People's United Financial (PBCT) 10-K 1 Mar 17 2016 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2016	Feb. 17, 2017	Jun. 30, 2016
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	FY
Trading Symbol	PBCT
Entity Registrant Name	People's United Financial, Inc.
Entity Central Index Key	1,378,946
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		316,916,353
Entity Public Float			$ 4,558,358,923

Consolidated Statements of Cond

Consolidated Statements of Condition - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Assets
Cash and due from banks (note 3)	$ 432.4	$ 334.8
Short-term investments (note 3)	181.7	380.5
Total cash and cash equivalents	614.1	715.3
Securities (note 4):
Trading account securities, at fair value	6.8	6.7
Securities available for sale, at fair value	4,409.9	4,527.7
Securities held to maturity, at amortized cost (fair value of $2.01 billion and $1.66 billion)	2,005.4	1,609.6
Federal Home Loan Bank and Federal Reserve Bank stock, at cost	315.8	305.4
Total securities	6,737.9	6,449.4
Loans held for sale (note 5)	39.3	34.5
Loans (note 5):
Total loans	29,744.9	28,410.9
Less allowance for loan losses	(229.3)	(211)
Total loans, net	29,515.6	28,199.9
Goodwill (notes 2 and 6)	1,992.7	1,958.7
Bank-owned life insurance	349.1	346.5
Premises and equipment, net (note 7)	244.5	257.8
Other acquisition-related intangible assets (notes 2 and 6)	149.4	129.1
Other assets (note 8)	967.2	855.5
Total assets	40,609.8	38,946.7
Deposits (note 9):
Non-interest-bearing	6,660.8	6,178.6
Savings	4,397.7	4,199.9
Interest-bearing checking and money market	14,260.1	13,220.8
Time	4,542.2	4,818.1
Total deposits	29,860.8	28,417.4
Borrowings (note 10):
Federal Home Loan Bank advances	3,061.1	3,463.8
Federal funds purchased and other borrowings	652.4	374
Customer repurchase agreements	343.3	469.5
Total borrowings	4,056.8	4,307.3
Notes and debentures (note 11)	1,030.1	1,033.1
Other liabilities (note 8)	520.2	457.3
Total liabilities	35,467.9	34,215.1
Commitments and contingencies (notes 20 and 21)
Stockholders' Equity (note 13)
Preferred stock ($0.01 par value; 50.0 million shares authorized; 10.0 million shares issued and outstanding at December 31, 2016)	244.1
Common stock ($0.01 par value; 1.95 billion shares authorized; 405.0 million shares and 399.2 million shares issued)	4	3.9
Additional paid-in capital	5,446.1	5,337.7
Retained earnings	949.3	880.8
Unallocated common stock of Employee Stock Ownership Plan, at cost (7.0 million shares and 7.3 million shares) (note 17)	(144.6)	(151.8)
Accumulated other comprehensive loss (note 16)	(195)	(177.2)
Treasury stock, at cost (89.1 million shares at both dates)	(1,162)	(1,161.8)
Total stockholders' equity	5,141.9	4,731.6
Total liabilities and stockholders' equity	40,609.8	38,946.7
Commercial [Member]
Loans (note 5):
Total loans	21,404.9	20,750.8
Less allowance for loan losses	(204.9)	(189.7)
Retail Loans [Member]
Loans (note 5):
Total loans	8,340	7,660.1
Less allowance for loan losses	(24.4)	(21.3)
Commercial Real Estate Loan [Member] | Commercial [Member]
Loans (note 5):
Total loans	10,247.3	10,028.8
Commercial and Industrial [Member] | Commercial [Member]
Loans (note 5):
Total loans	8,125.1	7,748.7
Equipment Financing [Member] | Commercial [Member]
Loans (note 5):
Total loans	3,032.5	2,973.3
Residential Mortgage Loan [Member] | Retail Loans [Member]
Loans (note 5):
Total loans	6,216.7	5,457
Home Equity and Other Consumer [Member] | Retail Loans [Member]
Loans (note 5):
Total loans	$ 2,123.3	$ 2,203.1

Consolidated Statements of Con3

Consolidated Statements of Condition (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Securities held to maturity, at fair value	$ 2,012.6	$ 1,662.5
Preferred stock, par value	$ 0.01
Preferred stock, shares authorized	50,000,000
Preferred stock, shares issued	10,000,000
Preferred stock, shares outstanding	10,000,000
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	1,950,000,000	1,950,000,000
Common stock, shares issued	405,000,000	399,200,000
Unallocated common stock of Employee Stock Ownership Plan, shares	6,969,050	7,300,000
Treasury stock, shares	89,100,000	89,100,000

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Interest and dividend income:
Commercial real estate	$ 344.6	$ 343.5	$ 354.2
Residential mortgage	180.4	165.4	153.5
Home equity and other consumer	73.5	72.3	73.9
Total interest on loans	984.4	945.6	932.6
Securities	140.3	121.5	96.8
Loans held for sale	1.1	1.3	0.8
Short-term investments	1.5	0.5	0.4
Total interest and dividend income	1,127.3	1,068.9	1,030.6
Interest expense:
Deposits (note 9)	100.9	95.5	80.9
Borrowings (note 10)	22.8	11.5	11.1
Notes and debentures	31.4	29.8	26.7
Total interest expense	155.1	136.8	118.7
Net interest income	972.2	932.1	911.9
Provision for loan losses (note 5)	36.6	33.4	40.6
Net interest income after provision for loan losses	935.6	898.7	871.3
Non-interest income:
Bank service charges	98	100.7	105.7
Investment management fees	48.3	43.7	41.6
Operating lease income	41.2	42.3	41.6
Insurance revenue	32.9	30.7	29.9
Commercial banking lending fees	31.6	42.6	36.4
Cash management fees	25	24.5	22.9
Brokerage commissions	12.2	12.6	13.6
Net gains on sales of residential mortgage loans (note 5)	6.3	5.5	2.9
Net security (losses) gains (note 4)	(5.9)		3
Gain on sale of business, net of expenses (note 8)		9.2	20.6
Other non-interest income	53.1	40.6	32.6
Total non-interest income	342.7	352.4	350.8
Non-interest expense:
Compensation and benefits (notes 17 and 18)	455.6	449.5	436
Occupancy and equipment (notes 7 and 20)	150.4	149.5	147.3
Professional and outside services	67.8	68	59.2
Regulatory assessments	37.5	35.1	35.6
Operating lease expense	36.3	37.1	37.4
Amortization of other acquisition-related intangible assets (note 6)	23.6	23.9	24.8
Other non-interest expense	97.6	97.5	101.2
Total non-interest expense	868.8	860.6	841.5
Income before income tax expense	409.5	390.5	380.6
Income tax expense (note 12)	128.5	130.4	128.9
Net income	281	260.1	251.7
Preferred stock dividend	1.8
Net income available to common shareholders	$ 279.2	$ 260.1	$ 251.7
Earnings per common share (note 15):
Basic	$ 0.92	$ 0.86	$ 0.84
Diluted	$ 0.92	$ 0.86	$ 0.84
Commercial and Industrial [Member]
Interest and dividend income:
Interest and fee income	$ 255	$ 234.8	$ 225.7
Equipment Financing [Member]
Interest and dividend income:
Interest and fee income	$ 130.9	$ 129.6	$ 125.3

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ 281	$ 260.1	$ 251.7
Net actuarial gains and losses on pension and other postretirement plans:
Net actuarial loss arising during the year	(15.5)	(3.5)	(98.5)
Reclassification adjustment for net actuarial loss included in net income	7.2	9.1	8.4
Net actuarial (loss) gain	(8.3)	5.6	(90.1)
Prior service credit on pension and other postretirement plans:
Reclassification adjustment for prior service credit included in net income	(0.8)	(1)	(1)
Net actuarial (loss) gain and prior service credit	(9.1)	4.6	(91.1)
Net unrealized gains and losses on securities available for sale:
Net unrealized holding (losses) gains arising during the year	(29)	(22.1)	70.9
Reclassification adjustment for net realized losses (gains) included in net income	5.9		(3)
Net unrealized (losses) gains	(23.1)	(22.1)	67.9
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	3.3	3.1	3
Net unrealized gains	3.3	3.1	3
Net unrealized gains and losses on derivatives accounted for as cash flow hedges:
Net unrealized losses arising during the year	(0.2)	(1.1)	(0.9)
Reclassification adjustment for net realized losses included in net income	0.7	1.2	1.3
Net unrealized gains	0.5	0.1	0.4
Other comprehensive loss, before tax	(28.4)	(14.3)	(19.8)
Deferred income tax benefit related to other comprehensive loss	10.6	5.3	6.7
Current period other comprehensive income (loss)	(17.8)	(9)	(13.1)
Total comprehensive income	$ 263.2	$ 251.1	$ 238.6

Consolidated Statements of Chan

Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Millions	Total	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Unallocated ESOP Common Stock [Member]	Accumulated Other Comprehensive Loss [Member]	Treasury Stock [Member]
Beginning Balance at Dec. 31, 2013	$ 4,568.4		$ 3.9	$ 5,277	$ 779	$ (166.2)	$ (155.1)	$ (1,170.2)
Net income	251.7				251.7
Total other comprehensive loss, net of tax (note 16)	(13.1)						(13.1)
Cash dividends on common stock	(196.9)				(196.9)
Restricted stock and performance-based share awards	9.6			2.9	(2)			8.7
Employee Stock Ownership Plan common stock committed to be released (note 17)	5.1				(2.1)	7.2
Common stock repurchased and retired upon vesting of restricted stock awards (note 18)	(3)				(3)
Stock options and related tax benefits	11.3			11.3
Ending Balance at Dec. 31, 2014	4,633.1		3.9	5,291.2	826.7	(159)	(168.2)	(1,161.5)
Net income	260.1				260.1
Total other comprehensive loss, net of tax (note 16)	(9)						(9)
Cash dividends on common stock	(201.2)				(201.2)
Restricted stock and performance-based share awards	10.5			10.6	0.2			(0.3)
Employee Stock Ownership Plan common stock committed to be released (note 17)	5.4				(1.8)	7.2
Common stock repurchased and retired upon vesting of restricted stock awards (note 18)	(3.2)				(3.2)
Stock options and related tax benefits	35.9			35.9
Ending Balance at Dec. 31, 2015	4,731.6		3.9	5,337.7	880.8	(151.8)	(177.2)	(1,161.8)
Proceeds from issuance of preferred stock, net	244.1	$ 244.1
Net income	281				281
Total other comprehensive loss, net of tax (note 16)	(17.8)						(17.8)
Cash dividends on common stock	(205.7)				(205.7)
Cash dividend on preferred stock	(1.8)				(1.8)
Restricted stock and performance-based share awards	9.6			9.7	0.1			(0.2)
Employee Stock Ownership Plan common stock committed to be released (note 17)	5.5				(1.7)	7.2
Common stock repurchased and retired upon vesting of restricted stock awards (note 18)	(3.4)				(3.4)
Stock options and related tax benefits	98.8		0.1	98.7
Ending Balance at Dec. 31, 2016	$ 5,141.9	$ 244.1	$ 4	$ 5,446.1	$ 949.3	$ (144.6)	$ (195)	$ (1,162)

Consolidated Statements of Cha7

Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash dividends on common stock, per share	$ 0.6775	$ 0.6675	$ 0.6575
Retained Earnings [Member]
Cash dividends on common stock, per share	$ 0.6775	$ 0.6675	$ 0.6575

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash Flows from Operating Activities:
Net income	$ 281	$ 260.1	$ 251.7
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of premises and equipment	36.9	39.3	39.6
Provision for loan losses	36.6	33.4	40.6
Expense related to operating leases	36.3	37.1	37.4
Amortization of other acquisition-related intangible assets	23.6	23.9	24.8
Expense related to share-based awards	15.2	17.1	14.9
Deferred income tax expense	3.7	14.1	6.7
Employee Stock Option Plan common stock committed to be released	5.5	5.4	5.1
Net gains on sales of residential mortgage loans	(6.3)	(5.5)	(2.9)
Net security losses (gains)	5.9		(3)
Gain on sale of business, net of expenses		(9.2)	(20.6)
Net (gains) losses on sales of acquired loans		(1.7)	0.9
Originations of loans held-for-sale	(427.8)	(448.3)	(308.4)
Proceeds from sales of loans held-for-sale	429.3	453.5	300.4
Net (increase) decrease in trading account securities	(0.1)	1.6
Net changes in other assets and other liabilities	(104.2)	(92.5)	(37.2)
Net cash provided by operating activities	335.6	328.3	350
Cash Flows from Investing Activities:
Net decrease (increase) in securities purchased under agreements to resell		100	(100)
Proceeds from principal repayments and maturities of securities available for sale	925	821.4	686.7
Proceeds from sales of securities available for sale	647.2	305.9	539.2
Proceeds from principal repayments and maturities of securities held to maturity	117.3	25.6	64.4
Purchases of securities available for sale	(1,486)	(1,766.4)	(879.8)
Purchases of securities held to maturity	(513.1)	(803.3)	(251.4)
Net (purchases) redemptions of Federal Home Loan Bank stock	(1)	10.4
Net purchases of Federal Reserve Bank stock	(9.4)	(140.1)
Proceeds from sales of loans	3.5	31.3	9.7
Loan disbursements, net of principal collections	(1,260.2)	(1,856.5)	(2,241.5)
Purchases of loans	(93.5)	(9.5)
Purchases of premises and equipment	(23.6)	(29.8)	(19.5)
Purchases of leased equipment	(18.8)	(50.5)	(34)
Proceeds from sales of real estate owned	16.8	23.4	14.5
Return of premiums on bank-owned life insurance, net	2.2	1.2	1.4
Cash paid in acquisitions	(59.8)	(10.3)
Net cash used in investing activities	(1,753.4)	(3,347.2)	(2,210.3)
Cash Flows from Financing Activities:
Net increase in deposits	1,443.4	2,279.2	3,580.9
Net (decrease) increase in borrowings with terms of three months or less	(247.7)	619.5	(1,362.2)
Repayments of borrowings with terms of more than three months	(0.2)	(1.3)	(0.6)
Net proceeds from issuance of notes and debentures			394.4
Repayments of notes and debentures			(19)
Proceeds from issuance of preferred stock, net	244.1
Cash dividends paid on common stock	(205.7)	(201.2)	(196.9)
Cash dividend paid on preferred stock	(1.8)
Common stock repurchases	(3.4)	(3.2)	(3)
Proceeds from stock options exercised, including excess income tax benefits	87.9	27.5	6
Net cash provided by financing activities	1,316.6	2,720.5	2,399.6
Net (decrease) increase in cash and cash equivalents	(101.2)	(298.4)	539.3
Cash and cash equivalents at beginning of year	715.3	1,013.7	474.4
Cash and cash equivalents at end of year	614.1	715.3	1,013.7
Supplemental Information:
Interest payments	153.2	136.2	108.8
Income tax payments	113.3	107.8	109.7
Real estate properties acquired by foreclosure	19.4	14.7	17.6
Unsettled purchases of securities	$ 5	$ 5	$ 91.5

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2016
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. Prior to February 23, 2015, the Company was a savings and loan holding company within the meaning of the Home Owners’ Loan Act and the Bank was a federally-chartered savings bank. 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 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. Basis of Financial Statement Presentation The 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. Certain reclassifications have been made to prior year amounts to conform to the current year presentation. 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”); Securities Marketable equity and debt securities (other than those reported as short-term investments) are classified as either trading account securities, held to maturity securities (applicable only to debt securities) or available for sale securities. Management determines the classification of a security at the time of its purchase and reevaluates such classification at each balance sheet date. 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 account securities and reported at fair value with unrealized gains and losses reported in non-interest 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 securities are classified as available for sale and reported at fair value with unrealized gains and losses reported on an after-tax Security transactions are recorded on the trade date. Realized gains and losses are determined using the specific identification method and reported in non-interest Securities transferred from available for sale to held to maturity are recorded at fair value at the date of transfer. The unrealized pre-tax Management conducts a periodic review and evaluation of the 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 non-marketable FRB-NY 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 non-interest 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 A loan is generally considered “non-performing” non-accrual non-accrual non-accrual All previously accrued but unpaid interest on non-accrual non-accrual non-accrual 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 originated loans whose terms have been modified in such a way that they are considered troubled debt restructurings (“TDRs”). Originated 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 non-performing non-accrual non-performing Impairment is evaluated on a collective basis for smaller-balance loans with similar credit risk and on an individual loan 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 Acquired Loans Acquired loans that have evidence of deterioration in credit quality since origination and for which it is probable, at acquisition, that all contractually required payments will not be collected are initially recorded at fair value without recording an 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 Under the accounting model for acquired 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 effective yield method. Accordingly, acquired loans are not subject to classification as non-accrual 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 • Changes in prepayment assumptions • Changes in interest rate indices for variable rate loans 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. An acquired loan 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 re-assessment Allowance and Provision for Loan Losses 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 The Company’s allowance for loan losses consists of three elements: (i) an allowance for larger-balance, non-homogeneous (loan-by-loan) smaller-balance, Larger-balance, Non-homogeneous larger-balance, non-homogeneous charge-off In establishing the allowance for loan losses for larger-balance, non-homogeneous Smaller-balance, Homogeneous Loans. The qualitative component of the allowance for loan losses for smaller-balance, homogenous loans 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 Portfolio-specific risk characteristics include, but are not limited to: (i) collateral values/loan-to non-stated non-owner In establishing the allowance for loan losses for smaller-balance, homogeneous loans, 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 Individually Impaired Loans. non-accrual charge-off charge-off 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 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 commercial real estate portfolios. People’s United did not change its methodologies with respect to determining the allowance for loan losses during 2016. 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, 2016. 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. Loan Charge-Offs The Company’s charge-off charged-off 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 The decision whether to charge-off charge-off Wealth Management and Other Fee-Based Investment management fees are accrued when earned based on total assets managed and administered, which are not reported as assets of People’s United. Insurance revenue represents commissions earned solely from performing broker- and agency-related services. Insurance commission revenues related to agency-billed policies are recognized at the later of the policy billing date or the policy effective date. Insurance commission revenues on premiums directly billed by insurance carriers are generally recognized as revenue during the period commissions are paid by the insurance carrier. Brokerage commissions are recognized on a trade-date basis. Bank service charges are recorded when earned. 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 low-to-moderate 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 An acquirer in a business combination is required, upon initially obtaining control of another entity, to recognize the assets, liabilities and any non-controlling pre-acquisition 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 7 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 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 two-step two-step two-step The first step (“Step 1”) 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 indicator of potential impairment is deemed to exist and a second step is performed to measure the amount of such impairment, if any. At this time, none of the Company’s identified reporting units are at risk of failing the Step 1 goodwill impairment test. The second step (“Step 2”) involves calculating the implied fair value of goodwill for each reporting unit for which impairment was indicated in Step 1. The implied fair value of goodwill is determined in a manner similar to how the amount of goodwill is determined in a business combination (i.e. by measuring the excess of the estimated fair value of the reporting unit, as determined in Step 1, over the aggregate estimated fair values of the individual assets, liabilities, and identifiable intangibles applicable to that reporting unit as of the impairment testing date). If the implied fair value of goodwill exceeds the carrying amount of goodwill assigned to the reporting unit, no impairment exists. If the carrying amount of goodwill assigned to a reporting unit exceeds the implied fair value of the goodwill, an impairment loss is recorded in an amount equal to such excess. An impairment loss cannot exceed the carrying amount of goodwill assigned to a reporting unit, and the loss (write-down) 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. Real Estate Owned Real estate owned (“REO”) properties acquired through foreclosure or deed-in-lieu 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. Tax benefits attributable to deductions in excess of financial statement amounts arising from the exercise of non-statutory paid-in 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 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 two-class two-class 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

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2016
Business Combinations [Abstract]
Acquisitions	NOTE 2 – Acquisitions Acquisitions Completed in 2016 Gerstein Fisher In November 2016, PSI completed its acquisition of Gerstein, Fisher & Associates, Inc. (“Gerstein Fisher”), a $3 billion investment management firm based in New York City, in an all-cash transaction. The acquisition brings People’s United Wealth Management’s total assets under administration to slightly over $21 billion, of which approximately $8 billion are under discretionary management. The fair value of the consideration transferred in the Gerstein Fisher acquisition consisted of $57.4 million in cash and $18.3 million in contingent consideration. The Company’s results of operations for the year ended December 31, 2016 include the results of Gerstein Fisher for November and December 2016. In connection with the acquisition, the Company recorded: (i) goodwill of $31.7 million; (ii) other acquisition-related intangible assets, representing customer relationships, trade name, and non-compete, favorable lease and fund management contracts, totaling $42.3 million; and (iii) other assets totaling $1.7 million. Merger-related expenses recorded in 2016 relating to this transaction totaled $1.9 million. Eagle Insurance In April 2016, PUIA completed its acquisition of Eagle Insurance Group, LLC (“Eagle Insurance”), a Massachusetts-based insurance brokerage firm, focused on commercial insurance, in an all-cash transaction. The fair value of the consideration transferred in the Eagle Insurance acquisition consisted of $2.4 million in cash and $1.5 million in contingent consideration. In connection with the acquisition, the Company recorded (i) goodwill of $2.3 million and (ii) other acquisition-related intangible assets, representing insurance customer relationships, of $1.6 million. Acquisition Completed in 2015 Kesten-Brown Insurance In October 2015, PUIA completed its acquisition of Kesten-Brown Insurance, LLC (“Kesten-Brown”), a Connecticut-based insurance brokerage firm that focuses on commercial lines and employee benefits, in an all-cash 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 (see Note 6). 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, 2016 and 2015, tax deductible goodwill totaled $77.9 million and $24.1 million, respectively.

Cash and Short-Term Investments

Cash and Short-Term Investments	12 Months Ended
	Dec. 31, 2016
Cash and Cash Equivalents [Abstract]
Cash and Short-Term Investments	NOTE 3 – Cash and Short-Term Investments A combination of reserves in the form of deposits with the FRB-NY and vault cash, totaling $91.8 million and $86.0 million at December 31, 2016 and 2015, respectively, were maintained to satisfy federal regulatory requirements. Vault cash is included in cash and due from banks and interest-bearing deposits at 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 had yields of 0.75% and 0.50% at December 31, 2016 and 2015, respectively. Short-term investments consist of the following cash equivalents: As of December 31 (in millions) 2016 2015 Interest-bearing deposits at the FRB-NY $ 169.8 $ 333.7 Money market mutual funds 7.9 8.0 Other (1) 4.0 38.8 Total short-term investments $ 181.7 $ 380.5 (1) Includes cash collateral posted for certain derivative positions at December 31, 2015 (none at December 31, 2016).

