gains) losses	(0.2)	9.8	25.4
Net gains on sales of acquired loans	(0.4)	(1.8)	(2.4)
Net gains on sales of residential mortgage loans	(1.9)	(1.2)	(3.2)
Originations of loans held-for-sale	(180.3)	(188.2)	(261.8)
Proceeds from sales of loans held-for-sale	181.9	186.5	287.7
Net changes in trading debt securities	1.3	(0.2)	(1.4)
Excess income tax benefits from stock options exercised	0.3	1.3	1.1
Net changes in other assets and other liabilities	(466.5)	(40)	38.1
Net cash provided by operating activities	240.8	589.3	603
Cash Flows from Investing Activities:
Proceeds from sales of equity securities	1.6	2.3	0
Proceeds from principal repayments and maturities of debt securities available-for-sale	578.5	465.5	562.6
Proceeds from sales of debt securities available-for-sale	365.3	313.8	1,305.5
Proceeds from principal repayments and maturities of debt securities held-to-maturity	158.2	185.3	120.9
Purchases of debt securities available-for-sale	(827.8)	(726.8)	(603.3)
Purchases of debt securities held-to-maturity	(257.9)	(407.4)	(1,580.4)
Net redemptions of Federal Home Loan Bank stock	19.3	17.2	27.1
Net purchases of Federal Reserve Bank stock	(25.2)	(8.3)	(20.8)
Proceeds from sales of loans	51.2	22.3	38.7
Net principal (disbursements) collections of loans	(770.3)	244.8	(538.7)
Purchases of loans	(71.2)	(37.5)	(17.7)
Purchases of premises and equipment	(26.5)	(28.3)	(4.8)
Purchases of leased equipment, net	(41.2)	(59.6)	(24.2)
Proceeds from sales of real estate owned	13.9	9.1	10
Return of premiums on bank-owned life insurance, net	2.2	1	2.7
Net cash acquired in acquisitions and dispositions	519.4	6.2	28.9
Net cash used in investing activities	(310.5)	(0.4)	(693.5)
Cash Flows from Financing Activities:
Net (decrease) increase in deposits	(117.6)	696.6	1,343.1
Net increase (decrease) in borrowings with terms of three months or less	647.7	(525.7)	(293.8)
Repayments of borrowings with terms of more than three months	(321.2)	(476.7)	(380.7)
Repayments of notes and debentures	0	0	(125)
Cash dividends paid on common stock	(274.8)	(243.8)	(227.9)
Cash dividends paid on preferred stock	(14.1)	(14.1)	(14.1)
Repurchases of common stock	(4.5)	(2.5)	(3.4)
Proceeds from stock options exercised	24.1	27.9	61.8
Contingent consideration payments	(0.9)	(1.2)	(1)
Net cash (used in) provided by financing activities	(61.3)	(539.5)	359
Net (decrease) increase in cash, cash equivalents and restricted cash	(131)	49.4	268.5
Cash, cash equivalents and restricted cash at beginning of year	932	882.6	614.1
Cash, cash equivalents and restricted cash at end of year	801	932	882.6
Supplemental Information:
Interest payments	473.4	312.3	195.9
Income tax payments	107.7	45.6	112.9
Significant non-cash transactions:
Right-of-use assets obtained in exchange for lessee operating and finance lease liabilities	91.7
Real estate properties acquired by foreclosure	19.9	7.7	17.2
Unsettled purchases of securities	0	4	0
Assets acquired and liabilities assumed in acquisitions and dispositions (note 2):
Non-cash assets, excluding goodwill and other acquisition-related intangibles	9,224.7	3,173.6	2,642.1
Liabilities	9,120.4	2,965.1	2,634.1
Common stock issued in acquisitions	$ 1,045.1	$ 486.4	$ 484.8

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	NOTE 1 – Summary of Significant Accounting Policies People’s United Financial, Inc. (“People’s United” or the “Company”) is a bank holding company and a financial holding company registered under the Bank Holding Company Act of 1956, as amended, and is incorporated under the state laws of Delaware. People’s United is the holding company for People’s United Bank, National Association (the “Bank”), a national banking association headquartered in Bridgeport, Connecticut. The principal business of People’s United is to provide, through the Bank and its subsidiaries, commercial banking, retail banking and wealth management services to individual, corporate and municipal customers. The Bank provides a full-range of traditional banking services, including accepting deposits and originating loans, as well as specialized financial services through its non-bank subsidiaries, including: equipment financing provided through People’s Capital and Leasing Corp. (“PCLC”), People’s United Equipment Finance Corp. (“PUEFC”) and LEAF Commercial Capital, Inc. (“LEAF”); brokerage, financial advisory services, investment management services and life insurance provided through People’s Securities, Inc. (“PSI”); investment advisory services and financial management and planning services provided through People’s United Advisors, Inc. (“PUA”) and commercial insurance services provided through People’s United Insurance Agency, Inc. (“PUIA”). The Company’s overall financial results are particularly dependent on economic conditions in New England and New York, which are its primary markets, although economic conditions elsewhere in the United States affect its national equipment financing business. People’s United is regulated by the Board of Governors of the Federal Reserve System (the “FRB”) and subject to FRB examination, supervision and reporting requirements. The Bank is regulated by the Office of the Comptroller of the Currency (the “OCC”) and subject to OCC examination, supervision and reporting requirements. Deposits are insured up to applicable limits by the Deposit Insurance Fund of the Federal Deposit Insurance Corporation (the “FDIC”). Basis of Financial Statement Presentation The accompanying consolidated financial statements have been prepared in conformity with U.S. generally accepted accounting principles (“GAAP”) and include the accounts of People’s United and its subsidiaries. All significant intercompany transactions and balances are eliminated in consolidation. In preparing the consolidated financial statements, management is required to make significant estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses. Actual results could differ from management’s current estimates, as a result of changing conditions and future events. Several accounting estimates are particularly critical and are susceptible to significant near-term change, including the allowance for loan losses and asset impairment judgments, such as the recoverability of goodwill and other intangible assets. These accounting estimates, which are included in the discussion below, are reviewed with the Audit Committee of the Board of Directors. The judgments used by management in applying critical accounting policies may be affected by economic conditions, which may result in changes to future financial results. For example, subsequent evaluations of the loan portfolio, in light of the factors then prevailing, may result in significant changes in the allowance for loan losses in future periods, and the inability to collect outstanding principal may result in increased loan losses. For purposes of the Consolidated Statements of Cash Flows, cash equivalents include highly-liquid instruments, such as: (i) interest-bearing deposits at the Federal Reserve Bank of New York (the “FRB-NY”); (ii) government-sponsored enterprise (“GSE”) debt securities with an original maturity of three months or less (determined as of the date of purchase); (iii) federal funds sold; (iv) commercial paper; and (v) money market mutual funds. These instruments are reported as short-term investments in the Consolidated Statements of Condition at cost or amortized cost, which approximates fair value. GSE debt securities classified as cash equivalents are held to maturity and carry the implicit backing of the U.S. government, but are not direct obligations of the U.S. government. Securities Marketable debt securities (other than those reported as short-term investments) are classified as either trading debt securities, held-to-maturity debt securities or available-for-sale debt securities. Management determines the classification of a security at the time of its purchase and reevaluates such classification at each balance sheet date. Debt securities purchased for sale in the near term as well as those securities held by PSI (in accordance with the requirements for a broker-dealer) are classified as trading debt securities and reported at fair value with gains and losses reported in non-interest income. Debt securities for which People’s United has the intent and ability to hold to maturity are classified as held-to-maturity securities and reported at amortized cost. All other debt securities are classified as available-for-sale and reported at fair value with unrealized gains and losses reported on an after-tax basis in stockholders’ equity as a component of accumulated other comprehensive income (loss) (“AOCL”). Premiums (discounts) are amortized (accreted) to interest income for debt securities, using the interest method over the remaining period to contractual maturity, adjusted for the effect of actual prepayments in the case of mortgage-backed and collateralized mortgage obligation (“CMO”) securities. Security transactions are recorded on the trade date. Realized gains and losses are determined using the specific identification method and reported in non-interest income. Debt securities transferred from available-for-sale to held-to-maturity are recorded at fair value at the date of transfer. The unrealized pre-tax gain or loss resulting from the difference between fair value and amortized cost at the transfer date becomes part of the new amortized cost basis of the securities and remains in AOCL. Such unrealized gains or losses are amortized to interest income as an adjustment to yield over the remaining life of the securities, offset by the amortization (accretion) of the premium (discount) resulting from the transfer at fair value, with no effect to net income. Management conducts a periodic review and evaluation of the debt securities portfolio to determine if the decline in fair value of any security is deemed to be other-than-temporary. Other-than-temporary impairment losses are recognized on debt securities when: (i) People’s United has an intention to sell the security; (ii) it is more likely than not that People’s United will be required to sell the security prior to recovery; or (iii) People’s United does not expect to recover the entire amortized cost basis of the security. Other-than-temporary impairment losses on debt securities are reflected in earnings as realized losses to the extent the impairment is related to credit losses of the issuer. The amount of the impairment related to other factors is recognized in other comprehensive income. Management has the ability and intent to hold the securities classified as held-to-maturity until they mature, at which time People’s United expects to receive full value for the securities. Both Federal Home Loan Bank (“FHLB”) stock and FRB-NY stock are non-marketable equity securities and are, therefore, reported at their respective costs, which equals par value (the amount at which shares have been redeemed in the past). These investments are periodically evaluated for impairment based on, among other things, the capital adequacy of the applicable FHLB or the FRB-NY and their overall financial condition. Equity securities are reported at fair value with gains and losses reported in non-interest income. Securities Resale and Securities Repurchase Agreements In securities resale agreements, a counterparty transfers securities to People’s United (as transferee) and People’s United agrees to resell the same securities to the counterparty at a fixed price in the future. In securities repurchase agreements, which include both retail arrangements with customers and wholesale arrangements with other counterparties, People’s United (as transferor) transfers securities to a counterparty and agrees to repurchase the same securities from the counterparty at a fixed price in the future. People’s United accounts for securities resale agreements as secured lending transactions and securities repurchase agreements as secured borrowings since the transferor maintains effective control over the transferred securities and the transfer meets the other criteria for such accounting. The securities are pledged by the transferor as collateral and the transferee has the right by contract to repledge that collateral provided the same collateral is returned to the transferor upon maturity of the underlying agreement. The fair value of the pledged collateral approximates the recorded amount of the secured loan or borrowing. Decreases in the fair value of the transferred securities below an established threshold require the transferor to provide additional collateral. Loans Held-for-Sale Loans held-for-sale are reported at the lower of cost or fair value in the aggregate with any adjustment for net unrealized losses reported in non-interest income. Management identifies and designates as loans held-for-sale certain newly-originated adjustable-rate and fixed-rate residential mortgage loans that meet secondary market requirements, as these loans are originated with the intent to sell. From time to time, management may also identify and designate certain loans previously held-for-investment as held-for-sale. Such loans are transferred to loans held-for-sale and adjusted to the lower of cost or fair value with the resulting unrealized loss, if any, reported in non-interest income. Loans Loans acquired in connection with business combinations are referred to as ‘acquired’ loans as a result of the manner in which they are accounted for (see further discussion under ‘Acquired Loans’ below). All other loans are referred to as ‘originated’ loans. Basis of Accounting Originated loans are reported at amortized cost less the allowance for loan losses. Interest on loans is accrued to income monthly based on outstanding principal balances. Loan origination fees and certain direct loan origination costs are deferred, and the net fee or cost is recognized in interest income as an adjustment of yield. Depending on the loan portfolio, amounts are amortized or accreted using the level yield method over either the actual life or the estimated average life of the loan. Non-accrual Loans A loan is generally considered “non-performing” when it is placed on non-accrual status. A loan is generally placed on non-accrual status when it becomes 90 days past due as to interest or principal payments. Past due status is based on the contractual payment terms of the loan. A loan may be placed on non-accrual status before it reaches 90 days past due if such loan has been identified as presenting uncertainty with respect to the collectability of interest and principal. A loan past due 90 days or more may remain on accruing status if such loan is both well secured and in the process of collection. All previously accrued but unpaid interest on non-accrual loans is reversed from interest income in the period in which the accrual of interest is discontinued. Interest payments received on non-accrual loans (including impaired loans) are generally applied as a reduction of principal if future collections are doubtful, although such interest payments may be recognized as income. A loan remains on non-accrual status until the factors that indicated doubtful collectability no longer exist or until a loan is determined to be uncollectible and is charged off against the allowance for loan losses. There were no loans past due 90 days or more and still accruing interest at December 31, 2019, 2018 or 2017. Impaired Loans A loan is considered impaired when, based on current information and events, it is probable that the Company will be unable to collect all amounts due in accordance with the original contractual terms of the loan agreement, including scheduled principal and interest payments. Impaired loans also include certain loans whose terms have been modified in such a way that they are considered troubled debt restructurings (“TDRs”). Loans are considered TDRs if the borrower is experiencing financial difficulty and is afforded a concession by People’s United, such as, but not limited to: (i) payment deferral; (ii) a reduction of the stated interest rate for the remaining contractual life of the loan; (iii) an extension of the loan’s original contractual term at a stated interest rate lower than the current market rate for a new loan with similar risk; (iv) capitalization of interest; or (v) forgiveness of principal or interest. TDRs may either be accruing or placed on non-accrual status (and reported as non-performing loans) depending upon the loan’s specific circumstances, including the nature and extent of the related modifications. TDRs on non-accrual status remain classified as such until the loan qualifies for return to accrual status. Loans qualify for return to accrual status once they have demonstrated performance with the restructured terms of the loan agreement for a minimum of six months in the case of a commercial loan or, in the case of a retail loan, when the loan is less than 90 days past due. Loans may continue to be reported as TDRs after they are returned to accrual status. In accordance with regulatory guidance, residential mortgage and home equity loans restructured in connection with the borrower’s bankruptcy and meeting certain criteria are also required to be classified as TDRs, included in non-performing loans and written down to the estimated collateral value, regardless of delinquency status. Acquired loans that are modified are not considered for TDR classification provided they are evaluated for impairment on a pool basis (see further discussion under ‘Acquired Loans’ below). Impairment is evaluated on a collective basis for pools of retail loans possessing similar risk and loss characteristics and on an individual basis for other loans. If a loan is deemed to be impaired, a specific valuation allowance is allocated, if necessary, so that the loan is reported (net of the allowance) at the present value of expected future cash flows discounted at the loan’s original effective interest rate or at the fair value of the collateral less cost to sell if repayment is expected solely from the collateral. Interest payments on impaired non-accrual loans are typically applied to principal unless collectability of the principal amount is reasonably assured, in which case interest is recognized on a cash basis. Impaired loans, or portions thereof, are charged off when deemed uncollectible. Acquired Loans Loans acquired in a business combination are initially recorded at fair value with no carryover of an acquired entity’s previously established allowance for loan losses. Fair value of the loans is determined using market participant assumptions in estimating the amount and timing of both principal and interest cash flows expected to be collected, as adjusted for an estimate of future credit losses and prepayments, and then applying a market-based discount rate to those cash flows. Acquired loans are evaluated upon acquisition and classified as either purchased performing or purchased credit impaired (“PCI”). For purchased performing loans, any premium or discount, representing the difference between the fair value and the outstanding principal balance of the loans, is recognized (using the level yield method) as an adjustment to interest income over the remaining period to contractual maturity or until the loan is repaid in full or sold. Subsequent to the acquisition date, the method utilized to estimate the required allowance for loan losses for these loans is similar to that for originated loans. However, a provision for loan losses is only recorded when the required allowance for loan losses exceeds any remaining purchase discount at the loan level. PCI loans represent those acquired loans with specific evidence of deterioration in credit quality since origination and for which it is probable that, as of the acquisition date, all contractually required principal and interest payments will not be collected . Such loans are generally accounted for on a pool basis, with pools formed based on the loans’ common risk characteristics, such as loan collateral type and accrual status. Each pool is accounted for as a single asset with a single composite interest rate and an aggregate expectation of cash flows. Under the accounting model for PCI loans, the excess of cash flows expected to be collected over the carrying amount of the loans, referred to as the “accretable yield”, is accreted into interest income over the life of the loans in each pool using the level yield method. Accordingly, PCI loans are not subject to classification as non-accrual in the same manner as other loans. Rather, PCI loans are considered to be accruing loans because their interest income relates to the accretable yield recognized at the pool level and not to contractual interest payments at the loan level. The difference between contractually required principal and interest payments and the cash flows expected to be collected, referred to as the “nonaccretable difference”, includes estimates of both the impact of prepayments and future credit losses expected to be incurred over the life of the loans in each pool. As such, charge-offs on PCI loans are first applied to the nonaccretable difference and then to any allowance for loan losses recognized subsequent to acquisition. Subsequent to acquisition, actual cash collections are monitored relative to management’s expectations and revised cash flow forecasts are prepared, as warranted. These revised forecasts involve updates, as necessary, of the key assumptions and estimates used in the initial estimate of fair value. Generally speaking, expected cash flows are affected by: • Changes in the expected principal and interest payments over the estimated life — Updates to changes in expected cash flows are driven by the credit outlook and actions taken with borrowers. Changes in expected future cash flows resulting from loan modifications are included in the assessment of expected cash flows; • Changes in prepayment assumptions — Prepayments affect the estimated life of the loans which may change the amount of interest income, and possibly principal, expected to be collected; and • Changes in interest rate indices for variable rate loans — Expected future cash flows are based, as applicable, on the variable rates in effect at the time of the assessment of expected cash flows. A decrease in expected cash flows in subsequent periods may indicate that the loan pool is impaired, which would require the establishment of an allowance for loan losses by a charge to the provision for loan losses. An increase in expected cash flows in subsequent periods serves, first, to reduce any previously established allowance for loan losses by the increase in the present value of cash flows expected to be collected, and results in a recalculation of the amount of accretable yield for the loan pool. The adjustment of accretable yield due to an increase in expected cash flows is accounted for as a change in estimate. The additional cash flows expected to be collected are reclassified from the nonaccretable difference to the accretable yield, and the amount of periodic accretion is adjusted accordingly over the remaining life of the loans in the pool. PCI loans may be resolved either through receipt of payment (in full or in part) from the borrower, the sale of the loan to a third party or foreclosure of the collateral. In the event of a sale of the loan, a gain or loss on sale is recognized and reported within non-interest income based on the difference between the sales proceeds and the carrying amount of the loan. In other cases, individual loans are removed from the pool based on comparing the amount received from its resolution (fair value of the underlying collateral less costs to sell in the case of a foreclosure) with its outstanding balance. Any difference between these amounts is absorbed by the nonaccretable difference established for the entire pool. For loans resolved by payment in full, there is no adjustment of the nonaccretable difference since there is no difference between the amount received at resolution and the outstanding balance of the loan. In these cases, the remaining accretable yield balance is unaffected and any material change in remaining effective yield caused by the removal of the loan from the pool is addressed in connection with the subsequent cash flow re-assessment for the pool. PCI loans subject to modification are not removed from the pool even if those loans would otherwise be deemed TDRs as the pool, and not the individual loan, represents the unit of account. Allowance and Provision for Loan Losses Originated Portfolio The allowance for loan losses is established through provisions for loan losses charged to income. Losses on loans, including impaired loans, are charged to the allowance for loan losses when all or a portion of a loan is deemed to be uncollectible. Recoveries of loans previously charged off are credited to the allowance for loan losses when realized. People’s United maintains the allowance for loan losses at a level that is deemed to be appropriate to absorb probable losses inherent in the respective loan portfolios, based on a quarterly evaluation of a variety of factors. These factors include, but are not limited to: (i) People’s United’s historical loan loss experience and recent trends in that experience; (ii) risk ratings assigned by lending personnel to commercial real estate loans, commercial and industrial loans, and equipment financing loans, and the results of ongoing reviews of those ratings by People’s United’s independent loan review function; (iii) an evaluation of delinquent and non-performing loans and related collateral values; (iv) the probability of loss in view of geographic and industry concentrations and other portfolio risk characteristics; (v) the present financial condition of borrowers; and (vi) current economic conditions. The Company’s allowance for loan losses consists of three elements: (i) an allowance for commercial loans collectively evaluated for impairment; (ii) an allowance for retail loans collectively evaluated for impairment; and (iii) a specific allowance for loans individually evaluated for impairment, including loans classified as TDRs. Commercial Loans Collectively Evaluated for Impairment. The Company establishes a loan loss allowance for its commercial loans collectively evaluated for impairment using a methodology that incorporates (i) the probability of default for a given loan risk rating and (ii) historical loss-given-default data, both derived using appropriate look-back periods and loss emergence periods. In accordance with the Company’s loan risk rating system, each commercial loan is assigned a risk rating (using a nine-grade scale) by the originating loan officer, credit management, internal loan review or loan committee. Loans rated “One” represent those loans least likely to default while loans rated “Nine” represent a loss. The probability of loans defaulting for each risk rating, referred to as default factors, are estimated based on the historical pattern of loans migrating from one risk rating to another and to default status over time as well as the length of time that it takes losses to emerge. Estimated loan default factors, which are updated annually (or more frequently, if necessary), are multiplied by loan balances within each risk-rating category and again multiplied by a historical loss-given-default estimate for each loan type to determine an appropriate level of allowance by loan type. The historical loss-given-default estimates are also updated annually (or more frequently, if necessary) based on actual charge-off experience. This approach is applied to the commercial and industrial, commercial real estate and equipment financing components of the loan portfolio. In establishing the allowance for loan losses for commercial loans collectively evaluated for impairment, the Company also gives consideration to certain qualitative factors, including the macroeconomic environment and any potential imprecision inherent in its loan loss model that may result from having limited historical loan loss data which, in turn, may result in inaccurate probability of default and loss-given-default estimates. In this manner, historical portfolio experience, as described above, is not adjusted and the allowance for loan losses always includes a component attributable to qualitative factors, the degree of which may change from period to period as such qualitative factors indicate improving or worsening trends. The Company evaluates the qualitative factors on a quarterly basis in order to conclude that they continue to be appropriate. There were no significant changes in our approach to determining the qualitative component of the related allowance for loan losses during 2019. Retail Loans Collectively Evaluated for Impairment. Pools of retail loans possessing similar risk and loss characteristics are collectively evaluated for impairment. These loan pools include residential mortgage, home equity and other consumer loans that are not assigned individual loan risk ratings. Rather, the assessment of these portfolios, and the establishment of the related allowance for loan losses, is based upon a consideration of (i) historical portfolio loss experience over an appropriate look-back period and loss emergence period and (ii) certain qualitative factors. The qualitative component of the allowance for loan losses for retail loans collectively evaluated for impairment is intended to incorporate risks inherent in the portfolio, economic uncertainties, regulatory requirements and other subjective factors such as changes in underwriting standards. Accordingly, consideration is given to: (i) present and forecasted economic conditions, including unemployment rates; (ii) changes in industry trends, including the impact of new regulations, (iii) trends in property values; (iv) broader portfolio indicators, including delinquencies, non-performing loans, portfolio concentrations, and trends in the volume and terms of loans; and (v) portfolio-specific risk characteristics. Portfolio-specific risk characteristics considered include: (i) collateral values/loan-to-value ("LTV") ratios (above and below 70%); (ii) borrower credit scores under the FICO scoring system (above and below a score of 680); and (iii) other relevant portfolio risk elements such as income verification at the time of underwriting (stated income vs. non-stated income) and the property’s intended use (owner-occupied, non-owner occupied, second home, etc.), the combination of which results in a loan being classified as either “High”, “Moderate” or “Low” risk. These risk classifications are reviewed quarterly to ensure that changes within the portfolio, as well as economic indicators and industry developments, have been appropriately considered in establishing the related allowance for loan losses. In establishing the allowance for loan losses for retail loans collectively evaluated for impairment, the amount reflecting the Company’s consideration of qualitative factors is added to the amount attributable to historical portfolio loss experience. In this manner, historical charge-off data (whether periods or amounts) is not adjusted and the allowance for loan losses always includes a component attributable to qualitative factors, the degree of which may change from period to period as such qualitative factors indicate improving or worsening trends. The Company evaluates the qualitative factors on a quarterly basis in order to conclude that they continue to be appropriate. There were no significant changes in our approach to determining the qualitative component of the related allowance for loan losses during 2019. Individually Impaired Loans. The allowance for loan losses also includes specific allowances for individually impaired loans. Generally, the Company’s impaired loans consist of (i) classified commercial loans in excess of $1 million that have been placed on non-accrual status and (ii) loans classified as TDRs. Individually impaired loans are measured based upon observable market prices; the present value of expected future cash flows discounted at the loan’s original effective interest rate; or, in the case of collateral dependent loans, fair value of the collateral (based on appraisals and other market information) less cost to sell. If the recorded investment in a loan exceeds the amount measured as described in the preceding sentence, a specific allowance for loan losses would be established as a component of the overall allowance for loan losses or, in the case of a collateral dependent loan, a charge-off would be recorded for the difference between the loan’s recorded investment and management’s estimate of the fair value of the collateral (less cost to sell). It would be rare for the Company to identify a loan that meets the criteria stated above and requires a specific allowance or a charge-off and not deem it impaired solely as a result of the existence of a guarantee. People’s United performs an analysis of its impaired loans, including collateral dependent impaired loans, on a quarterly basis. Individually impaired collateral dependent loans are measured based upon the appraised value of the underlying collateral and other market information. Generally, the Company’s policy is to obtain updated appraisals for commercial collateral dependent loans when the loan is downgraded to a risk rating of “substandard” or “doubtful”, and the most recent appraisal is more than 12 months old or a determination has been made that the property has experienced a significant decline in value. Appraisals are prepared by independent, licensed third-party appraisers and are subject to review by the Company’s internal commercial appraisal department or external appraisers contracted by the commercial appraisal department. The conclusions of the external appraisal review are reviewed by the Company’s Chief Commercial Appraiser prior to acceptance. The Company’s policy with respect to impaired loans secured by residential real estate is to receive updated estimates of property values upon the loan being classified as non-performing (typically upon becoming 90 days past due). In determining the allowance for loan losses, People’s United gives appropriate consideration to the age of appraisals through its regular evaluation of other relevant qualitative and quantitative information. Specifically, between scheduled appraisals, property values are monitored within the commercial portfolio by reference to current originations of collateral dependent loans and the related appraisals obtained during underwriting as well as by reference to recent trends in commercial property sales as published by leading industry sources. Property values are monitored within the residential mortgage and home equity portfolios by reference to available market indicators, including real estate price indices within the Company’s primary lending areas. In most situations where a guarantee exists, the guarantee arrangement is not a specific factor in the assessment of the related allowance for loan losses. However, the assessment of a guarantor’s credit strength is reflected in the Company’s internal loan risk ratings which, in turn, are an important factor in its allowance for loan loss methodology for loans within the commercial and industrial, and commercial real estate portfolios. People’s United did not change its methodologies with respect to determining the allowance for loan losses during 2019. As part of its ongoing assessment of the allowance for loan losses, People’s United regularly makes refinements to certain underlying assumptions used in its methodologies. However, such refinements did not have a material impact on the allowanc

Acquisitions and Dispositions

Acquisitions and Dispositions	12 Months Ended
	Dec. 31, 2019
Business Combinations [Abstract]
Acquisitions and Dispositions	NOTE 2 – Acquisitions and Dispositions Acquisitions Completed in 2019 United Financial Bancorp, Inc. Effective November 1, 2019, People’s United completed its acquisition of United Financial Bancorp, Inc. (“United Financial”) based in Hartford, Connecticut. The fair value of the consideration transferred in the United Financial acquisition totaled $720.6 million and consisted of 44.4 million shares of People’s United common stock. At the acquisition date, United Financial operated 58 branch locations concentrated in central Connecticut and western Massachusetts. The assets acquired and liabilities assumed in this transaction were recorded by People’s United at their estimated fair values as of the effective date. The excess of the purchase price over the estimated fair value of the net assets acquired was recorded as goodwill and allocated to the Commercial Banking and Retail Banking segments. Merger-related expenses related to the United Financial acquisition recorded during the year ended December 31, 2019 totaled $22.2 million, including: (i) fees for investment advisory, legal, accounting and valuation services; (ii) costs associated with contract terminations and branch closings; and (iii) compensatory charges. The acquisition-date estimated fair values of the assets acquired and liabilities assumed in the acquisition of United Financial are s ummarized as follows: (in millions) Assets: Cash and cash equivalents $ 594.9 Securities 381.3 Loans 5,535.5 Goodwill 204.3 Core deposit intangible 41.5 Premises and equipment 61.8 BOLI 196.5 Lease ROU assets 56.3 Mortgage servicing rights 10.6 REO 1.2 Other assets 136.2 Total assets $ 7,220.1 Liabilities: Deposits $ 5,687.2 Borrowings 622.4 Lease liabilities 61.4 Other liabilities 128.5 Total liabilities $ 6,499.5 Total purchase price $ 720.6 Net deferred tax assets totaling $16.7 million were established in connection with recording the related purchase accounting adjustments (other than goodwill). Fair value adjustments to assets acquired (other than loans, see Note 5) and liabilities assumed are generally amortized on a straight-line basis over periods consistent with the average life, useful life and/or contractual term of the related assets and liabilities. BSB Bancorp, Inc. Effective April 1, 2019, People’s United completed its acquisition of BSB Bancorp, Inc. (“BSB Bancorp”) based in Belmont, Massachusetts. The fair value of the consideration transferred in the BSB Bancorp acquisition totaled $324.5 million and consisted of 19.7 million shares of People’s United common stock. At the acquisition date, BSB Bancorp operated six branches in the greater Boston area. The assets acquired and liabilities assumed in this transaction were recorded by People’s United at their estimated fair values as of the effective date. The excess of the purchase price over the estimated fair value of the net assets acquired was recorded as goodwill and allocated to the Commercial Banking and Retail Banking segments. Merger-related expenses related to the BSB Bancorp acquisition recorded during the years ended December 31, 2019 and 2018 totaled $8.1 million and $0.5 million, respectively, including: (i) fees for investment advisory, legal, accounting and valuation services; (ii) costs associated with contract terminations and branch closings; and (iii) compensatory charges. The acquisition-date estimated fair values of the assets acquired and liabilities assumed in the acquisition of BSB Bancorp are s ummarized as follows: (in millions) Assets: Cash and cash equivalents $ 108.7 Securities 175.8 Loans 2,642.9 Goodwill 144.9 Core deposit intangible 39.5 Premises and equipment 8.3 BOLI 36.8 Other assets 29.8 Total assets $ 3,186.7 Liabilities: Deposits $ 2,118.7 Borrowings 696.6 Other liabilities 46.9 Total liabilities $ 2,862.2 Total purchase price $ 324.5 Net deferred tax assets totaling $3.8 million were established in connection with recording the related purchase accounting adjustments (other than goodwill). Fair value adjustments to assets acquired (other than loans, see Note 5) and liabilities assumed are generally amortized on a straight-line basis over periods consistent with the average life, useful life and/or contractual term of the related assets and liabilities. The preceding summaries include adjustments to record the acquired assets and assumed liabilities at their respective fair values based on management’s best estimate using the information available at the time of the respective acquisitions. While there may be changes in the respective acquisition-date fair values of certain balance sheet amounts and other items, management does not expect that such changes, if any, will be material. Fair values of the major categories of assets acquired and liabilities assumed were determined as follows: Cash and Cash Equivalents The fair values of cash and cash equivalents approximate the respective carrying amounts because the instruments are payable on demand or have short-term maturities. Securities The fair values of securities acquired were based on quoted market prices. If a quoted market price for a certain security was not available, then a quoted price for a similar security in active markets was used to estimate fair value. Loans Loans acquired in connection with these acquisitions were recorded at fair value with no carryover of either United Financial's or BSB Bancorp's previously established allowance for loan losses. Fair value of the loans was determined using market participant assumptions in estimating the amount and timing of both principal and interest cash flows expected to be collected as adjusted for an estimate of future credit losses and prepayments and then applying a market-based discount rate to those cash flows. The acquired loans were evaluated upon the acquisition date and subsequently classified as either purchased performing or PCI (see Note 5). In the aggregate, United Financial loans totaling $136.5 million were deemed PCI (none for BSB Bancorp) and were recorded at a discount from the corresponding outstanding principal balance of $193.1 million. The remaining acquired loans were deemed purchased performing and had a fair value of $8.04 billion and an outstanding principal balance of $8.10 billion, resulting in a discount that will be accreted over the remaining lives of the loans. Included in the Consolidated Statements of Income for the year ended December 31, 2019 is approximately $125 million of interest income attributable to these acquisitions since the respective acquisition dates. Core Deposit Intangible The core deposit intangible represents the value of the relationships with the respective deposit customers. The fair values were estimated based on a cost savings methodology that gave appropriate consideration to expected customer attrition rates, net maintenance costs of the deposit base, the alternative cost of funds, the interest cost associated with the respective customer d eposits and discount rates. The core deposit intangibles will be amortized using an accelerated amortization method over a six attributable to the deposits will be recognized. Deposits The fair values of acquired savings and transaction deposit accounts were assumed to approximate the respective carrying amounts as these accounts have no stated maturity and are payable on demand. Time deposits were valued based on the present value of the contractual cash flows over the remaining period to maturity using a market rate. Borrowings The fair values of FHLB advances and other borrowings represent contractual repayments discounted using interest rates currently available on borrowings with similar characteristics and remaining maturities. The following table presents selected unaudited pro forma financial information of the Company, reflecting the acquisitions of United Financial and BSB Bancorp, assuming the acquisitions were completed as of the beginning of the respective periods: Years ended December 31 (in millions, except per common share data) 2019 2018 Selected Financial Results: Net interest income $ 1,582.5 $ 1,488.6 Provision for loan losses 28.3 30.0 Non-interest income 454.5 408.1 Non-interest expense 1,277.5 1,186.4 Net income 583.5 552.4 Net income available to common shareholders 569.4 538.3 EPS: Basic $ 1.31 $ 1.30 Diluted 1.30 1.29 The selected unaudited pro forma financial information is presented for illustrative purposes only and is not necessarily indicative of the financial results of the combined companies had the acquisitions actually been completed at the beginning of the periods presented, nor does it indicate future results for any other interim or full-year period. Merger-related expenses attributable to the acquisitions that were incurred by People’s United, United Financial and BSB Bancorp during the years ended December 31, 2019 and 2018 are not reflected in the selected unaudited pro forma financial information. Pro forma basic and diluted EPS were calculated using People’s United’s actual weighted-average common shares outstanding for the periods presented, plus the incremental common shares issued, assuming the acquisitions occurred at the beginning of the periods presented. VAR Technology Finance Effec tive January 2, 2019, the Bank completed its acquisition of VAR Technology Finance ("VAR"), a leasing and financing company headquartered in Mesquite, Texas. The fair value of the consideration transferred in the VAR acquisition consisted of $60.0 million in cash. Merger-related expenses totaling $1.9 million relating to this transaction were recorded during the year ended December 31, 2019. Sale of Branches On October 25, 2019, the Bank completed the sale of eight branches located in central Maine, including approximately: (i) $103 million in loans; (ii) $258 million in deposits; and (iii) $227 million of assets under management. The sale resulted in a gain, net of expenses, of $7.6 million, which is included in other non-interest income in the Consolidated Statements of Income. Acquisitions Completed in 2018 First Connecticut Bancorp, Inc. Effective October 1, 2018, the Company completed its acquisition of First Connecticut Bancorp, Inc. ("First Connecticut") based in Farmington, Connecticut. The fair value of the consideration transferred in the First Connecticut acquisition totaled $486.4 million and consisted of 28.4 million shares of People's United common stock. At the acquisition date, First Connecticut operated 25 branch locations throughout central Connecticut and western Massachusetts. The fair value of assets acquired and liabilities assumed in the First Connecticut acquisition totaled $3.45 billion and $2.96 billion, respectively. Merger-related expenses recorded during the years ended December 31, 2019 and 2018 related to this acquisition totaled $16.8 million and $8.8 million, respectively. Vend Lease Company Effective June 27, 2018, the Bank completed its acquisition of Vend Lease Company ("Vend Lease"), a Baltimore-based equipment finance company. The fair value of the consideration transferred in the Vend Lease acquisition consisted of $37.5 million in cash. In connection with this transaction, the Bank acquired a lease and loan portfolio with an acquisition-date estimated fair value of $68.8 million and recorded goodwill of $23.9 million. Merger-related expenses totaling $2.1 million relating to this transaction were recorded during the year ended December 31, 2018. Acquisitions Completed in 2017 LEAF Effective August 1, 2017, the Bank completed its acquisition of LEAF, a Philadelphia-based commercial equipment finance company. The fair value of the consideration transferred in the LEAF acquisition consisted of $220.0 million in cash. The fair value of assets acquired and liabilities assumed in this acquisition totaled $957.7 million and $737.7 million, respectively. Merger-related expenses recorded during the year ended December 31, 2017 related to this acquisition totaled $3.7 million. Prior to the acquisition, and in connection with its previous revolving warehouse debt facilities and term note securitization transactions, LEAF established bankruptcy-remote special-purpose entities ("SPEs") that issued term debt to institutional investors. These SPEs were variable interest entities ("VIEs"), of which LEAF was deemed the primary beneficiary, and, therefore, the related financings were treated as secured borrowings with the SPEs consolidated in LEAF's financial statements. Following the Company’s acquisition of LEAF, approximately $460 million of LEAF's borrowings were repaid prior to September 30, 2017, including all but one remaining securitization, which was repaid without penalty in June 2018. Suffolk Bancorp Effective April 1, 2017, People's United completed its acquisition of Suffolk Bancorp ("Suffolk") based in Riverhead, New York. The fair value of the consideration transferred in the Suffolk acquisition totaled $484.8 million and consisted of 26.6 million shares of People’s United common stock. At the acquisition date, Suffolk operated 27 branch locations in the greater Long Island area. The fair value of assets acquired and liabilities assumed in the Suffolk acquisition totaled $2.38 billion and $1.90 billion, respectively. Merger-related expenses recorded during the year ended December 31, 2017 related to this acquisition totaled $26.6 million.

Cash and Cash Equivalents

Cash and Cash Equivalents	12 Months Ended
	Dec. 31, 2019
Cash and Cash Equivalents [Abstract]
Cash and Cash Equivalents	NOTE 3 – Cash and Cash Equivalents A combination of reserves in the form of deposits with the FRB-NY and vault cash, totaling $171.6 million and $124.1 million at December 31, 2019 and 2018, respectively, were maintained to satisfy federal regulatory requirements. Vault cash is included in cash and due from banks, and interest-bearing deposits with the FRB-NY are included in short-term investments in the Consolidated Statements of Condition. These deposits represent an alternative to overnight federal funds sold and yielded 1.55% and 2.40% at December 31, 2019 and 2018, respectively. Cash and due from banks included restricted cash totaling $13.8 million at December 31, 2017 (none at December 31, 2019 and 2018) relating to one remaining securitization assumed in the acquisition of LEAF that was repaid in June 2018 (see Note 2). Short-term investments consist of the following cash equivalents: As of December 31 (in millions) 2019 2018 Interest-bearing deposits at the FRB-NY $ 219.4 $ 234.0 Money market mutual funds 5.7 26.3 Other (1) 91.7 6.0 Total short-term investments $ 316.8 $ 266.3 (1) Includes cash collateral posted for certain derivative positions at both December 31, 2019 and 2018.

Securities

Securities	12 Months Ended
	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Securities	NOTE 4 – Securities The amortized cost, gross unrealized gains and losses, and fair value of People’s United’s debt securities available-for-sale and debt securities held-to-maturity are as follows: As of December 31, 2019 (in millions) Amortized Gross Gross Fair Debt securities available-for-sale: U.S. Treasury and agency $ 689.5 $ 0.4 $ (2.8) $ 687.1 GSE mortgage-backed and CMO securities 2,856.3 25.0 (4.1) 2,877.2 Total debt securities available-for-sale $ 3,545.8 $ 25.4 $ (6.9) $ 3,564.3 Debt securities held-to-maturity: State and municipal $ 2,503.9 $ 142.0 $ (0.4) $ 2,645.5 GSE mortgage-backed securities 1,271.4 8.0 (0.3) 1,279.1 Corporate 92.4 1.5 — 93.9 Other 1.5 — — 1.5 Total debt securities held-to-maturity $ 3,869.2 $ 151.5 $ (0.7) $ 4,020.0 As of December 31, 2018 (in millions) Amortized Gross Gross Fair Debt securities available-for-sale: U.S. Treasury and agency $ 699.0 $ 0.1 $ (21.1) $ 678.0 GSE mortgage-backed securities 2,486.6 4.6 (48.2) 2,443.0 Total debt securities available-for-sale $ 3,185.6 $ 4.7 $ (69.3) $ 3,121.0 Debt securities held-to-maturity: State and municipal $ 2,352.4 $ 35.4 $ (18.4) $ 2,369.4 GSE mortgage-backed securities 1,367.5 — (33.2) 1,334.3 Corporate 70.9 0.5 (0.7) 70.7 Other 1.5 — — 1.5 Total debt securities held-to-maturity $ 3,792.3 $ 35.9 $ (52.3) $ 3,775.9 At December 31, 2019 and 2018, debt securities available-for-sale with fair values of $2.43 billion and $2.20 billion, respectively, and debt securities held-to-maturity with an amortized cost basis of $1.47 billion and $1.49 billion, respectively, were pledged as collateral for public deposits and for other purposes. The following table is a summary of the amortized cost, fair value and fully taxable equivalent (“FTE”) yield of debt securities as of December 31, 2019, based on remaining period to contractual maturity. Information for GSE mortgage-backed and CMO securities is based on the final contractual maturity dates without considering repayments and prepayments. Available-for-Sale Held-to-Maturity (dollars in millions) Amortized Fair FTE Amortized Fair FTE U.S. Treasury and agency: Within 1 year $ 158.4 $ 158.4 1.84 % $ — $ — — % After 1 but within 5 years 531.1 528.7 1.43 — — — Total 689.5 687.1 1.53 — — — GSE mortgage-backed and CMO Within 1 year — — — 2.7 2.7 2.04 After 1 but within 5 years 84.9 86.9 3.17 861.0 866.6 2.43 After 5 but within 10 years 855.1 867.7 2.67 120.2 121.3 2.52 After 10 years 1,916.3 1,922.6 2.35 287.5 288.5 2.17 Total 2,856.3 2,877.2 2.47 1,271.4 1,279.1 2.38 State and municipal: Within 1 year — — — 10.3 10.4 2.61 After 1 but within 5 years — — — 235.4 245.3 2.78 After 5 but within 10 years — — — 418.8 444.1 3.47 After 10 years — — — 1,839.4 1,945.7 3.81 Total — — — 2,503.9 2,645.5 3.65 Corporate: Within 1 year — — — 5.0 5.0 3.50 After 1 but within 5 years — — — 1.0 1.0 2.67 After 5 but within 10 years — — — 86.4 87.9 4.52 Total — — — 92.4 93.9 4.45 Other: Within 1 year — — — 1.5 1.5 2.46 Total — — — 1.5 1.5 2.46 Total: Within 1 year 158.4 158.4 1.84 19.5 19.6 2.74 After 1 but within 5 years 616.0 615.6 1.67 1,097.4 1,112.9 2.51 After 5 but within 10 years 855.1 867.7 2.67 625.4 653.3 3.43 After 10 years 1,916.3 1,922.6 2.35 2,126.9 2,234.2 3.59 Total $ 3,545.8 $ 3,564.3 2.29 % $ 3,869.2 $ 4,020.0 3.25 % The following tables summarize those debt securities with unrealized losses, segregated by the length of time the securities have been in a continuous unrealized loss position at the respective dates. Certain unrealized losses totaled less than $0.1 million. Continuous Unrealized Loss Position Less Than 12 Months 12 Months Or Longer Total As of December 31, 2019 (in millions)_ Fair Unrealized Fair Unrealized Fair Unrealized Debt securities available-for-sale: GSE mortgage-backed and CMO $ 565.4 $ (3.1) $ 509.3 $ (1.0) $ 1,074.7 $ (4.1) U.S. Treasury and agency 181.0 (0.4) 362.4 (2.4) 543.4 (2.8) Total debt securities available-for-sale $ 746.4 $ (3.5) $ 871.7 $ (3.4) $ 1,618.1 $ (6.9) Debt securities held-to-maturity: GSE mortgage-backed securities $ 100.9 $ (0.3) $ 9.1 $ — $ 110.0 $ (0.3) State and municipal 33.0 (0.2) 11.4 (0.2) 44.4 (0.4) Corporate 3.5 — 8.6 — 12.1 — Total debt securities held-to-maturity $ 137.4 $ (0.5) $ 29.1 $ (0.2) $ 166.5 $ (0.7) Continuous Unrealized Loss Position Less Than 12 Months 12 Months Or Longer Total As of December 31, 2018 (in millions) Fair Unrealized Fair Unrealized Fair Unrealized Debt securities available-for-sale: GSE mortgage-backed securities $ 132.4 $ (0.5) $ 1,656.3 $ (47.7) $ 1,788.7 $ (48.2) U.S. Treasury and agency — — 656.2 (21.1) 656.2 (21.1) Total debt securities available-for-sale $ 132.4 $ (0.5) $ 2,312.5 $ (68.8) $ 2,444.9 $ (69.3) Debt securities held-to-maturity: GSE mortgage-backed securities $ — $ — $ 1,334.3 $ (33.2) $ 1,334.3 $ (33.2) State and municipal 113.4 (0.7) 697.6 (17.7) 811.0 (18.4) Corporate 31.2 (0.6) 2.7 (0.1) 33.9 (0.7) Total debt securities held-to-maturity $ 144.6 $ (1.3) $ 2,034.6 $ (51.0) $ 2,179.2 $ (52.3) At December 31, 2019, approximately 8% of the 2,242 debt securities owned by the Company, consisting of 101 debt securities classified as available-for-sale and 79 debt securities classified as held-to-maturity, had gross unrealized losses totaling $6.9 million and $0.7 million, respectively. With respect to those securities with unrealized losses, all of the GSE mortgage-backed and CMO securities had AAA credit ratings and an average contractual maturity of 18 years. The state and municipal securities had an average credit rating of AA and a weighted average maturity of nine years. The cause of the gross unrealized losses with respect to all of the debt securities is directly related to changes in interest rates. At this time, management does not intend to sell such securities nor is it more likely than not, based upon available evidence, that management will be required to sell such securities prior to recovery. As such, management believes that all gross unrealized losses within the securities portfolio at December 31, 2019 are temporary impairments. No other-than-temporary impairment losses were recognized in the Consolidated Statements of Income for the years ended December 31, 2019, 2018 and 2017. People’s United uses the specific identification method to determine the cost of securities sold and records securities transactions on the trade date. People’s United sold (i) GSE mortgage-backed securities with an amortized cost of $235.5 million and recorded $10.0 million of gross realized losses in December 2018 and (ii) U.S. Treasury and CMO securities with a combined amortized cost of $291.3 million and recorded $10.0 million of gross realized losses in December 2017. Also in 2017, People’s United sold U.S. Treasury and CMO securities with a combined amortized cost of $486.9 million and recorded $15.7 million of gross realized losses. Including other minor gains and losses, net security gains (losses) totaled $0.2 million, $(9.8) million and $(25.4) million for the years ended December 31, 2019, 2018 and 2017, respectively. The components of net security gains (losses) are summarized below. Years ended December 31 (in millions) 2019 2018 2017 Debt securities: Gains $ 0.5 $ 0.1 $ 2.1 Losses (0.4) (10.0) (27.5) Total debt securities 0.1 (9.9) (25.4) Trading debt securities: Gains 0.1 0.1 — Losses — — — Total trading debt securities (1) 0.1 0.1 — Net security gains (losses) $ 0.2 $ (9.8) $ (25.4) (1) Net gains and losses on trading debt securities totaled less than $0.1 million for the year ended December 31, 2017. Effective January 1, 2018, People’s United adopted new accounting guidance that requires equity investments (other than equity method investments) to be measured at fair value with changes in fair value recognized in net income. At December 31, 2017, the Company’s securities portfolio included equity securities with an amortized cost of $9.6 million and a fair value of $8.7 million. Accordingly, upon adoption of this guidance, a cumulative-effect transition adjustment, representing the cumulative unrealized loss (net-of-tax) within AOCL was recorded, which served to decrease opening retained earnings by $0.6 million. For the years ended December 31, 2019 and 2018, People’s United recorded unrealized gains of $1.5 million and $0.6 million (included in other non-interest income in the Consolidated Statements of Income) relating to the change in fair value of its equity securities during the respective periods. The Bank, as a member of the FHLB of Boston, is currently required to purchase and hold shares of capital stock in the FHLB of Boston (total cost of $136.6 million and $124.2 million at December 31, 2019 and 2018, respectively) in an amount equal to its membership base investment plus an activity based investment determined according to the Bank’s level of outstanding FHLB advances. As a result of prior acquisitions, the Bank acquired shares of capital stock in the FHLB of New York (total cost of $0.7 million at both December 31, 2019 and 2018). Based on the current capital adequacy and liquidity position of both the FHLB of Boston and the FHLB of New York, management believes there is no impairment in the Company’s investment at December 31, 2019 and the cost of the investment approximates fair value. Dividend income on FHLB capital stock totaled $7.0 million, $8.3 million and $6.6 million for the years ended December 31, 2019, 2018 and 2017, respectively. The Bank, as a member of the Federal Reserve Bank system, is currently required to purchase and hold shares of capital stock in the FRB-NY (total cost of $203.8 million and $178.5 million at December 31, 2019 and 2018, respectively) in an amount equal to 6% of its capital and surplus. Based on the current capital adequacy and liquidity position of the FRB-NY, management believes there is no impairment in the Company’s investment at December 31, 2019 and the cost of the investment approximates fair value. Dividend income on FRB-NY capital stock totaled $3.8 million, $5.1 million and $3.7 million for the years ended December 31, 2019, 2018 and 2017, respectively.

Loans

Loans	12 Months Ended
	Dec. 31, 2019
Receivables [Abstract]
Loans	NOTE 5 – Loans For purposes of disclosures related to the credit quality of financing receivables and the allowance for loan losses, People’s United has identified two loan portfolio segments, Commercial and Retail, which are comprised of the following loan classes: • Commercial Portfolio : commercial real estate; commercial and industrial; and equipment financing. • Retail Portfolio : residential mortgage; home equity; and other consumer. Loans acquired in connection with business combinations are referred to as ‘acquired’ loans as a result of the manner in which they are accounted for (see further discussion under ‘Acquired Loans’ in Note 1). All other loans are referred to as ‘originated’ loans. Accordingly, selected credit quality disclosures that follow are presented separately for the ‘originated’ loan portfolio and the ‘acquired’ loan portfolio. The following table summarizes People’s United’s loans by loan portfolio segment and class: 2019 2018 As of December 31 (in millions) Originated Acquired Total Originated Acquired Total Commercial: Commercial real estate $ 10,012.5 $ 4,749.8 $ 14,762.3 $ 9,798.5 $ 1,851.1 $ 11,649.6 Commercial and industrial 9,763.1 1,278.5 11,041.6 8,292.3 796.6 9,088.9 Equipment financing 4,706.1 204.3 4,910.4 3,937.7 401.5 4,339.2 Total Commercial Portfolio 24,481.7 6,232.6 30,714.3 22,028.5 3,049.2 25,077.7 Retail: Residential mortgage: Adjustable-rate 5,366.0 1,698.8 7,064.8 5,854.1 807.9 6,662.0 Fixed-rate 1,222.9 2,030.4 3,253.3 935.1 557.1 1,492.2 Total residential mortgage 6,588.9 3,729.2 10,318.1 6,789.2 1,365.0 8,154.2 Home equity and other consumer: Home equity 1,625.1 781.4 2,406.5 1,789.5 173.0 1,962.5 Other consumer 39.7 117.5 157.2 42.8 4.2 47.0 Total home equity and 1,664.8 898.9 2,563.7 1,832.3 177.2 2,009.5 Total Retail Portfolio 8,253.7 4,628.1 12,881.8 8,621.5 1,542.2 10,163.7 Total loans $ 32,735.4 $ 10,860.7 $ 43,596.1 $ 30,650.0 $ 4,591.4 $ 35,241.4 Net deferred loan costs, which are included in loans by respective class and accounted for as interest yield adjustments, totaled $87.5 million at December 31, 2019 and $94.6 million at December 31, 2018. At December 31, 2019, 25%, 22% and 18% of the Company’s loans by outstanding principal amount were to customers located within Connecticut, Massachusetts and New York, respectively. Loans to customers located in the New England states as a group represented 58% and 56% of total loans at December 31, 2019 and 2018, respectively. Substantially the entire equipment financing portfolio (95% at both December 31, 2019 and 2018) was to customers located outside of New England. At December 31, 2019, 30% of the equipment financing portfolio was to customers located in Texas, California and New York, and no other state exposure was greater than 7%. Included in the Commercial portfolio are construction loans totaling $1.1 billion and $651.2 million at December 31, 2019 and 2018, respectively, net of the unadvanced portion of such loans totaling $798.3 million and $588.2 million, respectively. At December 31, 2019 and 2018, residential mortgage loans included $1.1 billion and $1.2 billion, respectively, of interest-only loans. People’s United’s underwriting guidelines and requirements for such loans are generally more restrictive than those applied to other types of residential mortgage products. Also included in residential mortgage loans are construction loans totaling $40.5 million and $57.3 million at December 31, 2019 and 2018, respectively, net of the unadvanced portion of such loans totaling $14.6 million and $21.5 million, respectively. People’s United sells newly-originated residential mortgage loans in the secondary market, without recourse. Net gains on sales of residential mortgage loans totaled $1.9 million, $1.2 million and $3.2 million for the years ended December 31, 2019, 2018 and 2017, respectively. Loans held-for-sale at December 31, 2019 and 2018 included newly-originated residential mortgage loans with carrying amounts of $19.7 million and $19.5 million, respectively. At December 31, 2019, loans held-for-sale also included $333.7 million of consumer loans and $157.9 million of commercial loans previously acquired in the United Financial acquisition. During 2019, 2018 and 2017, the Company sold acquired loans with outstanding principal balances totaling $10.1 million, $10.0 million and $7.9 million, respectively, (carrying amounts of $7.1 million, $4.4 million and $5.0 million, respectively) and recognized net gains on sales totaling $0.4 million, $1.8 million and $2.4 million, respectively. The following table presents a summary, by loan portfolio segment, of activity in the allowance for loan losses for the years ended December 31, 2019, 2018 and 2017. With respect to the originated portfolio, an allocation of a portion of the allowance to one segment does not preclude its availability to absorb losses in another segment. Commercial Retail (in millions) Originated Acquired Total Originated Acquired Total Total Balance at December 31, 2016 $ 198.8 $ 6.1 $ 204.9 $ 24.2 $ 0.2 $ 24.4 $ 229.3 Charge-offs (17.1) (4.4) (21.5) (6.4) — (6.4) (27.9) Recoveries 4.6 0.3 4.9 2.1 — 2.1 7.0 Net loan charge-offs (12.5) (4.1) (16.6) (4.3) — (4.3) (20.9) Provision for loan losses 14.8 1.4 16.2 9.8 — 9.8 26.0 Balance at December 31, 2017 201.1 3.4 204.5 29.7 0.2 29.9 234.4 Charge-offs (19.5) (8.1) (27.6) (3.3) — (3.3) (30.9) Recoveries 3.5 1.3 4.8 2.1 — 2.1 6.9 Net loan charge-offs (16.0) (6.8) (22.8) (1.2) — (1.2) (24.0) Provision for loan losses 20.5 7.3 27.8 2.2 — 2.2 30.0 Balance at December 31, 2018 205.6 3.9 209.5 30.7 0.2 30.9 240.4 Charge-offs (20.0) (7.5) (27.5) (4.0) — (4.0) (31.5) Recoveries 5.0 1.3 6.3 3.1 — 3.1 9.4 Net loan charge-offs (15.0) (6.2) (21.2) (0.9) — (0.9) (22.1) Provision for loan losses 26.2 3.4 29.6 (1.1) (0.2) (1.3) 28.3 Balance at December 31, 2019 $ 216.8 $ 1.1 $ 217.9 $ 28.7 $ — $ 28.7 $ 246.6 The following tables summarize, by loan portfolio segment and impairment methodology, the allowance for loan losses and related portfolio balances: As of December 31, 2019 (in millions) Commercial Retail Total Portfolio Allowance Portfolio Allowance Portfolio Allowance Originated loans: Collectively evaluated for impairment $ 22,938.3 $ 207.8 $ 9,592.8 $ 26.5 $ 32,531.1 $ 234.3 Individually evaluated for impairment 115.0 9.0 89.2 2.2 204.2 11.2 Acquired loans: PCI (1) 308.5 — 87.5 — 396.0 — Purchased performing: Collectively evaluated for impairment 7,344.9 1.1 3,104.8 — 10,449.7 1.1 Individually evaluated for impairment 7.6 — 7.5 — 15.1 — Total $ 30,714.3 $ 217.9 $ 12,881.8 $ 28.7 $ 43,596.1 $ 246.6 As of December 31, 2018 (in millions) Commercial Retail Total Portfolio Allowance Portfolio Allowance Portfolio Allowance Originated loans: Collectively evaluated for impairment $ 21,900.1 $ 198.9 $ 8,535.0 $ 28.4 $ 30,435.1 $ 227.3 Individually evaluated for impairment 128.4 6.7 86.5 2.3 214.9 9.0 Acquired loans: PCI (1) 300.3 2.2 99.6 0.1 399.9 2.3 Purchased performing: Collectively evaluated for impairment 2,744.4 1.7 1,439.1 — 4,183.5 1.7 Individually evaluated for impairment 4.5 — 3.5 0.1 8.0 0.1 Total $ 25,077.7 $ 209.5 $ 10,163.7 $ 30.9 $ 35,241.4 $ 240.4 (1) PCI loans are evaluated for impairment on a pool basis. The recorded investments, by class of loan, in originated non-performing loans are summarized as follows: As of December 31 (in millions) 2019 2018 2017 Commercial: Commercial real estate $ 29.8 $ 33.5 $ 23.7 Commercial and industrial 32.1 38.0 32.6 Equipment financing 46.2 42.0 44.3 Total (1) 108.1 113.5 100.6 Retail: Residential mortgage 36.3 38.9 32.7 Home equity 12.6 15.3 15.4 Other consumer — — — Total (2) 48.9 54.2 48.1 Total $ 157.0 $ 167.7 $ 148.7 (1) Reported net of government guarantees totaling $1.3 million, $1.9 million and $3.1 million at December 31, 2019, 2018 and 2017, respectively. These government guarantees relate, almost entirely, to guarantees provided by the Small Business Administration as well as selected other Federal agencies and represent the carrying value of the loans that are covered by such guarantees, the extent of which (i.e. full or partial) varies by loan. At December 31, 2019, the principal loan classes to which these government guarantees relate are commercial and industrial loans (95%) and commercial real estate loans (5%). (2) Includes $17.0 million, $24.8 million and $15.2 million of loans in the process of foreclosure at December 31, 2019, 2018 and 2017, respectively. The preceding table excludes acquired loans that are (i) accounted for as PCI loans and/or (ii) covered by an FDIC loss-share agreement (“LSA”) which totaled $53.5 million at December 31, 2019; $44.1 million at December 31, 2018; and $25.1 million at December 31, 2017. Such loans otherwise meet People’s United’s definition of a non-performing loan but are excluded because the loans are included in loan pools that are considered performing and/or credit losses are covered by an FDIC LSA. The discounts arising from recording these loans at fair value were due, in part, to credit quality. Accordingly, such loans are generally accounted for on a pool basis and the accretable yield on the pools is being recognized as interest income over the life of the loans based on expected cash flows at the pool level. In addition, the table excludes purchased performing loans totaling $13.6 million, $6.0 million and $4.7 million at December 31, 2019, 2018 and 2017, respectively, of which $13.2 million, $6.0 million and $4.7 million, respectively at those dates, became non-performing subsequent to acquisition. If interest payments on all loans classified as non-performing at December 31, 2019, 2018 and 2017 had been made during the respective years in accordance with the loan agreements, interest income of $18.5 million, $18.1 million and $16.2 million would have been recognized on such loans for the respective years. Interest income actually recognized on non-performing loans totaled $2.3 million, $2.9 million and $1.7 million for the years ended December 31, 2019, 2018 and 2017, respectively. At December 31, 2019 and 2018, People’s United’s recorded investment in loans classified as TDRs totaled $177.0 million and $179.4 million, respectively. The related allowance for loan losses was $4.3 million at December 31, 2019 and $4.5 million at December 31, 2018. Interest income recognized on TDRs totaled $5.5 million, $6.1 million and $4.7 million for the years ended December 31, 2019, 2018 and 2017, respectively. Fundings under commitments to lend additional amounts to borrowers with loans classified as TDRs were immaterial for the years ended December 31, 2019, 2018 and 2017. Loans that were modified and classified as TDRs during 2019 principally involve reduced payment and/or payment deferral, extension of term (generally no more than two years for commercial loans and five years for retail loans) and/or a temporary reduction of interest rate (generally less than 200 basis points). The following tables summarize, by class of loan, the recorded investments in loans modified as TDRs during the years ended December 31, 2019 and 2018. For purposes of this disclosure, recorded investments represent amounts immediately prior to and subsequent to the restructuring. Year ended December 31, 2019 (dollars in millions) Number of Pre-Modification Post-Modification Commercial: Commercial real estate (1) 12 $ 17.2 $ 17.2 Commercial and industrial (2) 33 31.9 31.9 Equipment financing (3) 37 24.9 24.9 Total 82 74.0 74.0 Retail: Residential mortgage (4) 85 26.3 26.3 Home equity (5) 102 9.0 9.0 Other consumer — — — Total 187 35.3 35.3 Total 269 $ 109.3 $ 109.3 (1) Represents the following concessions: extension of term (7 contracts; recorded investment of $2.1 million); reduced payment and/or payment deferral (1 contract; recorded investment of $0.6 million); or a combination of concessions (4 contracts; recorded investment of $14.5 million). (2) Represents the following concessions: extension of term (26 contracts; recorded investment of $26.4 million); reduced payment and/or payment deferral (3 contracts; recorded investment of $0.8 million); or a combination of concessions (4 contracts; recorded investment of $4.7 million). (3) Represents the following concessions: extension of term (5 contracts; recorded investment of $1.6 million); reduced payment and/or payment deferral (26 contracts; recorded investment of $18.9 million); or a combination of concessions (6 contracts; recorded investment of $4.4 million). (4) Represents the following concessions: loans restructured through bankruptcy (45 contracts; recorded investment of $9.9 million); reduced payment and/or payment deferral (24 contracts; recorded investment of $10.1 million); or a combination of concessions (16 contracts; recorded investment of $6.3 million). (5) Represents the following concessions: loans restructured through bankruptcy (54 contracts; recorded investment of $3.2 million); reduced payment and/or payment deferral (18 contracts; recorded investment of $2.9 million); or a combination of concessions (30 contracts; recorded investment of $2.9 million). Year ended December 31, 2018 (dollars in millions) Number of Pre-Modification Post-Modification Commercial: Commercial real estate (1) 13 $ 27.6 $ 27.6 Commercial and industrial (2) 47 73.1 73.1 Equipment financing (3) 31 31.6 31.6 Total 91 132.3 132.3 Retail: Residential mortgage (4) 38 9.5 9.5 Home equity (5) 79 7.3 7.3 Other consumer — — — Total 117 16.8 16.8 Total 208 $ 149.1 $ 149.1 (1) Represents the following concessions: extension of term (9 contracts; recorded investment of $24.1 million); reduced payment and/or payment deferral (1 contract; recorded investment of $0.5 million); or a combination of concessions (3 contracts; recorded investment of $3.0 million). (2) Represents the following concessions: extension of term (31 contracts; recorded investment of $48.4 million); reduced payment and/or payment deferral (11 contracts; recorded investment of $23.8 million); or a combination of concessions (5 contracts; recorded investment of $0.9 million). (3) Represents the following concessions: extension of term (3 contracts; recorded investment of $4.2 million); reduced payment and/or payment deferral (16 contracts; recorded investment of $17.6 million); or a combination of concessions (12 contracts; recorded investment of $9.8 million). (4) Represents the following concessions: loans restructured through bankruptcy (21 contracts; recorded investment of $3.7 million); reduced payment and/or payment deferral (10 contracts; recorded investment of $3.5 million); or a combination of concessions (7 contracts; recorded investment of $2.3 million). (5) Represents the following concessions: loans restructured through bankruptcy (49 contracts; recorded investment of $3.6 million); reduced payment and/or payment deferral (10 contracts; recorded investment of $1.3 million); or a combination of concessions (20 contracts; recorded investment of $2.4 million). The following is a summary, by class of loan, of information related to TDRs completed within the previous 12 months that subsequently defaulted during the years ended December 31, 2019 and 2018. For purposes of this disclosure, the previous 12 months is measured from January 1 of the respective prior year and a default represents a previously-modified loan that became past due 30 days or more during 2019 or 2018. 2019 2018 Years ended December 31 (dollars in millions) Number of Recorded Number of Recorded Commercial: Commercial real estate — $ — — $ — Commercial and industrial 2 2.4 12 6.7 Equipment financing 8 5.3 6 3.5 Total 10 7.7 18 10.2 Retail: Residential mortgage 5 2.2 7 1.6 Home equity 12 1.0 13 0.7 Other consumer — — — — Total 17 3.2 20 2.3 Total 27 $ 10.9 38 $ 12.5 People’s United’s impaired loans consist of certain loans that have been placed on non-accrual status, including all TDRs. The following table summarizes, by class of loan, information related to individually-evaluated impaired loans. 2019 2018 As of December 31 (in millions) Unpaid Recorded Related Unpaid Recorded Related Without a related allowance for loan losses: Commercial: Commercial real estate $ 28.9 $ 25.9 $ — $ 31.0 $ 28.1 $ — Commercial and industrial 31.0 25.9 — 45.6 42.0 — Equipment financing 24.1 21.8 — 20.2 18.0 — Retail: Residential mortgage 68.4 60.8 — 66.8 59.3 — Home equity 26.0 23.0 — 23.8 20.3 — Other consumer — — — — — — Total $ 178.4 $ 157.4 $ — $ 187.4 $ 167.7 $ — With a related allowance for loan losses: Commercial: Commercial real estate $ 21.5 $ 21.0 $ 3.4 $ 23.8 $ 21.8 $ 1.6 Commercial and industrial 20.0 16.4 3.9 12.6 10.2 2.4 Equipment financing 12.4 11.6 1.7 16.2 12.8 2.7 Retail: Residential mortgage 11.6 11.5 1.5 8.8 8.8 1.7 Home equity 1.4 1.4 0.7 1.7 1.6 0.7 Other consumer — — — — — — Total $ 66.9 $ 61.9 $ 11.2 $ 63.1 $ 55.2 $ 9.1 Total impaired loans: Commercial: Commercial real estate $ 50.4 $ 46.9 $ 3.4 $ 54.8 $ 49.9 $ 1.6 Commercial and industrial 51.0 42.3 3.9 58.2 52.2 2.4 Equipment financing 36.5 33.4 1.7 36.4 30.8 2.7 Total 137.9 122.6 9.0 149.4 132.9 6.7 Retail: Residential mortgage $ 80.0 $ 72.3 $ 1.5 $ 75.6 $ 68.1 $ 1.7 Home equity 27.4 24.4 0.7 25.5 21.9 0.7 Other consumer — — — — — — Total 107.4 96.7 2.2 101.1 90.0 2.4 Total $ 245.3 $ 219.3 $ 11.2 $ 250.5 $ 222.9 $ 9.1 The following table summarizes, by class of loan, the average recorded investment and interest income recognized on impaired loans for the periods indicated. The average recorded investment amounts are based on month-end balances. 2019 2018 2017 Years ended December 31 (in millions) Average Interest Average Interest Average Interest Commercial: Commercial real estate $ 39.6 $ 1.1 $ 40.2 $ 1.1 $ 55.8 $ 1.2 Commercial and industrial 44.5 1.6 49.6 2.8 63.4 1.9 Equipment financing 27.0 0.3 38.4 0.1 44.4 0.4 Total 111.1 3.0 128.2 4.0 163.6 3.5 Retail: Residential mortgage 68.3 2.1 68.7 1.9 71.8 1.7 Home equity 23.0 0.6 20.9 0.5 21.2 0.4 Other consumer — — — — — — Total 91.3 2.7 89.6 2.4 93.0 2.1 Total $ 202.4 $ 5.7 $ 217.8 $ 6.4 $ 256.6 $ 5.6 The following tables summarize, by class of loan, aging information for originated loans: Past Due As of December 31, 2019 (in millions) Current 30-89 90 Days Total Total Commercial: Commercial real estate $ 9,983.5 $ 7.8 $ 21.2 $ 29.0 $ 10,012.5 Commercial and industrial 9,738.0 10.5 14.6 25.1 9,763.1 Equipment financing 4,591.4 94.7 20.0 114.7 4,706.1 Total 24,312.9 113.0 55.8 168.8 24,481.7 Retail: Residential mortgage 6,534.3 31.6 23.0 54.6 6,588.9 Home equity 1,615.0 5.0 5.1 10.1 1,625.1 Other consumer 39.5 0.2 — 0.2 39.7 Total 8,188.8 36.8 28.1 64.9 8,253.7 Total originated loans $ 32,501.7 $ 149.8 $ 83.9 $ 233.7 $ 32,735.4 Included in the “Current” and “30-89 Days” categories above are early non-performing commercial real estate loans, commercial and industrial loans, and equipment financing loans totaling $8.6 million, $18.8 million and $26.2 million, respectively, and $20.8 million of retail loans in the process of foreclosure or bankruptcy. These loans are less than 90 days past due but have been placed on non-accrual status as a result of having been identified as presenting uncertainty with respect to the collectability of interest and principal. Past Due As of December 31, 2018 (in millions) Current 30-89 90 Days Total Total Commercial: Commercial real estate $ 9,762.1 $ 23.0 $ 13.4 $ 36.4 $ 9,798.5 Commercial and industrial 8,261.5 6.9 23.9 30.8 8,292.3 Equipment financing 3,855.3 68.8 13.6 82.4 3,937.7 Total 21,878.9 98.7 50.9 149.6 22,028.5 Retail: Residential mortgage 6,723.2 38.6 27.4 66.0 6,789.2 Home equity 1,776.0 5.8 7.7 13.5 1,789.5 Other consumer 42.7 0.1 — 0.1 42.8 Total 8,541.9 44.5 35.1 79.6 8,621.5 Total originated loans $ 30,420.8 $ 143.2 $ 86.0 $ 229.2 $ 30,650.0 Included in the “Current” and “30-89 Days” categories above are early non-performing commercial real estate loans, commercial and industrial loans, and equipment financing loans totaling $20.3 million, $15.8 million and $28.4 million, respectively, and $19.1 million of retail loans in the process of foreclosure or bankruptcy. These loans are less than 90 days past due but have been placed on non-accrual status as a result of having been identified as presenting uncertainty with respect to the collectability of interest and principal. Commercial Credit Quality Indicators The Company utilizes an internal loan risk rating system as a means of monitoring portfolio credit quality and identifying both problem and potential problem loans. Under the Company’s risk rating system, loans not meeting the criteria for problem and potential problem loans as specified below are considered to be “Pass”-rated loans. Problem and potential problem loans are classified as either “Special Mention,” “Substandard” or “Doubtful.” Loans that do not currently expose the Company to sufficient enough risk of loss to warrant classification as either Substandard or Doubtful, but possess weaknesses that deserve management’s close attention, are classified as Special Mention. Substandard loans represent those credits characterized by the distinct possibility that the Company will sustain some loss if the deficiencies are not corrected. Loans classified as Doubtful possess all the weaknesses inherent in those classified Substandard with the added characteristic that collection or liquidation in full, on the basis of existing facts, conditions and values, is highly questionable and/or improbable. Risk ratings on commercial loans are subject to ongoing monitoring by lending and credit personnel with such ratings updated annually or more frequently, if warranted. The Company’s internal Loan Review function is responsible for independently evaluating the appropriateness of those credit risk ratings in connection with its cyclical reviews, the approach to which is risk-based and determined by reference to underlying portfolio credit quality and the results of prior reviews. Differences in risk ratings noted in conjunction with such periodic portfolio loan reviews, if any, are reported to management each month. Retail Credit Quality Indicators Pools of retail loans possessing similar risk and loss characteristics are collectively evaluated for impairment. These loan pools include residential mortgage, home equity and other consumer loans that are not assigned individual loan risk ratings. Rather, the assessment of these portfolios is based upon a consideration of historical portfolio loss experience, broader portfolio indicators, including trends in delinquencies, non-performing loans and portfolio concentrations, and portfolio-specific risk characteristics, the combination of which determines whether a loan is classified as “High”, “Moderate” or “Low” risk. The portfolio-specific risk characteristics considered include: (i) collateral values/LTV ratios (above and below 70%); (ii) borrower credit scores under the FICO scoring system (above and below a score of 680); and (iii) other relevant portfolio risk elements such as income verification at the time of underwriting (stated income vs. non-stated income) and the property’s intended use (owner-occupied, non-owner occupied, second home, etc.). In classifying a loan as either “High”, “Moderate” or “Low” risk, the combination of each of the aforementioned risk characteristics is considered for that loan, resulting, effectively, in a “matrix approach” to its risk classification. These risk classifications are reviewed quarterly to ensure that they continue to be appropriate in light of changes within the portfolio and/or economic indicators as well as other industry developments. For example, to the extent LTV ratios exceed 70% (reflecting a weaker collateral position for the Company) or borrower FICO scores are less than 680 (reflecting weaker financial standing and/or credit history of the customer), the loans are considered to have an increased level of inherent loss. As a result, a loan with a combination of these characteristics would generally be classified as “High” risk. Conversely, as LTV ratios decline (reflecting a stronger collateral position for the Company) or borrower FICO scores exceed 680 (reflecting stronger financial standing and/or credit history of the customer), the loans are considered to have a decreased level of inherent loss. A loan with a combination of these characteristics would generally be classified as “Low” risk. This analysis also considers (i) the extent of underwriting that occurred at the time of origination (direct income verification provides further support for credit decisions) and (ii) the property’s intended use (owner-occupied properties are less likely to default compared to ‘investment-type’ non-owner occupied properties, second homes, etc.). Loans not otherwise deemed to be “High” or “Low” risk are classified as “Moderate” risk. LTV ratios and FICO scores are determined at origination and updated periodically throughout the life of the loan. LTV ratios are updated for loans 90 days past due and FICO scores are updated for the entire portfolio quarterly. The portfolio stratification (“High”, “Moderate” and “Low” risk) and identification of the corresponding credit quality indicators also occurs quarterly. Commercial and Retail loans are also evaluated to determine whether they are impaired loans. Such loans are included in the tabular disclosures of credit quality indicators that follow. Acquired Loan Credit Quality Indicators Upon acquiring a loan portfolio, the Company’s internal Loan Review function undertakes the process of assigning risk ratings to all commercial loans in accordance with the Company’s established policy, which may differ in certain respects from the risk rating policy of the predecessor company. The length of time necessary to complete this process varies based on the size of the acquired portfolio, the quality of the documentation maintained in the underlying loan files and the extent to which the predecessor company followed a risk rating approach comparable to People’s United’s. As a result, while acquired loans are risk rated, there are occasions when such ratings may be deemed “preliminary” until the Company’s re-rating process has been completed. The following tables summarize, by class of loan, credit quality indicators: As of December 31, 2019 (in millions) Commercial Commercial Equipment Total Commercial: Originated loans: Pass $ 9,736.4 $ 9,223.5 $ 4,231.6 $ 23,191.5 Special mention 197.6 294.8 76.5 568.9 Substandard 75.4 242.7 398.0 716.1 Doubtful 3.1 2.1 — 5.2 Total originated loans 10,012.5 9,763.1 4,706.1 24,481.7 Acquired loans: Pass 4,485.9 1,168.2 201.9 5,856.0 Special mention 136.7 35.6 — 172.3 Substandard 127.2 73.1 2.4 202.7 Doubtful — 1.6 — 1.6 Total acquired loans 4,749.8 1,278.5 204.3 6,232.6 Total $ 14,762.3 $ 11,041.6 $ 4,910.4 $ 30,714.3 As of December 31, 2019 (in millions) Residential Home Other Total Retail: Originated loans: Low risk $ 3,225.3 $ 747.3 $ 24.9 $ 3,997.5 Moderate risk 2,649.0 548.5 5.9 3,203.4 High risk 714.6 329.3 8.9 1,052.8 Total originated loans 6,588.9 1,625.1 39.7 8,253.7 Acquired loans: Low risk 1,184.7 — — 1,184.7 Moderate risk 2,309.3 — — 2,309.3 High risk 235.2 781.4 117.5 1,134.1 Total acquired loans 3,729.2 781.4 117.5 4,628.1 Total $ 10,318.1 $ 2,406.5 $ 157.2 $ 12,881.8 As of December 31, 2018 (in millions) Commercial Commercial Equipment Total Commercial: Originated loans: Pass $ 9,607.0 $ 7,855.7 $ 3,549.3 $ 21,012.0 Special mention 105.5 196.9 92.1 394.5 Substandard 85.2 239.3 296.3 620.8 Doubtful 0.8 0.4 — 1.2 Total originated loans 9,798.5 8,292.3 3,937.7 22,028.5 Acquired loans: Pass 1,766.2 719.6 394.0 2,879.8 Special mention 27.3 14.6 4.7 46.6 Substandard 57.6 62.4 2.8 122.8 Doubtful — — — — Total acquired loans 1,851.1 796.6 401.5 3,049.2 Total $ 11,649.6 $ 9,088.9 $ 4,339.2 $ 25,077.7 As of December 31, 2018 (in millions) Residential Home Other Total Retail: Originated loans: Low risk $ 2,912.8 $ 834.5 $ 27.3 $ 3,774.6 Moderate risk 3,360.9 576.4 5.9 3,943.2 High risk 515.5 378.6 9.6 903.7 Total originated loans 6,789.2 1,789.5 42.8 8,621.5 Acquired loans: Low risk 506.1 — — 506.1 Moderate risk 639.6 — — 639.6 High risk 219.3 173.0 4.2 396.5 Total acquired loans 1,365.0 173.0 4.2 1,542.2 Total $ 8,154.2 $ 1,962.5 $ 47.0 $ 10,163.7 Acquired PCI Loans At the respective acquisition dates, on an aggregate basis, the PCI loan portfolio had contractually required principal and interest payments receivable of $7.95 billion; expected cash flows of $7.35 billion; and a fair value (initial carrying amount) of $5.62 billion. The difference between the contractually required principal and interest payments receivable and the expected cash flows ($603.1 million) represented the initial nonaccretable difference. The difference between the expected cash flows and fair value ($1.73 billion) represented the initial accretable yield. Both the contractually required principal and interest payments receivable and the expected cash flows reflect anticipated prepayments, determined based on historical portfolio experience. At December 31, 2019, the outstanding principal balance and carrying amount of the PCI loan portfolio were $532.2 million and $396.0 million, respectively ($491.6 million and $399.9 million, respectively, at December 31, 2018). The following table summarizes activity in the accretable yield for the PCI loan portfolio: Years ended December 31 (in millions) 2019 2018 2017 Balance at beginning of period $ 189.7 $ 219.7 $ 255.4 Acquisitions 25.5 27.1 13.1 Accretion (21.0) (24.6) (29.1) Reclassification from nonaccretable difference for loans with improved cash flows (1) — — — Other changes in expected cash flows (2) (56.7) (32.5) (19.7) Balance at end of period $ 137.5 $ 189.7 $ 219.7 (1) Results in increased interest accretion as a prospective yield adjustment over the remaining life of the corresponding pool of loans. (2) Represents changes in cash flows expected to be collected due to factors other than credit (e.g. changes in prepayment assumptions and/or changes in interest rates on variable rate loans), as well as loan sales, modifications and payoffs. FDIC Loss-Share Receivable On April 16, 2010, the Bank entered into a definitive purchase and assumption agreement (the “Agreement”) with the FDIC pursuant to which the Bank assumed all of the deposits, certain assets and the banking operations of Butler Bank. The Agreement also provides for loss-share coverage by the FDIC, up to certain limits, on all covered assets (loans and REO). The FDIC is obligated to reimburse the Bank for 80% of any future losses on covered assets up to $34.0 million. The Bank will reimburse the FDIC for 80% of recoveries with respect to losses for which the FDIC paid 80% reimbursement under the loss-sharing coverage. The asset arising from the loss-sharing coverage, referred to as the “FDIC loss-share receivable,” totaled $0.1 million and $0.2 million at December 31, 2019 and 2018, respectively, and is included in other assets in the Consolidated Statements of Condition. The FDIC loss-share receivable is measured separately from the covered loans because the coverage is not contractually embedded in the loans and is not transferable should the Bank choose to dispose of the covered loans. The FDIC loss-share receivable will be reduced as losses are realized on covered assets and as loss-sharing payments are received from the FDIC. Realized losses in excess of the acquisition date estimates will result in an increase in the FDIC loss-share receivable. Conversely, the FDIC loss-share receivable will be reduced if realized losses are less than the estimates at acquisition. The amount ultimately collected for the FDIC loss-share receivable is dependent upon the performance of the underlying covered assets over time and claims submitted to the FDIC. In the event that losses under the loss-share coverage do not reach expected levels, the Bank has agreed to make a cash payment to the FDIC on approximately the tenth anniversary of the Agreement.