Securities

Securities	12 Months Ended
	Dec. 31, 2016
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 securities available for sale and securities held to maturity are as follows: As of December 31, 2016 (in millions) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Securities available for sale: Debt securities: U.S. Treasury and agency $ 889.9 $ 0.3 $ (30.5 ) $ 859.7 GSE mortgage-backed securities and CMOs 3,573.1 15.0 (38.1 ) 3,550.0 Total debt securities 4,463.0 15.3 (68.6 ) 4,409.7 Equity securities 0.2 — — 0.2 Total securities available for sale $ 4,463.2 $ 15.3 $ (68.6 ) $ 4,409.9 Securities held to maturity: Debt securities: State and municipal $ 1,499.1 $ 33.9 $ (23.5 ) $ 1,509.5 GSE mortgage-backed securities 500.8 — (3.2 ) 497.6 Other 5.5 — — 5.5 Total securities held to maturity $ 2,005.4 $ 33.9 $ (26.7 ) $ 2,012.6 As of December 31, 2015 (in millions) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Securities available for sale: Debt securities: U.S. Treasury and agency $ 363.7 $ 0.2 $ (1.1 ) $ 362.8 GSE mortgage-backed securities and CMOs 4,191.3 22.3 (48.9 ) 4,164.7 Total debt securities 4,555.0 22.5 (50.0 ) 4,527.5 Equity securities 0.2 — — 0.2 Total securities available for sale $ 4,555.2 $ 22.5 $ (50.0 ) $ 4,527.7 Securities held to maturity: Debt securities: State and municipal $ 1,019.6 $ 55.8 $ (0.1 ) $ 1,075.3 GSE mortgage-backed securities 588.5 — (2.8 ) 585.7 Other 1.5 — — 1.5 Total securities held to maturity $ 1,609.6 $ 55.8 $ (2.9 ) $ 1,662.5 Securities available for sale with a fair value of $1.83 billion and $1.64 billion at December 31, 2016 and 2015, 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, 2016, based on remaining period to contractual maturity. Information for GSE mortgage-backed securities and CMOs is based on the final contractual maturity dates without considering repayments and prepayments. Available for Sale Held to Maturity (dollars in millions) Amortized Cost Fair Value FTE Yield Amortized Cost Fair Value FTE Yield U.S. Treasury and agency: Within 1 year $ 1.0 $ 1.0 0.56 % $ — $ — — % After 1 but within 5 years 187.8 186.1 1.31 — — — After 5 but within 10 years 701.1 672.6 1.38 — — — Total 889.9 859.7 1.36 — — — GSE mortgage-backed securities and CMOs: After 5 but within 10 years 870.7 884.5 2.40 — — — After 10 years 2,702.4 2,665.5 1.78 500.8 497.6 2.05 Total 3,573.1 3,550.0 1.93 500.8 497.6 2.05 State and municipal: Within 1 year — — — 4.6 4.6 4.42 After 1 but within 5 years — — — 26.9 27.2 4.98 After 5 but within 10 years — — — 365.0 379.3 3.35 After 10 years — — — 1,102.6 1,098.4 4.34 Total — — — 1,499.1 1,509.5 4.11 Other: Within 1 year — — — 1.5 1.5 2.10 After 5 but within 10 years — — — 4.0 4.0 5.00 Total — — — 5.5 5.5 4.21 Total: Within 1 year 1.0 1.0 0.56 6.1 6.1 3.86 After 1 but within 5 years 187.8 186.1 1.31 26.9 27.2 4.98 After 5 but within 10 years 1,571.8 1,557.1 1.94 369.0 383.3 3.37 After 10 years 2,702.4 2,665.5 1.78 1,603.4 1,596.0 3.62 Total $ 4,463.0 $ 4,409.7 1.82 % $ 2,005.4 $ 2,012.6 3.59 % The following tables summarize 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 Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses As of December 31, 2016 (in millions) Securities available for sale: GSE mortgage-backed securities and CMOs $ 2,339.6 $ (26.6 ) $ 396.9 $ (11.5 ) $ 2,736.5 $ (38.1 ) U.S. Treasury and agency 828.3 (30.5 ) — — 828.3 (30.5 ) Securities held to maturity: GSE mortgage-backed securities 497.6 (3.2 ) — — 497.6 (3.2 ) State and municipal 581.7 (23.5 ) — — 581.7 (23.5 ) Total $ 4,247.2 $ (83.8 ) $ 396.9 $ (11.5 ) $ 4,644.1 $ (95.3 ) Continuous Unrealized Loss Position Less Than 12 Months 12 Months Or Longer Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses As of December 31, 2015 (in millions) Securities available for sale: GSE mortgage-backed securities and CMOs $ 2,200.8 $ (20.3 ) $ 933.9 $ (28.6 ) $ 3,134.7 $ (48.9 ) U.S. Treasury and agency 346.3 (1.1 ) — — 346.3 (1.1 ) Securities held to maturity: GSE mortgage-backed securities 585.7 (2.8 ) — — 585.7 (2.8 ) State and municipal 22.3 (0.1 ) 3.7 — 26.0 (0.1 ) Total $ 3,155.1 $ (24.3 ) $ 937.6 $ (28.6 ) $ 4,092.7 $ (52.9 ) At December 31, 2016, approximately 36% of the 1,684 securities owned by the Company, consisting of 125 securities classified as available for sale and 482 securities classified as held to maturity, had gross unrealized losses totaling $68.6 million and $26.7 million, respectively. All of the GSE mortgage-backed securities and CMOs had AAA credit ratings and an average contractual maturity of 12 years. The state and municipal securities had an average credit rating of AA and an average maturity of 14 years. The cause of the gross unrealized losses with respect to all of these 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, 2016 are temporary impairments. No other-than-temporary impairment losses were recognized in the Consolidated Statements of Income for the years ended December 31, 2016, 2015 and 2014. People’s United uses the specific identification method to determine the cost of securities sold and records securities transactions on the trade date. In 2016, People’s United sold U.S. Treasury and CMO securities with an amortized cost of $403 million and recorded $6.1 million of gross realized losses. Including other minor gains and losses, net security losses totaled $5.9 million for the year ended December 31, 2016. The components of net security (losses) gains on debt securities are summarized below. Net gains and losses on trading account securities, which are not included in the table below, totaled less than $0.1 million for each of the years ended December 31, 2016, 2015 and 2014. Years ended December 31 (in millions) 2016 2015 2014 Debt securities: Gains $ 0.2 $ 0.3 $ 4.4 Losses (6.1 ) (0.3 ) (1.4 ) Net security (losses) gains $ (5.9 ) $ — $ 3.0 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 $155.0 million and $154.0 million at December 31, 2016 and 2015, 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 the Smithtown Bancorp, Inc. acquisition, the Bank acquired shares of capital stock in the FHLB of New York (total cost of $11.3 million at both December 31, 2016 and 2015). 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, 2016 and the cost of the investment approximates fair value. Dividend income on FHLB capital stock totaled $5.8 million, $4.6 million and $2.8 million for the years ended December 31, 2016, 2015 and 2014, respectively. The Bank, as a member of the Federal Reserve Bank system beginning in 2015, is currently required to purchase and hold shares of capital stock in the FRB-NY FRB-NY, FRB-NY

Loans

Loans	12 Months Ended
	Dec. 31, 2016
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 • Retail Portfolio 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: 2016 2015 As of December 31 (in millions) Originated Acquired Total Originated Acquired Total Commercial: Commercial real estate $ 10,012.6 $ 234.7 $ 10,247.3 $ 9,696.9 $ 331.9 $ 10,028.8 Commercial and industrial 7,939.0 186.1 8,125.1 7,526.4 222.3 7,748.7 Equipment financing 3,020.9 11.6 3,032.5 2,957.6 15.7 2,973.3 Total Commercial Portfolio 20,972.5 432.4 21,404.9 20,180.9 569.9 20,750.8 Retail: Residential mortgage: Adjustable-rate 5,453.8 95.3 5,549.1 4,733.3 117.9 4,851.2 Fixed-rate 613.5 54.1 667.6 536.1 69.7 605.8 Total residential mortgage 6,067.3 149.4 6,216.7 5,269.4 187.6 5,457.0 Home equity and other consumer: Home equity 2,044.9 27.7 2,072.6 2,115.5 38.2 2,153.7 Other consumer 50.0 0.7 50.7 48.5 0.9 49.4 Total home equity and other consumer 2,094.9 28.4 2,123.3 2,164.0 39.1 2,203.1 Total Retail Portfolio 8,162.2 177.8 8,340.0 7,433.4 226.7 7,660.1 Total loans $ 29,134.7 $ 610.2 $ 29,744.9 $ 27,614.3 $ 796.6 $ 28,410.9 Net deferred loan costs, which are included in loans by respective class and accounted for as interest yield adjustments, totaled $69.9 million and $59.8 million at December 31, 2016 and 2015, respectively. At December 31, 2016, 26%, 19% and 18% of the Company’s loans by outstanding principal amount were to customers located within Connecticut, New York and Massachusetts, respectively. Loans to customers located in the New England states as a group represented 59% of total loans at both December 31, 2016 and 2015, respectively. Substantially the entire equipment financing portfolio (96% and 97% at December 31, 2016 and 2015, respectively) was to customers located outside of New England. At December 31, 2016, 29% of the equipment financing portfolio was to customers located in Texas, California and New York, and no other state exposure was greater than 5%. Commercial real estate loans include construction loans totaling $604.1 million and $630.6 million at December 31, 2016 and 2015, respectively, net of the unadvanced portion of such loans totaling $243.1 million and $314.1 million, respectively. At December 31, 2016, residential mortgage loans included $1.2 billion of interest-only loans compared to $1.1 billion at December 31, 2015. 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 $84.2 million and $105.7 million at December 31, 2016 and 2015, respectively, net of the unadvanced portion of such loans totaling $21.4 million and $38.6 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 $6.3 million, $5.5 million and $2.9 million for the years ended December 31, 2016, 2015 and 2014, respectively. Loans held for sale at December 31, 2016 and 2015 consisted of newly-originated residential mortgage loans with carrying amounts of $39.3 million and $34.5 million, respectively. During 2015 and 2014 (none in 2016), the Company sold acquired loans with outstanding principal balances totaling $24.1 million and $10.4 million, respectively (carrying amounts of $22.3 million and $10.3 million, respectively) and recognized net gains (losses) on sales totaling $1.7 million and $(0.9) 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, 2016, 2015 and 2014. 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, 2013 $ 158.5 $ 9.8 $ 168.3 $ 19.0 $ 0.5 $ 19.5 $ 187.8 Charge-offs (22.3 ) (2.6 ) (24.9 ) (11.1 ) (0.1 ) (11.2 ) (36.1 ) Recoveries 3.6 — 3.6 2.4 — 2.4 6.0 Net loan charge-offs (18.7 ) (2.6 ) (21.3 ) (8.7 ) (0.1 ) (8.8 ) (30.1 ) Provision for loan losses 29.8 2.6 32.4 8.2 — 8.2 40.6 Balance at December 31, 2014 169.6 9.8 179.4 18.5 0.4 18.9 198.3 Charge-offs (20.1 ) — (20.1 ) (7.9 ) — (7.9 ) (28.0 ) Recoveries 4.9 — 4.9 2.4 — 2.4 7.3 Net loan charge-offs (15.2 ) — (15.2 ) (5.5 ) — (5.5 ) (20.7 ) Provision for loan losses 27.4 (1.9 ) 25.5 8.1 (0.2 ) 7.9 33.4 Balance at December 31, 2015 181.8 7.9 189.7 21.1 0.2 21.3 211.0 Charge-offs (13.5 ) (1.4 ) (14.9 ) (8.5 ) — (8.5 ) (23.4 ) Recoveries 2.1 — 2.1 3.0 — 3.0 5.1 Net loan charge-offs (11.4 ) (1.4 ) (12.8 ) (5.5 ) — (5.5 ) (18.3 ) Provision for loan losses 28.4 (0.4 ) 28.0 8.6 — 8.6 36.6 Balance at December 31, 2016 $ 198.8 $ 6.1 $ 204.9 $ 24.2 $ 0.2 $ 24.4 $ 229.3 The following is a summary, by loan portfolio segment and impairment methodology, of the allowance for loan losses and related portfolio balances: As of December 31, 2016 (in millions) Originated Loans Individually Originated Loans Collectively Evaluated for Impairment Acquired Loans (Discounts Related to Credit Quality) Total Portfolio Allowance Portfolio Allowance Portfolio Allowance Portfolio Allowance Commercial $ 161.8 $ 5.8 $ 20,810.7 $ 193.0 $ 432.4 $ 6.1 $ 21,404.9 $ 204.9 Retail 91.8 3.2 8,070.4 21.0 177.8 0.2 8,340.0 24.4 Total $ 253.6 $ 9.0 $ 28,881.1 $ 214.0 $ 610.2 $ 6.3 $ 29,744.9 $ 229.3 As of December 31, 2015 (in millions) Originated Loans Individually Evaluated for Impairment Originated Loans Collectively Evaluated for Impairment Acquired Loans (Discounts Related to Credit Quality) Total Portfolio Allowance Portfolio Allowance Portfolio Allowance Portfolio Allowance Commercial $ 155.1 $ 5.5 $ 20,025.8 $ 176.3 $ 569.9 $ 7.9 $ 20,750.8 $ 189.7 Retail 97.0 3.9 7,336.4 17.2 226.7 0.2 7,660.1 21.3 Total $ 252.1 $ 9.4 $ 27,362.2 $ 193.5 $ 796.6 $ 8.1 $ 28,410.9 $ 211.0 The recorded investments, by class of loan, of originated non-performing As of December 31 (in millions) 2016 2015 2014 Commercial: Commercial real estate $ 22.3 $ 30.2 $ 60.2 Commercial and industrial 41.5 44.9 55.8 Equipment financing 39.4 27.5 25.4 Total (1) 103.2 102.6 141.4 Retail: Residential mortgage 27.4 37.2 37.6 Home equity 17.4 19.5 17.9 Other consumer — 0.1 0.1 Total (2) 44.8 56.8 55.6 Total $ 148.0 $ 159.4 $ 197.0 (1) Reported net of government guarantees totaling $13.1 million, $16.9 million and $17.6 million at December 31, 2016, 2015 and 2014, 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, 2016, the principal loan classes to which these government guarantees relate are commercial and industrial loans (99%) and commercial real estate loans (1%). (2) Includes $9.8 million, $19.9 million and $18.9 million of loans in the process of foreclosure at December 31, 2016, 2015 and 2014, respectively. The preceding table excludes acquired loans that are (i) accounted for as purchased credit impaired loans or (ii) covered by an FDIC loss-share agreement (“LSA”) totaling $21.6 million and $3.1 million, respectively, at December 31, 2016; $27.7 million and $2.3 million, respectively, at December 31, 2015; and $100.6 million and $3.0 million, respectively, at December 31, 2014. Such loans otherwise meet People’s United’s definition of a non-performing If interest payments on all originated loans classified as non-performing non-performing At December 31, 2016 and 2015, People’s United’s recorded investment in originated loans classified as TDRs totaled $189.9 million and $195.7 million, respectively. The related allowance for loan losses was $4.2 million at December 31, 2016 and $5.9 million at December 31, 2015. Interest income recognized on TDRs totaled $4.8 million, $4.6 million and $3.8 million for the years ended December 31, 2016, 2015 and 2014, respectively. Fundings under commitments to lend additional amounts to borrowers with loans classified as TDRs were immaterial for the years ended December 31, 2016, 2015 and 2014. Originated loans that were modified and classified as TDRs during 2016 principally involve reduced payment and/or payment deferral, extension of term (generally no more than two years for commercial loans and nine 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, 2016 and 2015. For purposes of this disclosure, recorded investments represent amounts immediately prior to and subsequent to the restructuring. Year ended December 31, 2016 (dollars in millions) Number of Pre-Modification Outstanding Recorded Investment Post-Modification Outstanding Recorded Investment Commercial: Commercial real estate (1) 18 $ 28.2 $ 28.2 Commercial and industrial (2) 51 44.9 44.9 Equipment financing (3) 61 30.7 30.7 Total 130 103.8 103.8 Retail: Residential mortgage (4) 57 15.5 15.5 Home equity (5) 62 4.5 4.5 Other consumer — — — Total 119 20.0 20.0 Total 249 $ 123.8 $ 123.8 (1) Represents the following concessions: extension of term (13 contracts; recorded investment of $8.1 million); reduced payment and/or payment deferral (3 contracts; recorded investment of $3.0 million); or a combination of concessions (2 contracts; recorded investment of $17.1 million). (2) Represents the following concessions: extension of term (32 contracts; recorded investment of $23.4 million); reduced payment and/or payment deferral (10 contracts; recorded investment of $9.9 million); or a combination of concessions (9 contracts; recorded investment of $11.6 million). (3) Represents the following concessions: extension of term (17 contracts; recorded investment of $6.2 million); reduced payment and/or payment deferral (30 contracts; recorded investment of $17.6 million); or a combination of concessions (14 contracts; recorded investment of $6.9 million). (4) Represents the following concessions: loans restructured through bankruptcy (21 contracts; recorded investment of $3.7 million); reduced payment and/or payment deferral (13 contracts; recorded investment of $5.8 million); or a combination of concessions (23 contracts; recorded investment of $6.0 million). (5) Represents the following concessions: loans restructured through bankruptcy (38 contracts; recorded investment of $2.5 million); reduced payment and/or payment deferral (4 contracts; recorded investment of $0.4 million); or a combination of concessions (20 contracts; recorded investment of $1.6 million). Year ended December 31, 2015 (dollars in millions) Number of Contracts Pre-Modification Outstanding Recorded Investment Post-Modification Outstanding Recorded Investment Commercial: Commercial real estate (1) 26 $ 15.2 $ 15.2 Commercial and industrial (2) 61 80.6 80.6 Equipment financing (3) 48 28.5 28.5 Total 135 124.3 124.3 Retail: Residential mortgage (4) 66 20.1 20.1 Home equity (5) 98 9.5 9.5 Other consumer — — — Total 164 29.6 29.6 Total 299 $ 153.9 $ 153.9 (1) Represents the following concessions: extension of term (21 contracts; recorded investment of $8.9 million); reduced payment and/or payment deferral (2 contracts; recorded investment of $1.2 million); or a combination of concessions (3 contracts; recorded investment of $5.1 million). (2) Represents the following concessions: extension of term (35 contracts; recorded investment of $41.1 million); reduced payment and/or payment deferral (20 contracts; recorded investment of $35.9 million); or a combination of concessions (6 contracts; recorded investment of $3.6 million). (3) Represents the following concessions: extension of term (1 contract; recorded investment of $0.1 million); reduced payment and/or payment deferral (38 contracts; recorded investment of $21.5 million); or a combination of concessions (9 contracts; recorded investment of $6.9 million). (4) Represents the following concessions: loans restructured through bankruptcy (24 contracts; recorded investment of $5.9 million); reduced payment and/or payment deferral (13 contracts; recorded investment of $4.7 million); temporary rate reduction (2 contracts; recorded investment of $0.3 million); or a combination of concessions (27 contracts; recorded investment of $9.2 million). (5) Represents the following concessions: loans restructured through bankruptcy (61 contracts; recorded investment of $5.2 million); reduced payment and/or payment deferral (7 contracts; recorded investment of $0.8 million); temporary rate reduction (1 contract; recorded investment of $0.5 million); or a combination of concessions (29 contracts; recorded investment of $3.0 million). The following is a summary, by class of loan, of information related to TDRs of originated loans completed within the previous 12 months that subsequently defaulted during the years ended December 31, 2016 and 2015. 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 2016 or 2015. 2016 2015 Years ended December 31 (dollars in millions) Number of Contracts Recorded Investment as of Period End Number of Contracts Recorded Investment as of Period End Commercial: Commercial real estate 3 $ 1.1 5 $ 3.2 Commercial and industrial 5 8.6 4 1.2 Equipment financing 20 2.8 9 4.5 Total 28 12.5 18 8.9 Retail: Residential mortgage 12 2.6 17 2.6 Home equity 12 0.8 16 1.8 Other consumer — — — — Total 24 3.4 33 4.4 Total 52 $ 15.9 51 $ 13.3 People’s United’s impaired loans consist of certain originated loans, including all TDRs. The following table summarizes, by class of loan, information related to individually-evaluated impaired loans within the originated portfolio. 2016 2015 As of December 31 (in millions) Unpaid Principal Balance Recorded Investment Related Allowance for Loan Losses Unpaid Principal Balance Recorded Investment Related Allowance for Loan Losses Without a related allowance for loan losses: Commercial: Commercial real estate $ 41.4 $ 40.0 $ — $ 46.5 $ 45.3 $ — Commercial and industrial 50.7 45.7 — 53.2 50.8 — Equipment financing 38.2 35.3 — 32.6 26.0 — Retail: Residential mortgage 63.6 58.0 — 67.2 60.4 — Home equity 22.4 18.7 — 23.3 20.5 — Other consumer — — — — — — Total $ 216.3 $ 197.7 $ — $ 222.8 $ 203.0 $ — With a related allowance for loan losses: Commercial: Commercial real estate $ 12.2 $ 11.4 $ 0.6 $ 18.8 $ 14.7 $ 1.9 Commercial and industrial 25.9 25.0 4.7 19.2 14.7 3.3 Equipment financing 5.0 4.4 0.5 3.8 3.6 0.3 Retail: Residential mortgage 13.1 13.1 2.3 14.1 14.0 2.9 Home equity 2.1 2.0 0.9 2.3 2.1 1.0 Other consumer — — — — — — Total $ 58.3 $ 55.9 $ 9.0 $ 58.2 $ 49.1 $ 9.4 Total impaired loans: Commercial: Commercial real estate $ 53.6 $ 51.4 $ 0.6 $ 65.3 $ 60.0 $ 1.9 Commercial and industrial 76.6 70.7 4.7 72.4 65.5 3.3 Equipment financing 43.2 39.7 0.5 36.4 29.6 0.3 Total 173.4 161.8 5.8 174.1 155.1 5.5 Retail: Residential mortgage 76.7 71.1 2.3 81.3 74.4 2.9 Home equity 24.5 20.7 0.9 25.6 22.6 1.0 Other consumer — — — — — — Total 101.2 91.8 3.2 106.9 97.0 3.9 Total $ 274.6 $ 253.6 $ 9.0 $ 281.0 $ 252.1 $ 9.4 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 2016 2015 2014 Years ended December 31 (in millions) Average Recorded Investment Interest Income Recognized Average Recorded Investment Interest Income Recognized Average Recorded Investment Interest Income Recognized Commercial: Commercial real estate $ 56.7 $ 1.4 $ 65.6 $ 1.6 $ 76.6 $ 1.3 Commercial and industrial 62.6 2.1 71.6 1.8 46.4 1.1 Equipment financing 37.1 0.3 28.0 0.9 28.6 0.7 Total 156.4 3.8 165.2 4.3 151.6 3.1 Retail: Residential mortgage 71.8 1.6 75.2 1.5 71.8 1.5 Home equity 21.6 0.3 21.2 0.3 18.0 0.2 Other consumer — — — — — — Total 93.4 1.9 96.4 1.8 89.8 1.7 Total $ 249.8 $ 5.7 $ 261.6 $ 6.1 $ 241.4 $ 4.8 The following tables summarize, by class of loan, aging information for originated loans: Past Due As of December 31, 2016 (in millions) Current 30-89 90 Days Total Total Commercial: Commercial real estate $ 9,989.9 $ 10.9 $ 11.8 $ 22.7 $ 10,012.6 Commercial and industrial 7,899.2 10.0 29.8 39.8 7,939.0 Equipment financing 2,941.5 68.4 11.0 79.4 3,020.9 Total 20,830.6 89.3 52.6 141.9 20,972.5 Retail: Residential mortgage 6,027.5 22.0 17.8 39.8 6,067.3 Home equity 2,030.3 5.2 9.4 14.6 2,044.9 Other consumer 49.7 0.3 — 0.3 50.0 Total 8,107.5 27.5 27.2 54.7 8,162.2 Total originated loans $ 28,938.1 $ 116.8 $ 79.8 $ 196.6 $ 29,134.7 Included in the “Current” and “30-89 non-performing non-accrual Past Due As of December 31, 2015 (in millions) Current 30-89 90 Days Total Total Commercial: Commercial real estate $ 9,667.7 $ 15.0 $ 14.2 $ 29.2 $ 9,696.9 Commercial and industrial 7,466.5 13.1 46.8 59.9 7,526.4 Equipment financing 2,886.7 63.9 7.0 70.9 2,957.6 Total 20,020.9 92.0 68.0 160.0 20,180.9 Retail: Residential mortgage 5,212.9 31.1 25.4 56.5 5,269.4 Home equity 2,098.9 7.1 9.5 16.6 2,115.5 Other consumer 48.2 0.2 0.1 0.3 48.5 Total 7,360.0 38.4 35.0 73.4 7,433.4 Total originated loans $ 27,380.9 $ 130.4 $ 103.0 $ 233.4 $ 27,614.3 Included in the “Current” and “30-89 non-performing non-accrual 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 smaller-balance, homogeneous loans with similar risk and loss characteristics are also assessed for probable losses. 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 recent historical loss experience, broader portfolio indicators, including trends in delinquencies, non-performing 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 non-owner 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 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 Loans 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 Acquired loans are initially recorded at fair value, determined based upon an estimate of the amount and timing of both principal and interest cash flows expected to be collected and discounted using a market interest rate. 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 portfolio. A decrease in the expected cash flows in subsequent periods requires the establishment of an allowance for loan losses at that time. At December 31, 2016 and 2015, the allowance for loan losses on acquired loans was $6.3 million and $8.1 million, respectively. The following tables summarize, by class of loan, credit quality indicators: As of December 31, 2016 (in millions) Commercial Commercial Equipment Total Commercial: Originated loans: Pass $ 9,817.2 $ 7,580.6 $ 2,617.9 $ 20,015.7 Special mention 107.3 121.9 98.8 328.0 Substandard 87.1 233.3 304.2 624.6 Doubtful 1.0 3.2 — 4.2 Total originated loans 10,012.6 7,939.0 3,020.9 20,972.5 Acquired loans: Pass 182.9 155.5 1.0 339.4 Special mention 13.5 3.6 8.6 25.7 Substandard 37.6 27.0 2.0 66.6 Doubtful 0.7 — — 0.7 Total acquired loans 234.7 186.1 11.6 432.4 Total $ 10,247.3 $ 8,125.1 $ 3,032.5 $ 21,404.9 As of December 31, 2016 (in millions) Residential Home Other Total Retail: Originated loans: Low risk $ 3,016.4 $ 950.9 $ 31.1 $ 3,998.4 Moderate risk 2,538.9 663.9 7.2 3,210.0 High risk 512.0 430.1 11.7 953.8 Total originated loans 6,067.3 2,044.9 50.0 8,162.2 Acquired loans: Low risk 75.7 — — 75.7 Moderate risk 27.5 — — 27.5 High risk 46.2 27.7 0.7 74.6 Total acquired loans 149.4 27.7 0.7 177.8 Total $ 6,216.7 $ 2,072.6 $ 50.7 $ 8,340.0 As of December 31, 2015 (in millions) Commercial Commercial Equipment Total Commercial: Originated loans: Pass $ 9,438.6 $ 7,153.4 $ 2,550.0 $ 19,142.0 Special mention 130.6 121.0 119.1 370.7 Substandard 127.7 250.5 288.5 666.7 Doubtful — 1.5 — 1.5 Total originated loans 9,696.9 7,526.4 2,957.6 20,180.9 Acquired loans: Pass 260.9 175.9 6.1 442.9 Special mention 20.1 6.6 5.0 31.7 Substandard 49.1 39.8 4.6 93.5 Doubtful 1.8 — — 1.8 Total acquired loans 331.9 222.3 15.7 569.9 Total $ 10,028.8 $ 7,748.7 $ 2,973.3 $ 20,750.8 As of December 31, 2015 (in millions) Residential Home Other Total Retail: Originated loans: Low risk $ 2,579.3 $ 959.2 $ 25.8 $ 3,564.3 Moderate risk 2,208.6 651.2 7.9 2,867.7 High risk 481.5 505.1 14.8 1,001.4 Total originated loans 5,269.4 2,115.5 48.5 7,433.4 Acquired loans: Low risk 97.7 — — 97.7 Moderate risk 36.2 — — 36.2 High risk 53.7 38.2 0.9 92.8 Total acquired loans 187.6 38.2 0.9 226.7 Total $ 5,457.0 $ 2,153.7 $ 49.4 $ 7,660.1 Acquired Loans At the respective acquisition dates, on an aggregate basis, the acquired loan portfolio had contractually required principal and interest payments receivable of $7.57 billion; expected cash flows of $7.02 billion; and a fair value (initial carrying amount) of $5.36 billion. The difference between the contractually required principal and interest payments receivable and the expected cash flows ($550.9 million) represented the initial nonaccretable difference. The difference between the expected cash flows and fair value ($1.66 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, 2016, the outstanding principal balance and carrying amount of the acquired loan portfolio were $707.0 million and $610.2 million, respectively ($901.9 million and $796.6 million, respectively, at December 31, 2015). The following table summarizes activity in the accretable yield for the acquired loan portfolio: Years ended December 31 (in millions) 2016 2015 2014 Balance at beginning of period $ 296.0 $ 396.3 $ 639.7 Accretion (39.0 ) (55.5 ) (81.0 ) Reclassification from nonaccretable difference for loans — 1.1 6.7 Other changes in expected cash flows (2) (1.6 ) (45.9 ) (169.1 ) Balance at end of period $ 255.4 $ 296.0 $ 396.3 (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 $1.8 million and $3.5 million at December 31, 2016 and 2015, 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

Goodwill and Other Acquisition-

Goodwill and Other Acquisition-Related Intangible Assets	12 Months Ended
	Dec. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Acquisition-Related Intangible Assets	NOTE 6 – 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, 2014 $ 1,222.8 $ 681.9 $ 49.8 $ 1,954.5 Acquisition of Kesten-Brown — — 4.2 4.2 Balance at December 31, 2015 1,222.8 681.9 54.0 1,958.7 Acquisition of Gerstein Fisher — — 31.7 31.7 Acquisition of Eagle Insurance — — 2.3 2.3 Adjustments (0.7 ) (2.3 ) 3.0 — Balance at December 31, 2016 $ 1,222.1 $ 679.6 $ 91.0 $ 1,992.7 Other Acquisition-Related Intangible Assets The following is a summary of People’s United’s other acquisition-related intangible assets: 2016 2015 As of December 31 (in millions) Gross Accumulated Carrying Gross Accumulated Carrying Intangibles amortized: Trade name intangible $ 123.0 $ 50.3 $ 72.7 $ 122.7 $ 42.8 $ 79.9 Core deposit intangible 143.8 132.0 11.8 143.8 120.0 23.8 Trust relationships 42.7 25.6 17.1 42.7 22.8 19.9 Insurance relationships 38.1 32.0 6.1 36.5 31.0 5.5 Client relationships 24.4 0.3 24.1 — — — Favorable lease agreement 0.7 — 0.7 — — — Non-compete 0.4 — 0.4 — — — Total $ 373.1 $ 240.2 132.9 $ 345.7 $ 216.6 129.1 Mutual fund management contracts (not amortized) 16.5 — Total other acquisition-related $ 149.4 $ 129.1 Other acquisition-related intangible assets subject to amortization have an original weighted-average amortization period of 14 years. Amortization expense of other acquisition-related intangible assets totaled $23.6 million, $23.9 million and $24.8 million for the years ended December 31, 2016, 2015 and 2014, respectively. Scheduled amortization expense attributable to other acquisition-related intangible assets for each of the next five years is as follows: $24.7 million in 2017; $13.2 million in 2018; $12.4 million in 2019; $12.0 million in 2020; and $11.7 million in 2021. There were no impairment losses relating to goodwill or other acquisition-related intangible assets recorded during the years ended December 31, 2016, 2015 and 2014.

Premises and Equipment

Premises and Equipment	12 Months Ended
	Dec. 31, 2016
Property, Plant and Equipment [Abstract]
Premises and Equipment	NOTE 7 – Premises and Equipment The components of premises and equipment are summarized below: As of December 31 (in millions) 2016 2015 Land $ 38.1 $ 38.8 Buildings 265.1 267.6 Leasehold improvements 161.8 158.2 Furniture and equipment 236.2 225.3 Total 701.2 689.9 Less: Accumulated depreciation and amortization 456.7 432.1 Total premises and equipment, net $ 244.5 $ 257.8 Depreciation and amortization expense included in occupancy and equipment expense in the Consolidated Statements of Income totaled $36.9 million, $39.3 million and $39.6 million for the years ended December 31, 2016, 2015 and 2014, respectively.

Other Assets and Other Liabilit

Other Assets and Other Liabilities	12 Months Ended
	Dec. 31, 2016
Text Block [Abstract]
Other Assets and Other Liabilities	NOTE 8 – Other Assets and Other Liabilities The components of other assets are as follows: As of December 31 (in millions) 2016 2015 Affordable housing investments (note 12) $ 195.2 $ 158.4 Leased equipment 176.9 194.4 Fair value of derivative financial instruments (notes 19 and 21) 174.0 158.2 Accrued interest receivable 101.8 90.6 Loans in process 63.9 13.1 Assets held in trust for supplemental retirement plans (note 17) 39.6 36.5 Receivables arising from securities brokerage and insurance businesses 32.0 33.7 Current income tax receivable (note 12) 29.9 26.3 Funded status of defined benefit pension plans (note 17) 29.5 26.6 Investment in joint venture (1) 21.3 22.0 Economic development investments 20.3 19.8 Other prepaid expenses 15.9 15.3 Net deferred tax asset (note 12) 9.4 1.9 Repossessed assets 7.2 9.5 REO: Residential 8.1 7.1 Commercial 4.0 5.5 Other (2) 38.2 36.6 Total other assets (3) $ 967.2 $ 855.5 (1) During the quarter ended June 30, 2014, the Bank formed a joint venture with Vantiv, Inc. to provide a comprehensive suite of payment solutions to businesses throughout the Bank’s footprint. The Bank retained a 49% minority interest in the joint venture and recognized a $20.6 million gain, net of related expenses, resulting from its formation. The gain represented the fair value of the Bank’s entire portfolio of merchant contracts that were contributed to the joint venture and which previously had a zero book basis. The investment in the joint venture is accounted for using the equity method of accounting. (2) During the quarter ended December 31, 2015, the Bank sold its payroll services business and recognized a $9.2 million gain, net of related expenses. The gain represented the fair value of the Bank’s entire portfolio of payroll services customer contracts, which previously had a zero book basis. In connection with this transaction, the Bank recorded a contingent receivable, which totaled $0.3 million and $2.8 million at December 31, 2016 and 2015, respectively. (3) As discussed in Notes 1 and 11, debt issuance costs totaling $5.6 million at December 31, 2015, previously included in other assets, are now included as a component of notes and debentures in the Consolidated Statements of Condition. The components of other liabilities are as follows: As of December 31 (in millions) 2016 2015 Fair value of derivative financial instruments (notes 19 and 21) $ 121.7 $ 109.5 Future contingent commitments for affordable housing investments (note 12) 92.5 74.9 Liabilities for supplemental retirement plans (note 17) 68.1 63.9 Accrued expenses payable (1) 68.0 43.7 Accrued employee benefits 50.6 48.4 Payables arising from securities brokerage and insurance businesses 33.0 34.7 Accrued interest payable 14.2 13.3 Other postretirement plan (note 17) 13.6 14.0 Liability for unsettled purchases of securities 5.0 5.0 Other 53.5 49.9 Total other liabilities $ 520.2 $ 457.3 (1) In connection with recent acquisitions, the Company recorded contingent payables, which totaled $21.4 million and $2.0 million at December 31, 2016 and 2015, respectively (see Note 2).

Deposits

Deposits	12 Months Ended
	Dec. 31, 2016
Banking and Thrift [Abstract]
Deposits	NOTE 9 – Deposits The following is an analysis of People’s United’s total deposits by product type: 2016 2015 Amount Weighted Average Rate Amount Weighted Average Rate As of December 31 (dollars in millions) Non-interest-bearing $ 6,660.8 — % $ 6,178.6 — % Savings 4,397.7 0.14 4,199.9 0.13 Interest-bearing checking and money market 14,260.1 0.27 13,220.8 0.23 Time deposits maturing: Within 3 months 1,054.9 0.70 991.5 0.69 After 3 but within 6 months 852.4 0.75 679.6 0.86 After 6 months but within 1 year 835.2 0.75 1,915.6 1.10 After 1 but within 2 years 1,256.3 1.09 636.1 1.06 After 2 but within 3 years 142.7 1.26 153.5 0.98 After 3 but within 4 years 335.1 1.81 101.9 1.46 After 4 but within 5 years 65.5 1.03 339.6 1.81 After 5 years 0.1 0.93 0.3 2.44 Total 4,542.2 0.93 4,818.1 1.03 Total deposits $ 29,860.8 0.29 % $ 28,417.4 0.30 % Time deposits issued in amounts of $100,000 or more totaled $2.0 billion and $2.1 billion at December 31, 2016 and 2015, respectively. Overdrafts of non-interest-bearing deposit accounts totaling $1.7 million and $1.6 million at December 31, 2016 and 2015, respectively, have been classified as loans. Interest expense on deposits is summarized as follows: Years ended December 31 (in millions) 2016 2015 2014 Savings $ 9.6 $ 11.4 $ 10.9 Interest-bearing checking and money market 43.4 32.1 25.8 Time 47.9 52.0 44.2 Total $ 100.9 $ 95.5 $ 80.9

Borrowings

Borrowings	12 Months Ended
	Dec. 31, 2016
Debt Disclosure [Abstract]
Borrowings	NOTE 10 – Borrowings People’s United’s borrowings are summarized as follows: 2016 2015 As of December 31 (dollars in millions) Amount Weighted Average Rate Amount Weighted Average Rate Fixed-rate FHLB advances maturing: Within 1 month $ 2,250.0 0.69 % $ 2,750.0 0.44 % After 1 month but within 1 year 550.0 0.77 450.0 0.57 After 1 but within 2 years 256.1 2.71 — — After 2 but within 3 years — — 258.6 2.71 After 5 years 5.0 1.34 5.2 1.34 Total FHLB advances 3,061.1 0.87 3,463.8 0.63 Federal funds purchased maturing: Within 1 month 617.0 0.71 374.0 0.32 Total federal funds purchased 617.0 0.71 374.0 0.32 Customer repurchase agreements maturing: Within 1 month 343.3 0.19 469.5 0.19 Total customer repurchase agreements 343.3 0.19 469.5 0.19 Other borrowings maturing: Within 1 year 35.4 0.55 — — Total other borrowings 35.4 0.55 — — Total borrowings $ 4,056.8 0.79 % $ 4,307.3 0.55 % At December 31, 2016, the Bank’s total borrowing capacity from (i) the FHLB of Boston and the FRB-NY single-family Interest expense on borrowings consists of the following: Years ended December 31 (in millions) 2016 2015 2014 FHLB advances $ 19.3 $ 9.8 $ 9.2 Federal funds purchased 2.9 0.8 0.8 Customer repurchase agreements 0.6 0.9 1.0 Other borrowings — — 0.1 Total $ 22.8 $ 11.5 $ 11.1 Information concerning People’s United’s borrowings is presented below: As of and for the years ended December 31 (dollars in millions) 2016 2015 2014 FHLB advances: Balance at year end $ 3,061.1 $ 3,463.8 $ 2,291.7 Average outstanding during the year 3,093.7 2,306.6 2,593.7 Maximum outstanding at any month end 3,562.5 3,463.8 3,419.5 Average interest rate during the year 0.62 % 0.42 % 0.36 % Federal funds purchased: Balance at year end $ 617.0 $ 374.0 $ 913.0 Average outstanding during the year 568.1 411.0 471.8 Maximum outstanding at any month end 872.0 582.0 960.0 Average interest rate during the year 0.50 % 0.19 % 0.17 % Customer repurchase agreements: Balance at year end $ 343.3 $ 469.5 $ 486.0 Carrying amount of collateral securities at year end 350.2 478.9 495.7 Average outstanding during the year 337.2 463.6 482.0 Maximum outstanding at any month end 427.2 504.5 519.2 Average interest rate during the year 0.19 % 0.19 % 0.20 % Other borrowings: Balance at year end $ 35.4 $ — $ 1.0 Carrying amount of collateral securities at year end — — 1.1 Average outstanding during the year 2.8 0.6 57.1 Maximum outstanding at any month end 35.4 1.0 206.2 Average interest rate during the year 0.66 % 1.76 % 0.25 %

Notes and Debentures

Notes and Debentures	12 Months Ended
	Dec. 31, 2016
Brokers and Dealers [Abstract]
Notes and Debentures	NOTE 11 – Notes and Debentures Notes and debentures are summarized as follows: As of December 31 (in millions) 2016 2015 People’s United Financial, Inc.: 3.65% senior notes due 2022 $ 496.5 $ 496.0 5.80% fixed-rate/floating-rate subordinated notes due 2017 125.0 123.7 People’s United Bank: 4.00% subordinated notes due 2024 408.6 413.4 Total notes and debentures $ 1,030.1 $ 1,033.1 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 5.80% fixed-rate/floating-rate subordinated notes in connection with its acquisition of Chittenden Corporation (“Chittenden”). These subordinated notes, which were issued in 2007 and are due in February 2017, represent unsecured general obligations of People’s United with interest payable semi-annually. The 4.00% subordinated notes represent fixed-rate unsecured and subordinated obligations of the Bank with interest payable semi-annually. The Bank may redeem the notes, in whole or in part, on or after April 16, 2024 at a redemption price equal to 100% of the principal amount of the notes to be redeemed, plus accrued and unpaid interest to, but excluding, the redemption date. The Bank may redeem the notes in whole, but not in part, at its option at a redemption price equal to 100% of the principal amount of the notes together with accrued but unpaid interest to, but excluding, the date fixed for redemption, within 90 days of the occurrence of a “regulatory event” (as defined). Pursuant to capital regulations of the OCC, effective January 1, 2015, the Bank may not redeem the notes prior to maturity without the prior approval of the OCC. The Bank has entered into a pay floating/receive fixed interest rate swap to hedge the change in fair value of the subordinated notes due to changes in interest rates (see Note 21). For regulatory capital purposes, subordinated note issuances qualify, up to certain limits, as Tier 2 capital for both People’s United’s and the Bank’s Total risk-based capital (see Note 14). As discussed in Note 1, effective January 1, 2016, the Company adopted, with retrospective application, amended standards with respect to the presentation of debt issuance costs by changing the presentation of such costs from an asset on the statement of condition to a deduction from the related debt liability. The adoption of this new guidance did not impact the Company’s results of operations or cash flows. In accordance with the amended standard, debt issuance costs totaling $5.6 million at December 31, 2015, previously included in other assets, are now included as a component of notes and debentures in the Consolidated Statements of Condition.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Income Taxes	NOTE 12 – Income Taxes The following is a summary of total income tax expense: Years ended December 31 (in millions) 2016 2015 2014 Income tax expense applicable to pre-tax $ 128.5 $ 130.4 $ 128.9 Deferred income tax benefit applicable to items reported in total other comprehensive loss (note 16) (10.6 ) (5.3 ) (6.7 ) Total $ 117.9 $ 125.1 $ 122.2 The components of income tax expense applicable to pre-tax Years ended December 31 (in millions) 2016 2015 2014 Current tax expense: Federal $ 109.7 $ 103.6 $ 111.9 State 15.1 12.7 10.3 Total current tax expense 124.8 116.3 122.2 Deferred tax expense (1) 3.7 14.1 6.7 Total income tax expense $ 128.5 $ 130.4 $ 128.9 (1) Includes the effect of decreases in the valuation allowance for state deferred tax assets of $1.3 million, $0.1 million and $1.2 million in 2016, 2015 and 2014, respectively. The following is a reconciliation of expected income tax expense, computed at the U.S. federal statutory rate of 35%, to actual income tax expense: Years ended December 31 (dollars in millions) 2016 2015 2014 Expected income tax expense $ 143.3 $ 136.7 $ 133.2 State income tax, net of federal tax effect 10.0 9.3 8.2 Tax-exempt (20.0 ) (16.4 ) (13.2 ) Federal income tax credits (5.3 ) (0.4 ) 0.8 Tax-exempt (2.0 ) (1.6 ) (2.0 ) Other, net 2.5 2.8 1.9 Actual income tax expense $ 128.5 $ 130.4 $ 128.9 Effective income tax rate 31.4 % 33.4 % 33.9 % 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 variable interest entities, 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 ($195.2 million and $158.4 million at December 31, 2016 and 2015, respectively). Included in other liabilities in the Consolidated Statements of Condition is a liability for all legally binding unfunded commitments to fund future investments ($92.5 million and $74.9 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 $12.6 million, $12.6 million and $10.7 million for the years ended December 31, 2016, 2015 and 2014, respectively. 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 $1.4 billion at December 31, 2016 and expire between 2020 and 2036. 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) 2016 2015 Deferred tax assets: Leasing activities $ 122.2 $ 101.5 Allowance for loan losses and non-accrual 90.2 82.7 State tax net operating loss carryforwards, net of federal tax effect 66.3 68.0 Equity-based compensation 19.0 22.9 Unrealized loss on securities available for sale 18.7 10.8 Pension and other postretirement benefits 10.9 12.2 Unrealized loss on securities transferred to held to maturity 10.2 12.0 Other deductible temporary differences 37.1 35.1 Total deferred tax assets 374.6 345.2 Less: valuation allowance for state deferred tax assets (66.7 ) (68.0 ) Total deferred tax assets, net of the valuation allowance 307.9 277.2 Deferred tax liabilities: Tax over book depreciation (207.1 ) (185.4 ) Acquisition-related deferred tax liabilities (35.3 ) (39.9 ) Book over tax income recognized on consumer loans (18.4 ) (14.6 ) Mark-to-market (16.0 ) (7.3 ) Deferred cancellation-of-indebtedness (9.0 ) (13.4 ) Temporary differences related to merchant services joint venture (6.3 ) (6.8 ) Other taxable temporary differences (6.4 ) (7.9 ) Total deferred tax liabilities (298.5 ) (275.3 ) Net deferred tax asset $ 9.4 $ 1.9 Based on People’s United’s recent historical and anticipated future pre-tax People’s United’s current income tax receivable at December 31, 2016 and 2015 totaled $29.9 million and $26.3 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) 2016 2015 2014 Balance at beginning of year $ 2.7 $ 3.0 $ 3.0 Additions for tax positions taken in prior years 0.1 0.1 0.1 Reductions for tax positions taken in prior years — — — Reductions attributable to audit settlements/lapse of statute of limitations — (0.4 ) (0.1 ) Balance at end of year $ 2.8 $ 2.7 $ 3.0 If recognized, the unrecognized income tax benefits at December 31, 2016 would minimally affect People’s United’s annualized income tax rate. Accrued interest expense related to the unrecognized income tax benefits totaled $0.7 million and $0.6 million at December 31, 2016 and 2015, respectively. People’s United recognizes accrued interest related to unrecognized income tax benefits and penalties, if incurred, as components of income tax expense in the Consolidated Statements of Income. The amount of total unrecognized income tax benefits is not expected to change significantly within the next twelve months. People’s United files a consolidated U.S. Federal income tax return and various state income tax returns and is no longer subject to federal or state income tax examinations through 2011.