Leases

Leases	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Leases	NOTE 6 – Leases Lessor Arrangements People's United provides equipment financing to its customers through a variety of lessor arrangements, some of which may include options to renew and/or for the lessee to purchase the leased equipment at the end of the lease term. Direct financing leases and sales-type leases (collectively, "lease financing receivables") are carried at the aggregate of lease payments receivable plus the estimated residual value of the leased assets and any IDC incurred to originate these leases , less unearned income, which is accreted to interest income over the lease term using the interest method. The residual value component of a lease financing receivable represents the estimated fair value of the leased equipment at the end of the lease term. In establishing residual value estimates, the Company may rely on industry data, historical experience, independent appraisals and, where appropriate, information regarding product life cycle, product upgrades and competing products. Upon expiration of a lease, residual assets are remarketed, resulting in an extension of the lease by the lessee, a lease to a new customer or purchase of the residual asset by the lessee or another party. Impairment of residual values arises if the expected fair value is less than the carrying amount. The Company assesses its net investment in lease financing receivables (including residual values) for impairment on a quarterly basis with any impairment losses recognized in accordance with the impairment guidance for financial instruments. As such, net investment in lease financing receivables may be reduced by an allowance for credit losses with changes recognized as provision expense. The composition of the Company’s total net investment in lease financing receivables included within equipment financing loans in the Consolidated Statements of Condition was as follows: (in millions) December 31, 2019 Lease payments receivable $ 1,417.1 Estimated residual value of leased assets 128.0 Gross investment in lease financing receivables 1,545.1 Plus: Deferred origination costs 13.4 Less: Unearned income (156.9) Total net investment in lease financing receivables $ 1,401.6 The contractual maturities of the Company's lease financing receivables were as follows: (in millions) December 31, 2019 2020 $ 518.8 2021 414.2 2022 303.3 2023 178.5 2024 93.6 Later years 36.7 Total $ 1,545.1 Operating lease income, generated in connection with operating leases for which the Company acts as a lessor, is recognized on a straight-line basis over the lease term as a component of non-interest income in the Consolidated Statements of Income. Depreciation expense for assets under operating leases, which are included in other assets in the Consolidated Statements of Condition, is generally recorded on a straight-line basis over the lease term as a component of non-interest expense in the Consolidated Statements of Income. For the year ended December 31, 2019, total lease income was $117.9 million, which consisted of $66.7 million from lease financing receivables and $51.2 million from operating leases. Lessee Arrangements Substantially all of the Company’s lessee arrangements represent non-cancelable operating leases for real estate (primarily branch locations) and office equipment with terms extending through 2054. Under these arrangements, People's United records ROU assets and corresponding lease liabilities at lease commencement. Lease liabilities are recognized based on the present value of the remaining lease payments and discounted using the Company’s incremental borrowing rate for borrowings of similar term. ROU assets initially equal the related lease liability, adjusted for any lease payments made prior to the lease commencement and any lease incentives. Portions of certain properties are subleased for terms extending through 2024. At lease commencement, the Company considers renewal or termination options in the determination of the term of the lease. If it is reasonably certain that a renewal or termination option will be exercised, the effects of such options are included in the determination of the expected lease term. All leases are recorded with the exception of leases with an initial term of twelve months or less for which the Company made the short-term lease election. Within the Consolidated Statements of Condition, ROU assets are reported in other assets and the related lease liabilities are reported in other liabilities. In recognizing ROU assets and related lease liabilities, lease and non-lease components (such as taxes, insurance and common area maintenance costs) are accounted for separately as such amounts are generally readily determinable under the Company's lease contracts. Lease expense is recognized on a straight-line basis over the lease term and is recorded within occupancy and equipment expense in the Consolidated Statements of Income. Variable lease payments, which generally relate to the non-lease components noted above, are expensed as incurred. The following tables provide the components of lease cost and supplemental information: For the Year Ended (in millions) December 31, 2019 Operating lease cost $ 61.6 Variable lease cost 8.6 Finance lease cost 0.1 Sublease income (1.4) Net lease cost $ 68.9 Rent expense under operating leases included in occupancy and equipment in the Consolidated Statements of Income totaled $64.2 million and $62.5 million for the years ended December 31, 2018 and 2017, respectively. (dollars in millions) As of and for the Year Lease ROU assets: Operating lease $ 276.6 Finance lease 2.6 Lease liabilities: Operating lease $ 307.9 Finance lease 5.3 Cash payments included in the measurement of lease liabilities: Reported in operating cash from operating leases 61.7 Reported in financing cash from finance leases 0.1 ROU assets obtained in exchange for lessee: Operating lease liabilities (1) 89.1 Finance lease liabilities (1) 2.6 Weighted-average discount rate: Operating leases 3.13 % Finance leases 2.58 Weighted-average remaining lease term (in years): Operating leases 7.7 Finance leases 12.2 1. Amount excludes related transition adjustment (see Note 1). The contractual maturities of the Company's lease liabilities as of December 31, 2019 were as follows: (in millions) Operating Leases Finance Leases 2020 $ 66.6 $ 0.5 2021 63.9 0.5 2022 46.3 0.5 2023 33.9 0.5 2024 28.3 0.5 Later years 111.8 3.7 Total lease payments 350.8 6.2 Less: Interest (42.9) (0.9) Total lease liabilities $ 307.9 $ 5.3 In the fourth quarter of 2019, the Company completed a sale-leaseback transaction on a property located in Burlington, Vermont. The transaction resulted in a gain of $3.3 million, which is included in other non-interest income in the Consolidated Statements of Income.
Leases	NOTE 6 – Leases Lessor Arrangements People's United provides equipment financing to its customers through a variety of lessor arrangements, some of which may include options to renew and/or for the lessee to purchase the leased equipment at the end of the lease term. Direct financing leases and sales-type leases (collectively, "lease financing receivables") are carried at the aggregate of lease payments receivable plus the estimated residual value of the leased assets and any IDC incurred to originate these leases , less unearned income, which is accreted to interest income over the lease term using the interest method. The residual value component of a lease financing receivable represents the estimated fair value of the leased equipment at the end of the lease term. In establishing residual value estimates, the Company may rely on industry data, historical experience, independent appraisals and, where appropriate, information regarding product life cycle, product upgrades and competing products. Upon expiration of a lease, residual assets are remarketed, resulting in an extension of the lease by the lessee, a lease to a new customer or purchase of the residual asset by the lessee or another party. Impairment of residual values arises if the expected fair value is less than the carrying amount. The Company assesses its net investment in lease financing receivables (including residual values) for impairment on a quarterly basis with any impairment losses recognized in accordance with the impairment guidance for financial instruments. As such, net investment in lease financing receivables may be reduced by an allowance for credit losses with changes recognized as provision expense. The composition of the Company’s total net investment in lease financing receivables included within equipment financing loans in the Consolidated Statements of Condition was as follows: (in millions) December 31, 2019 Lease payments receivable $ 1,417.1 Estimated residual value of leased assets 128.0 Gross investment in lease financing receivables 1,545.1 Plus: Deferred origination costs 13.4 Less: Unearned income (156.9) Total net investment in lease financing receivables $ 1,401.6 The contractual maturities of the Company's lease financing receivables were as follows: (in millions) December 31, 2019 2020 $ 518.8 2021 414.2 2022 303.3 2023 178.5 2024 93.6 Later years 36.7 Total $ 1,545.1 Operating lease income, generated in connection with operating leases for which the Company acts as a lessor, is recognized on a straight-line basis over the lease term as a component of non-interest income in the Consolidated Statements of Income. Depreciation expense for assets under operating leases, which are included in other assets in the Consolidated Statements of Condition, is generally recorded on a straight-line basis over the lease term as a component of non-interest expense in the Consolidated Statements of Income. For the year ended December 31, 2019, total lease income was $117.9 million, which consisted of $66.7 million from lease financing receivables and $51.2 million from operating leases. Lessee Arrangements Substantially all of the Company’s lessee arrangements represent non-cancelable operating leases for real estate (primarily branch locations) and office equipment with terms extending through 2054. Under these arrangements, People's United records ROU assets and corresponding lease liabilities at lease commencement. Lease liabilities are recognized based on the present value of the remaining lease payments and discounted using the Company’s incremental borrowing rate for borrowings of similar term. ROU assets initially equal the related lease liability, adjusted for any lease payments made prior to the lease commencement and any lease incentives. Portions of certain properties are subleased for terms extending through 2024. At lease commencement, the Company considers renewal or termination options in the determination of the term of the lease. If it is reasonably certain that a renewal or termination option will be exercised, the effects of such options are included in the determination of the expected lease term. All leases are recorded with the exception of leases with an initial term of twelve months or less for which the Company made the short-term lease election. Within the Consolidated Statements of Condition, ROU assets are reported in other assets and the related lease liabilities are reported in other liabilities. In recognizing ROU assets and related lease liabilities, lease and non-lease components (such as taxes, insurance and common area maintenance costs) are accounted for separately as such amounts are generally readily determinable under the Company's lease contracts. Lease expense is recognized on a straight-line basis over the lease term and is recorded within occupancy and equipment expense in the Consolidated Statements of Income. Variable lease payments, which generally relate to the non-lease components noted above, are expensed as incurred. The following tables provide the components of lease cost and supplemental information: For the Year Ended (in millions) December 31, 2019 Operating lease cost $ 61.6 Variable lease cost 8.6 Finance lease cost 0.1 Sublease income (1.4) Net lease cost $ 68.9 Rent expense under operating leases included in occupancy and equipment in the Consolidated Statements of Income totaled $64.2 million and $62.5 million for the years ended December 31, 2018 and 2017, respectively. (dollars in millions) As of and for the Year Lease ROU assets: Operating lease $ 276.6 Finance lease 2.6 Lease liabilities: Operating lease $ 307.9 Finance lease 5.3 Cash payments included in the measurement of lease liabilities: Reported in operating cash from operating leases 61.7 Reported in financing cash from finance leases 0.1 ROU assets obtained in exchange for lessee: Operating lease liabilities (1) 89.1 Finance lease liabilities (1) 2.6 Weighted-average discount rate: Operating leases 3.13 % Finance leases 2.58 Weighted-average remaining lease term (in years): Operating leases 7.7 Finance leases 12.2 1. Amount excludes related transition adjustment (see Note 1). The contractual maturities of the Company's lease liabilities as of December 31, 2019 were as follows: (in millions) Operating Leases Finance Leases 2020 $ 66.6 $ 0.5 2021 63.9 0.5 2022 46.3 0.5 2023 33.9 0.5 2024 28.3 0.5 Later years 111.8 3.7 Total lease payments 350.8 6.2 Less: Interest (42.9) (0.9) Total lease liabilities $ 307.9 $ 5.3 In the fourth quarter of 2019, the Company completed a sale-leaseback transaction on a property located in Burlington, Vermont. The transaction resulted in a gain of $3.3 million, which is included in other non-interest income in the Consolidated Statements of Income.
Leases	NOTE 6 – Leases Lessor Arrangements People's United provides equipment financing to its customers through a variety of lessor arrangements, some of which may include options to renew and/or for the lessee to purchase the leased equipment at the end of the lease term. Direct financing leases and sales-type leases (collectively, "lease financing receivables") are carried at the aggregate of lease payments receivable plus the estimated residual value of the leased assets and any IDC incurred to originate these leases , less unearned income, which is accreted to interest income over the lease term using the interest method. The residual value component of a lease financing receivable represents the estimated fair value of the leased equipment at the end of the lease term. In establishing residual value estimates, the Company may rely on industry data, historical experience, independent appraisals and, where appropriate, information regarding product life cycle, product upgrades and competing products. Upon expiration of a lease, residual assets are remarketed, resulting in an extension of the lease by the lessee, a lease to a new customer or purchase of the residual asset by the lessee or another party. Impairment of residual values arises if the expected fair value is less than the carrying amount. The Company assesses its net investment in lease financing receivables (including residual values) for impairment on a quarterly basis with any impairment losses recognized in accordance with the impairment guidance for financial instruments. As such, net investment in lease financing receivables may be reduced by an allowance for credit losses with changes recognized as provision expense. The composition of the Company’s total net investment in lease financing receivables included within equipment financing loans in the Consolidated Statements of Condition was as follows: (in millions) December 31, 2019 Lease payments receivable $ 1,417.1 Estimated residual value of leased assets 128.0 Gross investment in lease financing receivables 1,545.1 Plus: Deferred origination costs 13.4 Less: Unearned income (156.9) Total net investment in lease financing receivables $ 1,401.6 The contractual maturities of the Company's lease financing receivables were as follows: (in millions) December 31, 2019 2020 $ 518.8 2021 414.2 2022 303.3 2023 178.5 2024 93.6 Later years 36.7 Total $ 1,545.1 Operating lease income, generated in connection with operating leases for which the Company acts as a lessor, is recognized on a straight-line basis over the lease term as a component of non-interest income in the Consolidated Statements of Income. Depreciation expense for assets under operating leases, which are included in other assets in the Consolidated Statements of Condition, is generally recorded on a straight-line basis over the lease term as a component of non-interest expense in the Consolidated Statements of Income. For the year ended December 31, 2019, total lease income was $117.9 million, which consisted of $66.7 million from lease financing receivables and $51.2 million from operating leases. Lessee Arrangements Substantially all of the Company’s lessee arrangements represent non-cancelable operating leases for real estate (primarily branch locations) and office equipment with terms extending through 2054. Under these arrangements, People's United records ROU assets and corresponding lease liabilities at lease commencement. Lease liabilities are recognized based on the present value of the remaining lease payments and discounted using the Company’s incremental borrowing rate for borrowings of similar term. ROU assets initially equal the related lease liability, adjusted for any lease payments made prior to the lease commencement and any lease incentives. Portions of certain properties are subleased for terms extending through 2024. At lease commencement, the Company considers renewal or termination options in the determination of the term of the lease. If it is reasonably certain that a renewal or termination option will be exercised, the effects of such options are included in the determination of the expected lease term. All leases are recorded with the exception of leases with an initial term of twelve months or less for which the Company made the short-term lease election. Within the Consolidated Statements of Condition, ROU assets are reported in other assets and the related lease liabilities are reported in other liabilities. In recognizing ROU assets and related lease liabilities, lease and non-lease components (such as taxes, insurance and common area maintenance costs) are accounted for separately as such amounts are generally readily determinable under the Company's lease contracts. Lease expense is recognized on a straight-line basis over the lease term and is recorded within occupancy and equipment expense in the Consolidated Statements of Income. Variable lease payments, which generally relate to the non-lease components noted above, are expensed as incurred. The following tables provide the components of lease cost and supplemental information: For the Year Ended (in millions) December 31, 2019 Operating lease cost $ 61.6 Variable lease cost 8.6 Finance lease cost 0.1 Sublease income (1.4) Net lease cost $ 68.9 Rent expense under operating leases included in occupancy and equipment in the Consolidated Statements of Income totaled $64.2 million and $62.5 million for the years ended December 31, 2018 and 2017, respectively. (dollars in millions) As of and for the Year Lease ROU assets: Operating lease $ 276.6 Finance lease 2.6 Lease liabilities: Operating lease $ 307.9 Finance lease 5.3 Cash payments included in the measurement of lease liabilities: Reported in operating cash from operating leases 61.7 Reported in financing cash from finance leases 0.1 ROU assets obtained in exchange for lessee: Operating lease liabilities (1) 89.1 Finance lease liabilities (1) 2.6 Weighted-average discount rate: Operating leases 3.13 % Finance leases 2.58 Weighted-average remaining lease term (in years): Operating leases 7.7 Finance leases 12.2 1. Amount excludes related transition adjustment (see Note 1). The contractual maturities of the Company's lease liabilities as of December 31, 2019 were as follows: (in millions) Operating Leases Finance Leases 2020 $ 66.6 $ 0.5 2021 63.9 0.5 2022 46.3 0.5 2023 33.9 0.5 2024 28.3 0.5 Later years 111.8 3.7 Total lease payments 350.8 6.2 Less: Interest (42.9) (0.9) Total lease liabilities $ 307.9 $ 5.3 In the fourth quarter of 2019, the Company completed a sale-leaseback transaction on a property located in Burlington, Vermont. The transaction resulted in a gain of $3.3 million, which is included in other non-interest income in the Consolidated Statements of Income.

Goodwill and Other Acquisition-

Goodwill and Other Acquisition-Related Intangible Assets	12 Months Ended
	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Acquisition-Related Intangible Assets	NOTE 7 – Goodwill and Other Acquisition-Related Intangible Assets Goodwill Changes in the carrying amount of People’s United’s goodwill are summarized as follows: Operating Segment (in millions) Commercial Retail Wealth Total Balance at December 31, 2017 $ 1,600.3 $ 720.1 $ 91.0 $ 2,411.4 Acquisition of: First Connecticut 135.2 115.2 — 250.4 Vend Lease 23.9 — — 23.9 Balance at December 31, 2018 1,759.4 835.3 91.0 2,685.7 Acquisition of: United Financial 120.5 83.8 — 204.3 BSB Bancorp 49.3 95.6 — 144.9 VAR 37.5 — — 37.5 Write-down relating to the sale of branches (1) (0.6) (3.8) (2.5) (6.9) Balance at December 31, 2019 $ 1,966.1 $ 1,010.9 $ 88.5 $ 3,065.5 (1) See Note 2. Recent acquisitions have been undertaken with the objective of expanding the Company’s business, both geographically and through product offerings, as well as realizing synergies and economies of scale by combining with the acquired entities. For these reasons, a market-based premium was paid for the acquired entities which, in turn, resulted in the recognition of goodwill, representing the excess of the respective purchase prices over the estimated fair value of the net assets acquired. All of People’s United’s tax deductible goodwill was created in transactions in which the Company purchased the assets of the target (as opposed to purchasing the issued and outstanding stock of the target). At December 31, 2019 and 2018, tax deductible goodwill totaled $134.4 million and $90.3 million, respectively. Other Acquisition-Related Intangible Assets The following is a summary of People’s United’s other acquisition-related intangible assets: 2019 2018 As of December 31 (in millions) Gross Accumulated Carrying Gross Accumulated Carrying Intangibles amortized: Core deposit intangible $ 303.9 $ 177.3 $ 126.6 $ 222.9 $ 157.4 $ 65.5 Trade name intangible 123.9 73.4 50.5 123.9 64.8 59.1 Client relationships 24.4 6.4 18.0 24.4 4.4 20.0 Trust relationships 42.7 35.1 7.6 42.7 31.3 11.4 Insurance relationships 38.1 34.3 3.8 38.1 33.6 4.5 Favorable lease agreements 2.9 0.6 2.3 2.9 0.3 2.6 Non-compete agreements 0.6 0.3 0.3 0.6 0.2 0.4 Total $ 536.5 $ 327.4 209.1 $ 455.5 $ 292.0 163.5 Mutual fund management contracts — 16.5 Total other acquisition-related $ 209.1 $ 180.0 Other acquisition-related intangible assets subject to amortization have an original weighted-average amortization period of 12 years. Amortization expense of other acquisition-related intangible assets totaled $32.5 million, $21.8 million and $30.0 million for the years ended December 31, 2019, 2018 and 2017, respectively. Scheduled amortization expense attributable to other acquisition-related intangible assets for each of the next five years is as follows: $40.9 million in 2020; $36.1 million in 2021; $31.7 million in 2022; $24.0 million in 2023; and $20.3 million in 2024. In the fourth quarter of 2019, People's United recorded a complete write-down of the mutual fund management contract intangible asset ($16.5 million) stemming from the liquidation of the Company's public mutual funds. The charge is included in other non-interest expense in the Consolidated Statements of Income. Also in the fourth quarter of 2019, People's United recorded partial write-downs of the trade name and trust relationship intangible assets ($1.9 million and $1.0 million, respectively) as a result of the sale of eight branches in central Maine. The charge is included in other non-interest income (as a component of the net gain on sale) in the Consolidated Statements of Income. There were no other impairment losses relating to goodwill or other acquisition-related intangible assets recorded in the Consolidated Statements of Income during the years ended December 31, 2019, 2018 and 2017.

Premises and Equipment

Premises and Equipment	12 Months Ended
	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Premises and Equipment	NOTE 8 – Premises and Equipment The components of premises and equipment are summarized below: As of December 31 (in millions) 2019 2018 Land $ 49.8 $ 50.1 Buildings 330.6 300.0 Leasehold improvements 197.4 170.7 Furniture and equipment 324.3 279.3 Total 902.1 800.1 Less: Accumulated depreciation and amortization 596.6 532.8 Total premises and equipment, net $ 305.5 $ 267.3 Depreciation and amortization expense included in occupancy and equipment expense in the Consolidated Statements of Income totaled $41.7 million, $36.3 million and $39.1 million for the years ended December 31, 2019, 2018 and 2017, respectively.

Other Assets and Other Liabilit

Other Assets and Other Liabilities	12 Months Ended
	Dec. 31, 2019
Other Assets And Other Liabilities [Abstract]
Other Assets and Other Liabilities	NOTE 9 – Other Assets and Other Liabilities The components of other assets are as follows: As of December 31 (in millions) 2019 2018 Affordable housing investments (note 13) $ 383.9 $ 304.1 Fair value of derivative financial instruments (notes 20 and 22) 341.0 103.0 Lease ROU assets (note 6) 279.2 — Leased equipment 191.3 189.0 Accrued interest receivable 156.1 138.2 Funded status of defined benefit pension plans (note 18) 121.4 78.0 Loan disbursements in process 65.8 17.9 Current income tax receivable (note 13) 51.7 31.4 Assets held in trust for supplemental retirement plans (note 18) 51.0 56.4 Net deferred tax asset (note 13) 33.6 11.4 Other prepaid expenses 32.6 27.5 Economic development investments 29.2 26.2 Investment in joint venture 16.3 17.2 Receivables arising from securities brokerage and insurance businesses 13.0 26.4 REO: Residential 11.9 5.5 Commercial 7.3 8.7 Mortgage servicing rights 10.6 — Repossessed assets 4.2 3.9 Other 52.9 46.8 Total other assets $ 1,853.0 $ 1,091.6 The components of other liabilities are as follows: As of December 31 (in millions) 2019 2018 Lease liabilities (note 6) $ 313.2 $ — Future contingent commitments for affordable housing investments (note 13) 141.1 119.7 Accrued expenses payable 104.3 87.9 Fair value of derivative financial instruments (notes 20 and 22) 96.2 139.0 Liabilities for supplemental retirement plans (note 18) 84.4 86.6 Accrued employee benefits 74.8 66.6 Accrued interest payable 21.7 25.4 Loan payments in process 18.8 51.2 Other postretirement plans (note 18) 18.7 15.3 Payables arising from securities brokerage and insurance businesses 9.6 29.7 Other 22.7 73.8 Total other liabilities $ 905.5 $ 695.2

Deposits

Deposits	12 Months Ended
	Dec. 31, 2019
Banking and Thrift [Abstract]
Deposits	NOTE 10 – Deposits The following is an analysis of People’s United’s total deposits by product type: 2019 2018 As of December 31 (dollars in millions) Amount Weighted- Amount Weighted- Non-interest-bearing $ 9,803.7 — % $ 8,543.0 — % Savings 4,987.7 0.23 4,116.5 0.09 Interest-bearing checking and money market 19,592.6 0.92 16,583.3 1.04 Time deposits maturing: Within 3 months $ 3,984.7 1.90 1,480.0 1.66 After 3 but within 6 months 2,659.3 2.12 1,375.6 1.67 After 6 months but within 1 year 1,354.8 1.77 2,511.5 1.83 After 1 but within 2 years 816.3 1.82 1,275.5 1.98 After 2 but within 3 years 275.4 2.23 153.5 1.97 After 3 but within 4 years 97.8 2.37 102.1 1.63 After 4 but within 5 years 17.2 1.09 18.0 1.29 After 5 years (1) — 0.99 — 1.01 Total 9,205.5 1.95 6,916.2 1.78 Total deposits $ 43,589.5 0.85 % $ 36,159.0 0.83 % (1) Amount totaled less than $0.1 million at both December 31, 2019 and 2018. Time deposits issued in amounts that exceed $250,000 totaled $1.9 billion and $1.1 billion at December 31, 2019 and 2018, respectively. Overdrafts of non-interest-bearing deposit accounts totaling $4.0 million and $2.7 million at December 31, 2019 and 2018, respectively, have been classified as loans. Interest expense on deposits is summarized as follows: Years ended December 31 (in millions) 2019 2018 2017 Savings $ 13.4 $ 7.2 $ 9.7 Interest-bearing checking and money market 195.9 120.2 70.4 Time 147.6 88.7 50.6 Total $ 356.9 $ 216.1 $ 130.7

Borrowings

Borrowings	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Borrowings	NOTE 11 – Borrowings People’s United’s borrowings are summarized as follows: 2019 2018 As of December 31 (dollars in millions) Amount Weighted- Amount Weighted- Fixed-rate FHLB advances maturing: Within 1 month $ 3,060.8 1.79 % $ 2,270.3 2.59 % After 1 month but within 1 year 44.8 1.79 61.0 1.76 After 1 but within 2 years 6.8 2.11 54.2 1.75 After 2 but within 3 years 1.2 0.51 6.8 2.11 After 3 but within 4 years 0.6 0.05 1.3 0.52 After 4 but within 5 years — — 0.6 0.05 After 5 years 11.2 1.50 10.3 1.64 Total FHLB advances 3,125.4 1.79 2,404.5 2.54 Federal funds purchased maturing: Within 1 month 1,620.0 1.61 845.0 2.53 Total federal funds purchased 1,620.0 1.61 845.0 2.53 Customer repurchase agreements maturing: Within 1 month 409.1 0.69 332.9 0.61 Total customer repurchase agreements 409.1 0.69 332.9 0.61 Other borrowings maturing: Within 1 year — — 11.0 2.40 Total other borrowings — — 11.0 2.40 Total borrowings $ 5,154.5 1.64 % $ 3,593.4 2.36 % At December 31, 2019, the Bank’s total borrowing capacity from (i) the FHLB of Boston and the FRB-NY for advances and (ii) repurchase agreements was $12.7 billion based on the level of qualifying collateral available for these borrowings. In addition, the Bank had unsecured borrowing capacity of $1.7 billion at that date. FHLB advances are secured by the Bank’s investment in FHLB stock and by a security agreement that requires the Bank to maintain, as collateral, sufficient qualifying assets not otherwise pledged (principally single-family residential mortgage loans, home equity lines of credit and loans, and commercial real estate loans). Interest expense on borrowings consists of the following: Years ended December 31 (in millions) 2019 2018 2017 FHLB advances $ 50.1 $ 54.5 $ 31.5 Federal funds purchased 24.6 13.6 7.1 Customer repurchase agreements 2.2 1.0 0.6 Other borrowings 0.1 1.8 2.1 Total $ 77.0 $ 70.9 $ 41.3 Information concerning People’s United’s borrowings is presented below: As of and for the years ended December 31 (dollars in millions) 2019 2018 2017 FHLB advances: Balance at year end $ 3,125.4 $ 2,404.5 $ 2,774.4 Average outstanding during the year 2,098.0 2,653.6 2,677.5 Maximum outstanding at any month end 3,125.5 3,510.1 3,130.8 Average interest rate during the year 2.39 % 2.05 % 1.17 % Federal funds purchased: Balance at year end $ 1,620.0 $ 845.0 $ 820.0 Average outstanding during the year 1,127.5 682.2 643.5 Maximum outstanding at any month end 1,665.0 855.0 820.0 Average interest rate during the year 2.18 % 2.00 % 1.11 % Customer repurchase agreements: Balance at year end $ 409.1 $ 332.9 $ 301.6 Carrying amount of collateral securities at year end 418.0 342.3 307.7 Average outstanding during the year 296.6 252.7 311.0 Maximum outstanding at any month end 409.1 332.9 331.6 Average interest rate during the year 0.75 % 0.40 % 0.19 % Other borrowings: Balance at year end $ — $ 11.0 $ 207.8 Average outstanding during the year 3.3 104.5 132.0 Maximum outstanding at any month end 10.4 207.6 237.4 Average interest rate during the year 1.87 % 1.66 % 1.60 %

Notes and Debentures

Notes and Debentures	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Notes and Debentures	NOTE 12 – Notes and Debentures Notes and debentures are summarized as follows: As of December 31 (in millions) 2019 2018 People’s United Financial, Inc.: 3.65% senior notes due 2022 $ 498.3 $ 497.7 5.75% subordinated notes due 2024 81.6 — People’s United Bank: 4.00% subordinated notes due 2024 413.2 398.1 Total notes and debentures $ 993.1 $ 895.8 The 3.65% senior notes represent fixed-rate unsecured and unsubordinated obligations of People’s United with interest payable semi-annually. The Company may redeem the senior notes at its option, in whole or in part, at any time prior to September 6, 2022, at a redemption price equal to the greater of (i) 100% of the principal amount of the senior notes to be redeemed or (ii) a “make-whole” amount, plus in either case accrued and unpaid interest to the redemption date. In addition, the Company may redeem the senior notes at its option, in whole or in part, at any time on or following September 6, 2022, at a redemption price equal to 100% of the principal amount of the senior notes to be redeemed, plus accrued and unpaid interest to the redemption date. People's United assumed the 5.75% subordinated notes in connection with its acquisition of United Financial. These subordinated notes, which were issued in September 2014, represent fixed-rate unsecured and unsubordinated obligations of People’s United with interest payable semi-annually. People's United may not redeem the subordinated notes prior to maturity without the prior approval of the FRB.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	NOTE 13 – Income Taxes The following is a summary of total income tax expense: Years ended December 31 (in millions) 2019 2018 2017 Income tax expense applicable to pre-tax income $ 132.0 $ 108.2 $ 129.9 Deferred income tax expense (benefit) applicable to items reported in 27.2 (12.2) 8.3 Total $ 159.2 $ 96.0 $ 138.2 The components of income tax expense applicable to pre-tax income are summarized as follows: Years ended December 31 (in millions) 2019 2018 2017 Current tax expense: Federal $ 90.8 $ 83.0 $ 88.9 State 26.9 23.3 15.2 Total current tax expense 117.7 106.3 104.1 Deferred tax expense (1) 14.3 1.9 25.8 Total income tax expense $ 132.0 $ 108.2 $ 129.9 (1) Includes the effect of (decreases) increases in the valuation allowance for state deferred tax assets of $(7.7) million, $0.3 million and $(0.6) million in 2019, 2018 and 2017, respectively. The following is a reconciliation of expected income tax expense, computed at the U.S. federal statutory rate of 21% in both 2019 and 2018, and 35% in 2017, to actual income tax expense: 2019 2018 2017 Years ended December 31 (dollars in millions) Amount Rate Amount Rate Amount Rate Expected income tax expense $ 137.0 21.0 % $ 121.0 21.0 % $ 163.5 35.0 % State income tax, net of federal tax effect 22.6 3.4 23.2 4.1 12.2 2.6 Non-deductible FDIC insurance premiums 4.4 0.7 6.5 1.1 — — Tax-exempt interest (21.4) (3.3) (19.4) (3.4) (26.6) (5.7) Federal income tax credits (12.7) (2.0) (12.3) (2.1) (11.6) (2.5) Tax-exempt income from BOLI (2.2) (0.3) (1.5) (0.3) (2.2) (0.5) Tax benefits recognized in connection with: The Tax Cuts and Jobs Act — — (9.2) (1.6) (6.5) (1.4) Equity-based compensation (0.1) — (1.3) (0.2) (1.1) (0.2) Other, net 4.4 0.7 1.2 0.2 2.2 0.5 Actual income tax expense $ 132.0 $ 108.2 $ 129.9 Effective income tax rate 20.2 % 18.8 % 27.8 % Tax Reform The Tax Cuts and Jobs Act (the "Act") was enacted on December 22, 2017. The most significant provision of the Act applicable to the Company served to reduce the U.S. federal corporate income tax rate, effective January 1, 2018, from 35% to 21%. In connection with its accounting for enactment of the Act, the Company recognized an income tax benefit of $6.5 million during the quarter ended December 31, 2017. This benefit, which served to reduce income tax expense, reflected the revaluation of certain deferred tax assets ($58.0 million) and deferred tax liabilities ($64.5 million) based on the rates at which they are expected to reverse in the future (generally 21%). During the quarter ended December 31, 2018, the Company recognized an income tax benefit of $9.2 million related, primarily, to voluntary employer contributions totaling $50 million made to the Company’s defined benefit pension plans in February 2018 and deducted (as permitted) on the Company’s 2017 federal income tax return (see Note 18). Under GAAP, the effect of a change in tax law is recorded discretely as a component of the income tax provision related to continuing operations in the period of enactment. This is true even if the deferred taxes being revalued were established through a financial statement component other than continuing operations (e.g. accumulated other comprehensive income). Adjusting the deferred taxes for temporary differences that arose from items of income or loss that were originally recorded in accumulated other comprehensive income through continuing operations may result in a disproportionate tax effect lodged in accumulated other comprehensive income. In other words, the original deferred tax amount recorded through accumulated other comprehensive income at the old tax rate will remain in accumulated other comprehensive income despite the fact that its related deferred tax asset/liability will be reduced through continuing operations to reflect the new tax rate. The amounts lodged in accumulated other comprehensive income are often referred to as “stranded tax effects.” In February 2018, as a result of the enactment of the Act, the FASB issued new accounting guidance that provided entities with the option to reclassify, from accumulated other comprehensive income to retained earnings, certain “stranded tax effects” resulting from application of the Act. The guidance became effective for all organizations for fiscal years beginning after December 15, 2018 (January 1, 2019 for People’s United), including interim periods within those fiscal years, and early adoption was permitted. The Company elected to early adopt this amendment effective January 1, 2018 (see Note 1). Affordable Housing Investments People's United holds ownership interests in limited partnerships formed to develop and operate affordable housing units for lower income tenants throughout its franchise area. The underlying partnerships, which are considered VIEs, are not consolidated into the Company's Consolidated Financial Statements. These investments have historically played a role in enabling the Bank to meet its Community Reinvestment Act requirements while, at the same time, providing federal income tax credits. Affordable housing investments, including all legally binding commitments to fund future investments, are included in other assets in the Consolidated Statements of Condition ($383.9 million and $304.1 million at December 31, 2019 and 2018, respectively). Included in other liabilities in the Consolidated Statements of Condition is a liability for all legally binding unfunded commitments to fund future investments ($141.1 million and $119.7 million at those dates). The cost of the Company's investments is amortized on a straight-line basis over the period during which the related federal income tax credits are realized (generally ten years). Amortization expense, which is included as a component of income tax expense in the Consolidated Statements of Income, totaled $25.0 million, $19.1 million and $16.7 million for the years ended December 31, 2019, 2018 and 2017, respectively. D.C. Solar Tax-Advantaged Investments As a result of its acquisition of United Financial, People’s United became a limited liability member in three tax-advantaged funds – Solar Eclipse Investment Fund X, LLC; Solar Eclipse Investment Fund XV, LLC; and Solar Eclipse Investment Fund XXII, LLC (collectively, the “LLCs”) – each of which previously generated solar investment tax credits for United Financial. Solarmore Management Services, Inc. (“Solarmore”) originally served as the managing member for each of the LLCs, and also acted as the managing member of a number of other solar investment tax credit LLC funds (collectively, the “Funds”). In December 2019, Solarmore was replaced as the manager of the LLCs. The LLCs were established to participate in a government-sponsored program to promote solar technology and obtain financing to acquire approximately 500 mobile solar generators and place those generators in service to qualify for a federal tax credit based upon the fair value of the generators. Each Fund (and each LLC) obtained financing from D.C. Solar Solutions, Inc. (“Solutions”), which is also the manufacturer and seller of the generators, and entered into a master lease arrangement with D.C. Solar Distribution, Inc. (“Distribution”), the entity that is responsible for the end sub-lease activity supporting the fair value of the master lease agreement. Solutions and Distribution are indirectly related. In December 2018, Solutions and Distribution (collectively, “D.C. Solar”) had certain assets seized by the U.S. Government. In late January and early February 2019, D.C. Solar and certain affiliated companies filed voluntary petitions for bankruptcy under Chapter 11 of the U.S. Bankruptcy Code in an attempt to reorganize. On March 22, 2019, primarily as a result of a lack of financing to maintain the on-going operations of these companies, ambiguity around actual inventory in existence and the U.S. Government’s seizure of certain assets, the bankruptcy cases were converted to cases under Chapter 7. Prior to conversion of the bankruptcy cases, an FBI affidavit filed in the bankruptcy cases contained allegations of a potential fraud perpetrated by the principals of D.C. Solar, including allegations of fictitious or overstated sales of mobile solar generators sold to the Funds (including the LLCs) as well as the fabrication of sublease revenue streams for the generators. At the time of the Company’s acquisition of United Financial, further developments had occurred which served to increase the level of uncertainty with respect to the existence, condition and fair value of the generators. These factors were considered by the Company and, as a result, it was concluded that there was sufficient evidence to support that a full loss was probable. Accordingly, in connection with the related purchase accounting for United Financial, People’s United recorded a full write-down of the balance of the remaining investments in the LLCs of $8.4 million (after-tax) and established a reserve against tax benefits and credits of $18.9 million to reflect a full loss on the generators and the associated tax benefits previously realized by United Financial. In January 2020, the principals of D.C. Solar plead guilty in federal court to conspiracy to commit wire fraud and money laundering in connection with their role in a Ponzi scheme in which they: (i) sold solar generators that did not exist; (ii) made it appear as though solar generators existed in locations where they did not; (iii) created false financial statements; and (iv) obtained false lease contracts. In connection with the guilty plea, the U.S. Securities and Exchange Commission filed related civil charges against the principals. Connecticut Passive Investment Company In 1998, the Bank formed a passive investment company, People's Mortgage Investment Company ("PMIC"), in accordance with Connecticut tax laws, which permit transfers of mortgage loans to such subsidiaries on or after January 1, 1999. The related earnings of PMIC, and any dividends it pays to the Bank, are not subject to Connecticut income tax. As a result of the exclusion of such earnings and dividends from Connecticut taxable income beginning in 1999, the Bank has established a valuation allowance for the full amount of its Connecticut deferred tax asset attributable to net temporary differences and state net operating loss carryforwards. Connecticut tax net operating loss carryforwards totaled $1.2 billion at December 31, 2019 and expire between 2020 and 2032. The tax effects of temporary differences that give rise to People’s United’s deferred tax assets and liabilities are as follows: As of December 31 (in millions) 2019 2018 Deferred tax assets: State tax net operating loss carryforwards, net of federal tax effect $ 71.8 $ 79.4 Allowance for loan losses and non-accrual interest 65.5 62.3 Acquisition-related deferred tax assets 30.5 13.3 Tax credits and net operating loss carryforwards 24.7 — Equity-based compensation 18.1 15.6 ROU lease assets, net of lease liabilities 7.5 — D.C. Solar investment basis difference 6.8 — Unrealized loss on debt securities transferred to held-to-maturity 3.6 4.7 Unrealized loss on debt securities available-for-sale — 15.4 Other deductible temporary differences 28.2 28.5 Total deferred tax assets 256.7 219.2 Less: valuation allowance for state deferred tax assets (72.4) (80.1) Total deferred tax assets, net of the valuation allowance 184.3 139.1 Deferred tax liabilities: Leasing activities (92.7) (82.0) Pension and other postretirement benefits (20.0) (9.7) Book over tax income recognized on consumer loans (18.0) (17.5) Unrealized gain on debt securities available-for-sale (6.6) — Mark-to-market and original issue discounts for tax purposes (5.2) (10.4) Temporary differences related to merchant services joint venture (3.5) (3.7) Other taxable temporary differences (4.7) (4.4) Total deferred tax liabilities (150.7) (127.7) Net deferred tax asset $ 33.6 $ 11.4 Based on People's United’s recent historical and anticipated future pre-tax earnings and the reversal of taxable temporary differences, management believes it is more likely than not that People's United will realize its total deferred tax assets, net of the valuation allowance. People's United’s current income tax receivable at December 31, 2019 and 2018 totaled $51.7 million and $31.4 million, respectively. The following is a reconciliation of the beginning and ending balances of People's United’s unrecognized income tax benefits related to uncertain tax positions: Years ended December 31 (in millions) 2019 2018 2017 Balance at beginning of year $ 5.2 $ 2.7 $ 2.8 Additions for tax positions taken in prior years 0.5 2.5 0.1 Additions related to D.C. Solar: Established by United Financial prior to acquisition 8.7 — — Established by People's United subsequent to acquisition 18.9 — — Reductions attributable to audit settlements/lapse of statute of limitations — — (0.2) Balance at end of year $ 33.3 $ 5.2 $ 2.7

Stockholders' Equity and Divide

Stockholders' Equity and Dividends	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Stockholders' Equity and Dividends	NOTE 14 – Stockholders’ Equity and Dividends People’s United is authorized to issue (i) 50.0 million shares of preferred stock, par value of $0.01 per share, of which 10.0 million shares were outstanding at December 31, 2019, and (ii) 1.95 billion shares of common stock, par value of $0.01 per share, of which 532.8 million shares were issued at December 31, 2019. Treasury stock includes (i) common stock repurchased by People’s United, either directly or through agents, in the open market at prices and terms satisfactory to management in connection with stock repurchases authorized by its Board of Directors (86.6 million shares at December 31, 2019) and (ii) common stock purchased in the open market by a trustee with funds provided by People’s United and originally intended for awards under the People’s United Financial, Inc. 2007 Recognition and Retention Plan (the “RRP”) (2.6 million shares at December 31, 2019). Following shareholder approval of the People’s United Financial, Inc. 2014 Long-Term Incentive Plan (the “2014 Plan”) in 2014, no new awards may be granted under the RRP (see Note 19). In June 2019, the Company’s Board of Directors authorized the repurchase of up to 20.0 million shares of People’s United’s outstanding common stock. Such shares may be repurchased, either directly or through agents, in the open market at prices and terms satisfactory to management. During 2019, the Company repurchased 0.2 million shares of People's United common stock under this authorization at a total cost of $2.5 million. In April 2007, People’s United established an Employee Stock Ownership Plan (the “ESOP”) (see Note 17). At that time, People’s United loaned the ESOP $216.8 million to purchase 10.5 million shares of People’s United common stock in the open market. Shares of People’s United common stock are held by the ESOP and allocated to eligible participants annually based upon a percentage of each participant’s eligible compensation. At December 31, 2019, 5.9 million shares of People’s United common stock, with a contra-equity balance of $122.9 million, have not been allocated or committed to be released. Common dividends declared and paid per common share totaled $0.7075, $0.6975 and $0.6875 for the years ended December 31, 2019, 2018 and 2017, respectively. People’s United’s common dividend payout ratio (common dividends paid as a percentage of net income available to common shareholders) was 54.3%, 53.7% and 70.6% for the years ended December 31, 2019, 2018 and 2017, respectively. In the ordinary course of business, People’s United (parent company) is dependent upon dividends from the Bank to provide funds for the payment of dividends to shareholders and other general corporate purposes. People’s United’s ability to pay cash dividends is governed by federal law, regulations and related guidance. The Bank’s ability to pay cash dividends directly or indirectly to People’s United also is governed by federal law and regulations. These provide that the Bank must receive OCC approval to declare a dividend if the total amount of all dividends (common and preferred), including the proposed dividend, declared by the Bank in any current year exceeds the total of the Bank’s net income for the current year to date, combined with its retained net income for the previous two years, less the sum of any transfers required by the OCC and any transfers required to be made to a fund for the retirement of any preferred stock. The term “retained net income” as defined by federal regulations means the Bank’s net income for a specified period less the total amount of all dividends declared in that period. The Bank may not pay dividends to People’s United if, after paying those dividends, it would fail to meet the required minimum levels under risk-based capital guidelines or if the OCC has notified the Bank that it is in need of more than normal supervision. See Note 15 for a discussion of regulatory capital requirements. Under the Federal Deposit Insurance Act, an insured depository institution such as the Bank is prohibited from making capital distributions, including the payment of dividends, if, after making such distribution, the institution would become “undercapitalized” (as such term is used in the Federal Deposit Insurance Act). Payment of dividends by the Bank also may be restricted at any time at the discretion of the appropriate regulator if it deems the payment to constitute an unsafe and unsound banking practice.

Regulatory Capital Requirements

Regulatory Capital Requirements	12 Months Ended
	Dec. 31, 2019
Banking and Thrift [Abstract]
Regulatory Capital Requirements	NOTE 15 – Regulatory Capital Requirements Bank holding companies and banks are subject to various regulations regarding capital requirements administered by U.S. banking agencies. The FRB (in the case of a bank holding company) and the OCC (in the case of a bank) may initiate certain actions if a bank holding company or a bank fails to meet minimum capital requirements. In addition, under its prompt corrective action regulations, the OCC is required to take certain supervisory actions (and may take additional discretionary actions) with respect to an undercapitalized bank. These actions could have a direct material effect on a bank’s financial statements. People’s United and the Bank are subject to regulatory capital requirements administered by the FRB and the OCC, respectively. Both People's United and the Bank are subject to capital rules (the “Basel III capital rules”) issued by U.S. banking agencies. The Basel III capital rules, which are now fully phased-in, require U.S. financial institutions to maintain: (i) a minimum ratio of “Common Equity Tier 1” (“CET 1”) 1 capital to total risk-weighted assets of at least 4.5%, plus a 2.5% “capital conservation buffer” (which is added to the 4.5% CET 1 risk-based capital ratio as that buffer is phased-in beginning in 2016, effectively resulting in a minimum CET 1 risk-based capital ratio of 7.0% upon full implementation); (ii) a minimum ratio of Tier 1 capital to total risk-weighted assets of at least 6.0%, plus the capital conservation buffer (which is added to the 6.0% Tier 1 risk-based capital ratio as that buffer is phased-in beginning in 2016, effectively resulting in a minimum Tier 1 risk-based capital ratio of 8.5% upon full implementation); (iii) a minimum ratio of Total (that is, Tier 1 plus Tier 2) capital to total risk-weighted assets of at least 8.0%, plus the capital conservation buffer (which is added to the 8.0% Total risk-based capital ratio as that buffer is phased-in beginning in 2016, effectively resulting in a minimum Total risk-based capital ratio of 10.5% upon full implementation); and (iv) a minimum Tier 1 Leverage capital ratio of at least 4.0%, calculated as the ratio of Tier 1 capital to average total assets, as defined. In order to avoid limitations on distributions, including dividend payments, and certain discretionary bonus payments, a financial institution must hold a capital conservation buffer above its minimum risk-based capital requirements. For 2019, the final year of the phase-in period, and thereafter, the capital conservation buffer was to 2.50%. For 2018, the capital conservation buffer was 1.875%. In July 2019, U.S. banking agencies issued a final rule intended to simplify certain aspects of the regulatory capital rules. Management does not expect the impact of this final rule will have a material effect on the Company's or the Bank's risk-based capital ratios. For regulatory capital purposes, subordinated note issuances qualify, up to certain limits, as Tier 2 capital for Total risk-based capital. In accordance with regulatory capital rules, beginning in 2019 and for each of the next four years, the eligible amount of the Bank's $400 million subordinated notes due 2024 and People's United's $75 million subordinated notes due 2024 included in Tier 2 capital will be reduced each year by 20%, or $80 million and $15 million, respectively. The foregoing capital ratios are based in part on specific quantitative measures of assets, liabilities and certain off-balance-sheet items as calculated under regulatory accounting guidelines. Capital amounts and classifications are also subject to qualitative judgments by federal regulators about capital components, risk weightings and other factors. Management believes that, as of December 31, 2019, both People's United and the Bank met all capital adequacy requirements to which each is subject. Further, the most recent regulatory notification categorized the Bank as a well-capitalized institution under the prompt corrective action regulations. Since that notification, no conditions or events have occurred that have caused management to believe any change in the Bank's capital classification would be warranted. As discussed in Note 1 to the Consolidated Financial Statements, People's United adopted, effective January 1, 2019, new accounting guidance relating to leases. Upon adoption, the Company recorded (i) operating lease liabilities totaling $268.8 million and (ii) corresponding ROU assets totaling $248.5 million. This transition adjustment served to increase risk-weighted assets, resulting in an approximate 5 to 10 basis point decrease in the risk-based capital ratios of both the Company and the Bank at that time. As also discussed in Note 1, the Company's adoption of a new accounting standard related to credit losses on financial instruments, effective January 1, 2020, will result in an approximate 10 basis point decrease in the capital ratios at both People's United and the Bank. People's United has elected to phase-in, over three years, the day-one regulatory capital effects of the credit losses standard in accordance with Federal banking agencies final rule issued in December 2018. The following is a summary of People's United’s and the Bank's regulatory capital amounts and ratios under the Basel III capital rules. The minimum capital required amounts as of December 31, 2019 and 2018 are based on the capital conservation buffer phase-in provisions (as applicable for each year) of the Basel III capital rules. In connection with the adoption of the Basel III capital rules, both the Company and the Bank elected to opt-out of the requirement to include most components of AOCL in CET 1 capital. At December 31, 2019, both People's United's and the Bank's total risk-weighted assets, as defined, were $45.2 billion, compared to $35.9 billion for both at December 31, 2018. As of December 31, 2019 Minimum Capital Classification as (dollars in millions) Amount Ratio Amount Ratio Amount Ratio Tier 1 Leverage Capital (1): People’s United $ 4,846.1 9.1 % $ 2,119.7 4.0 % N/A N/A Bank 4,902.0 9.3 2,119.1 4.0 $ 2,648.8 5.0 % CET 1 Risk-Based Capital (2): People’s United 4,602.1 10.2 3,164.5 7.0 N/A N/A Bank 4,902.0 10.9 3,162.2 7.0 2,936.3 6.5 Tier 1 Risk-Based Capital (3): People’s United 4,846.1 10.7 3,842.6 8.5 2,712.5 6.0 Bank 4,902.0 10.9 3,839.8 8.5 3,614.0 8.0 Total Risk-Based Capital (4): People’s United 5,435.6 12.0 4,746.8 10.5 4,520.8 10.0 Bank 5,474.2 12.1 4,743.3 10.5 4,517.4 10.0 As of December 31, 2018 Minimum Capital Classification as (dollars in millions) Amount Ratio Amount Ratio Amount Ratio Tier 1 Leverage Capital (1): People’s United $ 3,927.2 8.7 % $ 1,806.0 4.0 % N/A N/A Bank 4,076.0 9.0 1,805.4 4.0 $ 2,256.8 5.0 % CET 1 Risk-Based Capital (2): People’s United 3,683.1 10.3 2,289.3 6.375 N/A N/A Bank 4,076.0 11.4 2,287.1 6.375 2,331.9 6.5 Tier 1 Risk-Based Capital (3): People’s United 3,927.2 10.9 2,827.9 7.875 2,154.6 6.0 Bank 4,076.0 11.4 2,825.2 7.875 2,870.0 8.0 Total Risk-Based Capital (4): People’s United 4,505.7 12.5 3,546.1 9.875 3,591.0 10.0 Bank 4,719.1 13.2 3,542.7 9.875 3,587.5 10.0 (1) Tier 1 Leverage Capital ratio represents CET 1 Capital plus Additional Tier 1 Capital instruments (together, "Tier 1 Capital") divided by Average Total Assets (less goodwill, other acquisition-related intangibles and other deductions from CET 1 Capital). (2) CET 1 Risk-Based Capital ratio represents equity capital, as defined, less: (i) after-tax net unrealized gains (losses) on certain securities classified as available-for-sale; (ii) after-tax net unrealized gains (losses) on securities transferred to held-to-maturity; (iii) goodwill and other acquisition-related intangible assets; and (iv) the amount recorded in AOCL relating to pension and other postretirement benefits divided by Total Risk-Weighted Assets. (3) Tier 1 Risk-Based Capital ratio represents Tier 1 Capital divided by Total Risk-Weighted Assets. (4) Total Risk-Based Capital ratio represents Tier 1 Capital plus subordinated notes and debentures, up to certain limits, and the allowance for loan losses, up to 1.25% of Total Risk-Weighted Assets, divided by Total Risk-Weighted Assets.

Earnings Per Common Share

Earnings Per Common Share	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Earnings Per Common Share	NOTE 16 – Earnings Per Common Share The following is an analysis of People’s United’s basic and diluted EPS, reflecting the application of the two-class method, as described in Note 1: Years ended December 31 (in millions, except per common share data) 2019 2018 2017 Net income available to common shareholders $ 506.3 $ 454.0 $ 323.1 Dividends paid on and undistributed earnings allocated to participating securities (0.2) (0.2) (0.5) Earnings attributable to common shareholders $ 506.1 $ 453.8 $ 322.6 Weighted average common shares outstanding for basic EPS 394.0 348.1 330.3 Effect of dilutive equity-based awards 3.2 3.6 2.6 Weighted average common shares and common-equivalent shares for diluted EPS 397.2 351.7 332.9 EPS: Basic $ 1.28 $ 1.30 $ 0.98 Diluted 1.27 1.29 0.97 All unallocated ESOP common shares and all common shares accounted for as treasury shares have been excluded from the calculation of basic and diluted EPS. Anti-dilutive equity-based awards totaling 6.7 million shares, 6.8 million shares and 8.9 million shares for the years ended December 31, 2019, 2018 and 2017, respectively, have also been excluded from the calculation of diluted EPS.