Stockholders' Equity and Divide

Stockholders' Equity and Dividends	12 Months Ended
	Dec. 31, 2016
Equity [Abstract]
Stockholders' Equity and Dividends	NOTE 13 – Stockholders’ Equity and Dividends People’s United is authorized to issue 50.0 million shares of preferred stock, par value of $0.01 per share, of which 10.0 million shares were outstanding as of December 31, 2016, and 1.95 billion shares of common stock, par value of $0.01 per share, of which 405.0 million shares were issued as of December 31, 2016. On October 31, 2016, People’s United issued 10.0 million shares of fixed-to-floating non-cumulative 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 (86.4 million shares at December 31, 2016) 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”) (2.7 million shares at December 31, 2016). Following shareholder approval of the People’s United Financial, Inc. 2014 Long-Term 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, 2016, 7.0 million shares of People’s United common stock, with a contra-equity balance of $144.6 million, have not been allocated or committed to be released. Common dividends declared and paid per common share totaled $0.6775, $0.6675 and $0.6575 for the years ended December 31, 2016, 2015 and 2014, respectively. People’s United’s common dividend payout ratio (common dividends paid as a percentage of net income available to common shareholders) was 73.7%, 77.3% and 78.2% for the years ended December 31, 2016, 2015 and 2014, respectively. In the ordinary course of business, People’s United 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 14 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. In 2016, 2015 and 2014, the Bank paid a total of $271.0 million, $245.0 million and $244.0 million, respectively, in cash dividends to People’s United (parent company). At December 31, 2016, the Bank’s retained net income, as defined by federal regulations, totaled $42.8 million.

Regulatory Capital Requirements

Regulatory Capital Requirements	12 Months Ended
	Dec. 31, 2016
Banking and Thrift [Abstract]
Regulatory Capital Requirements	NOTE 14 – 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. On January 1, 2015, both People’s United and the Bank became subject to new capital rules (the “Basel III capital rules”) issued by U.S. banking agencies. The Basel III capital rules, among other things: (i) introduced as a new capital measure “Common Equity Tier 1” (“CET 1”) capital; (ii) specified that Tier 1 capital consists of CET 1 capital and “Additional Tier 1 Capital” instruments meeting specified requirements; (iii) defined CET 1 capital narrowly by requiring that most adjustments to regulatory capital measures be made to CET 1 capital and not to the other components of capital; and (iv) expanded the scope of the adjustments as compared to prior regulations. When fully phased-in phased-in phased-in phased-in 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 2016, the capital conservation buffer is 0.625%. The foregoing capital ratios are based in part on specific quantitative measures of assets, liabilities and certain off-balance-sheet Management believes that, as of December 31, 2016, 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. 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 improvement in People’s United’s Tier 1 and Total risk-based capital ratios since December 31, 2015 reflects, in part, the issuance of preferred stock in October 2016, which qualifies as a Tier 1 capital instrument (see Note 13). The improvement in the Bank’s capital ratios since December 31, 2015 reflects equity contributions from People’s United (parent company) during 2016. The minimum capital required amounts as of December 31, 2016 and 2015 are based on the capital conservation buffer phase-in opt-out As of December 31, 2016 Minimum Capital Phase-In Classification as (dollars in millions) Amount Ratio Amount Ratio Amount Ratio Tier 1 Leverage Capital (1): People’s United $ 3,256.1 8.4 % $ 1,546.7 4.0 % $ 1,933.4 5.0 % Bank 3,430.5 8.9 1,537.0 4.0 1,921.2 5.0 CET 1 Risk-Based Capital (2): People’s United 3,012.0 9.9 1,565.2 5.125 1,985.1 6.5 Bank 3,430.5 11.3 1,562.5 5.125 1,981.8 6.5 Tier 1 Risk-Based Capital (3): People’s United 3,256.1 10.7 2,023.3 6.625 2,443.2 8.0 Bank 3,430.5 11.3 2,019.9 6.625 2,439.1 8.0 Total Risk-Based Capital (4): People’s United 3,802.9 12.5 2,634.1 8.625 3,054.0 10.0 Bank 4,062.1 13.3 2,629.7 8.625 3,048.9 10.0 As of December 31, 2015 Minimum Capital Phase-In Classification as Well-Capitalized (dollars in millions) Amount Ratio Amount Ratio Amount Ratio Tier 1 Leverage Capital (1): People’s United $ 2,898.1 8.0 % $ 1,440.6 4.0 % $ 1,800.8 5.0 % Bank 3,012.7 8.4 1,431.9 4.0 1,789.8 5.0 CET 1 Risk-Based Capital (2): People’s United 2,898.1 9.8 1,620.7 4.5 2,341.0 6.5 Bank 3,012.7 10.2 1,610.9 4.5 2,326.8 6.5 Tier 1 Risk-Based Capital (3): People’s United 2,898.1 9.8 1,778.8 6.0 2,371.7 8.0 Bank 3,012.7 10.2 1,777.3 6.0 2,369.7 8.0 Total Risk-Based Capital (4): People’s United 3,470.5 11.7 2,371.7 8.0 2,964.6 10.0 Bank 3,726.3 12.6 2,369.7 8.0 2,962.1 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 (ii) after-tax (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. Management currently estimates that, as of December 31, 2016, both the Company’s and the Bank’s risk-based 10-20 phased-in”

Earnings Per Common Share

Earnings Per Common Share	12 Months Ended
	Dec. 31, 2016
Earnings Per Share [Abstract]
Earnings Per Common Share	NOTE 15 – 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 Years ended December 31 (in millions, except per share data) 2016 2015 2014 Net income available to common shareholders $ 279.2 $ 260.1 $ 251.7 Dividends paid on and undistributed earnings allocated to participating securities (0.9 ) (1.1 ) (1.2 ) Earnings attributable to common shareholders $ 278.3 $ 259.0 $ 250.5 Weighted average common shares outstanding for basic EPS 303.1 300.4 298.2 Effect of dilutive equity-based awards 0.9 — 0.1 Weighted average common and common-equivalent shares for diluted EPS 304.0 300.4 298.3 Basic EPS $ 0.92 $ 0.86 $ 0.84 Diluted EPS $ 0.92 $ 0.86 $ 0.84 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 13.6 million shares, 19.7 million shares and 17.7 million shares for the years ended December 31, 2016, 2015 and 2014, respectively, have also been excluded from the calculation of diluted EPS.

Comprehensive Income

Comprehensive Income	12 Months Ended
	Dec. 31, 2016
Equity [Abstract]
Comprehensive Income	NOTE 16 – Comprehensive Income Comprehensive income represents the sum of net income and items of “other comprehensive income or loss,” including (on an after-tax 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 (in millions) Pension and Other Net Unrealized on Securities Net Unrealized Net Unrealized Cash Flow Hedges Total Balance at December 31, 2013 $ (85.0 ) $ (46.5 ) $ (23.3 ) $ (0.3 ) $ (155.1 ) Other comprehensive income (loss) before reclassifications (62.6 ) 44.6 — (0.6 ) (18.6 ) Amounts reclassified from AOCL (1) 4.7 (1.8 ) 1.8 0.8 5.5 Current period other comprehensive income (loss) (57.9 ) 42.8 1.8 0.2 (13.1 ) Balance at December 31, 2014 (142.9 ) (3.7 ) (21.5 ) (0.1 ) (168.2 ) Other comprehensive income (loss) before reclassifications (2.2 ) (14.0 ) — (0.7 ) (16.9 ) Amounts reclassified from AOCL (1) 5.1 — 2.0 0.8 7.9 Current period other comprehensive income (loss) 2.9 (14.0 ) 2.0 0.1 (9.0 ) Balance at December 31, 2015 (140.0 ) (17.7 ) (19.5 ) — (177.2 ) Other comprehensive income (loss) before reclassifications (9.6 ) (18.3 ) — (0.1 ) (28.0 ) Amounts reclassified from AOCL (1) 4.0 3.7 2.1 0.4 10.2 Current period other comprehensive income (loss) (5.6 ) (14.6 ) 2.1 0.3 (17.8 ) Balance at December 31, 2016 $ (145.6 ) $ (32.3 ) $ (17.4 ) $ 0.3 $ (195.0 ) (1) See the following table for details about these reclassifications. The following is a summary of the amounts reclassified from AOCL: Years ended December 31 (in millions) Amounts Reclassified from AOCL Affected Line Item in the Statement Where Net Income is Presented 2016 2015 2014 Details about components of AOCL: Amortization of pension and other postretirement plans items: Net actuarial loss $ (7.2 ) $ (9.1 ) $ (8.4 ) (1) Prior service credit 0.8 1.0 1.0 (1) (6.4 ) (8.1 ) (7.4 ) Income before income tax expense 2.4 3.0 2.7 Income tax expense (4.0 ) (5.1 ) (4.7 ) Net income Reclassification adjustment for net realized (losses) gains on securities available for sale (5.9 ) — 3.0 Income before income tax expense (2) 2.2 — (1.2 ) Income tax expense (3.7 ) — 1.8 Net income Amortization of unrealized losses on securities transferred to held to maturity (3.3 ) (3.1 ) (3.0 ) Income before income tax expense (3) 1.2 1.1 1.2 Income tax expense (2.1 ) (2.0 ) (1.8 ) Net income Amortization of unrealized gains and losses on cash flow hedges: Interest rate swaps (0.8 ) (1.3 ) (1.4 ) (4) Interest rate locks 0.1 0.1 0.1 (4) (0.7 ) (1.2 ) (1.3 ) Income before income tax expense 0.3 0.4 0.5 Income tax expense (0.4 ) (0.8 ) (0.8 ) Net income Total reclassifications for the period $ (10.2 ) $ (7.9 ) $ (5.5 ) (1) Included in the computation of net periodic benefit income (expense) reflected in compensation and benefits expense (see Note 17 for additional details). (2) Included in non-interest (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) 2016 2015 2014 Net actuarial loss and other amounts related to pension and other postretirement plans $ 85.0 $ 81.5 $ 83.2 Net unrealized loss on securities available for sale 18.8 10.3 2.2 Net unrealized loss on securities transferred to held to maturity 10.2 11.4 12.5 Net unrealized gain on derivatives accounted for as cash flow hedges (0.2 ) — — Total deferred income taxes $ 113.8 $ 103.2 $ 97.9 The following is a summary of the components of People’s United’s total other comprehensive loss: Pre-Tax After-Tax Year ended December 31, 2016 (in millions) Amount Tax Effect Amount Net actuarial gains and losses on pension and other postretirement plans: Net actuarial loss arising during the year $ (15.5 ) $ 5.9 $ (9.6 ) Reclassification adjustment for net actuarial loss included in net income 7.2 (2.7 ) 4.5 Net actuarial loss (8.3 ) 3.2 (5.1 ) Prior service credit on pension and other postretirement plans: Reclassification adjustment for prior service credit included in net income (0.8 ) 0.3 (0.5 ) Net actuarial loss and prior service credit (9.1 ) 3.5 (5.6 ) Net unrealized gains and losses on securities available for sale: Net unrealized holding losses arising during the year (29.0 ) 10.7 (18.3 ) Reclassification adjustment for net realized gains included in net income 5.9 (2.2 ) 3.7 Net unrealized losses (23.1 ) 8.5 (14.6 ) 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 3.3 (1.2 ) 2.1 Net unrealized gains 3.3 (1.2 ) 2.1 Net unrealized gains and losses on derivatives accounted for as cash flow hedges: Net unrealized losses arising during the year (0.2 ) 0.1 (0.1 ) Reclassification adjustment for net realized losses included in net income 0.7 (0.3 ) 0.4 Net unrealized gains 0.5 (0.2 ) 0.3 Total other comprehensive loss $ (28.4) $ 10.6 $ (17.8 ) Pre-Tax After-Tax Year ended December 31, 2015 (in millions) Amount Tax Effect Amount Net actuarial gains and losses on pension and other postretirement plans: Net actuarial loss arising during the year $ (3.5 ) $ 1.3 $ (2.2 ) Reclassification adjustment for net actuarial loss included in net income 9.1 (3.4 ) 5.7 Net actuarial gain 5.6 (2.1 ) 3.5 Prior service credit on pension and other postretirement plans: Reclassification adjustment for prior service credit included in net income (1.0 ) 0.4 (0.6 ) Net actuarial gain and prior service credit 4.6 (1.7 ) 2.9 Net unrealized gains and losses on securities available for sale: Net unrealized holding losses arising during the year (22.1 ) 8.1 (14.0 ) Net unrealized losses (22.1 ) 8.1 (14.0 ) 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 3.1 (1.1 ) 2.0 Net unrealized gains 3.1 (1.1 ) 2.0 Net unrealized gains and losses on derivatives accounted for as cash flow hedges: Net unrealized losses arising during the year (1.1 ) 0.4 (0.7 ) Reclassification adjustment for net realized losses included in net income 1.2 (0.4 ) 0.8 Net unrealized gains 0.1 — 0.1 Total other comprehensive loss $ (14.3 ) $ 5.3 $ (9.0 ) Pre-Tax After-Tax Year ended December 31, 2014 (in millions) Amount Tax Effect Amount Net actuarial gains and losses on pension and other postretirement plans: Net actuarial loss arising during the year $ (98.5 ) $ 35.9 $ (62.6 ) Reclassification adjustment for net actuarial loss included in net income 8.4 (3.1 ) 5.3 Net actuarial loss (90.1 ) 32.8 (57.3 ) Prior service credit on pension and other postretirement plans: Reclassification adjustment for prior service credit included in net income (1.0 ) 0.4 (0.6 ) Net actuarial loss and prior service credit (91.1 ) 33.2 (57.9 ) Net unrealized gains and losses on securities available for sale: Net unrealized holding gains arising during the year 70.9 (26.3 ) 44.6 Reclassification adjustment for net realized gains included in net income (3.0 ) 1.2 (1.8 ) Net unrealized gains 67.9 (25.1 ) 42.8 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 3.0 (1.2 ) 1.8 Net unrealized gains 3.0 (1.2 ) 1.8 Net unrealized gains and losses on derivatives accounted for as cash flow hedges: Net unrealized losses arising during the year (0.9 ) 0.3 (0.6 ) Reclassification adjustment for net realized losses included in net income 1.3 (0.5 ) 0.8 Net unrealized gains 0.4 (0.2 ) 0.2 Total other comprehensive loss $ (19.8 ) $ 6.7 $ (13.1 )