Comprehensive Income

Comprehensive Income	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Comprehensive Income	NOTE 17 – Comprehensive Income Comprehensive income represents the sum of net income and items of “other comprehensive income or loss,” including (on an after-tax basis): (i) net actuarial gains and losses, prior service credits and costs, and transition assets and obligations related to People’s United’s pension and other postretirement plans; (ii) net unrealized gains and losses on debt securities available-for-sale; (iii) net unrealized gains and losses on debt securities transferred to held-to-maturity; and (iv) net unrealized gains and losses on derivatives accounted for as cash flow hedges. People’s United’s total comprehensive income for the years ended December 31, 2019, 2018 and 2017 is reported in the Consolidated Statements of Comprehensive Income. The following is a summary of the changes in the components of AOCL, which are included in People’s United’s stockholders’ equity on an after-tax basis: (in millions) Pension Net Unrealized Net Unrealized Net Unrealized Total Balance at December 31, 2016 $ (145.6) $ (32.3) $ (17.4) $ 0.3 $ (195.0) Other comprehensive income (loss) (2.8) (5.3) — (0.6) (8.7) Amounts reclassified from AOCL (1) 4.3 16.0 2.3 (0.6) 22.0 Current period other comprehensive 1.5 10.7 2.3 (1.2) 13.3 Balance at December 31, 2017 (144.1) (21.6) (15.1) (0.9) (181.7) Other comprehensive income (loss) (24.7) (29.0) — (1.3) (55.0) Amounts reclassified from AOCL (1) 6.3 7.5 3.0 0.4 17.2 Current period other comprehensive (18.4) (21.5) 3.0 (0.9) (37.8) Transition adjustments related to adoption (30.0) (3.9) (3.2) (0.2) (37.3) Balance at December 31, 2018 (192.5) (47.0) (15.3) (2.0) (256.8) Other comprehensive income (loss) 9.7 67.9 — 1.5 79.1 Amounts reclassified from AOCL (1) 6.6 (0.1) 3.5 0.8 10.8 Current period other comprehensive 16.3 67.8 3.5 2.3 89.9 Balance at December 31, 2019 $ (176.2) $ 20.8 $ (11.8) $ 0.3 $ (166.9) (1) See the following table for details about these reclassifications. (2) See Notes 1 and 4. The following is a summary of the amounts reclassified from AOCL: Years ended December 31 (in millions) Amounts Reclassified Affected Line Item 2019 2018 2017 Details about components of AOCL: Amortization of pension and Net actuarial loss $ (8.3) $ (8.6) $ (9.3) (1) Prior service credit — 0.3 0.8 (1) (8.3) (8.3) (8.5) Income before income tax expense 1.7 2.0 4.2 Income tax expense (6.6) (6.3) (4.3) Net income Reclassification adjustment for net 0.1 (9.9) (25.4) Income before income tax expense (2) — 2.4 9.4 Income tax expense 0.1 (7.5) (16.0) Net income Amortization of unrealized losses on (4.6) (3.9) (3.7) Income before income tax expense (3) 1.1 0.9 1.4 Income tax expense (3.5) (3.0) (2.3) Net income Amortization of unrealized gains and Interest rate swaps (1.2) (0.6) 0.8 (4) Interest rate locks 0.1 0.1 0.1 (4) (1.1) (0.5) 0.9 Income before income tax expense 0.3 0.1 (0.3) Income tax expense (0.8) (0.4) 0.6 Net income Total reclassifications for the period $ (10.8) $ (17.2) $ (22.0) (1) Included in the computation of net periodic benefit income (expense) reflected in other non-interest expense (see Note 17 for additional details). (2) Included in non-interest income. (3) Included in interest and dividend income — securities. (4) Included in interest expense — notes and debentures. Deferred income taxes applicable to the components of AOCL are as follows: As of December 31 (in millions) 2019 2018 2017 Net actuarial loss and other amounts related to pension and $ 55.3 $ 59.4 $ 83.5 Net unrealized (gain) loss on debt securities available-for-sale (6.6) 14.7 12.7 Net unrealized loss on debt securities transferred to held-to-maturity 3.6 4.7 8.8 Net unrealized (gain) loss on derivatives accounted for as cash flow hedges (0.1) 0.6 0.5 Total deferred income taxes $ 52.2 $ 79.4 $ 105.5 The following is a summary of the components of People’s United’s total other comprehensive income (loss): Year ended December 31, 2019 (in millions) Pre-Tax Tax Effect After-Tax Net actuarial gains and losses on pension and other postretirement plans: Net actuarial gain arising during the year $ 12.1 $ (2.4) $ 9.7 Reclassification adjustment for net actuarial loss included in net income 8.3 (1.7) 6.6 Net actuarial gain 20.4 (4.1) 16.3 Net unrealized gains and losses on debt securities available-for-sale: Net unrealized holding gains arising during the year 89.2 (21.3) 67.9 Reclassification adjustment for net realized losses included in net income (0.1) — (0.1) Net unrealized gains 89.1 (21.3) 67.8 Net unrealized gains and losses on debt securities transferred to held-to-maturity: Reclassification adjustment for amortization of unrealized losses on debt securities transferred to held-to-maturity included in net income 4.6 (1.1) 3.5 Net unrealized gains 4.6 (1.1) 3.5 Net unrealized gains and losses on derivatives accounted for as cash flow hedges: Net unrealized gains arising during the year 1.9 (0.4) 1.5 Reclassification adjustment for net realized losses included in net income 1.1 (0.3) 0.8 Net unrealized gains 3.0 (0.7) 2.3 Total other comprehensive income $ 117.1 $ (27.2) $ 89.9 Year ended December 31, 2018 (in millions) Pre-Tax Tax Effect After-Tax Net actuarial gains and losses on pension and other postretirement plans: Net actuarial loss arising during the year $ (32.6) $ 7.9 $ (24.7) Reclassification adjustment for net actuarial loss included in net income 8.6 (2.1) 6.5 Net actuarial loss (24.0) 5.8 (18.2) Prior service credit on pension and other postretirement plans: Reclassification adjustment for prior service credit included in net income (0.3) 0.1 (0.2) Net actuarial loss and prior service credit (24.3) 5.9 (18.4) Net unrealized gains and losses on debt securities available-for-sale: Net unrealized holding losses arising during the year (38.3) 9.3 (29.0) Reclassification adjustment for net realized losses included in net income 9.9 (2.4) 7.5 Net unrealized losses (28.4) 6.9 (21.5) Net unrealized gains and losses on debt securities transferred to held-to-maturity: Reclassification adjustment for amortization of unrealized losses on debt securities transferred to held-to-maturity included in net income 3.9 (0.9) 3.0 Net unrealized gains 3.9 (0.9) 3.0 Net unrealized gains and losses on derivatives accounted for as cash flow hedges: Net unrealized losses arising during the year (1.7) 0.4 (1.3) Reclassification adjustment for net realized losses included in net income 0.5 (0.1) 0.4 Net unrealized losses (1.2) 0.3 (0.9) Total other comprehensive loss $ (50.0) $ 12.2 $ (37.8) Year ended December 31, 2017 (in millions) Pre-Tax Tax Effect After-Tax Net actuarial gains and losses on pension and other postretirement plans: Net actuarial loss arising during the year $ (5.5) $ 2.7 $ (2.8) Reclassification adjustment for net actuarial loss included in net income 9.3 (4.6) 4.7 Net actuarial gain 3.8 (1.9) 1.9 Prior service credit on pension and other postretirement plans: Reclassification adjustment for prior service credit included in net income (0.8) 0.4 (0.4) Net actuarial gain and prior service credit 3.0 (1.5) 1.5 Net unrealized gains and losses on debt securities available-for-sale: Net unrealized holding losses arising during the year (8.6) 3.3 (5.3) Reclassification adjustment for net realized losses included in net income 25.4 (9.4) 16.0 Net unrealized gains 16.8 (6.1) 10.7 Net unrealized gains and losses on debt securities transferred to held-to-maturity: Reclassification adjustment for amortization of unrealized losses on debt securities transferred to held-to-maturity included in net income 3.7 (1.4) 2.3 Net unrealized gains 3.7 (1.4) 2.3 Net unrealized gains and losses on derivatives accounted for as cash flow hedges: Net unrealized losses arising during the year (1.0) 0.4 (0.6) Reclassification adjustment for net realized gains included in net income (0.9) 0.3 (0.6) Net unrealized losses (1.9) 0.7 (1.2) Total other comprehensive income $ 21.6 $ (8.3) $ 13.3

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2019
Retirement Benefits [Abstract]
Employee Benefit Plans	NOTE 18 – Employee Benefit Plans People’s United Employee Pension and Other Postretirement Plans People’s United maintains a qualified noncontributory defined benefit pension plan (the “People’s Qualified Plan”) that covers substantially all full-time and part-time employees who (i) meet certain age and length of service requirements and (ii) were employed by the Bank prior to August 14, 2006. Benefits are based upon the employee’s years of credited service and either the average compensation for the last five years or the average compensation for the five New employees of the Bank starting on or after August 14, 2006 are not eligible to participate in the People’s Qualified Plan. Instead, the Bank makes contributions on behalf of these employees to a qualified defined contribution plan in an annual amount equal to 3% of the employee’s eligible compensation. Employee participation in this plan is restricted to employees who (i) are at least 18 years of age and (ii) worked at least 1000 hours in a year. Both full-time and part-time employees are eligible to participate as long as they meet these requirements. In July 2011, the Bank amended the People’s Qualified Plan to “freeze”, effective December 31, 2011, the accrual of pension benefits for People’s Qualified Plan participants. As such, participants will not earn any additional benefits after that date. Instead, effective January 1, 2012, the Bank began making contributions on behalf of these participants to a qualified defined contribution plan in an annual amount equal to 3% of the employee’s eligible compensation. In addition to the People’s Qualified Plan, People’s United continues to maintain qualified defined benefit pension plans that cover (i) former First Connecticut employees who meet certain eligibility requirements (the “First Connecticut Qualified Plan”) and (ii) former United Financial employees who meet certain eligibility requirements (the “United Financial Qualified Plan”). All benefits under these plans were frozen effective February 28, 2013 and December 31, 2012, respectively. Effective October 1, 2018, both the Chittenden Qualified Plan and the Suffolk Qualified Plan were merged into the People’s Qualified Plan. People’s United also maintains (i) unfunded, nonqualified supplemental plans to provide retirement benefits to certain senior officers (the “People’s Supplemental Plans”) and (ii) an unfunded plan that provides retirees with optional medical, dental and life insurance benefits (the “People’s Postretirement Plan”). People’s United accrues the cost of these postretirement benefits over the employees’ years of service to the date of their eligibility for such benefit. People’s United also continues to maintain: (1) for certain eligible former First Connecticut employees (i) an unfunded, nonqualified supplemental retirement plan (the “First Connecticut Supplemental Plan”) and (ii) unfunded plans that provide medical, dental and life insurance benefits (the “First Connecticut Postretirement Plans”); (2) for certain eligible former BSB Bancorp employees (i) an unfunded, nonqualified supplemental retirement plan (the “BSB Bancorp Supplemental Plan”) and (ii) unfunded plans that provide life insurance benefits (the “BSB Bancorp Post Retirement Welfare (Life Insurance) Plan”); and (3) for certain former United Financial employees (i) an unfunded, nonqualified supplemental retirement plan (the “United Financial Supplemental Plan”) and (ii) unfunded plans that provide medical, dental and life insurance benefits (the “United Financial Postretirement Benefit Plan”). An employer is required to recognize an asset or a liability for the funded status of pension and other postretirement plans. The funded status is measured as the difference between the fair value of plan assets and the applicable benefit obligation, which is the projected benefit obligation for a pension plan and the accumulated postretirement benefit obligation for another postretirement plan. Plan assets and benefit obligations are required to be measured as of the date of the employer’s fiscal year-end. The following table summarizes changes in the benefit obligations and plan assets of (i) the People’s Qualified Plan (including the Chittenden Qualified Plan and the Suffolk Qualified Plan), the First Connecticut Qualified Plan, the People's Supplemental Plans, the First Connecticut Supplemental Plan, the BSB Bancorp Supplemental Plan and the United Financial Supplemental Plan (together the “Pension Plans”) and (ii) the People’s Postretirement Plan, the First Connecticut Postretirement Plans, the BSB Bancorp Post Retirement Welfare (Life Insurance) Plan and the United Financial Postretirement Plan (together the “Other Postretirement Plans”). The table also shows the funded status (or the difference between benefit obligations and plan assets) recognized in the Consolidated Statements of Condition. All plans have a December 31 measurement date. Pension Plans Other (in millions) 2019 2018 2019 2018 Benefit obligations: (1) Beginning of year $ 562.7 $ 584.8 $ 15.3 $ 14.6 Service cost — — 0.3 0.3 Interest cost 22.9 20.2 0.6 0.5 Actuarial loss (gain) 80.2 (51.0) 1.2 (1.7) Benefits paid (28.2) (21.4) (0.7) (0.8) Settlements (13.1) (2.7) — — Acquisitions (2) 41.0 35.2 2.0 2.4 Plan revaluations (3) — (2.4) — — End of year 665.5 562.7 18.7 15.3 Fair value of plan assets: Beginning of year 596.4 584.9 — — Actual return on assets 138.6 (40.9) — — Employer contributions 18.7 52.7 0.7 0.8 Benefits paid (28.2) (21.4) (0.7) (0.8) Settlements (13.1) (2.7) — — Acquisitions (2) 34.3 23.8 — — End of year 746.7 596.4 — — Funded status at end of year $ 81.2 $ 33.7 $ (18.7) $ (15.3) Amounts recognized in the Consolidated Statements Other assets $ 121.4 $ 78.0 $ — $ — Other liabilities (40.2) (44.3) (18.7) (15.3) Funded status at end of year $ 81.2 $ 33.7 $ (18.7) $ (15.3) (1) Represents the projected benefit obligation for the Pension Plans and the accumulated benefit obligation for the Other Postretirement Plans. (2) Represents the benefit obligations and plan assets of the United Financial Qualified Plan and the United Financial Supplemental Plan as of November 1, 2019, the BSB Bancorp Supplemental Plan as of April 1, 2019, the First Connecticut Qualified Plan as of October 1, 2018, and the benefit obligations of the United Financial Postretirement Plan as of November 1, 2019, the BSB Bancorp Post Retirement Welfare (Life Insurance) Plan as of April 1, 2019 and the First Connecticut Postretirement Plans as of October 1, 2018 (3) Represents the revaluations of the Chittenden Qualified Plan and the Suffolk Qualified Plan, effective October 1, 2018, upon merging into the People’s Qualified Plan. Plan assets for the People’s Qualified Plan, the United Financial Qualified Plan and the First Connecticut Qualified Plan (together the “Qualified Plans”) were $687.8 million, $34.0 million and $24.9 million, respectively, as of December 31, 2019. The related projected benefit obligation of each plan was $569.1 million, $31.9 million and $24.3 million, respectively, at the same date. Although the People’s Supplemental Plans and the First Connecticut Supplemental Plan (together the “Supplemental Plans”) hold no assets, People’s United has funded trusts to provide benefit payments to the extent such benefits are not paid directly by People’s United. Trust assets of $33.1 million as of December 31, 2019 (which are included in other assets in the Consolidated Statements of Condition) were exceeded by the related projected benefit obligation of $40.2 million at that date. The following table summarizes the accumulated and projected benefit obligations for the Pension Plans at the respective measurement dates: Pension Plans As of December 31 (in millions) 2019 2018 Accumulated benefit obligations: Qualified Plans $ 625.3 $ 518.7 Supplemental Plans 40.0 43.6 Total $ 665.3 $ 562.3 Projected benefit obligations: Qualified Plans $ 625.3 $ 518.7 Supplemental Plans 40.2 44.0 Total $ 665.5 $ 562.7 Components of net periodic benefit (income) expense and other amounts recognized in other comprehensive income (loss) are as follows: Pension Plans Other Years ended December 31 (in millions) 2019 2018 2017 2019 2018 2017 Net periodic benefit (income) expense: Interest cost $ 22.9 $ 20.2 $ 19.1 $ 0.9 $ 0.8 $ 0.8 Expected return on plan assets (46.1) (44.3) (37.9) — — — Recognized net actuarial loss 5.3 7.3 6.5 0.1 0.3 0.2 Recognized prior service credit — (0.3) (0.8) — — — Settlements (1) 2.9 1.0 2.6 — — — Net periodic benefit (income) expense (15.0) (16.1) (10.5) 1.0 1.1 1.0 Other changes in plan assets and benefit obligations recognized in other comprehensive income (loss): Net actuarial (gain) loss (20.5) 26.0 (4.8) 1.1 (2.0) 1.0 Prior service credit — 0.3 0.8 — — — Total pre-tax changes recognized in other comprehensive income (loss) (20.5) 26.3 (4.0) 1.1 (2.0) 1.0 Total recognized in net periodic benefit (income) expense and other comprehensive income (loss) $ (35.5) $ 10.2 $ (14.5) $ 2.1 $ (0.9) $ 2.0 (1) Settlement charges are a result of lump-sum benefit payments in excess of the sum of a plan’s annual interest and service costs. When an employer settles the full amount of its obligation for vested benefits with respect to some of a plan’s participants, the employer is required to recognize in income a pro-rata portion of the aggregate gain or loss recorded in AOCL. The pre-tax amounts in AOCL that have not been recognized as components of net periodic benefit (income) expense are as follows: Pension Plans Other As of December 31 (in millions) 2019 2018 2019 2018 Net actuarial loss $ 228.5 $ 249.0 $ 3.9 $ 2.8 Total pre-tax amounts included in AOCL $ 228.5 $ 249.0 $ 3.9 $ 2.8 The Company uses a corridor approach in the valuation of its Qualified Plans, which results in the deferral of actuarial gains and losses resulting from differences between actual results and actuarial assumptions. Amortization of actuarial gains and losses occurs when the accumulated unrecognized gain or loss balance, as of the beginning of the year, exceeds 10% of the greater of the projected benefit obligation or the market-related value of plan assets. The excess unrecognized gain or loss balance is amortized over the average remaining life expectancy of plan participants for the People’s Qualified Plan (approximately 26 years) and over the average working lifetime of active participants for both the First Connecticut Qualified Plan (approximately 28 years) and the United Financial Qualified Plan (approximately 30 years) as of December 31, 2019. The following assumptions were used in determining the benefit obligations and net periodic benefit (income) expense as of and for the periods indicated: Qualified Plans Other Postretirement Plans 2019 2018 2017 2019 2018 2017 Weighted-average assumptions used to determine Discount rate: People’s Qualified Plan 3.38 % 4.41 % 3.74 % 3.40 % 4.40 % 3.70 % First Connecticut Qualified Plan 3.39 4.41 n/a n/a n/a n/a United Financial Qualified Plan 3.42 n/a n/a n/a n/a n/a Chittenden Qualified Plan (1) n/a n/a 3.62 n/a n/a n/a Suffolk Qualified Plan (1) n/a n/a 3.72 n/a n/a n/a Rate of compensation increase n/a n/a n/a n/a n/a n/a Weighted-average assumptions used to determine net Discount rate: People’s Qualified Plan (2) 4.41 % 3.74%/4.34% 4.41 % 4.40 % 3.70 % 4.40 % First Connecticut Qualified Plan 4.41 4.35 n/a n/a n/a n/a United Financial Qualified Plan 3.33 n/a n/a n/a n/a n/a Chittenden Qualified Plan (1) n/a n/a 4.16 n/a n/a n/a Suffolk Qualified Plan (1) n/a n/a 4.24 n/a n/a n/a Expected return on plan assets People’s Qualified Plan 7.25 7.25 7.25 n/a n/a n/a First Connecticut Qualified Plan 6.00 6.00 n/a n/a n/a n/a United Financial Qualified Plan 5.25 n/a n/a n/a n/a n/a Rate of compensation increase n/a n/a n/a n/a n/a n/a Assumed health care cost trend rates at December 31: Health care cost trend rate assumed for next year n/a n/a n/a 5.70 % 6.00 % 6.20 % Rate to which the cost trend rate is assumed to decline (the ultimate trend rate) n/a n/a n/a 4.50 4.50 4.50 Year that the rate reaches the ultimate trend rate n/a n/a n/a 2037 2037 2037 n/a — not applicable (1) Effective October 1, 2018, the Chittenden Qualified Plan and the Suffolk Qualified Plan were merged into the People’s Qualified Plan. (2) Rate of 3.74% through September 30, 2018 and 4.34% through December 31, 2018. The discount rates used to determine the benefit obligation of the Supplemental Plans at December 31, 2019 ranged from 2.76% to 3.40%, while the discount rate used to determine net periodic benefit (income) expense for 2019 ranged from 3.33% to 4.40%. The discount rates used to determine the benefit obligation of the People’s Supplemental Plans at December 31, 2018 ranged from 4.00% to 4.40%, while the discount rate used to determine net periodic benefit (income) expense for 2018 ranged from 3.32% to 4.30%. The discount rates reflect the then current rates available on long-term high-quality fixed-income debt instruments, and are reset annually on the measurement date. To determine the discount rates, People’s United reviews, along with its independent actuary, spot interest rate yield curves based upon yields from a broad population of high-quality bonds adjusted to match the timing and amounts of expected benefit payments. People’s United uses a full yield curve approach to estimate the interest cost component of net periodic benefit income by applying the specific spot rates along the yield curve, used in the determination of the benefit obligations, to the relevant projected cash flows. In developing an expected long-term rate of return on asset assumption for the Qualified Plans for purposes of determining 2019 net periodic benefit income, People’s United considered the historical returns and the future expectations for returns within each asset class, as well as the target asset allocation of the pension portfolio. This resulted in an expected long-term rate of return assumption of 7.25% for the People’s Qualified Plan, 6.00% for the First Connecticut Qualified Plan and 5.25% for the United Financial Qualified Plan. This was intended to reflect expected asset returns over the life of the related pension benefits expected to be paid. In 2020, $22.3 million in net periodic benefit income is expected to be recognized related to the Qualified Plans. This amount was determined using the following assumptions: (i) expected long-term rates of return of 7.25% for both the People’s Qualified Plan and the First Connecticut Qualified Plan, and 5.25% for the United Financial Qualified Plan; (ii) discount rates of 3.38%, 3.39% and 3.42% for the People's Qualified Plan, the First Connecticut Qualified Plan and the United Financial Qualified Plan, respectively; and (iii) updated mortality tables issued by the Society of Actuaries in the fourth quarter of 2019. The mortality rate is a key assumption used in valuing retirement benefit obligations as it reflects the probability of future benefit payments that are contingent upon the longevity of plan participants and their beneficiaries. People’s United’s funding policy is to contribute the amounts required by applicable regulations, although additional amounts may be contributed from time to time. In February 2018, People’s United made voluntary employer contributions of $40 million to the People’s Qualified Plan and $10 million to the Chittenden Qualified Plan (none to the Suffolk Qualified Plan) in response to tax reform (see Note 13). Employer contributions for the Supplemental Plans and the Other Postretirement Plans in 2020 are expected to total $4.9 million, representing net benefit payments expected to be paid under these plans. Expected future net benefit payments for the Pension Plans as of December 31, 2019 are: $28.5 million in 2020; $30.0 million in 2021; $30.6 million in 2022; $31.2 million in 2023; $33.0 million in 2024; and an aggregate of $181.2 million in 2025 through 2029. As of December 31, 2019, expected future net benefit payments for the Other Postretirement Plans are (i) $1.1 million in each of the years 2020 through 2023, $1.0 million for 2024 and (ii) an aggregate of $4.7 million in 2025 through 2029. The investment strategy of the Qualified Plans is to develop a diversified portfolio, representing a variety of asset classes of varying duration, in order to effectively fund expected near-term and long-term benefit payments. All investment decisions are governed by an established policy that contains the following asset allocation guidelines: Asset Class Policy Target % Policy Range % Cash equivalents 1 0-20 Equity securities 65 55-75 Fixed income securities 24 10-40 Equity investments are required to be diversified among industries and economic sectors and may be invested directly in individual securities or indirectly through the use of mutual funds, trust company common funds, REIT's, investment partnerships, LLCs or exchange traded funds. Limitations have been established on the overall allocation to any individual security representing more than 3% of the market value of plan assets. A limit of 50% of equity holdings may be invested in international equities. Short sales, margin purchases, physical commodities and future contracts, and exchange traded or over-the-counter options are prohibited. Fixed income securities are oriented toward risk-averse, investment-grade securities rated “A” or higher. A limit of up to 30% of the fixed income holdings may be purchased and held indirectly in issues rated below “Baa3” by Moody’s or “BBB-” by Standard & Poor’s, if the higher investment risk is compensated for by the prospect of a positive incremental investment return. With the exception of U.S. government securities, in which the Qualified Plans may invest the entire fixed income allocation, fixed income securities require diversification among individual securities and sectors. Limitations have been established on the overall investment in securities of a single issuer to no more than 2.5% of the market value of total plan assets. There is no limit on the maximum maturity of securities held. The following table summarizes the percentages of fair value for the major categories of assets in the Qualified Plans as of the respective measurement dates: Plan Assets 2019 2018 As of December 31 People’s First Connecticut United Financial People’s First Equity securities 66 % 66 % 9 % 70 % 73 % Cash and fixed income securities 34 34 91 30 27 Total 100 % 100 % 100 % 100 % 100 % (1) The United Financial Qualified Plan is not yet aligned with the Company's investment strategy and asset allocation guidelines as the acquisition of United Financial occurred effective November 1, 2019. The following tables present the Qualified Plans’ assets measured at fair value: Fair Value Measurements Using As of December 31, 2019 (in millions) Level 1 Level 2 Level 3 Total Cash and cash equivalents $ 18.9 $ — $ — $ 18.9 Equity securities: Common stocks 261.2 — — 261.2 Mutual funds — 215.2 — 215.2 Fixed income securities: U.S. Treasury — 104.8 — 104.8 Corporate — 73.0 — 73.0 Mutual funds — 72.5 — 72.5 Other — 1.1 — 1.1 Total $ 280.1 $ 466.6 $ — $ 746.7 Fair Value Measurements Using As of December 31, 2018 (in millions) Level 1 Level 2 Level 3 Total Cash and cash equivalents $ 15.2 $ — $ — $ 15.2 Equity securities: Common stocks 216.6 — — 216.6 Mutual funds — 201.1 — 201.1 Fixed income securities: Corporate — 68.5 — 68.5 U.S. Treasury — 58.6 — 58.6 Mutual funds — 32.9 — 32.9 Other — 3.5 — 3.5 Total $ 231.8 $ 364.6 $ — $ 596.4 Employee Stock Ownership Plan In April 2007, People’s United established an ESOP. At that time, People’s United loaned the ESOP $216.8 million to purchase 10,453,575 shares of People’s United common stock in the open market. In order for the ESOP to repay the loan, People’s United expects to make annual cash contributions of approximately $18.8 million until 2036. Such cash contributions may be reduced by the cash dividends paid on unallocated ESOP shares, which totaled $4.4 million in 2019, $4.6 million in 2018 and $4.8 million in 2017. At December 31, 2019, the loan balance totaled $171.8 million. Employee participation in this plan is restricted to those employees who (i) are at least 18 years of age and (ii) worked at least 1000 hours within 12 months of their hire date or any plan year (January 1 to December 31) after their date of hire. Employees meeting the aforementioned eligibility criteria during the plan year must continue to be employed as of the last day of the plan year in order to receive an allocation of shares for that plan year. Shares of People’s United common stock are held by the ESOP and allocated to eligible participants annually based upon a percentage of each participant’s eligible compensation. Since the ESOP was established, a total of 4,529,883 shares of People’s United common stock have been allocated or committed to be released to participants’ accounts. At December 31, 2019, 5,923,692 shares of People’s United common stock, with a fair value of $100.1 million at that date, have not been allocated or committed to be released. Compensation expense related to the ESOP is recognized at an amount equal to the number of common shares committed to be released by the ESOP for allocation to participants’ accounts multiplied by the average fair value of People’s United’s common stock during the reporting period. The difference between the fair value of the shares of People’s United’s common stock committed to be released and the cost of those common shares is recorded as a credit to additional paid-in capital (if fair value exceeds cost) or, to the extent that no such credits remain in additional paid-in capital, as a charge to retained earnings (if fair value is less than cost). Expense recognized for the ESOP totaled $5.7 million, $6.2 million and $6.4 million for the years ended December 31, 2019, 2018 and 2017, respectively. Employee Savings Plans People’s United sponsors an employee savings plan that qualifies as a 401(k) plan under the Internal Revenue Code. Employees may contribute up to 50% of their pre-tax compensation up to certain limits, and People’s United makes a matching contribution equal to 100% of a participant’s contributions up to 4% of pre-tax compensation. Participants vest immediately in their own contributions and after one year in People’s United’s contributions. A supplemental savings plan has also been established for certain senior officers and the Company has funded a trust to provide benefit payments to the extent such benefits are not paid directly by People’s United. People’s United also continues to maintain, for former First Connecticut participants who met certain eligibility requirements, a funded plan that provides supplemental retirement benefits. Combined trust assets of $17.9 million as of December 31, 2019 (which are included in other assets in the Consolidated Statements of Condition) were exceeded by the related combined benefit obligations of $44.2 million at that date. Expense recognized for these employee savings plans totaled $32.3 million, $29.1 million and $25.4 million for the years ended December 31, 2019, 2018 and 2017, respectively.

Stock-Based Compensation Plans

Stock-Based Compensation Plans	12 Months Ended
	Dec. 31, 2019
Share-based Payment Arrangement [Abstract]
Stock-Based Compensation Plans	NOTE 19 – Stock-Based Compensation Plans Long-Term Incentive Plan People's United’s 2014 Plan, as amended and restated in 2017, and the predecessor 2008 Long-Term Incentive Plan (together the "Incentive Plans") provide for awards to officers and employees in the form of: (i) incentive stock options that may afford tax benefits to recipients; (ii) non-statutory stock options that do not afford tax benefits to recipients but may provide tax benefits to People's United; and (iii) stock appreciation rights, restricted stock and performance shares. A total of 75,850,000 shares of People's United common stock are reserved for issuance under the 2014 Plan. The number of shares of common stock reserved under the 2014 Plan is depleted by one share for each option or stock appreciation right, by 5.32 shares for each restricted stock award and by 7.98 shares for each performance share. At December 31, 2019, a total of 35,633,607 reserved shares remain available for future awards. Non-statutory stock options have been granted under the Incentive Plans at exercise prices equal to the fair value of People’s United common stock at the grant dates. Option expiration dates are fixed at the grant date, with a maximum term of ten years. Prior to 2013, options granted under the Incentive Plans generally vested 50% after two years, 75% after three years and 100% after four years. Beginning in 2013, options granted under the Incentive Plans vest 33% after one year, 66% after two years and 100% after three years. Unvested options become fully exercisable in the event of a change of control, as defined in the Incentive Plans. People's United has also granted restricted stock awards under the Incentive Plans. Employees become fully vested in these shares generally after a three People's United has also granted performance shares under the 2014 Plan. A performance share represents the right to receive a share of People’s United common stock contingent upon the Company achieving certain pre-established performance goals and the employee satisfying requisite service conditions. Employees become fully vested in these performance shares upon completion of a three three Performance Shares Awarded The following is a summary of performance share activity under the 2014 Plan: Shares Weighted-Average Unvested performance shares outstanding at December 31, 2016 551,985 $ 15.22 Granted 466,923 18.61 Forfeited (34,073) 16.28 Unvested performance shares outstanding at December 31, 2017 984,835 16.80 Granted 532,740 19.78 Forfeited (62,124) 17.82 Vested (2,079) 16.70 Unvested performance shares outstanding at December 31, 2018 1,453,372 17.85 Granted 637,118 17.84 Forfeited (80,319) 18.66 Vested (505,755) 15.23 Unvested performance shares outstanding at December 31, 2019 1,504,416 $ 18.68 Expense related to unvested performance shares is recognized on a straight-line basis, generally over the applicable service period, and totaled $12.2 million, $10.5 million and $7.0 million for the years ended December 31, 2019, 2018 and 2017, respectively. Unamortized cost for unvested performance shares, which reflects an estimated forfeiture rate of 5% per year over the vesting period, totaled $10.8 million at December 31, 2019, and is expected to be recognized over the remaining weighted-average vesting period of 1.8 years. The fair value of performance shares vested during the years ended December 31, 2019 and 2018 was $7.7 million and less than $0.1 million, respectively. Recognition and Retention Plan and Stock Option Plan Following shareholder approval of the 2014 Plan in 2014, no new awards may be granted under the 2008 Long-Term Incentive Plan, the 2007 Stock Option Plan (the "SOP") or the RRP (together the "Prior Plans"). All awards granted under the Prior Plans and the 1998 Long-Term Incentive Plan that were unvested (in the case of stock options and restricted stock awards) or unexercised (in the case of stock options) as of the date of shareholder approval of the 2014 Plan continue to be governed by the terms of the plan under which such awards were granted and the applicable grant agreements. The RRP and SOP (together the "2007 Plans") provided for awards to directors, officers and employees in the form of: (i) incentive stock options that may afford tax benefits to recipients; (ii) non-statutory stock options that do not afford tax benefits to recipients but may provide tax benefits to People's United; and (iii) restricted stock. Shares of People's United common stock were purchased in the open market in October 2007 by a trustee with funds provided by People's United for the maximum number of shares available to be awarded in the form of restricted stock. Previously, non-statutory stock options were granted under the SOP at exercise prices equal to the fair value of People's United's common stock at the grant date based on quoted market prices. The fair value of all restricted stock awarded under the RRP was measured at the grant date based on quoted market prices. Prior to 2014, most restricted stock awards and stock options granted under the 2007 Plans were scheduled to vest in 20% annual increments over a five three Stock Options Granted People's United granted a total of 2,807,692 stock options in 2019, 2,450,861 stock options in 2018 and 2,261,586 stock options in 2017 under the Incentive Plans. The estimated weighted-average grant-date fair value of all stock options granted in 2019, 2018 and 2017 was $2.04 per option, $2.31 per option and $1.97 per option, respectively, using the Black-Scholes option-pricing model with assumptions as follows: dividend yield of 4.0% in 2019, 3.5% in 2018 and 3.6% in 2017; expected volatility rate of 19% in 2019 and 18% in both 2018 and 2017; risk-free interest rate of 2.6% in both 2019 and 2018, and 1.9% in 2017; and expected option life of approximately 4 years in 2019, 2018 and 2017. In arriving at the grant date fair value of stock options using the Black-Scholes option-pricing model, expected volatilities were based on the historical volatilities of People's United traded common stock. The expected term of stock options represents the period of time that options granted are expected to be outstanding. People’s United used historical data to estimate voluntary suboptimal (early) exercises by continuing employees, and estimates of post-vest option exercise or forfeiture by terminated employees. Suboptimal exercise data and employee termination estimates are incorporated into Monte Carlo simulations of People’s United common stock prices to calculate the expected term. The risk-free interest rate approximated the U.S. Treasury rate curve matched to the expected option term at the time of the grant. The following is a summary of stock option activity under the Incentive Plans and the SOP: Shares Weighted-Average Weighted-Average Aggregate Options outstanding at December 31, 2016 16,555,925 $ 14.84 Granted 2,261,586 19.14 Forfeited (459,576) 17.87 Exercised (3,920,294) 15.97 Options outstanding at December 31, 2017 14,437,641 15.11 Granted 2,450,861 19.61 Forfeited (294,474) 17.87 Exercised (1,916,961) 14.55 Options outstanding at December 31, 2018 14,677,067 15.87 Granted 2,807,692 17.62 Forfeited (652,965) 18.28 Exercised (1,632,971) 14.77 Options outstanding at December 31, 2019 15,198,823 $ 16.20 6.2 $ 22.7 Options exercisable at December 31, 2019 10,551,014 $ 15.21 5.2 $ 22.7 (1) Reflects only those stock options with intrinsic value at December 31, 2019. Expense relating to stock options granted is recognized on a straight-line basis, generally over the applicable service period, and totaled $5.2 million, $5.2 million and $5.5 million for the years ended December 31, 2019, 2018 and 2017, respectively. Unamortized cost for unvested stock options, which reflects an estimated forfeiture rate of 5.0% per year over the vesting period, totaled $5.1 million at December 31, 2019, and is expected to be recognized over the remaining weighted-average vesting period of 1.6 years. The total intrinsic value of stock options exercised was $3.2 million, $8.7 million and $11.2 million for the years ended December 31, 2019, 2018 and 2017, respectively. Additional information concerning options outstanding and options exercisable at December 31, 2019 is summarized as follows: Exercise Price Range Options Outstanding Options Exercisable Weighted-Average Number Remaining Exercise Number Weighted-Average $11.53 — $14.54 3,531,960 3.4 $ 13.53 3,525,520 $ 13.53 14.55 — 14.88 4,970,387 5.0 14.73 4,970,387 14.73 14.89 — 18.40 2,689,105 9.0 17.60 57,997 16.47 18.41 — 19.71 4,007,371 7.6 19.45 1,997,110 19.36 Restricted Stock Awarded The following is a summary of restricted stock award activity under the Incentive Plans and the RRP: Shares Weighted-Average Unvested restricted shares outstanding at December 31, 2016 886,082 $ 14.59 Granted 303,090 18.84 Forfeited (31,828) 15.56 Vested (485,023) 14.49 Unvested restricted shares outstanding at December 31, 2017 672,321 16.53 Granted 489,789 18.50 Forfeited (29,426) 17.81 Vested (402,134) 16.04 Unvested restricted shares outstanding at December 31, 2018 730,550 18.03 Granted 383,420 17.44 Forfeited (68,091) 17.11 Vested (347,078) 17.49 Unvested restricted shares outstanding at December 31, 2019 698,801 $ 18.07 Expense relating to unvested restricted stock awards is recognized on a straight-line basis, generally over the applicable service period, and totaled $6.6 million, $5.8 million and $6.4 million for the years ended December 31, 2019, 2018 and 2017, respectively. Unamortized cost for unvested restricted stock awards, which reflects an estimated forfeiture rate of 5.0% per year over the vesting period, totaled $7.0 million at December 31, 2019, and is expected to be recognized over the remaining weighted-average vesting period of 1.5 years. The total fair value of restricted stock awards vested during the years ended December 31, 2019, 2018 and 2017 was $6.0 million, $7.5 million and $9.3 million, respectively. During 2019, 2018 and 2017, employees of People's United tendered a total of 115,632 shares, 136,426 shares and 216,969 shares of common stock, respectively, in satisfaction of their related tax withholding obligations upon the vesting of restricted stock awards granted in prior periods and/or in payment of the exercise price and satisfaction of their related tax withholding obligations upon the exercise of stock options granted in prior periods. There is no limit on the number of shares that may be tendered by employees of People's United in the future for these purposes. Shares acquired in payment of the stock option exercise price or in satisfaction of tax withholding obligations are not eligible for reissuance in connection with any subsequent grants made pursuant to equity compensation plans maintained by People's United. Rather, all shares acquired in this manner are retired by People’s United, resuming the status of authorized but unissued shares of People’s United’s common stock. The total cost of shares repurchased and retired applicable to restricted stock awards during the years ended December 31, 2019, 2018 and 2017 was $2.0 million, $2.5 million and $3.3 million, respectively. Directors’ Equity Compensation Plan The People's United Financial, Inc. Directors' Equity Compensation Plan (the "Directors' Plan") provides for an annual award of shares of People's United common stock with a fair value of approximately $95,000 to each non-employee director immediately following each annual meeting of shareholders. Shares of People's United common stock issued pursuant to the Directors' Plan are subject to a one In 2019, 2018 and 2017, directors were granted a total of 58,340 shares, 51,680 shares and 49,050 shares, respectively, of People’s United common stock, with grant date fair values of $16.31 per share, $18.21 per share and $17.65 per share, respectively, at those dates. Expense totaling $0.9 million for the Directors’ Plan was recognized for each of the years ended December 31, 2019, 2018 and 2017. At December 31, 2019, a total of 333,981 shares remain available for issuance.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Fair Value Measurements	NOTE 20 – Fair Value Measurements Described below are the valuation methodologies used by People’s United and the resulting fair values for those financial instruments measured at fair value on both a recurring and a non-recurring basis. For those financial instruments not measured at fair value either on a recurring or non-recurring basis, disclosure of each instrument’s carrying amount and estimated fair value has been provided. Recurring Fair Value Measurements Trading Debt Securities, Equity Securities and Debt Securities Available-For-Sale When available, People’s United uses quoted market prices for identical securities received from an independent, nationally-recognized, third-party pricing service (as discussed further below) to determine the fair value of investment securities such as U.S. Treasury and agency securities and equity securities that are included in Level 1. When quoted market prices for identical securities are unavailable, People’s United uses prices provided by the independent pricing service based on recent trading activity and other observable information including, but not limited to, market interest rate curves, referenced credit spreads and estimated prepayment rates where applicable. These investments include certain U.S. and government agency debt securities, corporate and municipal debt securities and GSE mortgage-backed and CMO securities, all of which are included in Level 2. The Company’s available-for-sale debt securities are primarily comprised of GSE mortgage-backed securities. The fair value of these securities is based on prices obtained from the independent pricing service. The pricing service uses various techniques to determine pricing for the Company’s mortgage-backed securities, including option pricing and discounted cash flow analysis. The inputs include benchmark yields, reported trades, broker/dealer quotes, issuer spreads, benchmark securities, bids, offers, reference data, monthly payment information and collateral performance. At December 31, 2019, the entire available-for-sale mortgage-backed securities portfolio was comprised of GSE mortgage-backed and CMO securities with original final maturities ranging from 10 to 40 years. At December 31, 2018, the entire available-for-sale mortgage-backed securities portfolio was comprised of GSE mortgage-backed securities with original final maturities of 10- and 15-years. An active market exists for securities that are similar to the Company’s GSE mortgage-backed and CMO securities, making observable inputs readily available. Changes in the prices obtained from the pricing service are analyzed from month to month, taking into consideration changes in market conditions including changes in mortgage spreads, changes in U.S. Treasury security yields and changes in generic pricing of securities with similar duration. As a further point of validation, the Company generates its own month-end fair value estimate for all mortgage-backed securities, and state and municipal securities. While the Company has not adjusted the prices obtained from the independent pricing service, any notable differences between those prices and the Company’s estimates are subject to further analysis. This additional analysis may include a review of prices provided by other independent parties, a yield analysis, a review of average life changes using Bloomberg analytics and a review of historical pricing for the particular security. Based on management’s review of the prices provided by the pricing service, the fair values incorporate observable market inputs used by market participants at the measurement date and, as such, are classified as Level 2 securities. Other Assets As discussed in Note 18, certain unfunded, nonqualified supplemental plans have been established to provide retirement benefits to certain senior officers. People’s United has funded two trusts to provide benefit payments to the extent such benefits are not paid directly by People’s United, the assets of which are included in other assets in the Consolidated Statements of Condition. When available, People’s United determines the fair value of the trust assets using quoted market prices for identical securities received from a third-party nationally recognized pricing service. Derivatives People’s United values its derivatives using internal models that are based on market or observable inputs, including interest rate curves and forward/spot prices for selected currencies. Derivative assets and liabilities included in Level 2 represent interest rate swaps and caps, foreign exchange contracts, risk participation agreements, forward commitments to sell residential mortgage loans and interest rate-lock commitments on residential mortgage loans. The following tables summarize People’s United’s financial instruments that are measured at fair value on a recurring basis: Fair Value Measurements Using As of December 31, 2019 (in millions) Level 1 Level 2 Level 3 Total Financial assets: Trading debt securities: U.S. Treasury $ 7.1 $ — $ — $ 7.1 Debt securities available-for-sale: U.S. Treasury and agency 687.1 — — 687.1 GSE mortgage-backed and CMO securities — 2,877.2 — 2,877.2 Equity securities 8.2 — — 8.2 Other assets: Exchange-traded funds 47.7 — — 47.7 Mutual funds 3.3 — — 3.3 Interest rate swaps — 337.6 — 337.6 Interest rate caps — 1.7 — 1.7 Foreign exchange contracts — 1.2 — 1.2 Forward commitments to sell residential mortgage loans — 0.5 — 0.5 Total $ 753.4 $ 3,218.2 $ — $ 3,971.6 Financial liabilities: Interest rate swaps $ — $ 92.1 $ — $ 92.1 Interest rate caps — 1.7 — 1.7 Risk participation agreements — 0.1 — 0.1 Foreign exchange contracts — 1.8 — 1.8 Interest rate-lock commitments on residential mortgage loans — 0.5 — 0.5 Total $ — $ 96.2 $ — $ 96.2 Fair Value Measurements Using As of December 31, 2018 (in millions) Level 1 Level 2 Level 3 Total Financial assets: Trading debt securities: U.S. Treasury $ 8.4 $ — $ — $ 8.4 Debt securities available-for-sale: U.S. Treasury and agency 678.0 — — 678.0 GSE mortgage-backed securities — 2,443.0 — 2,443.0 Equity securities 8.1 — — 8.1 Other assets: Exchange-traded funds 35.5 — — 35.5 Mutual funds 20.6 — — 20.6 Fixed income securities — 0.3 — 0.3 Interest rate swaps — 98.9 — 98.9 Interest rate caps — 3.1 — 3.1 Foreign exchange contracts — 0.9 — 0.9 Forward commitments to sell residential mortgage loans — 0.1 — 0.1 Total $ 750.6 $ 2,546.3 $ — $ 3,296.9 Financial liabilities: Interest rate swaps $ — $ 135.0 $ — $ 135.0 Interest rate caps — 3.1 — 3.1 Risk participation agreements (1) — — — — Foreign exchange contracts — 0.8 — 0.8 Interest rate-lock commitments on residential mortgage loans — 0.1 — 0.1 Total $ — $ 139.0 $ — $ 139.0 (1) At December 31, 2018, the fair value of risk participation agreements totaled less than $0.1 million (see Note 22). Non-Recurring Fair Value Measurements Loans Held-for-Sale Loans held-for-sale are recorded at the lower of cost or fair value and are therefore measured at fair value on a non-recurring basis. When available, People’s United uses observable secondary market data, including pricing on recent closed market transactions for loans with similar characteristics. Accordingly, such loans are classified as Level 2 measurements. When observable data is unavailable, valuation methodologies using current market interest rate data adjusted for inherent credit risk are used, and such loans are included in Level 3. Impaired Loans Loan impairment is deemed to exist when full repayment of principal and interest according to the contractual terms of the loan is no longer probable. Impaired loans are reported based on one of three measures: (i) the present value of expected future cash flows discounted at the loan’s original effective interest rate; (ii) the loan’s observable market price; or (iii) the fair value of the collateral (less estimated cost to sell) if the loan is collateral dependent. Accordingly, certain impaired loans may be subject to measurement at fair value on a non-recurring basis. People’s United has estimated the fair values of these assets using Level 3 inputs, such as discounted cash flows based on inputs that are largely unobservable and, instead, reflect management’s own estimates of the assumptions a market participant would use in pricing such loans and/or the fair value of collateral based on independent third-party appraisals for collateral-dependent loans. Such appraisals are based on the market and/or income approach to value and are subject to a discount (to reflect estimated cost to sell) that generally approximates 10%. REO and Repossessed Assets REO and repossessed assets are recorded at the lower of cost or fair value, less estimated selling costs, and are therefore measured at fair value on a non-recurring basis. People’s United has estimated the fair values of these assets using Level 3 inputs, such as independent third-party appraisals and price opinions. Such appraisals are based on the market and/or income approach to value and are subject to a discount (to reflect estimated cost to sell) that generally approximates 10%. Assets that are acquired through loan default are recorded as held-for-sale initially at the lower of the recorded investment in the loan or fair value (less estimated selling costs) upon the date of foreclosure/repossession. Subsequent to foreclosure/repossession, valuations are updated periodically and the carrying amounts of these assets may be reduced further. Mortgage Servicing Rights Mortgage servicing rights are evaluated for impairment based upon the fair value of the servicing rights as compared to their amortized cost. The fair value of mortgage servicing rights is based on a valuation model that calculates the present value of estimated net servicing income. This model incorporates certain assumptions that market participants would likely use in estimating future net servicing income, such as interest rates, prepayment speeds and the cost to service (including delinquency and foreclosure costs), all of which require a degree of management judgment. Adjustments are only recorded when the discounted cash flows derived from the valuation model are less than the carrying value of the asset. As such, mortgage servicing rights are subject to measurement at fair value on a non-recurring basis and are classified as Level 3 assets. The following tables summarize People’s United’s assets that are measured at fair value on a non-recurring basis: Fair Value Measurements Using As of December 31, 2019 (in millions) Level 1 Level 2 Level 3 Total Loans held-for-sale: Commercial (1) $ — $ — $ 157.9 $ 157.9 Other consumer (1) — — 333.7 333.7 Residential (2) — 19.7 — 19.7 Impaired loans (3) — — 61.9 61.9 REO and repossessed assets (4) — — 23.4 23.4 Mortgage servicing rights (1) — — 10.3 10.3 Total $ — $ 19.7 $ 587.2 $ 606.9 Fair Value Measurements Using As of December 31, 2018 (in millions) Level 1 Level 2 Level 3 Total Loans held-for-sale - Residential (2) $ — $ 19.5 $ — $ 19.5 Impaired loans (3) — — 55.2 55.2 REO and repossessed assets (4) — — 18.1 18.1 Total $ — $ 19.5 $ 73.3 $ 92.8 (1) Fair value adjustments recorded for the year ended December 31, 2019 were immaterial. (2) No fair value adjustments were recorded for the years ended December 31, 2019 and 2018. (3) Represents the recorded investment in originated impaired loans with a related allowance for loan losses measured in accordance with applicable accounting guidance. The total consists of $49.0 million of Commercial loans and $12.9 million of Retail loans at December 31, 2019. The provision for loan losses on impaired loans totaled $9.3 million and $8.6 million for the years ended December 31, 2019 and 2018, respectively. (4) Represents: (i) $11.9 million of residential REO; (ii) $7.3 million of commercial REO; and (iii) $4.2 million of repossessed assets at December 31, 2019. Charge-offs to the allowance for loan losses related to loans that were transferred to REO or repossessed assets totaled $2.8 million and $1.7 million for the years ended December 31, 2019 and 2018, respectively. Write downs and net loss on sale of foreclosed/repossessed assets charged to non-interest expense totaled $1.1 million and $0.2 million for the same periods. Financial Assets and Financial Liabilities Not Measured At Fair Value The following tables summarize the carrying amounts, estimated fair values and placement in the fair value hierarchy of People’s United’s financial instruments that are not measured at fair value either on a recurring or non-recurring basis: Carrying Estimated Fair Value As of December 31, 2019 (in millions) Level 1 Level 2 Level 3 Total Financial assets: Cash and due from banks $ 484.2 $ 484.2 $ — $ — $ 484.2 Short-term investments 316.8 — 316.8 — 316.8 Debt securities held-to-maturity 3,869.2 — 4,018.5 1.5 4,020.0 FHLB and FRB stock 341.1 — 341.1 — 341.1 Total loans, net (1) 43,287.6 — 10,072.1 33,282.9 43,355.0 Financial liabilities: Time deposits 9,205.5 — 9,218.1 — 9,218.1 Other deposits 34,384.0 — 34,384.0 — 34,384.0 FHLB advances 3,125.4 — 3,125.5 — 3,125.5 Federal funds purchased 1,620.0 — 1,620.0 — 1,620.0 Customer repurchase agreements 409.1 — 409.1 — 409.1 Notes and debentures 993.1 — 1,021.3 — 1,021.3 (1) Excludes impaired loans totaling $61.9 million measured at fair value on a non-recurring basis. Carrying Estimated Fair Value As of December 31, 2018 (in millions) Level 1 Level 2 Level 3 Total Financial assets: Cash and due from banks $ 665.7 $ 665.7 $ — $ — $ 665.7 Short-term investments 266.3 — 266.3 — 266.3 Debt securities held-to-maturity 3,792.3 — 3,774.4 1.5 3,775.9 FHLB and FRB stock 303.4 — 303.4 — 303.4 Total loans, net (1) 34,945.8 — 7,806.1 26,800.2 34,606.3 Financial liabilities: Time deposits 6,916.2 — 6,884.0 — 6,884.0 Other deposits 29,242.8 — 29,242.8 — 29,242.8 FHLB advances 2,404.5 — 2,404.5 — 2,404.5 Federal funds purchased 845.0 — 845.0 — 845.0 Customer repurchase agreements 332.9 — 332.9 — 332.9 Other borrowings 11.0 — 11.0 — 11.0 Notes and debentures 895.8 — 893.4 — 893.4 (1) Excludes impaired loans totaling $55.2 million measured at fair value on a non-recurring basis.

Legal Proceedings

Legal Proceedings	12 Months Ended
	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Legal Proceedings	NOTE 21 – Legal Proceedings In the normal course of business, People’s United is subject to various legal proceedings. Management has discussed with legal counsel the nature of these legal proceedings and, based on the advice of counsel and the information currently available, believes that the eventual outcome of these legal proceedings will not have a material adverse effect on People’s United’s financial condition, results of operations or liquidity.

Financial Instruments

Financial Instruments	12 Months Ended
	Dec. 31, 2019
Investments, All Other Investments [Abstract]
Financial Instruments	NOTE 22 – Financial Instruments In the normal course of business, People’s United is a party to both on-balance-sheet and off-balance-sheet financial instruments involving, to varying degrees, elements of credit risk and IRR in addition to the amounts recognized in the Consolidated Statements of Condition. The contractual amounts of off-balance-sheet instruments reflect the extent of People’s United’s involvement in particular classes of financial instruments. A summary of the contractual or notional amounts of People’s United’s lending-related and derivative financial instruments follows: As of December 31 (in millions) 2019 2018 Lending-Related Financial Instruments: (1) Loan origination commitments and unadvanced lines of credit: Commercial and industrial $ 5,549.9 $ 4,937.1 Home equity and other consumer 3,401.9 2,646.6 Commercial real estate 1,614.9 1,095.4 Equipment financing 471.0 459.7 Residential mortgage 54.7 78.7 Letters of credit: Stand-by 185.2 139.4 Commercial 4.4 5.0 Derivative Financial Instruments: (2) Interest rate swaps: For market risk management 585.0 585.0 For commercial customers: Customer 8,847.7 7,455.9 Institutional counterparties 8,851.8 7,161.3 Interest rate caps: For commercial customers: Customer 246.0 329.1 Institutional counterparties 246.0 329.1 Risk participation agreements 882.8 576.5 Foreign exchange contracts 180.4 145.2 Forward commitments to sell residential mortgage loans 23.3 9.5 Interest rate-lock commitments on residential mortgage loans 33.6 13.6 (1) The contractual amounts of these financial instruments represent People’s United’s maximum potential exposure to credit loss, assuming: (i) the instruments are fully funded at a later date; (ii) the borrower does not meet contractual repayment obligations; and (iii) any collateral or other security proves to be worthless. (2) The contractual or notional amounts of these financial instruments are substantially greater than People’s United’s maximum potential exposure to credit loss. Lending-Related Financial Instruments The contractual amounts of People’s United’s lending-related financial instruments do not necessarily represent future cash requirements since certain of these instruments may expire without being funded and others may not be fully drawn upon. These instruments are subject to People’s United’s credit approval process, including an evaluation of the customer’s creditworthiness and related collateral requirements. Commitments generally have fixed expiration dates or other termination clauses and may require the payment of a fee by the customer. The geographic distribution of People’s United’s lending-related financial instruments is similar to the distribution of its loan portfolio as described in Note 5. People’s United issues both stand-by and commercial letters of credit. Stand-by letters of credit are conditional commitments issued by People’s United to guarantee the performance of a customer to a third party. The letter of credit is generally extended for an average term of one year and is secured in a manner similar to existing extensions of credit. For each letter of credit issued, if the customer fails to perform under the terms of the agreement, People’s United would have to fulfill the terms of the letter of credit. The credit risk involved in issuing stand-by letters of credit is essentially the same as that involved in extending loan facilities to customers. A commercial letter of credit is normally a short-term instrument issued by a financial institution on behalf of its customer. The letter of credit authorizes a beneficiary to draw drafts on the financial institution or one of its correspondent banks, provided the terms and conditions of the letter of credit have been met. In issuing a commercial letter of credit, the financial institution has substituted its credit standing for that of its customer. After drafts are paid by the financial institution, the customer is charged or an obligation is created under an existing reimbursement agreement. An advance under a reimbursement agreement is recorded as a loan by the financial institution and is subject to terms and conditions similar to other commercial obligations. The fair value of People’s United’s obligations relating to its unfunded loan commitments and letters of credit was $5.6 million and $2.7 million at December 31, 2019 and 2018, respectively, and is included in other liabilities in the Consolidated Statements of Condition. Derivative Financial Instruments and Hedging Activities People’s United uses derivative financial instruments as components of its market risk management (principally to manage IRR). Certain other derivatives are entered into in connection with transactions with commercial customers. Derivatives are not used for speculative purposes. By using derivatives, People’s United is exposed to credit risk to the extent that counterparties to the derivative contracts do not perform as required. Should a counterparty fail to perform under the terms of a derivative contract, the Company’s counterparty credit risk is equal to the amount reported as a derivative asset in the Consolidated Statements of Condition. In accordance with the Company’s balance sheet offsetting policy (see Note 1), amounts reported as derivative assets represent derivative contracts in a gain position, without consideration for derivative contracts in a loss position with the same counterparty (to the extent subject to master netting arrangements) and posted collateral. People’s United seeks to minimize counterparty credit risk through credit approvals, limits, monitoring procedures, execution of master netting arrangements and obtaining collateral, where appropriate. Counterparties to People’s United’s derivatives include major financial institutions and exchanges that undergo comprehensive and periodic internal credit analysis as well as maintain investment grade credit ratings from the major credit rating agencies. As such, management believes the risk of incurring credit losses on derivative contracts with those counterparties is remote and losses, if any, would be immaterial. Certain of People’s United’s derivative contracts contain provisions establishing collateral requirements (subject to minimum collateral posting thresholds) based on the Company’s external credit rating. If the Company’s senior unsecured debt rating were to fall below the level generally recognized as investment grade, the counterparties to such derivative contracts could require additional collateral on those derivative transactions in a net liability position (after considering the effect of master netting arrangements and posted collateral). The aggregate fair value of derivative instruments with such credit-related contingent features that were in a net liability position at December 31, 2019 was $0.5 million, for which People’s United had posted no collateral in the normal course of business. If the Company’s senior unsecured debt rating had fallen below investment grade as of that date, $0.5 million in additional collateral would have been required. The following sections further discuss each class of derivative financial instrument used by People’s United, including management’s principal objectives and risk management strategies. Interest Rate Swaps People’s United may, from time to time, enter into interest rate swaps that are used to manage IRR associated with certain interest-earning assets and interest-bearing liabilities. The Bank has entered into pay floating/receive fixed interest rate swaps to reduce its IRR exposure to the variability in interest cash flows on certain floating-rate commercial loans. The Bank has agreed with the swap counterparties to exchange, at specified intervals, the difference between fixed-rate and floating-rate interest amounts calculated based on notional amounts totaling $210 million. The floating-rate interest payments made under the swaps are calculated using the same floating rate received on the commercial loans. The swaps effectively convert the floating-rate one-month LIBOR interest payments received on the commercial loans to a fixed rate and consequently reduce the Bank’s exposure to variability in short-term interest rates. These swaps are accounted for as cash flow hedges. The Bank has entered into a pay floating/receive fixed interest rate swap to hedge the change in fair value due to changes in interest rates of the Bank’s $400 million subordinated notes. The Bank has agreed with the swap counterparty to exchange, at specified intervals, the difference between fixed-rate and floating-rate interest amounts calculated based on a notional amount of $375 million. The fixed-rate interest payments received on the swap will essentially offset the fixed-rate interest payments made on these notes, notwithstanding the notional difference between these notes and the swap. The floating-rate interest amounts paid under the swap are calculated based on three-month LIBOR plus 126.5 basis points. The swap effectively converts the fixed-rate subordinated notes to a floating-rate liability. This swap is accounted for as a fair value hedge. Customer Derivatives People’s United enters into interest rate swaps and caps with certain of its commercial customers. In order to minimize its risk, these customer interest rate swaps (pay floating/receive fixed) and caps have been offset with essentially matching interest rate swaps (pay fixed/receive floating) and caps with People’s United’s institutional counterparties. Hedge accounting has not been applied for these derivatives. Accordingly, changes in the fair value of all such interest rate swaps and caps are recognized in current earnings. Foreign Exchange Contracts Foreign exchange contracts are commitments to buy or sell foreign currency on a future date at a contractual price. People’s United uses these instruments on a limited basis to (i) eliminate its exposure to fluctuations in currency exchange rates on certain of its commercial loans that are denominated in foreign currencies and (ii) provide foreign exchange contracts on behalf of commercial customers within credit exposure limits. Gains and losses on foreign exchange contracts substantially offset the translation gains and losses on the related loans. Risk Participation Agreements People’s United enters into risk participation agreements under which it may either assume or sell credit risk associated with a borrower’s performance under certain interest rate derivative contracts. In those instances in which People’s United has assumed credit risk, it is not a party to the derivative contract and has entered into the risk participation agreement because it is also a party to the related loan agreement with the borrower. In those instances in which People’s United has sold credit risk, it is a party to the derivative contract and has entered into the risk participation agreement because it sold a portion of the related loan. People’s United manages its credit risk under risk participation agreements by monitoring the creditworthiness of the borrower, based on its normal credit review process. The notional amounts of the risk participation agreements reflect People’s United’s pro-rata share of the derivative contracts, consistent with its share of the related loans. Forward Commitments to Sell Residential Mortgage Loans and Related Interest Rate-Lock Commitments People’s United enters into forward commitments to sell adjustable-rate and fixed-rate residential mortgage loans (all to be sold servicing released) in order to reduce the market risk associated with originating loans for sale in the secondary market. In order to fulfill a forward commitment, People’s United delivers originated loans at prices or yields specified by the contract. The risks associated with such contracts arise from the possible inability of counterparties to meet the contract terms or People’s United’s inability to originate the necessary loans. Gains and losses realized on the forward contracts are reported in the Consolidated Statements of Income as a component of the net gains on sales of residential mortgage loans. In the normal course of business, People’s United will commit to an interest rate on a mortgage loan application at the time of application, or anytime thereafter. The risks associated with these interest rate-lock commitments arise if market interest rates change prior to the closing of these loans. Both forward sales commitments and interest rate-lock commitments made to borrowers on held-for-sale loans are accounted for as derivatives, with changes in fair value recognized in current earnings. Interest Rate Locks In connection with its planned issuance of senior notes in the fourth quarter of 2012, People’s United entered into U.S. Treasury forward interest rate locks (“T-Locks”) to hedge the risk that the 10-year U.S. Treasury yield component of the underlying coupon of the fixed-rate senior notes would rise prior to establishing the fixed interest rate on the senior notes. Upon pricing the senior notes, the T-Locks were terminated and the unrealized gain of $0.9 million was included (on a net-of-tax basis) as a component of AOCL. The gain is being recognized as a reduction of interest expense over the ten-year period during which the hedged item ($500 million senior note issuance) affects earnings. The portion of the unrecognized gain at December 31, 2019 that is expected to be recognized over the next 12 months totals approximately $0.1 million. The table below provides a summary of the notional amounts and fair values (presented on a gross basis) of derivatives outstanding: Fair Values (1) Type of Notional Amounts Assets Liabilities As of December 31 (in millions) 2019 2018 2019 2018 2019 2018 Derivatives Not Designated as Hedging Interest rate swaps: Commercial customers N/A $ 8,847.7 $ 7,455.9 $ 320.5 $ 76.3 $ 13.9 $ 102.6 Institutional counterparties N/A 8,851.8 7,161.3 17.1 22.6 78.2 32.4 Interest rate caps: Commercial customers N/A 246.0 329.1 1.6 0.6 0.1 2.5 Institutional counterparties N/A 246.0 329.1 0.1 2.5 1.6 0.6 Risk participation agreements (2) N/A 882.8 576.5 — — 0.1 — Foreign exchange contracts N/A 180.4 145.2 1.2 0.9 1.8 0.8 Forward commitments to sell N/A 23.3 9.5 0.5 0.1 — — Interest rate-lock commitments on N/A 33.6 13.6 — — 0.5 0.1 Total 341.0 103.0 96.2 139.0 Derivatives Designated as Hedging Interest rate swaps: Subordinated notes Fair value 375.0 375.0 — — — — Loans Cash flow 210.0 210.0 — — — — Total — — — — Total fair value of $ 341.0 $ 103.0 $ 96.2 $ 139.0 (1) Assets are recorded in other assets and liabilities are recorded in other liabilities. (2) Fair value totaled less than $0.1 million at December 31, 2018. The following table summarizes the impact of People’s United’s derivatives on pre-tax income and AOCL: Type of Amount of Pre-Tax Gain (Loss) Amount of Pre-Tax Gain (Loss) Years ended December 31 (in millions) 2019 2018 2017 2019 2018 2017 Derivatives Not Designated as Interest rate swaps: Commercial customers N/A $ 374.9 $ (3.6) $ 5.3 $ — $ — $ — Institutional counterparties N/A (350.3) 17.1 6.1 — — — Interest rate caps: Commercial customers N/A 1.4 1.1 0.7 — — — Institutional counterparties N/A (1.5) (1.0) (0.3) — — — Foreign exchange contracts N/A 1.0 0.9 0.5 — — — Risk participation agreements N/A (0.4) 0.2 — — — — Forward commitments to sell N/A 0.3 (0.1) (0.2) — — — Interest rate-lock commitments on N/A (0.4) 0.1 0.3 — — — Total 25.0 14.7 12.4 — — — Derivatives Designated as Interest rate swaps Fair value 0.3 2.1 5.9 — — — Interest rate swaps Cash flow (1.2) (0.6) 0.8 1.9 (1.7) (1.0) Interest rate locks Cash flow 0.1 0.1 0.1 — — — Total (0.8) 1.6 6.8 1.9 (1.7) (1.0) Total $ 24.2 $ 16.3 $ 19.2 $ 1.9 $ (1.7) $ (1.0) (1) Amounts recognized in earnings are recorded in interest income, interest expense or other non-interest income for derivatives designated as hedging instruments and in other non-interest income for derivatives not designated as hedging instruments.

Balance Sheet Offsetting

Balance Sheet Offsetting	12 Months Ended
	Dec. 31, 2019
Offsetting [Abstract]
Balance Sheet Offsetting	NOTE 23 – Balance Sheet Offsetting The Chicago Mercantile Exchange (“CME”) legally characterizes variation margin payments for over-the-counter derivatives that clear as settlements rather than collateral. Accordingly, the Company’s accounting policies classify, for accounting and presentation purposes, variation margin payments deemed to be legal settlements as a single unit of account with the related derivative(s). At both December 31, 2019 and 2018, this presentation impacted one of the Company’s institutional counterparties. As such, People’s United has, subject to the corresponding enforceable master netting arrangement, netted the institutional counterparty’s CME derivative position and offset the counterparty’s variation margin payments in the Consolidated Statement of Condition as of both dates. The following tables provide a gross presentation, the effects of offsetting, and a net presentation of the Company’s financial instruments that are eligible for offset in the Consolidated Statements of Condition. The collateral amounts in these tables are limited to the outstanding balances of the related asset or liability (after netting is applied) and, therefore, instances of overcollateralization are not presented. In the tables below, the Net Amount Presented of the derivative assets and liabilities can be reconciled to the fair value of the Company’s derivative financial instruments in Note 22. The Company’s derivative contracts with commercial customers and customer repurchase agreements are not subject to master netting arrangements and, therefore, have been excluded from the tables below. Gross Gross Net Gross Amounts Not Offset Net As of December 31, 2019 (in millions) Financial Collateral Financial assets: Interest rate swaps/caps: Counterparty A $ 0.2 $ — $ 0.2 $ (0.2) $ — $ — Counterparty B 0.1 — 0.1 (0.1) — — Counterparty C 0.4 — 0.4 (0.4) — — Counterparty D 0.1 — 0.1 (0.1) — — Counterparty E 15.3 — 15.3 — — 15.3 Other counterparties 1.1 — 1.1 (1.1) — — Foreign exchange contracts 1.2 — 1.2 — — 1.2 Total $ 18.4 $ — $ 18.4 $ (1.9) $ — $ 16.5 Financial liabilities: Interest rate swaps/caps: Counterparty A $ 2.3 $ — $ 2.3 $ (0.2) $ (2.1) $ — Counterparty B 5.5 — 5.5 (0.1) (5.4) — Counterparty C 28.2 — 28.2 (0.4) (27.8) — Counterparty D 10.9 — 10.9 (0.1) (10.8) — Counterparty E — — — — — — Other counterparties 32.9 — 32.9 (1.1) (31.8) — Foreign exchange contracts 1.8 — 1.8 — — 1.8 Total $ 81.6 $ — $ 81.6 $ (1.9) $ (77.9) $ 1.8 Gross Gross Net Gross Amounts Not Offset Net As of December 31, 2018 (in millions) Financial Collateral Financial assets: Interest rate swaps/caps: Counterparty A $ 3.1 $ — $ 3.1 $ (1.4) $ (1.7) $ — Counterparty B 2.5 — 2.5 (2.5) — — Counterparty C 4.8 — 4.8 (3.7) (1.1) — Counterparty D 3.6 — 3.6 (2.7) (0.1) 0.8 Counterparty E — — — — — — Other counterparties 11.1 — 11.1 (5.4) (5.7) — Foreign exchange contracts 0.9 — 0.9 — — 0.9 Total $ 26.0 $ — $ 26.0 $ (15.7) $ (8.6) $ 1.7 Financial liabilities: Interest rate swaps/caps: Counterparty A $ 1.4 $ — $ 1.4 $ (1.4) $ — $ — Counterparty B 3.8 — 3.8 (2.5) (1.2) 0.1 Counterparty C 3.7 — 3.7 (3.7) — — Counterparty D 2.7 — 2.7 (2.7) — — Counterparty E 16.0 — 16.0 — — 16.0 Other counterparties 5.4 — 5.4 (5.4) — — Foreign exchange contracts 0.8 — 0.8 — — 0.8 Total $ 33.8 $ — $ 33.8 $ (15.7) $ (1.2) $ 16.9 The following tables show the extent to which assets and liabilities exchanged under resale and repurchase agreements have been offset in the Consolidated Statements of Condition. These agreements: (i) are entered into simultaneously with the same financial institution counterparty; (ii) have the same principal amounts and inception/maturity dates; and (iii) are subject to a master netting arrangement that contains a conditional right of offset upon default. At December 31, 2019 and 2018, the Company posted as collateral marketable securities with fair values of $462.4 million and $461.3 million, respectively, and, in turn, accepted as collateral marketable securities with fair values of $457.5 million and $457.0 million, respectively. As of December 31, 2019 (in millions) Gross Gross Net Total resale agreements $ 450.0 $ (450.0) $ — Total repurchase agreements $ 450.0 $ (450.0) $ — As of December 31, 2018 (in millions) Gross Gross Net Total resale agreements $ 450.0 $ (450.0) $ — Total repurchase agreements $ 450.0 $ (450.0) $ —

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2019
Segment Reporting [Abstract]
Segment Information	NOTE 24 – Segment Information Public companies are required to report (i) certain financial and descriptive information about “reportable operating segments,” as defined, and (ii) certain enterprise-wide financial information about products and services, geographic areas and major customers. Operating segment information is reported using a “management approach” that is based on the way management organizes the segments for purposes of making operating decisions and assessing performance. People’s United’s operations are divided into three primary operating segments that represent its core businesses: Commercial Banking; Retail Banking; and Wealth Management. In addition, the Treasury area manages People’s United’s securities portfolio, short-term investments, brokered deposits, wholesale borrowings and the funding center. The Company’s operating segments have been aggregated into two reportable segments: Commercial Banking and Retail Banking. These reportable segments have been identified and organized based on the nature of the underlying products and services applicable to each segment, the type of customers to whom those products and services are offered and the distribution channel through which those products and services are made available. With respect to the Company’s traditional wealth management activities, this presentation results in the allocation of the Company’s insurance business and certain trust activities to the Commercial Banking segment, and the allocation of the Company’s brokerage business and certain other trust activities to the Retail Banking segment. Commercial Banking consists principally of commercial real estate lending, commercial and industrial lending, and commercial deposit gathering activities. This segment also includes equipment financing operations, as well as cash management, correspondent banking, municipal banking, institutional trust services, corporate trust, commercial insurance services provided by PUIA and private banking. Retail Banking includes, as its principal business lines, consumer lending (including residential mortgage and home equity lending) and consumer deposit gathering activities. This segment also includes brokerage, financial advisory services, investment management services and life insurance provided by PSI, investment advisory services and financial management and planning services provided by PUA and non-institutional trust services. People’s United’s segment disclosure is based on an internal profitability reporting system, which generates information by operating segment based on a series of management estimates and allocations regarding funds transfer pricing (“FTP”), the provision for loan losses, non-interest expense and income taxes. These estimates and allocations, some of which are subjective in nature, are subject to periodic review and refinement. Any changes in estimates and allocations that may affect the reported results of any segment will not affect the consolidated financial position or results of operations of People’s United as a whole. FTP, which is used in the calculation of each operating segment’s net interest income, measures the value of funds used in and provided by an operating segment. The difference between the interest income on earning assets and the interest expense on funding liabilities, and the corresponding FTP charge for interest income or credit for interest expense, results in net spread income. For fixed-term assets and liabilities, the FTP rate is assigned at the time the asset or liability is originated by reference to the Company’s FTP yield curve, which is updated daily. For non-maturity-term assets and liabilities, the FTP rate is determined based upon the underlying characteristics, or behavior, of each particular product and results in the use of a historical rolling average FTP rate determined over a period that is most representative of the average life of the particular asset or liability. While the Company’s FTP methodology serves to remove IRR from the operating segments and better facilitate pricing decisions, thereby allowing management to assess the longer-term profitability of an operating segment more effectively, it may, in sustained periods of low and/or high interest rates, result in a measure of operating segment net interest income that is not reflective of current interest rates. A five-year rolling average net charge-off rate is used as the basis for the provision for loan losses for the respective operating segment in order to present a level of portfolio credit cost that is representative of the Company’s historical experience, without presenting the potential volatility from year-to-year changes in credit conditions. While this method of allocation allows management to assess the longer-term profitability of an operating segment more effectively, it may result in a measure of an operating segment’s provision for loan losses that does not reflect actual incurred losses for the periods presented. People’s United allocates a majority of non-interest expenses to each operating segment using a full-absorption costing process (i.e. all expenses are fully-allocated to the segments). Direct and indirect costs are analyzed and pooled by process and assigned to the appropriate operating segment and corporate overhead costs are allocated to the operating segments. Income tax expense is allocated to each operating segment using a constant rate, based on an estimate of the consolidated effective income tax rate for the year. Average total assets and average total liabilities are presented for each reportable segment due to management’s reliance, in part, on such average balances for purposes of assessing segment performance. Average total assets of each reportable segment include allocated goodwill and intangible assets, both of which are reviewed for impairment at least annually. The "Other" category includes the residual financial impact from the allocation of revenues and expenses (including the provision for loan losses) and certain revenues and expenses not attributable to a particular segment; assets and liabilities not attributable to a particular segment; reversal of the FTE adjustment since net interest income for each segment is presented on an FTE basis; and the FTP impact from excess capital. The "Other" category also includes (i) gains of $7.6 million, net of expenses, resulting from the sale of eight branches in central Maine and $3.3 million on a sale-leaseback transaction, both for the year ended December 31, 2019, and $10.0 million of security losses in each of the years ended December 31, 2018 and 2017 incurred in response to tax reform-related benefits recognized in each period (all included in non-interest income); and (ii) merger-related expenses totaling $49.1 million, $11.4 million and $30.6 million for the years ended December 31, 2019, 2018 and 2017, respectively, and a $16.5 million charge for the year ended December 31, 2019 associated with the complete write-down of an acquisition-related intangible asset stemming from the liquidation of the Company's public mutual funds (all included in non-interest expense). The increases in average total assets and average total liabilities in 2019 compared to 2018 primarily reflect the recognition of ROU assets and corresponding operating lease liabilities upon adoption of the FASB leasing standard on January 1, 2019 (see Notes 1 and 6 to the Consolidated Financial Statements for a further discussion regarding the accounting for leases). The following tables provide selected financial information for People’s United’s reportable segments: Year ended December 31, 2019 (in millions) Commercial Retail Total Treasury Other Total Net interest income (loss) $ 807.1 $ 555.1 $ 1,362.2 $ 66.5 $ (16.4) $ 1,412.3 Provision for loan losses 44.1 8.9 53.0 — (24.7) 28.3 Total non-interest income 206.5 195.9 402.4 14.1 14.6 431.1 Total non-interest expense 448.7 600.2 1,048.9 13.8 100.0 1,162.7 Income (loss) before income tax 520.8 141.9 662.7 66.8 (77.1) 652.4 Income tax expense (benefit) 104.3 28.5 132.8 13.5 (14.3) 132.0 Net income (loss) $ 416.5 $ 113.4 $ 529.9 $ 53.3 $ (62.8) $ 520.4 Average total assets $ 29,746.8 $ 12,560.9 $ 42,307.7 $ 7,882.3 $ 1,468.0 $ 51,658.0 Average total liabilities 11,490.2 23,397.7 34,887.9 9,011.9 686.9 44,586.7 Year ended December 31, 2018 (in millions) Commercial Retail Total Treasury Other Total Net interest income (loss) $ 699.2 $ 467.2 $ 1,166.4 $ 93.0 $ (23.4) $ 1,236.0 Provision for loan losses 38.7 9.0 47.7 — (17.7) 30.0 Total non-interest income 177.8 186.7 364.5 8.3 (6.4) 366.4 Total non-interest expense 383.7 565.3 949.0 17.8 29.3 996.1 Income (loss) before income tax 454.6 79.6 534.2 83.5 (41.4) 576.3 Income tax expense (benefit) 85.0 14.9 99.9 15.8 (7.5) 108.2 Net income (loss) $ 369.6 $ 64.7 $ 434.3 $ 67.7 $ (33.9) $ 468.1 Average total assets $ 25,956.7 $ 10,103.3 $ 36,060.0 $ 7,955.8 $ 1,013.9 $ 45,029.7 Average total liabilities 9,305.0 20,699.1 30,004.1 8,544.3 444.1 38,992.5 Year ended December 31, 2017 (in millions) Commercial Retail Total Treasury Other Total Net interest income (loss) $ 631.0 $ 403.9 $ 1,034.9 $ 107.4 $ (41.8) $ 1,100.5 Provision for loan losses 43.7 13.4 57.1 — (31.1) 26.0 Total non-interest income 165.0 183.4 348.4 11.2 (6.7) 352.9 Total non-interest expense 357.1 547.0 904.1 15.6 40.6 960.3 Income (loss) before income tax 395.2 26.9 422.1 103.0 (58.0) 467.1 Income tax expense (benefit) 110.0 7.5 117.5 28.6 (16.2) 129.9 Net income (loss) $ 285.2 $ 19.4 $ 304.6 $ 74.4 $ (41.8) $ 337.2 Average total assets $ 24,533.9 $ 9,695.1 $ 34,229.0 $ 7,512.1 $ 840.5 $ 42,581.6 Average total liabilities 7,938.6 20,202.8 28,141.4 8,450.6 398.0 36,990.0

Parent Company Financial Inform

Parent Company Financial Information	12 Months Ended
	Dec. 31, 2019
Condensed Financial Information Disclosure [Abstract]
Parent Company Financial Information	NOTE 25 – Parent Company Financial Information Condensed financial information of People’s United (parent company only) is presented below: CONDENSED STATEMENTS OF CONDITION As of December 31 (in millions) 2019 2018 Assets: Cash at bank subsidiary $ 455.2 $ 291.6 Total cash and cash equivalents 455.2 291.6 Equity securities, at fair value 8.2 8.1 Investments in subsidiaries: Bank subsidiary 7,800.0 6,485.3 Non-bank subsidiaries 4.8 2.8 Goodwill 203.0 197.1 Due from bank subsidiary 4.6 5.5 Other assets 56.0 45.9 Total assets $ 8,531.8 $ 7,036.3 Liabilities and Stockholders’ Equity: Notes and debentures $ 579.9 $ 497.7 Other liabilities 4.7 4.7 Stockholders’ equity 7,947.2 6,533.9 Total liabilities and stockholders’ equity $ 8,531.8 $ 7,036.3 CONDENSED STATEMENTS OF INCOME Years ended December 31(in millions) 2019 2018 2017 Revenues: Interest income: Securities $ 0.4 $ 0.4 $ 1.1 Total interest income 0.4 0.4 1.1 Dividend income from bank subsidiary 457.0 342.0 292.0 Net security losses — — (1.2) Other non-interest income 1.7 2.3 16.9 Total revenues 459.1 344.7 308.8 Expenses: Interest on notes and debentures 19.2 18.7 19.0 Non-interest expense 14.1 11.4 13.9 Total expenses 33.3 30.1 32.9 Income before income tax benefit and 425.8 314.6 275.9 Income tax benefit (6.2) (5.5) (5.7) Income before subsidiaries undistributed income 432.0 320.1 281.6 Subsidiaries undistributed income 88.4 148.0 55.6 Net income $ 520.4 $ 468.1 $ 337.2 CONDENSED STATEMENTS OF COMPREHENSIVE INCOME Years ended December 31 (in millions) 2019 2018 2017 Net income $ 520.4 $ 468.1 $ 337.2 Other comprehensive income (loss), net of tax: Net unrealized losses on securities available-for-sale — — (0.1) Net unrealized losses on derivatives accounted for as cash flow hedges (0.1) — — Other comprehensive income (loss) of bank subsidiary 90.0 (37.8) 13.4 Total other comprehensive income (loss), net of tax 89.9 (37.8) 13.3 Total comprehensive income $ 610.3 $ 430.3 $ 350.5 CONDENSED STATEMENTS OF CASH FLOWS Years ended December 31 (in millions) 2019 2018 2017 Cash Flows from Operating Activities: Net income $ 520.4 $ 468.1 $ 337.2 Adjustments to reconcile net income to net cash provided Subsidiaries undistributed income (88.4) (148.0) (55.6) Net security losses — — 1.2 Net change in other assets and other liabilities (0.7) 23.1 20.1 Net cash provided by operating activities 431.3 343.2 302.9 Cash Flows from Investing Activities: Proceeds from sales of equity securities 1.6 2.3 — Proceeds from sales of debt securities available-for-sale — — 75.6 Increase in investment in bank subsidiary — (200.0) — Net cash provided by (used in) investing activities 1.6 (197.7) 75.6 Cash Flows from Financing Activities: Repayment of notes and debentures — — (125.0) Cash dividends paid on common stock (274.8) (243.8) (227.9) Cash dividends paid on preferred stock (14.1) (14.1) (14.1) Common stock repurchases (4.5) (2.5) (3.4) Proceeds from stock options exercised 24.1 27.9 61.8 Net cash used in financing activities (269.3) (232.5) (308.6) Net increase (decrease) in cash and cash equivalents 163.6 (87.0) 69.9 Cash and cash equivalents at beginning of year 291.6 378.6 308.7 Cash and cash equivalents at end of year $ 455.2 $ 291.6 $ 378.6

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2019
Subsequent Events [Abstract]
Subsequent Events	NOTE 26 – Subsequent Events Repurchase of Common Stock In June 2019, the Company’s Board of Directors authorized the repurchase of up to 20.0 million shares of People's United’s outstanding common stock. Such shares may be repurchased, either directly or through agents, in the open market at prices and terms satisfactory to management. In the fourth quarter of 2019, the Company repurchased 0.2 million shares of People's United common stock under this authorization at a total cost of $2.5 million. Through February 14, 2020, an additional 10.2 million shares of People's United common stock had been repurchased at a total cost of $161.9 million. Loans Held-for-Sale At December 31, 2019, loans held-for-sale included $333.7 million of consumer loans and $157.9 million of commercial loans previously acquired in the United Financial acquisition. All of these loans were subsequently sold, resulting in a gain, net of expenses, of approximately $15 million.