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2016
Compensation and Retirement Disclosure [Abstract]
Employee Benefit Plans	NOTE 17 – 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 consecutive years of the last ten years that produce the highest average. 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 1,000 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 a qualified defined benefit pension plan that covers former Chittenden employees who meet certain eligibility requirements (the “Chittenden Qualified Plan”). Effective December 31, 2005, accrued benefits were frozen based on participants’ then-current service and pay levels. Interest continues to be credited on undistributed balances at a crediting rate specified by the Chittenden Qualified Plan. During April 2010, participants who were in payment status as of April 1, 2010, or whose accrued benefit as of that date was scheduled to be paid in the form of an annuity commencing May 1, 2010 based upon elections made by April 15, 2010, were transferred 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 “Supplemental Plans”) and (ii) an unfunded plan that provides retirees with optional medical, dental and life insurance benefits (the “Other 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. 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 an other 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 the People’s Qualified Plan, the Chittenden Qualified Plan and the Supplemental Plans (together the “Pension Plans”) and the Other Postretirement Plan. 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) 2016 2015 2016 2015 Benefit obligations: (1) Beginning of year $ 480.4 $ 515.3 $ 14.0 $ 14.6 Service cost — — 0.3 0.3 Interest cost 18.6 21.1 0.6 0.6 Actuarial loss (gain) 10.2 (36.7 ) (0.2 ) (0.6 ) Benefits paid (17.8 ) (16.6 ) (1.1 ) (0.9 ) Settlements (2.1 ) (2.7 ) — — End of year 489.3 480.4 13.6 14.0 Fair value of plan assets: Beginning of year 466.5 439.9 — — Actual return on assets 29.2 (6.4 ) — — Employer contributions (2) 2.2 52.3 1.1 0.9 Benefits paid (17.8 ) (16.6 ) (1.1 ) (0.9 ) Settlements (2.1 ) (2.7 ) — — End of year 478.0 466.5 — — Funded status at end of year $ (11.3 ) $ (13.9 ) $ (13.6 ) $ (14.0 ) Amounts recognized in the Consolidated Statements of Condition: Other assets $ 29.5 $ 26.6 $ — $ — Other liabilities (40.8 ) (40.5 ) (13.6 ) (14.0 ) Funded status at end of year $ (11.3 ) $ (13.9 ) $ (13.6 ) $ (14.0 ) (1) Represents the projected benefit obligation for the Pension Plans and the accumulated benefit obligation for the Other Postretirement Plan. (2) During the quarter ended March 31, 2015, People’s United made voluntary employer contributions of $40.0 million to the People’s Qualified Plan and $10.0 million to the Chittenden Qualified Plan. Plan assets for the People’s Qualified Plan and the Chittenden Qualified Plan (together the “Qualified Plans”) of $430.4 million and $47.6 million, respectively, as of December 31, 2016 exceeded the related projected benefit obligation ($405.5 million and $43.0 million, respectively) at that date. Although the Supplemental Plans hold no assets, People’s United has funded a trust to provide benefit payments to the extent such benefits are not paid directly by People’s United. Trust assets of $31.6 million as of December 31, 2016 (which are included in other assets in the Consolidated Statements of Condition) were exceeded by the related projected benefit obligation ($40.8 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) 2016 2015 Accumulated benefit obligations: Qualified Plans $ 448.5 $ 439.9 Supplemental Plans 40.8 40.5 Total $ 489.3 $ 480.4 Projected benefit obligations: Qualified Plans $ 448.5 $ 439.9 Supplemental Plans 40.8 40.5 Total $ 489.3 $ 480.4 Components of net periodic benefit (income) expense and other amounts recognized in other comprehensive loss are as follows: Pension Plans Other Years ended December 31 (in millions) 2016 2015 2014 2016 2015 2014 Net periodic benefit (income) expense: Service cost $ — $ — $ — $ 0.3 $ 0.3 $ 0.1 Interest cost 18.6 21.1 21.4 0.6 0.6 0.5 Expected return on plan assets (34.6 ) (34.4 ) (32.0 ) — — — Recognized net actuarial loss 6.1 7.7 5.1 0.2 0.3 — Recognized prior service credit (0.8 ) (0.8 ) (0.8 ) — (0.2 ) (0.2 ) Settlements (1) 0.8 1.2 3.3 — — — Net periodic benefit (income) expense (9.9 ) (5.2 ) (3.0 ) 1.1 1.0 0.4 Other changes in plan assets and benefit obligations recognized in other comprehensive loss: Net actuarial loss (gain) 8.7 (4.7 ) 85.3 (0.4 ) (0.9 ) 4.8 Prior service credit 0.8 0.8 0.8 — 0.2 0.2 Total pre-tax 9.5 (3.9 ) 86.1 (0.4 ) (0.7 ) 5.0 Total recognized in net periodic benefit (income) expense and other comprehensive loss $ (0.4 ) $ (9.1 ) $ 83.1 $ 0.7 $ 0.3 $ 5.4 (1) Settlement charges are a result of lump-sum pro-rata The pre-tax Pension Plans Other As of December 31 (in millions) 2016 2015 2016 2015 Net actuarial loss $ 228.0 $ 219.3 $ 3.8 $ 4.2 Prior service credit (1.2 ) (2.0 ) — — Total pre-tax $ 226.8 $ 217.3 $ 3.8 $ 4.2 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 28 years) and over the average working lifetime of active participants for the Chittenden Qualified Plan (approximately 9 years), both as of December 31, 2016. In 2017, approximately $6.5 million in net actuarial losses and $0.8 million in prior service credit are expected to be recognized as components of net periodic benefit (income) expense for the Pension Plans and approximately $0.2 million in net actuarial losses is expected to be recognized as a component of net periodic benefit (income) expense for the Other Postretirement Plan. 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 2016 2015 2014 2016 2015 2014 Weighted-average assumptions used to determine Discount rate: People’s Qualified Plan 4.41 % 4.64 % 4.20 % 4.40 % 4.60 % 4.20 % Chittenden Qualified Plan 4.16 4.45 4.00 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 periodic benefit (income) expense for the years ended December 31: Discount rate: People’s Qualified Plan 4.64 % 4.20 % 5.10 % 4.60 % 4.20 % 5.10 % Chittenden Qualified Plan 4.45 4.00 4.90 n/a n/a n/a Expected return on plan assets 7.25 7.50 8.00 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: (1) Health care cost trend rate assumed for next year n/a n/a n/a 6.50 % 6.80 % 7.05 % Rate to which the cost trend rate is assumed to decline 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 2027 2027 n/a – not applicable (1) Changes in the net periodic benefit (income) expense and the related benefit obligation arising as a result of a one-percentage-point The discount rates used to determine the benefit obligation of the Supplemental Plans at December 31, 2016 ranged from 3.60% to 4.40% while the discount rate used to determine net periodic benefit (income) expense for 2016 ranged from 3.95% to 4.60%. The discount rates used to determine the benefit obligation of the Supplemental Plans at December 31, 2015 ranged from 3.95% to 4.60% while the discount rate used to determine net periodic benefit (income) expense for 2015 was 4.20%. 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. Effective January 1, 2016, People’s United changed the method used to estimate the interest cost component of net periodic benefit income for the Pension Plans and the Other Postretirement Plan. Instead of using spot interest rate yield curves as discussed above, People’s United has elected to use a full yield curve approach to estimate this component of 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. This change is expected to improve the correlation between projected benefit cash flows and the corresponding yield curve spot rates and to provide a more precise measurement of interest cost. This change did not affect the measurement of People’s United’s total benefit obligations as the change in interest cost is completely offset by the actuarial gain or loss recognized. People’s United considers this a change in accounting estimate and, accordingly, accounted for it prospectively in 2016. The impact in 2016 of the change in accounting estimate for the Qualified Plans was as follows: (dollars in millions) People’s Chittenden Discount rates used to measure net periodic benefit income in 2016: Interest cost 4.03 % 3.70 % Discount rates that would have been used to measure net periodic benefit income Interest cost 4.64 4.45 Increase in net periodic benefit income in 2016 using specific spot rates: Interest cost $ 2.5 $ 0.3 The impact in 2016 of the change in accounting estimate for the Supplemental Plans and the Other Postretirement Plan was $0.3 million. In developing an expected long-term rate of return on asset assumption for the Qualified Plans for purposes of determining 2016 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%, which was intended to reflect expected asset returns over the life of the related pension benefits expected to be paid. In 2017, $14.3 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) an expected long-term rate of return of 7.25%; (ii) discount rates of 4.41% and 4.16% (based on the full yield curve approach discussed above) for the People’s Qualified Plan and the Chittenden Qualified Plan, respectively; and (iii) updated mortality tables issued by the Society of Actuaries in October 2016. 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. Adoption of updated mortality tables resulted in a decrease in the related benefit obligation of $6.0 million for the Qualified Plans. 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 2017, no employer contributions are expected to be made for either the People’s Qualified Plan or the Chittenden Qualified Plan. Employer contributions for the Supplemental Plans and the Other Postretirement Plan in 2017 are expected to total $8.1 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, 2016 are: $23.0 million in 2017; $20.8 million in 2018; $20.4 million in 2019; $20.3 million in 2020; $23.4 million in 2021; and an aggregate of $125.1 million in 2022 through 2026. Expected future net benefit payments for the Other Postretirement Plan as of December 31, 2016 are: $2.5 million in 2017; $2.7 million in 2018; $2.2 million in 2019; $2.6 million in 2020; $2.7 million in 2021; and an aggregate of $15.5 million in 2022 through 2026. 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 5 0-20 Equity securities 65 50-75 Fixed income securities 30 20-50 Equity securities are required to be diversified among industries and economic sectors and may include convertible securities. Limitations have been established on the overall allocation to any individual security representing more than 3% of the market value of total plan assets. A limit of 50% of equity holdings may be invested in international equities. Short sales, margin purchases and similar speculative transactions 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 “Baa” 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. Short sales, margin purchases and similar speculative transactions are prohibited. 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 2016 2015 As of December 31 People’s Chittenden People’s Chittenden Equity securities 69 % 67 % 69 % 69 % Cash and fixed income securities 31 33 31 31 Total 100 % 100 % 100 % 100 % The following tables present the Qualified Plans’ assets measured at fair value: Fair Value Measurements Using As of December 31, 2016 (in millions) Level 1 Level 2 Level 3 Total Cash and cash equivalents $ 11.7 $ — $ — $ 11.7 Equity securities: Corporate 214.8 — — 214.8 Mutual funds — 114.8 — 114.8 Fixed income securities: Corporate — 102.9 — 102.9 Mutual funds — 21.4 — 21.4 U.S. Treasury and municipals — 6.8 — 6.8 Other — 5.6 — 5.6 Total $ 226.5 $ 251.5 $ — $ 478.0 Fair Value Measurements Using As of December 31, 2015 (in millions) Level 1 Level 2 Level 3 Total Cash and cash equivalents $ 26.3 $ — $ — $ 26.3 Equity securities: Corporate 215.3 — — 215.3 Mutual funds — 105.8 — 105.8 Fixed income securities: Corporate — 81.6 — 81.6 Mutual funds — 21.8 — 21.8 Municipals — 10.5 — 10.5 Other — 5.2 — 5.2 Total $ 241.6 $ 224.9 $ — $ 466.5 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 $5.0 million in 2016, $5.1 million in 2015 and $5.3 million in 2014. At December 31, 2016, the loan balance totaled $184.9 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 1,000 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 3,484,525 shares of People’s United common stock have been allocated or committed to be released to participants’ accounts. At December 31, 2016, 6,969,050 shares of People’s United common stock, with a fair value of $134.9 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 paid-in 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 pre-tax

Stock-Based Compensation Plans

Stock-Based Compensation Plans	12 Months Ended
	Dec. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation Plans	NOTE 18 – Stock-Based Compensation Plans Long-Term Incentive Plan People’s United’s 2014 Plan and the predecessor 2008 Long-Term Incentive Plan and the 1998 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 Non-statutory People’s United has also granted restricted stock awards under the Incentive Plans. Employees become fully vested in these shares generally after a three- or four-year period, with requisite service conditions and no performance-based conditions to such vesting. Unvested restricted stock awards become fully vested in the event of a change in control, as defined in the Incentive Plans. During the vesting period, dividends are paid on the restricted stock and the recipients are entitled to vote these restricted shares. The fair value of all restricted stock awards is measured at the grant date based on quoted market prices. Beginning in 2016, People’s United 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 pre-established 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, 2015 — $ — Granted 568,596 15.22 Forfeited (15,664 ) 15.22 Vested (947 ) 15.22 Unvested performance shares outstanding at December 31, 2016 551,985 $ 15.22 Expense related to unvested performance shares is recognized on a straight-line basis, generally over the applicable service period, and totaled $2.1 million for the year ended December 31, 2016. Unamortized cost for unvested performance shares, which reflects an estimated forfeiture rate of 5% per year over the vesting period, totaled $5.3 million at December 31, 2016, and is expected to be recognized over the remaining weighted-average Following shareholder approval of the 2014 Plan in the second quarter of 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. Recognition and Retention Plan and Stock Option Plan 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 Non-statutory one-third Stock Options Granted People’s United granted a total of 3,187,500 stock options in 2016, 5,221,992 stock options in 2015 and 562,355 stock options in 2014 under the Incentive Plans and 4,391,269 stock options under the SOP in 2014. The estimated weighted-average grant-date fair value of all stock options granted in 2016, 2015 and 2014 was $1.33 per option, $1.46 per option and $1.51 per option, respectively, using the Black-Scholes option-pricing model with assumptions as follows: dividend yield of 4.6% in 2016, 4.4% in 2015 and 4.7% in 2014; expected volatility rate of 20% in both 2016 and 2015 and 22% in 2014; risk-free interest rate of 1.3% in 2016 and 1.6% in both 2015 and 2014; and expected option life of approximately 5 years in 2016, 2015 and 2014. 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 Weighted-Average Aggregate Options outstanding at December 31, 2013 14,217,074 $ 15.43 Granted 4,953,624 13.94 Forfeited (896,003 ) 15.13 Exercised (476,290 ) 12.48 Options outstanding at December 31, 2014 17,798,405 15.11 Granted 5,221,992 14.85 Forfeited (1,290,396 ) 16.57 Exercised (2,052,577 ) 13.35 Options outstanding at December 31, 2015 19,677,424 15.13 Granted 3,187,500 14.57 Forfeited (632,869 ) 15.65 Exercised (5,676,130 ) 15.60 Options outstanding at December 31, 2016 16,555,925 $ 14.84 6.4 $ 75.2 Options exercisable at December 31, 2016 8,837,386 $ 15.08 4.7 $ 38.2 (1) Reflects only those stock options with intrinsic value at December 31, 2016. Expense relating to stock options granted is recognized on a straight-line basis, generally over the applicable service period, and totaled $5.7 million, $6.8 million and $5.4 million for the years ended December 31, 2016, 2015 and 2014, respectively. Unamortized cost for unvested stock options, which reflects an estimated forfeiture rate of 5.0% per year over the vesting period, totaled $5.3 million at December 31, 2016, and is expected to be recognized over the remaining weighted-average vesting period of 1.4 years. The total intrinsic value of stock options exercised was $15.6 million, $5.1 million and $1.1 million in the years ended December 31, 2016, 2015 and 2014, respectively. Additional information concerning options outstanding and options exercisable at December 31, 2016 is summarized as follows: Options Outstanding Options Exercisable Weighted Average Exercise Price Range Number Remaining Exercise Number Weighted $11.53 – $13.05 1,717,527 5.7 $ 12.85 1,717,527 $ 12.85 13.42 – 15.80 12,425,506 7.6 14.51 4,706,967 14.42 16.07 – 17.76 734,089 1.8 16.85 734,089 16.85 18.10 – 21.63 1,678,803 0.8 18.45 1,678,803 18.45 Restricted Stock Awarded The following is a summary of restricted stock award activity under the Incentive Plans and the RRP: Shares Weighted-Average Fair Value Unvested restricted shares outstanding at December 31, 2013 1,533,215 $ 13.12 Granted 660,617 14.01 Forfeited (95,700 ) 13.53 Vested (730,600 ) 13.22 Unvested restricted shares outstanding at December 31, 2014 1,367,532 13.47 Granted 568,273 14.88 Forfeited (80,303 ) 14.23 Vested (623,185 ) 13.33 Unvested restricted shares outstanding at December 31, 2015 1,232,317 14.14 Granted 344,812 14.66 Forfeited (41,684 ) 14.34 Vested (649,363 ) 13.79 Unvested restricted shares outstanding at December 31, 2016 886,082 $ 14.59 Expense relating to unvested restricted stock awards is recognized on a straight-line basis, generally over the applicable service period, and totaled $6.5 million, $9.4 million and $8.7 million for the years ended December 31, 2016, 2015 and 2014, respectively. Unamortized cost for unvested restricted stock awards, which reflects an estimated forfeiture rate of 5.0% per year over the vesting period, totaled $6.4 million at December 31, 2016, and is expected to be recognized over the remaining weighted-average vesting period of 1.3 years. The total fair value of restricted stock awards vested during the years ended December 31, 2016, 2015 and 2014 was $9.8 million, $9.4 million and $10.3 million, respectively. During 2016, 2015 and 2014, employees of People’s United tendered a total of 289,992 shares, 230,459 shares and 229,635 shares of common stock, respectively, in satisfaction of their related minimum 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 minimum 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 minimum 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, 2016, 2015 and 2014 was $3.4 million, $3.2 million and $3.0 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 one-year In 2016, 2015 and 2014, directors were granted a total of 58,020 shares, 62,690 shares and 57,330 shares, respectively, of People’s United common stock, with grant date fair values of $16.24 per share, $15.23 per share and $14.63 per share, respectively, at those dates. Expense totaling $0.9 million, $0.9 million and $0.8 million was recognized for the years ended December 31, 2016, 2015 and 2014, respectively, for the Directors’ Plan. At December 31, 2016, a total of 193,051 shares remain available for issuance.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Fair Value Measurements	NOTE 19 – 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 Recurring Fair Value Measurements Trading Account Securities and 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 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, GSE mortgage-backed securities and CMOs, all of which are included in Level 2. The Company’s available-for-sale available-for-sale 10- 15-year 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 10- 15-year Other Assets As discussed in Note 17, 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, 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, 2016 (in millions) Level 1 Level 2 Level 3 Total Financial assets: Trading account securities: U.S. Treasury $ 6.8 $ — $ — $ 6.8 Securities available for sale: U.S. Treasury and agency 859.7 — — 859.7 GSE mortgage-backed securities and CMOs — 3,550.0 — 3,550.0 Equity securities — 0.2 — 0.2 Other assets: Exchange-traded funds 32.6 — — 32.6 Fixed income securities — 4.3 — 4.3 Mutual funds 2.7 — — 2.7 Interest rate swaps — 173.1 — 173.1 Foreign exchange contracts — 0.6 — 0.6 Forward commitments to sell residential mortgage loans — 0.3 — 0.3 Total $ 901.8 $ 3,728.5 $ — $ 4,630.3 Financial liabilities: Interest rate swaps $ — $ 121.0 $ — $ 121.0 Risk participation agreements (1) — — — — Foreign exchange contracts — 0.3 — 0.3 Interest rate-lock commitments on residential mortgage loans — 0.4 — 0.4 Total $ — $ 121.7 $ — $ 121.7 Fair Value Measurements Using As of December 31, 2015 (in millions) Level 1 Level 2 Level 3 Total Financial assets: Trading account securities: U.S. Treasury $ 6.7 $ — $ — $ 6.7 Securities available for sale: U.S. Treasury and agency 362.8 — — 362.8 GSE residential mortgage-backed securities and CMOs — 4,164.7 — 4,164.7 Equity securities — 0.2 — 0.2 Other assets: Exchange-traded funds 29.4 — — 29.4 Fixed income securities — 5.1 — 5.1 Mutual funds 2.0 — — 2.0 Interest rate swaps — 157.0 — 157.0 Foreign exchange contracts — 0.6 — 0.6 Forward commitments to sell residential mortgage loans — 0.6 — 0.6 Total $ 400.9 $ 4,328.2 $ — $ 4,729.1 Financial liabilities: Interest rate swaps $ — $ 108.5 $ — $ 108.5 Risk participation agreements (1) — — — — Foreign exchange contracts — 0.2 — 0.2 Interest rate-lock commitments on residential mortgage loans — 0.8 — 0.8 Total $ — $ 109.5 $ — $ 109.5 (1) As of December 31, 2016 and 2015, the fair value of risk participation agreements totaled less than $0.1 million (see Note 21). There were no transfers into or out of the Level 1 or Level 2 categories during the years ended December 31, 2016 and 2015. Non-Recurring Loans Held for Sale Residential mortgage 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 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: the present value of expected future cash flows discounted at the loan’s original effective interest rate; the loan’s observable market price; or 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 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 The following tables summarize People’s United’s assets that are measured at fair value on a non-recurring Fair Value Measurements Using As of December 31, 2016 (in millions) Level 1 Level 2 Level 3 Total Loans held for sale (1) $ — $ 39.3 $ — $ 39.3 Impaired loans (2) — — 55.9 55.9 REO and repossessed assets (3) — — 19.3 19.3 Total $ — $ 39.3 $ 75.2 $ 114.5 Fair Value Measurements Using As of December 31, 2015 (in millions) Level 1 Level 2 Level 3 Total Loans held for sale (1) $ — $ 34.5 $ — $ 34.5 Impaired loans (2) — — 49.1 49.1 REO and repossessed assets (3) — — 22.1 22.1 Total $ — $ 34.5 $ 71.2 $ 105.7 (1) Consists of residential mortgage loans; no fair value adjustments were recorded for the years ended December 31, 2016 and 2015. (2) 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 $40.8 million of Commercial loans and $15.1 million of Retail loans at December 31, 2016. The provision for loan losses on impaired loans totaled $3.8 million and $6.7 million for the years ended December 31, 2016 and 2015, respectively. (3) Represents: (i) $8.1 million of residential REO; (ii) $4.0 million of commercial REO; and (iii) $7.2 million of repossessed assets at December 31, 2016. Charge-offs to the allowance for loan losses related to loans that were transferred to REO or repossessed assets totaled $3.7 million and $1.8 million for the years ended December 31, 2016 and 2015, respectively. Write downs and net loss on sale of foreclosed/repossessed assets charged to non-interest Financial Assets and Financial Liabilities Not Measured At Fair Value As discussed in Note 1, 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 (an “exit price” approach to fair value). Acceptable valuation techniques (when quoted market prices are not available) that might be used to estimate the fair value of financial instruments include discounted cash flow analyses and comparison to similar instruments. Such estimates are highly subjective and require judgments regarding significant matters such as the amount and timing of future cash flows and the selection of discount rates that appropriately reflect market and credit risks. Changes in these judgments often have a material impact on the fair value estimates. In addition, since these estimates are made as of a specific point in time, they are susceptible to material near-term changes. Fair values estimated in this manner do not reflect any premium or discount that could result from the sale of a large volume of a particular financial instrument, nor do they reflect possible tax ramifications or estimated transaction costs. The following is a description of the principal valuation methods used by People’s United for those financial instruments that are not measured at fair value either on a recurring or non-recurring Cash, Short-Term Investments and Securities Purchased Under Agreements to Resell Cash and due from banks are classified as Level 1. Short-term investments and securities purchased under agreements to resell have fair values that approximate the respective carrying amounts because the instruments are payable on demand or have short-term maturities, and present relatively low credit risk and IRR. As such, these fair values are classified as Level 2. Securities Held to Maturity When available, the fair values of investment securities held to maturity are measured based on quoted market prices for identical securities in active markets and, accordingly, are classified as Level 1 assets. When quoted market prices for identical securities are not available, fair values are estimated based on quoted prices for similar assets in active markets or through the use of pricing models containing observable inputs (i.e. market interest rates, financial information and credit ratings of the issuer, etc.). These fair values are included in Level 2. In cases where there may be limited information available and/or little or no market activity for the underlying security, fair value is estimated using pricing models containing unobservable inputs and classified as Level 3. FHLB and FRB-NY Both FHLB and FRB-NY non-marketable Loans For valuation purposes, the loan portfolio is segregated into its significant categories, which are commercial real estate, commercial and industrial, equipment financing, residential mortgage, home equity and other consumer. These categories are further segregated, where appropriate, into components based on significant financial characteristics such as type of interest rate (fixed or adjustable) and payment status (performing or non-performing). The fair values of performing loans were estimated by discounting the anticipated cash flows from the respective portfolios, assuming future prepayments and using market interest rates for new loans with comparable credit risk. As a result, the valuation method for performing loans, which is consistent with certain guidance provided in accounting standards, does not fully incorporate the “exit price” approach to fair value. The fair values of non-performing Deposit Liabilities The fair values of time deposits represent contractual cash flows discounted at current rates determined by reference to observable inputs including a LIBOR/swap curve over the remaining period to maturity. As such, these fair values are classified as Level 2. The fair values of other deposit liabilities (those with no stated maturity, such as checking and savings accounts) are equal to the carrying amounts payable on demand. Deposit fair values do not include the intangible value of core deposit relationships that comprise a significant portion of People’s United’s deposit base. Management believes that People’s United’s core deposit relationships provide a relatively stable, low-cost Borrowings and Notes and Debentures The fair values of federal funds purchased, repurchase agreements and other borrowings are equal to the carrying amounts due to the short maturities (generally overnight). The fair values of FHLB advances represent contractual repayments discounted using interest rates currently available on borrowings with similar characteristics and remaining maturities and are classified as Level 2. The fair values of notes and debentures were based on dealer quotes and are classified as Level 2. Lending-Related Financial Instruments The estimated fair values of People’s United’s lending-related financial instruments approximate the respective carrying amounts. Such instruments include commitments to extend credit, unadvanced lines of credit and letters of credit, for which fair values were estimated based on an analysis of the interest rates and fees currently charged to enter into similar transactions, considering the remaining terms of the instruments and the creditworthiness of the potential borrowers. 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 Carrying Amount Estimated Fair Value As of December 31, 2016 (in millions) Level 1 Level 2 Level 3 Total Financial assets: Cash and due from banks $ 432.4 $ 432.4 $ — $ — $ 432.4 Short-term investments 181.7 — 181.7 — 181.7 Securities held to maturity 2,005.4 — 2,011.2 1.5 2,012.7 FHLB and FRB stock 315.8 — 315.8 — 315.8 Total loans, net (1) 29,459.7 — 6,028.4 23,238.1 29,266.5 Financial liabilities: Time deposits 4,542.2 — 4,539.7 — 4,539.7 Other deposits 25,318.6 — 25,318.6 — 25,318.6 FHLB advances 3,061.1 — 3,064.4 — 3,064.4 Federal funds purchased 617.0 — 617.0 — 617.0 Customer repurchase agreements 343.3 — 343.3 — 343.3 Other borrowings 35.4 — 35.4 — 35.4 Notes and debentures 1,030.1 — 1,000.0 — 1,000.0 (1) Excludes impaired loans totaling $55.9 million measured at fair value on a non-recurring Carrying Amount Estimated Fair Value As of December 31, 2015 (in millions) Level 1 Level 2 Level 3 Total Financial assets: Cash and due from banks $ 334.8 $ 334.8 $ — $ — $ 334.8 Short-term investments 380.5 — 380.5 — 380.5 Securities held to maturity 1,609.6 — 1,661.0 1.5 1,662.5 FHLB and FRB stock 305.4 — 305.4 — 305.4 Total loans, net (1) 28,150.8 — 5,315.3 22,893.7 28,209.0 Financial liabilities: Time deposits 4,818.1 — 4,836.5 — 4,836.5 Other deposits 23,599.3 — 23,599.3 — 23,599.3 FHLB advances 3,463.8 — 3,468.7 — 3,468.7 Customer repurchase agreements 469.5 — 469.5 — 469.5 Federal funds purchased 374.0 — 374.0 — 374.0 Notes and debentures 1,033.1 — 1,012.9 — 1,012.9 (1) Excludes impaired loans totaling $49.1 million measured at fair value on a non-recurring

Legal Proceedings and Lease Com

Legal Proceedings and Lease Commitments	12 Months Ended
	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Legal Proceedings and Lease Commitments	NOTE 20 – Legal Proceedings and Lease Commitments People’s United has various outstanding commitments and contingent liabilities that are not required to be and, therefore, have not been reflected in the consolidated financial statements. 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. Lease Commitments At December 31, 2016, People’s United was obligated under various noncancelable operating leases for office space, which expire on various dates through 2054. Certain leases contain renewal options and provide for increased rentals based principally on the consumer price index and fair market rental value provisions. Future minimum rental commitments under operating leases in excess of one year at December 31, 2016 were: $58.8 million in 2017; $54.3 million in 2018; $49.5 million in 2019; $45.6 million in 2020; $42.5 million in 2021; and an aggregate of $106.6 million in 2022 through 2054. Rent expense under operating leases included in occupancy and equipment in the Consolidated Statements of Income totaled $59.8 million, $58.9 million and $59.1 million for the years ended December 31, 2016, 2015 and 2014, respectively.