Selected Quarterly Financial Da

Selected Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Financial Data (Unaudited)	NOTE 27 – Selected Quarterly Financial Data (Unaudited) The following table presents People’s United’s quarterly financial data for 2019 and 2018: 2019 (1) 2018 (1) (dollars in millions, except First Second Third Fourth First Second Third Fourth Interest and dividend income $ 440.5 $ 472.8 $ 470.9 $ 496.9 $ 359.1 $ 375.4 $ 390.0 $ 431.8 Interest expense 107.7 124.7 122.2 114.2 63.3 74.2 83.6 99.2 Net interest income 332.8 348.1 348.7 382.7 295.8 301.2 306.4 332.6 Provision for loan losses 5.6 7.6 7.8 7.3 5.4 6.5 8.2 9.9 Net interest income 327.2 340.5 340.9 375.4 290.4 294.7 298.2 322.7 Non-interest income 94.6 106.3 106.0 124.2 90.4 94.9 92.3 88.7 Non-interest expense 277.2 278.4 281.4 325.7 243.5 248.6 241.3 262.7 Income before income tax 144.6 168.4 165.5 173.9 137.3 141.0 149.2 148.7 Income tax expense 30.0 35.2 30.4 36.4 29.4 30.8 32.2 15.8 Net income 114.6 133.2 135.1 137.5 107.9 110.2 117.0 132.9 Preferred stock dividend 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 Net income available to $ 111.1 $ 129.7 $ 131.6 $ 134.0 $ 104.4 $ 106.7 $ 113.5 $ 129.4 Common Share Data: EPS: Basic $ 0.30 $ 0.33 $ 0.34 $ 0.31 $ 0.31 $ 0.31 $ 0.33 $ 0.35 Diluted 0.30 0.33 0.33 0.31 0.30 0.31 0.33 0.35 Common dividends paid 65.2 69.8 69.9 69.9 58.8 59.9 60.0 65.1 Dividends paid per 0.1750 0.1775 0.1775 0.1775 0.1725 0.1750 0.1750 0.1750 Common dividend payout ratio 58.6 % 53.8 % 53.1 % 52.2 % 56.3 % 56.2 % 52.9 % 50.3 % Stock price: High $ 18.03 $ 17.66 $ 17.10 $ 17.22 $ 20.26 $ 19.37 $ 19.00 $ 17.46 Low 14.25 15.24 13.81 14.73 18.18 18.00 16.95 13.66 Weighted average common shares Basic 370.72 391.27 391.66 421.85 339.76 340.64 341.43 370.22 Diluted 374.09 394.57 394.45 424.98 344.00 344.47 345.04 372.83 (1) The sum of the quarterly amounts for certain line items may not equal the full-year amounts due to rounding.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Basis of Financial Statement Presentation	Basis of Financial Statement Presentation The accompanying consolidated financial statements have been prepared in conformity with U.S. generally accepted accounting principles (“GAAP”) and include the accounts of People’s United and its subsidiaries. All significant intercompany transactions and balances are eliminated in consolidation. In preparing the consolidated financial statements, management is required to make significant estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses. Actual results could differ from management’s current estimates, as a result of changing conditions and future events. Several accounting estimates are particularly critical and are susceptible to significant near-term change, including the allowance for loan losses and asset impairment judgments, such as the recoverability of goodwill and other intangible assets. These accounting estimates, which are included in the discussion below, are reviewed with the Audit Committee of the Board of Directors. The judgments used by management in applying critical accounting policies may be affected by economic conditions, which may result in changes to future financial results. For example, subsequent evaluations of the loan portfolio, in light of the factors then prevailing, may result in significant changes in the allowance for loan losses in future periods, and the inability to collect outstanding principal may result in increased loan losses.
Cash Equivalents	For purposes of the Consolidated Statements of Cash Flows, cash equivalents include highly-liquid instruments, such as: (i) interest-bearing deposits at the Federal Reserve Bank of New York (the “FRB-NY”); (ii) government-sponsored enterprise (“GSE”) debt securities with an original maturity of three months or less (determined as of the date of purchase); (iii) federal funds sold; (iv) commercial paper; and (v) money market mutual funds. These instruments are reported as short-term investments in the Consolidated Statements of Condition at cost or amortized cost, which approximates fair value. GSE debt securities classified as cash equivalents are held to maturity and carry the implicit backing of the U.S. government, but are not direct obligations of the U.S. government.
Securities	Securities Marketable debt securities (other than those reported as short-term investments) are classified as either trading debt securities, held-to-maturity debt securities or available-for-sale debt securities. Management determines the classification of a security at the time of its purchase and reevaluates such classification at each balance sheet date. Debt securities purchased for sale in the near term as well as those securities held by PSI (in accordance with the requirements for a broker-dealer) are classified as trading debt securities and reported at fair value with gains and losses reported in non-interest income. Debt securities for which People’s United has the intent and ability to hold to maturity are classified as held-to-maturity securities and reported at amortized cost. All other debt securities are classified as available-for-sale and reported at fair value with unrealized gains and losses reported on an after-tax basis in stockholders’ equity as a component of accumulated other comprehensive income (loss) (“AOCL”). Premiums (discounts) are amortized (accreted) to interest income for debt securities, using the interest method over the remaining period to contractual maturity, adjusted for the effect of actual prepayments in the case of mortgage-backed and collateralized mortgage obligation (“CMO”) securities. Security transactions are recorded on the trade date. Realized gains and losses are determined using the specific identification method and reported in non-interest income. Debt securities transferred from available-for-sale to held-to-maturity are recorded at fair value at the date of transfer. The unrealized pre-tax gain or loss resulting from the difference between fair value and amortized cost at the transfer date becomes part of the new amortized cost basis of the securities and remains in AOCL. Such unrealized gains or losses are amortized to interest income as an adjustment to yield over the remaining life of the securities, offset by the amortization (accretion) of the premium (discount) resulting from the transfer at fair value, with no effect to net income. Management conducts a periodic review and evaluation of the debt securities portfolio to determine if the decline in fair value of any security is deemed to be other-than-temporary. Other-than-temporary impairment losses are recognized on debt securities when: (i) People’s United has an intention to sell the security; (ii) it is more likely than not that People’s United will be required to sell the security prior to recovery; or (iii) People’s United does not expect to recover the entire amortized cost basis of the security. Other-than-temporary impairment losses on debt securities are reflected in earnings as realized losses to the extent the impairment is related to credit losses of the issuer. The amount of the impairment related to other factors is recognized in other comprehensive income. Management has the ability and intent to hold the securities classified as held-to-maturity until they mature, at which time People’s United expects to receive full value for the securities. Both Federal Home Loan Bank (“FHLB”) stock and FRB-NY stock are non-marketable equity securities and are, therefore, reported at their respective costs, which equals par value (the amount at which shares have been redeemed in the past). These investments are periodically evaluated for impairment based on, among other things, the capital adequacy of the applicable FHLB or the FRB-NY and their overall financial condition. Equity securities are reported at fair value with gains and losses reported in non-interest income.
Securities Resale and Securities Repurchase Agreements	Securities Resale and Securities Repurchase Agreements In securities resale agreements, a counterparty transfers securities to People’s United (as transferee) and People’s United agrees to resell the same securities to the counterparty at a fixed price in the future. In securities repurchase agreements, which include both retail arrangements with customers and wholesale arrangements with other counterparties, People’s United (as transferor) transfers securities to a counterparty and agrees to repurchase the same securities from the counterparty at a fixed price in the future. People’s United accounts for securities resale agreements as secured lending transactions and securities repurchase agreements as secured borrowings since the transferor maintains effective control over the transferred securities and the transfer meets the other criteria for such accounting. The securities are pledged by the transferor as collateral and the transferee has the right by contract to repledge that collateral provided the same collateral is returned to the transferor upon maturity of the underlying agreement. The fair value of the pledged collateral approximates the recorded amount of the secured loan or borrowing. Decreases in the fair value of the transferred securities below an established threshold require the transferor to provide additional collateral.
Loans Held-for-Sale	Loans Held-for-Sale Loans held-for-sale are reported at the lower of cost or fair value in the aggregate with any adjustment for net unrealized losses reported in non-interest income. Management identifies and designates as loans held-for-sale certain newly-originated adjustable-rate and fixed-rate residential mortgage loans that meet secondary market requirements, as these loans are originated with the intent to sell. From time to time, management may also identify and designate certain loans previously held-for-investment as held-for-sale. Such loans are transferred to loans held-for-sale and adjusted to the lower of cost or fair value with the resulting unrealized loss, if any, reported in non-interest income.
Loans	Loans Loans acquired in connection with business combinations are referred to as ‘acquired’ loans as a result of the manner in which they are accounted for (see further discussion under ‘Acquired Loans’ below). All other loans are referred to as ‘originated’ loans. Basis of Accounting Originated loans are reported at amortized cost less the allowance for loan losses. Interest on loans is accrued to income monthly based on outstanding principal balances. Loan origination fees and certain direct loan origination costs are deferred, and the net fee or cost is recognized in interest income as an adjustment of yield. Depending on the loan portfolio, amounts are amortized or accreted using the level yield method over either the actual life or the estimated average life of the loan.
Non-accrual Loans	Non-accrual Loans A loan is generally considered “non-performing” when it is placed on non-accrual status. A loan is generally placed on non-accrual status when it becomes 90 days past due as to interest or principal payments. Past due status is based on the contractual payment terms of the loan. A loan may be placed on non-accrual status before it reaches 90 days past due if such loan has been identified as presenting uncertainty with respect to the collectability of interest and principal. A loan past due 90 days or more may remain on accruing status if such loan is both well secured and in the process of collection.
Impaired Loans	Impaired Loans A loan is considered impaired when, based on current information and events, it is probable that the Company will be unable to collect all amounts due in accordance with the original contractual terms of the loan agreement, including scheduled principal and interest payments. Impaired loans also include certain loans whose terms have been modified in such a way that they are considered troubled debt restructurings (“TDRs”). Loans are considered TDRs if the borrower is experiencing financial difficulty and is afforded a concession by People’s United, such as, but not limited to: (i) payment deferral; (ii) a reduction of the stated interest rate for the remaining contractual life of the loan; (iii) an extension of the loan’s original contractual term at a stated interest rate lower than the current market rate for a new loan with similar risk; (iv) capitalization of interest; or (v) forgiveness of principal or interest. TDRs may either be accruing or placed on non-accrual status (and reported as non-performing loans) depending upon the loan’s specific circumstances, including the nature and extent of the related modifications. TDRs on non-accrual status remain classified as such until the loan qualifies for return to accrual status. Loans qualify for return to accrual status once they have demonstrated performance with the restructured terms of the loan agreement for a minimum of six months in the case of a commercial loan or, in the case of a retail loan, when the loan is less than 90 days past due. Loans may continue to be reported as TDRs after they are returned to accrual status. In accordance with regulatory guidance, residential mortgage and home equity loans restructured in connection with the borrower’s bankruptcy and meeting certain criteria are also required to be classified as TDRs, included in non-performing loans and written down to the estimated collateral value, regardless of delinquency status. Acquired loans that are modified are not considered for TDR classification provided they are evaluated for impairment on a pool basis (see further discussion under ‘Acquired Loans’ below). Impairment is evaluated on a collective basis for pools of retail loans possessing similar risk and loss characteristics and on an individual basis for other loans. If a loan is deemed to be impaired, a specific valuation allowance is allocated, if necessary, so that the loan is reported (net of the allowance) at the present value of expected future cash flows discounted at the loan’s original effective interest rate or at the fair value of the collateral less cost to sell if repayment is expected solely from the collateral. Interest payments on impaired non-accrual loans are typically applied to principal unless collectability of the principal amount is reasonably assured, in which case interest is recognized on a cash basis. Impaired loans, or portions thereof, are charged off when deemed uncollectible. Acquired Loans Loans acquired in a business combination are initially recorded at fair value with no carryover of an acquired entity’s previously established allowance for loan losses. Fair value of the loans is determined using market participant assumptions in estimating the amount and timing of both principal and interest cash flows expected to be collected, as adjusted for an estimate of future credit losses and prepayments, and then applying a market-based discount rate to those cash flows. Acquired loans are evaluated upon acquisition and classified as either purchased performing or purchased credit impaired (“PCI”). For purchased performing loans, any premium or discount, representing the difference between the fair value and the outstanding principal balance of the loans, is recognized (using the level yield method) as an adjustment to interest income over the remaining period to contractual maturity or until the loan is repaid in full or sold. Subsequent to the acquisition date, the method utilized to estimate the required allowance for loan losses for these loans is similar to that for originated loans. However, a provision for loan losses is only recorded when the required allowance for loan losses exceeds any remaining purchase discount at the loan level. PCI loans represent those acquired loans with specific evidence of deterioration in credit quality since origination and for which it is probable that, as of the acquisition date, all contractually required principal and interest payments will not be collected . Such loans are generally accounted for on a pool basis, with pools formed based on the loans’ common risk characteristics, such as loan collateral type and accrual status. Each pool is accounted for as a single asset with a single composite interest rate and an aggregate expectation of cash flows. Under the accounting model for PCI loans, the excess of cash flows expected to be collected over the carrying amount of the loans, referred to as the “accretable yield”, is accreted into interest income over the life of the loans in each pool using the level yield method. Accordingly, PCI loans are not subject to classification as non-accrual in the same manner as other loans. Rather, PCI loans are considered to be accruing loans because their interest income relates to the accretable yield recognized at the pool level and not to contractual interest payments at the loan level. The difference between contractually required principal and interest payments and the cash flows expected to be collected, referred to as the “nonaccretable difference”, includes estimates of both the impact of prepayments and future credit losses expected to be incurred over the life of the loans in each pool. As such, charge-offs on PCI loans are first applied to the nonaccretable difference and then to any allowance for loan losses recognized subsequent to acquisition. Subsequent to acquisition, actual cash collections are monitored relative to management’s expectations and revised cash flow forecasts are prepared, as warranted. These revised forecasts involve updates, as necessary, of the key assumptions and estimates used in the initial estimate of fair value. Generally speaking, expected cash flows are affected by: • Changes in the expected principal and interest payments over the estimated life — Updates to changes in expected cash flows are driven by the credit outlook and actions taken with borrowers. Changes in expected future cash flows resulting from loan modifications are included in the assessment of expected cash flows; • Changes in prepayment assumptions — Prepayments affect the estimated life of the loans which may change the amount of interest income, and possibly principal, expected to be collected; and • Changes in interest rate indices for variable rate loans — Expected future cash flows are based, as applicable, on the variable rates in effect at the time of the assessment of expected cash flows. A decrease in expected cash flows in subsequent periods may indicate that the loan pool is impaired, which would require the establishment of an allowance for loan losses by a charge to the provision for loan losses. An increase in expected cash flows in subsequent periods serves, first, to reduce any previously established allowance for loan losses by the increase in the present value of cash flows expected to be collected, and results in a recalculation of the amount of accretable yield for the loan pool. The adjustment of accretable yield due to an increase in expected cash flows is accounted for as a change in estimate. The additional cash flows expected to be collected are reclassified from the nonaccretable difference to the accretable yield, and the amount of periodic accretion is adjusted accordingly over the remaining life of the loans in the pool. PCI loans may be resolved either through receipt of payment (in full or in part) from the borrower, the sale of the loan to a third party or foreclosure of the collateral. In the event of a sale of the loan, a gain or loss on sale is recognized and reported within non-interest income based on the difference between the sales proceeds and the carrying amount of the loan. In other cases, individual loans are removed from the pool based on comparing the amount received from its resolution (fair value of the underlying collateral less costs to sell in the case of a foreclosure) with its outstanding balance. Any difference between these amounts is absorbed by the nonaccretable difference established for the entire pool. For loans resolved by payment in full, there is no adjustment of the nonaccretable difference since there is no difference between the amount received at resolution and the outstanding balance of the loan. In these cases, the remaining accretable yield balance is unaffected and any material change in remaining effective yield caused by the removal of the loan from the pool is addressed in connection with the subsequent cash flow re-assessment for the pool. PCI loans subject to modification are not removed from the pool even if those loans would otherwise be deemed TDRs as the pool, and not the individual loan, represents the unit of account. Allowance and Provision for Loan Losses Originated Portfolio The allowance for loan losses is established through provisions for loan losses charged to income. Losses on loans, including impaired loans, are charged to the allowance for loan losses when all or a portion of a loan is deemed to be uncollectible. Recoveries of loans previously charged off are credited to the allowance for loan losses when realized. People’s United maintains the allowance for loan losses at a level that is deemed to be appropriate to absorb probable losses inherent in the respective loan portfolios, based on a quarterly evaluation of a variety of factors. These factors include, but are not limited to: (i) People’s United’s historical loan loss experience and recent trends in that experience; (ii) risk ratings assigned by lending personnel to commercial real estate loans, commercial and industrial loans, and equipment financing loans, and the results of ongoing reviews of those ratings by People’s United’s independent loan review function; (iii) an evaluation of delinquent and non-performing loans and related collateral values; (iv) the probability of loss in view of geographic and industry concentrations and other portfolio risk characteristics; (v) the present financial condition of borrowers; and (vi) current economic conditions. The Company’s allowance for loan losses consists of three elements: (i) an allowance for commercial loans collectively evaluated for impairment; (ii) an allowance for retail loans collectively evaluated for impairment; and (iii) a specific allowance for loans individually evaluated for impairment, including loans classified as TDRs. Commercial Loans Collectively Evaluated for Impairment. The Company establishes a loan loss allowance for its commercial loans collectively evaluated for impairment using a methodology that incorporates (i) the probability of default for a given loan risk rating and (ii) historical loss-given-default data, both derived using appropriate look-back periods and loss emergence periods. In accordance with the Company’s loan risk rating system, each commercial loan is assigned a risk rating (using a nine-grade scale) by the originating loan officer, credit management, internal loan review or loan committee. Loans rated “One” represent those loans least likely to default while loans rated “Nine” represent a loss. The probability of loans defaulting for each risk rating, referred to as default factors, are estimated based on the historical pattern of loans migrating from one risk rating to another and to default status over time as well as the length of time that it takes losses to emerge. Estimated loan default factors, which are updated annually (or more frequently, if necessary), are multiplied by loan balances within each risk-rating category and again multiplied by a historical loss-given-default estimate for each loan type to determine an appropriate level of allowance by loan type. The historical loss-given-default estimates are also updated annually (or more frequently, if necessary) based on actual charge-off experience. This approach is applied to the commercial and industrial, commercial real estate and equipment financing components of the loan portfolio. In establishing the allowance for loan losses for commercial loans collectively evaluated for impairment, the Company also gives consideration to certain qualitative factors, including the macroeconomic environment and any potential imprecision inherent in its loan loss model that may result from having limited historical loan loss data which, in turn, may result in inaccurate probability of default and loss-given-default estimates. In this manner, historical portfolio experience, as described above, is not adjusted and the allowance for loan losses always includes a component attributable to qualitative factors, the degree of which may change from period to period as such qualitative factors indicate improving or worsening trends. The Company evaluates the qualitative factors on a quarterly basis in order to conclude that they continue to be appropriate. There were no significant changes in our approach to determining the qualitative component of the related allowance for loan losses during 2019. Retail Loans Collectively Evaluated for Impairment. Pools of retail loans possessing similar risk and loss characteristics are collectively evaluated for impairment. These loan pools include residential mortgage, home equity and other consumer loans that are not assigned individual loan risk ratings. Rather, the assessment of these portfolios, and the establishment of the related allowance for loan losses, is based upon a consideration of (i) historical portfolio loss experience over an appropriate look-back period and loss emergence period and (ii) certain qualitative factors. The qualitative component of the allowance for loan losses for retail loans collectively evaluated for impairment is intended to incorporate risks inherent in the portfolio, economic uncertainties, regulatory requirements and other subjective factors such as changes in underwriting standards. Accordingly, consideration is given to: (i) present and forecasted economic conditions, including unemployment rates; (ii) changes in industry trends, including the impact of new regulations, (iii) trends in property values; (iv) broader portfolio indicators, including delinquencies, non-performing loans, portfolio concentrations, and trends in the volume and terms of loans; and (v) portfolio-specific risk characteristics. Portfolio-specific risk characteristics considered include: (i) collateral values/loan-to-value ("LTV") ratios (above and below 70%); (ii) borrower credit scores under the FICO scoring system (above and below a score of 680); and (iii) other relevant portfolio risk elements such as income verification at the time of underwriting (stated income vs. non-stated income) and the property’s intended use (owner-occupied, non-owner occupied, second home, etc.), the combination of which results in a loan being classified as either “High”, “Moderate” or “Low” risk. These risk classifications are reviewed quarterly to ensure that changes within the portfolio, as well as economic indicators and industry developments, have been appropriately considered in establishing the related allowance for loan losses. In establishing the allowance for loan losses for retail loans collectively evaluated for impairment, the amount reflecting the Company’s consideration of qualitative factors is added to the amount attributable to historical portfolio loss experience. In this manner, historical charge-off data (whether periods or amounts) is not adjusted and the allowance for loan losses always includes a component attributable to qualitative factors, the degree of which may change from period to period as such qualitative factors indicate improving or worsening trends. The Company evaluates the qualitative factors on a quarterly basis in order to conclude that they continue to be appropriate. There were no significant changes in our approach to determining the qualitative component of the related allowance for loan losses during 2019. Individually Impaired Loans. The allowance for loan losses also includes specific allowances for individually impaired loans. Generally, the Company’s impaired loans consist of (i) classified commercial loans in excess of $1 million that have been placed on non-accrual status and (ii) loans classified as TDRs. Individually impaired loans are measured based upon observable market prices; the present value of expected future cash flows discounted at the loan’s original effective interest rate; or, in the case of collateral dependent loans, fair value of the collateral (based on appraisals and other market information) less cost to sell. If the recorded investment in a loan exceeds the amount measured as described in the preceding sentence, a specific allowance for loan losses would be established as a component of the overall allowance for loan losses or, in the case of a collateral dependent loan, a charge-off would be recorded for the difference between the loan’s recorded investment and management’s estimate of the fair value of the collateral (less cost to sell). It would be rare for the Company to identify a loan that meets the criteria stated above and requires a specific allowance or a charge-off and not deem it impaired solely as a result of the existence of a guarantee. People’s United performs an analysis of its impaired loans, including collateral dependent impaired loans, on a quarterly basis. Individually impaired collateral dependent loans are measured based upon the appraised value of the underlying collateral and other market information. Generally, the Company’s policy is to obtain updated appraisals for commercial collateral dependent loans when the loan is downgraded to a risk rating of “substandard” or “doubtful”, and the most recent appraisal is more than 12 months old or a determination has been made that the property has experienced a significant decline in value. Appraisals are prepared by independent, licensed third-party appraisers and are subject to review by the Company’s internal commercial appraisal department or external appraisers contracted by the commercial appraisal department. The conclusions of the external appraisal review are reviewed by the Company’s Chief Commercial Appraiser prior to acceptance. The Company’s policy with respect to impaired loans secured by residential real estate is to receive updated estimates of property values upon the loan being classified as non-performing (typically upon becoming 90 days past due). In determining the allowance for loan losses, People’s United gives appropriate consideration to the age of appraisals through its regular evaluation of other relevant qualitative and quantitative information. Specifically, between scheduled appraisals, property values are monitored within the commercial portfolio by reference to current originations of collateral dependent loans and the related appraisals obtained during underwriting as well as by reference to recent trends in commercial property sales as published by leading industry sources. Property values are monitored within the residential mortgage and home equity portfolios by reference to available market indicators, including real estate price indices within the Company’s primary lending areas. In most situations where a guarantee exists, the guarantee arrangement is not a specific factor in the assessment of the related allowance for loan losses. However, the assessment of a guarantor’s credit strength is reflected in the Company’s internal loan risk ratings which, in turn, are an important factor in its allowance for loan loss methodology for loans within the commercial and industrial, and commercial real estate portfolios. People’s United did not change its methodologies with respect to determining the allowance for loan losses during 2019. As part of its ongoing assessment of the allowance for loan losses, People’s United regularly makes refinements to certain underlying assumptions used in its methodologies. However, such refinements did not have a material impact on the allowance for loan losses or the provision for loan losses as of or for the year ended December 31, 2019. While People’s United seeks to use the best available information to make these determinations, future adjustments to the allowance for loan losses may be necessary based on changes in economic conditions, results of regulatory examinations, further information obtained regarding known problem loans, the identification of additional problem loans and other factors. Acquired Portfolio Acquired loans are evaluated upon acquisition and classified as either purchased performing or PCI, which represents those acquired loans with specific evidence of deterioration in credit quality since origination and for which it is probable that, as of the acquisition date, all contractually required principal and interest payments will not be collected. PCI loans are generally accounted for on a pool basis, with pools formed based on the loans’ common risk characteristics, such as loan collateral type and accrual status. Each pool is accounted for as a single asset with a single composite interest rate and an aggregate expectation of cash flows. For purchased performing loans, the required allowance for loan losses is determined in a manner similar to that for originated loans with a provision for loan losses only recorded when the required allowance for loan losses exceeds any remaining purchase discount at the loan level. For PCI loans, the difference between contractually required principal and interest payments at the acquisition date and the undiscounted cash flows expected to be collected at the acquisition date is referred to as the “nonaccretable difference”, which includes an estimate of future credit losses expected to be incurred over the life of the loans in each pool. A decrease in the expected cash flows in subsequent periods requires the establishment of an allowance for loan losses at that time. Loan Charge-Offs The Company’s charge-off policies, which comply with standards established by banking regulators, are consistently applied from period to period. Charge-offs are recorded on a monthly basis. Partially charged-off loans continue to be evaluated on a monthly basis and additional charge-offs or loan loss provisions may be recorded on the remaining loan balance based on the same criteria. For unsecured consumer loans, charge-offs are generally recorded when the loan is deemed to be uncollectible or 120 days past due, whichever occurs first. For consumer loans secured by real estate, including residential mortgage loans, charge-offs are generally recorded when the loan is deemed to be uncollectible or 180 days past due, whichever occurs first, unless it can be clearly demonstrated that repayment will occur regardless of the delinquency status. Factors that demonstrate an ability to repay may include: (i) a loan that is secured by adequate collateral and is in the process of collection; (ii) a loan supported by a valid guarantee or insurance; or (iii) a loan supported by a valid claim against a solvent estate. For commercial loans, a charge-off is recorded when the Company determines that it will not collect all amounts contractually due based on the fair value of the collateral less cost to sell, or the present value of expected future cash flows.
Revenue from Contracts with Customers	Revenue from Contracts with Customers The Company earns revenue from a variety of sources. For revenue streams other than (i) net interest income and (ii) other revenues associated with financial assets and financial liabilities, including loans, leases, securities and derivatives, the Company generally applies the following steps with respect to revenue recognition: (i) identify the contract; (ii) identify the performance obligation; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligation; and (v) recognize revenue when the performance obligation is satisfied. The Company’s contracts with customers are generally short-term in nature, typically due within one year or less, or cancellable by the Company or the customer upon a short notice period. Performance obligations for customer contracts are generally satisfied at a single point in time, typically when the transaction is complete, or over time. For performance obligations satisfied over time, the value of the products/services transferred to the customer are evaluated to determine when, and to what degree, performance obligations have been satisfied. Payments from customers are typically received, and revenue recognized, concurrent with the satisfaction of our performance obligations. In most cases, this occurs within a single financial reporting period. For payments received in advance of the satisfaction of our performance obligations, revenue recognition is deferred until such time the performance obligations have been satisfied. In cases where a payment has not been received despite satisfaction of our performance obligations, an estimate of the amount due is accrued in the period our performance obligations have been satisfied. For contracts with variable components, amounts for which collection is probable are accrued. The following summarizes the Company’s performance obligations for the more significant recurring revenue streams included in non-interest income: Service charges and fees on deposit accounts — Service charges and fees on deposit accounts consist of monthly account maintenance and other related fees (bank service charges) as well as cash management fees, which are earned for services related to payment processing, overdrafts, non-sufficient funds and other deposit account activity. The Company’s performance obligation for monthly service fees is generally satisfied, and the related revenue recognized, over the period in which the service is provided. Other deposit account related fees, including overdraft charges and cash management fees, are largely transactional-based, and therefore, the Company’s performance obligation is satisfied, and related revenue recognized, at a point in time. Payment for service charges on deposit accounts is primarily received immediately or in the following month through a direct charge to customers’ accounts. Card-based and other non-deposit fees — Card-based and other non-deposit fees are comprised, primarily, of debit and credit card income and ATM fees as well as certain commercial banking lending fees. Debit and credit card income is primarily comprised of interchange fees earned whenever the Company’s debit and credit cards are processed through card payment networks. ATM fees and commercial banking lending fees are largely transactional-based and, therefore, the Company’s performance obligation is satisfied, and related revenue recognized, at a point in time. Payment is typically received immediately or in the following month. Investment management fees — Investment management income is primarily comprised of fees earned from the management and administration of trusts and other customer assets. The Company’s performance obligation is generally satisfied over time and the resulting fees are recognized monthly, based upon the month-end market value of the assets under management and the applicable fee rate. Payment is generally received a few days after month end through a direct charge to customers’ accounts. The Company’s performance obligation for these transactional-based services is generally satisfied, and the related revenue recognized, at a point in time (i.e. as incurred). Payment is received shortly after services are rendered. Insurance commissions and fees — The Company’s insurance revenue, which represents commissions earned for performing broker- and agency-related services, has two distinct performance obligations. The first performance obligation is the selling of the policy as an agent for the carrier. This performance obligation is satisfied upon binding of the policy. The second performance obligation is the ongoing servicing of the policy which is satisfied over the life of the policy. For employee benefits, the payment is typically received monthly. For property and casualty, payments can vary but are typically received at, or in advance of, the policy period. Brokerage commissions and fees — Brokerage commissions and fees primarily relate to investment advisory and brokerage activities as well as the sale of mutual funds and annuities. The Company’s performance obligation for investment advisory services is generally satisfied, and the related revenue recognized, over the period in which the services are provided. Fees earned for brokerage activities, such as facilitating securities transactions, are generally recognized at the time of transaction execution. The performance obligation for mutual fund and annuity sales is satisfied upon sale of the underlying investment, and therefore, the related revenue is primarily recognized at the time of sale. Payment for these services is typically received immediately or in advance of the service. The revenue streams noted above represent approximately $288 million (or 67%) of total non-interest income for the year ended December 31, 2019, and approximately $270 million (or 74%) for the year ended December 31, 2018. Of these amounts, approximately 40% in both 2019 and 2018 is allocated to the Commercial Banking operating segment and approximately 30% in both 2019 and 2018 is allocated to each of the Retail Banking and Wealth Management operating segments. The Company generally acts in a principal capacity, on its own behalf, in the majority of its contracts with customers. In such transactions, revenue and the related costs to provide our services are recognized on a gross basis in the financial statements. In some cases, the Company may act in an agent capacity, deriving revenue by assisting other entities in transactions with our customers. In such transactions, revenue and the related costs to provide our services are recognized on a net basis in the financial statements. The extent of the Company’s activities for which it acts as an agent (and for which the related revenue and expense has been presented on a net basis) is immaterial.
Bank-Owned Life Insurance	Bank-Owned Life Insurance Bank-owned life insurance (“BOLI”) represents the cash surrender value of life insurance policies purchased on the lives of certain key executives and former key executives. BOLI funds are generally invested in separate accounts and are supported by a stable wrap agreement to fully insulate the underlying investments against changes in fair value. Increases in the cash surrender value of these policies and death benefits in excess of the related invested premiums are included in non-interest income in the Consolidated Statements of Income. The Company’s BOLI policies have been underwritten by highly-rated third party insurance carriers and the investments underlying these policies are deemed to be of low-to-moderate market risk.
Premises and Equipment	Premises and Equipment Premises and equipment are reported at cost less accumulated depreciation and amortization, except for land, which is reported at cost. Buildings, data processing and other equipment, computer software, furniture and fixtures are depreciated using the straight-line method over the estimated useful lives of the assets. Leasehold improvements are amortized using the straight-line method over the shorter of the remaining lease term, the estimated useful life of the improvements or 10 years. Capitalized software development costs are amortized on a straight-line basis over the estimated useful life of the software. Generally, the estimated useful lives are as follows: buildings — 40 years; data processing and other equipment — 3 to 5 years; computer software — 3 to 5 years; and furniture and fixtures — 10 years.
Goodwill and Other Acquisition-Related Intangible Assets	Goodwill and Other Acquisition-Related Intangible Assets An acquirer in a business combination is required, upon initially obtaining control of another entity, to recognize the assets, liabilities and any non-controlling interest in the acquiree at fair value as of the acquisition date. Contingent consideration, if any, is also recognized and measured at fair value on the date of acquisition. In addition, the accounting standards for business combinations require that: (i) acquisition-related transaction costs be expensed as incurred; (ii) specific requirements be met in order to accrue for a restructuring plan as part of the acquisition; (iii) certain pre-acquisition contingencies be recognized at fair value; and (iv) acquired loans be recorded at fair value as of the acquisition date without recognition of an allowance for loan losses. Intangible assets are recognized in an amount equal to the excess of the consideration transferred over the fair value of the tangible net assets acquired. “Acquisition-related intangible assets” are separately identified, recognized and amortized, where appropriate, for assets such as trade names, certain contractual agreements and the estimated values of acquired core deposits and/or customer relationships. Mutual fund management contract intangibles recognized by People’s United are deemed to have indefinite useful lives and, accordingly, are not amortized. The remaining intangible asset is recognized as goodwill. Goodwill and indefinite-lived intangible assets are not amortized but, rather, are reviewed for impairment at least annually, with impairment losses recognized as a charge to expense when they occur. Acquisition-related intangible assets other than goodwill and indefinite-lived intangible assets are amortized to expense over their estimated useful lives in a manner consistent with that in which the related benefits are expected to be realized, and are periodically reviewed by management to assess recoverability, with impairment losses recognized as a charge to expense if carrying amounts exceed fair values. The Company’s trade name intangibles are amortized on either (i) an accelerated basis over a period of approximately 20 years or (ii) a straight-line basis over 5 years. Core deposit intangibles are amortized on an accelerated basis over a period ranging from 6 to 10 years. Customer relationship intangibles are amortized on a straight-line basis over the estimated remaining average life of those relationships, which ranges from 10 to 15 years from the respective acquisition dates. Intangibles stemming from contractual agreements, such as favorable lease and non-compete agreements, are amortized on a straight-line basis over the remaining term of the respective agreements. Goodwill is evaluated for impairment at the reporting unit level. For the purpose of goodwill impairment evaluations, management has identified reporting units based upon the Company’s three operating segments: Commercial Banking; Retail Banking; and Wealth Management. The impairment evaluation is performed as of an annual date or more frequently if a triggering event indicates that impairment may have occurred. Entities have the option to first assess qualitative factors to determine whether the existence of events or circumstances leads to a determination that it is more likely than not that the fair value of a reporting unit is less than its carrying amount. If, after assessing the totality of such events or circumstances, an entity determines it is not more likely than not that the fair value of a reporting unit is less than its carrying amount, then the entity is not required to perform the quantitative impairment test as described below. The quantitative test is used to identify potential impairment, and involves comparing each reporting unit’s estimated fair value to its carrying amount, including goodwill. If the estimated fair value of a reporting unit exceeds its carrying amount, goodwill is not deemed to be impaired. Should the carrying amount of the reporting unit exceed its estimated fair value, an impairment loss shall be recognized in an amount equal to that excess, not to exceed the carrying amount of goodwill. At this time, none of the Company’s identified reporting units are at risk of failing the quantitative goodwill impairment test. The Company estimates the fair value of its reporting units based on an appropriate weighting of values based on (i) a present-value measurement technique (discounted cash flow analysis based on internal forecasts) and (ii) market-based trading and transaction multiples. The discounted cash flow analysis is based on significant assumptions and judgments including future growth rates and discount rates reflecting management’s assessment of market participant views of the risks associated with the projected cash flows of the reporting units. The market-based trading and transaction multiples are derived from the market prices of stocks of companies that are actively traded and engaged in the same or similar businesses as the Company and the respective reporting unit. The derived multiples are then applied to the reporting unit’s financial metrics to produce an indication of value. Differences in the identification of reporting units or in the selection of valuation techniques and related assumptions could result in materially different evaluations of goodwill impairment. In conducting its 2019 and 2018 goodwill impairment evaluations (as of the annual October 1 st evaluation date), People’s United elected to perform the optional qualitative assessment for all three reporting units. In 2017, People’s United elected to perform the optional qualitative assessment for both the Commercial Banking and Retail Banking reporting units and, upon doing so, concluded that performance of the quantitative impairment test was not required. The quantitative impairment test was elected for purposes of the 2017 goodwill impairment evaluation for the Wealth Management reporting unit as a result of the acquisition of Gerstein, Fisher & Associates, Inc., which occurred subsequent to performance of the Company’s 2016 impairment analysis.
Real Estate Owned	Real Estate Owned Real estate owned (“REO”) properties acquired through foreclosure or deed-in-lieu of foreclosure are recorded initially at the lower of cost or estimated fair value less costs to sell. Any write-down of the recorded investment in the related loan is charged to the allowance for loan losses upon transfer to REO. Thereafter, an allowance for REO losses is established for any further declines in the property’s value. This allowance is increased by provisions charged to income and decreased by charge-offs for realized losses. Management’s periodic evaluation of the adequacy of the allowance is based on an analysis of individual properties, as well as a general assessment of current real estate market conditions.
Income Taxes	Income Taxes Deferred taxes are recognized for the estimated future tax effects attributable to “temporary differences” and tax loss carryforwards. Temporary differences are differences between the financial statement carrying amounts and the tax bases of existing assets and liabilities. A deferred tax liability is recognized for all temporary differences that will result in future taxable income. A deferred tax asset is recognized for all temporary differences that will result in future tax deductions and for all tax loss carryforwards, subject to reduction of the asset by a valuation allowance in certain circumstances. This valuation allowance is recognized if, based on an analysis of available evidence, management determines that it is more likely than not that some portion or all of the deferred tax asset will not be realized. The valuation allowance is subject to ongoing adjustment based on changes in circumstances that affect management’s judgment about the realizability of the deferred tax asset. Deferred tax assets and liabilities are measured using the enacted tax rates expected to apply to future taxable income. The effect on deferred tax assets and liabilities of a change in tax laws or rates is recognized in income tax expense in the period that includes the enactment date of the change. Effective January 1, 2017, tax benefits attributable to deductions in excess of financial statement amounts arising from the exercise of non-statutory stock options are included as a component of income tax expense (previously credited to additional paid-in capital). Individual tax positions taken or expected to be taken on a tax return must satisfy certain criteria in order for some or all of the related tax benefits to be recognized in the financial statements. Specifically, a recognition threshold of more-likely-than-not must be met in order to recognize those tax benefits.
Earnings Per Common Share	Earnings Per Common Share Basic earnings per common share (“EPS”) excludes dilution and is computed by dividing earnings attributable to common shareholders by the weighted average number of common shares outstanding for the year. Diluted EPS reflects the potential dilution that could occur if securities or other contracts to issue common stock (such as stock options and performance shares) were exercised or converted into additional common shares that would then share in the earnings of the entity. Diluted EPS is computed by dividing earnings attributable to common shareholders by the weighted average number of common shares outstanding for the year, plus an incremental number of common-equivalent shares computed using the treasury stock method. Unvested share-based payment awards, which include the right to receive non-forfeitable dividends or dividend equivalents, are considered to participate with common shareholders in undistributed earnings for purposes of computing EPS. Companies that have such participating securities, including People’s United, are required to calculate basic and diluted EPS using the two-class method. Restricted stock awards granted by People’s United are considered participating securities. Calculations of EPS under the two-class method (i) exclude from the numerator any dividends paid or owed on participating securities and any undistributed earnings considered to be attributable to participating securities and (ii) exclude from the denominator the dilutive impact of the participating securities.
Derivative Financial Instruments and Hedging Activities	Derivative Financial Instruments and Hedging Activities People’s United uses derivative financial instruments as components of its market risk management (principally to manage interest rate risk (“IRR”)). Certain other derivatives are entered into in connection with transactions with commercial customers. Derivatives are not used for speculative purposes. All derivatives are recognized as either assets or liabilities in the Consolidated Statements of Condition, reported at fair value and presented on a gross basis. Until a derivative is settled, a favorable change in fair value results in an unrealized gain that is recognized as an asset, while an unfavorable change in fair value results in an unrealized loss that is recognized as a liability. The Company generally applies hedge accounting to its derivatives used for market risk management purposes. Hedge accounting is permitted only if specific criteria are met, including a requirement that a highly effective relationship exist between the derivative instrument and the hedged item, both at inception of the hedge and on an ongoing basis. The hedge accounting method depends upon whether the derivative instrument is classified as a fair value hedge (i.e. hedging an exposure related to a recognized asset or liability, or a firm commitment) or a cash flow hedge (i.e. hedging an exposure related to the variability of future cash flows associated with a recognized asset or liability, or a forecasted transaction). Changes in the fair value of effective fair value hedges are recognized in current earnings (with the change in fair value of the hedged asset or liability also recorded in earnings). Changes in the fair value of effective cash flow hedges are recognized in other comprehensive income (loss) until earnings are affected by the variability in cash flows of the designated hedged item. Ineffective portions of hedge results are recognized in current earnings. Changes in the fair value of derivatives for which hedge accounting is not applied are recognized in current earnings. People’s United formally documents at inception all relationships between the derivative instruments and the hedged items, as well as its risk management objectives and strategies for undertaking the hedge transactions. This process includes linking all derivatives that are designated as hedges to specific assets and liabilities, or to specific firm commitments or forecasted transactions. People’s United also formally assesses, both at inception of the hedge and on an ongoing basis, whether the derivatives that are used in hedging transactions are highly effective in offsetting changes in the fair values or cash flows of the hedged items. If it is determined that a derivative is not highly effective or has ceased to be a highly effective hedge, People’s United would discontinue hedge accounting prospectively. Gains or losses resulting from the termination of a derivative accounted for as a cash flow hedge remain in AOCL and are amortized to earnings over the remaining period of the former hedging relationship, provided the hedged item continues to be outstanding or it is probable the forecasted transaction will occur. People’s United uses the dollar offset method, regression analysis and scenario analysis to assess hedge effectiveness at inception and on an ongoing basis. Such methods are chosen based on the nature of the hedge strategy and are used consistently throughout the life of the hedging relationship. Certain derivative financial instruments are offered to commercial customers to assist them in meeting their financing and investing objectives and for their risk management purposes. These derivative financial instruments consist primarily of interest rate swaps and caps, but also include foreign exchange contracts. The interest rate and foreign exchange risks associated with customer interest rate swaps and caps and foreign exchange contracts are mitigated by entering into similar derivatives having essentially offsetting terms with institutional counterparties. Interest rate-lock commitments extended to borrowers relate to the origination of residential mortgage loans. To mitigate the IRR inherent in these commitments, People’s United enters into mandatory delivery and best efforts contracts to sell adjustable-rate and fixed-rate residential mortgage loans (servicing released). Forward commitments to sell and interest rate-lock commitments on residential mortgage loans are considered derivatives and their respective estimated fair values are adjusted based on changes in interest rates. Changes in the fair value of derivatives for which hedge accounting is not applied are recognized in current earnings, including customer derivatives, interest-rate lock commitments and forward sale commitments.
Balance Sheet Offsetting	Balance Sheet Offsetting Assets and liabilities relating to certain financial instruments, including derivatives, may be eligible for offset in the Consolidated Statements of Condition and/or subject to enforceable master netting arrangements or similar agreements. People’s United’s derivative transactions with institutional counterparties are generally executed under International Swaps and Derivative Association (“ISDA”) master agreements, which include “right of set-off” provisions that provide for a single net settlement of all interest rate swap positions, as well as collateral, in the event of default on, or the termination of, any one contract. Nonetheless, the Company does not, except as discussed in Note 23, offset asset and liabilities under such arrangements in the Consolidated Statements of Condition. Collateral (generally in the form of marketable debt securities) pledged by counterparties in connection with derivative transactions is not reported in the Consolidated Statements of Condition unless the counterparty defaults. Collateral that has been pledged by People’s United to counterparties continues to be reported in the Consolidated Statements of Condition unless the Company defaults.
Fair Value Measurements	Fair Value Measurements Accounting standards related to fair value measurements define fair value, provide a framework for measuring fair value and establish related disclosure requirements. Broadly, fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants at the measurement date. Accordingly, an “exit price” approach is required in determining fair value. In support of this principle, a fair value hierarchy has been established that prioritizes the inputs used to measure fair value, requiring entities to maximize the use of market or observable inputs (as more reliable measures) and minimize the use of unobservable inputs. Observable inputs reflect market data obtained from independent sources, while unobservable inputs generally require significant management judgment. The three levels within the fair value hierarchy are as follows: • Level 1 — Unadjusted quoted market prices for identical assets or liabilities in active markets that the entity has the ability to access at the measurement date (such as active exchange-traded equity securities or mutual funds and certain U.S. and government agency debt securities). • Level 2 — Observable inputs other than quoted prices included in Level 1, such as: ◦ quoted prices for similar assets or liabilities in active markets (such as U.S. agency and GSE issued mortgage-backed and CMO securities); ◦ quoted prices for identical or similar assets or liabilities in less active markets (such as certain U.S. and government agency debt securities, and corporate and municipal debt securities that trade infrequently); and ◦ other inputs that (i) are observable for substantially the full term of the asset or liability (e.g. interest rates, yield curves, prepayment speeds, default rates, etc.) or (ii) can be corroborated by observable market data (such as interest rate and currency derivatives and certain other securities). • Level 3 — Valuation techniques that require unobservable inputs that are supported by little or no market activity and are significant to the fair value measurement of the asset or liability (such as pricing models, discounted cash flow methodologies and similar techniques that typically reflect management’s own estimates of the assumptions a market participant would use in pricing the asset or liability). People’s United maintains policies and procedures to value assets and liabilities using the most relevant data available.
Stock-Based Compensation	Stock-Based Compensation People’s United’s stock-based compensation plans provide for awards of stock options, restricted stock and performance shares to directors, officers and employees. Costs resulting from the issuance of such share-based payment awards are required to be recognized in the financial statements based on the grant date fair value of the award. Stock-based compensation expense is recognized over the requisite service period, which is generally the vesting period.
New Accounting Standards	New Accounting Standards Standards effective in 2019 Accounting for Leases In February 2016, the Financial Accounting Standards Board (the “FASB”) amended its standards with respect to the accounting for leases. The amended guidance serves to replace all current GAAP guidance on this topic and requires that an operating lease be recognized on the statement of condition as a right-of-use (“ROU”) asset along with a corresponding liability representing the rent obligation. Key aspects of current lessor accounting generally remain unchanged from existing guidance, although the definition of eligible initial direct costs (“IDC”) has been amended. The guidance became effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018 (January 1, 2019 for People’s United) and, as originally issued, required the use of the modified retrospective transition approach for existing leases that have not expired before the date of initial application. In July 2018, the FASB issued two targeted improvements to the standard with the objective of reducing the cost and complexity of implementing the guidance. These amendments, which have the same effective date and transition requirements as the new lease standard, serve to (i) introduce an optional transition method allowing entities to recognize a cumulative-effect transition adjustment to the opening balance of retained earnings in the period of adoption rather than in the earliest period presented and (ii) provide a practical expedient whereby lessors can elect, by class of underlying asset, to not separate lease and related non-lease components if certain criteria are met. The Company elected the optional transition method which results in the modified retrospective approach being applied on January 1, 2019 (as opposed to January 1, 2017). The Company also elected certain transition relief options provided in the standard, including the package of practical expedients. These relief options allow the Company to forego (i) the recognition of ROU assets and lease liabilities arising from short-term leases (i.e. leases with terms of twelve months or less) and (ii) a reassessment as to: (a) whether expired or existing contracts are or contain leases; (b) the lease classification for expired or existing leases; and (c) whether previously capitalized IDC for existing leases would qualify for capitalization under the standard. The Company did not elect the hindsight practical expedient which allows entities to use hindsight when determining lease term and impairment of ROU assets. The Company identified several areas that are within the scope of the guidance, including (i) its contracts with respect to leased real estate and office equipment and (ii) lease agreements entered into with customers of the Company’s equipment financing businesses. The most significant impact of adopting the guidance relates to real estate (primarily branch locations) and office equipment subject to non-cancelable operating lease agreements entered into by the Company as lessee. The amount of the ROU assets and corresponding lease liabilities recorded upon adoption were based, primarily, on the present value of unpaid future minimum lease payments, the amount of which is dependent upon the population of leases in effect at the date of adoption, as well as assumptions with respect to renewals and/or extensions and the interest rate used to discount the future lease obligations. The Federal banking agencies have indicated that to the extent a ROU asset arises due to a lease of a tangible asset (e.g. building or equipment), the asset should be: (i) treated as a tangible asset not subject to deduction from regulatory capital; (ii) risk-weighted at 100%; and (iii) included in total assets for leverage capital purposes. As it relates to lease agreements entered into with equipment financing customers, and for which the Company acts as lessor, the impact principally relates to the definition of eligible IDC under the new guidance. Specifically, the standard maintains a narrower definition of IDC which will result in the Company recognizing immediately (rather than deferring) certain lease origination-related expenses. Such expenses would be offset by the recognition of a higher yield on the underlying leases over their contractual term. The guidance was adopted on January 1, 2019 and resulted in the recognition of (i) operating lease liabilities totaling $268.8 million, based on the present value of the remaining minimum lease payments, determined using a discount rate as of the effective date, and (ii) corresponding ROU assets totaling $248.5 million, based upon the operating lease liabilities, adjusted for prepaid and deferred rent, and liabilities associated with lease termination costs. This transition adjustment served to increase risk-weighted assets, resulting in an approximate 5 to 10 basis point decrease in the risk-based capital ratios of both the Company and the Bank at that time. While the adoption of the guidance did not have a material impact on the Company’s Consolidated Statements of Income or Consolidated Statements of Cash Flows, the Company has, where appropriate, modified its business processes, systems and internal controls in order to support the recognition, measurement and disclosure requirements of the new standard. Expanded disclosures about the nature and terms of lease agreements, which are required prospectively, have been included in Note 6. Premium Amortization — Purchased Callable Debt Securities In April 2017, the FASB amended its standards to shorten the amortization period for certain callable debt securities held at a premium, requiring such premiums to be amortized to the earliest call date unless applicable guidance related to certain pools of securities is applied to consider estimated prepayments. Under prior guidance, entities were generally required to amortize premiums on individual, non-pooled callable debt securities as a yield adjustment over the contractual life of the security. This amendment, which does not change the accounting for callable debt securities held at a discount, became effective for People's United on January 1, 2019 and did not have a significant impact on the Company’s Consolidated Financial Statements. Derivatives and Hedging In August 2017, the FASB amended its standards with respect to the accounting for derivatives and hedging, simplifying existing guidance in order to enable companies to more accurately portray the economic effects of risk management activities in the financial statements and enhancing the transparency and understandability of hedge results through improved disclosures. This new guidance became effective on January 1, 2019 for People’s United and did not have a significant impact on the Company’s Consolidated Financial Statements. Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income In February 2018, as a result of the enactment of the Tax Cuts and Jobs Act (the “Act”), the FASB issued new accounting guidance providing entities with the option to reclassify, from accumulated other comprehensive income to retained earnings, certain “stranded tax effects” resulting from application of the Act. An entity that elects to do so must provide the following disclosures in the period of adoption: (i) that an election was made to reclassify the income tax effects of the Act from accumulated other comprehensive income to retained earnings and (ii) a description of other income tax effects related to the application of the Act that were reclassified from accumulated other comprehensive income to retained earnings, if any (e.g. income tax effects other than the effect of the change in the U.S. federal corporate income tax rate on gross deferred tax amounts and related valuation allowances). Regardless of whether an entity elects to adopt the guidance or not it is required to disclose its accounting policy for releasing income tax effects from accumulated other comprehensive income (e.g. the portfolio approach or the security-by-security approach). The guidance is effective for all organizations for fiscal years beginning after December 15, 2018 (January 1, 2019 for People’s United), including interim periods within those fiscal years, and early adoption is permitted. Entities electing to apply the guidance should do so (i) as of the beginning of the period of adoption or (ii) retrospectively to each period in which the effect of the change in the U.S. federal corporate income tax rate is recognized. The Company elected to early adopt this amendment effective January 1, 2018 (for the reporting period ending on March 31, 2018). Upon adoption, $37.9 million, representing the income tax effects of the Act as well as the indirect impacts from the decreased federal tax effect on future state tax benefits, was reclassified from AOCL to retained earnings. The reclassification adjustment, which related to: (i) the net actuarial loss on defined benefit pension and postretirement plans; (ii) the net unrealized loss on debt securities available-for-sale and debt securities transferred to held-to-maturity; and (iii) the net unrealized loss on derivatives accounted for as cash flow hedges, served to increase regulatory capital by $37.9 million, which resulted in an approximate 11 basis point increase in the risk-based capital ratios of both the Company and the Bank at that time. Standards effective in 2020 Financial Instruments — Credit Losses In June 2016, the FASB amended its standards with respect to certain aspects of measurement, recognition and disclosure of credit losses on loans and other financial instruments carried at amortized cost, as well as available-for-sale debt securities and purchased financial assets with credit deterioration (“PCD assets”). The amendment is to be applied through a cumulative-effect adjustment to retained earnings as of the beginning of the first reporting period in which the guidance is effective (that is, a modified-retrospective approach). For certain assets (such as debt securities for which other-than-temporary impairment has been recognized before the effective date and PCD assets), a prospective transition approach is required. For existing PCI assets, upon adoption, the amortized cost basis will be adjusted to reflect the addition of the allowance for credit losses (“ACL”). This transition relief avoids the need for a reporting entity to reassess its purchased financial assets that exist as of the date of adoption in order to determine whether they would have met, at acquisition, the new criteria of ‘more-than insignificant’ credit deterioration since origination. The transition relief also allows an entity to accrete the remaining noncredit discount (based on the revised amortized cost basis) into interest income over the life of the related asset using the interest method. For public business entities, this new amendment is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019 (January 1, 2020 for People’s United) and earlier application is permitted as of the beginning of an interim or annual reporting period beginning after December 15, 2018. While early adoption is permitted, the Company has not elected that option. To assist in implementing the standard, the Company formed a cross-functional working group, comprised of individuals from various disciplines, including credit, risk management, information technology and finance. The implementation activities of the working group were subject to the Company’s established corporate governance and oversight structure. Initially, some of the more important activities of the working group included: (i) purchasing and installing a third-party vendor solution to aid in application of the standard; (ii) establishing the Company’s portfolio segmentation; (iii) fulfilling historical data requirements necessary to comply with the standard; and (iv) developing and testing loss estimation models leveraged from existing credit models used to comply with other regulatory requirements. Subsequently, the working group tested, refined and validated its loss estimation framework during parallel runs that involved a comprehensive assessment of: (i) model functionality; (ii) internal control design and effectiveness; and (iii) related governance activities. The working group is currently in the final stages of implementation, documenting the relevant processes, systems, internal controls and data sources necessary to support the requirements of the new standard, including related disclosures, and executing established review and approval protocols. Under the standard, the Company will determine the ACL based on its historical loss experience, current borrower-specific risk characteristics, forecasts of future economic conditions and other relevant factors. In doing so, the Company will utilize a two-year reasonable and supportable forecast period followed by a one-year period over which estimated losses will revert to historical loss experience for the remaining life of the loan. As a result of the required change to determining estimated credit losses from an “incurred loss” model to a “life of loan” model, the new guidance can be expected to result in an increase in the allowance for loan losses, particularly for longer duration portfolios. That said, any estimate of expected credit losses will be dependent upon portfolio size, composition and credit quality, as well as economic conditions and forecasts at that time. Based upon forecasted economic conditions and portfolio balances existing as of December 31, 2019, the Company expects to record a pre-tax adjustment to retained earnings of approximately $60 million, representing the aggregate effect of adoption on the ACL for loans and securities as well as the reserve for unfunded commitments. The Company also expects to record an adjustment of approximately $30 million to the amortized cost basis of its existing PCI loans to reflect the addition of the ACL on such loans. The increase in aggregate loan allowance levels is driven, primarily, by higher reserve requirements associated with the Company’s retail portfolios (i.e. residential mortgage and home equity) due to the difference between the loss emergence periods of these portfolios under the incurred loss model and the expected remaining life of such loans as required by the standard, partially offset by lower reserve requirements associated with certain of the Company’s commercial portfolios, which generally have shorter contractual maturities. The Company’s held-to-maturity debt securities portfolio consists primarily of agency-backed securities and highly-rated municipal and corporate bonds, all of which inherently have minimal non-payment risk. The adjustments noted above serve to reduce regulatory capital ratios for both the Holding Company and the Bank by approximately 10 basis points. The Company has elected to phase-in, over three years, the day-one regulatory capital effects of the standard in accordance with the Federal banking agencies final rule issued in December 2018. Simplifying the Test for Goodwill Impairment In January 2017, the FASB amended its standards with respect to goodwill, simplifying how an entity is required to conduct the impairment assessment by eliminating Step 2, which requires a hypothetical purchase price allocation, from the goodwill impairment test. Instead, goodwill impairment will now be measured as the amount by which a reporting unit’s carrying amount exceeds its fair value, not to exceed the carrying amount of goodwill. An entity will still have the option to perform a qualitative assessment to determine if a quantitative impairment test is necessary. For public business entities, this new guidance is effective in fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019 (January 1, 2020 for People’s United) and is to be applied prospectively. Early adoption is permitted for any impairment tests performed after January 1, 2017. This amendment, which the Company elected to early adopt effective January 1, 2018, did not have a significant impact on the Company’s Consolidated Financial Statements. Disclosure Requirements — Fair Value Measurement In August 2018, the FASB issued targeted amendments that serve to eliminate, add and modify certain disclosure requirements for fair value measurements. Among the changes, entities are no longer required to disclose the amount of and reasons for transfers between Level 1 and Level 2 of the fair value hierarchy, but are required to disclose the range and weighted average used to develop significant unobservable inputs for Level 3 fair value measurements. These amendments are effective for interim and annual reporting periods beginning after December 15, 2019 (January 1, 2020 for People’s United) and early adoption is permitted. Entities may also elect to (i) early adopt the eliminated and/or modified disclosure requirements and (ii) delay adoption of the new disclosure requirements until their effective date. The provisions set forth in this guidance, which the Company elected to early adopt in 2018, have been reflected in Note 20 (as applicable) and did not have a significant impact on the Company’s Consolidated Financial Statements. Standards effective in 2021 Disclosure Requirements — Defined Benefit Plans In August 2018, the FASB issued targeted amendments that serve to make minor changes to the disclosure requirements for employers that sponsor defined benefit pension and/or other postretirement benefit plans. More specifically, the amendments (i) remove disclosures that are no longer considered cost beneficial, (ii) clarify the specific requirements of selected disclosures and (iii) add disclosure requirements identified as relevant. These amendments are effective for fiscal years ending after December 15, 2020 (January 1, 2021 for People’s United) and early adoption is permitted. The provisions set forth in this guidance, which the Company elected to early adopt in 2018, have been reflected in Note 18 (as applicable) and did not have a significant impact on the Company’s Consolidated Financial Statements. Simplifying the Accounting for Income Taxes In December 2019, the FASB amended its standards with respect to income taxes, simplifying the accounting in several areas, including intra-period tax allocation, deferred tax liabilities related to outside basis differences, and year-to-date losses in interim periods, among others. For public business entities, this new guidance is effective in fiscal years, and interim periods within those fiscal years, beginning after December 15, 2020 (January 1, 2021 for People’s United) and early adoption is permitted. If an entity elects to early adopt, it must adopt all changes as a result of the guidance. Adoption of this standard is not expected to have a significant impact on the Company’s Consolidated Financial Statements .
Fair Value Measurements	Recurring Fair Value Measurements Trading Debt Securities, Equity Securities and Debt Securities Available-For-Sale When available, People’s United uses quoted market prices for identical securities received from an independent, nationally-recognized, third-party pricing service (as discussed further below) to determine the fair value of investment securities such as U.S. Treasury and agency securities and equity securities that are included in Level 1. When quoted market prices for identical securities are unavailable, People’s United uses prices provided by the independent pricing service based on recent trading activity and other observable information including, but not limited to, market interest rate curves, referenced credit spreads and estimated prepayment rates where applicable. These investments include certain U.S. and government agency debt securities, corporate and municipal debt securities and GSE mortgage-backed and CMO securities, all of which are included in Level 2. The Company’s available-for-sale debt securities are primarily comprised of GSE mortgage-backed securities. The fair value of these securities is based on prices obtained from the independent pricing service. The pricing service uses various techniques to determine pricing for the Company’s mortgage-backed securities, including option pricing and discounted cash flow analysis. The inputs include benchmark yields, reported trades, broker/dealer quotes, issuer spreads, benchmark securities, bids, offers, reference data, monthly payment information and collateral performance. At December 31, 2019, the entire available-for-sale mortgage-backed securities portfolio was comprised of GSE mortgage-backed and CMO securities with original final maturities ranging from 10 to 40 years. At December 31, 2018, the entire available-for-sale mortgage-backed securities portfolio was comprised of GSE mortgage-backed securities with original final maturities of 10- and 15-years. An active market exists for securities that are similar to the Company’s GSE mortgage-backed and CMO securities, making observable inputs readily available. Changes in the prices obtained from the pricing service are analyzed from month to month, taking into consideration changes in market conditions including changes in mortgage spreads, changes in U.S. Treasury security yields and changes in generic pricing of securities with similar duration. As a further point of validation, the Company generates its own month-end fair value estimate for all mortgage-backed securities, and state and municipal securities. While the Company has not adjusted the prices obtained from the independent pricing service, any notable differences between those prices and the Company’s estimates are subject to further analysis. This additional analysis may include a review of prices provided by other independent parties, a yield analysis, a review of average life changes using Bloomberg analytics and a review of historical pricing for the particular security. Based on management’s review of the prices provided by the pricing service, the fair values incorporate observable market inputs used by market participants at the measurement date and, as such, are classified as Level 2 securities. Other Assets As discussed in Note 18, certain unfunded, nonqualified supplemental plans have been established to provide retirement benefits to certain senior officers. People’s United has funded two trusts to provide benefit payments to the extent such benefits are not paid directly by People’s United, the assets of which are included in other assets in the Consolidated Statements of Condition. When available, People’s United determines the fair value of the trust assets using quoted market prices for identical securities received from a third-party nationally recognized pricing service. Derivatives People’s United values its derivatives using internal models that are based on market or observable inputs, including interest rate curves and forward/spot prices for selected currencies. Derivative assets and liabilities included in Level 2 represent interest rate swaps and caps, foreign exchange contracts, risk participation agreements, forward commitments to sell residential mortgage loans and interest rate-lock commitments on residential mortgage loans. Non-Recurring Fair Value Measurements Loans Held-for-Sale Loans held-for-sale are recorded at the lower of cost or fair value and are therefore measured at fair value on a non-recurring basis. When available, People’s United uses observable secondary market data, including pricing on recent closed market transactions for loans with similar characteristics. Accordingly, such loans are classified as Level 2 measurements. When observable data is unavailable, valuation methodologies using current market interest rate data adjusted for inherent credit risk are used, and such loans are included in Level 3. Impaired Loans Loan impairment is deemed to exist when full repayment of principal and interest according to the contractual terms of the loan is no longer probable. Impaired loans are reported based on one of three measures: (i) the present value of expected future cash flows discounted at the loan’s original effective interest rate; (ii) the loan’s observable market price; or (iii) the fair value of the collateral (less estimated cost to sell) if the loan is collateral dependent. Accordingly, certain impaired loans may be subject to measurement at fair value on a non-recurring basis. People’s United has estimated the fair values of these assets using Level 3 inputs, such as discounted cash flows based on inputs that are largely unobservable and, instead, reflect management’s own estimates of the assumptions a market participant would use in pricing such loans and/or the fair value of collateral based on independent third-party appraisals for collateral-dependent loans. Such appraisals are based on the market and/or income approach to value and are subject to a discount (to reflect estimated cost to sell) that generally approximates 10%. REO and Repossessed Assets REO and repossessed assets are recorded at the lower of cost or fair value, less estimated selling costs, and are therefore measured at fair value on a non-recurring basis. People’s United has estimated the fair values of these assets using Level 3 inputs, such as independent third-party appraisals and price opinions. Such appraisals are based on the market and/or income approach to value and are subject to a discount (to reflect estimated cost to sell) that generally approximates 10%. Assets that are acquired through loan default are recorded as held-for-sale initially at the lower of the recorded investment in the loan or fair value (less estimated selling costs) upon the date of foreclosure/repossession. Subsequent to foreclosure/repossession, valuations are updated periodically and the carrying amounts of these assets may be reduced further. Mortgage Servicing Rights Mortgage servicing rights are evaluated for impairment based upon the fair value of the servicing rights as compared to their amortized cost. The fair value of mortgage servicing rights is based on a valuation model that calculates the present value of estimated net servicing income. This model incorporates certain assumptions that market participants would likely use in estimating future net servicing income, such as interest rates, prepayment speeds and the cost to service (including delinquency and foreclosure costs), all of which require a degree of management judgment. Adjustments are only recorded when the discounted cash flows derived from the valuation model are less than the carrying value of the asset. As such, mortgage servicing rights are subject to measurement at fair value on a non-recurring basis and are classified as Level 3 assets.
Segment Information	Public companies are required to report (i) certain financial and descriptive information about “reportable operating segments,” as defined, and (ii) certain enterprise-wide financial information about products and services, geographic areas and major customers. Operating segment information is reported using a “management approach” that is based on the way management organizes the segments for purposes of making operating decisions and assessing performance. People’s United’s operations are divided into three primary operating segments that represent its core businesses: Commercial Banking; Retail Banking; and Wealth Management. In addition, the Treasury area manages People’s United’s securities portfolio, short-term investments, brokered deposits, wholesale borrowings and the funding center. The Company’s operating segments have been aggregated into two reportable segments: Commercial Banking and Retail Banking. These reportable segments have been identified and organized based on the nature of the underlying products and services applicable to each segment, the type of customers to whom those products and services are offered and the distribution channel through which those products and services are made available. With respect to the Company’s traditional wealth management activities, this presentation results in the allocation of the Company’s insurance business and certain trust activities to the Commercial Banking segment, and the allocation of the Company’s brokerage business and certain other trust activities to the Retail Banking segment. Commercial Banking consists principally of commercial real estate lending, commercial and industrial lending, and commercial deposit gathering activities. This segment also includes equipment financing operations, as well as cash management, correspondent banking, municipal banking, institutional trust services, corporate trust, commercial insurance services provided by PUIA and private banking. Retail Banking includes, as its principal business lines, consumer lending (including residential mortgage and home equity lending) and consumer deposit gathering activities. This segment also includes brokerage, financial advisory services, investment management services and life insurance provided by PSI, investment advisory services and financial management and planning services provided by PUA and non-institutional trust services. People’s United’s segment disclosure is based on an internal profitability reporting system, which generates information by operating segment based on a series of management estimates and allocations regarding funds transfer pricing (“FTP”), the provision for loan losses, non-interest expense and income taxes. These estimates and allocations, some of which are subjective in nature, are subject to periodic review and refinement. Any changes in estimates and allocations that may affect the reported results of any segment will not affect the consolidated financial position or results of operations of People’s United as a whole. FTP, which is used in the calculation of each operating segment’s net interest income, measures the value of funds used in and provided by an operating segment. The difference between the interest income on earning assets and the interest expense on funding liabilities, and the corresponding FTP charge for interest income or credit for interest expense, results in net spread income. For fixed-term assets and liabilities, the FTP rate is assigned at the time the asset or liability is originated by reference to the Company’s FTP yield curve, which is updated daily. For non-maturity-term assets and liabilities, the FTP rate is determined based upon the underlying characteristics, or behavior, of each particular product and results in the use of a historical rolling average FTP rate determined over a period that is most representative of the average life of the particular asset or liability. While the Company’s FTP methodology serves to remove IRR from the operating segments and better facilitate pricing decisions, thereby allowing management to assess the longer-term profitability of an operating segment more effectively, it may, in sustained periods of low and/or high interest rates, result in a measure of operating segment net interest income that is not reflective of current interest rates. A five-year rolling average net charge-off rate is used as the basis for the provision for loan losses for the respective operating segment in order to present a level of portfolio credit cost that is representative of the Company’s historical experience, without presenting the potential volatility from year-to-year changes in credit conditions. While this method of allocation allows management to assess the longer-term profitability of an operating segment more effectively, it may result in a measure of an operating segment’s provision for loan losses that does not reflect actual incurred losses for the periods presented. People’s United allocates a majority of non-interest expenses to each operating segment using a full-absorption costing process (i.e. all expenses are fully-allocated to the segments). Direct and indirect costs are analyzed and pooled by process and assigned to the appropriate operating segment and corporate overhead costs are allocated to the operating segments. Income tax expense is allocated to each operating segment using a constant rate, based on an estimate of the consolidated effective income tax rate for the year. Average total assets and average total liabilities are presented for each reportable segment due to management’s reliance, in part, on such average balances for purposes of assessing segment performance. Average total assets of each reportable segment include allocated goodwill and intangible assets, both of which are reviewed for impairment at least annually.
People's United Employee Pension and Other Postretirement Plans	People’s United Employee Pension and Other Postretirement Plans People’s United maintains a qualified noncontributory defined benefit pension plan (the “People’s Qualified Plan”) that covers substantially all full-time and part-time employees who (i) meet certain age and length of service requirements and (ii) were employed by the Bank prior to August 14, 2006. Benefits are based upon the employee’s years of credited service and either the average compensation for the last five years or the average compensation for the five New employees of the Bank starting on or after August 14, 2006 are not eligible to participate in the People’s Qualified Plan. Instead, the Bank makes contributions on behalf of these employees to a qualified defined contribution plan in an annual amount equal to 3% of the employee’s eligible compensation. Employee participation in this plan is restricted to employees who (i) are at least 18 years of age and (ii) worked at least 1000 hours in a year. Both full-time and part-time employees are eligible to participate as long as they meet these requirements. In July 2011, the Bank amended the People’s Qualified Plan to “freeze”, effective December 31, 2011, the accrual of pension benefits for People’s Qualified Plan participants. As such, participants will not earn any additional benefits after that date. Instead, effective January 1, 2012, the Bank began making contributions on behalf of these participants to a qualified defined contribution plan in an annual amount equal to 3% of the employee’s eligible compensation. In addition to the People’s Qualified Plan, People’s United continues to maintain qualified defined benefit pension plans that cover (i) former First Connecticut employees who meet certain eligibility requirements (the “First Connecticut Qualified Plan”) and (ii) former United Financial employees who meet certain eligibility requirements (the “United Financial Qualified Plan”). All benefits under these plans were frozen effective February 28, 2013 and December 31, 2012, respectively. Effective October 1, 2018, both the Chittenden Qualified Plan and the Suffolk Qualified Plan were merged into the People’s Qualified Plan. People’s United also maintains (i) unfunded, nonqualified supplemental plans to provide retirement benefits to certain senior officers (the “People’s Supplemental Plans”) and (ii) an unfunded plan that provides retirees with optional medical, dental and life insurance benefits (the “People’s Postretirement Plan”). People’s United accrues the cost of these postretirement benefits over the employees’ years of service to the date of their eligibility for such benefit. People’s United also continues to maintain: (1) for certain eligible former First Connecticut employees (i) an unfunded, nonqualified supplemental retirement plan (the “First Connecticut Supplemental Plan”) and (ii) unfunded plans that provide medical, dental and life insurance benefits (the “First Connecticut Postretirement Plans”); (2) for certain eligible former BSB Bancorp employees (i) an unfunded, nonqualified supplemental retirement plan (the “BSB Bancorp Supplemental Plan”) and (ii) unfunded plans that provide life insurance benefits (the “BSB Bancorp Post Retirement Welfare (Life Insurance) Plan”); and (3) for certain former United Financial employees (i) an unfunded, nonqualified supplemental retirement plan (the “United Financial Supplemental Plan”) and (ii) unfunded plans that provide medical, dental and life insurance benefits (the “United Financial Postretirement Benefit Plan”).
Employee Stock Ownership Plan	Employee Stock Ownership Plan In April 2007, People’s United established an ESOP. At that time, People’s United loaned the ESOP $216.8 million to purchase 10,453,575 shares of People’s United common stock in the open market. In order for the ESOP to repay the loan, People’s United expects to make annual cash contributions of approximately $18.8 million until 2036. Such cash contributions may be reduced by the cash dividends paid on unallocated ESOP shares, which totaled $4.4 million in 2019, $4.6 million in 2018 and $4.8 million in 2017. At December 31, 2019, the loan balance totaled $171.8 million. Employee participation in this plan is restricted to those employees who (i) are at least 18 years of age and (ii) worked at least 1000 hours within 12 months of their hire date or any plan year (January 1 to December 31) after their date of hire. Employees meeting the aforementioned eligibility criteria during the plan year must continue to be employed as of the last day of the plan year in order to receive an allocation of shares for that plan year. Shares of People’s United common stock are held by the ESOP and allocated to eligible participants annually based upon a percentage of each participant’s eligible compensation. Since the ESOP was established, a total of 4,529,883 shares of People’s United common stock have been allocated or committed to be released to participants’ accounts. At December 31, 2019, 5,923,692 shares of People’s United common stock, with a fair value of $100.1 million at that date, have not been allocated or committed to be released. Compensation expense related to the ESOP is recognized at an amount equal to the number of common shares committed to be released by the ESOP for allocation to participants’ accounts multiplied by the average fair value of People’s United’s common stock during the reporting period. The difference between the fair value of the shares of People’s United’s common stock committed to be released and the cost of those common shares is recorded as a credit to additional paid-in capital (if fair value exceeds cost) or, to the extent that no such credits remain in additional paid-in capital, as a charge to retained earnings (if fair value is less than cost). Expense recognized for the ESOP totaled $5.7 million, $6.2 million and $6.4 million for the years ended December 31, 2019, 2018 and 2017, respectively.
Directors' Equity Compensation Plan	Directors’ Equity Compensation Plan The People's United Financial, Inc. Directors' Equity Compensation Plan (the "Directors' Plan") provides for an annual award of shares of People's United common stock with a fair value of approximately $95,000 to each non-employee director immediately following each annual meeting of shareholders. Shares of People's United common stock issued pursuant to the Directors' Plan are subject to a one In 2019, 2018 and 2017, directors were granted a total of 58,340 shares, 51,680 shares and 49,050 shares, respectively, of People’s United common stock, with grant date fair values of $16.31 per share, $18.21 per share and $17.65 per share, respectively, at those dates. Expense totaling $0.9 million for the Directors’ Plan was recognized for each of the years ended December 31, 2019, 2018 and 2017. At December 31, 2019, a total of 333,981 shares remain available for issuance.