Financial Instruments

Financial Instruments	12 Months Ended
	Dec. 31, 2016
Investments, All Other Investments [Abstract]
Financial Instruments	NOTE 21 – Financial Instruments In the normal course of business, People’s United is a party to both on-balance-sheet off-balance-sheet off-balance-sheet 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) 2016 2015 Lending-Related Financial Instruments: (1) Loan origination commitments and unadvanced lines of credit: Commercial and industrial $ 4,029.6 $ 3,337.0 Home equity and other consumer 2,800.7 2,558.4 Commercial real estate 701.6 831.0 Equipment financing 179.9 241.0 Residential mortgage 69.6 93.3 Letters of credit: Stand-by 105.6 121.5 Commercial 3.6 3.4 Derivative Financial Instruments: (2) Interest rate swaps: For market risk management 500.0 500.0 For commercial customers: Customer 5,612.2 4,644.8 Institutional counterparties 5,620.2 4,644.8 Risk participation agreements 251.9 244.4 Foreign exchange contracts 101.2 56.7 Forward commitments to sell residential mortgage loans 48.6 44.7 Interest rate-lock commitments on residential mortgage loans 57.0 65.4 (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 Stand-by stand-by 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 $2.3 million and $2.5 million at December 31, 2016 and 2015, 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, 2016 was $7.5 million, for which People’s United had posted collateral of $5.4 million in the normal course of business. If the Company’s senior unsecured debt rating had fallen below investment grade as of that date, $2.1 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. People’s United has entered into a pay fixed/receive floating interest rate swap to hedge the LIBOR-based floating rate payments on the Company’s $125 million subordinated notes (see Note 11) (such payments began in February 2012). These notes had a fixed interest rate of 5.80% until February 2012, at which time the interest rate converted to the three-month LIBOR plus 68.5 basis points. People’s United has agreed with the swap counterparty to exchange, at specified intervals, the difference between fixed-rate (1.99%) and floating-rate interest amounts calculated based on a notional amount of $125 million. The floating-rate interest amounts received under the swap are calculated using the same floating-rate paid on these notes. The swap effectively converts the variable-rate subordinated notes to a fixed-rate liability and consequently reduces People’s United’s exposure to increases in interest rates. This swap is accounted for as a cash flow hedge (see Note 25). The Bank has entered into a pay floating/receive fixed interest rate swap to hedge the change in fair value of the Bank’s $400 million subordinated notes (see Note 11) due to changes in interest rates. 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 with certain of its commercial customers. In order to minimize its risk, these customer derivatives (pay floating/receive fixed swaps) have been offset with essentially matching interest rate swaps with People’s United’s institutional counterparties (pay fixed/receive floating swaps). Hedge accounting has not been applied for these derivatives. Accordingly, changes in the fair value of all such interest rate swaps 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 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 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”) 10-year T-Locks net-of-tax ten-year 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 Hedge Notional Amounts Assets Liabilities As of December 31 (in millions) 2016 2015 2016 2015 2016 2015 Derivatives Not Designated as Hedging Interest rate swaps: Commercial customers N/A $ 5,612.2 $ 4,644.8 $ 93.9 $ 130.9 $ 46.9 $ 2.6 Institutional counterparties N/A 5,620.2 4,644.8 65.6 7.2 74.0 105.3 Risk participation agreements (2) N/A 251.9 244.4 — — — — Foreign exchange contracts N/A 101.2 56.7 0.6 0.6 0.3 0.2 Forward commitments to sell residential mortgage loans N/A 48.6 44.7 0.3 0.6 — — Interest rate-lock commitments on residential mortgage loans N/A 57.0 65.4 — — 0.4 0.8 Total 160.4 139.3 121.6 108.9 Derivatives Designated as Hedging Instruments: Interest rate swaps: Subordinated notes Cash flow 125.0 125.0 — — 0.1 0.6 Subordinated notes Fair value 375.0 375.0 13.6 18.9 — — Total 13.6 18.9 0.1 0.6 Total fair value of derivatives $ 174.0 $ 158.2 $ 121.7 $ 109.5 (1) Assets are recorded in other assets and liabilities are recorded in other liabilities. (2) Fair value totaled less than $0.1 million at both dates. The following table summarizes the impact of People’s United’s derivatives on pre-tax Amount of Pre-Tax Amount of Pre-Tax Type of Hedge Recognized in Earnings (1) Recognized in AOCL Years ended December 31 (in millions) 2016 2015 2014 2016 2015 2014 Derivatives Not Designated as Hedging Instruments: Interest rate swaps: Commercial customers N/A $ (11.1 ) $ 104.8 $ 165.4 $ — $ — $ — Institutional counterparties N/A 24.8 (90.3 ) (156.9 ) — — — Foreign exchange contracts N/A (0.6 ) 0.2 0.4 — — — Risk participation agreements N/A 0.5 (0.2 ) 0.1 — — — Forward commitments to sell residential mortgage loans N/A (0.2 ) 0.1 0.4 — — — Interest rate-lock commitments on residential mortgage loans N/A 0.3 (0.1 ) (0.5 ) — — — Total 13.7 14.5 8.9 — — — Derivatives Designated as Hedging Instruments: Interest rate swaps Cash flow (0.8 ) (1.3 ) (1.4 ) (0.2 ) (1.1 ) (0.9 ) Interest rate locks Cash flow 0.1 0.1 0.1 — — — Interest rate swaps Fair value 7.5 9.3 5.2 — — — Total 6.8 8.1 3.9 (0.2 ) (1.1 ) (0.9 ) Total $ 20.5 $ 22.6 $ 12.8 $ (0.2 ) $ (1.1 ) $ (0.9 ) (1) Amounts recognized in earnings are recorded in interest income, interest expense or other non-interest non-interest

Balance Sheet Offsetting

Balance Sheet Offsetting	12 Months Ended
	Dec. 31, 2016
Text Block [Abstract]
Balance Sheet Offsetting	NOTE 22 – Balance Sheet Offsetting 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. The net amounts of the derivative assets and liabilities can be reconciled to the fair value of the Company’s derivative financial instruments in Note 21. 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 Amount Gross Amount Net Amount Gross Amounts Not Offset As of December 31, 2016 (in millions) Financial Collateral Net Amount Financial assets: Interest rate swaps: Counterparty A $ 1.9 $ — $ 1.9 $ (1.9 ) $ — $ — Counterparty B 1.0 — 1.0 (1.0 ) — — Counterparty C 1.7 — 1.7 (1.7 ) — — Counterparty D 3.4 — 3.4 (3.4 ) — — Counterparty E 69.6 — 69.6 (50.0 ) (19.6 ) — Other counterparties 1.6 — 1.6 (0.3 ) (1.3 ) — Foreign exchange contracts 0.6 — 0.6 — — 0.6 Total $ 79.8 $ — $ 79.8 $ (58.3 ) $ (20.9 ) $ 0.6 Financial liabilities: Interest rate swaps: Counterparty A $ 4.3 $ — $ 4.3 $ (1.9 ) $ (2.4 ) $ — Counterparty B 7.7 — 7.7 (1.0 ) (6.7 ) — Counterparty C 3.4 — 3.4 (1.7 ) (1.1 ) 0.6 Counterparty D 6.9 — 6.9 (3.4 ) (1.7 ) 1.8 Counterparty E 50.0 — 50.0 (50.0 ) — — Other counterparties 1.8 — 1.8 (0.3 ) (1.5 ) — Foreign exchange contracts 0.3 — 0.3 — — 0.3 Total $ 74.4 $ — $ 74.4 $ (58.3 ) $ (13.4 ) $ 2.7 Gross Amount Gross Amount Net Amount Gross Amounts Not Offset As of December 31, 2015 (in millions) Financial Collateral Net Amount Financial assets: Interest rate swaps: Counterparty A $ 0.6 $ — $ 0.6 $ (0.6 ) $ — $ — Counterparty B 0.7 — 0.7 (0.7 ) — — Counterparty C 0.6 — 0.6 (0.6 ) — — Counterparty D 0.7 — 0.7 (0.7 ) — — Counterparty E 22.6 — 22.6 (22.6 ) — — Other counterparties 0.8 — 0.8 (0.7 ) — 0.1 Foreign exchange contracts 0.6 — 0.6 — — 0.6 Total $ 26.6 $ — $ 26.6 $ (25.9 ) $ — $ 0.7 Financial liabilities: Interest rate swaps: Counterparty A $ 8.4 $ — $ 8.4 $ (0.6 ) $ (7.8 ) $ — Counterparty B 10.4 — 10.4 (0.7 ) (9.7 ) — Counterparty C 5.1 — 5.1 (0.6 ) (4.5 ) — Counterparty D 8.9 — 8.9 (0.7 ) (7.3 ) 0.9 Counterparty E 69.5 — 69.5 (22.6 ) (46.9 ) — Other counterparties 3.6 — 3.6 (0.7 ) (2.9 ) — Foreign exchange contracts 0.2 — 0.2 — — 0.2 Total $ 106.1 $ — $ 106.1 $ (25.9 ) $ (79.1 ) $ 1.1

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2016
Segment Reporting [Abstract]
Segment Information	NOTE 23 – 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 Retail Banking non-institutional 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 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 During the quarter ended March 31, 2015, the Company modified its FTP methodology relating to certain deposit products that resulted in a reduction in the funding credit recognized within net interest income for Commercial Banking and Retail Banking, with the offset reflected in Treasury. Prior period segment results have not been adjusted and continue to reflect the previous FTP methodology. A five-year rolling average net charge-off year-to-year People’s United allocates a majority of non-interest full-absorption non-interest 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 certain gains totaling $7.5 million, $9.2 million and $20.6 million for the years ended December 31, 2016, 2015 and 2014, respectively (included in total non-interest non-interest The following tables provide selected financial information for People’s United’s reportable segments: Year ended December 31, 2016 (in millions) Commercial Retail Total Treasury Other Total Net interest income (loss) $ 566.5 $ 347.5 $ 914.0 $ 87.6 $ (29.4 ) $ 972.2 Provision for loan losses 39.3 13.0 52.3 — (15.7 ) 36.6 Total non-interest 156.4 169.0 325.4 9.2 8.1 342.7 Total non-interest 322.8 508.9 831.7 9.8 27.3 868.8 Income (loss) before income tax expense (benefit) 360.8 (5.4 ) 355.4 87.0 (32.9 ) 409.5 Income tax expense (benefit) 113.4 (1.7 ) 111.7 27.5 (10.7 ) 128.5 Net income (loss) $ 247.4 $ (3.7 ) $ 243.7 $ 59.5 $ (22.2 ) $ 281.0 Average total assets $ 22,691.1 $ 8,945.8 $ 31,636.9 $ 7,443.1 $ 704.3 $ 39,784.3 Average total liabilities 6,733.7 19,207.3 25,941.0 8,628.7 355.2 34,924.9 Year ended December 31, 2015 (in millions) Commercial Retail Total Treasury Other Total Net interest income (loss) $ 551.6 $ 344.6 $ 896.2 $ 64.4 $ (28.5 ) $ 932.1 Provision for loan losses 47.7 15.2 62.9 — (29.5 ) 33.4 Total non-interest 162.0 169.7 331.7 11.1 9.6 352.4 Total non-interest 313.2 520.2 833.4 6.9 20.3 860.6 Income (loss) before income tax expense (benefit) 352.7 (21.1 ) 331.6 68.6 (9.7 ) 390.5 Income tax expense (benefit) 117.9 (7.0 ) 110.9 22.9 (3.4 ) 130.4 Net income (loss) $ 234.8 $ (14.1 ) $ 220.7 $ 45.7 $ (6.3 ) $ 260.1 Average total assets $ 21,465.7 $ 8,478.1 $ 29,943.8 $ 6,399.3 $ 583.8 $ 36,926.9 Average total liabilities 5,483.2 19,235.8 24,719.0 7,188.4 322.2 32,229.6 Year ended December 31, 2014 (in millions) Commercial Retail Total Treasury Other Total Net interest income (loss) $ 516.0 $ 408.0 $ 924.0 $ 10.7 $ (22.8 ) $ 911.9 Provision for loan losses 47.6 16.8 64.4 — (23.8 ) 40.6 Total non-interest 141.4 167.4 308.8 12.4 29.6 350.8 Total non-interest 275.7 528.0 803.7 6.2 31.6 841.5 Income (loss) before income tax expense (benefit) 334.1 30.6 364.7 16.9 (1.0 ) 380.6 Income tax expense (benefit) 113.1 10.3 123.4 5.8 (0.3 ) 128.9 Net income (loss) $ 221.0 $ 20.3 $ 241.3 $ 11.1 $ (0.7 ) $ 251.7 Average total assets $ 19,338.5 $ 8,514.8 $ 27,853.3 $ 5,261.2 $ 652.6 $ 33,767.1 Average total liabilities 4,275.1 19,109.2 23,384.3 5,418.0 339.4 29,141.7

Parent Company Financial Inform

Parent Company Financial Information	12 Months Ended
	Dec. 31, 2016
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Parent Company Financial Information	NOTE 24 – 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) 2016 2015 Assets: Cash at bank subsidiary $ 308.7 $ 170.2 Total cash and cash equivalents 308.7 170.2 Securities available for sale, at fair value 75.3 201.4 Advances to bank subsidiary — 100.0 Investments in subsidiaries: Bank subsidiary 5,119.2 4,649.2 Non-bank 0.9 0.8 Goodwill 197.1 197.1 Due from bank subsidiary 36.5 8.1 Other assets 29.9 28.4 Total assets $ 5,767.6 $ 5,355.2 Liabilities and Stockholders’ Equity: Notes and debentures $ 621.5 $ 619.7 Other liabilities 4.2 3.9 Stockholders’ equity 5,141.9 4,731.6 Total liabilities and stockholders’ equity $ 5,767.6 $ 5,355.2 CONDENSED STATEMENTS OF INCOME Years ended December 31 (in millions) 2016 2015 2014 Revenues: Interest income: Securities $ 3.4 $ 1.1 $ 0.4 Advances to bank subsidiary 1.0 4.4 4.4 Total interest income 4.4 5.5 4.8 Dividend from bank subsidiary 271.0 245.0 244.0 Security gain — — 2.3 Other non-interest 14.8 4.2 1.2 Total revenues 290.2 254.7 252.3 Expenses: Interest on notes and debentures 22.5 22.5 22.4 Non-interest 9.6 2.8 6.1 Total expenses 32.1 25.3 28.5 Income before income tax benefit and 258.1 229.4 223.8 Income tax benefit (5.0 ) (5.5 ) (6.6 ) Income before subsidiaries undistributed income 263.1 234.9 230.4 Subsidiaries undistributed income 17.9 25.2 21.3 Net income $ 281.0 $ 260.1 $ 251.7 CONDENSED STATEMENTS OF COMPREHENSIVE INCOME Years ended December 31 (in millions) 2016 2015 2014 Net income $ 281.0 $ 260.1 $ 251.7 Other comprehensive loss, net of tax: Net unrealized losses on securities available for sale (0.1 ) (0.3 ) — Net unrealized gains on derivatives accounted for 0.3 0.1 0.2 Other comprehensive loss of bank subsidiary (18.0 ) (8.8 ) (13.3 ) Total other comprehensive loss, net of tax (17.8 ) (9.0 ) (13.1 ) Total comprehensive income $ 263.2 $ 251.1 $ 238.6 CONDENSED STATEMENTS OF CASH FLOWS Years ended December 31 (in millions) 2016 2015 2014 Cash Flows from Operating Activities: Net income $ 281.0 $ 260.1 $ 251.7 Adjustments to reconcile net income to net cash provided Subsidiaries undistributed income (17.9 ) (25.2 ) (21.3 ) Security gain — — (2.3 ) Net change in other assets and other liabilities (21.5 ) (0.4 ) 0.2 Net cash provided by operating activities 241.6 234.5 228.3 Cash Flows from Investing Activities: Proceeds from principal repayments and maturities 1.4 1.2 — Proceeds from sales of securities available for sale 200.4 — 5.0 Purchases of securities available for sale (76.0 ) (202.9 ) — Increase in investment in bank subsidiary (450.0 ) — — Decrease (increase) in advances to bank subsidiary 100.0 310.0 (57.0 ) Net cash (used in) provided by investing activities (224.2 ) 108.3 (52.0 ) Cash Flows from Financing Activities: Proceeds from issuance of preferred stock, net 244.1 — — Cash dividends paid on common stock (205.7 ) (201.2 ) (196.9 ) Cash dividend paid on preferred stock (1.8 ) — — Common stock repurchases (3.4 ) (3.2 ) (3.0 ) Proceeds from stock options exercised, including 87.9 27.5 6.0 Net cash provided by (used in) financing activities 121.1 (176.9 ) (193.9 ) Net increase (decrease) in cash and cash equivalents 138.5 165.9 (17.6 ) Cash and cash equivalents at beginning of year 170.2 4.3 21.9 Cash and cash equivalents at end of year $ 308.7 $ 170.2 $ 4.3

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2016
Subsequent Events [Abstract]
Subsequent Events	NOTE 25 – Subsequent Events Pending Acquisition On June 27, 2016, People’s United announced the signing of a definitive agreement to acquire Suffolk Bancorp (“Suffolk”) based in Riverhead, New York. Under the terms of the definitive agreement, each share of Suffolk common stock will be converted into the right to receive 2.225 shares of People’s United common stock, with a total transaction value, as of December 31, 2016, of approximately $518 million. As disclosed in its Quarterly Report on Form 10-Q as of and for the period ended September 30, 2016, Suffolk reported total assets of $2.2 billion, total deposits of $1.9 billion and operated 27 branches in the greater Long Island area. The acquisition, which is subject to regulatory approval, was approved by the shareholders of Suffolk on October 13, 2016. People’s United shareholder approval is not required for the acquisition. On February 6, 2017, the Company announced that the OCC approved the merger of Suffolk County National Bank with and into the Bank. The acquisition remains subject to the approval of the FRB. Merger-related expenses recorded in 2016 relating to this transaction totaled $2.8 million. Repayment of Subordinated Notes On February 14, 2017, the Company repaid the $125 million 5.80% fixed-rate/floating-rate subordinated notes (see Note 11). Concurrent with the repayment, the interest rate swap designated to these subordinated notes matured (see Note 21).