Acquisitions and Dispositions (

Acquisitions and Dispositions (Tables)	12 Months Ended
	Dec. 31, 2019
Business Combinations [Abstract]
Estimated Fair Values of Assets Acquired and Liabilities Assumed	The acquisition-date estimated fair values of the assets acquired and liabilities assumed in the acquisition of United Financial are s ummarized as follows: (in millions) Assets: Cash and cash equivalents $ 594.9 Securities 381.3 Loans 5,535.5 Goodwill 204.3 Core deposit intangible 41.5 Premises and equipment 61.8 BOLI 196.5 Lease ROU assets 56.3 Mortgage servicing rights 10.6 REO 1.2 Other assets 136.2 Total assets $ 7,220.1 Liabilities: Deposits $ 5,687.2 Borrowings 622.4 Lease liabilities 61.4 Other liabilities 128.5 Total liabilities $ 6,499.5 Total purchase price $ 720.6 The acquisition-date estimated fair values of the assets acquired and liabilities assumed in the acquisition of BSB Bancorp are s ummarized as follows: (in millions) Assets: Cash and cash equivalents $ 108.7 Securities 175.8 Loans 2,642.9 Goodwill 144.9 Core deposit intangible 39.5 Premises and equipment 8.3 BOLI 36.8 Other assets 29.8 Total assets $ 3,186.7 Liabilities: Deposits $ 2,118.7 Borrowings 696.6 Other liabilities 46.9 Total liabilities $ 2,862.2 Total purchase price $ 324.5
Summary of Pro Forma Financial Information Reflecting Acquisition	The following table presents selected unaudited pro forma financial information of the Company, reflecting the acquisitions of United Financial and BSB Bancorp, assuming the acquisitions were completed as of the beginning of the respective periods: Years ended December 31 (in millions, except per common share data) 2019 2018 Selected Financial Results: Net interest income $ 1,582.5 $ 1,488.6 Provision for loan losses 28.3 30.0 Non-interest income 454.5 408.1 Non-interest expense 1,277.5 1,186.4 Net income 583.5 552.4 Net income available to common shareholders 569.4 538.3 EPS: Basic $ 1.31 $ 1.30 Diluted 1.30 1.29

Cash and Cash Equivalents (Tabl

Cash and Cash Equivalents (Tables)	12 Months Ended
	Dec. 31, 2019
Cash and Cash Equivalents [Abstract]
Cash and Short-Term Investments	Short-term investments consist of the following cash equivalents: As of December 31 (in millions) 2019 2018 Interest-bearing deposits at the FRB-NY $ 219.4 $ 234.0 Money market mutual funds 5.7 26.3 Other (1) 91.7 6.0 Total short-term investments $ 316.8 $ 266.3 (1) Includes cash collateral posted for certain derivative positions at both December 31, 2019 and 2018.

Securities (Tables)

Securities (Tables)	12 Months Ended
	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Available-for-Sale and Held-to-Maturity Debt Securities Gains (Losses)	The amortized cost, gross unrealized gains and losses, and fair value of People’s United’s debt securities available-for-sale and debt securities held-to-maturity are as follows: As of December 31, 2019 (in millions) Amortized Gross Gross Fair Debt securities available-for-sale: U.S. Treasury and agency $ 689.5 $ 0.4 $ (2.8) $ 687.1 GSE mortgage-backed and CMO securities 2,856.3 25.0 (4.1) 2,877.2 Total debt securities available-for-sale $ 3,545.8 $ 25.4 $ (6.9) $ 3,564.3 Debt securities held-to-maturity: State and municipal $ 2,503.9 $ 142.0 $ (0.4) $ 2,645.5 GSE mortgage-backed securities 1,271.4 8.0 (0.3) 1,279.1 Corporate 92.4 1.5 — 93.9 Other 1.5 — — 1.5 Total debt securities held-to-maturity $ 3,869.2 $ 151.5 $ (0.7) $ 4,020.0 As of December 31, 2018 (in millions) Amortized Gross Gross Fair Debt securities available-for-sale: U.S. Treasury and agency $ 699.0 $ 0.1 $ (21.1) $ 678.0 GSE mortgage-backed securities 2,486.6 4.6 (48.2) 2,443.0 Total debt securities available-for-sale $ 3,185.6 $ 4.7 $ (69.3) $ 3,121.0 Debt securities held-to-maturity: State and municipal $ 2,352.4 $ 35.4 $ (18.4) $ 2,369.4 GSE mortgage-backed securities 1,367.5 — (33.2) 1,334.3 Corporate 70.9 0.5 (0.7) 70.7 Other 1.5 — — 1.5 Total debt securities held-to-maturity $ 3,792.3 $ 35.9 $ (52.3) $ 3,775.9
Summary of Amortized Cost, Fair Value and Fully Taxable Equivalent ("FTE") Yield of Debt Securities Based on Remaining Period to Contractual Maturity	The following table is a summary of the amortized cost, fair value and fully taxable equivalent (“FTE”) yield of debt securities as of December 31, 2019, based on remaining period to contractual maturity. Information for GSE mortgage-backed and CMO securities is based on the final contractual maturity dates without considering repayments and prepayments. Available-for-Sale Held-to-Maturity (dollars in millions) Amortized Fair FTE Amortized Fair FTE U.S. Treasury and agency: Within 1 year $ 158.4 $ 158.4 1.84 % $ — $ — — % After 1 but within 5 years 531.1 528.7 1.43 — — — Total 689.5 687.1 1.53 — — — GSE mortgage-backed and CMO Within 1 year — — — 2.7 2.7 2.04 After 1 but within 5 years 84.9 86.9 3.17 861.0 866.6 2.43 After 5 but within 10 years 855.1 867.7 2.67 120.2 121.3 2.52 After 10 years 1,916.3 1,922.6 2.35 287.5 288.5 2.17 Total 2,856.3 2,877.2 2.47 1,271.4 1,279.1 2.38 State and municipal: Within 1 year — — — 10.3 10.4 2.61 After 1 but within 5 years — — — 235.4 245.3 2.78 After 5 but within 10 years — — — 418.8 444.1 3.47 After 10 years — — — 1,839.4 1,945.7 3.81 Total — — — 2,503.9 2,645.5 3.65 Corporate: Within 1 year — — — 5.0 5.0 3.50 After 1 but within 5 years — — — 1.0 1.0 2.67 After 5 but within 10 years — — — 86.4 87.9 4.52 Total — — — 92.4 93.9 4.45 Other: Within 1 year — — — 1.5 1.5 2.46 Total — — — 1.5 1.5 2.46 Total: Within 1 year 158.4 158.4 1.84 19.5 19.6 2.74 After 1 but within 5 years 616.0 615.6 1.67 1,097.4 1,112.9 2.51 After 5 but within 10 years 855.1 867.7 2.67 625.4 653.3 3.43 After 10 years 1,916.3 1,922.6 2.35 2,126.9 2,234.2 3.59 Total $ 3,545.8 $ 3,564.3 2.29 % $ 3,869.2 $ 4,020.0 3.25 %
Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value	The following tables summarize those debt securities with unrealized losses, segregated by the length of time the securities have been in a continuous unrealized loss position at the respective dates. Certain unrealized losses totaled less than $0.1 million. Continuous Unrealized Loss Position Less Than 12 Months 12 Months Or Longer Total As of December 31, 2019 (in millions)_ Fair Unrealized Fair Unrealized Fair Unrealized Debt securities available-for-sale: GSE mortgage-backed and CMO $ 565.4 $ (3.1) $ 509.3 $ (1.0) $ 1,074.7 $ (4.1) U.S. Treasury and agency 181.0 (0.4) 362.4 (2.4) 543.4 (2.8) Total debt securities available-for-sale $ 746.4 $ (3.5) $ 871.7 $ (3.4) $ 1,618.1 $ (6.9) Debt securities held-to-maturity: GSE mortgage-backed securities $ 100.9 $ (0.3) $ 9.1 $ — $ 110.0 $ (0.3) State and municipal 33.0 (0.2) 11.4 (0.2) 44.4 (0.4) Corporate 3.5 — 8.6 — 12.1 — Total debt securities held-to-maturity $ 137.4 $ (0.5) $ 29.1 $ (0.2) $ 166.5 $ (0.7) Continuous Unrealized Loss Position Less Than 12 Months 12 Months Or Longer Total As of December 31, 2018 (in millions) Fair Unrealized Fair Unrealized Fair Unrealized Debt securities available-for-sale: GSE mortgage-backed securities $ 132.4 $ (0.5) $ 1,656.3 $ (47.7) $ 1,788.7 $ (48.2) U.S. Treasury and agency — — 656.2 (21.1) 656.2 (21.1) Total debt securities available-for-sale $ 132.4 $ (0.5) $ 2,312.5 $ (68.8) $ 2,444.9 $ (69.3) Debt securities held-to-maturity: GSE mortgage-backed securities $ — $ — $ 1,334.3 $ (33.2) $ 1,334.3 $ (33.2) State and municipal 113.4 (0.7) 697.6 (17.7) 811.0 (18.4) Corporate 31.2 (0.6) 2.7 (0.1) 33.9 (0.7) Total debt securities held-to-maturity $ 144.6 $ (1.3) $ 2,034.6 $ (51.0) $ 2,179.2 $ (52.3)
Debt Securities, Held-to-maturity	The following tables summarize those debt securities with unrealized losses, segregated by the length of time the securities have been in a continuous unrealized loss position at the respective dates. Certain unrealized losses totaled less than $0.1 million. Continuous Unrealized Loss Position Less Than 12 Months 12 Months Or Longer Total As of December 31, 2019 (in millions)_ Fair Unrealized Fair Unrealized Fair Unrealized Debt securities available-for-sale: GSE mortgage-backed and CMO $ 565.4 $ (3.1) $ 509.3 $ (1.0) $ 1,074.7 $ (4.1) U.S. Treasury and agency 181.0 (0.4) 362.4 (2.4) 543.4 (2.8) Total debt securities available-for-sale $ 746.4 $ (3.5) $ 871.7 $ (3.4) $ 1,618.1 $ (6.9) Debt securities held-to-maturity: GSE mortgage-backed securities $ 100.9 $ (0.3) $ 9.1 $ — $ 110.0 $ (0.3) State and municipal 33.0 (0.2) 11.4 (0.2) 44.4 (0.4) Corporate 3.5 — 8.6 — 12.1 — Total debt securities held-to-maturity $ 137.4 $ (0.5) $ 29.1 $ (0.2) $ 166.5 $ (0.7) Continuous Unrealized Loss Position Less Than 12 Months 12 Months Or Longer Total As of December 31, 2018 (in millions) Fair Unrealized Fair Unrealized Fair Unrealized Debt securities available-for-sale: GSE mortgage-backed securities $ 132.4 $ (0.5) $ 1,656.3 $ (47.7) $ 1,788.7 $ (48.2) U.S. Treasury and agency — — 656.2 (21.1) 656.2 (21.1) Total debt securities available-for-sale $ 132.4 $ (0.5) $ 2,312.5 $ (68.8) $ 2,444.9 $ (69.3) Debt securities held-to-maturity: GSE mortgage-backed securities $ — $ — $ 1,334.3 $ (33.2) $ 1,334.3 $ (33.2) State and municipal 113.4 (0.7) 697.6 (17.7) 811.0 (18.4) Corporate 31.2 (0.6) 2.7 (0.1) 33.9 (0.7) Total debt securities held-to-maturity $ 144.6 $ (1.3) $ 2,034.6 $ (51.0) $ 2,179.2 $ (52.3)
Schedule of Components of Net Security Losses	The components of net security gains (losses) are summarized below. Years ended December 31 (in millions) 2019 2018 2017 Debt securities: Gains $ 0.5 $ 0.1 $ 2.1 Losses (0.4) (10.0) (27.5) Total debt securities 0.1 (9.9) (25.4) Trading debt securities: Gains 0.1 0.1 — Losses — — — Total trading debt securities (1) 0.1 0.1 — Net security gains (losses) $ 0.2 $ (9.8) $ (25.4) (1) Net gains and losses on trading debt securities totaled less than $0.1 million for the year ended December 31, 2017.

Loans (Tables)

Loans (Tables)	12 Months Ended
	Dec. 31, 2019
Receivables [Abstract]
Summary of Loans by Loan Portfolio Segment and Class	The following table summarizes People’s United’s loans by loan portfolio segment and class: 2019 2018 As of December 31 (in millions) Originated Acquired Total Originated Acquired Total Commercial: Commercial real estate $ 10,012.5 $ 4,749.8 $ 14,762.3 $ 9,798.5 $ 1,851.1 $ 11,649.6 Commercial and industrial 9,763.1 1,278.5 11,041.6 8,292.3 796.6 9,088.9 Equipment financing 4,706.1 204.3 4,910.4 3,937.7 401.5 4,339.2 Total Commercial Portfolio 24,481.7 6,232.6 30,714.3 22,028.5 3,049.2 25,077.7 Retail: Residential mortgage: Adjustable-rate 5,366.0 1,698.8 7,064.8 5,854.1 807.9 6,662.0 Fixed-rate 1,222.9 2,030.4 3,253.3 935.1 557.1 1,492.2 Total residential mortgage 6,588.9 3,729.2 10,318.1 6,789.2 1,365.0 8,154.2 Home equity and other consumer: Home equity 1,625.1 781.4 2,406.5 1,789.5 173.0 1,962.5 Other consumer 39.7 117.5 157.2 42.8 4.2 47.0 Total home equity and 1,664.8 898.9 2,563.7 1,832.3 177.2 2,009.5 Total Retail Portfolio 8,253.7 4,628.1 12,881.8 8,621.5 1,542.2 10,163.7 Total loans $ 32,735.4 $ 10,860.7 $ 43,596.1 $ 30,650.0 $ 4,591.4 $ 35,241.4
Summary, by Loan Portfolio Segment, of Activity in Allowance for Loan Losses	The following table presents a summary, by loan portfolio segment, of activity in the allowance for loan losses for the years ended December 31, 2019, 2018 and 2017. With respect to the originated portfolio, an allocation of a portion of the allowance to one segment does not preclude its availability to absorb losses in another segment. Commercial Retail (in millions) Originated Acquired Total Originated Acquired Total Total Balance at December 31, 2016 $ 198.8 $ 6.1 $ 204.9 $ 24.2 $ 0.2 $ 24.4 $ 229.3 Charge-offs (17.1) (4.4) (21.5) (6.4) — (6.4) (27.9) Recoveries 4.6 0.3 4.9 2.1 — 2.1 7.0 Net loan charge-offs (12.5) (4.1) (16.6) (4.3) — (4.3) (20.9) Provision for loan losses 14.8 1.4 16.2 9.8 — 9.8 26.0 Balance at December 31, 2017 201.1 3.4 204.5 29.7 0.2 29.9 234.4 Charge-offs (19.5) (8.1) (27.6) (3.3) — (3.3) (30.9) Recoveries 3.5 1.3 4.8 2.1 — 2.1 6.9 Net loan charge-offs (16.0) (6.8) (22.8) (1.2) — (1.2) (24.0) Provision for loan losses 20.5 7.3 27.8 2.2 — 2.2 30.0 Balance at December 31, 2018 205.6 3.9 209.5 30.7 0.2 30.9 240.4 Charge-offs (20.0) (7.5) (27.5) (4.0) — (4.0) (31.5) Recoveries 5.0 1.3 6.3 3.1 — 3.1 9.4 Net loan charge-offs (15.0) (6.2) (21.2) (0.9) — (0.9) (22.1) Provision for loan losses 26.2 3.4 29.6 (1.1) (0.2) (1.3) 28.3 Balance at December 31, 2019 $ 216.8 $ 1.1 $ 217.9 $ 28.7 $ — $ 28.7 $ 246.6
Summary of Allowance for Loan Losses by Loan Portfolio Segment and Impairment Methodology	The following tables summarize, by loan portfolio segment and impairment methodology, the allowance for loan losses and related portfolio balances: As of December 31, 2019 (in millions) Commercial Retail Total Portfolio Allowance Portfolio Allowance Portfolio Allowance Originated loans: Collectively evaluated for impairment $ 22,938.3 $ 207.8 $ 9,592.8 $ 26.5 $ 32,531.1 $ 234.3 Individually evaluated for impairment 115.0 9.0 89.2 2.2 204.2 11.2 Acquired loans: PCI (1) 308.5 — 87.5 — 396.0 — Purchased performing: Collectively evaluated for impairment 7,344.9 1.1 3,104.8 — 10,449.7 1.1 Individually evaluated for impairment 7.6 — 7.5 — 15.1 — Total $ 30,714.3 $ 217.9 $ 12,881.8 $ 28.7 $ 43,596.1 $ 246.6 As of December 31, 2018 (in millions) Commercial Retail Total Portfolio Allowance Portfolio Allowance Portfolio Allowance Originated loans: Collectively evaluated for impairment $ 21,900.1 $ 198.9 $ 8,535.0 $ 28.4 $ 30,435.1 $ 227.3 Individually evaluated for impairment 128.4 6.7 86.5 2.3 214.9 9.0 Acquired loans: PCI (1) 300.3 2.2 99.6 0.1 399.9 2.3 Purchased performing: Collectively evaluated for impairment 2,744.4 1.7 1,439.1 — 4,183.5 1.7 Individually evaluated for impairment 4.5 — 3.5 0.1 8.0 0.1 Total $ 25,077.7 $ 209.5 $ 10,163.7 $ 30.9 $ 35,241.4 $ 240.4 (1) PCI loans are evaluated for impairment on a pool basis.
Summarized Recorded Investments, by Class of Loan, in Originated Non-Performing Loans	The recorded investments, by class of loan, in originated non-performing loans are summarized as follows: As of December 31 (in millions) 2019 2018 2017 Commercial: Commercial real estate $ 29.8 $ 33.5 $ 23.7 Commercial and industrial 32.1 38.0 32.6 Equipment financing 46.2 42.0 44.3 Total (1) 108.1 113.5 100.6 Retail: Residential mortgage 36.3 38.9 32.7 Home equity 12.6 15.3 15.4 Other consumer — — — Total (2) 48.9 54.2 48.1 Total $ 157.0 $ 167.7 $ 148.7 (1) Reported net of government guarantees totaling $1.3 million, $1.9 million and $3.1 million at December 31, 2019, 2018 and 2017, respectively. These government guarantees relate, almost entirely, to guarantees provided by the Small Business Administration as well as selected other Federal agencies and represent the carrying value of the loans that are covered by such guarantees, the extent of which (i.e. full or partial) varies by loan. At December 31, 2019, the principal loan classes to which these government guarantees relate are commercial and industrial loans (95%) and commercial real estate loans (5%). (2) Includes $17.0 million, $24.8 million and $15.2 million of loans in the process of foreclosure at December 31, 2019, 2018 and 2017, respectively.
Summary of Recorded Investments in TDRs by Class of Loan	The following tables summarize, by class of loan, the recorded investments in loans modified as TDRs during the years ended December 31, 2019 and 2018. For purposes of this disclosure, recorded investments represent amounts immediately prior to and subsequent to the restructuring. Year ended December 31, 2019 (dollars in millions) Number of Pre-Modification Post-Modification Commercial: Commercial real estate (1) 12 $ 17.2 $ 17.2 Commercial and industrial (2) 33 31.9 31.9 Equipment financing (3) 37 24.9 24.9 Total 82 74.0 74.0 Retail: Residential mortgage (4) 85 26.3 26.3 Home equity (5) 102 9.0 9.0 Other consumer — — — Total 187 35.3 35.3 Total 269 $ 109.3 $ 109.3 (1) Represents the following concessions: extension of term (7 contracts; recorded investment of $2.1 million); reduced payment and/or payment deferral (1 contract; recorded investment of $0.6 million); or a combination of concessions (4 contracts; recorded investment of $14.5 million). (2) Represents the following concessions: extension of term (26 contracts; recorded investment of $26.4 million); reduced payment and/or payment deferral (3 contracts; recorded investment of $0.8 million); or a combination of concessions (4 contracts; recorded investment of $4.7 million). (3) Represents the following concessions: extension of term (5 contracts; recorded investment of $1.6 million); reduced payment and/or payment deferral (26 contracts; recorded investment of $18.9 million); or a combination of concessions (6 contracts; recorded investment of $4.4 million). (4) Represents the following concessions: loans restructured through bankruptcy (45 contracts; recorded investment of $9.9 million); reduced payment and/or payment deferral (24 contracts; recorded investment of $10.1 million); or a combination of concessions (16 contracts; recorded investment of $6.3 million). (5) Represents the following concessions: loans restructured through bankruptcy (54 contracts; recorded investment of $3.2 million); reduced payment and/or payment deferral (18 contracts; recorded investment of $2.9 million); or a combination of concessions (30 contracts; recorded investment of $2.9 million). Year ended December 31, 2018 (dollars in millions) Number of Pre-Modification Post-Modification Commercial: Commercial real estate (1) 13 $ 27.6 $ 27.6 Commercial and industrial (2) 47 73.1 73.1 Equipment financing (3) 31 31.6 31.6 Total 91 132.3 132.3 Retail: Residential mortgage (4) 38 9.5 9.5 Home equity (5) 79 7.3 7.3 Other consumer — — — Total 117 16.8 16.8 Total 208 $ 149.1 $ 149.1 (1) Represents the following concessions: extension of term (9 contracts; recorded investment of $24.1 million); reduced payment and/or payment deferral (1 contract; recorded investment of $0.5 million); or a combination of concessions (3 contracts; recorded investment of $3.0 million). (2) Represents the following concessions: extension of term (31 contracts; recorded investment of $48.4 million); reduced payment and/or payment deferral (11 contracts; recorded investment of $23.8 million); or a combination of concessions (5 contracts; recorded investment of $0.9 million). (3) Represents the following concessions: extension of term (3 contracts; recorded investment of $4.2 million); reduced payment and/or payment deferral (16 contracts; recorded investment of $17.6 million); or a combination of concessions (12 contracts; recorded investment of $9.8 million). (4) Represents the following concessions: loans restructured through bankruptcy (21 contracts; recorded investment of $3.7 million); reduced payment and/or payment deferral (10 contracts; recorded investment of $3.5 million); or a combination of concessions (7 contracts; recorded investment of $2.3 million). (5) Represents the following concessions: loans restructured through bankruptcy (49 contracts; recorded investment of $3.6 million); reduced payment and/or payment deferral (10 contracts; recorded investment of $1.3 million); or a combination of concessions (20 contracts; recorded investment of $2.4 million).
Summary of Recorded Investments in TDRs by Class of Loan, Subsequently Defaulted	The following is a summary, by class of loan, of information related to TDRs completed within the previous 12 months that subsequently defaulted during the years ended December 31, 2019 and 2018. For purposes of this disclosure, the previous 12 months is measured from January 1 of the respective prior year and a default represents a previously-modified loan that became past due 30 days or more during 2019 or 2018. 2019 2018 Years ended December 31 (dollars in millions) Number of Recorded Number of Recorded Commercial: Commercial real estate — $ — — $ — Commercial and industrial 2 2.4 12 6.7 Equipment financing 8 5.3 6 3.5 Total 10 7.7 18 10.2 Retail: Residential mortgage 5 2.2 7 1.6 Home equity 12 1.0 13 0.7 Other consumer — — — — Total 17 3.2 20 2.3 Total 27 $ 10.9 38 $ 12.5
Summary of Individually-Evaluated Impaired Loans by Class of Loan	People’s United’s impaired loans consist of certain loans that have been placed on non-accrual status, including all TDRs. The following table summarizes, by class of loan, information related to individually-evaluated impaired loans. 2019 2018 As of December 31 (in millions) Unpaid Recorded Related Unpaid Recorded Related Without a related allowance for loan losses: Commercial: Commercial real estate $ 28.9 $ 25.9 $ — $ 31.0 $ 28.1 $ — Commercial and industrial 31.0 25.9 — 45.6 42.0 — Equipment financing 24.1 21.8 — 20.2 18.0 — Retail: Residential mortgage 68.4 60.8 — 66.8 59.3 — Home equity 26.0 23.0 — 23.8 20.3 — Other consumer — — — — — — Total $ 178.4 $ 157.4 $ — $ 187.4 $ 167.7 $ — With a related allowance for loan losses: Commercial: Commercial real estate $ 21.5 $ 21.0 $ 3.4 $ 23.8 $ 21.8 $ 1.6 Commercial and industrial 20.0 16.4 3.9 12.6 10.2 2.4 Equipment financing 12.4 11.6 1.7 16.2 12.8 2.7 Retail: Residential mortgage 11.6 11.5 1.5 8.8 8.8 1.7 Home equity 1.4 1.4 0.7 1.7 1.6 0.7 Other consumer — — — — — — Total $ 66.9 $ 61.9 $ 11.2 $ 63.1 $ 55.2 $ 9.1 Total impaired loans: Commercial: Commercial real estate $ 50.4 $ 46.9 $ 3.4 $ 54.8 $ 49.9 $ 1.6 Commercial and industrial 51.0 42.3 3.9 58.2 52.2 2.4 Equipment financing 36.5 33.4 1.7 36.4 30.8 2.7 Total 137.9 122.6 9.0 149.4 132.9 6.7 Retail: Residential mortgage $ 80.0 $ 72.3 $ 1.5 $ 75.6 $ 68.1 $ 1.7 Home equity 27.4 24.4 0.7 25.5 21.9 0.7 Other consumer — — — — — — Total 107.4 96.7 2.2 101.1 90.0 2.4 Total $ 245.3 $ 219.3 $ 11.2 $ 250.5 $ 222.9 $ 9.1
Schedule of Impaired Financing Receivable	The following table summarizes, by class of loan, the average recorded investment and interest income recognized on impaired loans for the periods indicated. The average recorded investment amounts are based on month-end balances. 2019 2018 2017 Years ended December 31 (in millions) Average Interest Average Interest Average Interest Commercial: Commercial real estate $ 39.6 $ 1.1 $ 40.2 $ 1.1 $ 55.8 $ 1.2 Commercial and industrial 44.5 1.6 49.6 2.8 63.4 1.9 Equipment financing 27.0 0.3 38.4 0.1 44.4 0.4 Total 111.1 3.0 128.2 4.0 163.6 3.5 Retail: Residential mortgage 68.3 2.1 68.7 1.9 71.8 1.7 Home equity 23.0 0.6 20.9 0.5 21.2 0.4 Other consumer — — — — — — Total 91.3 2.7 89.6 2.4 93.0 2.1 Total $ 202.4 $ 5.7 $ 217.8 $ 6.4 $ 256.6 $ 5.6
Summary of Aging Information by Class of Loan	The following tables summarize, by class of loan, aging information for originated loans: Past Due As of December 31, 2019 (in millions) Current 30-89 90 Days Total Total Commercial: Commercial real estate $ 9,983.5 $ 7.8 $ 21.2 $ 29.0 $ 10,012.5 Commercial and industrial 9,738.0 10.5 14.6 25.1 9,763.1 Equipment financing 4,591.4 94.7 20.0 114.7 4,706.1 Total 24,312.9 113.0 55.8 168.8 24,481.7 Retail: Residential mortgage 6,534.3 31.6 23.0 54.6 6,588.9 Home equity 1,615.0 5.0 5.1 10.1 1,625.1 Other consumer 39.5 0.2 — 0.2 39.7 Total 8,188.8 36.8 28.1 64.9 8,253.7 Total originated loans $ 32,501.7 $ 149.8 $ 83.9 $ 233.7 $ 32,735.4 Past Due As of December 31, 2018 (in millions) Current 30-89 90 Days Total Total Commercial: Commercial real estate $ 9,762.1 $ 23.0 $ 13.4 $ 36.4 $ 9,798.5 Commercial and industrial 8,261.5 6.9 23.9 30.8 8,292.3 Equipment financing 3,855.3 68.8 13.6 82.4 3,937.7 Total 21,878.9 98.7 50.9 149.6 22,028.5 Retail: Residential mortgage 6,723.2 38.6 27.4 66.0 6,789.2 Home equity 1,776.0 5.8 7.7 13.5 1,789.5 Other consumer 42.7 0.1 — 0.1 42.8 Total 8,541.9 44.5 35.1 79.6 8,621.5 Total originated loans $ 30,420.8 $ 143.2 $ 86.0 $ 229.2 $ 30,650.0
Summary of Credit Quality Indicators by Class of Loan	The following tables summarize, by class of loan, credit quality indicators: As of December 31, 2019 (in millions) Commercial Commercial Equipment Total Commercial: Originated loans: Pass $ 9,736.4 $ 9,223.5 $ 4,231.6 $ 23,191.5 Special mention 197.6 294.8 76.5 568.9 Substandard 75.4 242.7 398.0 716.1 Doubtful 3.1 2.1 — 5.2 Total originated loans 10,012.5 9,763.1 4,706.1 24,481.7 Acquired loans: Pass 4,485.9 1,168.2 201.9 5,856.0 Special mention 136.7 35.6 — 172.3 Substandard 127.2 73.1 2.4 202.7 Doubtful — 1.6 — 1.6 Total acquired loans 4,749.8 1,278.5 204.3 6,232.6 Total $ 14,762.3 $ 11,041.6 $ 4,910.4 $ 30,714.3 As of December 31, 2019 (in millions) Residential Home Other Total Retail: Originated loans: Low risk $ 3,225.3 $ 747.3 $ 24.9 $ 3,997.5 Moderate risk 2,649.0 548.5 5.9 3,203.4 High risk 714.6 329.3 8.9 1,052.8 Total originated loans 6,588.9 1,625.1 39.7 8,253.7 Acquired loans: Low risk 1,184.7 — — 1,184.7 Moderate risk 2,309.3 — — 2,309.3 High risk 235.2 781.4 117.5 1,134.1 Total acquired loans 3,729.2 781.4 117.5 4,628.1 Total $ 10,318.1 $ 2,406.5 $ 157.2 $ 12,881.8 As of December 31, 2018 (in millions) Commercial Commercial Equipment Total Commercial: Originated loans: Pass $ 9,607.0 $ 7,855.7 $ 3,549.3 $ 21,012.0 Special mention 105.5 196.9 92.1 394.5 Substandard 85.2 239.3 296.3 620.8 Doubtful 0.8 0.4 — 1.2 Total originated loans 9,798.5 8,292.3 3,937.7 22,028.5 Acquired loans: Pass 1,766.2 719.6 394.0 2,879.8 Special mention 27.3 14.6 4.7 46.6 Substandard 57.6 62.4 2.8 122.8 Doubtful — — — — Total acquired loans 1,851.1 796.6 401.5 3,049.2 Total $ 11,649.6 $ 9,088.9 $ 4,339.2 $ 25,077.7 As of December 31, 2018 (in millions) Residential Home Other Total Retail: Originated loans: Low risk $ 2,912.8 $ 834.5 $ 27.3 $ 3,774.6 Moderate risk 3,360.9 576.4 5.9 3,943.2 High risk 515.5 378.6 9.6 903.7 Total originated loans 6,789.2 1,789.5 42.8 8,621.5 Acquired loans: Low risk 506.1 — — 506.1 Moderate risk 639.6 — — 639.6 High risk 219.3 173.0 4.2 396.5 Total acquired loans 1,365.0 173.0 4.2 1,542.2 Total $ 8,154.2 $ 1,962.5 $ 47.0 $ 10,163.7
Summarized Activity in Accretable Yield for PCI Loan Portfolio	The following table summarizes activity in the accretable yield for the PCI loan portfolio: Years ended December 31 (in millions) 2019 2018 2017 Balance at beginning of period $ 189.7 $ 219.7 $ 255.4 Acquisitions 25.5 27.1 13.1 Accretion (21.0) (24.6) (29.1) Reclassification from nonaccretable difference for loans with improved cash flows (1) — — — Other changes in expected cash flows (2) (56.7) (32.5) (19.7) Balance at end of period $ 137.5 $ 189.7 $ 219.7 (1) Results in increased interest accretion as a prospective yield adjustment over the remaining life of the corresponding pool of loans. (2) Represents changes in cash flows expected to be collected due to factors other than credit (e.g. changes in prepayment assumptions and/or changes in interest rates on variable rate loans), as well as loan sales, modifications and payoffs.

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Composition of Total Net Investment in Lease Financing Receivables	The composition of the Company’s total net investment in lease financing receivables included within equipment financing loans in the Consolidated Statements of Condition was as follows: (in millions) December 31, 2019 Lease payments receivable $ 1,417.1 Estimated residual value of leased assets 128.0 Gross investment in lease financing receivables 1,545.1 Plus: Deferred origination costs 13.4 Less: Unearned income (156.9) Total net investment in lease financing receivables $ 1,401.6
Contractual Maturities of Lease Financing Receivables	The contractual maturities of the Company's lease financing receivables were as follows: (in millions) December 31, 2019 2020 $ 518.8 2021 414.2 2022 303.3 2023 178.5 2024 93.6 Later years 36.7 Total $ 1,545.1
Lease Costs	The following tables provide the components of lease cost and supplemental information: For the Year Ended (in millions) December 31, 2019 Operating lease cost $ 61.6 Variable lease cost 8.6 Finance lease cost 0.1 Sublease income (1.4) Net lease cost $ 68.9
Lease Right-of-use Assets and Liabilities	(dollars in millions) As of and for the Year Lease ROU assets: Operating lease $ 276.6 Finance lease 2.6 Lease liabilities: Operating lease $ 307.9 Finance lease 5.3 Cash payments included in the measurement of lease liabilities: Reported in operating cash from operating leases 61.7 Reported in financing cash from finance leases 0.1 ROU assets obtained in exchange for lessee: Operating lease liabilities (1) 89.1 Finance lease liabilities (1) 2.6 Weighted-average discount rate: Operating leases 3.13 % Finance leases 2.58 Weighted-average remaining lease term (in years): Operating leases 7.7 Finance leases 12.2 1. Amount excludes related transition adjustment (see Note 1).
Schedule of Contractual Maturities of Lease Liabilities	The contractual maturities of the Company's lease liabilities as of December 31, 2019 were as follows: (in millions) Operating Leases Finance Leases 2020 $ 66.6 $ 0.5 2021 63.9 0.5 2022 46.3 0.5 2023 33.9 0.5 2024 28.3 0.5 Later years 111.8 3.7 Total lease payments 350.8 6.2 Less: Interest (42.9) (0.9) Total lease liabilities $ 307.9 $ 5.3

Goodwill and Other Acquisitio_2

Goodwill and Other Acquisition-Related Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Changes in Carrying Amount of Goodwill	Changes in the carrying amount of People’s United’s goodwill are summarized as follows: Operating Segment (in millions) Commercial Retail Wealth Total Balance at December 31, 2017 $ 1,600.3 $ 720.1 $ 91.0 $ 2,411.4 Acquisition of: First Connecticut 135.2 115.2 — 250.4 Vend Lease 23.9 — — 23.9 Balance at December 31, 2018 1,759.4 835.3 91.0 2,685.7 Acquisition of: United Financial 120.5 83.8 — 204.3 BSB Bancorp 49.3 95.6 — 144.9 VAR 37.5 — — 37.5 Write-down relating to the sale of branches (1) (0.6) (3.8) (2.5) (6.9) Balance at December 31, 2019 $ 1,966.1 $ 1,010.9 $ 88.5 $ 3,065.5
Other Acquisition-Related Intangible	The following is a summary of People’s United’s other acquisition-related intangible assets: 2019 2018 As of December 31 (in millions) Gross Accumulated Carrying Gross Accumulated Carrying Intangibles amortized: Core deposit intangible $ 303.9 $ 177.3 $ 126.6 $ 222.9 $ 157.4 $ 65.5 Trade name intangible 123.9 73.4 50.5 123.9 64.8 59.1 Client relationships 24.4 6.4 18.0 24.4 4.4 20.0 Trust relationships 42.7 35.1 7.6 42.7 31.3 11.4 Insurance relationships 38.1 34.3 3.8 38.1 33.6 4.5 Favorable lease agreements 2.9 0.6 2.3 2.9 0.3 2.6 Non-compete agreements 0.6 0.3 0.3 0.6 0.2 0.4 Total $ 536.5 $ 327.4 209.1 $ 455.5 $ 292.0 163.5 Mutual fund management contracts — 16.5 Total other acquisition-related $ 209.1 $ 180.0

Premises and Equipment (Tables)

Premises and Equipment (Tables)	12 Months Ended
	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Components of Premises and Equipment	The components of premises and equipment are summarized below: As of December 31 (in millions) 2019 2018 Land $ 49.8 $ 50.1 Buildings 330.6 300.0 Leasehold improvements 197.4 170.7 Furniture and equipment 324.3 279.3 Total 902.1 800.1 Less: Accumulated depreciation and amortization 596.6 532.8 Total premises and equipment, net $ 305.5 $ 267.3

Other Assets and Other Liabil_2

Other Assets and Other Liabilities (Tables)	12 Months Ended
	Dec. 31, 2019
Other Assets And Other Liabilities [Abstract]
Components of Other Assets	The components of other assets are as follows: As of December 31 (in millions) 2019 2018 Affordable housing investments (note 13) $ 383.9 $ 304.1 Fair value of derivative financial instruments (notes 20 and 22) 341.0 103.0 Lease ROU assets (note 6) 279.2 — Leased equipment 191.3 189.0 Accrued interest receivable 156.1 138.2 Funded status of defined benefit pension plans (note 18) 121.4 78.0 Loan disbursements in process 65.8 17.9 Current income tax receivable (note 13) 51.7 31.4 Assets held in trust for supplemental retirement plans (note 18) 51.0 56.4 Net deferred tax asset (note 13) 33.6 11.4 Other prepaid expenses 32.6 27.5 Economic development investments 29.2 26.2 Investment in joint venture 16.3 17.2 Receivables arising from securities brokerage and insurance businesses 13.0 26.4 REO: Residential 11.9 5.5 Commercial 7.3 8.7 Mortgage servicing rights 10.6 — Repossessed assets 4.2 3.9 Other 52.9 46.8 Total other assets $ 1,853.0 $ 1,091.6
Components of Other Liabilities	The components of other liabilities are as follows: As of December 31 (in millions) 2019 2018 Lease liabilities (note 6) $ 313.2 $ — Future contingent commitments for affordable housing investments (note 13) 141.1 119.7 Accrued expenses payable 104.3 87.9 Fair value of derivative financial instruments (notes 20 and 22) 96.2 139.0 Liabilities for supplemental retirement plans (note 18) 84.4 86.6 Accrued employee benefits 74.8 66.6 Accrued interest payable 21.7 25.4 Loan payments in process 18.8 51.2 Other postretirement plans (note 18) 18.7 15.3 Payables arising from securities brokerage and insurance businesses 9.6 29.7 Other 22.7 73.8 Total other liabilities $ 905.5 $ 695.2

Deposits (Tables)

Deposits (Tables)	12 Months Ended
	Dec. 31, 2019
Banking and Thrift [Abstract]
Schedule of Deposits	The following is an analysis of People’s United’s total deposits by product type: 2019 2018 As of December 31 (dollars in millions) Amount Weighted- Amount Weighted- Non-interest-bearing $ 9,803.7 — % $ 8,543.0 — % Savings 4,987.7 0.23 4,116.5 0.09 Interest-bearing checking and money market 19,592.6 0.92 16,583.3 1.04 Time deposits maturing: Within 3 months $ 3,984.7 1.90 1,480.0 1.66 After 3 but within 6 months 2,659.3 2.12 1,375.6 1.67 After 6 months but within 1 year 1,354.8 1.77 2,511.5 1.83 After 1 but within 2 years 816.3 1.82 1,275.5 1.98 After 2 but within 3 years 275.4 2.23 153.5 1.97 After 3 but within 4 years 97.8 2.37 102.1 1.63 After 4 but within 5 years 17.2 1.09 18.0 1.29 After 5 years (1) — 0.99 — 1.01 Total 9,205.5 1.95 6,916.2 1.78 Total deposits $ 43,589.5 0.85 % $ 36,159.0 0.83 % (1) Amount totaled less than $0.1 million at both December 31, 2019 and 2018.
Schedule of Interest Expense on Deposits	Interest expense on deposits is summarized as follows: Years ended December 31 (in millions) 2019 2018 2017 Savings $ 13.4 $ 7.2 $ 9.7 Interest-bearing checking and money market 195.9 120.2 70.4 Time 147.6 88.7 50.6 Total $ 356.9 $ 216.1 $ 130.7

Borrowings (Tables)

Borrowings (Tables)	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Summary of Borrowings	People’s United’s borrowings are summarized as follows: 2019 2018 As of December 31 (dollars in millions) Amount Weighted- Amount Weighted- Fixed-rate FHLB advances maturing: Within 1 month $ 3,060.8 1.79 % $ 2,270.3 2.59 % After 1 month but within 1 year 44.8 1.79 61.0 1.76 After 1 but within 2 years 6.8 2.11 54.2 1.75 After 2 but within 3 years 1.2 0.51 6.8 2.11 After 3 but within 4 years 0.6 0.05 1.3 0.52 After 4 but within 5 years — — 0.6 0.05 After 5 years 11.2 1.50 10.3 1.64 Total FHLB advances 3,125.4 1.79 2,404.5 2.54 Federal funds purchased maturing: Within 1 month 1,620.0 1.61 845.0 2.53 Total federal funds purchased 1,620.0 1.61 845.0 2.53 Customer repurchase agreements maturing: Within 1 month 409.1 0.69 332.9 0.61 Total customer repurchase agreements 409.1 0.69 332.9 0.61 Other borrowings maturing: Within 1 year — — 11.0 2.40 Total other borrowings — — 11.0 2.40 Total borrowings $ 5,154.5 1.64 % $ 3,593.4 2.36 %
Interest Expense on Borrowings	Interest expense on borrowings consists of the following: Years ended December 31 (in millions) 2019 2018 2017 FHLB advances $ 50.1 $ 54.5 $ 31.5 Federal funds purchased 24.6 13.6 7.1 Customer repurchase agreements 2.2 1.0 0.6 Other borrowings 0.1 1.8 2.1 Total $ 77.0 $ 70.9 $ 41.3
Information Concerning Parent Company Borrowings	Information concerning People’s United’s borrowings is presented below: As of and for the years ended December 31 (dollars in millions) 2019 2018 2017 FHLB advances: Balance at year end $ 3,125.4 $ 2,404.5 $ 2,774.4 Average outstanding during the year 2,098.0 2,653.6 2,677.5 Maximum outstanding at any month end 3,125.5 3,510.1 3,130.8 Average interest rate during the year 2.39 % 2.05 % 1.17 % Federal funds purchased: Balance at year end $ 1,620.0 $ 845.0 $ 820.0 Average outstanding during the year 1,127.5 682.2 643.5 Maximum outstanding at any month end 1,665.0 855.0 820.0 Average interest rate during the year 2.18 % 2.00 % 1.11 % Customer repurchase agreements: Balance at year end $ 409.1 $ 332.9 $ 301.6 Carrying amount of collateral securities at year end 418.0 342.3 307.7 Average outstanding during the year 296.6 252.7 311.0 Maximum outstanding at any month end 409.1 332.9 331.6 Average interest rate during the year 0.75 % 0.40 % 0.19 % Other borrowings: Balance at year end $ — $ 11.0 $ 207.8 Average outstanding during the year 3.3 104.5 132.0 Maximum outstanding at any month end 10.4 207.6 237.4 Average interest rate during the year 1.87 % 1.66 % 1.60 %

Notes and Debentures (Tables)

Notes and Debentures (Tables)	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Schedule of Subordinated Borrowing	Notes and debentures are summarized as follows: As of December 31 (in millions) 2019 2018 People’s United Financial, Inc.: 3.65% senior notes due 2022 $ 498.3 $ 497.7 5.75% subordinated notes due 2024 81.6 — People’s United Bank: 4.00% subordinated notes due 2024 413.2 398.1 Total notes and debentures $ 993.1 $ 895.8

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Summary of Total Income Tax Expense	The following is a summary of total income tax expense: Years ended December 31 (in millions) 2019 2018 2017 Income tax expense applicable to pre-tax income $ 132.0 $ 108.2 $ 129.9 Deferred income tax expense (benefit) applicable to items reported in 27.2 (12.2) 8.3 Total $ 159.2 $ 96.0 $ 138.2
Income Tax Effects Related to Items Recognized in Other Comprehensive Income	The components of income tax expense applicable to pre-tax income are summarized as follows: Years ended December 31 (in millions) 2019 2018 2017 Current tax expense: Federal $ 90.8 $ 83.0 $ 88.9 State 26.9 23.3 15.2 Total current tax expense 117.7 106.3 104.1 Deferred tax expense (1) 14.3 1.9 25.8 Total income tax expense $ 132.0 $ 108.2 $ 129.9 (1) Includes the effect of (decreases) increases in the valuation allowance for state deferred tax assets of $(7.7) million, $0.3 million and $(0.6) million in 2019, 2018 and 2017, respectively.
Summary of Income Tax Reconciliation	The following is a reconciliation of expected income tax expense, computed at the U.S. federal statutory rate of 21% in both 2019 and 2018, and 35% in 2017, to actual income tax expense: 2019 2018 2017 Years ended December 31 (dollars in millions) Amount Rate Amount Rate Amount Rate Expected income tax expense $ 137.0 21.0 % $ 121.0 21.0 % $ 163.5 35.0 % State income tax, net of federal tax effect 22.6 3.4 23.2 4.1 12.2 2.6 Non-deductible FDIC insurance premiums 4.4 0.7 6.5 1.1 — — Tax-exempt interest (21.4) (3.3) (19.4) (3.4) (26.6) (5.7) Federal income tax credits (12.7) (2.0) (12.3) (2.1) (11.6) (2.5) Tax-exempt income from BOLI (2.2) (0.3) (1.5) (0.3) (2.2) (0.5) Tax benefits recognized in connection with: The Tax Cuts and Jobs Act — — (9.2) (1.6) (6.5) (1.4) Equity-based compensation (0.1) — (1.3) (0.2) (1.1) (0.2) Other, net 4.4 0.7 1.2 0.2 2.2 0.5 Actual income tax expense $ 132.0 $ 108.2 $ 129.9 Effective income tax rate 20.2 % 18.8 % 27.8 %
Deferred Tax Assets and Liabilities	The tax effects of temporary differences that give rise to People’s United’s deferred tax assets and liabilities are as follows: As of December 31 (in millions) 2019 2018 Deferred tax assets: State tax net operating loss carryforwards, net of federal tax effect $ 71.8 $ 79.4 Allowance for loan losses and non-accrual interest 65.5 62.3 Acquisition-related deferred tax assets 30.5 13.3 Tax credits and net operating loss carryforwards 24.7 — Equity-based compensation 18.1 15.6 ROU lease assets, net of lease liabilities 7.5 — D.C. Solar investment basis difference 6.8 — Unrealized loss on debt securities transferred to held-to-maturity 3.6 4.7 Unrealized loss on debt securities available-for-sale — 15.4 Other deductible temporary differences 28.2 28.5 Total deferred tax assets 256.7 219.2 Less: valuation allowance for state deferred tax assets (72.4) (80.1) Total deferred tax assets, net of the valuation allowance 184.3 139.1 Deferred tax liabilities: Leasing activities (92.7) (82.0) Pension and other postretirement benefits (20.0) (9.7) Book over tax income recognized on consumer loans (18.0) (17.5) Unrealized gain on debt securities available-for-sale (6.6) — Mark-to-market and original issue discounts for tax purposes (5.2) (10.4) Temporary differences related to merchant services joint venture (3.5) (3.7) Other taxable temporary differences (4.7) (4.4) Total deferred tax liabilities (150.7) (127.7) Net deferred tax asset $ 33.6 $ 11.4
Unrecognized Income Tax Benefits	The following is a reconciliation of the beginning and ending balances of People's United’s unrecognized income tax benefits related to uncertain tax positions: Years ended December 31 (in millions) 2019 2018 2017 Balance at beginning of year $ 5.2 $ 2.7 $ 2.8 Additions for tax positions taken in prior years 0.5 2.5 0.1 Additions related to D.C. Solar: Established by United Financial prior to acquisition 8.7 — — Established by People's United subsequent to acquisition 18.9 — — Reductions attributable to audit settlements/lapse of statute of limitations — — (0.2) Balance at end of year $ 33.3 $ 5.2 $ 2.7

Regulatory Capital Requiremen_2

Regulatory Capital Requirements (Tables)	12 Months Ended
	Dec. 31, 2019
Banking and Thrift [Abstract]
Regulatory Capital Requirements	The following is a summary of People's United’s and the Bank's regulatory capital amounts and ratios under the Basel III capital rules. The minimum capital required amounts as of December 31, 2019 and 2018 are based on the capital conservation buffer phase-in provisions (as applicable for each year) of the Basel III capital rules. In connection with the adoption of the Basel III capital rules, both the Company and the Bank elected to opt-out of the requirement to include most components of AOCL in CET 1 capital. At December 31, 2019, both People's United's and the Bank's total risk-weighted assets, as defined, were $45.2 billion, compared to $35.9 billion for both at December 31, 2018. As of December 31, 2019 Minimum Capital Classification as (dollars in millions) Amount Ratio Amount Ratio Amount Ratio Tier 1 Leverage Capital (1): People’s United $ 4,846.1 9.1 % $ 2,119.7 4.0 % N/A N/A Bank 4,902.0 9.3 2,119.1 4.0 $ 2,648.8 5.0 % CET 1 Risk-Based Capital (2): People’s United 4,602.1 10.2 3,164.5 7.0 N/A N/A Bank 4,902.0 10.9 3,162.2 7.0 2,936.3 6.5 Tier 1 Risk-Based Capital (3): People’s United 4,846.1 10.7 3,842.6 8.5 2,712.5 6.0 Bank 4,902.0 10.9 3,839.8 8.5 3,614.0 8.0 Total Risk-Based Capital (4): People’s United 5,435.6 12.0 4,746.8 10.5 4,520.8 10.0 Bank 5,474.2 12.1 4,743.3 10.5 4,517.4 10.0 As of December 31, 2018 Minimum Capital Classification as (dollars in millions) Amount Ratio Amount Ratio Amount Ratio Tier 1 Leverage Capital (1): People’s United $ 3,927.2 8.7 % $ 1,806.0 4.0 % N/A N/A Bank 4,076.0 9.0 1,805.4 4.0 $ 2,256.8 5.0 % CET 1 Risk-Based Capital (2): People’s United 3,683.1 10.3 2,289.3 6.375 N/A N/A Bank 4,076.0 11.4 2,287.1 6.375 2,331.9 6.5 Tier 1 Risk-Based Capital (3): People’s United 3,927.2 10.9 2,827.9 7.875 2,154.6 6.0 Bank 4,076.0 11.4 2,825.2 7.875 2,870.0 8.0 Total Risk-Based Capital (4): People’s United 4,505.7 12.5 3,546.1 9.875 3,591.0 10.0 Bank 4,719.1 13.2 3,542.7 9.875 3,587.5 10.0 (1) Tier 1 Leverage Capital ratio represents CET 1 Capital plus Additional Tier 1 Capital instruments (together, "Tier 1 Capital") divided by Average Total Assets (less goodwill, other acquisition-related intangibles and other deductions from CET 1 Capital). (2) CET 1 Risk-Based Capital ratio represents equity capital, as defined, less: (i) after-tax net unrealized gains (losses) on certain securities classified as available-for-sale; (ii) after-tax net unrealized gains (losses) on securities transferred to held-to-maturity; (iii) goodwill and other acquisition-related intangible assets; and (iv) the amount recorded in AOCL relating to pension and other postretirement benefits divided by Total Risk-Weighted Assets. (3) Tier 1 Risk-Based Capital ratio represents Tier 1 Capital divided by Total Risk-Weighted Assets. (4) Total Risk-Based Capital ratio represents Tier 1 Capital plus subordinated notes and debentures, up to certain limits, and the allowance for loan losses, up to 1.25% of Total Risk-Weighted Assets, divided by Total Risk-Weighted Assets.

Earnings Per Common Share (Tabl

Earnings Per Common Share (Tables)	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Basic and Diluted Earnings Per Common Share, Reflecting Application of Two-Class Method	The following is an analysis of People’s United’s basic and diluted EPS, reflecting the application of the two-class method, as described in Note 1: Years ended December 31 (in millions, except per common share data) 2019 2018 2017 Net income available to common shareholders $ 506.3 $ 454.0 $ 323.1 Dividends paid on and undistributed earnings allocated to participating securities (0.2) (0.2) (0.5) Earnings attributable to common shareholders $ 506.1 $ 453.8 $ 322.6 Weighted average common shares outstanding for basic EPS 394.0 348.1 330.3 Effect of dilutive equity-based awards 3.2 3.6 2.6 Weighted average common shares and common-equivalent shares for diluted EPS 397.2 351.7 332.9 EPS: Basic $ 1.28 $ 1.30 $ 0.98 Diluted 1.27 1.29 0.97

Comprehensive Income (Tables)

Comprehensive Income (Tables)	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Schedule of Accumulated Other Comprehensive Loss	The following is a summary of the changes in the components of AOCL, which are included in People’s United’s stockholders’ equity on an after-tax basis: (in millions) Pension Net Unrealized Net Unrealized Net Unrealized Total Balance at December 31, 2016 $ (145.6) $ (32.3) $ (17.4) $ 0.3 $ (195.0) Other comprehensive income (loss) (2.8) (5.3) — (0.6) (8.7) Amounts reclassified from AOCL (1) 4.3 16.0 2.3 (0.6) 22.0 Current period other comprehensive 1.5 10.7 2.3 (1.2) 13.3 Balance at December 31, 2017 (144.1) (21.6) (15.1) (0.9) (181.7) Other comprehensive income (loss) (24.7) (29.0) — (1.3) (55.0) Amounts reclassified from AOCL (1) 6.3 7.5 3.0 0.4 17.2 Current period other comprehensive (18.4) (21.5) 3.0 (0.9) (37.8) Transition adjustments related to adoption (30.0) (3.9) (3.2) (0.2) (37.3) Balance at December 31, 2018 (192.5) (47.0) (15.3) (2.0) (256.8) Other comprehensive income (loss) 9.7 67.9 — 1.5 79.1 Amounts reclassified from AOCL (1) 6.6 (0.1) 3.5 0.8 10.8 Current period other comprehensive 16.3 67.8 3.5 2.3 89.9 Balance at December 31, 2019 $ (176.2) $ 20.8 $ (11.8) $ 0.3 $ (166.9) (1) See the following table for details about these reclassifications. (2) See Notes 1 and 4.
Summary of Amounts Reclassified from AOCL	The following is a summary of the amounts reclassified from AOCL: Years ended December 31 (in millions) Amounts Reclassified Affected Line Item 2019 2018 2017 Details about components of AOCL: Amortization of pension and Net actuarial loss $ (8.3) $ (8.6) $ (9.3) (1) Prior service credit — 0.3 0.8 (1) (8.3) (8.3) (8.5) Income before income tax expense 1.7 2.0 4.2 Income tax expense (6.6) (6.3) (4.3) Net income Reclassification adjustment for net 0.1 (9.9) (25.4) Income before income tax expense (2) — 2.4 9.4 Income tax expense 0.1 (7.5) (16.0) Net income Amortization of unrealized losses on (4.6) (3.9) (3.7) Income before income tax expense (3) 1.1 0.9 1.4 Income tax expense (3.5) (3.0) (2.3) Net income Amortization of unrealized gains and Interest rate swaps (1.2) (0.6) 0.8 (4) Interest rate locks 0.1 0.1 0.1 (4) (1.1) (0.5) 0.9 Income before income tax expense 0.3 0.1 (0.3) Income tax expense (0.8) (0.4) 0.6 Net income Total reclassifications for the period $ (10.8) $ (17.2) $ (22.0) (1) Included in the computation of net periodic benefit income (expense) reflected in other non-interest expense (see Note 17 for additional details). (2) Included in non-interest income. (3) Included in interest and dividend income — securities. (4) Included in interest expense — notes and debentures.
Deferred Income Taxes Applicable to Components of Accumulated Other Comprehensive Loss	Deferred income taxes applicable to the components of AOCL are as follows: As of December 31 (in millions) 2019 2018 2017 Net actuarial loss and other amounts related to pension and $ 55.3 $ 59.4 $ 83.5 Net unrealized (gain) loss on debt securities available-for-sale (6.6) 14.7 12.7 Net unrealized loss on debt securities transferred to held-to-maturity 3.6 4.7 8.8 Net unrealized (gain) loss on derivatives accounted for as cash flow hedges (0.1) 0.6 0.5 Total deferred income taxes $ 52.2 $ 79.4 $ 105.5
Other Comprehensive Income (Loss)	The following is a summary of the components of People’s United’s total other comprehensive income (loss): Year ended December 31, 2019 (in millions) Pre-Tax Tax Effect After-Tax Net actuarial gains and losses on pension and other postretirement plans: Net actuarial gain arising during the year $ 12.1 $ (2.4) $ 9.7 Reclassification adjustment for net actuarial loss included in net income 8.3 (1.7) 6.6 Net actuarial gain 20.4 (4.1) 16.3 Net unrealized gains and losses on debt securities available-for-sale: Net unrealized holding gains arising during the year 89.2 (21.3) 67.9 Reclassification adjustment for net realized losses included in net income (0.1) — (0.1) Net unrealized gains 89.1 (21.3) 67.8 Net unrealized gains and losses on debt securities transferred to held-to-maturity: Reclassification adjustment for amortization of unrealized losses on debt securities transferred to held-to-maturity included in net income 4.6 (1.1) 3.5 Net unrealized gains 4.6 (1.1) 3.5 Net unrealized gains and losses on derivatives accounted for as cash flow hedges: Net unrealized gains arising during the year 1.9 (0.4) 1.5 Reclassification adjustment for net realized losses included in net income 1.1 (0.3) 0.8 Net unrealized gains 3.0 (0.7) 2.3 Total other comprehensive income $ 117.1 $ (27.2) $ 89.9 Year ended December 31, 2018 (in millions) Pre-Tax Tax Effect After-Tax Net actuarial gains and losses on pension and other postretirement plans: Net actuarial loss arising during the year $ (32.6) $ 7.9 $ (24.7) Reclassification adjustment for net actuarial loss included in net income 8.6 (2.1) 6.5 Net actuarial loss (24.0) 5.8 (18.2) Prior service credit on pension and other postretirement plans: Reclassification adjustment for prior service credit included in net income (0.3) 0.1 (0.2) Net actuarial loss and prior service credit (24.3) 5.9 (18.4) Net unrealized gains and losses on debt securities available-for-sale: Net unrealized holding losses arising during the year (38.3) 9.3 (29.0) Reclassification adjustment for net realized losses included in net income 9.9 (2.4) 7.5 Net unrealized losses (28.4) 6.9 (21.5) Net unrealized gains and losses on debt securities transferred to held-to-maturity: Reclassification adjustment for amortization of unrealized losses on debt securities transferred to held-to-maturity included in net income 3.9 (0.9) 3.0 Net unrealized gains 3.9 (0.9) 3.0 Net unrealized gains and losses on derivatives accounted for as cash flow hedges: Net unrealized losses arising during the year (1.7) 0.4 (1.3) Reclassification adjustment for net realized losses included in net income 0.5 (0.1) 0.4 Net unrealized losses (1.2) 0.3 (0.9) Total other comprehensive loss $ (50.0) $ 12.2 $ (37.8) Year ended December 31, 2017 (in millions) Pre-Tax Tax Effect After-Tax Net actuarial gains and losses on pension and other postretirement plans: Net actuarial loss arising during the year $ (5.5) $ 2.7 $ (2.8) Reclassification adjustment for net actuarial loss included in net income 9.3 (4.6) 4.7 Net actuarial gain 3.8 (1.9) 1.9 Prior service credit on pension and other postretirement plans: Reclassification adjustment for prior service credit included in net income (0.8) 0.4 (0.4) Net actuarial gain and prior service credit 3.0 (1.5) 1.5 Net unrealized gains and losses on debt securities available-for-sale: Net unrealized holding losses arising during the year (8.6) 3.3 (5.3) Reclassification adjustment for net realized losses included in net income 25.4 (9.4) 16.0 Net unrealized gains 16.8 (6.1) 10.7 Net unrealized gains and losses on debt securities transferred to held-to-maturity: Reclassification adjustment for amortization of unrealized losses on debt securities transferred to held-to-maturity included in net income 3.7 (1.4) 2.3 Net unrealized gains 3.7 (1.4) 2.3 Net unrealized gains and losses on derivatives accounted for as cash flow hedges: Net unrealized losses arising during the year (1.0) 0.4 (0.6) Reclassification adjustment for net realized gains included in net income (0.9) 0.3 (0.6) Net unrealized losses (1.9) 0.7 (1.2) Total other comprehensive income $ 21.6 $ (8.3) $ 13.3

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2019
Retirement Benefits [Abstract]
Changes in Benefit Obligations and Plan Assets	The following table summarizes changes in the benefit obligations and plan assets of (i) the People’s Qualified Plan (including the Chittenden Qualified Plan and the Suffolk Qualified Plan), the First Connecticut Qualified Plan, the People's Supplemental Plans, the First Connecticut Supplemental Plan, the BSB Bancorp Supplemental Plan and the United Financial Supplemental Plan (together the “Pension Plans”) and (ii) the People’s Postretirement Plan, the First Connecticut Postretirement Plans, the BSB Bancorp Post Retirement Welfare (Life Insurance) Plan and the United Financial Postretirement Plan (together the “Other Postretirement Plans”). The table also shows the funded status (or the difference between benefit obligations and plan assets) recognized in the Consolidated Statements of Condition. All plans have a December 31 measurement date. Pension Plans Other (in millions) 2019 2018 2019 2018 Benefit obligations: (1) Beginning of year $ 562.7 $ 584.8 $ 15.3 $ 14.6 Service cost — — 0.3 0.3 Interest cost 22.9 20.2 0.6 0.5 Actuarial loss (gain) 80.2 (51.0) 1.2 (1.7) Benefits paid (28.2) (21.4) (0.7) (0.8) Settlements (13.1) (2.7) — — Acquisitions (2) 41.0 35.2 2.0 2.4 Plan revaluations (3) — (2.4) — — End of year 665.5 562.7 18.7 15.3 Fair value of plan assets: Beginning of year 596.4 584.9 — — Actual return on assets 138.6 (40.9) — — Employer contributions 18.7 52.7 0.7 0.8 Benefits paid (28.2) (21.4) (0.7) (0.8) Settlements (13.1) (2.7) — — Acquisitions (2) 34.3 23.8 — — End of year 746.7 596.4 — — Funded status at end of year $ 81.2 $ 33.7 $ (18.7) $ (15.3) Amounts recognized in the Consolidated Statements Other assets $ 121.4 $ 78.0 $ — $ — Other liabilities (40.2) (44.3) (18.7) (15.3) Funded status at end of year $ 81.2 $ 33.7 $ (18.7) $ (15.3) (1) Represents the projected benefit obligation for the Pension Plans and the accumulated benefit obligation for the Other Postretirement Plans. (2) Represents the benefit obligations and plan assets of the United Financial Qualified Plan and the United Financial Supplemental Plan as of November 1, 2019, the BSB Bancorp Supplemental Plan as of April 1, 2019, the First Connecticut Qualified Plan as of October 1, 2018, and the benefit obligations of the United Financial Postretirement Plan as of November 1, 2019, the BSB Bancorp Post Retirement Welfare (Life Insurance) Plan as of April 1, 2019 and the First Connecticut Postretirement Plans as of October 1, 2018 (3) Represents the revaluations of the Chittenden Qualified Plan and the Suffolk Qualified Plan, effective October 1, 2018, upon merging into the People’s Qualified Plan.
Accumulated and Projected Benefit Obligations	The following table summarizes the accumulated and projected benefit obligations for the Pension Plans at the respective measurement dates: Pension Plans As of December 31 (in millions) 2019 2018 Accumulated benefit obligations: Qualified Plans $ 625.3 $ 518.7 Supplemental Plans 40.0 43.6 Total $ 665.3 $ 562.3 Projected benefit obligations: Qualified Plans $ 625.3 $ 518.7 Supplemental Plans 40.2 44.0 Total $ 665.5 $ 562.7
Components of Net Periodic Benefit (Income) Expense and Other Amounts	Components of net periodic benefit (income) expense and other amounts recognized in other comprehensive income (loss) are as follows: Pension Plans Other Years ended December 31 (in millions) 2019 2018 2017 2019 2018 2017 Net periodic benefit (income) expense: Interest cost $ 22.9 $ 20.2 $ 19.1 $ 0.9 $ 0.8 $ 0.8 Expected return on plan assets (46.1) (44.3) (37.9) — — — Recognized net actuarial loss 5.3 7.3 6.5 0.1 0.3 0.2 Recognized prior service credit — (0.3) (0.8) — — — Settlements (1) 2.9 1.0 2.6 — — — Net periodic benefit (income) expense (15.0) (16.1) (10.5) 1.0 1.1 1.0 Other changes in plan assets and benefit obligations recognized in other comprehensive income (loss): Net actuarial (gain) loss (20.5) 26.0 (4.8) 1.1 (2.0) 1.0 Prior service credit — 0.3 0.8 — — — Total pre-tax changes recognized in other comprehensive income (loss) (20.5) 26.3 (4.0) 1.1 (2.0) 1.0 Total recognized in net periodic benefit (income) expense and other comprehensive income (loss) $ (35.5) $ 10.2 $ (14.5) $ 2.1 $ (0.9) $ 2.0 (1) Settlement charges are a result of lump-sum benefit payments in excess of the sum of a plan’s annual interest and service costs. When an employer settles the full amount of its obligation for vested benefits with respect to some of a plan’s participants, the employer is required to recognize in income a pro-rata portion of the aggregate gain or loss recorded in AOCL.
Pre-Tax Amounts in Accumulated Other Comprehensive Loss	The pre-tax amounts in AOCL that have not been recognized as components of net periodic benefit (income) expense are as follows: Pension Plans Other As of December 31 (in millions) 2019 2018 2019 2018 Net actuarial loss $ 228.5 $ 249.0 $ 3.9 $ 2.8 Total pre-tax amounts included in AOCL $ 228.5 $ 249.0 $ 3.9 $ 2.8
Assumptions Used in Determining Benefit Obligations and Net Periodic Benefit Expense	The following assumptions were used in determining the benefit obligations and net periodic benefit (income) expense as of and for the periods indicated: Qualified Plans Other Postretirement Plans 2019 2018 2017 2019 2018 2017 Weighted-average assumptions used to determine Discount rate: People’s Qualified Plan 3.38 % 4.41 % 3.74 % 3.40 % 4.40 % 3.70 % First Connecticut Qualified Plan 3.39 4.41 n/a n/a n/a n/a United Financial Qualified Plan 3.42 n/a n/a n/a n/a n/a Chittenden Qualified Plan (1) n/a n/a 3.62 n/a n/a n/a Suffolk Qualified Plan (1) n/a n/a 3.72 n/a n/a n/a Rate of compensation increase n/a n/a n/a n/a n/a n/a Weighted-average assumptions used to determine net Discount rate: People’s Qualified Plan (2) 4.41 % 3.74%/4.34% 4.41 % 4.40 % 3.70 % 4.40 % First Connecticut Qualified Plan 4.41 4.35 n/a n/a n/a n/a United Financial Qualified Plan 3.33 n/a n/a n/a n/a n/a Chittenden Qualified Plan (1) n/a n/a 4.16 n/a n/a n/a Suffolk Qualified Plan (1) n/a n/a 4.24 n/a n/a n/a Expected return on plan assets People’s Qualified Plan 7.25 7.25 7.25 n/a n/a n/a First Connecticut Qualified Plan 6.00 6.00 n/a n/a n/a n/a United Financial Qualified Plan 5.25 n/a n/a n/a n/a n/a Rate of compensation increase n/a n/a n/a n/a n/a n/a Assumed health care cost trend rates at December 31: Health care cost trend rate assumed for next year n/a n/a n/a 5.70 % 6.00 % 6.20 % Rate to which the cost trend rate is assumed to decline (the ultimate trend rate) n/a n/a n/a 4.50 4.50 4.50 Year that the rate reaches the ultimate trend rate n/a n/a n/a 2037 2037 2037 n/a — not applicable (1) Effective October 1, 2018, the Chittenden Qualified Plan and the Suffolk Qualified Plan were merged into the People’s Qualified Plan. (2) Rate of 3.74% through September 30, 2018 and 4.34% through December 31, 2018.
Asset Allocation	All investment decisions are governed by an established policy that contains the following asset allocation guidelines: Asset Class Policy Target % Policy Range % Cash equivalents 1 0-20 Equity securities 65 55-75 Fixed income securities 24 10-40
Fair Value of Assets in Qualified Plans	The following table summarizes the percentages of fair value for the major categories of assets in the Qualified Plans as of the respective measurement dates: Plan Assets 2019 2018 As of December 31 People’s First Connecticut United Financial People’s First Equity securities 66 % 66 % 9 % 70 % 73 % Cash and fixed income securities 34 34 91 30 27 Total 100 % 100 % 100 % 100 % 100 % (1) The United Financial Qualified Plan is not yet aligned with the Company's investment strategy and asset allocation guidelines as the acquisition of United Financial occurred effective November 1, 2019.
Plan Assets Measured at Fair Value	The following tables present the Qualified Plans’ assets measured at fair value: Fair Value Measurements Using As of December 31, 2019 (in millions) Level 1 Level 2 Level 3 Total Cash and cash equivalents $ 18.9 $ — $ — $ 18.9 Equity securities: Common stocks 261.2 — — 261.2 Mutual funds — 215.2 — 215.2 Fixed income securities: U.S. Treasury — 104.8 — 104.8 Corporate — 73.0 — 73.0 Mutual funds — 72.5 — 72.5 Other — 1.1 — 1.1 Total $ 280.1 $ 466.6 $ — $ 746.7 Fair Value Measurements Using As of December 31, 2018 (in millions) Level 1 Level 2 Level 3 Total Cash and cash equivalents $ 15.2 $ — $ — $ 15.2 Equity securities: Common stocks 216.6 — — 216.6 Mutual funds — 201.1 — 201.1 Fixed income securities: Corporate — 68.5 — 68.5 U.S. Treasury — 58.6 — 58.6 Mutual funds — 32.9 — 32.9 Other — 3.5 — 3.5 Total $ 231.8 $ 364.6 $ — $ 596.4

Stock-Based Compensation Plans

Stock-Based Compensation Plans (Tables)	12 Months Ended
	Dec. 31, 2019
Share-based Payment Arrangement [Abstract]
Summary of Performance Share Activity	The following is a summary of performance share activity under the 2014 Plan: Shares Weighted-Average Unvested performance shares outstanding at December 31, 2016 551,985 $ 15.22 Granted 466,923 18.61 Forfeited (34,073) 16.28 Unvested performance shares outstanding at December 31, 2017 984,835 16.80 Granted 532,740 19.78 Forfeited (62,124) 17.82 Vested (2,079) 16.70 Unvested performance shares outstanding at December 31, 2018 1,453,372 17.85 Granted 637,118 17.84 Forfeited (80,319) 18.66 Vested (505,755) 15.23 Unvested performance shares outstanding at December 31, 2019 1,504,416 $ 18.68
Stock Option Incentive Plan	The following is a summary of stock option activity under the Incentive Plans and the SOP: Shares Weighted-Average Weighted-Average Aggregate Options outstanding at December 31, 2016 16,555,925 $ 14.84 Granted 2,261,586 19.14 Forfeited (459,576) 17.87 Exercised (3,920,294) 15.97 Options outstanding at December 31, 2017 14,437,641 15.11 Granted 2,450,861 19.61 Forfeited (294,474) 17.87 Exercised (1,916,961) 14.55 Options outstanding at December 31, 2018 14,677,067 15.87 Granted 2,807,692 17.62 Forfeited (652,965) 18.28 Exercised (1,632,971) 14.77 Options outstanding at December 31, 2019 15,198,823 $ 16.20 6.2 $ 22.7 Options exercisable at December 31, 2019 10,551,014 $ 15.21 5.2 $ 22.7 (1) Reflects only those stock options with intrinsic value at December 31, 2019.
Options Outstanding and Options Exercisable	Additional information concerning options outstanding and options exercisable at December 31, 2019 is summarized as follows: Exercise Price Range Options Outstanding Options Exercisable Weighted-Average Number Remaining Exercise Number Weighted-Average $11.53 — $14.54 3,531,960 3.4 $ 13.53 3,525,520 $ 13.53 14.55 — 14.88 4,970,387 5.0 14.73 4,970,387 14.73 14.89 — 18.40 2,689,105 9.0 17.60 57,997 16.47 18.41 — 19.71 4,007,371 7.6 19.45 1,997,110 19.36
Restricted Stock Award Incentive Plan	The following is a summary of restricted stock award activity under the Incentive Plans and the RRP: Shares Weighted-Average Unvested restricted shares outstanding at December 31, 2016 886,082 $ 14.59 Granted 303,090 18.84 Forfeited (31,828) 15.56 Vested (485,023) 14.49 Unvested restricted shares outstanding at December 31, 2017 672,321 16.53 Granted 489,789 18.50 Forfeited (29,426) 17.81 Vested (402,134) 16.04 Unvested restricted shares outstanding at December 31, 2018 730,550 18.03 Granted 383,420 17.44 Forfeited (68,091) 17.11 Vested (347,078) 17.49 Unvested restricted shares outstanding at December 31, 2019 698,801 $ 18.07

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Assets and Liabilities Measured at Fair Value on Recurring Basis	The following tables summarize People’s United’s financial instruments that are measured at fair value on a recurring basis: Fair Value Measurements Using As of December 31, 2019 (in millions) Level 1 Level 2 Level 3 Total Financial assets: Trading debt securities: U.S. Treasury $ 7.1 $ — $ — $ 7.1 Debt securities available-for-sale: U.S. Treasury and agency 687.1 — — 687.1 GSE mortgage-backed and CMO securities — 2,877.2 — 2,877.2 Equity securities 8.2 — — 8.2 Other assets: Exchange-traded funds 47.7 — — 47.7 Mutual funds 3.3 — — 3.3 Interest rate swaps — 337.6 — 337.6 Interest rate caps — 1.7 — 1.7 Foreign exchange contracts — 1.2 — 1.2 Forward commitments to sell residential mortgage loans — 0.5 — 0.5 Total $ 753.4 $ 3,218.2 $ — $ 3,971.6 Financial liabilities: Interest rate swaps $ — $ 92.1 $ — $ 92.1 Interest rate caps — 1.7 — 1.7 Risk participation agreements — 0.1 — 0.1 Foreign exchange contracts — 1.8 — 1.8 Interest rate-lock commitments on residential mortgage loans — 0.5 — 0.5 Total $ — $ 96.2 $ — $ 96.2 Fair Value Measurements Using As of December 31, 2018 (in millions) Level 1 Level 2 Level 3 Total Financial assets: Trading debt securities: U.S. Treasury $ 8.4 $ — $ — $ 8.4 Debt securities available-for-sale: U.S. Treasury and agency 678.0 — — 678.0 GSE mortgage-backed securities — 2,443.0 — 2,443.0 Equity securities 8.1 — — 8.1 Other assets: Exchange-traded funds 35.5 — — 35.5 Mutual funds 20.6 — — 20.6 Fixed income securities — 0.3 — 0.3 Interest rate swaps — 98.9 — 98.9 Interest rate caps — 3.1 — 3.1 Foreign exchange contracts — 0.9 — 0.9 Forward commitments to sell residential mortgage loans — 0.1 — 0.1 Total $ 750.6 $ 2,546.3 $ — $ 3,296.9 Financial liabilities: Interest rate swaps $ — $ 135.0 $ — $ 135.0 Interest rate caps — 3.1 — 3.1 Risk participation agreements (1) — — — — Foreign exchange contracts — 0.8 — 0.8 Interest rate-lock commitments on residential mortgage loans — 0.1 — 0.1 Total $ — $ 139.0 $ — $ 139.0 (1) At December 31, 2018, the fair value of risk participation agreements totaled less than $0.1 million (see Note 22).
Assets Measured at Fair Value on Non-Recurring Basis	The following tables summarize People’s United’s assets that are measured at fair value on a non-recurring basis: Fair Value Measurements Using As of December 31, 2019 (in millions) Level 1 Level 2 Level 3 Total Loans held-for-sale: Commercial (1) $ — $ — $ 157.9 $ 157.9 Other consumer (1) — — 333.7 333.7 Residential (2) — 19.7 — 19.7 Impaired loans (3) — — 61.9 61.9 REO and repossessed assets (4) — — 23.4 23.4 Mortgage servicing rights (1) — — 10.3 10.3 Total $ — $ 19.7 $ 587.2 $ 606.9 Fair Value Measurements Using As of December 31, 2018 (in millions) Level 1 Level 2 Level 3 Total Loans held-for-sale - Residential (2) $ — $ 19.5 $ — $ 19.5 Impaired loans (3) — — 55.2 55.2 REO and repossessed assets (4) — — 18.1 18.1 Total $ — $ 19.5 $ 73.3 $ 92.8 (1) Fair value adjustments recorded for the year ended December 31, 2019 were immaterial. (2) No fair value adjustments were recorded for the years ended December 31, 2019 and 2018. (3) Represents the recorded investment in originated impaired loans with a related allowance for loan losses measured in accordance with applicable accounting guidance. The total consists of $49.0 million of Commercial loans and $12.9 million of Retail loans at December 31, 2019. The provision for loan losses on impaired loans totaled $9.3 million and $8.6 million for the years ended December 31, 2019 and 2018, respectively. (4) Represents: (i) $11.9 million of residential REO; (ii) $7.3 million of commercial REO; and (iii) $4.2 million of repossessed assets at December 31, 2019. Charge-offs to the allowance for loan losses related to loans that were transferred to REO or repossessed assets totaled $2.8 million and $1.7 million for the years ended December 31, 2019 and 2018, respectively. Write downs and net loss on sale of foreclosed/repossessed assets charged to non-interest expense totaled $1.1 million and $0.2 million for the same periods.
Carrying Amounts and Estimated Fair Values of Financial Instruments	The following tables summarize the carrying amounts, estimated fair values and placement in the fair value hierarchy of People’s United’s financial instruments that are not measured at fair value either on a recurring or non-recurring basis: Carrying Estimated Fair Value As of December 31, 2019 (in millions) Level 1 Level 2 Level 3 Total Financial assets: Cash and due from banks $ 484.2 $ 484.2 $ — $ — $ 484.2 Short-term investments 316.8 — 316.8 — 316.8 Debt securities held-to-maturity 3,869.2 — 4,018.5 1.5 4,020.0 FHLB and FRB stock 341.1 — 341.1 — 341.1 Total loans, net (1) 43,287.6 — 10,072.1 33,282.9 43,355.0 Financial liabilities: Time deposits 9,205.5 — 9,218.1 — 9,218.1 Other deposits 34,384.0 — 34,384.0 — 34,384.0 FHLB advances 3,125.4 — 3,125.5 — 3,125.5 Federal funds purchased 1,620.0 — 1,620.0 — 1,620.0 Customer repurchase agreements 409.1 — 409.1 — 409.1 Notes and debentures 993.1 — 1,021.3 — 1,021.3 (1) Excludes impaired loans totaling $61.9 million measured at fair value on a non-recurring basis. Carrying Estimated Fair Value As of December 31, 2018 (in millions) Level 1 Level 2 Level 3 Total Financial assets: Cash and due from banks $ 665.7 $ 665.7 $ — $ — $ 665.7 Short-term investments 266.3 — 266.3 — 266.3 Debt securities held-to-maturity 3,792.3 — 3,774.4 1.5 3,775.9 FHLB and FRB stock 303.4 — 303.4 — 303.4 Total loans, net (1) 34,945.8 — 7,806.1 26,800.2 34,606.3 Financial liabilities: Time deposits 6,916.2 — 6,884.0 — 6,884.0 Other deposits 29,242.8 — 29,242.8 — 29,242.8 FHLB advances 2,404.5 — 2,404.5 — 2,404.5 Federal funds purchased 845.0 — 845.0 — 845.0 Customer repurchase agreements 332.9 — 332.9 — 332.9 Other borrowings 11.0 — 11.0 — 11.0 Notes and debentures 895.8 — 893.4 — 893.4 (1) Excludes impaired loans totaling $55.2 million measured at fair value on a non-recurring basis.

Financial Instruments (Tables)

Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2019
Investments, All Other Investments [Abstract]
Summary of Contractual or Notional Amounts of Financial Instruments	A summary of the contractual or notional amounts of People’s United’s lending-related and derivative financial instruments follows: As of December 31 (in millions) 2019 2018 Lending-Related Financial Instruments: (1) Loan origination commitments and unadvanced lines of credit: Commercial and industrial $ 5,549.9 $ 4,937.1 Home equity and other consumer 3,401.9 2,646.6 Commercial real estate 1,614.9 1,095.4 Equipment financing 471.0 459.7 Residential mortgage 54.7 78.7 Letters of credit: Stand-by 185.2 139.4 Commercial 4.4 5.0 Derivative Financial Instruments: (2) Interest rate swaps: For market risk management 585.0 585.0 For commercial customers: Customer 8,847.7 7,455.9 Institutional counterparties 8,851.8 7,161.3 Interest rate caps: For commercial customers: Customer 246.0 329.1 Institutional counterparties 246.0 329.1 Risk participation agreements 882.8 576.5 Foreign exchange contracts 180.4 145.2 Forward commitments to sell residential mortgage loans 23.3 9.5 Interest rate-lock commitments on residential mortgage loans 33.6 13.6 (1) The contractual amounts of these financial instruments represent People’s United’s maximum potential exposure to credit loss, assuming: (i) the instruments are fully funded at a later date; (ii) the borrower does not meet contractual repayment obligations; and (iii) any collateral or other security proves to be worthless. (2) The contractual or notional amounts of these financial instruments are substantially greater than People’s United’s maximum potential exposure to credit loss.
Schedule of Notional Amounts and Fair Values of Derivatives Outstanding	The table below provides a summary of the notional amounts and fair values (presented on a gross basis) of derivatives outstanding: Fair Values (1) Type of Notional Amounts Assets Liabilities As of December 31 (in millions) 2019 2018 2019 2018 2019 2018 Derivatives Not Designated as Hedging Interest rate swaps: Commercial customers N/A $ 8,847.7 $ 7,455.9 $ 320.5 $ 76.3 $ 13.9 $ 102.6 Institutional counterparties N/A 8,851.8 7,161.3 17.1 22.6 78.2 32.4 Interest rate caps: Commercial customers N/A 246.0 329.1 1.6 0.6 0.1 2.5 Institutional counterparties N/A 246.0 329.1 0.1 2.5 1.6 0.6 Risk participation agreements (2) N/A 882.8 576.5 — — 0.1 — Foreign exchange contracts N/A 180.4 145.2 1.2 0.9 1.8 0.8 Forward commitments to sell N/A 23.3 9.5 0.5 0.1 — — Interest rate-lock commitments on N/A 33.6 13.6 — — 0.5 0.1 Total 341.0 103.0 96.2 139.0 Derivatives Designated as Hedging Interest rate swaps: Subordinated notes Fair value 375.0 375.0 — — — — Loans Cash flow 210.0 210.0 — — — — Total — — — — Total fair value of $ 341.0 $ 103.0 $ 96.2 $ 139.0 (1) Assets are recorded in other assets and liabilities are recorded in other liabilities.
Impact of Derivatives on Pre-Tax Income and Accumulated Other Comprehensive Loss	The following table summarizes the impact of People’s United’s derivatives on pre-tax income and AOCL: Type of Amount of Pre-Tax Gain (Loss) Amount of Pre-Tax Gain (Loss) Years ended December 31 (in millions) 2019 2018 2017 2019 2018 2017 Derivatives Not Designated as Interest rate swaps: Commercial customers N/A $ 374.9 $ (3.6) $ 5.3 $ — $ — $ — Institutional counterparties N/A (350.3) 17.1 6.1 — — — Interest rate caps: Commercial customers N/A 1.4 1.1 0.7 — — — Institutional counterparties N/A (1.5) (1.0) (0.3) — — — Foreign exchange contracts N/A 1.0 0.9 0.5 — — — Risk participation agreements N/A (0.4) 0.2 — — — — Forward commitments to sell N/A 0.3 (0.1) (0.2) — — — Interest rate-lock commitments on N/A (0.4) 0.1 0.3 — — — Total 25.0 14.7 12.4 — — — Derivatives Designated as Interest rate swaps Fair value 0.3 2.1 5.9 — — — Interest rate swaps Cash flow (1.2) (0.6) 0.8 1.9 (1.7) (1.0) Interest rate locks Cash flow 0.1 0.1 0.1 — — — Total (0.8) 1.6 6.8 1.9 (1.7) (1.0) Total $ 24.2 $ 16.3 $ 19.2 $ 1.9 $ (1.7) $ (1.0) (1) Amounts recognized in earnings are recorded in interest income, interest expense or other non-interest income for derivatives designated as hedging instruments and in other non-interest income for derivatives not designated as hedging instruments.

Balance Sheet Offsetting (Table

Balance Sheet Offsetting (Tables)	12 Months Ended
	Dec. 31, 2019
Offsetting [Abstract]
Summary of Gross Presentation, Financial Instruments that are Eligible for Offset Not Offset in Consolidated Statement of Condition	The following tables provide a gross presentation, the effects of offsetting, and a net presentation of the Company’s financial instruments that are eligible for offset in the Consolidated Statements of Condition. The collateral amounts in these tables are limited to the outstanding balances of the related asset or liability (after netting is applied) and, therefore, instances of overcollateralization are not presented. In the tables below, the Net Amount Presented of the derivative assets and liabilities can be reconciled to the fair value of the Company’s derivative financial instruments in Note 22. The Company’s derivative contracts with commercial customers and customer repurchase agreements are not subject to master netting arrangements and, therefore, have been excluded from the tables below. Gross Gross Net Gross Amounts Not Offset Net As of December 31, 2019 (in millions) Financial Collateral Financial assets: Interest rate swaps/caps: Counterparty A $ 0.2 $ — $ 0.2 $ (0.2) $ — $ — Counterparty B 0.1 — 0.1 (0.1) — — Counterparty C 0.4 — 0.4 (0.4) — — Counterparty D 0.1 — 0.1 (0.1) — — Counterparty E 15.3 — 15.3 — — 15.3 Other counterparties 1.1 — 1.1 (1.1) — — Foreign exchange contracts 1.2 — 1.2 — — 1.2 Total $ 18.4 $ — $ 18.4 $ (1.9) $ — $ 16.5 Financial liabilities: Interest rate swaps/caps: Counterparty A $ 2.3 $ — $ 2.3 $ (0.2) $ (2.1) $ — Counterparty B 5.5 — 5.5 (0.1) (5.4) — Counterparty C 28.2 — 28.2 (0.4) (27.8) — Counterparty D 10.9 — 10.9 (0.1) (10.8) — Counterparty E — — — — — — Other counterparties 32.9 — 32.9 (1.1) (31.8) — Foreign exchange contracts 1.8 — 1.8 — — 1.8 Total $ 81.6 $ — $ 81.6 $ (1.9) $ (77.9) $ 1.8 Gross Gross Net Gross Amounts Not Offset Net As of December 31, 2018 (in millions) Financial Collateral Financial assets: Interest rate swaps/caps: Counterparty A $ 3.1 $ — $ 3.1 $ (1.4) $ (1.7) $ — Counterparty B 2.5 — 2.5 (2.5) — — Counterparty C 4.8 — 4.8 (3.7) (1.1) — Counterparty D 3.6 — 3.6 (2.7) (0.1) 0.8 Counterparty E — — — — — — Other counterparties 11.1 — 11.1 (5.4) (5.7) — Foreign exchange contracts 0.9 — 0.9 — — 0.9 Total $ 26.0 $ — $ 26.0 $ (15.7) $ (8.6) $ 1.7 Financial liabilities: Interest rate swaps/caps: Counterparty A $ 1.4 $ — $ 1.4 $ (1.4) $ — $ — Counterparty B 3.8 — 3.8 (2.5) (1.2) 0.1 Counterparty C 3.7 — 3.7 (3.7) — — Counterparty D 2.7 — 2.7 (2.7) — — Counterparty E 16.0 — 16.0 — — 16.0 Other counterparties 5.4 — 5.4 (5.4) — — Foreign exchange contracts 0.8 — 0.8 — — 0.8 Total $ 33.8 $ — $ 33.8 $ (15.7) $ (1.2) $ 16.9
Summary of Collateral Swaps	The following tables show the extent to which assets and liabilities exchanged under resale and repurchase agreements have been offset in the Consolidated Statements of Condition. These agreements: (i) are entered into simultaneously with the same financial institution counterparty; (ii) have the same principal amounts and inception/maturity dates; and (iii) are subject to a master netting arrangement that contains a conditional right of offset upon default. At December 31, 2019 and 2018, the Company posted as collateral marketable securities with fair values of $462.4 million and $461.3 million, respectively, and, in turn, accepted as collateral marketable securities with fair values of $457.5 million and $457.0 million, respectively. As of December 31, 2019 (in millions) Gross Gross Net Total resale agreements $ 450.0 $ (450.0) $ — Total repurchase agreements $ 450.0 $ (450.0) $ — As of December 31, 2018 (in millions) Gross Gross Net Total resale agreements $ 450.0 $ (450.0) $ — Total repurchase agreements $ 450.0 $ (450.0) $ —

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2019
Segment Reporting [Abstract]
Selected Financial Information Business Segments	The following tables provide selected financial information for People’s United’s reportable segments: Year ended December 31, 2019 (in millions) Commercial Retail Total Treasury Other Total Net interest income (loss) $ 807.1 $ 555.1 $ 1,362.2 $ 66.5 $ (16.4) $ 1,412.3 Provision for loan losses 44.1 8.9 53.0 — (24.7) 28.3 Total non-interest income 206.5 195.9 402.4 14.1 14.6 431.1 Total non-interest expense 448.7 600.2 1,048.9 13.8 100.0 1,162.7 Income (loss) before income tax 520.8 141.9 662.7 66.8 (77.1) 652.4 Income tax expense (benefit) 104.3 28.5 132.8 13.5 (14.3) 132.0 Net income (loss) $ 416.5 $ 113.4 $ 529.9 $ 53.3 $ (62.8) $ 520.4 Average total assets $ 29,746.8 $ 12,560.9 $ 42,307.7 $ 7,882.3 $ 1,468.0 $ 51,658.0 Average total liabilities 11,490.2 23,397.7 34,887.9 9,011.9 686.9 44,586.7 Year ended December 31, 2018 (in millions) Commercial Retail Total Treasury Other Total Net interest income (loss) $ 699.2 $ 467.2 $ 1,166.4 $ 93.0 $ (23.4) $ 1,236.0 Provision for loan losses 38.7 9.0 47.7 — (17.7) 30.0 Total non-interest income 177.8 186.7 364.5 8.3 (6.4) 366.4 Total non-interest expense 383.7 565.3 949.0 17.8 29.3 996.1 Income (loss) before income tax 454.6 79.6 534.2 83.5 (41.4) 576.3 Income tax expense (benefit) 85.0 14.9 99.9 15.8 (7.5) 108.2 Net income (loss) $ 369.6 $ 64.7 $ 434.3 $ 67.7 $ (33.9) $ 468.1 Average total assets $ 25,956.7 $ 10,103.3 $ 36,060.0 $ 7,955.8 $ 1,013.9 $ 45,029.7 Average total liabilities 9,305.0 20,699.1 30,004.1 8,544.3 444.1 38,992.5 Year ended December 31, 2017 (in millions) Commercial Retail Total Treasury Other Total Net interest income (loss) $ 631.0 $ 403.9 $ 1,034.9 $ 107.4 $ (41.8) $ 1,100.5 Provision for loan losses 43.7 13.4 57.1 — (31.1) 26.0 Total non-interest income 165.0 183.4 348.4 11.2 (6.7) 352.9 Total non-interest expense 357.1 547.0 904.1 15.6 40.6 960.3 Income (loss) before income tax 395.2 26.9 422.1 103.0 (58.0) 467.1 Income tax expense (benefit) 110.0 7.5 117.5 28.6 (16.2) 129.9 Net income (loss) $ 285.2 $ 19.4 $ 304.6 $ 74.4 $ (41.8) $ 337.2 Average total assets $ 24,533.9 $ 9,695.1 $ 34,229.0 $ 7,512.1 $ 840.5 $ 42,581.6 Average total liabilities 7,938.6 20,202.8 28,141.4 8,450.6 398.0 36,990.0

Parent Company Financial Info_2

Parent Company Financial Information (Tables) - People's United Financial, Inc. [Member]	12 Months Ended
	Dec. 31, 2019
Condensed Balance Sheet Statements, Captions [Line Items]
Condensed Statements of Condition	CONDENSED STATEMENTS OF CONDITION As of December 31 (in millions) 2019 2018 Assets: Cash at bank subsidiary $ 455.2 $ 291.6 Total cash and cash equivalents 455.2 291.6 Equity securities, at fair value 8.2 8.1 Investments in subsidiaries: Bank subsidiary 7,800.0 6,485.3 Non-bank subsidiaries 4.8 2.8 Goodwill 203.0 197.1 Due from bank subsidiary 4.6 5.5 Other assets 56.0 45.9 Total assets $ 8,531.8 $ 7,036.3 Liabilities and Stockholders’ Equity: Notes and debentures $ 579.9 $ 497.7 Other liabilities 4.7 4.7 Stockholders’ equity 7,947.2 6,533.9 Total liabilities and stockholders’ equity $ 8,531.8 $ 7,036.3
Condensed Statements of Income	CONDENSED STATEMENTS OF INCOME Years ended December 31(in millions) 2019 2018 2017 Revenues: Interest income: Securities $ 0.4 $ 0.4 $ 1.1 Total interest income 0.4 0.4 1.1 Dividend income from bank subsidiary 457.0 342.0 292.0 Net security losses — — (1.2) Other non-interest income 1.7 2.3 16.9 Total revenues 459.1 344.7 308.8 Expenses: Interest on notes and debentures 19.2 18.7 19.0 Non-interest expense 14.1 11.4 13.9 Total expenses 33.3 30.1 32.9 Income before income tax benefit and 425.8 314.6 275.9 Income tax benefit (6.2) (5.5) (5.7) Income before subsidiaries undistributed income 432.0 320.1 281.6 Subsidiaries undistributed income 88.4 148.0 55.6 Net income $ 520.4 $ 468.1 $ 337.2
Condensed Statements of Comprehensive Income	CONDENSED STATEMENTS OF COMPREHENSIVE INCOME Years ended December 31 (in millions) 2019 2018 2017 Net income $ 520.4 $ 468.1 $ 337.2 Other comprehensive income (loss), net of tax: Net unrealized losses on securities available-for-sale — — (0.1) Net unrealized losses on derivatives accounted for as cash flow hedges (0.1) — — Other comprehensive income (loss) of bank subsidiary 90.0 (37.8) 13.4 Total other comprehensive income (loss), net of tax 89.9 (37.8) 13.3 Total comprehensive income $ 610.3 $ 430.3 $ 350.5
Condensed Statements of Cash Flows	CONDENSED STATEMENTS OF CASH FLOWS Years ended December 31 (in millions) 2019 2018 2017 Cash Flows from Operating Activities: Net income $ 520.4 $ 468.1 $ 337.2 Adjustments to reconcile net income to net cash provided Subsidiaries undistributed income (88.4) (148.0) (55.6) Net security losses — — 1.2 Net change in other assets and other liabilities (0.7) 23.1 20.1 Net cash provided by operating activities 431.3 343.2 302.9 Cash Flows from Investing Activities: Proceeds from sales of equity securities 1.6 2.3 — Proceeds from sales of debt securities available-for-sale — — 75.6 Increase in investment in bank subsidiary — (200.0) — Net cash provided by (used in) investing activities 1.6 (197.7) 75.6 Cash Flows from Financing Activities: Repayment of notes and debentures — — (125.0) Cash dividends paid on common stock (274.8) (243.8) (227.9) Cash dividends paid on preferred stock (14.1) (14.1) (14.1) Common stock repurchases (4.5) (2.5) (3.4) Proceeds from stock options exercised 24.1 27.9 61.8 Net cash used in financing activities (269.3) (232.5) (308.6) Net increase (decrease) in cash and cash equivalents 163.6 (87.0) 69.9 Cash and cash equivalents at beginning of year 291.6 378.6 308.7 Cash and cash equivalents at end of year $ 455.2 $ 291.6 $ 378.6

Selected Quarterly Financial _2

Selected Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Data	The following table presents People’s United’s quarterly financial data for 2019 and 2018: 2019 (1) 2018 (1) (dollars in millions, except First Second Third Fourth First Second Third Fourth Interest and dividend income $ 440.5 $ 472.8 $ 470.9 $ 496.9 $ 359.1 $ 375.4 $ 390.0 $ 431.8 Interest expense 107.7 124.7 122.2 114.2 63.3 74.2 83.6 99.2 Net interest income 332.8 348.1 348.7 382.7 295.8 301.2 306.4 332.6 Provision for loan losses 5.6 7.6 7.8 7.3 5.4 6.5 8.2 9.9 Net interest income 327.2 340.5 340.9 375.4 290.4 294.7 298.2 322.7 Non-interest income 94.6 106.3 106.0 124.2 90.4 94.9 92.3 88.7 Non-interest expense 277.2 278.4 281.4 325.7 243.5 248.6 241.3 262.7 Income before income tax 144.6 168.4 165.5 173.9 137.3 141.0 149.2 148.7 Income tax expense 30.0 35.2 30.4 36.4 29.4 30.8 32.2 15.8 Net income 114.6 133.2 135.1 137.5 107.9 110.2 117.0 132.9 Preferred stock dividend 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 Net income available to $ 111.1 $ 129.7 $ 131.6 $ 134.0 $ 104.4 $ 106.7 $ 113.5 $ 129.4 Common Share Data: EPS: Basic $ 0.30 $ 0.33 $ 0.34 $ 0.31 $ 0.31 $ 0.31 $ 0.33 $ 0.35 Diluted 0.30 0.33 0.33 0.31 0.30 0.31 0.33 0.35 Common dividends paid 65.2 69.8 69.9 69.9 58.8 59.9 60.0 65.1 Dividends paid per 0.1750 0.1775 0.1775 0.1775 0.1725 0.1750 0.1750 0.1750 Common dividend payout ratio 58.6 % 53.8 % 53.1 % 52.2 % 56.3 % 56.2 % 52.9 % 50.3 % Stock price: High $ 18.03 $ 17.66 $ 17.10 $ 17.22 $ 20.26 $ 19.37 $ 19.00 $ 17.46 Low 14.25 15.24 13.81 14.73 18.18 18.00 16.95 13.66 Weighted average common shares Basic 370.72 391.27 391.66 421.85 339.76 340.64 341.43 370.22 Diluted 374.09 394.57 394.45 424.98 344.00 344.47 345.04 372.83 (1) The sum of the quarterly amounts for certain line items may not equal the full-year amounts due to rounding.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Detail)

Jan. 01, 2020USD ($)

Jan. 01, 2019USD ($)

Dec. 31, 2019USD ($)

Sep. 30, 2019USD ($)

Jun. 30, 2019USD ($)

Mar. 31, 2019USD ($)

Dec. 31, 2018USD ($)

Sep. 30, 2018USD ($)

Jun. 30, 2018USD ($)

Mar. 31, 2018USD ($)

Dec. 31, 2020

Dec. 31, 2019USD ($)RatingReporting_Unit

Dec. 31, 2018USD ($)Reporting_Unit

Dec. 31, 2017USD ($)

Summary Of Significant Accounting Policies [Line Items]

Number of days of non accrual status

90 days

Accruing interest total

$ 0

$ 0

$ 0

$ 0

$ 0

Collateral values/LTV ratios, minimum

70.00%

Borrower credit scores, minimum | Rating

680

Non-interest income

$ 124,200,000

$ 106,000,000

$ 106,300,000

$ 94,600,000

$ 88,700,000

$ 92,300,000

$ 94,900,000

$ 90,400,000

$ 431,100,000

$ 366,400,000

352,900,000

Non-interest income percentage

67.00%

74.00%

67.00%

74.00%

Number of reporting units | Reporting_Unit

3

3

Operating lease

$ 307,900,000

$ 307,900,000

Lease ROU assets

276,600,000

276,600,000

Retained earnings

$ 1,512,800,000

$ 1,284,800,000

1,512,800,000

$ 1,284,800,000

Operating Segments [Member]

Summary Of Significant Accounting Policies [Line Items]

Non-interest income

402,400,000

364,500,000

348,400,000

Significant Revenue Streams [Member]

Summary Of Significant Accounting Policies [Line Items]

Non-interest income

$ 288,000,000

270,000,000

Accounting Standards Update 2016-02 [Member]

Summary Of Significant Accounting Policies [Line Items]

Operating lease

$ 268,800,000

Lease ROU assets

$ 248,500,000

Increase (decrease) in risk-based capital ratios

(0.10%)

Accounting Standards Update 2018-02 [Member]

Summary Of Significant Accounting Policies [Line Items]

Increase (decrease) in risk-based capital ratios

0.11%

Accounting Standards Update 2018-02 [Member] | Retained Earnings [Member]

Summary Of Significant Accounting Policies [Line Items]

Cumulative effect on retained earnings

$ 37,900,000

Accounting Standards Update 2016-13 [Member] | Subsequent Event [Member] | Scenario, Forecast [Member]

Summary Of Significant Accounting Policies [Line Items]

Retained earnings

$ 60,000,000

Accounting Standards Update 2016-13 [Member] | Subsequent Event [Member] | PCI [Member] | Scenario, Forecast [Member]

Summary Of Significant Accounting Policies [Line Items]

Adjustment to amortized cost basis

$ (30,000,000)

Trade Name [Member] | Accelerated Amortization [Member]

Summary Of Significant Accounting Policies [Line Items]

Finite-lived intangible assets, useful life, (in years)

20 years

Trade Name [Member] | Straight Line Amortization [Member]

Summary Of Significant Accounting Policies [Line Items]

Finite-lived intangible assets, useful life, (in years)

5 years

Commercial Banking Loan [Member] | Operating Segments [Member]

Summary Of Significant Accounting Policies [Line Items]

Non-interest income

$ 206,500,000

$ 177,800,000

165,000,000

Non-interest income percentage

40.00%

40.00%

40.00%

40.00%

Retail Banking [Member] | Operating Segments [Member]

Summary Of Significant Accounting Policies [Line Items]

Non-interest income

$ 195,900,000

$ 186,700,000

$ 183,400,000

Non-interest income percentage

30.00%

30.00%

30.00%

30.00%

Leasehold Improvements [Member]

Summary Of Significant Accounting Policies [Line Items]

Estimated useful lives of assets, (in years)

10 years

Building [Member]

Summary Of Significant Accounting Policies [Line Items]

Estimated useful lives of assets, (in years)

40 years

Furniture and Fixtures [Member]

Summary Of Significant Accounting Policies [Line Items]

Estimated useful lives of assets, (in years)

10 years

Minimum [Member]

Summary Of Significant Accounting Policies [Line Items]

Loan agreement

6 months

Non accrual commercial loans

$ 1,000,000

$ 1,000,000

Minimum [Member] | Accounting Standards Update 2016-02 [Member]

Summary Of Significant Accounting Policies [Line Items]

Increase (decrease) in risk-based capital ratios

(0.05%)

Minimum [Member] | Accounting Standards Update 2016-13 [Member] | Subsequent Event [Member] | Scenario, Forecast [Member]

Summary Of Significant Accounting Policies [Line Items]

Increase (decrease) in regulatory capital ratio

(0.10%)

Minimum [Member] | Core Deposit Intangibles [Member]

Summary Of Significant Accounting Policies [Line Items]

Finite-lived intangible assets, useful life, (in years)

6 years

Minimum [Member] | Customer Relationships [Member]

Summary Of Significant Accounting Policies [Line Items]

Finite-lived intangible assets, useful life, (in years)

10 years

Minimum [Member] | Data Processing and Other Equipment [Member]

Summary Of Significant Accounting Policies [Line Items]

Estimated useful lives of assets, (in years)

3 years

Minimum [Member] | Computer Software [Member]

Summary Of Significant Accounting Policies [Line Items]

Estimated useful lives of assets, (in years)

3 years

Maximum [Member]

Summary Of Significant Accounting Policies [Line Items]

Term of contract with customers

1 year

Maximum [Member] | Accounting Standards Update 2016-02 [Member]

Summary Of Significant Accounting Policies [Line Items]

Increase (decrease) in risk-based capital ratios

(0.10%)

Maximum [Member] | Core Deposit Intangibles [Member]

Summary Of Significant Accounting Policies [Line Items]

Finite-lived intangible assets, useful life, (in years)

10 years

Maximum [Member] | Customer Relationships [Member]

Summary Of Significant Accounting Policies [Line Items]

Finite-lived intangible assets, useful life, (in years)

15 years

Maximum [Member] | Data Processing and Other Equipment [Member]

Summary Of Significant Accounting Policies [Line Items]

Estimated useful lives of assets, (in years)

5 years

Maximum [Member] | Computer Software [Member]

Summary Of Significant Accounting Policies [Line Items]

Estimated useful lives of assets, (in years)

5 years

Acquisitions and Dispositions -

Acquisitions and Dispositions - Additional Information (Detail) shares in Millions

Nov. 01, 2019USD ($)branchshares

Oct. 25, 2019USD ($)branch

Apr. 01, 2019USD ($)branchshares

Oct. 01, 2018USD ($)branchshares

Jun. 27, 2018USD ($)

Aug. 01, 2017USD ($)

Apr. 01, 2017USD ($)Branchesshares

Jun. 30, 2018Securitization

Sep. 30, 2017USD ($)

Dec. 31, 2019USD ($)

Dec. 31, 2018USD ($)

Dec. 31, 2017USD ($)

Jan. 02, 2019USD ($)

Business Acquisition [Line Items]

Loans outstanding principal balance

$ 532,200,000

$ 491,600,000

Goodwill

3,065,500,000

2,685,700,000

$ 2,411,400,000

Central Maine Branch Sale [Member]

Business Acquisition [Line Items]

Number of branches sold | branch

8

Deposits sold

$ 258,000,000

Loans sold

103,000,000

Assets under management sold

227,000,000

Gain on disposal

$ 7,600,000

United Financial [Member]

Business Acquisition [Line Items]

Business acquisition, date of acquisition agreement

Nov. 1, 2019

Business acquisition consideration transferred

$ 720,600,000

Business acquisition common stock shares (in shares) | shares

44.4

Number of branches acquired | branch

58

Merger-related expenses

$ 22,200,000

Net deferred tax liability

$ 16,700,000

Liabilities acquired

6,499,500,000

Goodwill

204,300,000

United Financial [Member] | Core Deposit Intangibles [Member]

Business Acquisition [Line Items]

Finite-lived intangible assets, useful life, (in years)

6 years

United Financial [Member] | Purchased Performing Loans [Member]

Business Acquisition [Line Items]

Loans

8,040,000,000

Loans outstanding principal balance

8,100,000,000

United Financial [Member] | Purchased Credit Impaired Loans [Member]

Business Acquisition [Line Items]

Loans

136,500,000

Total loans, net

193,100,000

BSB Bancorp [Member]

Business Acquisition [Line Items]

Business acquisition, date of acquisition agreement

Apr. 1, 2019

Business acquisition consideration transferred

$ 324,500,000

Business acquisition common stock shares (in shares) | shares

19.7

Number of branches acquired | branch

6

Merger-related expenses

$ 8,100,000

500,000

Net deferred tax liability

$ 3,800,000

Liabilities acquired

2,862,200,000

Goodwill

$ 144,900,000

BSB Bancorp [Member] | Core Deposit Intangibles [Member]

Business Acquisition [Line Items]

Finite-lived intangible assets, useful life, (in years)

10 years

BSB Bancorp [Member] | Purchased Credit Impaired Loans [Member]

Business Acquisition [Line Items]

Loans

$ 0

First Connecticut Bancorp, Inc. [Member]

Business Acquisition [Line Items]

Business acquisition, date of acquisition agreement

Oct. 1, 2018

Business acquisition consideration transferred

$ 486,400,000

Business acquisition common stock shares (in shares) | shares

28.4

Number of branches acquired | branch

25

Merger-related expenses

$ 16,800,000

8,800,000

Assets acquired

$ 3,450,000,000

Liabilities acquired

$ 2,960,000,000

Vend Lease [Member]

Business Acquisition [Line Items]

Business acquisition, date of acquisition agreement

Jun. 27, 2018

Merger-related expenses

$ 2,100,000

Loans

$ 68,800,000

Business acquisition cash consideration transferred

37,500,000

Goodwill

$ 23,900,000

LEAF Commercial Capital, Inc. [Member]

Business Acquisition [Line Items]

Business acquisition, date of acquisition agreement

Aug. 1, 2017

Merger-related expenses

3,700,000

Assets acquired

$ 957,700,000

Liabilities acquired

737,700,000

Business acquisition cash consideration transferred

$ 220,000,000

Repayment of borrowings

$ 460,000,000

Number of remaining securitization which can be repaid without penalty in 2018 | Securitization

1

Suffolk [Member]

Business Acquisition [Line Items]

Business acquisition, date of acquisition agreement

Apr. 1, 2017

Business acquisition consideration transferred

$ 484,800,000

Business acquisition common stock shares (in shares) | shares

26.6

Number of branches acquired | Branches

27

Merger-related expenses

$ 26,600,000

Assets acquired

$ 2,380,000,000

Liabilities acquired

$ 1,900,000,000

BSB Bancorp And United Financial [Member]

Business Acquisition [Line Items]

Interest income on loans acquired

125,000,000

VAR Technology Finance [Member]

Business Acquisition [Line Items]

Loans

$ 60,000,000

Payments for Merger Related Costs

$ 1,900,000

Acquisitions and Dispositions_2

Acquisitions and Dispositions - Estimated Fair Values of Assets Acquired and Liabilities Assumed (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Nov. 01, 2019	Apr. 01, 2019	Dec. 31, 2018	Dec. 31, 2017
Assets:
Goodwill	$ 3,065.5			$ 2,685.7	$ 2,411.4
United Financial [Member]
Assets:
Cash and cash equivalents		$ 594.9
Securities		381.3
Loans		5,535.5
Goodwill		204.3
Core deposit intangible		41.5
Premises and equipment		61.8
BOLI		196.5
Lease ROU assets		56.3
Mortgage servicing rights		10.6
REO		1.2
Other assets		136.2
Total assets		7,220.1
Liabilities:
Deposits		5,687.2
Borrowings		622.4
Lease liabilities		61.4
Other liabilities		128.5
Total liabilities		6,499.5
Total purchase price		$ 720.6
BSB Bancorp [Member]
Assets:
Cash and cash equivalents			$ 108.7
Securities			175.8
Loans			2,642.9
Goodwill			144.9
Core deposit intangible			39.5
Premises and equipment			8.3
BOLI			36.8
Other assets			29.8
Total assets			3,186.7
Liabilities:
Deposits			2,118.7
Borrowings			696.6
Other liabilities			46.9
Total liabilities			2,862.2
Total purchase price			$ 324.5

Acquisitions and Dispositions_3

Acquisitions and Dispositions - Summary of Pro Forma Financial Information Reflecting Acquisition (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Selected Financial Results:
Net interest income	$ 1,582.5	$ 1,488.6
Provision for loan losses	28.3	30
Non-interest income	454.5	408.1
Non-interest expense	1,277.5	1,186.4
Net income	583.5	552.4
Net income available to common shareholders	$ 569.4	$ 538.3
EPS:
Basic (in dollars per share)	$ 1.31	$ 1.30
Diluted (in dollars per share)	$ 1.30	$ 1.29

Cash and Cash Equivalents - Add

Cash and Cash Equivalents - Additional Information (Detail) - USD ($)	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash and Cash Equivalents [Line Items]
Cash at bank subsidiary	$ 171,600,000	$ 124,100,000
Restricted cash	$ 0	$ 0	$ 13,800,000
FHLB of New York [Member]
Cash and Cash Equivalents [Line Items]
Interest rate	1.55%	2.40%

Cash and Cash Equivalents - Cas

Cash and Cash Equivalents - Cash and Short-Term Investments (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Cash and Cash Equivalents [Abstract]
Interest-bearing deposits at the FRB-NY	$ 219.4	$ 234
Money market mutual funds	5.7	26.3
Other	91.7	6
Total short-term investments	$ 316.8	$ 266.3

Securities - Available-for-Sale

Securities - Available-for-Sale and Held-to-Maturity Debt Securities Gains (Losses) (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Debt securities available-for-sale:
Amortized Cost	$ 3,545.8	$ 3,185.6
Gross Unrealized Gains	25.4	4.7
Gross Unrealized Losses	(6.9)	(69.3)
Fair Value	3,564.3	3,121
Debt securities held-to-maturity:
Amortized Cost	3,869.2	3,792.3
Gross Unrealized Gains	151.5	35.9
Gross Unrealized Losses	(0.7)	(52.3)
Fair Value	4,020	3,775.9
U.S. Treasury and Agency [Member]
Debt securities available-for-sale:
Amortized Cost	689.5	699
Gross Unrealized Gains	0.4	0.1
Gross Unrealized Losses	(2.8)	(21.1)
Fair Value	687.1	678
Debt securities held-to-maturity:
Amortized Cost	0
Fair Value	0
State and Municipal [Member]
Debt securities available-for-sale:
Amortized Cost	0
Fair Value	0
Debt securities held-to-maturity:
Amortized Cost	2,503.9	2,352.4
Gross Unrealized Gains	142	35.4
Gross Unrealized Losses	(0.4)	(18.4)
Fair Value	2,645.5	2,369.4
GSE Mortgage-Backed Securities [Member]
Debt securities available-for-sale:
Amortized Cost	2,856.3	2,486.6
Gross Unrealized Gains	25	4.6
Gross Unrealized Losses	(4.1)	(48.2)
Fair Value	2,877.2	2,443
Debt securities held-to-maturity:
Amortized Cost	1,271.4	1,367.5
Gross Unrealized Gains	8	0
Gross Unrealized Losses	(0.3)	(33.2)
Fair Value	1,279.1	1,334.3
Corporate [Member]
Debt securities available-for-sale:
Amortized Cost	0
Fair Value	0
Debt securities held-to-maturity:
Amortized Cost	92.4	70.9
Gross Unrealized Gains	1.5	0.5
Gross Unrealized Losses	0	(0.7)
Fair Value	93.9	70.7
Other [Member]
Debt securities available-for-sale:
Amortized Cost	0
Fair Value	0
Debt securities held-to-maturity:
Amortized Cost	1.5	1.5
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	$ 1.5	$ 1.5

Securities - Additional Informa

Securities - Additional Information (Detail)	Jan. 01, 2018USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2019USD ($)SecuritySecurities	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Investment [Line Items]
Debt security available for sale with fair values pledged with collateral for public deposits		$ 2,200,000,000		$ 2,430,000,000	$ 2,200,000,000
Debt security available for sale with a held-to-maturity pledged with collateral for public deposits		1,490,000,000		$ 1,470,000,000	1,490,000,000
Percentage of securities available for sale				8.00%
Number of debt securities owned | Security				2,242
Number of debt securities classified as available-for-sale | Security				101
Number of debt securities classified as held-to-maturity | Securities				79
Available-for-sale unrealized losses		(69,300,000)		$ (6,900,000)	(69,300,000)
Held-to-maturity unrealized losses		(52,300,000)		(700,000)	(52,300,000)
Impairment of investments				0	0	$ 0
Loss on sales of Securities				400,000	10,000,000	27,500,000
Net security losses				200,000	(9,800,000)	(25,400,000)
Available-for-sale securities, amortized cost			$ 9,600,000			9,600,000
Equity securities, at fair value			8,700,000			8,700,000
Unrealized gain on equity securities				1,500,000	600,000
Impairment of investments				0
Dividend income on capital stock				$ 186,500,000	184,200,000	153,700,000
Federal Reserve Bank stock percentage				6.00%
Accounting Standards Update 2016-01 [Member]
Investment [Line Items]
Cumulative-effect transition adjustment to retained earnings	$ (600,000)
Investment in Federal Home Loan Bank Stock [Member]
Investment [Line Items]
Impairment of investments				$ 0
Dividend income on capital stock				7,000,000	8,300,000	6,600,000
FHLB of New York [Member]
Investment [Line Items]
Acquired shares of capital stock		700,000		700,000	700,000
Dividend income on capital stock				3,800,000	5,100,000	3,700,000
Acquired shares of capital stock		178,500,000		203,800,000	178,500,000
FHLB of Boston [Member]
Investment [Line Items]
Acquired shares of capital stock		124,200,000		136,600,000	124,200,000
GSE Mortgage-Backed Securities [Member]
Investment [Line Items]
Available-for-sale unrealized losses		(48,200,000)		(4,100,000)	(48,200,000)
Held-to-maturity unrealized losses		(33,200,000)		$ (300,000)	(33,200,000)
Available for sale securities average maturity period				18 years
Amortized cost of securities, sold		235,500,000
Loss on sales of Securities		10,000,000
State and Municipal [Member]
Investment [Line Items]
Held-to-maturity unrealized losses		$ (18,400,000)		$ (400,000)	(18,400,000)
Available for sale securities average maturity period				9 years
U.S. Treasury and CMO Securities [Member]
Investment [Line Items]
Amortized cost of securities, sold			291,300,000			486,900,000
Loss on sales of Securities			$ 10,000,000			15,700,000
Net security losses				$ 200,000	$ (9,800,000)	$ (25,400,000)

Securities - Summary of Amortiz

Securities - Summary of Amortized Cost and Fair Value of Debt Securities Based on Remaining Period to Contractual Maturity (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Available for sale amortized cost
Within 1 year	$ 158.4
After 1 but within 5 years	616
After 5 but within 10 years	855.1
After 10 years	1,916.3
Amortized Cost	3,545.8	$ 3,185.6
Available for sale fair value
Within 1 year	158.4
After 1 but within 5 years	615.6
After 5 but within 10 years	867.7
After 10 years	1,922.6
Fair value	$ 3,564.3	3,121
Available for sale FTE yield
Within 1 year	1.84%
After 1 but within 5 years	1.67%
After 5 but within 10 years	2.67%
After 10 years	2.35%
Total	2.29%
Held-to-maturity amortized cost
Within 1 year	$ 19.5
After 1 but within 5 years	1,097.4
After 5 but within 10 years	625.4
After 10 years	2,126.9
Amortized Cost	3,869.2	3,792.3
Held-to-maturity fair value
Within 1 year	19.6
After 1 but within 5 years	1,112.9
After 5 but within 10 years	653.3
After 10 years	2,234.2
Fair value	$ 4,020	3,775.9
Held-to-maturity FTE yield
Within 1 year	2.74%
After 1 but within 5 years	2.51%
After 5 but within 10 years	3.43%
After 10 years	3.59%
Total	3.25%
U.S. Treasury and Agency [Member]
Available for sale amortized cost
Within 1 year	$ 158.4
After 1 but within 5 years	531.1
Amortized Cost	689.5	699
Available for sale fair value
Within 1 year	158.4
After 1 but within 5 years	528.7
Fair value	$ 687.1	678
Available for sale FTE yield
Within 1 year	1.84%
After 1 but within 5 years	1.43%
Total	1.53%
Held-to-maturity amortized cost
Within 1 year	$ 0
After 1 but within 5 years	0
Amortized Cost	0
Held-to-maturity fair value
Within 1 year	0
After 1 but within 5 years	0
Fair value	$ 0
Held-to-maturity FTE yield
Within 1 year	0.00%
After 1 but within 5 years	0.00%
Total	0.00%
GSE Mortgage-Backed Securities [Member]
Available for sale amortized cost
Within 1 year	$ 0
After 1 but within 5 years	84.9
After 5 but within 10 years	855.1
After 10 years	1,916.3
Amortized Cost	2,856.3	2,486.6
Available for sale fair value
Within 1 year	0
After 1 but within 5 years	86.9
After 5 but within 10 years	867.7
After 10 years	1,922.6
Fair value	$ 2,877.2	2,443
Available for sale FTE yield
Within 1 year	0.00%
After 1 but within 5 years	3.17%
After 5 but within 10 years	2.67%
After 10 years	2.35%
Total	2.47%
Held-to-maturity amortized cost
Within 1 year	$ 2.7
After 1 but within 5 years	861
After 5 but within 10 years	120.2
After 10 years	287.5
Amortized Cost	1,271.4	1,367.5
Held-to-maturity fair value
Within 1 year	2.7
After 1 but within 5 years	866.6
After 5 but within 10 years	121.3
After 10 years	288.5
Fair value	$ 1,279.1	1,334.3
Held-to-maturity FTE yield
Within 1 year	2.04%
After 1 but within 5 years	2.43%
After 5 but within 10 years	2.52%
After 10 years	2.17%
Total	2.38%
State and Municipal [Member]
Available for sale amortized cost
Within 1 year	$ 0
After 1 but within 5 years	0
After 5 but within 10 years	0
After 10 years	0
Amortized Cost	0
Available for sale fair value
Within 1 year	0
After 1 but within 5 years	0
After 5 but within 10 years	0
After 10 years	0
Fair value	$ 0
Available for sale FTE yield
Within 1 year	0.00%
After 1 but within 5 years	0.00%
After 5 but within 10 years	0.00%
After 10 years	0.00%
Total	0.00%
Held-to-maturity amortized cost
Within 1 year	$ 10.3
After 1 but within 5 years	235.4
After 5 but within 10 years	418.8
After 10 years	1,839.4
Amortized Cost	2,503.9	2,352.4
Held-to-maturity fair value
Within 1 year	10.4
After 1 but within 5 years	245.3
After 5 but within 10 years	444.1
After 10 years	1,945.7
Fair value	$ 2,645.5	2,369.4
Held-to-maturity FTE yield
Within 1 year	2.61%
After 1 but within 5 years	2.78%
After 5 but within 10 years	3.47%
After 10 years	3.81%
Total	3.65%
Corporate [Member]
Available for sale amortized cost
Within 1 year	$ 0
After 1 but within 5 years	0
After 5 but within 10 years	0
Amortized Cost	0
Available for sale fair value
Within 1 year	0
After 1 but within 5 years	0
After 5 but within 10 years	0
Fair value	$ 0
Available for sale FTE yield
Within 1 year	0.00%
After 1 but within 5 years	0.00%
After 5 but within 10 years	0.00%
Total	0.00%
Held-to-maturity amortized cost
Within 1 year	$ 5
After 1 but within 5 years	1
After 5 but within 10 years	86.4
Amortized Cost	92.4	70.9
Held-to-maturity fair value
Within 1 year	5
After 1 but within 5 years	1
After 5 but within 10 years	87.9
Fair value	$ 93.9	70.7
Held-to-maturity FTE yield
Within 1 year	3.50%
After 1 but within 5 years	2.67%
After 5 but within 10 years	4.52%
Total	4.45%
Other [Member]
Available for sale amortized cost
Within 1 year	$ 0
Amortized Cost	0
Available for sale fair value
Within 1 year	0
Fair value	$ 0
Available for sale FTE yield
Within 1 year	0.00%
Total	0.00%
Held-to-maturity amortized cost
Within 1 year	$ 1.5
Amortized Cost	1.5	1.5
Held-to-maturity fair value
Within 1 year	1.5
Fair value	$ 1.5	$ 1.5
Held-to-maturity FTE yield
Within 1 year	2.46%
Total	2.46%

Securities - Continuous Unreali

Securities - Continuous Unrealized Loss Position on Available-for-Sale and Held-to-Maturities Securities (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Available-for-sale, Fair Value
Less Than 12 Months	$ 746.4	$ 132.4
12 Months Or Longer	871.7	2,312.5
Total	1,618.1	2,444.9
Available-for-sale, Unrealized Losses
Less Than 12 Months	(3.5)	(0.5)
12 Months Or Longer	(3.4)	(68.8)
Total	(6.9)	(69.3)
Held-to-maturity, Fair Value
Less Than 12 Months	137.4	144.6
12 Months Or Longer	29.1	2,034.6
Total	166.5	2,179.2
Held-to-maturity, Unrealized Losses
Less Than 12 Months	(0.5)	(1.3)
12 Months Or Longer	(0.2)	(51)
Total	(0.7)	(52.3)
GSE Mortgage-Backed Securities [Member]
Available-for-sale, Fair Value
Less Than 12 Months	565.4	132.4
12 Months Or Longer	509.3	1,656.3
Total	1,074.7	1,788.7
Available-for-sale, Unrealized Losses
Less Than 12 Months	(3.1)	(0.5)
12 Months Or Longer	(1)	(47.7)
Total	(4.1)	(48.2)
Held-to-maturity, Fair Value
Less Than 12 Months	100.9	0
12 Months Or Longer	9.1	1,334.3
Total	110	1,334.3
Held-to-maturity, Unrealized Losses
Less Than 12 Months	(0.3)	0
12 Months Or Longer	0	(33.2)
Total	(0.3)	(33.2)
U.S. Treasury and Agency [Member]
Available-for-sale, Fair Value
Less Than 12 Months	181	0
12 Months Or Longer	362.4	656.2
Total	543.4	656.2
Available-for-sale, Unrealized Losses
Less Than 12 Months	(0.4)	0
12 Months Or Longer	(2.4)	(21.1)
Total	(2.8)	(21.1)
State and Municipal [Member]
Held-to-maturity, Fair Value
Less Than 12 Months	33	113.4
12 Months Or Longer	11.4	697.6
Total	44.4	811
Held-to-maturity, Unrealized Losses
Less Than 12 Months	(0.2)	(0.7)
12 Months Or Longer	(0.2)	(17.7)
Total	(0.4)	(18.4)
Corporate [Member]
Held-to-maturity, Fair Value
Less Than 12 Months	3.5	31.2
12 Months Or Longer	8.6	2.7
Total	12.1	33.9
Held-to-maturity, Unrealized Losses
Less Than 12 Months	0	(0.6)
12 Months Or Longer	0	(0.1)
Total	0	$ (0.7)
Maximum [Member]
Available-for-sale, Unrealized Losses
Total	$ (0.1)

Securities - Schedule of Compon

Securities - Schedule of Components of Net Security Losses (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt securities:
Gains	$ 0.5	$ 0.1	$ 2.1
Losses	(0.4)	(10)	(27.5)
Total debt securities	0.1	(9.9)	(25.4)
Trading debt securities:
Gains	0.1	0.1	0
Losses	0	0	0
Total trading debt securities	0.1	0.1	0
Net security gains (losses)	$ 0.2	$ (9.8)	(25.4)
Maximum [Member]
Trading debt securities:
Total trading debt securities			$ 0.1

Loans - Additional Information

Loans - Additional Information (Detail)	Apr. 16, 2010USD ($)	Dec. 31, 2019USD ($)SegmentsRating	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of segments (in segments) | Segments		2
Net deferred loan costs		$ 87,500,000	$ 94,600,000
Construction loans		1,100,000,000	651,200,000
Interest-only residential mortgage loans		1,100,000,000	1,200,000,000
Net gains on sales of residential mortgage loans		1,900,000	1,200,000	$ 3,200,000
Loans held-for-sale		511,300,000	19,500,000
Acquired loans sold, outstanding balance		10,100,000	10,000,000	7,900,000
Acquired loans sold, carrying amount		7,100,000	4,400,000	5,000,000
Net gains (losses) on sales of acquired loan		400,000	1,800,000	2,400,000
Recorded investments, non-performing loans		157,000,000	167,700,000	148,700,000
Interest income that would have recognized		18,500,000	18,100,000	16,200,000
Allowance for loan losses		246,600,000	240,400,000	234,400,000	$ 229,300,000
Interest Income Recognized		$ 5,700,000	6,400,000	5,600,000
Interest rate reduction		2.00%
Collateral values/LTV ratios, minimum		70.00%
Borrower credit scores, minimum | Rating		680
Principal and interest payments receivable		$ 7,950,000,000
Expected cash flows		7,350,000,000
Loan portfolio fair value		5,620,000,000
Aggregate loan nonaccretable difference		603,100,000
Portfolio accretable yield		137,500,000	189,700,000	219,700,000	255,400,000
Portfolio outstanding balance		532,200,000	491,600,000
Portfolio carrying value		396,000,000	399,900,000
FDIC loss-share receivable		$ 100,000	$ 200,000
Connecticut [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of total loan portfolio representing loans to customers		25.00%
Massachusetts [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of total loan portfolio representing loans to customers		22.00%
New York State [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of total loan portfolio representing loans to customers		18.00%
New England [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of total loan portfolio representing loans to customers		58.00%	56.00%
Residential Mortgage Construction Financing Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Construction loans		$ 40,500,000	$ 57,300,000
Construction loan not yet advanced		14,600,000	21,500,000
Commercial Real Estate Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Early non-performing loans		8,600,000	20,300,000
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held-for-sale		157,900,000
Early non-performing loans		18,800,000	15,800,000
Equipment Financing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Early non-performing loans		$ 26,200,000	$ 28,400,000
Equipment Financing [Member] | Outside New England [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of total loan portfolio representing loans to customers		95.00%	95.00%
Equipment Financing [Member] | Texas California and New York [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of total loan portfolio representing loans to customers		30.00%
Equipment Financing [Member] | Outside Texas California and New York [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of total loan portfolio representing loans to customers		7.00%
Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held-for-sale		$ 19,700,000	$ 19,500,000
Commercial Construction Financing Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Construction loan not yet advanced		798,300,000	588,200,000
Other Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held-for-sale		333,700,000
Acquired Loans [Member] | Subsequent to Acquisition [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investments, non-performing loans		13,200,000	6,000,000	4,700,000
Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investments, non-performing loans		108,100,000	113,500,000	100,600,000
Allowance for loan losses		217,900,000	209,500,000	204,500,000	204,900,000
Interest Income Recognized		$ 3,000,000	4,000,000	3,500,000
Duration of extension for payment deferral on TDRs, years		2 years
Commercial [Member] | Commercial Real Estate Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investments, non-performing loans		$ 29,800,000	33,500,000	23,700,000
Interest Income Recognized		1,100,000	1,100,000	1,200,000
Commercial [Member] | Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investments, non-performing loans		32,100,000	38,000,000	32,600,000
Interest Income Recognized		1,600,000	2,800,000	1,900,000
Commercial [Member] | Equipment Financing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investments, non-performing loans		46,200,000	42,000,000	44,300,000
Interest Income Recognized		300,000	100,000	400,000
Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investments, non-performing loans		48,900,000	54,200,000	48,100,000
Allowance for loan losses		28,700,000	30,900,000	29,900,000	$ 24,400,000
Interest Income Recognized		$ 2,700,000	2,400,000	2,100,000
Duration of extension for payment deferral on TDRs, years		5 years
Retail Loans [Member] | Other Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investments, non-performing loans		$ 0	0	0
Interest Income Recognized		0	0	0
Butler Bank [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
FDIC reimbursement for future losses in percentage	80.00%
FDIC loss share reimbursement value maximum	$ 34,000,000
Bank reimbursement to FDIC for future recoveries of losses reimbursed to bank by FDIC	80.00%
At Acquisition [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Portfolio accretable yield		1,730,000,000
Acquired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investments, non-performing loans		53,500,000	44,100,000	25,100,000
Acquired Loans [Member] | Purchased Performing Loans [Member] | Subsequent to Acquisition [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investments, non-performing loans		13,600,000	6,000,000	4,700,000
Non-Performing Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income on loans acquired		2,300,000	2,900,000	1,700,000
Troubled Debt Restructurings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment in originated loans classified as TDRs		177,000,000	179,400,000
Allowance for loan losses		4,300,000	4,500,000
Interest Income Recognized		5,500,000	6,100,000	$ 4,700,000
Foreclosure or Bankruptcy [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Early non-performing loans		$ 20,800,000	$ 19,100,000

Loans - Summary of Loans by Loa

Loans - Summary of Loans by Loan Portfolio Segment and Class (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable	$ 43,596.1	$ 35,241.4
Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable	30,714.3	25,077.7
Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable	12,881.8	10,163.7
Commercial Real Estate Loan [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable	14,762.3	11,649.6
Commercial and Industrial [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable	11,041.6	9,088.9
Equipment Financing [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable	4,910.4	4,339.2
Residential Mortgage Loan [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable	10,318.1	8,154.2
Residential Mortgage Adjustable Rate [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable	7,064.8	6,662
Residential Mortgage Fixed Rate [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable	3,253.3	1,492.2
Home Equity and Other Consumer [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable	2,563.7	2,009.5
Home Equity Loan [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable	2,406.5	1,962.5
Other Consumer [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable	157.2	47
Originated [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable	32,735.4	30,650
Originated [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable	24,481.7	22,028.5
Originated [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable	8,253.7	8,621.5
Originated [Member] | Commercial Real Estate Loan [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable	10,012.5	9,798.5
Originated [Member] | Commercial and Industrial [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable	9,763.1	8,292.3
Originated [Member] | Equipment Financing [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable	4,706.1	3,937.7
Originated [Member] | Residential Mortgage Loan [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable	6,588.9	6,789.2
Originated [Member] | Residential Mortgage Adjustable Rate [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable	5,366	5,854.1
Originated [Member] | Residential Mortgage Fixed Rate [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable	1,222.9	935.1
Originated [Member] | Home Equity and Other Consumer [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable	1,664.8	1,832.3
Originated [Member] | Home Equity Loan [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable	1,625.1	1,789.5
Originated [Member] | Other Consumer [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable	39.7	42.8
Acquired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable	10,860.7	4,591.4
Acquired Loans [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable	6,232.6	3,049.2
Acquired Loans [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable	4,628.1	1,542.2
Acquired Loans [Member] | Commercial Real Estate Loan [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable	4,749.8	1,851.1
Acquired Loans [Member] | Commercial and Industrial [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable	1,278.5	796.6
Acquired Loans [Member] | Equipment Financing [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable	204.3	401.5
Acquired Loans [Member] | Residential Mortgage Loan [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable	3,729.2	1,365
Acquired Loans [Member] | Residential Mortgage Adjustable Rate [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable	1,698.8	807.9
Acquired Loans [Member] | Residential Mortgage Fixed Rate [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable	2,030.4	557.1
Acquired Loans [Member] | Home Equity and Other Consumer [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable	898.9	177.2
Acquired Loans [Member] | Home Equity Loan [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable	781.4	173
Acquired Loans [Member] | Other Consumer [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable	$ 117.5	$ 4.2

Loans - Summary, by Loan Portfo

Loans - Summary, by Loan Portfolio Segment, of Activity in Allowance for Loan Losses (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period				$ 240.4				$ 234.4	$ 240.4	$ 234.4	$ 229.3
Charge-offs									(31.5)	(30.9)	(27.9)
Recoveries									9.4	6.9	7
Net loan charge-offs									(22.1)	(24)	(20.9)
Provision for loan losses	$ 7.3	$ 7.8	$ 7.6	5.6	$ 9.9	$ 8.2	$ 6.5	5.4	28.3	30	26
Balance at end of period	246.6				240.4				246.6	240.4	234.4
Commercial [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period				209.5				204.5	209.5	204.5	204.9
Charge-offs									(27.5)	(27.6)	(21.5)
Recoveries									6.3	4.8	4.9
Net loan charge-offs									(21.2)	(22.8)	(16.6)
Provision for loan losses									29.6	27.8	16.2
Balance at end of period	217.9				209.5				217.9	209.5	204.5
Commercial [Member] | Originated [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period				205.6				201.1	205.6	201.1	198.8
Charge-offs									(20)	(19.5)	(17.1)
Recoveries									5	3.5	4.6
Net loan charge-offs									(15)	(16)	(12.5)
Provision for loan losses									26.2	20.5	14.8
Balance at end of period	216.8				205.6				216.8	205.6	201.1
Commercial [Member] | Acquired Loans [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period				3.9				3.4	3.9	3.4	6.1
Charge-offs									(7.5)	(8.1)	(4.4)
Recoveries									1.3	1.3	0.3
Net loan charge-offs									(6.2)	(6.8)	(4.1)
Provision for loan losses									3.4	7.3	1.4
Balance at end of period	1.1				3.9				1.1	3.9	3.4
Retail Loans [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period				30.9				29.9	30.9	29.9	24.4
Charge-offs									(4)	(3.3)	(6.4)
Recoveries									3.1	2.1	2.1
Net loan charge-offs									(0.9)	(1.2)	(4.3)
Provision for loan losses									(1.3)	2.2	9.8
Balance at end of period	28.7				30.9				28.7	30.9	29.9
Retail Loans [Member] | Originated [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period				30.7				29.7	30.7	29.7	24.2
Charge-offs									(4)	(3.3)	(6.4)
Recoveries									3.1	2.1	2.1
Net loan charge-offs									(0.9)	(1.2)	(4.3)
Provision for loan losses									(1.1)	2.2	9.8
Balance at end of period	28.7				30.7				28.7	30.7	29.7
Retail Loans [Member] | Acquired Loans [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period				$ 0.2				$ 0.2	0.2	0.2	0.2
Charge-offs									0	0	0
Recoveries									0	0	0
Net loan charge-offs									0	0	0
Provision for loan losses									(0.2)	0	0
Balance at end of period	$ 0				$ 0.2				$ 0	$ 0.2	$ 0.2

Loans - Summary of Allowance fo

Loans - Summary of Allowance for Loan Losses by Loan Portfolio Segment and Impairment Methodology (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	$ 43,596.1	$ 35,241.4
Allowance Total	246.6	240.4	$ 234.4	$ 229.3
Originated [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Collectively evaluated for impairment, Portfolio	32,531.1	30,435.1
Individually evaluated for impairment, Portfolio	204.2	214.9
Total loans	32,735.4	30,650
Collectively evaluated for impairment, Allowance	234.3	227.3
Individually evaluated for impairment, Allowance	11.2	9
PCI [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	396	399.9
Allowance Total	0	2.3
Purchased Performing [Member] | Purchased Performing Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Collectively evaluated for impairment, Portfolio	10,449.7	4,183.5
Individually evaluated for impairment, Portfolio	15.1	8
Collectively evaluated for impairment, Allowance	1.1	1.7
Individually evaluated for impairment, Allowance	0	0.1
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	30,714.3	25,077.7
Allowance Total	217.9	209.5	204.5	204.9
Commercial [Member] | Originated [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Collectively evaluated for impairment, Portfolio	22,938.3	21,900.1
Individually evaluated for impairment, Portfolio	115	128.4
Total loans	24,481.7	22,028.5
Collectively evaluated for impairment, Allowance	207.8	198.9
Individually evaluated for impairment, Allowance	9	6.7
Allowance Total	216.8	205.6	201.1	198.8
Commercial [Member] | PCI [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	308.5	300.3
Allowance Total	0	2.2
Commercial [Member] | Purchased Performing [Member] | Purchased Performing Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Collectively evaluated for impairment, Portfolio	7,344.9	2,744.4
Individually evaluated for impairment, Portfolio	7.6	4.5
Collectively evaluated for impairment, Allowance	1.1	1.7
Individually evaluated for impairment, Allowance	0	0
Retail Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	12,881.8	10,163.7
Allowance Total	28.7	30.9	29.9	24.4
Retail Loans [Member] | Originated [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Collectively evaluated for impairment, Portfolio	9,592.8	8,535
Individually evaluated for impairment, Portfolio	89.2	86.5
Total loans	8,253.7	8,621.5
Collectively evaluated for impairment, Allowance	26.5	28.4
Individually evaluated for impairment, Allowance	2.2	2.3
Allowance Total	28.7	30.7	$ 29.7	$ 24.2
Retail Loans [Member] | PCI [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	87.5	99.6
Allowance Total	0	0.1
Retail Loans [Member] | Purchased Performing [Member] | Purchased Performing Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Collectively evaluated for impairment, Portfolio	3,104.8	1,439.1
Individually evaluated for impairment, Portfolio	7.5	3.5
Collectively evaluated for impairment, Allowance	0	0
Individually evaluated for impairment, Allowance	$ 0	$ 0.1

Loans - Summarized Recorded Inv

Loans - Summarized Recorded Investments, by Class of Loan, in Originated Non-Performing Loans (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investments, non-performing loans	$ 157	$ 167.7	$ 148.7
Government guarantees	1.3	1.9	3.1
Foreclosure [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investments, non-performing loans	17	24.8	15.2
Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investments, non-performing loans	$ 108.1	113.5	100.6
Guarantee rate	95.00%
Retail Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investments, non-performing loans	$ 48.9	54.2	48.1
Guarantee rate	5.00%
Commercial Real Estate Loan [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investments, non-performing loans	$ 29.8	33.5	23.7
Commercial and Industrial [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investments, non-performing loans	32.1	38	32.6
Equipment Financing [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investments, non-performing loans	46.2	42	44.3
Residential Mortgage Loan [Member] | Retail Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investments, non-performing loans	36.3	38.9	32.7
Home Equity Loan [Member] | Retail Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investments, non-performing loans	12.6	15.3	15.4
Other Consumer [Member] | Retail Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investments, non-performing loans	$ 0	$ 0	$ 0