Selected Quarterly Financial Da

Selected Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Financial Data (Unaudited)	NOTE 26 – Selected Quarterly Financial Data (Unaudited) The following table presents People’s United’s quarterly financial data for 2016 and 2015: 2016 2015 (dollars in millions, except per share data) First Second Third Fourth First Second Third Fourth Interest and dividend income $ 278.0 $ 278.5 $ 284.5 $ 286.3 $ 260.3 $ 264.5 $ 269.9 $ 274.2 Interest expense 37.9 38.5 39.2 39.5 32.2 34.1 35.1 35.4 Net interest income 240.1 240.0 245.3 246.8 228.1 230.4 234.8 238.8 Provision for loan losses 10.5 10.0 8.4 7.7 9.8 7.7 6.2 9.7 Net interest income after provision for loan losses 229.6 230.0 236.9 239.1 218.3 222.7 228.6 229.1 Non-interest 82.3 85.4 90.8 84.2 89.0 83.0 87.1 93.3 Non-interest 217.3 212.9 221.4 217.2 217.6 211.8 214.2 217.0 Income before income tax expense 94.6 102.5 106.3 106.1 89.7 93.9 101.5 105.4 Income tax expense 31.7 34.0 32.6 30.2 30.5 32.2 33.1 34.6 Net income 62.9 68.5 73.7 75.9 59.2 61.7 68.4 70.8 Preferred stock dividend — — — 1.8 — — — — Net income available to common shareholders $ 62.9 $ 68.5 $ 73.7 $ 74.1 $ 59.2 $ 61.7 $ 68.4 $ 70.8 Common Share Data: Basic EPS $ 0.21 $ 0.23 $ 0.24 $ 0.24 $ 0.20 $ 0.20 $ 0.23 $ 0.23 Diluted EPS 0.21 0.23 0.24 0.24 0.20 0.20 0.23 0.23 Common dividends paid 50.6 51.7 51.7 51.7 49.5 50.5 50.6 50.6 Dividends paid per common share 0.1675 0.17 0.17 0.17 0.165 0.1675 0.1675 0.1675 Common dividend payout ratio 80.6 % 75.4 % 70.1 % 69.8 % 83.7 % 81.8 % 73.9 % 71.5 % Stock price: High $ 16.27 $ 16.68 $ 16.40 $ 20.13 $ 15.45 $ 16.64 $ 16.95 $ 16.93 Low 13.62 13.80 14.22 15.28 13.97 14.92 14.69 15.00 Weighted average common shares outstanding (in millions): Basic 301.86 302.48 302.88 305.17 299.15 300.09 301.00 301.38 Diluted 301.86 302.48 303.24 306.23 299.15 300.09 301.00 301.38

Summary of Significant Accoun35

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Basis of Financial Statement Presentation	Basis of Financial Statement Presentation The 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. Certain reclassifications have been made to prior year amounts to conform to the current year presentation. 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”);
Securities	Securities Marketable equity and debt securities (other than those reported as short-term investments) are classified as either trading account securities, held to maturity securities (applicable only to debt securities) or available for sale securities. Management determines the classification of a security at the time of its purchase and reevaluates such classification at each balance sheet date. 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 account securities and reported at fair value with unrealized gains and losses reported in non-interest 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 securities are classified as available for sale and reported at fair value with unrealized gains and losses reported on an after-tax Security transactions are recorded on the trade date. Realized gains and losses are determined using the specific identification method and reported in non-interest Securities transferred from available for sale to held to maturity are recorded at fair value at the date of transfer. The unrealized pre-tax Management conducts a periodic review and evaluation of the 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 non-marketable FRB-NY
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 non-interest
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 A loan is generally considered “non-performing” non-accrual non-accrual non-accrual All previously accrued but unpaid interest on non-accrual non-accrual non-accrual
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 originated loans whose terms have been modified in such a way that they are considered troubled debt restructurings (“TDRs”). Originated 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 non-performing non-accrual non-performing Impairment is evaluated on a collective basis for smaller-balance loans with similar credit risk and on an individual loan 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 Acquired Loans Acquired loans that have evidence of deterioration in credit quality since origination and for which it is probable, at acquisition, that all contractually required payments will not be collected are initially recorded at fair value without recording an 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 Under the accounting model for acquired 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 effective yield method. Accordingly, acquired loans are not subject to classification as non-accrual 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 • Changes in prepayment assumptions • Changes in interest rate indices for variable rate loans 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. An acquired loan 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 re-assessment Allowance and Provision for Loan Losses 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 The Company’s allowance for loan losses consists of three elements: (i) an allowance for larger-balance, non-homogeneous (loan-by-loan) smaller-balance, Larger-balance, Non-homogeneous larger-balance, non-homogeneous charge-off In establishing the allowance for loan losses for larger-balance, non-homogeneous Smaller-balance, Homogeneous Loans. The qualitative component of the allowance for loan losses for smaller-balance, homogenous loans 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 Portfolio-specific risk characteristics include, but are not limited to: (i) collateral values/loan-to non-stated non-owner In establishing the allowance for loan losses for smaller-balance, homogeneous loans, 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 Individually Impaired Loans. non-accrual charge-off charge-off 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 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 commercial real estate portfolios. People’s United did not change its methodologies with respect to determining the allowance for loan losses during 2016. 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, 2016. 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. Loan Charge-Offs The Company’s charge-off charged-off 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 The decision whether to charge-off charge-off
Wealth Management and Other Fee-Based Revenues	Wealth Management and Other Fee-Based Investment management fees are accrued when earned based on total assets managed and administered, which are not reported as assets of People’s United. Insurance revenue represents commissions earned solely from performing broker- and agency-related services. Insurance commission revenues related to agency-billed policies are recognized at the later of the policy billing date or the policy effective date. Insurance commission revenues on premiums directly billed by insurance carriers are generally recognized as revenue during the period commissions are paid by the insurance carrier. Brokerage commissions are recognized on a trade-date basis. Bank service charges are recorded when earned.
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 low-to-moderate
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 pre-acquisition 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 7 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 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 two-step two-step two-step The first step (“Step 1”) 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 indicator of potential impairment is deemed to exist and a second step is performed to measure the amount of such impairment, if any. At this time, none of the Company’s identified reporting units are at risk of failing the Step 1 goodwill impairment test. The second step (“Step 2”) involves calculating the implied fair value of goodwill for each reporting unit for which impairment was indicated in Step 1. The implied fair value of goodwill is determined in a manner similar to how the amount of goodwill is determined in a business combination (i.e. by measuring the excess of the estimated fair value of the reporting unit, as determined in Step 1, over the aggregate estimated fair values of the individual assets, liabilities, and identifiable intangibles applicable to that reporting unit as of the impairment testing date). If the implied fair value of goodwill exceeds the carrying amount of goodwill assigned to the reporting unit, no impairment exists. If the carrying amount of goodwill assigned to a reporting unit exceeds the implied fair value of the goodwill, an impairment loss is recorded in an amount equal to such excess. An impairment loss cannot exceed the carrying amount of goodwill assigned to a reporting unit, and the loss (write-down) 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.
Real Estate Owned	Real Estate Owned Real estate owned (“REO”) properties acquired through foreclosure or deed-in-lieu
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. Tax benefits attributable to deductions in excess of financial statement amounts arising from the exercise of non-statutory paid-in 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
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 two-class two-class
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, but also include foreign exchange contracts. The interest rate and foreign exchange risks associated with customer interest rate swaps 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” 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 securities and CMOs); • 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 2016 Stock Compensation In June 2014, the Financial Accounting Standards Board (the “FASB”) amended its standards with respect to stock compensation to require that a performance target that affects vesting, and that could be achieved after the requisite service period, be treated as a performance condition. As such, the performance target should not be reflected in estimating the grant date fair value of the award. The amendment further clarifies that compensation cost should be recognized in the period in which it becomes probable that the performance target will be achieved and should represent the compensation cost attributable to those periods for which the requisite service has already been rendered. This amendment, which is being applied prospectively, became effective for People’s United on January 1, 2016 and did not have a significant impact on the Company’s Consolidated Financial Statements. Consolidation In February 2015, the FASB amended its standards with respect to the analysis that a reporting entity must perform in determining whether certain types of legal entities should be consolidated. The amendment modifies the evaluation of whether limited partnerships or similar legal entities are variable interest entities (“VIEs”) or voting interest entities, eliminates the presumption that a general partner should consolidate a limited partnership and affects the consolidation analysis of reporting entities that are involved with VIEs, particularly those that have fee arrangements and related party relationships. This amendment, which is being applied retrospectively, became effective for People’s United on January 1, 2016 and did not have a significant impact on the Company’s Consolidated Financial Statements. Presentation of Debt Issuance Costs In April 2015, the FASB amended its standards with respect to the presentation of debt issuance costs by changing the presentation of such costs from an asset on the statement of condition to a deduction from the related debt liability. This amendment, which is being applied retrospectively, became effective for People’s United on January 1, 2016 and did not have a significant impact on the Company’s Consolidated Financial Statements. See Notes 8 and 11. Retirement Benefits In April 2015, the FASB amended its standards with respect to the accounting for retirement benefits by providing a practical expedient, for entities with fiscal year-ends that do not coincide with a month-end, month-end year-end. month-end, month-end Business Combinations In September 2015, the FASB amended its standards with respect to business combinations to eliminate the requirement to restate prior period financial statements for measurement period adjustments. Instead, the amended guidance requires that, during the measurement period, an acquirer recognize adjustments of previously recorded provisional amounts in the reporting period in which such adjustments are determined. In doing so, the acquirer would be required to record the cumulative effect of measurement period adjustments on current and prior period earnings, including the prior period impact on depreciation, amortization or other income statement items. The amended standard also contains additional disclosure requirements with respect to measurement period adjustments. This amendment, which is being applied prospectively, became effective for People’s United on January 1, 2016 and did not have a significant impact on the Company’s Consolidated Financial Statements. Standards effective in 2017 Derivatives and Hedging In March 2016, the FASB amended its standards with respect to derivatives and hedging. The first amendment clarifies that a change in the counterparty to a derivative instrument that has been designated as the hedging instrument does not, in and of itself, require dedesignation of that hedging relationship and discontinuation of the application of hedge accounting. This amendment does not require additional disclosures beyond disclosure about a change in accounting principle in the period of adoption. The second amendment clarifies the requirements for assessing whether contingent call (put) options that can accelerate the payment of principal on debt instruments are clearly and closely related to their debt hosts. An entity performing the assessment is required to assess the embedded call (put) options solely in accordance with a four-step decision sequence and no longer is required to assess whether the event that triggers the ability to exercise the option is related to interest rate or credit risk. For public business entities, both of these new amendments are effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2016 (January 1, 2017 for People’s United) and may be applied either prospectively or on a modified retrospective basis. Earlier application is permitted as of the beginning of an interim or annual reporting period. The adoption of these amendments is not expected to have a significant impact on the Company’s Consolidated Financial Statements. Investments – Equity Method and Joint Ventures In March 2016, the FASB amended its standards with respect to the equity method of accounting by eliminating the requirement that, upon an investment qualifying for use of the equity method of accounting as a result of an increase in the level of ownership interest or degree of influence, an investor must adjust the investment, results of operations and retained earnings retrospectively, as if the equity method of accounting had been in effect during all previous periods that the investment was held. Rather, under the new guidance, upon qualifying for the equity method of accounting, no retroactive adjustment of the investment is required. Instead, any unrealized holding gain or loss is to be recognized through other comprehensive income on the date the investment qualifies for use of the equity method. This amendment is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2016 (January 1, 2017 for People’s United) and is to be applied prospectively. The adoption of this amendment is not expected to have a significant impact on the Company’s Consolidated Financial Statements. Stock Compensation In March 2016, the FASB amended its standards with respect to certain aspects of the accounting for share-based Standards effective in 2018 Revenue Recognition In May 2014, the FASB amended its standards with respect to revenue recognition. The amended guidance serves to replace all current U.S. GAAP guidance on this topic and eliminate all industry-specific guidance, providing a unified model to determine when and how revenue is recognized. The underlying principle is that a company should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The amendments also require enhanced disclosures regarding the nature, amount, timing and uncertainty of revenue and cash flows arising from an entity’s contracts with customers. As originally issued, this new guidance, which can be applied retrospectively or through the use of the cumulative effect transition method, was to become effective for fiscal years, and interim periods within those fiscal years, beginning on or after December 15, 2016 (January 1, 2017 for People’s United) and early adoption was not permitted. In July 2015, the FASB approved a one-year The Company will adopt this guidance in the first quarter of 2018 using the modified retrospective method with a cumulative-effect adjustment to opening retained earnings, as appropriate. The Company’s revenue is comprised of net interest income on financial assets and financial liabilities and non-interest income. The scope of the guidance explicitly excludes net interest income as well as other revenues associated with financial assets and liabilities, including loans, leases, securities and derivatives. Accordingly, the majority of the Company’s revenues will not be affected. Other recurring revenue streams are within the scope of the guidance, including revenues associated with certain products and services offered by the Company’s trust and investment management, insurance and brokerage businesses. The Company’s preliminary analysis suggests that adoption of the guidance is not expected to have a material impact on its current accounting policies or the timing or amount of revenue recognized in the Company’s Consolidated Financial Statements. However, the FASB continues to release new accounting guidance related to the adoption of the amended standard which could impact the Company’s preliminary conclusions with respect to materiality. Presentation of Deferred Taxes In November 2015, the FASB amended its standards with respect to the presentation of deferred income taxes to eliminate the requirement to separate deferred income tax liabilities and assets into current and noncurrent amounts in a classified statement of condition, thereby simplifying the presentation of deferred income taxes. For public business entities, this new amendment is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2017 (January 1, 2018 for People’s United) and may be applied either prospectively or retrospectively to all periods presented. Earlier application of the amendment is permitted as of the beginning of an interim or annual reporting period. The adoption of this amendment is not expected to have a significant impact on the Company’s Consolidated Financial Statements. Recognition and Measurement of Financial Instruments In January 2016, the FASB amended its standards to address certain aspects of recognition, presentation and disclosure of financial instruments. The amended guidance (i) requires that equity investments be measured at fair value with changes in fair value recognized in net income and (ii) simplifies the impairment assessment of equity investments without readily determinable fair values by permitting a qualitative assessment to identify impairment. The guidance also contains additional disclosure and presentation requirements associated with financial instruments. For public business entities this new guidance is effective in fiscal years, and interim periods within those fiscal years, beginning after December 15, 2017 (January 1, 2018 for People’s United). The cumulative effect transition method will be applied to all outstanding instruments as of the date of adoption, while changes to the accounting for equity investments without readily determinable fair values will be applied prospectively. The Company continues to evaluate the impact of the amended guidance on the Company’s Consolidated Financial Statements. Statement of Cash Flows: Classification of Certain Cash Receipts and Cash Payments In August 2016, the FASB amended its standards to address the classification of certain cash receipts and payments within the statement of cash flows. Specifically, the amended guidance addresses the following: (i) debt prepayment or debt extinguishment costs; (ii) settlement of zero-coupon Standards effective in 2019 Accounting for Leases In February 2016, the FASB amended its standards with respect to the accounting for leases. The amended guidance serves to replace all current U.S. GAAP guidance on this topic and requires that an operating lease be recognized on the statement of condition as a “right-to-use” The Company has begun its evaluation of the amended guidance including the potential impact on its Consolidated Financial Statements. To date, the Company has identified several areas that are within the scope of the guidance, including its contracts with respect to leased real estate and office equipment. In addition, operating lease agreements entered into with customers by the Company’s equipment financing businesses are also subject to the new guidance. The Company continues to evaluate the impact of the guidance, including determining whether additional contracts exist that are deemed to be in scope. As such, no conclusions have yet been reached regarding the potential impact of adoption on the Company’s Consolidated Financial Statements. Further, to date, no guidance has been issued by either the Company’s or the Bank’s primary regulator with respect to how the impact of the amended standard is to be treated for regulatory capital purposes. 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, including available-for-sale While early adoption is permitted, the Company does not expect to elect that option. The Company has begun its evaluation of the amended guidance including the potential impact on its Consolidated Financial Statements. As a result of the required change in approach toward determining estimated credit losses from the current “incurred loss” model to one based on estimated cash flows over a loan’s contractual life, adjusted for prepayments (a “life of loan” model), the Company expects the new guidance will result in an increase in the allowance for loan losses, particularly for longer duration portfolios. The Company also expects the new guidance may result in an allowance for debt securities. In both cases, the extent of the change is indeterminable at this time as it will be dependent upon portfolio composition and credit quality at the adoption date, as well as economic conditions and forecasts at that time. Further, to date, no guidance has been issued by either the Company’s or the Bank’s primary regulator with respect to how the impact of the amended standard is to be treated for regulatory capital purposes. 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. The adoption of this amendment is not expected to have a significant impact on the Company’s Consolidated Financial Statements.
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 consecutive years of the last ten years that produce the highest average. 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 1,000 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 a qualified defined benefit pension plan that covers former Chittenden employees who meet certain eligibility requirements (the “Chittenden Qualified Plan”). Effective December 31, 2005, accrued benefits were frozen based on participants’ then-current service and pay levels. Interest continues to be credited on undistributed balances at a crediting rate specified by the Chittenden Qualified Plan. During April 2010, participants who were in payment status as of April 1, 2010, or whose accrued benefit as of that date was scheduled to be paid in the form of an annuity commencing May 1, 2010 based upon elections made by April 15, 2010, were transferred 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 “Supplemental Plans”) and (ii) an unfunded plan that provides retirees with optional medical, dental and life insurance benefits (the “Other 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. 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 an other postretirement plan. Plan assets and benefit obligations are required to be measured as of the date of the employer’s fiscal year-end.
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 $5.0 million in 2016, $5.1 million in 2015 and $5.3 million in 2014. At December 31, 2016, the loan balance totaled $184.9 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 1,000 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 3,484,525 shares of People’s United common stock have been allocated or committed to be released to participants’ accounts. At December 31, 2016, 6,969,050 shares of People’s United common stock, with a fair value of $134.9 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 paid-in
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 one-year
Fair Value Measurements	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 Recurring Fair Value Measurements Trading Account Securities and 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 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, GSE mortgage-backed securities and CMOs, all of which are included in Level 2. The Company’s available-for-sale available-for-sale 10- 15-year 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 10- 15-year Other Assets As discussed in Note 17, 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, 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, 2016 (in millions) Level 1 Level 2 Level 3 Total Financial assets: Trading account securities: U.S. Treasury $ 6.8 $ — $ — $ 6.8 Securities available for sale: U.S. Treasury and agency 859.7 — — 859.7 GSE mortgage-backed securities and CMOs — 3,550.0 — 3,550.0 Equity securities — 0.2 — 0.2 Other assets: Exchange-traded funds 32.6 — — 32.6 Fixed income securities — 4.3 — 4.3 Mutual funds 2.7 — — 2.7 Interest rate swaps — 173.1 — 173.1 Foreign exchange contracts — 0.6 — 0.6 Forward commitments to sell residential mortgage loans — 0.3 — 0.3 Total $ 901.8 $ 3,728.5 $ — $ 4,630.3 Financial liabilities: Interest rate swaps $ — $ 121.0 $ — $ 121.0 Risk participation agreements (1) — — — — Foreign exchange contracts — 0.3 — 0.3 Interest rate-lock commitments on residential mortgage loans — 0.4 — 0.4 Total $ — $ 121.7 $ — $ 121.7 Fair Value Measurements Using As of December 31, 2015 (in millions) Level 1 Level 2 Level 3 Total Financial assets: Trading account securities: U.S. Treasury $ 6.7 $ — $ — $ 6.7 Securities available for sale: U.S. Treasury and agency 362.8 — — 362.8 GSE residential mortgage-backed securities and CMOs — 4,164.7 — 4,164.7 Equity securities — 0.2 — 0.2 Other assets: Exchange-traded funds 29.4 — — 29.4 Fixed income securities — 5.1 — 5.1 Mutual funds 2.0 — — 2.0 Interest rate swaps — 157.0 — 157.0 Foreign exchange contracts — 0.6 — 0.6 Forward commitments to sell residential mortgage loans — 0.6 — 0.6 Total $ 400.9 $ 4,328.2 $ — $ 4,729.1 Financial liabilities: Interest rate swaps $ — $ 108.5 $ — $ 108.5 Risk participation agreements (1) — — — — Foreign exchange contracts — 0.2 — 0.2 Interest rate-lock commitments on residential mortgage loans — 0.8 — 0.8 Total $ — $ 109.5 $ — $ 109.5 (1) As of December 31, 2016 and 2015, the fair value of risk participation agreements totaled less than $0.1 million (see Note 21). There were no transfers into or out of the Level 1 or Level 2 categories during the years ended December 31, 2016 and 2015. Non-Recurring Loans Held for Sale Residential mortgage 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 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: the present value of expected future cash flows discounted at the loan’s original effective interest rate; the loan’s observable market price; or 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 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 The following tables summarize People’s United’s assets that are measured at fair value on a non-recurring Fair Value Measurements Using As of December 31, 2016 (in millions) Level 1 Level 2 Level 3 Total Loans held for sale (1) $ — $ 39.3 $ — $ 39.3 Impaired loans (2) — — 55.9 55.9 REO and repossessed assets (3) — — 19.3 19.3 Total $ — $ 39.3 $ 75.2 $ 114.5 Fair Value Measurements Using As of December 31, 2015 (in millions) Level 1 Level 2 Level 3 Total Loans held for sale (1) $ — $ 34.5 $ — $ 34.5 Impaired loans (2) — — 49.1 49.1 REO and repossessed assets (3) — — 22.1 22.1 Total $ — $ 34.5 $ 71.2 $ 105.7 (1) Consists of residential mortgage loans; no fair value adjustments were recorded for the years ended December 31, 2016 and 2015. (2) 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 $40.8 million of Commercial loans and $15.1 million of Retail loans at December 31, 2016. The provision for loan losses on impaired loans totaled $3.8 million and $6.7 million for the years ended December 31, 2016 and 2015, respectively. (3) Represents: (i) $8.1 million of residential REO; (ii) $4.0 million of commercial REO; and (iii) $7.2 million of repossessed assets at December 31, 2016. Charge-offs to the allowance for loan losses related to loans that were transferred to REO or repossessed assets totaled $3.7 million and $1.8 million for the years ended December 31, 2016 and 2015, respectively. Write downs and net loss on sale of foreclosed/repossessed assets charged to non-interest Financial Assets and Financial Liabilities Not Measured At Fair Value As discussed in Note 1, 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 (an “exit price” approach to fair value). Acceptable valuation techniques (when quoted market prices are not available) that might be used to estimate the fair value of financial instruments include discounted cash flow analyses and comparison to similar instruments. Such estimates are highly subjective and require judgments regarding significant matters such as the amount and timing of future cash flows and the selection of discount rates that appropriately reflect market and credit risks. Changes in these judgments often have a material impact on the fair value estimates. In addition, since these estimates are made as of a specific point in time, they are susceptible to material near-term changes. Fair values estimated in this manner do not reflect any premium or discount that could result from the sale of a large volume of a particular financial instrument, nor do they reflect possible tax ramifications or estimated transaction costs. The following is a description of the principal valuation methods used by People’s United for those financial instruments that are not measured at fair value either on a recurring or non-recurring Cash, Short-Term Investments and Securities Purchased Under Agreements to Resell Cash and due from banks are classified as Level 1. Short-term investments and securities purchased under agreements to resell have fair values that approximate the respective carrying amounts because the instruments are payable on demand or have short-term maturities, and present relatively low credit risk and IRR. As such, these fair values are classified as Level 2. Securities Held to Maturity When available, the fair values of investment securities held to maturity are measured based on quoted market prices for identical securities in active markets and, accordingly, are classified as Level 1 assets. When quoted market prices for identical securities are not available, fair values are estimated based on quoted prices for similar assets in active markets or through the use of pricing models containing observable inputs (i.e. market interest rates, financial information and credit ratings of the issuer, etc.). These fair values are included in Level 2. In cases where there may be limited information available and/or little or no market activity for the underlying security, fair value is estimated using pricing models containing unobservable inputs and classified as Level 3. FHLB and FRB-NY Both FHLB and FRB-NY non-marketable Loans For valuation purposes, the loan portfolio is segregated into its significant categories, which are commercial real estate, commercial and industrial, equipment financing, residential mortgage, home equity and other consumer. These categories are further segregated, where appropriate, into components based on significant financial characteristics such as type of interest rate (fixed or adjustable) and payment status (performing or non-performing). The fair values of performing loans were estimated by discounting the anticipated cash flows from the respective portfolios, assuming future prepayments and using market interest rates for new loans with comparable credit risk. As a result, the valuation method for performing loans, which is consistent with certain guidance provided in accounting standards, does not fully incorporate the “exit price” approach to fair value. The fair values of non-performing Deposit Liabilities The fair values of time deposits represent contractual cash flows discounted at current rates determined by reference to observable inputs including a LIBOR/swap curve over the remaining period to maturity. As such, these fair values are classified as Level 2. The fair values of other deposit liabilities (those with no stated maturity, such as checking and savings accounts) are equal to the carrying amounts payable on demand. Deposit fair values do not include the intangible value of core deposit relationships that comprise a significant portion of People’s United’s deposit base. Management believes that People’s United’s core deposit relationships provide a relatively stable, low-cost Borrowings and Notes and Debentures The fair values of federal funds purchased, repurchase agreements and other borrowings are equal to the carrying amounts due to the short maturities (generally overnight). The fair values of FHLB advances represent contractual repayments discounted using interest rates currently available on borrowings with similar characteristics and remaining maturities and are classified as Level 2. The fair values of notes and debentures were based on dealer quotes and are classified as Level 2. Lending-Related Financial Instruments The estimated fair values of People’s United’s lending-related financial instruments approximate the respective carrying amounts. Such instruments include commitments to extend credit, unadvanced lines of credit and letters of credit, for which fair values were estimated based on an analysis of the interest rates and fees currently charged to enter into similar transactions, considering the remaining terms of the instruments and the creditworthiness of the potential borrowers. 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 Carrying Amount Estimated Fair Value As of December 31, 2016 (in millions) Level 1 Level 2 Level 3 Total Financial assets: Cash and due from banks $ 432.4 $ 432.4 $ — $ — $ 432.4 Short-term investments 181.7 — 181.7 — 181.7 Securities held to maturity 2,005.4 — 2,011.2 1.5 2,012.7 FHLB and FRB stock 315.8 — 315.8 — 315.8 Total loans, net (1) 29,459.7 — 6,028.4 23,238.1 29,266.5 Financial liabilities: Time deposits 4,542.2 — 4,539.7 — 4,539.7 Other deposits 25,318.6 — 25,318.6 — 25,318.6 FHLB advances 3,061.1 — 3,064.4 — 3,064.4 Federal funds purchased 617.0 — 617.0 — 617.0 Customer repurchase agreements 343.3 — 343.3 — 343.3 Other borrowings 35.4 — 35.4 — 35.4 Notes and debentures 1,030.1 — 1,000.0 — 1,000.0 (1) Excludes impaired loans totaling $55.9 million measured at fair value on a non-recurring Carrying Amount Estimated Fair Value As of December 31, 2015 (in millions) Level 1 Level 2 Level 3 Total Financial assets: Cash and due from banks $ 334.8 $ 334.8 $ — $ — $ 334.8 Short-term investments 380.5 — 380.5 — 380.5 Securities held to maturity 1,609.6 — 1,661.0 1.5 1,662.5 FHLB and FRB stock 305.4 — 305.4 — 305.4 Total loans, net (1) 28,150.8 — 5,315.3 22,893.7 28,209.0 Financial liabilities: Time deposits 4,818.1 — 4,836.5 — 4,836.5 Other deposits 23,599.3 — 23,599.3 — 23,599.3 FHLB advances 3,463.8 — 3,468.7 — 3,468.7 Customer repurchase agreements 469.5 — 469.5 — 469.5 Federal funds purchased 374.0 — 374.0 — 374.0 Notes and debentures 1,033.1 — 1,012.9 — 1,012.9 (1) Excludes impaired loans totaling $49.1 million measured at fair value on a non-recurring
Segment Information	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 Retail Banking non-institutional 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 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 During the quarter ended March 31, 2015, the Company modified its FTP methodology relating to certain deposit products that resulted in a reduction in the funding credit recognized within net interest income for Commercial Banking and Retail Banking, with the offset reflected in Treasury. Prior period segment results have not been adjusted and continue to reflect the previous FTP methodology. A five-year rolling average net charge-off year-to-year People’s United allocates a majority of non-interest full-absorption non-interest 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 certain gains totaling $7.5 million, $9.2 million and $20.6 million for the years ended December 31, 2016, 2015 and 2014, respectively (included in total non-interest non-interest