Loans - Summary of Recorded Inv

Loans - Summary of Recorded Investments in TDRs by Class of Loan (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2019USD ($)contract	Dec. 31, 2018USD ($)contract
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	269	208
Pre-Modification Outstanding Recorded Investment	$ 109.3	$ 149.1
Post-Modification Outstanding Recorded Investment	109.3	149.1
Recorded investment	$ 109.3	$ 149.1
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	82	91
Pre-Modification Outstanding Recorded Investment	$ 74	$ 132.3
Post-Modification Outstanding Recorded Investment	74	132.3
Recorded investment	$ 74	$ 132.3
Retail Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	187	117
Pre-Modification Outstanding Recorded Investment	$ 35.3	$ 16.8
Post-Modification Outstanding Recorded Investment	35.3	16.8
Recorded investment	$ 35.3	$ 16.8
Commercial Real Estate Loan [Member] | Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	12	13
Pre-Modification Outstanding Recorded Investment	$ 17.2	$ 27.6
Post-Modification Outstanding Recorded Investment	17.2	27.6
Recorded investment	$ 17.2	$ 27.6
Commercial Real Estate Loan [Member] | Commercial [Member] | Extended Maturity [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	7	9
Post-Modification Outstanding Recorded Investment	$ 2.1	$ 24.1
Recorded investment	$ 2.1	$ 24.1
Commercial Real Estate Loan [Member] | Commercial [Member] | Payment Deferral [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	1	1
Post-Modification Outstanding Recorded Investment	$ 0.6	$ 0.5
Recorded investment	$ 0.6	$ 0.5
Commercial Real Estate Loan [Member] | Commercial [Member] | Combination of Concessions [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	4	3
Post-Modification Outstanding Recorded Investment	$ 14.5	$ 3
Recorded investment	$ 14.5	$ 3
Commercial and Industrial [Member] | Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	33	47
Pre-Modification Outstanding Recorded Investment	$ 31.9	$ 73.1
Post-Modification Outstanding Recorded Investment	31.9	73.1
Recorded investment	$ 31.9	$ 73.1
Commercial and Industrial [Member] | Commercial [Member] | Extended Maturity [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	26	31
Post-Modification Outstanding Recorded Investment	$ 26.4	$ 48.4
Recorded investment	$ 26.4	$ 48.4
Commercial and Industrial [Member] | Commercial [Member] | Payment Deferral [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	3	11
Post-Modification Outstanding Recorded Investment	$ 0.8	$ 23.8
Recorded investment	$ 0.8	$ 23.8
Commercial and Industrial [Member] | Commercial [Member] | Combination of Concessions [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	4	5
Post-Modification Outstanding Recorded Investment	$ 4.7	$ 0.9
Recorded investment	$ 4.7	$ 0.9
Equipment Financing [Member] | Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	37	31
Pre-Modification Outstanding Recorded Investment	$ 24.9	$ 31.6
Post-Modification Outstanding Recorded Investment	24.9	31.6
Recorded investment	$ 24.9	$ 31.6
Equipment Financing [Member] | Commercial [Member] | Extended Maturity [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	5	3
Post-Modification Outstanding Recorded Investment	$ 1.6	$ 4.2
Recorded investment	$ 1.6	$ 4.2
Equipment Financing [Member] | Commercial [Member] | Payment Deferral [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	26	16
Post-Modification Outstanding Recorded Investment	$ 18.9	$ 17.6
Recorded investment	$ 18.9	$ 17.6
Equipment Financing [Member] | Commercial [Member] | Combination of Concessions [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	6	12
Post-Modification Outstanding Recorded Investment	$ 4.4	$ 9.8
Recorded investment	$ 4.4	$ 9.8
Residential Mortgage Loan [Member] | Commercial [Member] | Foreclosure or Bankruptcy [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract		21
Residential Mortgage Loan [Member] | Commercial [Member] | Bankruptcy [Member]
Financing Receivable, Modifications [Line Items]
Post-Modification Outstanding Recorded Investment		$ 3.7
Recorded investment		$ 3.7
Residential Mortgage Loan [Member] | Retail Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	85	38
Pre-Modification Outstanding Recorded Investment	$ 26.3	$ 9.5
Post-Modification Outstanding Recorded Investment	26.3	9.5
Recorded investment	$ 26.3	$ 9.5
Residential Mortgage Loan [Member] | Retail Loans [Member] | Payment Deferral [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	24	10
Post-Modification Outstanding Recorded Investment	$ 10.1	$ 3.5
Recorded investment	$ 10.1	$ 3.5
Residential Mortgage Loan [Member] | Retail Loans [Member] | Combination of Concessions [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	16	7
Post-Modification Outstanding Recorded Investment	$ 6.3	$ 2.3
Recorded investment	$ 6.3	$ 2.3
Residential Mortgage Loan [Member] | Retail Loans [Member] | Bankruptcy [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	45
Post-Modification Outstanding Recorded Investment	$ 9.9
Recorded investment	$ 9.9
Home Equity Loan [Member] | Retail Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	102	79
Pre-Modification Outstanding Recorded Investment	$ 9	$ 7.3
Post-Modification Outstanding Recorded Investment	9	7.3
Recorded investment	$ 9	$ 7.3
Home Equity Loan [Member] | Retail Loans [Member] | Payment Deferral [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	18	10
Post-Modification Outstanding Recorded Investment	$ 2.9	$ 1.3
Recorded investment	$ 2.9	$ 1.3
Home Equity Loan [Member] | Retail Loans [Member] | Combination of Concessions [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	30	20
Post-Modification Outstanding Recorded Investment	$ 2.9	$ 2.4
Recorded investment	$ 2.9	$ 2.4
Home Equity Loan [Member] | Retail Loans [Member] | Bankruptcy [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	54	49
Post-Modification Outstanding Recorded Investment	$ 3.2	$ 3.6
Recorded investment	$ 3.2	$ 3.6
Other Consumer [Member] | Retail Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	0	0
Pre-Modification Outstanding Recorded Investment	$ 0	$ 0
Post-Modification Outstanding Recorded Investment	0	0
Recorded investment	$ 0	$ 0

Loans - Summary of Recorded I_2

Loans - Summary of Recorded Investments in TDRs by Class of Loan, Subsequently Defaulted (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2019USD ($)contract	Dec. 31, 2018USD ($)contract
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	27	38
Recorded Investment | $	$ 10.9	$ 12.5
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	10	18
Recorded Investment | $	$ 7.7	$ 10.2
Commercial [Member] | Commercial Real Estate Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	0	0
Recorded Investment | $	$ 0	$ 0
Commercial [Member] | Commercial and Industrial [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	2	12
Recorded Investment | $	$ 2.4	$ 6.7
Commercial [Member] | Equipment Financing [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	8	6
Recorded Investment | $	$ 5.3	$ 3.5
Retail Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	17	20
Recorded Investment | $	$ 3.2	$ 2.3
Retail Loans [Member] | Residential Mortgage Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	5	7
Recorded Investment | $	$ 2.2	$ 1.6
Retail Loans [Member] | Home Equity Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	12	13
Recorded Investment | $	$ 1	$ 0.7
Retail Loans [Member] | Other Consumer [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | contract	0	0
Recorded Investment | $	$ 0	$ 0

Loans - Summary of Individually

Loans - Summary of Individually-Evaluated Impaired Loans by Class of Loan (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Impaired [Line Items]
With no related allowance for loan losses, Unpaid Principal Balance	$ 178.4	$ 187.4
With no related allowance for loan losses, Recorded Investment	157.4	167.7
With a related allowance for loan losses, Unpaid Principal Balance	66.9	63.1
With a related allowance for loan losses, Recorded Investment	61.9	55.2
Related Allowance for Loan Losses	11.2	9.1
Unpaid Principal Balance	245.3	250.5
Recorded Investment	219.3	222.9
Commercial [Member]
Financing Receivable, Impaired [Line Items]
With a related allowance for loan losses, Recorded Investment	49
Related Allowance for Loan Losses	9	6.7
Unpaid Principal Balance	137.9	149.4
Recorded Investment	122.6	132.9
Commercial [Member] | Commercial Real Estate Loan [Member]
Financing Receivable, Impaired [Line Items]
With no related allowance for loan losses, Unpaid Principal Balance	28.9	31
With no related allowance for loan losses, Recorded Investment	25.9	28.1
With a related allowance for loan losses, Unpaid Principal Balance	21.5	23.8
With a related allowance for loan losses, Recorded Investment	21	21.8
Related Allowance for Loan Losses	3.4	1.6
Unpaid Principal Balance	50.4	54.8
Recorded Investment	46.9	49.9
Commercial [Member] | Commercial and Industrial [Member]
Financing Receivable, Impaired [Line Items]
With no related allowance for loan losses, Unpaid Principal Balance	31	45.6
With no related allowance for loan losses, Recorded Investment	25.9	42
With a related allowance for loan losses, Unpaid Principal Balance	20	12.6
With a related allowance for loan losses, Recorded Investment	16.4	10.2
Related Allowance for Loan Losses	3.9	2.4
Unpaid Principal Balance	51	58.2
Recorded Investment	42.3	52.2
Commercial [Member] | Equipment Financing [Member]
Financing Receivable, Impaired [Line Items]
With no related allowance for loan losses, Unpaid Principal Balance	24.1	20.2
With no related allowance for loan losses, Recorded Investment	21.8	18
With a related allowance for loan losses, Unpaid Principal Balance	12.4	16.2
With a related allowance for loan losses, Recorded Investment	11.6	12.8
Related Allowance for Loan Losses	1.7	2.7
Unpaid Principal Balance	36.5	36.4
Recorded Investment	33.4	30.8
Retail Loans [Member]
Financing Receivable, Impaired [Line Items]
With a related allowance for loan losses, Recorded Investment	12.9
Related Allowance for Loan Losses	2.2	2.4
Unpaid Principal Balance	107.4	101.1
Recorded Investment	96.7	90
Retail Loans [Member] | Residential Mortgage Loan [Member]
Financing Receivable, Impaired [Line Items]
With no related allowance for loan losses, Unpaid Principal Balance	68.4	66.8
With no related allowance for loan losses, Recorded Investment	60.8	59.3
With a related allowance for loan losses, Unpaid Principal Balance	11.6	8.8
With a related allowance for loan losses, Recorded Investment	11.5	8.8
Related Allowance for Loan Losses	1.5	1.7
Unpaid Principal Balance	80	75.6
Recorded Investment	72.3	68.1
Retail Loans [Member] | Home Equity Loan [Member]
Financing Receivable, Impaired [Line Items]
With no related allowance for loan losses, Unpaid Principal Balance	26	23.8
With no related allowance for loan losses, Recorded Investment	23	20.3
With a related allowance for loan losses, Unpaid Principal Balance	1.4	1.7
With a related allowance for loan losses, Recorded Investment	1.4	1.6
Related Allowance for Loan Losses	0.7	0.7
Unpaid Principal Balance	27.4	25.5
Recorded Investment	24.4	21.9
Retail Loans [Member] | Other Consumer [Member]
Financing Receivable, Impaired [Line Items]
With no related allowance for loan losses, Unpaid Principal Balance	0	0
With no related allowance for loan losses, Recorded Investment	0	0
With a related allowance for loan losses, Unpaid Principal Balance	0	0
With a related allowance for loan losses, Recorded Investment	0	0
Related Allowance for Loan Losses	0	0
Unpaid Principal Balance	0	0
Recorded Investment	$ 0	$ 0

Loans - Schedule of Impaired Fi

Loans - Schedule of Impaired Financing Receivable (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	$ 202.4	$ 217.8	$ 256.6
Interest Income Recognized	5.7	6.4	5.6
Commercial [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	111.1	128.2	163.6
Interest Income Recognized	3	4	3.5
Commercial [Member] | Commercial Real Estate Loan [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	39.6	40.2	55.8
Interest Income Recognized	1.1	1.1	1.2
Commercial [Member] | Commercial and Industrial [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	44.5	49.6	63.4
Interest Income Recognized	1.6	2.8	1.9
Commercial [Member] | Equipment Financing [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	27	38.4	44.4
Interest Income Recognized	0.3	0.1	0.4
Retail Loans [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	91.3	89.6	93
Interest Income Recognized	2.7	2.4	2.1
Retail Loans [Member] | Residential Mortgage Loan [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	68.3	68.7	71.8
Interest Income Recognized	2.1	1.9	1.7
Retail Loans [Member] | Home Equity Loan [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	23	20.9	21.2
Interest Income Recognized	0.6	0.5	0.4
Retail Loans [Member] | Other Consumer [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	0	0	0
Interest Income Recognized	$ 0	$ 0	$ 0

Loans - Summary of Aging Inform

Loans - Summary of Aging Information by Class of Loan (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	$ 43,596.1	$ 35,241.4
Originated [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	32,501.7	30,420.8
Past Due	233.7	229.2
Total loans	32,735.4	30,650
Originated [Member] | 30-89 Days [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	149.8	143.2
Originated [Member] | 90 Days or More [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	83.9	86
Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	30,714.3	25,077.7
Commercial [Member] | Commercial Real Estate Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	14,762.3	11,649.6
Commercial [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	11,041.6	9,088.9
Commercial [Member] | Equipment Financing [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	4,910.4	4,339.2
Commercial [Member] | Originated [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	24,312.9	21,878.9
Past Due	168.8	149.6
Total loans	24,481.7	22,028.5
Commercial [Member] | Originated [Member] | Commercial Real Estate Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	9,983.5	9,762.1
Past Due	29	36.4
Total loans	10,012.5	9,798.5
Commercial [Member] | Originated [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	9,738	8,261.5
Past Due	25.1	30.8
Total loans	9,763.1	8,292.3
Commercial [Member] | Originated [Member] | Equipment Financing [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	4,591.4	3,855.3
Past Due	114.7	82.4
Total loans	4,706.1	3,937.7
Commercial [Member] | Originated [Member] | 30-89 Days [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	113	98.7
Commercial [Member] | Originated [Member] | 30-89 Days [Member] | Commercial Real Estate Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	7.8	23
Commercial [Member] | Originated [Member] | 30-89 Days [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	10.5	6.9
Commercial [Member] | Originated [Member] | 30-89 Days [Member] | Equipment Financing [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	94.7	68.8
Commercial [Member] | Originated [Member] | 90 Days or More [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	55.8	50.9
Commercial [Member] | Originated [Member] | 90 Days or More [Member] | Commercial Real Estate Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	21.2	13.4
Commercial [Member] | Originated [Member] | 90 Days or More [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	14.6	23.9
Commercial [Member] | Originated [Member] | 90 Days or More [Member] | Equipment Financing [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	20	13.6
Retail Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	12,881.8	10,163.7
Retail Loans [Member] | Residential Mortgage Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	10,318.1	8,154.2
Retail Loans [Member] | Home Equity Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	2,406.5	1,962.5
Retail Loans [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	157.2	47
Retail Loans [Member] | Originated [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	8,188.8	8,541.9
Past Due	64.9	79.6
Total loans	8,253.7	8,621.5
Retail Loans [Member] | Originated [Member] | Residential Mortgage Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	6,534.3	6,723.2
Past Due	54.6	66
Total loans	6,588.9	6,789.2
Retail Loans [Member] | Originated [Member] | Home Equity Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	1,615	1,776
Past Due	10.1	13.5
Total loans	1,625.1	1,789.5
Retail Loans [Member] | Originated [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	39.5	42.7
Past Due	0.2	0.1
Total loans	39.7	42.8
Retail Loans [Member] | Originated [Member] | 30-89 Days [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	36.8	44.5
Retail Loans [Member] | Originated [Member] | 30-89 Days [Member] | Residential Mortgage Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	31.6	38.6
Retail Loans [Member] | Originated [Member] | 30-89 Days [Member] | Home Equity Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	5	5.8
Retail Loans [Member] | Originated [Member] | 30-89 Days [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0.2	0.1
Retail Loans [Member] | Originated [Member] | 90 Days or More [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	28.1	35.1
Retail Loans [Member] | Originated [Member] | 90 Days or More [Member] | Residential Mortgage Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	23	27.4
Retail Loans [Member] | Originated [Member] | 90 Days or More [Member] | Home Equity Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	5.1	7.7
Retail Loans [Member] | Originated [Member] | 90 Days or More [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	$ 0	$ 0

Loans - Summary of Credit Quali

Loans - Summary of Credit Quality Indicators by Class of Loan (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	$ 43,596.1	$ 35,241.4
Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	30,714.3	25,077.7
Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	12,881.8	10,163.7
Originated [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	24,481.7	22,028.5
Originated [Member] | Commercial [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	23,191.5	21,012
Originated [Member] | Commercial [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	568.9	394.5
Originated [Member] | Commercial [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	716.1	620.8
Originated [Member] | Commercial [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	5.2	1.2
Originated [Member] | Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	8,253.7	8,621.5
Originated [Member] | Retail Loans [Member] | Low Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	3,997.5	3,774.6
Originated [Member] | Retail Loans [Member] | Moderate Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	3,203.4	3,943.2
Originated [Member] | Retail Loans [Member] | High Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	1,052.8	903.7
Acquired Loans [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	6,232.6	3,049.2
Acquired Loans [Member] | Commercial [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	5,856	2,879.8
Acquired Loans [Member] | Commercial [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	172.3	46.6
Acquired Loans [Member] | Commercial [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	202.7	122.8
Acquired Loans [Member] | Commercial [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	1.6	0
Acquired Loans [Member] | Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	4,628.1	1,542.2
Acquired Loans [Member] | Retail Loans [Member] | Low Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	1,184.7	506.1
Acquired Loans [Member] | Retail Loans [Member] | Moderate Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	2,309.3	639.6
Acquired Loans [Member] | Retail Loans [Member] | High Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	1,134.1	396.5
Commercial Real Estate Loan [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	14,762.3	11,649.6
Commercial Real Estate Loan [Member] | Originated [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	10,012.5	9,798.5
Commercial Real Estate Loan [Member] | Originated [Member] | Commercial [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	9,736.4	9,607
Commercial Real Estate Loan [Member] | Originated [Member] | Commercial [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	197.6	105.5
Commercial Real Estate Loan [Member] | Originated [Member] | Commercial [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	75.4	85.2
Commercial Real Estate Loan [Member] | Originated [Member] | Commercial [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	3.1	0.8
Commercial Real Estate Loan [Member] | Acquired Loans [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	4,749.8	1,851.1
Commercial Real Estate Loan [Member] | Acquired Loans [Member] | Commercial [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	4,485.9	1,766.2
Commercial Real Estate Loan [Member] | Acquired Loans [Member] | Commercial [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	136.7	27.3
Commercial Real Estate Loan [Member] | Acquired Loans [Member] | Commercial [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	127.2	57.6
Commercial Real Estate Loan [Member] | Acquired Loans [Member] | Commercial [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	0	0
Commercial and Industrial [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	11,041.6	9,088.9
Commercial and Industrial [Member] | Originated [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	9,763.1	8,292.3
Commercial and Industrial [Member] | Originated [Member] | Commercial [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	9,223.5	7,855.7
Commercial and Industrial [Member] | Originated [Member] | Commercial [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	294.8	196.9
Commercial and Industrial [Member] | Originated [Member] | Commercial [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	242.7	239.3
Commercial and Industrial [Member] | Originated [Member] | Commercial [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	2.1	0.4
Commercial and Industrial [Member] | Acquired Loans [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	1,278.5	796.6
Commercial and Industrial [Member] | Acquired Loans [Member] | Commercial [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	1,168.2	719.6
Commercial and Industrial [Member] | Acquired Loans [Member] | Commercial [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	35.6	14.6
Commercial and Industrial [Member] | Acquired Loans [Member] | Commercial [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	73.1	62.4
Commercial and Industrial [Member] | Acquired Loans [Member] | Commercial [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	1.6	0
Equipment Financing [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	4,910.4	4,339.2
Equipment Financing [Member] | Originated [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	4,706.1	3,937.7
Equipment Financing [Member] | Originated [Member] | Commercial [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	4,231.6	3,549.3
Equipment Financing [Member] | Originated [Member] | Commercial [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	76.5	92.1
Equipment Financing [Member] | Originated [Member] | Commercial [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	398	296.3
Equipment Financing [Member] | Originated [Member] | Commercial [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	0	0
Equipment Financing [Member] | Acquired Loans [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	204.3	401.5
Equipment Financing [Member] | Acquired Loans [Member] | Commercial [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	201.9	394
Equipment Financing [Member] | Acquired Loans [Member] | Commercial [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	0	4.7
Equipment Financing [Member] | Acquired Loans [Member] | Commercial [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	2.4	2.8
Equipment Financing [Member] | Acquired Loans [Member] | Commercial [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	0	0
Residential Mortgage Loan [Member] | Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	10,318.1	8,154.2
Residential Mortgage Loan [Member] | Originated [Member] | Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	6,588.9	6,789.2
Residential Mortgage Loan [Member] | Originated [Member] | Retail Loans [Member] | Low Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	3,225.3	2,912.8
Residential Mortgage Loan [Member] | Originated [Member] | Retail Loans [Member] | Moderate Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	2,649	3,360.9
Residential Mortgage Loan [Member] | Originated [Member] | Retail Loans [Member] | High Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	714.6	515.5
Residential Mortgage Loan [Member] | Acquired Loans [Member] | Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	3,729.2	1,365
Residential Mortgage Loan [Member] | Acquired Loans [Member] | Retail Loans [Member] | Low Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	1,184.7	506.1
Residential Mortgage Loan [Member] | Acquired Loans [Member] | Retail Loans [Member] | Moderate Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	2,309.3	639.6
Residential Mortgage Loan [Member] | Acquired Loans [Member] | Retail Loans [Member] | High Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	235.2	219.3
Home Equity Loan [Member] | Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	2,406.5	1,962.5
Home Equity Loan [Member] | Originated [Member] | Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	1,625.1	1,789.5
Home Equity Loan [Member] | Originated [Member] | Retail Loans [Member] | Low Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	747.3	834.5
Home Equity Loan [Member] | Originated [Member] | Retail Loans [Member] | Moderate Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	548.5	576.4
Home Equity Loan [Member] | Originated [Member] | Retail Loans [Member] | High Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	329.3	378.6
Home Equity Loan [Member] | Acquired Loans [Member] | Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	781.4	173
Home Equity Loan [Member] | Acquired Loans [Member] | Retail Loans [Member] | Low Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	0	0
Home Equity Loan [Member] | Acquired Loans [Member] | Retail Loans [Member] | Moderate Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	0	0
Home Equity Loan [Member] | Acquired Loans [Member] | Retail Loans [Member] | High Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	781.4	173
Other Consumer [Member] | Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	157.2	47
Other Consumer [Member] | Originated [Member] | Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	39.7	42.8
Other Consumer [Member] | Originated [Member] | Retail Loans [Member] | Low Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	24.9	27.3
Other Consumer [Member] | Originated [Member] | Retail Loans [Member] | Moderate Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	5.9	5.9
Other Consumer [Member] | Originated [Member] | Retail Loans [Member] | High Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	8.9	9.6
Other Consumer [Member] | Acquired Loans [Member] | Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	117.5	4.2
Other Consumer [Member] | Acquired Loans [Member] | Retail Loans [Member] | Low Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	0	0
Other Consumer [Member] | Acquired Loans [Member] | Retail Loans [Member] | Moderate Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	0	0
Other Consumer [Member] | Acquired Loans [Member] | Retail Loans [Member] | High Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	$ 117.5	$ 4.2

Loans - Summarized Activity in

Loans - Summarized Activity in Accretable Yield for PCI Loan Portfolio (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Balance at beginning of period	$ 189.7	$ 219.7	$ 255.4
Acquisitions	25.5	27.1	13.1
Accretion	(21)	(24.6)	(29.1)
Reclassification from nonaccretable difference for loans with improved cash flows	0	0	0
Other changes in expected cash flows	(56.7)	(32.5)	(19.7)
Balance at end of period	$ 137.5	$ 189.7	$ 219.7

Leases - Net Investment in Leas

Leases - Net Investment in Lease Financing Receivables (Details) $ in Millions	Dec. 31, 2019USD ($)
Leases [Abstract]
Lease payments receivable	$ 1,417.1
Estimated residual value of leased assets	128
Gross investment in lease financing receivables	1,545.1
Plus: Deferred origination costs	13.4
Less: Unearned income	(156.9)
Total net investment in lease financing receivables	$ 1,401.6

Leases - Contractual Maturities

Leases - Contractual Maturities of Lease Financing Receivables (Details) $ in Millions	Dec. 31, 2019USD ($)
Leases [Abstract]
2020	$ 518.8
2021	414.2
2022	303.3
2023	178.5
2024	93.6
Later years	36.7
Gross investment in lease financing receivables	$ 1,545.1

Leases - Components of Lease Co

Leases - Components of Lease Cost and Supplemental Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019USD ($)
Leases [Abstract]
Operating lease cost	$ 61.6
Variable lease cost	8.6
Finance lease cost	0.1
Sublease income	(1.4)
Net lease cost	68.9
Lease ROU assets:
Operating lease	276.6
Finance lease	2.6
Lease liabilities:
Operating lease	307.9
Finance lease	5.3
Cash payments included in the measurement of lease liabilities:
Reported in operating cash from operating leases	61.7
Reported in financing cash from finance leases	0.1
ROU assets obtained in exchange for lessee:
Operating lease liabilities	89.1
Finance lease liabilities	$ 2.6
Weighted-average discount rate:
Operating leases	3.13%
Finance leases	2.58%
Weighted-average remaining lease term (in years):
Operating leases	7 years 8 months 12 days
Finance leases	12 years 2 months 12 days

Leases - Contractual Maturiti_2

Leases - Contractual Maturities of Lease Liabilities (Details) $ in Millions	Dec. 31, 2019USD ($)
Operating Leases
2020	$ 66.6
2021	63.9
2022	46.3
2023	33.9
2024	28.3
Later years	111.8
Total lease payments	350.8
Less: Interest	(42.9)
Operating lease	307.9
Finance Leases
2020	0.5
2021	0.5
2022	0.5
2023	0.5
2024	3.7
Later years	0.5
Total lease payments	6.2
Less: Interest	(0.9)
Finance lease	$ 5.3

Leases - Additional Information

Leases - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Leases [Abstract]
Lease income		$ 117.9
Lease financing receivables		66.7
Lease income from operating leases		51.2
Rent expense under operating leases			$ 64.2	$ 62.5
Gain on sale leaseback transaction	$ 3.3	$ 3.3

Goodwill and Other Acquisitio_3

Goodwill and Other Acquisition-Related Intangible Assets - Schedule of Changes in Carrying Amount of Goodwill (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Goodwill [Roll Forward]
Beginning balance	$ 2,685.7	$ 2,411.4
Write-down relating to the sale of branches	(6.9)
Ending balance	3,065.5	2,685.7
First Connecticut Bancorp, Inc. [Member]
Goodwill [Roll Forward]
Acquisition		250.4
Vend Lease [Member]
Goodwill [Roll Forward]
Acquisition		23.9
United Financial [Member]
Goodwill [Roll Forward]
Acquisition	204.3
BSB Bancorp [Member]
Goodwill [Roll Forward]
Acquisition	144.9
VAR Technology Finance [Member]
Goodwill [Roll Forward]
Acquisition	37.5
Commercial Banking Loan [Member]
Goodwill [Roll Forward]
Beginning balance	1,759.4	1,600.3
Write-down relating to the sale of branches	(0.6)
Ending balance	1,966.1	1,759.4
Commercial Banking Loan [Member] | First Connecticut Bancorp, Inc. [Member]
Goodwill [Roll Forward]
Acquisition		135.2
Commercial Banking Loan [Member] | Vend Lease [Member]
Goodwill [Roll Forward]
Acquisition		23.9
Commercial Banking Loan [Member] | United Financial [Member]
Goodwill [Roll Forward]
Acquisition	120.5
Commercial Banking Loan [Member] | BSB Bancorp [Member]
Goodwill [Roll Forward]
Acquisition	49.3
Commercial Banking Loan [Member] | VAR Technology Finance [Member]
Goodwill [Roll Forward]
Acquisition	37.5
Retail Banking [Member]
Goodwill [Roll Forward]
Beginning balance	835.3	720.1
Write-down relating to the sale of branches	(3.8)
Ending balance	1,010.9	835.3
Retail Banking [Member] | First Connecticut Bancorp, Inc. [Member]
Goodwill [Roll Forward]
Acquisition		115.2
Retail Banking [Member] | Vend Lease [Member]
Goodwill [Roll Forward]
Acquisition		0
Retail Banking [Member] | United Financial [Member]
Goodwill [Roll Forward]
Acquisition	83.8
Retail Banking [Member] | BSB Bancorp [Member]
Goodwill [Roll Forward]
Acquisition	95.6
Retail Banking [Member] | VAR Technology Finance [Member]
Goodwill [Roll Forward]
Acquisition	0
Wealth Management [Member]
Goodwill [Roll Forward]
Beginning balance	91	91
Write-down relating to the sale of branches	(2.5)
Ending balance	88.5	91
Wealth Management [Member] | First Connecticut Bancorp, Inc. [Member]
Goodwill [Roll Forward]
Acquisition		0
Wealth Management [Member] | Vend Lease [Member]
Goodwill [Roll Forward]
Acquisition		$ 0
Wealth Management [Member] | United Financial [Member]
Goodwill [Roll Forward]
Acquisition	0
Wealth Management [Member] | BSB Bancorp [Member]
Goodwill [Roll Forward]
Acquisition	0
Wealth Management [Member] | VAR Technology Finance [Member]
Goodwill [Roll Forward]
Acquisition	$ 0

Goodwill and Other Acquisitio_4

Goodwill and Other Acquisition-Related Intangible Assets - Other Acquisition-Related Intangibles (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Amount	$ 536.5	$ 455.5
Accumulated Amortization	327.4	292
Carrying Amount	209.1	163.5
Total other acquisition-related intangible assets	209.1	180
Mutual Fund Management Contracts [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Indefinite-lived intangible assets	0	16.5
Core Deposit Intangibles [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Amount	303.9	222.9
Accumulated Amortization	177.3	157.4
Carrying Amount	126.6	65.5
Trade Name [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Amount	123.9	123.9
Accumulated Amortization	73.4	64.8
Carrying Amount	50.5	59.1
Client Relationship [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Amount	24.4	24.4
Accumulated Amortization	6.4	4.4
Carrying Amount	18	20
Customer Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Amount	42.7	42.7
Accumulated Amortization	35.1	31.3
Carrying Amount	7.6	11.4
Insurance Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Amount	38.1	38.1
Accumulated Amortization	34.3	33.6
Carrying Amount	3.8	4.5
Favorable Lease Agreements [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Amount	2.9	2.9
Accumulated Amortization	0.6	0.3
Carrying Amount	2.3	2.6
Noncompete Agreements [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Amount	0.6	0.6
Accumulated Amortization	0.3	0.2
Carrying Amount	$ 0.3	$ 0.4

Goodwill and Other Acquisitio_5

Goodwill and Other Acquisition-Related Intangible Assets - Additional Information (Detail)	3 Months Ended	12 Months Ended
	Dec. 31, 2019USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Oct. 25, 2019branch
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill expected to be tax deductible	$ 134,400,000	$ 134,400,000	$ 90,300,000
Weighted-average amortization period		12 years
Amortization of other acquisition-related intangible assets		$ 32,500,000	21,800,000	$ 30,000,000
Impairment losses relating to goodwill or other acquisition-related intangible assets		0	$ 0	$ 0
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2020	40,900,000	40,900,000
2021	36,100,000	36,100,000
2022	31,700,000	31,700,000
2023	24,000,000	24,000,000
2024	20,300,000	$ 20,300,000
Central Maine Branch Sale [Member]
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Number of branches sold | branch					8
Mutual Fund Management Contract [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible asset write-down	16,500,000
Trade Name [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible asset write-down	1,900,000
Customer Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible asset write-down	$ 1,000,000

Premises and Equipment - Compon

Premises and Equipment - Components of Premises and Equipment (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Land	$ 49.8	$ 50.1
Buildings	330.6	300
Leasehold improvements	197.4	170.7
Furniture and equipment	324.3	279.3
Total	902.1	800.1
Less: Accumulated depreciation and amortization	596.6	532.8
Total premises and equipment, net	$ 305.5	$ 267.3

Premises and Equipment - Additi

Premises and Equipment - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Depreciation and amortization expense included in occupancy and equipment expense	$ 41.7	$ 36.3	$ 39.1

Other Assets and Other Liabil_3

Other Assets and Other Liabilities - Components of Other Assets (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Schedule Of Other Assets [Line Items]
Affordable housing investments	$ 383.9	$ 304.1
Fair value of derivative financial instruments (notes 20 and 22)	341	103
Lease ROU assets	279.2
Leased equipment	191.3	189
Accrued interest receivable	156.1	138.2
Funded status of defined benefit pension plans	121.4	78
Loan disbursements in process	65.8	17.9
Current income tax receivable	51.7	31.4
Assets held in trust for supplemental retirement plans	51	56.4
Net deferred tax asset	33.6	11.4
Other prepaid expenses	32.6	27.5
Economic development investments	29.2	26.2
Investment in joint venture	16.3	17.2
Receivables arising from securities brokerage and insurance businesses	13	26.4
Mortgage servicing rights	10.6	0
Repossessed assets	4.2	3.9
Other	52.9	46.8
Total other assets	1,853	1,091.6
Residential Mortgage Loan [Member]
Schedule Of Other Assets [Line Items]
REO	11.9	5.5
Commercial Real Estate Loan [Member]
Schedule Of Other Assets [Line Items]
REO	$ 7.3	$ 8.7

Other Assets and Other Liabil_4

Other Assets and Other Liabilities - Components of Other Liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Other Assets And Other Liabilities [Abstract]
Lease liabilities	$ 313.2
Future contingent commitments for affordable housing investments	141.1	$ 119.7
Accrued expenses payable	104.3	87.9
Fair value of derivative financial instruments (notes 20 and 22)	96.2	139
Liabilities for supplemental retirement plans	84.4	86.6
Accrued employee benefits	74.8	66.6
Accrued interest payable	21.7	25.4
Loan payments in process	18.8	51.2
Other postretirement plans	18.7	15.3
Payables arising from securities brokerage and insurance businesses	9.6	29.7
Other	22.7	73.8
Total other liabilities	$ 905.5	$ 695.2

Deposits - Schedule of Deposits

Deposits - Schedule of Deposits (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Amount
Non-interest-bearing	$ 9,803.7	$ 8,543
Savings	4,987.7	4,116.5
Interest-bearing checking and money market	19,592.6	16,583.3
Time deposits maturing:
Within 3 months	3,984.7	1,480
After 3 but within 6 months	2,659.3	1,375.6
After 6 months but within 1 year	1,354.8	2,511.5
After 1 but within 2 years	816.3	1,275.5
After 2 but within 3 years	275.4	153.5
After 3 but within 4 years	97.8	102.1
After 4 but within 5 years	17.2	18
After 5 years (less than $0.1 million)	0	0
Total	9,205.5	6,916.2
Total deposits	$ 43,589.5	$ 36,159
Weighted- Average Rate
Non-interest-bearing	0.00%	0.00%
Savings	0.23%	0.09%
Interest-bearing checking and money market	0.92%	1.04%
Time deposits maturing:
Within 3 months	1.90%	1.66%
After 3 but within 6 months	2.12%	1.67%
After 6 months but within 1 year	1.77%	1.83%
After 1 but within 2 years	1.82%	1.98%
After 2 but within 3 years	2.23%	1.97%
After 3 but within 4 years	2.37%	1.63%
After 4 but within 5 years	1.09%	1.29%
After 5 years	0.99%	1.01%
Total	1.95%	1.78%
Total deposits	0.85%	0.83%
Maximum [Member]
Time deposits maturing:
After 5 years (less than $0.1 million)	$ 0.1	$ 0.1

Deposits - Additional Informati

Deposits - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Banking and Thrift [Abstract]
Time deposits issued in amounts that exceed $250,000	$ 1,900	$ 1,100
Non-interest-bearing deposit overdrafts	$ 4	$ 2.7

Deposits - Schedule of Interest

Deposits - Schedule of Interest Expense on Deposits (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Banking and Thrift [Abstract]
Savings	$ 13.4	$ 7.2	$ 9.7
Interest-bearing checking and money market	195.9	120.2	70.4
Time	147.6	88.7	50.6
Total	$ 356.9	$ 216.1	$ 130.7

Borrowings - Summary of Borrowi

Borrowings - Summary of Borrowings (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fixed-rate FHLB advances maturing:
Within 1 month	$ 3,060.8	$ 2,270.3
After 1 month but within 1 year	44.8	61
After 1 but within 2 years	6.8	54.2
After 2 but within 3 years	1.2	6.8
After 3 but within 4 years	0.6	1.3
After 4 but within 5 years	0	0.6
After 5 years	11.2	10.3
Total FHLB advances	3,125.4	2,404.5	$ 2,774.4
Federal funds purchased maturing:
Within 1 month	1,620	845
Total federal funds purchased	1,620	845	820
Customer repurchase agreements maturing:
Within 1 month	409.1	332.9
Total customer repurchase agreements	409.1	332.9	301.6
Other borrowings maturing:
Within 1 year	0	11
Total other borrowings	0	11	$ 207.8
Total borrowings	$ 5,154.5	$ 3,593.4
Fixed-rate FHLB advances maturing, weighted average rate
Within 1 month	1.79%	2.59%
After 1 month but within 1 year	1.79%	1.76%
After 1 but within 2 years	2.11%	1.75%
After 2 but within 3 years	0.51%	2.11%
After 3 but within 4 years	0.05%	0.52%
After 4 but within 5 years	0.00%	0.05%
After 5 years	1.50%	1.64%
Total FHLB advances	1.79%	2.54%
Federal funds purchased maturing, weighted average rate
Within 1 month	1.61%	2.53%
Total federal funds purchased	1.61%	2.53%
Customer repurchase agreements maturing:
Within 1 month	0.69%	0.61%
Total customer repurchase agreements	0.69%	0.61%
Other borrowings maturing:
Within 1 year	0.00%	2.40%
Total other borrowings	0.00%	2.40%
Total borrowings, weighted average rate	1.64%	2.36%

Borrowings - Additional Informa

Borrowings - Additional Information (Detail) $ in Billions	Dec. 31, 2019USD ($)
Debt Disclosure [Abstract]
Repurchase agreements and advances borrowing limit	$ 12.7
Unsecured borrowing capacity	$ 1.7

Borrowings - Interest Expense o

Borrowings - Interest Expense on Borrowings (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt Disclosure [Abstract]
FHLB advances	$ 50.1	$ 54.5	$ 31.5
Federal funds purchased	24.6	13.6	7.1
Customer repurchase agreements	2.2	1	0.6
Other borrowings	0.1	1.8	2.1
Total	$ 77	$ 70.9	$ 41.3

Borrowings - Information Concer

Borrowings - Information Concerning Parent Company Borrowings (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
FHLB advances:
Balance at year end	$ 3,125.4	$ 2,404.5	$ 2,774.4
Average outstanding during the year	2,098	2,653.6	2,677.5
Maximum outstanding at any month end	$ 3,125.5	$ 3,510.1	$ 3,130.8
Average interest rate during the year	2.39%	2.05%	1.17%
Federal funds purchased:
Balance at year end	$ 1,620	$ 845	$ 820
Average outstanding during the year	1,127.5	682.2	643.5
Maximum outstanding at any month end	$ 1,665	$ 855	$ 820
Average interest rate during the year	2.18%	2.00%	1.11%
Customer repurchase agreements:
Balance at year end	$ 409.1	$ 332.9	$ 301.6
Average outstanding during the year	296.6	252.7	311
Maximum outstanding at any month end	$ 409.1	$ 332.9	$ 331.6
Average interest rate during the year	0.75%	0.40%	0.19%
Other borrowings:
Balance at year end	$ 0	$ 11	$ 207.8
Average outstanding during the year	3.3	104.5	132
Maximum outstanding at any month end	$ 10.4	$ 207.6	$ 237.4
Average interest rate during the year	1.87%	1.66%	1.60%
Securities Sold under Agreements to Repurchase [Member]
Customer repurchase agreements:
Carrying amount of collateral securities at year end	$ 418	$ 342.3	$ 307.7

Notes and Debentures - Schedule

Notes and Debentures - Schedule of Subordinated Borrowing (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Subordinated Borrowing [Line Items]
Total notes and debentures	$ 993.1	$ 895.8
People's United Financial, Inc. [Member]
Subordinated Borrowing [Line Items]
Total notes and debentures	579.9	497.7
People's United Financial, Inc. [Member] | 3.65% Senior Notes Due 2022 [Member]
Subordinated Borrowing [Line Items]
Senior notes	498.3	497.7
People's United Financial, Inc. [Member] | 5.75% Subordinated Notes Due 2024 [Member]
Subordinated Borrowing [Line Items]
Subordinated notes	81.6	0
People's United Bank [Member] | 4.00% Subordinated Notes Due 2024 [Member]
Subordinated Borrowing [Line Items]
Subordinated notes	$ 413.2	$ 398.1

Notes and Debentures - Addition

Notes and Debentures - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2019
Subordinated Borrowing [Line Items]
Debt instrument, maturity date	Apr. 16, 2024
4.00% Subordinated Notes Due 2024 [Member]
Subordinated Borrowing [Line Items]
Interest rate on debt	4.00%
People's United Financial, Inc. [Member] | 3.65% Senior Notes Due 2022 [Member]
Subordinated Borrowing [Line Items]
Debt instrument interest rate	3.65%
Debt instrument call option date	Sep. 6, 2022
Percentage of redemption price to principal amount	100.00%
People's United Financial, Inc. [Member] | 5.75% Subordinated Notes Due 2024 [Member]
Subordinated Borrowing [Line Items]
Interest rate on debt	5.75%
People's United Bank [Member] | 4.00% Subordinated Notes Due 2024 [Member]
Subordinated Borrowing [Line Items]
Percentage of redemption price to principal amount	100.00%
Number of days excluded for redemption of principal amount on occurrence of a regulatory event	90 days

Income Taxes - Summary of Total

Income Taxes - Summary of Total Income Tax Expense (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income tax expense applicable to pre-tax income	$ 36.4	$ 30.4	$ 35.2	$ 30	$ 15.8	$ 32.2	$ 30.8	$ 29.4	$ 132	$ 108.2	$ 129.9
Deferred income tax (benefit) expense applicable to items reported in total other comprehensive income (loss)									27.2	(12.2)	8.3
Total									$ 159.2	$ 96	$ 138.2

Income Taxes - Income Tax Effec

Income Taxes - Income Tax Effects Related to Items Recognized in Other Comprehensive Income (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Federal									$ 90.8	$ 83	$ 88.9
State									26.9	23.3	15.2
Total current tax expense									117.7	106.3	104.1
Deferred tax expense									14.3	1.9	25.8
Total income tax expense	$ 36.4	$ 30.4	$ 35.2	$ 30	$ 15.8	$ 32.2	$ 30.8	$ 29.4	132	108.2	129.9
Increase (decrease) in valuation allowance for state deferred tax assets									$ (7.7)	$ 0.3	$ (0.6)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) $ in Millions	1 Months Ended	3 Months Ended									12 Months Ended
	Feb. 28, 2018USD ($)	Dec. 31, 2019USD ($)	Sep. 30, 2019USD ($)	Jun. 30, 2019USD ($)	Mar. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Sep. 30, 2018USD ($)	Jun. 30, 2018USD ($)	Mar. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Nov. 01, 2019fundsmobileSolarUnit
Schedule Of Income Tax Expense [Line Items]
Income tax benefit										$ (6.5)
Deferred tax assets										58
Deferred tax liabilities										$ 64.5
Income tax expense (benefit)		$ 36.4	$ 30.4	$ 35.2	$ 30	$ 15.8	$ 32.2	$ 30.8	$ 29.4		$ 132	$ 108.2	$ 129.9
Employer contributions	$ 50
Affordable housing investments		383.9				304.1					383.9	304.1
Future contingent commitments		141.1				119.7					$ 141.1	119.7
Amortization period											10 years
Income tax expense											$ 25	19.1	16.7
Number of tax advantage funds | funds														3
Number of mobile solar generators to be acquired under limited liability company | mobileSolarUnit														500
Connecticut tax net operating loss carryforwards		1,200									1,200
Current income tax receivable		51.7				31.4					51.7	31.4
Accrued interest expense related to the unrecognized income tax benefits		$ 0.1				0.9					0.1	0.9
Pension Plans [Member]
Schedule Of Income Tax Expense [Line Items]
Income tax expense (benefit)						$ (9.2)
Employer contributions											18.7	52.7
People's United Financial, Inc. [Member]
Schedule Of Income Tax Expense [Line Items]
Income tax expense (benefit)											(6.2)	(5.5)	(5.7)
People's United Financial, Inc. [Member] | D.C. Solar investment [Member]
Schedule Of Income Tax Expense [Line Items]
Write down of investment											8.4
Additions related to D.C. Solar											$ 18.9	$ 0	$ 0

Income Taxes - Summary of Incom

Income Taxes - Summary of Income Tax Reconciliation (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Amount
Expected income tax expense									$ 137	$ 121	$ 163.5
State income tax, net of federal tax effect									22.6	23.2	12.2
Non-deductible FDIC insurance premiums									4.4	6.5	0
Tax-exempt interest									(21.4)	(19.4)	(26.6)
Federal income tax credits									(12.7)	(12.3)	(11.6)
Tax-exempt income from BOLI									(2.2)	(1.5)	(2.2)
The Tax Cuts and Jobs Act									0	(9.2)	(6.5)
Equity-based compensation									(0.1)	(1.3)	(1.1)
Other, net									4.4	1.2	2.2
Total income tax expense	$ 36.4	$ 30.4	$ 35.2	$ 30	$ 15.8	$ 32.2	$ 30.8	$ 29.4	$ 132	$ 108.2	$ 129.9
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Expected income tax expense									21.00%	21.00%	35.00%
State income tax, net of federal tax effect									3.40%	4.10%	2.60%
Non-deductible FDIC insurance premiums									0.70%	1.10%	0.00%
Tax-exempt interest									(3.30%)	(3.40%)	(5.70%)
Federal income tax credits									(2.00%)	(2.10%)	(2.50%)
Tax-exempt income from BOLI									(0.30%)	(0.30%)	(0.50%)
The Tax Cuts and Jobs Act									0.00%	(1.60%)	(1.40%)
Equity-based compensation									0.00%	(0.20%)	(0.20%)
Other, net									0.70%	0.20%	0.50%
Effective income tax rate									20.20%	18.80%	27.80%

Income Taxes - Deferred Tax Ass

Income Taxes - Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
State tax net operating loss carryforwards, net of federal tax effect	$ 71.8	$ 79.4
Allowance for loan losses and non-accrual interest	65.5	62.3
Acquisition-related deferred tax assets	30.5	13.3
Tax credits and net operating loss carryforwards	24.7	0
Equity-based compensation	18.1	15.6
ROU lease assets, net of lease liabilities	7.5
D.C. Solar investment basis difference	6.8	0
Unrealized loss on debt securities transferred to held-to-maturity	3.6	4.7
Unrealized loss on debt securities available-for-sale	0	15.4
Other deductible temporary differences	28.2	28.5
Total deferred tax assets	256.7	219.2
Less: valuation allowance for state deferred tax assets	(72.4)	(80.1)
Total deferred tax assets, net of the valuation allowance	184.3	139.1
Deferred tax liabilities:
Leasing activities	(92.7)	(82)
Pension and other postretirement benefits	(20)	(9.7)
Book over tax income recognized on consumer loans	(18)	(17.5)
Unrealized gain on debt securities available-for-sale	(6.6)	0
Mark-to-market and original issue discounts for tax purposes	(5.2)	(10.4)
Temporary differences related to merchant services joint venture	(3.5)	(3.7)
Other taxable temporary differences	(4.7)	(4.4)
Total deferred tax liabilities	(150.7)	(127.7)
Net deferred tax asset	$ 33.6	$ 11.4

Income Taxes - Unrecognized Inc

Income Taxes - Unrecognized Income Tax Benefits (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of year	$ 5.2	$ 2.7	$ 2.8
Additions for tax positions taken in prior years	0.5	2.5	0.1
Reductions attributable to audit settlements/lapse of statute of limitations	0	0	(0.2)
Balance at end of year	33.3	5.2	2.7
United Financial [Member] | D.C. Solar investment [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Additions related to D.C. Solar	8.7	0	0
People's United Financial, Inc. [Member] | D.C. Solar investment [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Additions related to D.C. Solar	$ 18.9	$ 0	$ 0

Stockholders' Equity and Divi_2

Stockholders' Equity and Dividends - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								7 Months Ended	12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Apr. 30, 2007
Schedule Of Stockholders Equity [Line Items]
Preferred stock, shares authorized (in shares)	50,000,000				50,000,000				50,000,000	50,000,000	50,000,000
Preferred stock, par value (in dollars per share)	$ 0.01				$ 0.01				$ 0.01	$ 0.01	$ 0.01
Preferred stock, shares outstanding (in shares)	10,000,000				10,000,000				10,000,000	10,000,000	10,000,000
Common stock, shares authorized (in shares)	1,950,000,000				1,950,000,000				1,950,000,000	1,950,000,000	1,950,000,000
Common stock, par value (in dollars per share)	$ 0.01				$ 0.01				$ 0.01	$ 0.01	$ 0.01
Common stock, shares issued (in shares)	532,800,000				466,300,000				532,800,000	532,800,000	466,300,000
Number of common stock purchased (in shares)	89,200,000				89,000,000				89,200,000	89,200,000	89,000,000
Shares authorized to be repurchased (in shares)			20,000,000
Treasury stock shares acquired (in shares)									200,000
Treasury stock acquired									$ 2.5	$ 2.5
Original loan amount ESOP													$ 216.8
ESOP shares purchased in open market													10,500,000
Unallocated common stock of Employee Stock Ownership Plan (in shares)	5,923,692				6,300,000				5,923,692	5,923,692	6,300,000
Unallocated common stock of employee stock ownership plan	$ 122.9				$ 130.1				$ 122.9	$ 122.9	$ 130.1
Cash dividends on common stock (in dollars per share)										$ 0.7075	$ 0.6975	$ 0.6875
Dividend payout ratio	52.20%	53.10%	53.80%	58.60%	50.30%	52.90%	56.20%	56.30%		54.30%	53.70%	70.60%
Repurchases Authorized by Board of Directors [Member]
Schedule Of Stockholders Equity [Line Items]
Number of common stock purchased (in shares)	86,600,000								86,600,000	86,600,000
2007 Recognition and Retention Plan [Member]
Schedule Of Stockholders Equity [Line Items]
Number of common stock purchased (in shares)	2,600,000								2,600,000	2,600,000
People's United Financial, Inc. [Member]
Schedule Of Stockholders Equity [Line Items]
Preferred stock, shares authorized (in shares)	50,000,000								50,000,000	50,000,000
Preferred stock, par value (in dollars per share)	$ 0.01								$ 0.01	$ 0.01
Preferred stock, shares outstanding (in shares)	10,000,000								10,000,000	10,000,000
Common stock, shares authorized (in shares)	1,950,000,000								1,950,000,000	1,950,000,000
Common stock, par value (in dollars per share)	$ 0.01								$ 0.01	$ 0.01
Common stock, shares issued (in shares)	532,800,000								532,800,000	532,800,000
Cash dividends payable to parent company										$ 457	$ 342	$ 292
People's United Bank [Member]
Schedule Of Stockholders Equity [Line Items]
Retained net income under federal regulations										$ 233.3
2014 Long-Term Incentive Plan [Member] | 2007 Recognition and Retention Plan [Member]
Schedule Of Stockholders Equity [Line Items]
Additional awards under RRP	0								0	0

Regulatory Capital Requiremen_3

Regulatory Capital Requirements - Additional Information (Detail) - USD ($)	Jan. 01, 2019	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2020
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common equity tier 1 capital, Ratio, Minimum capital adequacy		4.50%
Capital conservation buffer		2.50%
Common Equity Tier 1 Capital, Ratio, Minimum Capital Adequacy including conservation buffer		7.00%
Risk-based capital tier 1, Ratio, Minimum capital adequacy		6.00%
Common Tier 1 buffer phase start year		2016
Risk-based capital tier 1, Ratio, Minimum capital adequacy including conservation buffer		8.50%
Total, Ratio, Minimum capital adequacy		8.00%
Total, Ratio, Minimum capital adequacy including conservation buffer		10.50%
Leverage (core) capital, Ratio		4.00%
Capital conservation buffer		2.50%	1.875%
Operating lease		$ 307,900,000
Lease ROU assets		$ 276,600,000
Accounting Standards Update 2016-02 [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Operating lease	$ 268,800,000
Lease ROU assets	$ 248,500,000
Increase (decrease) in risk-based capital ratios	(0.10%)
Minimum [Member] | Accounting Standards Update 2016-02 [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Increase (decrease) in risk-based capital ratios	(0.05%)
Minimum [Member] | Accounting Standards Update 2016-02 [Member] | Subsequent Event [Member] | Scenario, Forecast [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Decrease in risk-based capital ratios				(0.10%)
Maximum [Member] | Accounting Standards Update 2016-02 [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Increase (decrease) in risk-based capital ratios	(0.10%)
People's United Financial, Inc. [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common equity tier 1 capital, Ratio, Minimum capital adequacy		7.00%	6.375%
Risk-based capital tier 1, Ratio, Minimum capital adequacy		8.50%	7.875%
Total, Ratio, Minimum capital adequacy		12.00%	12.50%
Leverage (core) capital, Ratio		9.10%	8.70%
Risk-weighted assets		$ 45,200,000,000	$ 35,900,000,000
People's United Financial, Inc. [Member] | 4.00% Subordinated Notes Due 2024 [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Reduction period		4 years
Senior notes issuance		$ 75,000,000
Reduction percentage		20.00%
Reduction amount		$ 15,000,000
Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common equity tier 1 capital, Ratio, Minimum capital adequacy		7.00%	6.375%
Risk-based capital tier 1, Ratio, Minimum capital adequacy		8.50%	7.875%
Total, Ratio, Minimum capital adequacy		12.10%	13.20%
Leverage (core) capital, Ratio		9.30%	9.00%
Bank [Member] | 4.00% Subordinated Notes Due 2024 [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Senior notes issuance		$ 400,000,000
Reduction percentage		20.00%
Reduction amount		$ 80,000,000

Regulatory Capital Requiremen_4

Regulatory Capital Requirements - Regulatory Capital Requirements and Ratio under Basel III Capital Rules (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 Leverage Capital, Ratio	4.00%
Total, Ratio	8.00%
CET 1 Risk-Based Capital, Ratio, Minimum Capital Required	4.50%
Tier 1 Risk-Based Capital, Ratio, Minimum Capital Required	6.00%
Total Risk-Weighted Assets for allowance for loan losses	1.25%
People's United Financial, Inc. [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 Leverage Capital, Amount	$ 4,846.1	$ 3,927.2
CET 1 Risk-Based Capital, Amount	4,602.1	3,683.1
Tier 1 Risk-Based Capital	4,846.1	3,927.2
Total, Amount	$ 5,435.6	$ 4,505.7
Tier 1 Leverage Capital, Ratio	9.10%	8.70%
CET 1 Risk-Based Capital, Ratio	10.20%	10.30%
Tier 1 Risk-Based Capital, Ratio	10.70%	10.90%
Total, Ratio	12.00%	12.50%
Tier 1 Leverage Capital, Minimum Capital Required, Amount	$ 2,119.7	$ 1,806
CET 1 Risk-Based Capital, Minimum Capital Required, Amount	3,164.5	2,289.3
Tier 1 Risk-Based Capital, Minimum Capital Required, Amount	3,842.6	2,827.9
Total, Minimum Capital Required, Amount	$ 4,746.8	$ 3,546.1
Tier 1 Leverage Capital, Ratio, Minimum Capital Required	4.00%	4.00%
CET 1 Risk-Based Capital, Ratio, Minimum Capital Required	7.00%	6.375%
Tier 1 Risk-Based Capital, Ratio, Minimum Capital Required	8.50%	7.875%
Total, Ratio, Minimum Capital Required	10.50%	9.875%
Tier 1 Risk-Based Capital, Well-Capitalized, Amount	$ 2,712.5	$ 2,154.6
Total, Well-Capitalized, Amount	$ 4,520.8	$ 3,591
Tier 1 Risk-Based Capital, Ratio, Well-Capitalized	6.00%	6.00%
Total, Ratio, Well-Capitalized	10.00%	10.00%
Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 Leverage Capital, Amount	$ 4,902	$ 4,076
CET 1 Risk-Based Capital, Amount	4,902	4,076
Tier 1 Risk-Based Capital	4,902	4,076
Total, Amount	$ 5,474.2	$ 4,719.1
Tier 1 Leverage Capital, Ratio	9.30%	9.00%
CET 1 Risk-Based Capital, Ratio	10.90%	11.40%
Tier 1 Risk-Based Capital, Ratio	10.90%	11.40%
Total, Ratio	12.10%	13.20%
Tier 1 Leverage Capital, Minimum Capital Required, Amount	$ 2,119.1	$ 1,805.4
CET 1 Risk-Based Capital, Minimum Capital Required, Amount	3,162.2	2,287.1
Tier 1 Risk-Based Capital, Minimum Capital Required, Amount	3,839.8	2,825.2
Total, Minimum Capital Required, Amount	$ 4,743.3	$ 3,542.7
Tier 1 Leverage Capital, Ratio, Minimum Capital Required	4.00%	4.00%
CET 1 Risk-Based Capital, Ratio, Minimum Capital Required	7.00%	6.375%
Tier 1 Risk-Based Capital, Ratio, Minimum Capital Required	8.50%	7.875%
Total, Ratio, Minimum Capital Required	10.50%	9.875%
Tier 1 Leverage Capital, Well-Capitalized, Amount	$ 2,648.8	$ 2,256.8
CET 1 Risk-Based Capital, Well-Capitalized, Amount	2,936.3	2,331.9
Tier 1 Risk-Based Capital, Well-Capitalized, Amount	3,614	2,870
Total, Well-Capitalized, Amount	$ 4,517.4	$ 3,587.5
Tier 1 Leverage Capital, Ratio , Well-Capitalized	5.00%	5.00%
CET 1 Risk-Based Capital, Ratio, Well-Capitalized	6.50%	6.50%
Tier 1 Risk-Based Capital, Ratio, Well-Capitalized	8.00%	8.00%
Total, Ratio, Well-Capitalized	10.00%	10.00%

Earnings Per Common Share - Bas

Earnings Per Common Share - Basic and Diluted Earnings Per Common Share, Reflecting Application of Two-Class Method (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share [Abstract]
Net income available to common shareholders	$ 134	$ 131.6	$ 129.7	$ 111.1	$ 129.4	$ 113.5	$ 106.7	$ 104.4	$ 506.3	$ 454	$ 323.1
Dividends paid on and undistributed earnings allocated to participating securities									(0.2)	(0.2)	(0.5)
Earnings attributable to common shareholders									$ 506.1	$ 453.8	$ 322.6
Weighted average common shares outstanding for basic EPS (in shares)	421,850	391,660	391,270	370,720	370,220	341,430	340,640	339,760	394,000	348,100	330,300
Effect of dilutive equity-based awards (in shares)									3,200	3,600	2,600
Weighted average common shares and common-equivalent shares for diluted EPS (in shares)	424,980	394,450	394,570	374,090	372,830	345,040	344,470	344,000	397,200	351,700	332,900
EPS:
Basic (in dollars per share)	$ 0.31	$ 0.34	$ 0.33	$ 0.30	$ 0.35	$ 0.33	$ 0.31	$ 0.31	$ 1.28	$ 1.30	$ 0.98
Diluted (in dollars per share)	$ 0.31	$ 0.33	$ 0.33	$ 0.30	$ 0.35	$ 0.33	$ 0.31	$ 0.30	$ 1.27	$ 1.29	$ 0.97

Earnings Per Common Share - Add

Earnings Per Common Share - Additional Information (Detail) - shares shares in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share [Abstract]
Anti-dilutive equity-based awards excluded from calculation of diluted EPS (in shares)	6.7	6.8	8.9

Comprehensive Income - Schedule

Comprehensive Income - Schedule of Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	$ 6,533.9	$ 5,819.9	$ 5,141.9
Other comprehensive income (loss) before reclassifications	79.1	(55)	(8.7)
Amounts reclassified from AOCL	10.8	17.2	22
Total other comprehensive income (loss), net of tax	89.9	(37.8)	13.3
Transition adjustments related to adoption of new accounting standards				$ 0.6
Ending Balance	7,947.2	6,533.9	5,819.9
Accumulated Other Comprehensive Loss [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(256.8)	(181.7)	(195)
Total other comprehensive income (loss), net of tax	89.9	(37.8)	13.3
Transition adjustments related to adoption of new accounting standards				(37.3)
Ending Balance	(166.9)	(256.8)	(181.7)
Pension and Other Postretirement Plans [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(192.5)	(144.1)	(145.6)
Other comprehensive income (loss) before reclassifications	9.7	(24.7)	(2.8)
Amounts reclassified from AOCL	6.6	6.3	4.3
Total other comprehensive income (loss), net of tax	16.3	(18.4)	1.5
Transition adjustments related to adoption of new accounting standards				(30)
Ending Balance	(176.2)	(192.5)	(144.1)
Net Unrealized Gains (Losses) on Debt Securities Available for Sale [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(47)	(21.6)	(32.3)
Other comprehensive income (loss) before reclassifications	67.9	(29)	(5.3)
Amounts reclassified from AOCL	(0.1)	7.5	16
Total other comprehensive income (loss), net of tax	67.8	(21.5)	10.7
Transition adjustments related to adoption of new accounting standards				(3.9)
Ending Balance	20.8	(47)	(21.6)
Net Unrealized Gain (Losses) On Debt Securities Transferred To Held To Maturity [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(15.3)	(15.1)	(17.4)
Other comprehensive income (loss) before reclassifications	0	0	0
Amounts reclassified from AOCL	3.5	3	2.3
Total other comprehensive income (loss), net of tax	3.5	3	2.3
Transition adjustments related to adoption of new accounting standards				(3.2)
Ending Balance	(11.8)	(15.3)	(15.1)
Net Unrealized Gains (Losses) on Derivatives Accounted for as Cash Flow Hedges [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(2)	(0.9)	0.3
Other comprehensive income (loss) before reclassifications		(1.3)	(0.6)
Amounts reclassified from AOCL		0.4	(0.6)
Total other comprehensive income (loss), net of tax		(0.9)	(1.2)
Transition adjustments related to adoption of new accounting standards				$ (0.2)
Ending Balance		$ (2)	$ (0.9)
Net Unrealized Gains (Losses) on Derivatives Accounted for as Cash Flow Hedges [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive income (loss) before reclassifications	1.5
Amounts reclassified from AOCL	0.8
Total other comprehensive income (loss), net of tax	2.3
Ending Balance	$ 0.3

Comprehensive Income - Summary

Comprehensive Income - Summary of Amounts Reclassified from AOCL (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other non-interest income									$ 85.9	$ 50.9	$ 62.6
Interest and dividend income - securities									(34.9)	(33.3)	(29.9)
Income before income tax expense	$ 173.9	$ 165.5	$ 168.4	$ 144.6	$ 148.7	$ 149.2	$ 141	$ 137.3	652.4	576.3	467.1
Income tax expense	(36.4)	(30.4)	(35.2)	(30)	(15.8)	(32.2)	(30.8)	(29.4)	(132)	(108.2)	(129.9)
Net income	$ 137.5	$ 135.1	$ 133.2	$ 114.6	$ 132.9	$ 117	$ 110.2	$ 107.9	520.4	468.1	337.2
Total reclassifications for the period									10.8	17.2	22
Pension and Other Postretirement Plans [Member] | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income before income tax expense									(8.3)	(8.3)	(8.5)
Income tax expense									1.7	2	4.2
Net income									(6.6)	(6.3)	(4.3)
Net Actuarial Loss [Member] | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other non-interest income									(8.3)	(8.6)	(9.3)
Prior Service Credit [Member] | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other non-interest income									0	0.3	0.8
Net Unrealized Gains (Losses) on Debt Securities Available for Sale [Member] | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income before income tax expense									0.1	(9.9)	(25.4)
Income tax expense									0	2.4	9.4
Net income									0.1	(7.5)	(16)
Net Unrealized Gain (Losses) On Debt Securities Transferred To Held To Maturity [Member] | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income before income tax expense									(4.6)	(3.9)	(3.7)
Income tax expense									1.1	0.9	1.4
Net income									(3.5)	(3)	(2.3)
Net Unrealized Gains (Losses) on Derivatives Accounted for as Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income before income tax expense									(1.1)
Income tax expense									0.3
Net income									(0.8)
Net Unrealized Gains (Losses) on Derivatives Accounted for as Cash Flow Hedges [Member] | Interest Rate Swaps [Member] | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest and dividend income - securities									(1.2)
Net Unrealized Gains (Losses) on Derivatives Accounted for as Cash Flow Hedges [Member] | Interest Rate Locks [Member] | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest and dividend income - securities									$ 0.1
Net Unrealized Gains (Losses) on Derivatives Accounted for as Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income before income tax expense										(0.5)	0.9
Income tax expense										0.1	(0.3)
Net income										(0.4)	0.6
Net Unrealized Gains (Losses) on Derivatives Accounted for as Cash Flow Hedges [Member] | Interest Rate Swaps [Member] | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest and dividend income - securities										(0.6)	0.8
Net Unrealized Gains (Losses) on Derivatives Accounted for as Cash Flow Hedges [Member] | Interest Rate Locks [Member] | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest and dividend income - securities										$ 0.1	$ 0.1

Comprehensive Income - Deferred

Comprehensive Income - Deferred Income Taxes Applicable to Components of Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI Tax, Attributable to Parent	$ 52.2	$ 79.4	$ 105.5
Pension and Other Postretirement Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI Tax, Attributable to Parent	55.3	59.4	83.5
Net Unrealized Gains (Losses) on Debt Securities Available for Sale [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI Tax, Attributable to Parent	(6.6)	14.7	12.7
Net Unrealized Gain (Losses) On Debt Securities Transferred To Held To Maturity [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI Tax, Attributable to Parent	3.6	4.7	8.8
Net Unrealized Gains (Losses) on Derivatives Accounted for as Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI Tax, Attributable to Parent	$ (0.1)
Net Unrealized Gains (Losses) on Derivatives Accounted for as Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI Tax, Attributable to Parent		$ 0.6	$ 0.5

Comprehensive Income - Other Co

Comprehensive Income - Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
OCI, before reclassifications, after tax amount	$ 79.1	$ (55)	$ (8.7)
Reclassification adjustment, after-tax amount	10.8	17.2	22
Other comprehensive income (loss), pre-tax amount	117.1	(50)	21.6
Other comprehensive income (loss), tax effect	(27.2)	12.2	(8.3)
Total other comprehensive income (loss), net of tax	89.9	(37.8)	13.3
Pension and Other Postretirement Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
OCI, before reclassifications, pre-tax amount	12.1
OCI, before reclassification, tax effect	(2.4)
OCI, before reclassifications, after tax amount	9.7	(24.7)	(2.8)
Reclassification adjustment, pre-tax amount	8.3
Reclassification adjustment, tax effect	(1.7)
Reclassification adjustment, after-tax amount	6.6	6.3	4.3
Other comprehensive income (loss), pre-tax amount	20.4	(24.3)	3
Other comprehensive income (loss), tax effect	(4.1)	5.9	(1.5)
Total other comprehensive income (loss), net of tax	16.3	(18.4)	1.5
Net Actuarial Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
OCI, before reclassifications, pre-tax amount		(32.6)	(5.5)
OCI, before reclassification, tax effect		7.9	2.7
OCI, before reclassifications, after tax amount		(24.7)	(2.8)
Reclassification adjustment, pre-tax amount		8.6	9.3
Reclassification adjustment, tax effect		(2.1)	(4.6)
Reclassification adjustment, after-tax amount		6.5	4.7
Other comprehensive income (loss), pre-tax amount		(24)	3.8
Other comprehensive income (loss), tax effect		5.8	(1.9)
Total other comprehensive income (loss), net of tax		(18.2)	1.9
Prior Service Credit [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification adjustment, pre-tax amount		(0.3)	(0.8)
Reclassification adjustment, tax effect		0.1	0.4
Reclassification adjustment, after-tax amount		(0.2)	(0.4)
Net Unrealized Gains (Losses) on Debt Securities Available for Sale [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
OCI, before reclassifications, pre-tax amount	89.2	(38.3)	(8.6)
OCI, before reclassification, tax effect	(21.3)	9.3	3.3
OCI, before reclassifications, after tax amount	67.9	(29)	(5.3)
Reclassification adjustment, pre-tax amount	(0.1)	9.9	25.4
Reclassification adjustment, tax effect	0	(2.4)	(9.4)
Reclassification adjustment, after-tax amount	(0.1)	7.5	16
Other comprehensive income (loss), pre-tax amount	89.1	(28.4)	16.8
Other comprehensive income (loss), tax effect	(21.3)	6.9	(6.1)
Total other comprehensive income (loss), net of tax	67.8	(21.5)	10.7
Net Unrealized Gain (Losses) On Debt Securities Transferred To Held To Maturity [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
OCI, before reclassifications, after tax amount	0	0	0
Reclassification adjustment, pre-tax amount	4.6	3.9	3.7
Reclassification adjustment, tax effect	(1.1)	(0.9)	(1.4)
Reclassification adjustment, after-tax amount	3.5	3	2.3
Other comprehensive income (loss), pre-tax amount	4.6	3.9	3.7
Other comprehensive income (loss), tax effect	(1.1)	(0.9)	(1.4)
Total other comprehensive income (loss), net of tax	3.5	3	2.3
Net Unrealized Gains (Losses) on Derivatives Accounted for as Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
OCI, before reclassifications, pre-tax amount	1.9
OCI, before reclassification, tax effect	(0.4)
OCI, before reclassifications, after tax amount	1.5
Reclassification adjustment, pre-tax amount	1.1
Reclassification adjustment, tax effect	(0.3)
Reclassification adjustment, after-tax amount	0.8
Other comprehensive income (loss), pre-tax amount	3
Other comprehensive income (loss), tax effect	(0.7)
Total other comprehensive income (loss), net of tax	$ 2.3
Net Unrealized Gains (Losses) on Derivatives Accounted for as Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
OCI, before reclassifications, pre-tax amount		(1.7)	(1)
OCI, before reclassification, tax effect		0.4	0.4
OCI, before reclassifications, after tax amount		(1.3)	(0.6)
Reclassification adjustment, pre-tax amount		0.5	(0.9)
Reclassification adjustment, tax effect		(0.1)	0.3
Reclassification adjustment, after-tax amount		0.4	(0.6)
Other comprehensive income (loss), pre-tax amount		(1.2)	(1.9)
Other comprehensive income (loss), tax effect		0.3	0.7
Total other comprehensive income (loss), net of tax		$ (0.9)	$ (1.2)

Employee Benefit Plans - People

Employee Benefit Plans - People's United Employee Pension and Other Postretirement Plans - Additional Information (Detail) - USD ($)	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Feb. 28, 2018
Defined Benefit Plan Disclosure [Line Items]
Average compensation term on which pension plan benefits are based, in years			5 years
Average compensation term within last ten years on which pension plan benefits are based, in years			5 years
Term considered when determining employee pension benefits, in years			10 years
Trust assets	$ 56,400,000		$ 51,000,000	$ 56,400,000
Maximum percentage of fixed income holdings invested in issues rated below Baa			30.00%
Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of covered employee's eligible compensation			4.00%
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	596,400,000		$ 746,700,000	596,400,000	$ 584,900,000
Projected benefit obligations:	562,700,000		665,500,000	562,700,000	$ 584,800,000
Defined benefit plan, expected future benefit payments in year one			28,500,000
Defined benefit plan, expected future benefit payments in year two			30,000,000
Defined benefit plan, expected future benefit payments in year three			30,600,000
Defined benefit plan, expected future benefit payments in year four			31,200,000
Defined benefit plan, expected future benefit payments in year five			33,000,000
Defined benefit plan, expected future benefit payments after five years			181,200,000
Pension Plans [Member] | Nonqualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligations:	44,000,000		40,200,000	44,000,000
Trust assets			33,100,000
Pension Plans [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	596,400,000		746,700,000	596,400,000
Projected benefit obligations:	$ 518,700,000		625,300,000	$ 518,700,000
Net periodic benefit income			$ 22,300,000
Percentage of equity holdings invested in international equities			50.00%
Maximum percentage of fixed income holdings invested in issues rated below Baa			2.50%
Market value of total plan assets			2.50%
Maximum percentage of any individual security			3.00%
Pension Plans [Member] | Qualified Plan [Member] | People's Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of covered employee's eligible compensation			3.00%
Minimum age requirement to participate in pension plan, years			18 years
Minimum service hours per year requirement to participate in pension plan			1000 hours
Pension plan assets measured at fair value			$ 687,800,000
Projected benefit obligations:			$ 569,100,000
Amortization of unrecognized gain loss over average remaining life of plan participants			26 years
Discount rate used to determine benefit obligation	4.41%		3.38%	4.41%	3.74%
Discount rate used to calculate net periodic benefit cost	4.34%	3.74%	4.41%		4.41%
Expected long-term rate of return assumption			7.25%	7.25%	7.25%
Expected long-term rate of return assumption			7.25%
Discount rate			3.38%
Expected employer contributions						$ 40,000,000
Pension Plans [Member] | Qualified Plan [Member] | United Financial Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value			$ 34,000,000
Projected benefit obligations:			$ 31,900,000
Amortization of unrecognized gain loss over average remaining life of plan participants			30 years
Discount rate used to determine benefit obligation			3.42%
Discount rate used to calculate net periodic benefit cost			3.33%
Expected long-term rate of return assumption			5.25%
Discount rate			3.42%
Pension Plans [Member] | Qualified Plan [Member] | First Connecticut Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value			$ 24,900,000
Projected benefit obligations:			$ 24,300,000
Amortization of unrecognized gain loss over average remaining life of plan participants			28 years
Discount rate used to determine benefit obligation	4.41%		3.39%	4.41%
Discount rate used to calculate net periodic benefit cost			4.41%	4.35%
Expected long-term rate of return assumption			6.00%	6.00%
Expected long-term rate of return assumption			7.25%
Discount rate			3.39%
Pension Plans [Member] | Qualified Plan [Member] | Chittenden Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate used to determine benefit obligation					3.62%
Discount rate used to calculate net periodic benefit cost					4.16%
Expected employer contributions						10,000,000
Pension Plans [Member] | Qualified Plan [Member] | Suffolk Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate used to determine benefit obligation					3.72%
Discount rate used to calculate net periodic benefit cost					4.24%
Expected employer contributions						$ 0
Pension Plans [Member] | Minimum [Member] | Nonqualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate used to determine benefit obligation	4.00%		2.76%	4.00%
Discount rate used to calculate net periodic benefit cost			3.33%	3.32%
Pension Plans [Member] | Minimum [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated unrecognized gain or loss percentage for amortization of actuarial gain loss			10.00%
Pension Plans [Member] | Maximum [Member] | Nonqualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate used to determine benefit obligation	4.40%		3.40%	4.40%
Discount rate used to calculate net periodic benefit cost			4.40%	4.30%
Other Pension Plan, Postretirement or Supplemental Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected employer contributions			$ 4,900,000
Other Postretirement Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	$ 0		0	$ 0	$ 0
Projected benefit obligations:	$ 15,300,000		18,700,000	$ 15,300,000	$ 14,600,000
Defined benefit plan, expected future benefit payments in year one			1,100,000
Defined benefit plan, expected future benefit payments in year two			1,100,000
Defined benefit plan, expected future benefit payments in year three			1,100,000
Defined benefit plan, expected future benefit payments in year four			1,100,000
Defined benefit plan, expected future benefit payments in year five			1,000,000
Defined benefit plan, expected future benefit payments after five years			$ 4,700,000
Other Postretirement Plans [Member] | People's Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate used to determine benefit obligation	4.40%		3.40%	4.40%	3.70%
Discount rate used to calculate net periodic benefit cost			4.40%	3.70%	4.40%

Employee Benefit Plans - Change

Employee Benefit Plans - Changes in Benefit Obligations and Plan Assets (Detail) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Feb. 28, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fair value of plan assets:
Employer contributions	$ 50
Pension Plans [Member]
Benefit Obligation
Beginning of year		$ 562.7	$ 584.8
Service cost		0	0
Interest cost		22.9	20.2	$ 19.1
Actuarial loss (gain)		80.2	(51)
Benefits paid		(28.2)	(21.4)
Settlements		(13.1)	(2.7)
Acquisitions		41	35.2
Plan revaluations		0	(2.4)
End of year		665.5	562.7	584.8
Fair value of plan assets:
Beginning of year		596.4	584.9
Actual return on assets		138.6	(40.9)
Employer contributions		18.7	52.7
Benefits paid		(28.2)	(21.4)
Settlements		(13.1)	(2.7)
Acquisitions		34.3	23.8
End of year		746.7	596.4	584.9
Funded status at end of year		81.2	33.7
Amounts recognized in the Consolidated Statements of Condition:
Other assets		121.4	78
Other liabilities		(40.2)	(44.3)
Funded status at end of year		81.2	33.7
Other Postretirement Plans [Member]
Benefit Obligation
Beginning of year		15.3	14.6
Service cost		0.3	0.3
Interest cost		0.6	0.5
Actuarial loss (gain)		1.2	(1.7)
Benefits paid		(0.7)	(0.8)
Settlements		0	0
Acquisitions		2	2.4
Plan revaluations		0	0
End of year		18.7	15.3	14.6
Fair value of plan assets:
Beginning of year		0	0
Actual return on assets		0	0
Employer contributions		0.7	0.8
Benefits paid		(0.7)	(0.8)
Settlements		0	0
Acquisitions		0	0
End of year		0	0	$ 0
Funded status at end of year		(18.7)	(15.3)
Amounts recognized in the Consolidated Statements of Condition:
Other assets		0	0
Other liabilities		(18.7)	(15.3)
Funded status at end of year		$ (18.7)	$ (15.3)

Employee Benefit Plans - Accumu

Employee Benefit Plans - Accumulated and Projected Benefit Obligations (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligations:	$ 84.4	$ 86.6
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligations:	665.3	562.3
Projected benefit obligations:	665.5	562.7	$ 584.8
Pension Plans [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligations:	625.3	518.7
Projected benefit obligations:	625.3	518.7
Pension Plans [Member] | Nonqualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligations:	40	43.6
Projected benefit obligations:	$ 40.2	$ 44

Employee Benefit Plans - Compon

Employee Benefit Plans - Components of Net Periodic Benefit (Income) Expense and Other Amounts (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss) [Abstract]
Net actuarial (gain) loss	$ (12.1)	$ 32.6	$ 5.5
Total pre-tax changes recognized in other comprehensive income (loss)	(20.4)	24.3	(3)
Pension Plans [Member]
Net periodic benefit (income) expense:
Interest cost	22.9	20.2	19.1
Expected return on plan assets	(46.1)	(44.3)	(37.9)
Recognized net actuarial loss	5.3	7.3	6.5
Recognized prior service credit	0	(0.3)	(0.8)
Settlements	2.9	1	2.6
Net periodic benefit (income) expense	(15)	(16.1)	(10.5)
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss) [Abstract]
Net actuarial (gain) loss	(20.5)	26	(4.8)
Prior service credit	0	0.3	0.8
Total pre-tax changes recognized in other comprehensive income (loss)	(20.5)	26.3	(4)
Total recognized in net periodic benefit (income) expense and other comprehensive income (loss)	(35.5)	10.2	(14.5)
Other Postretirement Plans [Member]
Net periodic benefit (income) expense:
Interest cost	0.6	0.5
Expected return on plan assets	0	0	0
Recognized net actuarial loss	0.1	0.3	0.2
Recognized prior service credit	0	0	0
Settlements	0	0	0
Net periodic benefit (income) expense	1	1.1	1
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss) [Abstract]
Net actuarial (gain) loss	1.1	(2)	1
Prior service credit	0	0	0
Total pre-tax changes recognized in other comprehensive income (loss)	1.1	(2)	1
Total recognized in net periodic benefit (income) expense and other comprehensive income (loss)	2.1	(0.9)	2
Interest cost	$ 0.9	$ 0.8	$ 0.8

Employee Benefit Plans - Pre-Ta

Employee Benefit Plans - Pre-Tax Amounts in Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	$ 228.5	$ 249
Total pre-tax amounts included in AOCL	228.5	249
Other Postretirement Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	3.9	2.8
Total pre-tax amounts included in AOCL	$ 3.9	$ 2.8

Employee Benefit Plans - Assump

Employee Benefit Plans - Assumptions Used in Determining Benefit Obligations and Net Periodic Benefit Expense (Detail)	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Assumed health care cost trend rates at December 31:
Health care cost trend rate assumed for next year	6.00%		5.70%	6.00%	6.20%
Rate to which the cost trend rate is assumed to decline (the ultimate trend rate)	4.50%		4.50%	4.50%	4.50%
Year that the rate reaches the ultimate trend rate			2037	2037	2037
Pension Plans [Member] | People's Qualified Plan [Member] | Qualified Plan [Member]
Weighted-average assumptions used to determine benefit obligations at December 31:
Discount rate:	4.41%		3.38%	4.41%	3.74%
Weighted-average assumptions used to determine net periodic benefit (income) expense for the years ended December 31:
Discount rate:	4.34%	3.74%	4.41%		4.41%
Expected return on plan assets			7.25%	7.25%	7.25%
Pension Plans [Member] | First Connecticut Qualified Plan [Member] | Qualified Plan [Member]
Weighted-average assumptions used to determine benefit obligations at December 31:
Discount rate:	4.41%		3.39%	4.41%
Weighted-average assumptions used to determine net periodic benefit (income) expense for the years ended December 31:
Discount rate:			4.41%	4.35%
Expected return on plan assets			6.00%	6.00%
Pension Plans [Member] | United Financial Qualified Plan [Member] | Qualified Plan [Member]
Weighted-average assumptions used to determine benefit obligations at December 31:
Discount rate:			3.42%
Weighted-average assumptions used to determine net periodic benefit (income) expense for the years ended December 31:
Discount rate:			3.33%
Expected return on plan assets			5.25%
Pension Plans [Member] | Chittenden Qualified Plan [Member] | Qualified Plan [Member]
Weighted-average assumptions used to determine benefit obligations at December 31:
Discount rate:					3.62%
Weighted-average assumptions used to determine net periodic benefit (income) expense for the years ended December 31:
Discount rate:					4.16%
Pension Plans [Member] | Suffolk Qualified Plan [Member] | Qualified Plan [Member]
Weighted-average assumptions used to determine benefit obligations at December 31:
Discount rate:					3.72%
Weighted-average assumptions used to determine net periodic benefit (income) expense for the years ended December 31:
Discount rate:					4.24%
Other Postretirement Plans [Member] | People's Qualified Plan [Member]
Weighted-average assumptions used to determine benefit obligations at December 31:
Discount rate:	4.40%		3.40%	4.40%	3.70%
Weighted-average assumptions used to determine net periodic benefit (income) expense for the years ended December 31:
Discount rate:			4.40%	3.70%	4.40%

Employee Benefit Plans - Assets

Employee Benefit Plans - Assets Allocation (Detail) - Pension Plans [Member] - Qualified Plan [Member]	Dec. 31, 2019
Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Policy target percentage	1.00%
Cash Equivalents [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Policy target percentage	0.00%
Cash Equivalents [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Policy target percentage	2000.00%
Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Policy target percentage	65.00%
Equity Securities [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Policy target percentage	5500.00%
Equity Securities [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Policy target percentage	7500.00%
Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Policy target percentage	24.00%
Fixed Income Securities [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Policy target percentage	1000.00%
Fixed Income Securities [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Policy target percentage	4000.00%

Employee Benefit Plans - Fair V

Employee Benefit Plans - Fair Value of Assets in Qualified Plans (Detail) - Pension Plans [Member] - Qualified Plan [Member]	Dec. 31, 2019	Dec. 31, 2018
People's Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	100.00%	100.00%
First Connecticut Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	100.00%	100.00%
United Financial Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	100.00%
Equity Securities [Member] | People's Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	66.00%	70.00%
Equity Securities [Member] | First Connecticut Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	66.00%	73.00%
Equity Securities [Member] | United Financial Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	9.00%
Cash Equivalents and Fixed Income Securities [Member] | People's Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	34.00%	30.00%
Cash Equivalents and Fixed Income Securities [Member] | First Connecticut Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	34.00%	27.00%
Cash Equivalents and Fixed Income Securities [Member] | United Financial Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	91.00%

Employee Benefit Plans - Plan A

Employee Benefit Plans - Plan Assets Measured at Fair Value (Detail) - Pension Plans [Member] - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	$ 746.7	$ 596.4	$ 584.9
Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	746.7	596.4
Cash Equivalents [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	18.9	15.2
Equity Common Stocks [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	261.2	216.6
Equity Mutual Funds [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	215.2	201.1
Corporate [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	73	68.5
Mutual Funds [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	72.5	32.9
U.S. Treasury and Agency [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	104.8	58.6
Other [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	1.1	3.5
Level 1 [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	280.1	231.8
Level 1 [Member] | Cash Equivalents [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	18.9	15.2
Level 1 [Member] | Equity Common Stocks [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	261.2	216.6
Level 1 [Member] | Equity Mutual Funds [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	0	0
Level 1 [Member] | Corporate [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	0	0
Level 1 [Member] | Mutual Funds [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	0	0
Level 1 [Member] | U.S. Treasury and Agency [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	0	0
Level 1 [Member] | Other [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	0	0
Level 2 [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	466.6	364.6
Level 2 [Member] | Cash Equivalents [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	0	0
Level 2 [Member] | Equity Common Stocks [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	0	0
Level 2 [Member] | Equity Mutual Funds [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	215.2	201.1
Level 2 [Member] | Corporate [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	73	68.5
Level 2 [Member] | Mutual Funds [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	72.5	32.9
Level 2 [Member] | U.S. Treasury and Agency [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	104.8	58.6
Level 2 [Member] | Other [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	1.1	3.5
Level 3 [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	0	0
Level 3 [Member] | Cash Equivalents [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	0	0
Level 3 [Member] | Equity Common Stocks [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	0	0
Level 3 [Member] | Equity Mutual Funds [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	0	0
Level 3 [Member] | Corporate [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	0	0
Level 3 [Member] | Mutual Funds [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	0	0
Level 3 [Member] | U.S. Treasury and Agency [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	0	0
Level 3 [Member] | Other [Member] | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	$ 0	$ 0

Employee Benefit Plans - Employ

Employee Benefit Plans - Employee Stock Ownership Plan - Additional Information (Detail) - USD ($) $ in Millions	Apr. 30, 2007	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Retirement Benefits [Abstract]
ESOP loan	$ 216.8	$ 171.8
ESOP, shares to be purchased (in shares)	10,453,575
Loan repayments expected annual through 2036		18.8
Cash dividends paid on unallocated ESOP shares		$ 4.4	$ 4.6	$ 4.8
Minimum age requirement to participate in ESOP		18 years
Minimum work experience within 12 months of hire needed to participate in ESOP		1000 hours
ESOP common stock allocated (in shares)		4,529,883
Unallocated common stock of Employee Stock Ownership Plan (in shares)		5,923,692	6,300,000
Fair value of deferred ESOP shares		$ 100.1
ESOP compensation expense		$ 5.7	$ 6.2	$ 6.4

Employee Benefit Plans - Empl_2

Employee Benefit Plans - Employee Savings Plans - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Maximum percentage of pre-tax compensation an employee can contribute to savings plan	50.00%
Percentage of matching contribution on employee savings plan	100.00%
Trust assets	$ 51	$ 56.4
Employee savings plan expense	646.2	562.9	$ 522.7
Employee Savings Plan [Member] | Supplemental Employee Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Trust assets	17.9
Related benefit obligation	44.2
Employee savings plan expense	$ 32.3	$ 29.1	$ 25.4
Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Maximum percentage employer will match on pre-tax compensation	4.00%

Stock Based Compensation Plans

Stock Based Compensation Plans - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted, vesting period				1 year
Expense related to share-based awards	$ 24,900	$ 22,400	$ 19,800
Long-term incentive plan (in shares)	2,807,692	2,450,861	2,261,586
Total cost of shares repurchased and retired	$ 2,000	$ 2,500	$ 3,400
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expense related to share-based awards	12,200	10,500	7,000
Unamortized cost for unvested options and awards	$ 10,800
Weighted-average vesting period, years	1 year 9 months 18 days
Fair value of restricted stock awards	$ 7,700	100
Unamortized cost for share-based awards estimated forfeiture rate	5.00%
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expense related to share-based awards	$ 5,200	5,200	5,500
Unamortized cost for unvested options and awards	$ 5,100
Weighted-average vesting period, years	1 year 7 months 6 days
Unamortized cost for share-based awards estimated forfeiture rate	5.00%
Intrinsic value of stock options exercised	$ 3,200	8,700	11,200
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expense related to share-based awards	6,600	5,800	6,400
Unamortized cost for unvested options and awards	$ 7,000
Weighted-average vesting period, years	1 year 6 months
Fair value of restricted stock awards	$ 6,000	$ 7,500	$ 9,300
Unamortized cost for share-based awards estimated forfeiture rate	5.00%
Minimum tax withholding obligations upon the vesting of restricted stock awards granted (in shares)	115,632	136,426	216,969
Total cost of shares repurchased and retired	$ 2,000	$ 2,500	$ 3,300
Share based compensation arrangement by share based payment award grants in period weighted average grant date fair value (in dollars per share)	$ 17.44	$ 18.50	$ 18.84
2007 Plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock and stock options per year over a five year period, in years				20.00%
2007 Plans [Member] | Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award service period				5 years
2014 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock reserved for issuance under the Directors' Equity Plan (in shares)	75,850,000
Reserved shares remaining, available for future awards (in shares)	35,633,607
2014 Plan [Member] | Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares depleted for every share subject to award other than option or stock appreciation right (in shares)	7.98
Performance period	3 years
Share based compensation arrangement by share based payment award grants in period weighted average grant date fair value (in dollars per share)	$ 17.84	$ 19.78	$ 18.61
2014 Plan [Member] | Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares depleted for every share subject to award other than option or stock appreciation right (in shares)	5.32
Options granted, vesting period	3 years
2014 Plan [Member] | Restricted Stock [Member] | Share-based Payment Arrangement, Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage	33.00%
2014 Plan [Member] | Restricted Stock [Member] | Share-based Payment Arrangement, Tranche Two [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage	33.00%
2014 Plan [Member] | Restricted Stock [Member] | Share-based Payment Arrangement, Tranche Three [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage	33.00%
Incentive Plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted under the Incentive Plans after two years				66.00%	50.00%
Options granted under the Incentive Plans after three years				100.00%	75.00%
Options granted under the Incentive Plans after four years					100.00%
Options granted under the Incentive Plans after one year				33.00%
New awards granted	0
Long-term incentive plan (in shares)	2,807,692	2,450,861	2,261,586
Weighted-average grant-date fair value of options	$ 2.04	$ 2.31	$ 1.97
Expected volatility rate	19.00%	18.00%	18.00%
Dividend yield	4.00%	3.50%	3.60%
Risk-free interest rate	2.60%	2.60%	1.90%
Expected option life, years	4 years	4 years	4 years
Incentive Plans [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option expiration, maximum term					10 years
Directors' Equity Compensation Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock reserved for issuance under the Directors' Equity Plan (in shares)	1,492,500
Reserved shares remaining, available for future awards (in shares)	333,981
Expense related to share-based awards	$ 900	$ 900	$ 900
New awards granted	58,340	51,680	49,050
Director's equity compensation plan fair value	$ 95
Share based compensation arrangement by share based payment award grants in period weighted average grant date fair value (in dollars per share)	$ 16.31	$ 18.21	$ 17.65

Stock-Based Compensation Plan_2

Stock-Based Compensation Plans - Summary of Performance Share Activity (Detail) - 2014 Plan [Member] - Performance Shares [Member] - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Shares
Unvested shares outstanding, beginning balance (in shares)	1,453,372	984,835	551,985
Granted (in shares)	637,118	532,740	466,923
Forfeited (in shares)	(80,319)	(62,124)	(34,073)
Vested (in shares)	(505,755)	(2,079)
Unvested shares outstanding, ending balance (in shares)	1,504,416	1,453,372	984,835
Weighted-average grant date fair value
Unvested shares outstanding, beginning balance (in dollars per share)	$ 17.85	$ 16.80	$ 15.22
Granted (in dollars per share)	17.84	19.78	18.61
Forfeited (in dollars per share)	18.66	17.82	16.28
Vested (in dollars per share)	15.23	16.70
Unvested shares outstanding, ending balance (in dollars per share)	$ 18.68	$ 17.85	$ 16.80

Stock Based Compensation Plan_2

Stock Based Compensation Plans - Summary of Stock Option Incentive Plan (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Shares Subject To Option
Options outstanding beginning balance (in shares)	14,677,067	14,437,641	16,555,925
Granted (in shares)	2,807,692	2,450,861	2,261,586
Forfeited (in shares)	(652,965)	(294,474)	(459,576)
Exercised (in shares)	(1,632,971)	(1,916,961)	(3,920,294)
Options outstanding, ending balance (in shares)	15,198,823	14,677,067	14,437,641
Options exercisable ending balance (in shares)	10,551,014
Weighted-Average Exercise Price
Options outstanding, beginning balance (in dollars per share)	$ 15.87	$ 15.11	$ 14.84
Granted (in dollars per share)	17.62	19.61	19.14
Forfeited (in dollars per share)	18.28	17.87	17.87
Exercised (in dollars per share)	14.77	14.55	15.97
Options outstanding, ending balance (in dollars per share)	16.20	$ 15.87	$ 15.11
Options exercisable weighted average exercise price (in dollars per share)	$ 15.21
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Options outstanding weighted average remaining contractual term, in years	6 years 2 months 12 days
Options exercisable weighted average remaining contractual term	5 years 2 months 12 days
Options outstanding aggregate intrinsic value	$ 22.7
Options exercisable aggregate intrinsic value	$ 22.7

Stock Based Compensation Plan_3

Stock Based Compensation Plans - Summary of Option Outstanding and Exercisable (Detail)	12 Months Ended
	Dec. 31, 2019$ / sharesshares
$11.53 to $14.54 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Exercise Price minimum	$ 11.53
Options Exercise Price maximum	$ 14.54
Number of options outstanding | shares	3,531,960
Remaining Life	3 years 4 months 24 days
Exercise Price (in dollars per share)	$ 13.53
Number of options exercisable | shares	3,525,520
Weighted Average Exercise Price (in dollars per share)	$ 13.53
$14.55 to $14.88 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Exercise Price minimum	14.55
Options Exercise Price maximum	$ 14.88
Number of options outstanding | shares	4,970,387
Remaining Life	5 years
Exercise Price (in dollars per share)	$ 14.73
Number of options exercisable | shares	4,970,387
Weighted Average Exercise Price (in dollars per share)	$ 14.73
$14.89 to $18.40 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Exercise Price minimum	14.89
Options Exercise Price maximum	$ 18.40
Number of options outstanding | shares	2,689,105
Remaining Life	9 years
Exercise Price (in dollars per share)	$ 17.60
Number of options exercisable | shares	57,997
Weighted Average Exercise Price (in dollars per share)	$ 16.47
$18.41 to $19.71 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Exercise Price minimum	18.41
Options Exercise Price maximum	$ 19.71
Number of options outstanding | shares	4,007,371
Remaining Life	7 years 7 months 6 days
Exercise Price (in dollars per share)	$ 19.45
Number of options exercisable | shares	1,997,110
Weighted Average Exercise Price (in dollars per share)	$ 19.36

Stock Based Compensation Plan_4

Stock Based Compensation Plans - Summary of Restricted Stock Activity (Detail) - Restricted Stock [Member] - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Shares
Unvested shares outstanding, beginning balance (in shares)	730,550	672,321	886,082
Granted (in shares)	383,420	489,789	303,090
Forfeited (in shares)	(68,091)	(29,426)	(31,828)
Vested (in shares)	(347,078)	(402,134)	(485,023)
Unvested shares outstanding, ending balance (in shares)	698,801	730,550	672,321
Weighted-average grant date fair value
Unvested shares outstanding, beginning balance (in dollars per share)	$ 18.03	$ 16.53	$ 14.59
Granted (in dollars per share)	17.44	18.50	18.84
Forfeited (in dollars per share)	17.11	17.81	15.56
Vested (in dollars per share)	17.49	16.04	14.49
Unvested shares outstanding, ending balance (in dollars per share)	$ 18.07	$ 18.03	$ 16.53

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - trust	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of trusts funded to provide benefit payments	2
GSE Mortgage-Backed Securities [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Maturity period of available-for-sale residential mortgage-backed securities portfolio	10 years	10 years
GSE Mortgage-Backed Securities [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Maturity period of available-for-sale residential mortgage-backed securities portfolio	40 years	15 years
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount to impaired loans	10.00%

Fair Value Measurements - Asset

Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Financial assets:
Trading debt securities:	$ 7,100,000	$ 8,400,000
Debt securities available-for-sale, at fair value	3,564,300,000	3,121,000,000
Equity securities	8,200,000	8,100,000
Mortgage servicing rights	10,600,000	0
Other assets	1,853,000,000	1,091,600,000
Fair value of derivative financial instruments	18,400,000	26,000,000
Total	3,971,600,000	3,296,900,000
Financial liabilities:
Fair value of derivative financial instruments	81,600,000	33,800,000
Total	96,200,000	139,000,000
Exchange Traded Funds [Member]
Financial assets:
Other assets	47,700,000	35,500,000
Equity Mutual Funds [Member]
Financial assets:
Other assets	3,300,000	20,600,000
Fixed Income Securities [Member]
Financial assets:
Other assets		300,000
Risk Participation Agreements [Member] | Maximum [Member]
Financial liabilities:
Fair Value of risk participation agreements		100,000
US Treasury [Member]
Financial assets:
Trading debt securities:	7,100,000	8,400,000
U.S. Treasury and Agency [Member]
Financial assets:
Debt securities available-for-sale, at fair value	687,100,000	678,000,000
GSE Mortgage-Backed Securities [Member]
Financial assets:
Debt securities available-for-sale, at fair value	2,877,200,000	2,443,000,000
Interest Rate Swaps [Member]
Financial assets:
Fair value of derivative financial instruments	337,600,000	98,900,000
Financial liabilities:
Fair value of derivative financial instruments	92,100,000	135,000,000
Interest Rate Caps [Member]
Financial assets:
Fair value of derivative financial instruments	1,700,000	3,100,000
Financial liabilities:
Fair value of derivative financial instruments	1,700,000	3,100,000
Foreign Exchange Contracts [Member]
Financial assets:
Fair value of derivative financial instruments	1,200,000	900,000
Financial liabilities:
Fair value of derivative financial instruments	1,800,000	800,000
Forward Commitments to Sell Residential Mortgage Loans [Member]
Financial assets:
Fair value of derivative financial instruments	500,000	100,000
Risk Participation Agreements [Member]
Financial liabilities:
Fair value of derivative financial instruments	100,000	0
Interest Rate-Lock Commitments on Residential Mortgage Loans [Member]
Financial liabilities:
Fair value of derivative financial instruments	500,000	100,000
Level 1 [Member]
Financial assets:
Equity securities	8,200,000	8,100,000
Total	753,400,000	750,600,000
Financial liabilities:
Total	0	0
Level 1 [Member] | Exchange Traded Funds [Member]
Financial assets:
Other assets	47,700,000	35,500,000
Level 1 [Member] | Equity Mutual Funds [Member]
Financial assets:
Other assets	3,300,000	20,600,000
Level 1 [Member] | Fixed Income Securities [Member]
Financial assets:
Other assets		0
Level 1 [Member] | US Treasury [Member]
Financial assets:
Trading debt securities:	7,100,000	8,400,000
Level 1 [Member] | U.S. Treasury and Agency [Member]
Financial assets:
Debt securities available-for-sale, at fair value	687,100,000	678,000,000
Level 1 [Member] | GSE Mortgage-Backed Securities [Member]
Financial assets:
Debt securities available-for-sale, at fair value	0	0
Level 1 [Member] | Interest Rate Swaps [Member]
Financial assets:
Fair value of derivative financial instruments	0	0
Financial liabilities:
Fair value of derivative financial instruments	0	0
Level 1 [Member] | Interest Rate Caps [Member]
Financial assets:
Fair value of derivative financial instruments	0	0
Financial liabilities:
Fair value of derivative financial instruments	0	0
Level 1 [Member] | Foreign Exchange Contracts [Member]
Financial assets:
Fair value of derivative financial instruments	0	0
Financial liabilities:
Fair value of derivative financial instruments	0	0
Level 1 [Member] | Forward Commitments to Sell Residential Mortgage Loans [Member]
Financial assets:
Fair value of derivative financial instruments	0	0
Level 1 [Member] | Risk Participation Agreements [Member]
Financial liabilities:
Fair value of derivative financial instruments	0	0
Level 1 [Member] | Interest Rate-Lock Commitments on Residential Mortgage Loans [Member]
Financial liabilities:
Fair value of derivative financial instruments	0	0
Level 2 [Member]
Financial assets:
Equity securities	0	0
Total	3,218,200,000	2,546,300,000
Financial liabilities:
Total	96,200,000	139,000,000
Level 2 [Member] | Exchange Traded Funds [Member]
Financial assets:
Other assets	0	0
Level 2 [Member] | Equity Mutual Funds [Member]
Financial assets:
Other assets	0	0
Level 2 [Member] | Fixed Income Securities [Member]
Financial assets:
Other assets		300,000
Level 2 [Member] | US Treasury [Member]
Financial assets:
Trading debt securities:	0	0
Level 2 [Member] | U.S. Treasury and Agency [Member]
Financial assets:
Debt securities available-for-sale, at fair value	0	0
Level 2 [Member] | GSE Mortgage-Backed Securities [Member]
Financial assets:
Debt securities available-for-sale, at fair value	2,877,200,000	2,443,000,000
Level 2 [Member] | Interest Rate Swaps [Member]
Financial assets:
Fair value of derivative financial instruments	337,600,000	98,900,000
Financial liabilities:
Fair value of derivative financial instruments	92,100,000	135,000,000
Level 2 [Member] | Interest Rate Caps [Member]
Financial assets:
Fair value of derivative financial instruments	1,700,000	3,100,000
Financial liabilities:
Fair value of derivative financial instruments	1,700,000	3,100,000
Level 2 [Member] | Foreign Exchange Contracts [Member]
Financial assets:
Fair value of derivative financial instruments	1,200,000	900,000
Financial liabilities:
Fair value of derivative financial instruments	1,800,000	800,000
Level 2 [Member] | Forward Commitments to Sell Residential Mortgage Loans [Member]
Financial assets:
Fair value of derivative financial instruments	500,000	100,000
Level 2 [Member] | Risk Participation Agreements [Member]
Financial liabilities:
Fair value of derivative financial instruments	100,000	0
Level 2 [Member] | Interest Rate-Lock Commitments on Residential Mortgage Loans [Member]
Financial liabilities:
Fair value of derivative financial instruments	500,000	100,000
Level 3 [Member]
Financial assets:
Equity securities	0	0
Total	0	0
Financial liabilities:
Total	0	0
Level 3 [Member] | Exchange Traded Funds [Member]
Financial assets:
Other assets	0	0
Level 3 [Member] | Equity Mutual Funds [Member]
Financial assets:
Other assets	0	0
Level 3 [Member] | Fixed Income Securities [Member]
Financial assets:
Other assets		0
Level 3 [Member] | US Treasury [Member]
Financial assets:
Trading debt securities:	0	0
Level 3 [Member] | U.S. Treasury and Agency [Member]
Financial assets:
Debt securities available-for-sale, at fair value	0	0
Level 3 [Member] | GSE Mortgage-Backed Securities [Member]
Financial assets:
Debt securities available-for-sale, at fair value	0	0
Level 3 [Member] | Interest Rate Swaps [Member]
Financial assets:
Fair value of derivative financial instruments	0	0
Financial liabilities:
Fair value of derivative financial instruments	0	0
Level 3 [Member] | Interest Rate Caps [Member]
Financial assets:
Fair value of derivative financial instruments	0	0
Financial liabilities:
Fair value of derivative financial instruments	0	0
Level 3 [Member] | Foreign Exchange Contracts [Member]
Financial assets:
Fair value of derivative financial instruments	0	0
Financial liabilities:
Fair value of derivative financial instruments	0	0
Level 3 [Member] | Forward Commitments to Sell Residential Mortgage Loans [Member]
Financial assets:
Fair value of derivative financial instruments	0	0
Level 3 [Member] | Risk Participation Agreements [Member]
Financial liabilities:
Fair value of derivative financial instruments	0	0
Level 3 [Member] | Interest Rate-Lock Commitments on Residential Mortgage Loans [Member]
Financial liabilities:
Fair value of derivative financial instruments	$ 0	$ 0

Fair Value Measurements - Ass_2

Fair Value Measurements - Assets Measured at Fair Value on Non-Recurring Basis (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale	$ 511.3				$ 19.5				$ 511.3	$ 19.5
Impaired loans	61.9				55.2				61.9	55.2
Mortgage servicing rights	10.6				0				10.6	0
Total	3,971.6				3,296.9				3,971.6	3,296.9
Provision for loan losses (note 5)	7.3	$ 7.8	$ 7.6	$ 5.6	9.9	$ 8.2	$ 6.5	$ 5.4	28.3	30	$ 26
Repossessed assets	4.2				3.9				4.2	3.9
Commercial [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	49								49
Provision for loan losses (note 5)									29.6	27.8	16.2
Retail Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	12.9								12.9
Provision for loan losses (note 5)									(1.3)	2.2	$ 9.8
Nonoperating Income (Expense) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Write downs and net loss on sale of foreclosed/repossessed assets charged to non-interest expense total									1.1	0.2
Impaired Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Provision for loan losses (note 5)									9.3	8.6
REO and Repossessed Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Provision for loan losses (note 5)									2.8	1.7
Other Consumer [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale	333.7								333.7
Other Consumer [Member] | Retail Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	0				0				0	0
Residential Mortgage [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale	19.7				19.5				19.7	19.5
Real estate owned	11.9								11.9
Commercial Real Estate Loan [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Real estate owned	7.3				8.7				7.3	8.7
Commercial Real Estate Loan [Member] | Commercial [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	21				21.8				21	21.8
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	753.4				750.6				753.4	750.6
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	3,218.2				2,546.3				3,218.2	2,546.3
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	0				0				0	0
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	61.9				55.2				61.9	55.2
REO and repossessed assets	23.4				18.1				23.4	18.1
Mortgage servicing rights	10.3								10.3
Total	606.9				92.8				606.9	92.8
Fair Value, Measurements, Nonrecurring [Member] | Commercial Loan [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale	157.9								157.9
Fair Value, Measurements, Nonrecurring [Member] | Other Consumer [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale	333.7								333.7
Fair Value, Measurements, Nonrecurring [Member] | Residential Mortgage [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale	19.7				19.5				19.7	19.5
Fair Value, Measurements, Nonrecurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	0				0				0	0
REO and repossessed assets	0				0				0	0
Mortgage servicing rights	0								0
Total	0				0				0	0
Fair Value, Measurements, Nonrecurring [Member] | Level 1 [Member] | Commercial Loan [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale	0								0
Fair Value, Measurements, Nonrecurring [Member] | Level 1 [Member] | Other Consumer [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale	0								0
Fair Value, Measurements, Nonrecurring [Member] | Level 1 [Member] | Residential Mortgage [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale	0				0				0	0
Fair Value, Measurements, Nonrecurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	0				0				0	0
REO and repossessed assets	0				0				0	0
Mortgage servicing rights	0								0
Total	19.7				19.5				19.7	19.5
Fair Value, Measurements, Nonrecurring [Member] | Level 2 [Member] | Commercial Loan [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale	0								0
Fair Value, Measurements, Nonrecurring [Member] | Level 2 [Member] | Other Consumer [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale	0								0
Fair Value, Measurements, Nonrecurring [Member] | Level 2 [Member] | Residential Mortgage [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale	19.7				19.5				19.7	19.5
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	61.9				55.2				61.9	55.2
REO and repossessed assets	23.4				18.1				23.4	18.1
Mortgage servicing rights	10.3								10.3
Total	587.2				73.3				587.2	73.3
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member] | Commercial Loan [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale	157.9								157.9
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member] | Other Consumer [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale	333.7								333.7
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member] | Residential Mortgage [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale	$ 0				$ 0				$ 0	$ 0

Fair Value Measurements - Carry

Fair Value Measurements - Carrying Amounts and Estimated Fair Values of Financial Instruments (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	$ 484.2	$ 665.7
Short-term investments	316.8	266.3
Debt securities held-to-maturity	3,869.2	3,792.3
FHLB and FRB stock	341.1	303.4
Time deposits	9,205.5	6,916.2
FHLB advances	3,125.4	2,404.5	$ 2,774.4
Federal funds purchased	1,620	845	820
Customer repurchase agreements	409.1	332.9	301.6
Other borrowings	0	11	$ 207.8
Notes and debentures	993.1	895.8
Impaired loans	61.9	55.2
Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	484.2	665.7
Short-term investments	316.8	266.3
Debt securities held-to-maturity	3,869.2	3,792.3
FHLB and FRB stock	341.1	303.4
Total loans, net	43,287.6	34,945.8
Time deposits	9,205.5	6,916.2
Other deposits	34,384	29,242.8
FHLB advances	3,125.4	2,404.5
Federal funds purchased	1,620	845
Customer repurchase agreements	409.1	332.9
Other borrowings		11
Notes and debentures	993.1	895.8
Estimated Fair Value Measurements [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	484.2	665.7
Short-term investments	316.8	266.3
Debt securities held-to-maturity	4,020	3,775.9
FHLB and FRB stock	341.1	303.4
Total loans, net	43,355	34,606.3
Time deposits	9,218.1	6,884
Other deposits	34,384	29,242.8
FHLB advances	3,125.5	2,404.5
Federal funds purchased	1,620	845
Customer repurchase agreements	409.1	332.9
Other borrowings		11
Notes and debentures	1,021.3	893.4
Estimated Fair Value Measurements [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	484.2	665.7
Short-term investments	0	0
Debt securities held-to-maturity	0	0
FHLB and FRB stock	0	0
Total loans, net	0	0
Time deposits	0	0
Other deposits	0	0
FHLB advances	0	0
Federal funds purchased	0	0
Customer repurchase agreements	0	0
Other borrowings		0
Notes and debentures	0	0
Estimated Fair Value Measurements [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	0	0
Short-term investments	316.8	266.3
Debt securities held-to-maturity	4,018.5	3,774.4
FHLB and FRB stock	341.1	303.4
Total loans, net	10,072.1	7,806.1
Time deposits	9,218.1	6,884
Other deposits	34,384	29,242.8
FHLB advances	3,125.5	2,404.5
Federal funds purchased	1,620	845
Customer repurchase agreements	409.1	332.9
Other borrowings		11
Notes and debentures	1,021.3	893.4
Estimated Fair Value Measurements [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	0	0
Short-term investments	0	0
Debt securities held-to-maturity	1.5	1.5
FHLB and FRB stock	0	0
Total loans, net	33,282.9	26,800.2
Time deposits	0	0
Other deposits	0	0
FHLB advances	0	0
Federal funds purchased	0	0
Customer repurchase agreements	0	0
Other borrowings		0
Notes and debentures	$ 0	$ 0

Financial Instruments - Summary

Financial Instruments - Summary of Contractual or Notional Amounts of Financial Instruments (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Commercial and Industrial [Member]
Derivative Instruments And Hedging Activities [Line Items]
Loan origination commitments and unadvanced lines of credit:	$ 5,549.9	$ 4,937.1
Home Equity and Other Consumer [Member]
Derivative Instruments And Hedging Activities [Line Items]
Loan origination commitments and unadvanced lines of credit:	3,401.9	2,646.6
Commercial Real Estate [Member]
Derivative Instruments And Hedging Activities [Line Items]
Loan origination commitments and unadvanced lines of credit:	1,614.9	1,095.4
Equipment Financing [Member]
Derivative Instruments And Hedging Activities [Line Items]
Loan origination commitments and unadvanced lines of credit:	471	459.7
Residential Mortgage [Member]
Derivative Instruments And Hedging Activities [Line Items]
Loan origination commitments and unadvanced lines of credit:	54.7	78.7
Forward Commitments to Sell Residential Mortgage Loans [Member]
Derivative Instruments And Hedging Activities [Line Items]
Derivative Financial Instruments	23.3	9.5
Interest Rate-Lock Commitments on Residential Mortgage Loans [Member]
Derivative Instruments And Hedging Activities [Line Items]
Derivative Financial Instruments	33.6	13.6
Stand-By Letters of Credit [Member]
Derivative Instruments And Hedging Activities [Line Items]
Letters of credit:	185.2	139.4
Commercial Letters of Credit [Member]
Derivative Instruments And Hedging Activities [Line Items]
Letters of credit:	4.4	5
Interest Rate Swaps [Member] | Subordinated Notes [Member]
Derivative Instruments And Hedging Activities [Line Items]
Derivative Financial Instruments	585	585
Interest Rate Swaps [Member] | Customer [Member]
Derivative Instruments And Hedging Activities [Line Items]
Derivative Financial Instruments	8,847.7	7,455.9
Interest Rate Swaps [Member] | Counterparty [Member]
Derivative Instruments And Hedging Activities [Line Items]
Derivative Financial Instruments	8,851.8	7,161.3
Interest Rate Caps [Member] | Customer [Member]
Derivative Instruments And Hedging Activities [Line Items]
Derivative Financial Instruments	246	329.1
Interest Rate Caps [Member] | Counterparty [Member]
Derivative Instruments And Hedging Activities [Line Items]
Derivative Financial Instruments	246	329.1
Risk Participation Agreements [Member]
Derivative Instruments And Hedging Activities [Line Items]
Derivative Financial Instruments	882.8	576.5
Foreign Exchange Contracts [Member]
Derivative Instruments And Hedging Activities [Line Items]
Derivative Financial Instruments	$ 180.4	$ 145.2

Financial Instruments - Additio

Financial Instruments - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Derivative [Line Items]
Average period extended for letter of credit	1 year
Loan commitments and letters of credit	$ 5,600,000	$ 2,700,000
Net liability position, derivative instruments	500,000
Collateral already posted	0
Additional collateral required	500,000
Net unrealized gains (losses) arising during the year		(1,700,000)	$ (1,000,000)
Interest Rate Swaps [Member] | Subordinated Notes [Member]
Derivative [Line Items]
Notional Amounts	585,000,000	585,000,000
Interest Rate Swaps [Member] | Cash Flow [Member] | Loans [Member]
Derivative [Line Items]
Notional Amounts	210,000,000
Interest Rate Swaps [Member] | Fair Value [Member]
Derivative [Line Items]
Notional Amounts	375,000,000
Subordinated notes	$ 400,000,000
Basis points	1.265%
Treasury Forward Interest Rate Locks ("T-Locks") [Member]
Derivative [Line Items]
Period hedged items affected earnings, years	10 years
Net unrealized gains (losses) arising during the year	$ 900,000
Total unrecognized gain	100,000	$ 100,000
Treasury Forward Interest Rate Locks ("T-Locks") [Member] | Subordinated Notes [Member]
Derivative [Line Items]
Senior notes issuance	$ 500,000,000

Financial Instruments - Schedul

Financial Instruments - Schedule of Notional Amounts and Fair Values of Derivatives Outstanding (Detail) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Assets	$ 341,000,000	$ 103,000,000
Liabilities	96,200,000	139,000,000
Forward Commitments to Sell Residential Mortgage Loans [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amounts	23,300,000	9,500,000
Interest Rate-Lock Commitments on Residential Mortgage Loans [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amounts	33,600,000	13,600,000
Derivatives Not Designated as Hedging Instruments [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Assets	341,000,000	103,000,000
Liabilities	96,200,000	139,000,000
Derivatives Not Designated as Hedging Instruments [Member] | Forward Commitments to Sell Residential Mortgage Loans [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amounts	23,300,000	9,500,000
Assets	500,000	100,000
Liabilities	0	0
Derivatives Not Designated as Hedging Instruments [Member] | Interest Rate-Lock Commitments on Residential Mortgage Loans [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amounts	33,600,000	13,600,000
Assets	0	0
Liabilities	500,000	100,000
Designated as Hedging Instrument [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Assets	0	0
Liabilities	0	0
Interest Rate Swaps [Member] | Fair Value [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amounts	375,000,000
Interest Rate Swaps [Member] | Cash Flow [Member] | Loans [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amounts	210,000,000
Interest Rate Swaps [Member] | Derivatives Not Designated as Hedging Instruments [Member] | Commercial Customers [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amounts	8,847,700,000	7,455,900,000
Assets	320,500,000	76,300,000
Liabilities	13,900,000	102,600,000
Interest Rate Swaps [Member] | Derivatives Not Designated as Hedging Instruments [Member] | Institutional Counterparties [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amounts	8,851,800,000	7,161,300,000
Assets	17,100,000	22,600,000
Liabilities	78,200,000	32,400,000
Interest Rate Swaps [Member] | Designated as Hedging Instrument [Member] | Cash Flow [Member] | Loans [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amounts	210,000,000	210,000,000
Assets	0	0
Liabilities	0	0
Interest Rate Swaps [Member] | Designated as Hedging Instrument [Member] | Subordinated Notes [Member] | Fair Value [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amounts	375,000,000	375,000,000
Assets	0	0
Liabilities	0	0
Interest Rate Caps [Member] | Derivatives Not Designated as Hedging Instruments [Member] | Commercial Customers [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amounts	246,000,000	329,100,000
Assets	1,600,000	600,000
Liabilities	100,000	2,500,000
Interest Rate Caps [Member] | Derivatives Not Designated as Hedging Instruments [Member] | Institutional Counterparties [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amounts	246,000,000	329,100,000
Assets	100,000	2,500,000
Liabilities	1,600,000	600,000
Risk Participation Agreements [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amounts	882,800,000	576,500,000
Risk Participation Agreements [Member] | Derivatives Not Designated as Hedging Instruments [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amounts	882,800,000	576,500,000
Assets	0	0
Liabilities	100,000	0
Foreign Exchange Contracts [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amounts	180,400,000	145,200,000
Foreign Exchange Contracts [Member] | Derivatives Not Designated as Hedging Instruments [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amounts	180,400,000	145,200,000
Assets	1,200,000	900,000
Liabilities	$ 1,800,000	$ 800,000

Financial Instruments - Impact

Financial Instruments - Impact of Derivatives on Pre-Tax Income and Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of Pre-Tax Gain (Loss) Recognized in Earnings	$ 24.2	$ 16.3	$ 19.2
Amount of Pre-Tax Gain (Loss) Recognized in AOCL	1.9
Amount of Pre-Tax Gain (Loss) Recognized in AOCL		(1.7)	(1)
Derivatives Not Designated as Hedging Instruments [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of Pre-Tax Gain (Loss) Recognized in Earnings	25	14.7	12.4
Amount of Pre-Tax Gain (Loss) Recognized in AOCL	0
Amount of Pre-Tax Gain (Loss) Recognized in AOCL		0	0
Derivatives Not Designated as Hedging Instruments [Member] | Forward Commitments to Sell Residential Mortgage Loans [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of Pre-Tax Gain (Loss) Recognized in Earnings	0.3	(0.1)	(0.2)
Amount of Pre-Tax Gain (Loss) Recognized in AOCL	0
Amount of Pre-Tax Gain (Loss) Recognized in AOCL		0	0
Derivatives Not Designated as Hedging Instruments [Member] | Interest Rate-Lock Commitments on Residential Mortgage Loans [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of Pre-Tax Gain (Loss) Recognized in Earnings	(0.4)	0.1	0.3
Amount of Pre-Tax Gain (Loss) Recognized in AOCL	0
Amount of Pre-Tax Gain (Loss) Recognized in AOCL		0	0
Derivatives Not Designated as Hedging Instruments [Member] | Interest Rate Swaps [Member] | Commercial Customers [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of Pre-Tax Gain (Loss) Recognized in Earnings	374.9	(3.6)	5.3
Amount of Pre-Tax Gain (Loss) Recognized in AOCL	0
Amount of Pre-Tax Gain (Loss) Recognized in AOCL		0	0
Derivatives Not Designated as Hedging Instruments [Member] | Interest Rate Swaps [Member] | Institutional Counterparties [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of Pre-Tax Gain (Loss) Recognized in Earnings	(350.3)	17.1	6.1
Amount of Pre-Tax Gain (Loss) Recognized in AOCL	0
Amount of Pre-Tax Gain (Loss) Recognized in AOCL		0	0
Derivatives Not Designated as Hedging Instruments [Member] | Interest Rate Caps [Member] | Commercial Customers [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of Pre-Tax Gain (Loss) Recognized in Earnings	1.4	1.1	0.7
Amount of Pre-Tax Gain (Loss) Recognized in AOCL	0
Amount of Pre-Tax Gain (Loss) Recognized in AOCL		0	0
Derivatives Not Designated as Hedging Instruments [Member] | Interest Rate Caps [Member] | Institutional Counterparties [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of Pre-Tax Gain (Loss) Recognized in Earnings	(1.5)	(1)	(0.3)
Amount of Pre-Tax Gain (Loss) Recognized in AOCL	0
Amount of Pre-Tax Gain (Loss) Recognized in AOCL		0	0
Derivatives Not Designated as Hedging Instruments [Member] | Foreign Exchange Contracts [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of Pre-Tax Gain (Loss) Recognized in Earnings	1	0.9	0.5
Amount of Pre-Tax Gain (Loss) Recognized in AOCL	0
Amount of Pre-Tax Gain (Loss) Recognized in AOCL		0	0
Derivatives Not Designated as Hedging Instruments [Member] | Risk Participation Agreements [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of Pre-Tax Gain (Loss) Recognized in Earnings	(0.4)	0.2	0
Amount of Pre-Tax Gain (Loss) Recognized in AOCL	0
Amount of Pre-Tax Gain (Loss) Recognized in AOCL		0	0
Designated as Hedging Instrument [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of Pre-Tax Gain (Loss) Recognized in Earnings	(0.8)	1.6	6.8
Amount of Pre-Tax Gain (Loss) Recognized in AOCL	1.9
Amount of Pre-Tax Gain (Loss) Recognized in AOCL		(1.7)	(1)
Designated as Hedging Instrument [Member] | Cash Flow [Member] | Interest Rate-Lock Commitments on Residential Mortgage Loans [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of Pre-Tax Gain (Loss) Recognized in Earnings	0.1	0.1	0.1
Amount of Pre-Tax Gain (Loss) Recognized in AOCL	0
Amount of Pre-Tax Gain (Loss) Recognized in AOCL		0	0
Designated as Hedging Instrument [Member] | Interest Rate Swaps [Member] | Fair Value [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of Pre-Tax Gain (Loss) Recognized in Earnings	0.3	2.1	5.9
Amount of Pre-Tax Gain (Loss) Recognized in AOCL	0
Amount of Pre-Tax Gain (Loss) Recognized in AOCL		0	0
Designated as Hedging Instrument [Member] | Interest Rate Swaps [Member] | Cash Flow [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of Pre-Tax Gain (Loss) Recognized in Earnings	(1.2)	(0.6)	0.8
Amount of Pre-Tax Gain (Loss) Recognized in AOCL	$ 1.9
Amount of Pre-Tax Gain (Loss) Recognized in AOCL		$ (1.7)	$ (1)

Balance Sheet Offsetting - Summ

Balance Sheet Offsetting - Summary of Gross Presentation, Financial Instruments that are Eligible for Offset in Consolidated Statement of Condition (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Financial assets:
Gross Amount Recognized	$ 18.4	$ 26
Gross Amount Offset	0	0
Net Amount Presented	18.4	26
Gross amounts not offset, financial instruments	(1.9)	(15.7)
Gross amounts not offset, collateral	0	(8.6)
Net Amount	16.5	1.7
Financial liabilities:
Gross Amount Recognized	81.6	33.8
Gross Amount Offset	0	0
Net Amount Presented	81.6	33.8
Gross amounts not offset, financial instruments	(1.9)	(15.7)
Gross amounts not offset, collateral	(77.9)	(1.2)
Net Amount	1.8	16.9
Interest Rate Swaps/Caps [Member]
Financial assets:
Gross Amount Offset	0
Foreign Exchange Contracts [Member]
Financial assets:
Gross Amount Recognized	1.2	0.9
Gross Amount Offset	0	0
Net Amount Presented	1.2	0.9
Gross amounts not offset, financial instruments	0	0
Gross amounts not offset, collateral	0	0
Net Amount	1.2	0.9
Financial liabilities:
Gross Amount Recognized	1.8	0.8
Gross Amount Offset	0	0
Net Amount Presented	1.8	0.8
Gross amounts not offset, financial instruments	0	0
Gross amounts not offset, collateral	0	0
Net Amount	1.8	0.8
Counterparty A [Member] | Interest Rate Swaps/Caps [Member]
Financial assets:
Gross Amount Recognized	0.2	3.1
Gross Amount Offset	0	0
Net Amount Presented	0.2	3.1
Gross amounts not offset, financial instruments	(0.2)	(1.4)
Gross amounts not offset, collateral	0	(1.7)
Net Amount	0	0
Financial liabilities:
Gross Amount Recognized	2.3	1.4
Gross Amount Offset	0	0
Net Amount Presented	2.3	1.4
Gross amounts not offset, financial instruments	(0.2)	(1.4)
Gross amounts not offset, collateral	(2.1)	0
Net Amount	0	0
Counterparty B [Member] | Interest Rate Swaps/Caps [Member]
Financial assets:
Gross Amount Recognized	0.1	2.5
Gross Amount Offset	0	0
Net Amount Presented	0.1	2.5
Gross amounts not offset, financial instruments	(0.1)	(2.5)
Gross amounts not offset, collateral	0	0
Net Amount	0	0
Financial liabilities:
Gross Amount Recognized	5.5	3.8
Gross Amount Offset	0	0
Net Amount Presented	5.5	3.8
Gross amounts not offset, financial instruments	(0.1)	(2.5)
Gross amounts not offset, collateral	(5.4)	(1.2)
Net Amount	0	0.1
Counterparty C [Member] | Interest Rate Swaps/Caps [Member]
Financial assets:
Gross Amount Recognized	0.4	4.8
Gross Amount Offset	0	0
Net Amount Presented	0.4	4.8
Gross amounts not offset, financial instruments	(0.4)	(3.7)
Gross amounts not offset, collateral	0	(1.1)
Net Amount	0	0
Financial liabilities:
Gross Amount Recognized	28.2	3.7
Gross Amount Offset	0	0
Net Amount Presented	28.2	3.7
Gross amounts not offset, financial instruments	(0.4)	(3.7)
Gross amounts not offset, collateral	(27.8)	0
Net Amount	0	0
Counterparty D [Member] | Interest Rate Swaps/Caps [Member]
Financial assets:
Gross Amount Recognized	0.1	3.6
Gross Amount Offset	0	0
Net Amount Presented	0.1	3.6
Gross amounts not offset, financial instruments	(0.1)	(2.7)
Gross amounts not offset, collateral	0	(0.1)
Net Amount	0	0.8
Financial liabilities:
Gross Amount Recognized	10.9	2.7
Gross Amount Offset	0	0
Net Amount Presented	10.9	2.7
Gross amounts not offset, financial instruments	(0.1)	(2.7)
Gross amounts not offset, collateral	(10.8)	0
Net Amount	0	0
Counterparty E [Member] | Interest Rate Swaps/Caps [Member]
Financial assets:
Gross Amount Recognized	15.3	0
Gross Amount Offset		0
Net Amount Presented	15.3	0
Gross amounts not offset, financial instruments	0	0
Gross amounts not offset, collateral	0	0
Net Amount	15.3	0
Financial liabilities:
Gross Amount Recognized	0	16
Gross Amount Offset	0	0
Net Amount Presented	0	16
Gross amounts not offset, financial instruments	0	0
Gross amounts not offset, collateral	0	0
Net Amount	0	16
Other Counterparties [Member] | Interest Rate Swaps/Caps [Member]
Financial assets:
Gross Amount Recognized	1.1	11.1
Gross Amount Offset	0	0
Net Amount Presented	1.1	11.1
Gross amounts not offset, financial instruments	(1.1)	(5.4)
Gross amounts not offset, collateral	0	(5.7)
Net Amount	0	0
Financial liabilities:
Gross Amount Recognized	32.9	5.4
Gross Amount Offset	0	0
Net Amount Presented	32.9	5.4
Gross amounts not offset, financial instruments	(1.1)	(5.4)
Gross amounts not offset, collateral	(31.8)	0
Net Amount	$ 0	$ 0

Balance Sheet Offsetting - Addi

Balance Sheet Offsetting - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
US Treasury [Member]
Offsettting Assets and Liabilities [Line Items]
Fair value of treasury securities	$ 462.4	$ 461.3
Mortgage-Backed Securities [Member]
Offsettting Assets and Liabilities [Line Items]
Fair value of treasury securities	$ 457.5	$ 457

Balance Sheet Offsetting - Su_2

Balance Sheet Offsetting - Summary of Collateral Swaps (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Total repurchase agreements
Total customer repurchase agreements	$ 409.1	$ 332.9	$ 301.6
Collateral Swaps [Member]
Total resale agreements
Gross Amount Recognized	450	450
Gross Amount Offset	(450)	(450)
Net Amount Presented	0	0
Total repurchase agreements
Gross Amount Recognized	450	450
Gross Amount Offset	(450)	(450)
Total customer repurchase agreements	$ 0	$ 0

Segment Information - Additiona

Segment Information - Additional Information (Detail) $ in Millions	Oct. 25, 2019USD ($)branch	Dec. 31, 2019USD ($)	Dec. 31, 2019USD ($)Segment	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Segment Reporting Information [Line Items]
Number of primary operating segments | Segment			3
Number of operating reportable segments | Segment			2
Gain on sale leaseback transaction		$ 3.3	$ 3.3
Net security (gains) losses			(0.2)	$ 9.8	$ 25.4
Other non-interest expense			49.1	11.4	30.6
Charges relating to liquidation of investments			$ 16.5
Other [Member]
Segment Reporting Information [Line Items]
Net security (gains) losses				$ 10	$ 10
Central Maine Branch Sale [Member]
Segment Reporting Information [Line Items]
Number of branches sold | branch	8
Gain on disposal	$ 7.6

Segment Information - Selected

Segment Information - Selected Financial Information Business Segments (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Net interest income (loss)	$ 382.7	$ 348.7	$ 348.1	$ 332.8	$ 332.6	$ 306.4	$ 301.2	$ 295.8	$ 1,412.3	$ 1,236	$ 1,100.5
Provision for loan losses	7.3	7.8	7.6	5.6	9.9	8.2	6.5	5.4	28.3	30	26
Total non-interest income	124.2	106	106.3	94.6	88.7	92.3	94.9	90.4	431.1	366.4	352.9
Total non-interest expense	325.7	281.4	278.4	277.2	262.7	241.3	248.6	243.5	1,162.7	996.1	960.3
Income before income tax expense	173.9	165.5	168.4	144.6	148.7	149.2	141	137.3	652.4	576.3	467.1
Income tax expense (benefit)	36.4	30.4	35.2	30	15.8	32.2	30.8	29.4	132	108.2	129.9
Net income	$ 137.5	$ 135.1	$ 133.2	$ 114.6	$ 132.9	$ 117	$ 110.2	$ 107.9	520.4	468.1	337.2
Average total assets									51,658	45,029.7	42,581.6
Average total liabilities									44,586.7	38,992.5	36,990
Operating Segments [Member]
Segment Reporting Information [Line Items]
Net interest income (loss)									1,362.2	1,166.4	1,034.9
Provision for loan losses									53	47.7	57.1
Total non-interest income									402.4	364.5	348.4
Total non-interest expense									1,048.9	949	904.1
Income before income tax expense									662.7	534.2	422.1
Income tax expense (benefit)									132.8	99.9	117.5
Net income									529.9	434.3	304.6
Average total assets									42,307.7	36,060	34,229
Average total liabilities									34,887.9	30,004.1	28,141.4
Operating Segments [Member] | Commercial Banking Loan [Member]
Segment Reporting Information [Line Items]
Net interest income (loss)									807.1	699.2	631
Provision for loan losses									44.1	38.7	43.7
Total non-interest income									206.5	177.8	165
Total non-interest expense									448.7	383.7	357.1
Income before income tax expense									520.8	454.6	395.2
Income tax expense (benefit)									104.3	85	110
Net income									416.5	369.6	285.2
Average total assets									29,746.8	25,956.7	24,533.9
Average total liabilities									11,490.2	9,305	7,938.6
Operating Segments [Member] | Retail Banking [Member]
Segment Reporting Information [Line Items]
Net interest income (loss)									555.1	467.2	403.9
Provision for loan losses									8.9	9	13.4
Total non-interest income									195.9	186.7	183.4
Total non-interest expense									600.2	565.3	547
Income before income tax expense									141.9	79.6	26.9
Income tax expense (benefit)									28.5	14.9	7.5
Net income									113.4	64.7	19.4
Average total assets									12,560.9	10,103.3	9,695.1
Average total liabilities									23,397.7	20,699.1	20,202.8
Treasury [Member]
Segment Reporting Information [Line Items]
Net interest income (loss)									66.5	93	107.4
Provision for loan losses									0	0	0
Total non-interest income									14.1	8.3	11.2
Total non-interest expense									13.8	17.8	15.6
Income before income tax expense									66.8	83.5	103
Income tax expense (benefit)									13.5	15.8	28.6
Net income									53.3	67.7	74.4
Average total assets									7,882.3	7,955.8	7,512.1
Average total liabilities									9,011.9	8,544.3	8,450.6
Other [Member]
Segment Reporting Information [Line Items]
Net interest income (loss)									(16.4)	(23.4)	(41.8)
Provision for loan losses									(24.7)	(17.7)	(31.1)
Total non-interest income									14.6	(6.4)	(6.7)
Total non-interest expense									100	29.3	40.6
Income before income tax expense									(77.1)	(41.4)	(58)
Income tax expense (benefit)									(14.3)	(7.5)	(16.2)
Net income									(62.8)	(33.9)	(41.8)
Average total assets									1,468	1,013.9	840.5
Average total liabilities									$ 686.9	$ 444.1	$ 398

Parent Company Financial Info_3

Parent Company Financial Information - Condensed Statements of Condition (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Assets:
Cash at bank subsidiary	$ 484.2	$ 665.7
Total cash and cash equivalents	801	932
Equity securities, at fair value	8.2	8.1
Goodwill	3,065.5	2,685.7	$ 2,411.4
Other assets	1,853	1,091.6
Total assets	58,589.8	47,877.3
Liabilities and Stockholders’ Equity:
Notes and debentures	993.1	895.8
Other liabilities	905.5	695.2
Total stockholders’ equity	7,947.2	6,533.9	$ 5,819.9	$ 5,141.9
Total liabilities and stockholders’ equity	58,589.8	47,877.3
People's United Financial, Inc. [Member]
Assets:
Cash at bank subsidiary	455.2	291.6
Total cash and cash equivalents	455.2	291.6
Equity securities, at fair value	8.2	8.1
Goodwill	203	197.1
Due from bank subsidiary	4.6	5.5
Other assets	56	45.9
Total assets	8,531.8	7,036.3
Liabilities and Stockholders’ Equity:
Notes and debentures	579.9	497.7
Other liabilities	4.7	4.7
Total stockholders’ equity	7,947.2	6,533.9
Total liabilities and stockholders’ equity	8,531.8	7,036.3
People's United Financial, Inc. [Member] | Bank Subsidiary [Member]
Assets:
Investments in subsidiaries:	7,800	6,485.3
People's United Financial, Inc. [Member] | Non Bank Subsidiaries [Member]
Assets:
Investments in subsidiaries:	$ 4.8	$ 2.8

Parent Company Financial Info_4

Parent Company Financial Information - Condensed Statements of Income (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues:
Securities									$ 186.5	$ 184.2	$ 153.7
Total interest and dividend income	$ 496.9	$ 470.9	$ 472.8	$ 440.5	$ 431.8	$ 390	$ 375.4	$ 359.1	1,881.1	1,556.3	1,302.4
Net security losses									0.2	(9.8)	(25.4)
Other non-interest income									85.9	50.9	62.6
Expenses:
Interest on notes and debentures									34.9	33.3	29.9
Non-interest expense	325.7	281.4	278.4	277.2	262.7	241.3	248.6	243.5	1,162.7	996.1	960.3
Income tax expense (benefit)	36.4	30.4	35.2	30	15.8	32.2	30.8	29.4	132	108.2	129.9
Net income	$ 137.5	$ 135.1	$ 133.2	$ 114.6	$ 132.9	$ 117	$ 110.2	$ 107.9	520.4	468.1	337.2
People's United Financial, Inc. [Member]
Revenues:
Securities									0.4	0.4	1.1
Total interest and dividend income									0.4	0.4	1.1
Dividend income from bank subsidiary									457	342	292
Net security losses									0	0	(1.2)
Other non-interest income									1.7	2.3	16.9
Total revenues									459.1	344.7	308.8
Expenses:
Interest on notes and debentures									19.2	18.7	19
Non-interest expense									14.1	11.4	13.9
Total expenses									33.3	30.1	32.9
Income (loss) before income tax expense (benefit)									425.8	314.6	275.9
Income tax expense (benefit)									(6.2)	(5.5)	(5.7)
Income before subsidiaries undistributed income									432	320.1	281.6
Subsidiaries undistributed income									88.4	148	55.6
Net income									$ 520.4	$ 468.1	$ 337.2

Parent Company Financial Info_5

Parent Company Financial Information - Condensed Statements of Comprehensive Income (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Condensed Financial Statements, Captions [Line Items]
Net income	$ 137.5	$ 135.1	$ 133.2	$ 114.6	$ 132.9	$ 117	$ 110.2	$ 107.9	$ 520.4	$ 468.1	$ 337.2
Other comprehensive (loss) income, net of tax:
Total other comprehensive income (loss), net of tax									89.9	(37.8)	13.3
Total comprehensive income									610.3	430.3	350.5
People's United Financial, Inc. [Member]
Condensed Financial Statements, Captions [Line Items]
Net income									520.4	468.1	337.2
Other comprehensive (loss) income, net of tax:
Net unrealized losses on securities available-for-sale									0	0	(0.1)
Net unrealized losses on derivatives accounted for as cash flow hedges									(0.1)
Net unrealized losses on derivatives accounted for as cash flow hedges										0	0
Other comprehensive income (loss) of bank subsidiary									90	(37.8)	13.4
Total other comprehensive income (loss), net of tax									89.9	(37.8)	13.3
Total comprehensive income									$ 610.3	$ 430.3	$ 350.5

Parent Company Financial Info_6

Parent Company Financial Information - Condensed Statements of Cash Flows (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash Flows from Operating Activities:
Net income	$ 520.4	$ 468.1	$ 337.2
Adjustments to reconcile net income to net cash provided by operating activities:
Net security (gains) losses	(0.2)	9.8	25.4
Net change in other assets and other liabilities	(466.5)	(40)	38.1
Net cash provided by operating activities	240.8	589.3	603
Cash Flows from Investing Activities:
Proceeds from sales of equity securities	1.6	2.3	0
Proceeds from sales of debt securities available-for-sale	365.3	313.8	1,305.5
Net cash used in investing activities	(310.5)	(0.4)	(693.5)
Cash Flows from Financing Activities:
Repayment of notes and debentures	0	0	(125)
Cash dividends paid on common stock	(274.8)	(243.8)	(227.9)
Cash dividends paid on preferred stock	(14.1)	(14.1)	(14.1)
Common stock repurchases	(4.5)	(2.5)	(3.4)
Proceeds from stock options exercised	24.1	27.9	61.8
Net cash (used in) provided by financing activities	(61.3)	(539.5)	359
Net (decrease) increase in cash, cash equivalents and restricted cash	(131)	49.4	268.5
Cash, cash equivalents and restricted cash at beginning of year	932	882.6	614.1
Cash, cash equivalents and restricted cash at end of year	801	932	882.6
People's United Financial, Inc. [Member]
Cash Flows from Operating Activities:
Net income	520.4	468.1	337.2
Adjustments to reconcile net income to net cash provided by operating activities:
Subsidiaries undistributed income	(88.4)	(148)	(55.6)
Net security (gains) losses	0	0	1.2
Net change in other assets and other liabilities	(0.7)	23.1	20.1
Net cash provided by operating activities	431.3	343.2	302.9
Cash Flows from Investing Activities:
Proceeds from sales of equity securities	1.6	2.3	0
Proceeds from sales of debt securities available-for-sale	0	0	75.6
Increase in investment in bank subsidiary	0	(200)	0
Net cash used in investing activities	1.6	(197.7)	75.6
Cash Flows from Financing Activities:
Repayment of notes and debentures	0	0	(125)
Cash dividends paid on common stock	(274.8)	(243.8)	(227.9)
Cash dividends paid on preferred stock	(14.1)	(14.1)	(14.1)
Common stock repurchases	(4.5)	(2.5)	(3.4)
Proceeds from stock options exercised	24.1	27.9	61.8
Net cash (used in) provided by financing activities	(269.3)	(232.5)	(308.6)
Net (decrease) increase in cash, cash equivalents and restricted cash	163.6	(87)	69.9
Cash, cash equivalents and restricted cash at beginning of year	291.6	378.6	308.7
Cash, cash equivalents and restricted cash at end of year	$ 455.2	$ 291.6	$ 378.6

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - USD ($) $ in Millions	2 Months Ended		7 Months Ended	12 Months Ended
	Mar. 02, 2020	Feb. 21, 2020	Dec. 31, 2019	Dec. 31, 2019	Jun. 30, 2019
Subsequent Event [Line Items]
Shares authorized to be repurchased (in shares)					20,000,000
Treasury stock shares acquired (in shares)			200,000
Treasury stock acquired			$ 2.5	$ 2.5
Consumer Loan
Subsequent Event [Line Items]
Loans held-for-sale			333.7	333.7
Commercial Loan [Member]
Subsequent Event [Line Items]
Loans held-for-sale			$ 157.9	$ 157.9
Subsequent Event [Member]
Subsequent Event [Line Items]
Treasury stock shares acquired (in shares)		10,200,000
Treasury stock acquired		$ 161.9
Gain on sale of loans	$ 15

Selected Quarterly Financial _3

Selected Quarterly Financial Data - Selected Quarterly Financial Data (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information [Line Items]
Interest and dividend income	$ 496.9	$ 470.9	$ 472.8	$ 440.5	$ 431.8	$ 390	$ 375.4	$ 359.1	$ 1,881.1	$ 1,556.3	$ 1,302.4
Interest expense	114.2	122.2	124.7	107.7	99.2	83.6	74.2	63.3	468.8	320.3	201.9
Net interest income	382.7	348.7	348.1	332.8	332.6	306.4	301.2	295.8	1,412.3	1,236	1,100.5
Provision for loan losses	7.3	7.8	7.6	5.6	9.9	8.2	6.5	5.4	28.3	30	26
Net interest income after provision for loan losses	375.4	340.9	340.5	327.2	322.7	298.2	294.7	290.4	1,384	1,206	1,074.5
Non-interest income	124.2	106	106.3	94.6	88.7	92.3	94.9	90.4	431.1	366.4	352.9
Non-interest expense	325.7	281.4	278.4	277.2	262.7	241.3	248.6	243.5	1,162.7	996.1	960.3
Income before income tax expense	173.9	165.5	168.4	144.6	148.7	149.2	141	137.3	652.4	576.3	467.1
Income tax expense (benefit)	36.4	30.4	35.2	30	15.8	32.2	30.8	29.4	132	108.2	129.9
Net income	137.5	135.1	133.2	114.6	132.9	117	110.2	107.9	520.4	468.1	337.2
Preferred stock dividend	3.5	3.5	3.5	3.5	3.5	3.5	3.5	3.5	14.1	14.1	14.1
Net income available to common shareholders	$ 134	$ 131.6	$ 129.7	$ 111.1	$ 129.4	$ 113.5	$ 106.7	$ 104.4	$ 506.3	$ 454	$ 323.1
EPS:
Basic (in dollars per share)	$ 0.31	$ 0.34	$ 0.33	$ 0.30	$ 0.35	$ 0.33	$ 0.31	$ 0.31	$ 1.28	$ 1.30	$ 0.98
Diluted (in dollars per share)	$ 0.31	$ 0.33	$ 0.33	$ 0.30	$ 0.35	$ 0.33	$ 0.31	$ 0.30	$ 1.27	$ 1.29	$ 0.97
Common dividends paid	$ 69.9	$ 69.9	$ 69.8	$ 65.2	$ 65.1	$ 60	$ 59.9	$ 58.8	$ 274.8	$ 243.8	$ 227.9
Dividends paid per common share (in dollars per share)	$ 0.1775	$ 0.1775	$ 0.1775	$ 0.1750	$ 0.1750	$ 0.1750	$ 0.1750	$ 0.1725	$ 0.1775	$ 0.1750
Common dividend payout ratio	52.20%	53.10%	53.80%	58.60%	50.30%	52.90%	56.20%	56.30%	54.30%	53.70%	70.60%
Basic (in shares)	421,850	391,660	391,270	370,720	370,220	341,430	340,640	339,760	394,000	348,100	330,300
Diluted (in shares)	424,980	394,450	394,570	374,090	372,830	345,040	344,470	344,000	397,200	351,700	332,900
Maximum [Member]
EPS:
Stock price (in dollars per share)	$ 17.22	$ 17.10	$ 17.66	$ 18.03	$ 17.46	$ 19	$ 19.37	$ 20.26	$ 17.22	$ 17.46
Minimum [Member]
EPS:
Stock price (in dollars per share)	$ 14.73	$ 13.81	$ 15.24	$ 14.25	$ 13.66	$ 16.95	$ 18	$ 18.18	$ 14.73	$ 13.66

Uncategorized Items - pbct-2019

Label	Element	Value
Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 37,900,000