Cash and Short-Term Investmen36

Cash and Short-Term Investments (Tables)	12 Months Ended
	Dec. 31, 2016
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) 2016 2015 Interest-bearing deposits at the FRB-NY $ 169.8 $ 333.7 Money market mutual funds 7.9 8.0 Other (1) 4.0 38.8 Total short-term investments $ 181.7 $ 380.5 (1) Includes cash collateral posted for certain derivative positions at December 31, 2015 (none at December 31, 2016).

Securities (Tables)

Securities (Tables)	12 Months Ended
	Dec. 31, 2016
Investments, Debt and Equity Securities [Abstract]
Available-for-Sale and Held-to-Maturity Securities Gains (Losses)	The amortized cost, gross unrealized gains and losses, and fair value of People’s United’s securities available for sale and securities held to maturity are as follows: As of December 31, 2016 (in millions) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Securities available for sale: Debt securities: U.S. Treasury and agency $ 889.9 $ 0.3 $ (30.5 ) $ 859.7 GSE mortgage-backed securities and CMOs 3,573.1 15.0 (38.1 ) 3,550.0 Total debt securities 4,463.0 15.3 (68.6 ) 4,409.7 Equity securities 0.2 — — 0.2 Total securities available for sale $ 4,463.2 $ 15.3 $ (68.6 ) $ 4,409.9 Securities held to maturity: Debt securities: State and municipal $ 1,499.1 $ 33.9 $ (23.5 ) $ 1,509.5 GSE mortgage-backed securities 500.8 — (3.2 ) 497.6 Other 5.5 — — 5.5 Total securities held to maturity $ 2,005.4 $ 33.9 $ (26.7 ) $ 2,012.6 As of December 31, 2015 (in millions) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Securities available for sale: Debt securities: U.S. Treasury and agency $ 363.7 $ 0.2 $ (1.1 ) $ 362.8 GSE mortgage-backed securities and CMOs 4,191.3 22.3 (48.9 ) 4,164.7 Total debt securities 4,555.0 22.5 (50.0 ) 4,527.5 Equity securities 0.2 — — 0.2 Total securities available for sale $ 4,555.2 $ 22.5 $ (50.0 ) $ 4,527.7 Securities held to maturity: Debt securities: State and municipal $ 1,019.6 $ 55.8 $ (0.1 ) $ 1,075.3 GSE mortgage-backed securities 588.5 — (2.8 ) 585.7 Other 1.5 — — 1.5 Total securities held to maturity $ 1,609.6 $ 55.8 $ (2.9 ) $ 1,662.5
Summary of Amortized Cost, Fair Value and Fully Taxable Equivalent Yield of Debt Securities 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, 2016, based on remaining period to contractual maturity. Information for GSE mortgage-backed securities and CMOs is based on the final contractual maturity dates without considering repayments and prepayments. Available for Sale Held to Maturity (dollars in millions) Amortized Cost Fair Value FTE Yield Amortized Cost Fair Value FTE Yield U.S. Treasury and agency: Within 1 year $ 1.0 $ 1.0 0.56 % $ — $ — — % After 1 but within 5 years 187.8 186.1 1.31 — — — After 5 but within 10 years 701.1 672.6 1.38 — — — Total 889.9 859.7 1.36 — — — GSE mortgage-backed securities and CMOs: After 5 but within 10 years 870.7 884.5 2.40 — — — After 10 years 2,702.4 2,665.5 1.78 500.8 497.6 2.05 Total 3,573.1 3,550.0 1.93 500.8 497.6 2.05 State and municipal: Within 1 year — — — 4.6 4.6 4.42 After 1 but within 5 years — — — 26.9 27.2 4.98 After 5 but within 10 years — — — 365.0 379.3 3.35 After 10 years — — — 1,102.6 1,098.4 4.34 Total — — — 1,499.1 1,509.5 4.11 Other: Within 1 year — — — 1.5 1.5 2.10 After 5 but within 10 years — — — 4.0 4.0 5.00 Total — — — 5.5 5.5 4.21 Total: Within 1 year 1.0 1.0 0.56 6.1 6.1 3.86 After 1 but within 5 years 187.8 186.1 1.31 26.9 27.2 4.98 After 5 but within 10 years 1,571.8 1,557.1 1.94 369.0 383.3 3.37 After 10 years 2,702.4 2,665.5 1.78 1,603.4 1,596.0 3.62 Total $ 4,463.0 $ 4,409.7 1.82 % $ 2,005.4 $ 2,012.6 3.59 %
Continuous Unrealized Loss Position on Available-for-Sale and Held-to-Maturities Securities	The following tables summarize 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 Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses As of December 31, 2016 (in millions) Securities available for sale: GSE mortgage-backed securities and CMOs $ 2,339.6 $ (26.6 ) $ 396.9 $ (11.5 ) $ 2,736.5 $ (38.1 ) U.S. Treasury and agency 828.3 (30.5 ) — — 828.3 (30.5 ) Securities held to maturity: GSE mortgage-backed securities 497.6 (3.2 ) — — 497.6 (3.2 ) State and municipal 581.7 (23.5 ) — — 581.7 (23.5 ) Total $ 4,247.2 $ (83.8 ) $ 396.9 $ (11.5 ) $ 4,644.1 $ (95.3 ) Continuous Unrealized Loss Position Less Than 12 Months 12 Months Or Longer Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses As of December 31, 2015 (in millions) Securities available for sale: GSE mortgage-backed securities and CMOs $ 2,200.8 $ (20.3 ) $ 933.9 $ (28.6 ) $ 3,134.7 $ (48.9 ) U.S. Treasury and agency 346.3 (1.1 ) — — 346.3 (1.1 ) Securities held to maturity: GSE mortgage-backed securities 585.7 (2.8 ) — — 585.7 (2.8 ) State and municipal 22.3 (0.1 ) 3.7 — 26.0 (0.1 ) Total $ 3,155.1 $ (24.3 ) $ 937.6 $ (28.6 ) $ 4,092.7 $ (52.9 )
Schedule of Gains and Losses from Sales of Debt Securities	The components of net security (losses) gains on debt securities are summarized below. Net gains and losses on trading account securities, which are not included in the table below, totaled less than $0.1 million for each of the years ended December 31, 2016, 2015 and 2014. Years ended December 31 (in millions) 2016 2015 2014 Debt securities: Gains $ 0.2 $ 0.3 $ 4.4 Losses (6.1 ) (0.3 ) (1.4 ) Net security (losses) gains $ (5.9 ) $ — $ 3.0

Loans (Tables)

Loans (Tables)	12 Months Ended
	Dec. 31, 2016
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: 2016 2015 As of December 31 (in millions) Originated Acquired Total Originated Acquired Total Commercial: Commercial real estate $ 10,012.6 $ 234.7 $ 10,247.3 $ 9,696.9 $ 331.9 $ 10,028.8 Commercial and industrial 7,939.0 186.1 8,125.1 7,526.4 222.3 7,748.7 Equipment financing 3,020.9 11.6 3,032.5 2,957.6 15.7 2,973.3 Total Commercial Portfolio 20,972.5 432.4 21,404.9 20,180.9 569.9 20,750.8 Retail: Residential mortgage: Adjustable-rate 5,453.8 95.3 5,549.1 4,733.3 117.9 4,851.2 Fixed-rate 613.5 54.1 667.6 536.1 69.7 605.8 Total residential mortgage 6,067.3 149.4 6,216.7 5,269.4 187.6 5,457.0 Home equity and other consumer: Home equity 2,044.9 27.7 2,072.6 2,115.5 38.2 2,153.7 Other consumer 50.0 0.7 50.7 48.5 0.9 49.4 Total home equity and other consumer 2,094.9 28.4 2,123.3 2,164.0 39.1 2,203.1 Total Retail Portfolio 8,162.2 177.8 8,340.0 7,433.4 226.7 7,660.1 Total loans $ 29,134.7 $ 610.2 $ 29,744.9 $ 27,614.3 $ 796.6 $ 28,410.9
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, 2016, 2015 and 2014. 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, 2013 $ 158.5 $ 9.8 $ 168.3 $ 19.0 $ 0.5 $ 19.5 $ 187.8 Charge-offs (22.3 ) (2.6 ) (24.9 ) (11.1 ) (0.1 ) (11.2 ) (36.1 ) Recoveries 3.6 — 3.6 2.4 — 2.4 6.0 Net loan charge-offs (18.7 ) (2.6 ) (21.3 ) (8.7 ) (0.1 ) (8.8 ) (30.1 ) Provision for loan losses 29.8 2.6 32.4 8.2 — 8.2 40.6 Balance at December 31, 2014 169.6 9.8 179.4 18.5 0.4 18.9 198.3 Charge-offs (20.1 ) — (20.1 ) (7.9 ) — (7.9 ) (28.0 ) Recoveries 4.9 — 4.9 2.4 — 2.4 7.3 Net loan charge-offs (15.2 ) — (15.2 ) (5.5 ) — (5.5 ) (20.7 ) Provision for loan losses 27.4 (1.9 ) 25.5 8.1 (0.2 ) 7.9 33.4 Balance at December 31, 2015 181.8 7.9 189.7 21.1 0.2 21.3 211.0 Charge-offs (13.5 ) (1.4 ) (14.9 ) (8.5 ) — (8.5 ) (23.4 ) Recoveries 2.1 — 2.1 3.0 — 3.0 5.1 Net loan charge-offs (11.4 ) (1.4 ) (12.8 ) (5.5 ) — (5.5 ) (18.3 ) Provision for loan losses 28.4 (0.4 ) 28.0 8.6 — 8.6 36.6 Balance at December 31, 2016 $ 198.8 $ 6.1 $ 204.9 $ 24.2 $ 0.2 $ 24.4 $ 229.3
Summary of Allowance for Loan Losses by Loan Portfolio Segment and Impairment Methodology	The following is a summary, by loan portfolio segment and impairment methodology, of the allowance for loan losses and related portfolio balances: As of December 31, 2016 (in millions) Originated Loans Individually Originated Loans Collectively Evaluated for Impairment Acquired Loans (Discounts Related to Credit Quality) Total Portfolio Allowance Portfolio Allowance Portfolio Allowance Portfolio Allowance Commercial $ 161.8 $ 5.8 $ 20,810.7 $ 193.0 $ 432.4 $ 6.1 $ 21,404.9 $ 204.9 Retail 91.8 3.2 8,070.4 21.0 177.8 0.2 8,340.0 24.4 Total $ 253.6 $ 9.0 $ 28,881.1 $ 214.0 $ 610.2 $ 6.3 $ 29,744.9 $ 229.3 As of December 31, 2015 (in millions) Originated Loans Individually Evaluated for Impairment Originated Loans Collectively Evaluated for Impairment Acquired Loans (Discounts Related to Credit Quality) Total Portfolio Allowance Portfolio Allowance Portfolio Allowance Portfolio Allowance Commercial $ 155.1 $ 5.5 $ 20,025.8 $ 176.3 $ 569.9 $ 7.9 $ 20,750.8 $ 189.7 Retail 97.0 3.9 7,336.4 17.2 226.7 0.2 7,660.1 21.3 Total $ 252.1 $ 9.4 $ 27,362.2 $ 193.5 $ 796.6 $ 8.1 $ 28,410.9 $ 211.0
Summarized Recorded Investments, by Class of Loan, of Originated Non-Performing Loans	The recorded investments, by class of loan, of originated non-performing As of December 31 (in millions) 2016 2015 2014 Commercial: Commercial real estate $ 22.3 $ 30.2 $ 60.2 Commercial and industrial 41.5 44.9 55.8 Equipment financing 39.4 27.5 25.4 Total (1) 103.2 102.6 141.4 Retail: Residential mortgage 27.4 37.2 37.6 Home equity 17.4 19.5 17.9 Other consumer — 0.1 0.1 Total (2) 44.8 56.8 55.6 Total $ 148.0 $ 159.4 $ 197.0 (1) Reported net of government guarantees totaling $13.1 million, $16.9 million and $17.6 million at December 31, 2016, 2015 and 2014, 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, 2016, the principal loan classes to which these government guarantees relate are commercial and industrial loans (99%) and commercial real estate loans (1%). (2) Includes $9.8 million, $19.9 million and $18.9 million of loans in the process of foreclosure at December 31, 2016, 2015 and 2014, 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, 2016 and 2015. For purposes of this disclosure, recorded investments represent amounts immediately prior to and subsequent to the restructuring. Year ended December 31, 2016 (dollars in millions) Number of Pre-Modification Outstanding Recorded Investment Post-Modification Outstanding Recorded Investment Commercial: Commercial real estate (1) 18 $ 28.2 $ 28.2 Commercial and industrial (2) 51 44.9 44.9 Equipment financing (3) 61 30.7 30.7 Total 130 103.8 103.8 Retail: Residential mortgage (4) 57 15.5 15.5 Home equity (5) 62 4.5 4.5 Other consumer — — — Total 119 20.0 20.0 Total 249 $ 123.8 $ 123.8 (1) Represents the following concessions: extension of term (13 contracts; recorded investment of $8.1 million); reduced payment and/or payment deferral (3 contracts; recorded investment of $3.0 million); or a combination of concessions (2 contracts; recorded investment of $17.1 million). (2) Represents the following concessions: extension of term (32 contracts; recorded investment of $23.4 million); reduced payment and/or payment deferral (10 contracts; recorded investment of $9.9 million); or a combination of concessions (9 contracts; recorded investment of $11.6 million). (3) Represents the following concessions: extension of term (17 contracts; recorded investment of $6.2 million); reduced payment and/or payment deferral (30 contracts; recorded investment of $17.6 million); or a combination of concessions (14 contracts; recorded investment of $6.9 million). (4) Represents the following concessions: loans restructured through bankruptcy (21 contracts; recorded investment of $3.7 million); reduced payment and/or payment deferral (13 contracts; recorded investment of $5.8 million); or a combination of concessions (23 contracts; recorded investment of $6.0 million). (5) Represents the following concessions: loans restructured through bankruptcy (38 contracts; recorded investment of $2.5 million); reduced payment and/or payment deferral (4 contracts; recorded investment of $0.4 million); or a combination of concessions (20 contracts; recorded investment of $1.6 million). Year ended December 31, 2015 (dollars in millions) Number of Contracts Pre-Modification Outstanding Recorded Investment Post-Modification Outstanding Recorded Investment Commercial: Commercial real estate (1) 26 $ 15.2 $ 15.2 Commercial and industrial (2) 61 80.6 80.6 Equipment financing (3) 48 28.5 28.5 Total 135 124.3 124.3 Retail: Residential mortgage (4) 66 20.1 20.1 Home equity (5) 98 9.5 9.5 Other consumer — — — Total 164 29.6 29.6 Total 299 $ 153.9 $ 153.9 (1) Represents the following concessions: extension of term (21 contracts; recorded investment of $8.9 million); reduced payment and/or payment deferral (2 contracts; recorded investment of $1.2 million); or a combination of concessions (3 contracts; recorded investment of $5.1 million). (2) Represents the following concessions: extension of term (35 contracts; recorded investment of $41.1 million); reduced payment and/or payment deferral (20 contracts; recorded investment of $35.9 million); or a combination of concessions (6 contracts; recorded investment of $3.6 million). (3) Represents the following concessions: extension of term (1 contract; recorded investment of $0.1 million); reduced payment and/or payment deferral (38 contracts; recorded investment of $21.5 million); or a combination of concessions (9 contracts; recorded investment of $6.9 million). (4) Represents the following concessions: loans restructured through bankruptcy (24 contracts; recorded investment of $5.9 million); reduced payment and/or payment deferral (13 contracts; recorded investment of $4.7 million); temporary rate reduction (2 contracts; recorded investment of $0.3 million); or a combination of concessions (27 contracts; recorded investment of $9.2 million). (5) Represents the following concessions: loans restructured through bankruptcy (61 contracts; recorded investment of $5.2 million); reduced payment and/or payment deferral (7 contracts; recorded investment of $0.8 million); temporary rate reduction (1 contract; recorded investment of $0.5 million); or a combination of concessions (29 contracts; recorded investment of $3.0 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 of originated loans completed within the previous 12 months that subsequently defaulted during the years ended December 31, 2016 and 2015. 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 2016 or 2015. 2016 2015 Years ended December 31 (dollars in millions) Number of Contracts Recorded Investment as of Period End Number of Contracts Recorded Investment as of Period End Commercial: Commercial real estate 3 $ 1.1 5 $ 3.2 Commercial and industrial 5 8.6 4 1.2 Equipment financing 20 2.8 9 4.5 Total 28 12.5 18 8.9 Retail: Residential mortgage 12 2.6 17 2.6 Home equity 12 0.8 16 1.8 Other consumer — — — — Total 24 3.4 33 4.4 Total 52 $ 15.9 51 $ 13.3
Summary of Individually-Evaluated Impaired Loans by Class of Loan	People’s United’s impaired loans consist of certain originated loans, including all TDRs. The following table summarizes, by class of loan, information related to individually-evaluated impaired loans within the originated portfolio. 2016 2015 As of December 31 (in millions) Unpaid Principal Balance Recorded Investment Related Allowance for Loan Losses Unpaid Principal Balance Recorded Investment Related Allowance for Loan Losses Without a related allowance for loan losses: Commercial: Commercial real estate $ 41.4 $ 40.0 $ — $ 46.5 $ 45.3 $ — Commercial and industrial 50.7 45.7 — 53.2 50.8 — Equipment financing 38.2 35.3 — 32.6 26.0 — Retail: Residential mortgage 63.6 58.0 — 67.2 60.4 — Home equity 22.4 18.7 — 23.3 20.5 — Other consumer — — — — — — Total $ 216.3 $ 197.7 $ — $ 222.8 $ 203.0 $ — With a related allowance for loan losses: Commercial: Commercial real estate $ 12.2 $ 11.4 $ 0.6 $ 18.8 $ 14.7 $ 1.9 Commercial and industrial 25.9 25.0 4.7 19.2 14.7 3.3 Equipment financing 5.0 4.4 0.5 3.8 3.6 0.3 Retail: Residential mortgage 13.1 13.1 2.3 14.1 14.0 2.9 Home equity 2.1 2.0 0.9 2.3 2.1 1.0 Other consumer — — — — — — Total $ 58.3 $ 55.9 $ 9.0 $ 58.2 $ 49.1 $ 9.4 Total impaired loans: Commercial: Commercial real estate $ 53.6 $ 51.4 $ 0.6 $ 65.3 $ 60.0 $ 1.9 Commercial and industrial 76.6 70.7 4.7 72.4 65.5 3.3 Equipment financing 43.2 39.7 0.5 36.4 29.6 0.3 Total 173.4 161.8 5.8 174.1 155.1 5.5 Retail: Residential mortgage 76.7 71.1 2.3 81.3 74.4 2.9 Home equity 24.5 20.7 0.9 25.6 22.6 1.0 Other consumer — — — — — — Total 101.2 91.8 3.2 106.9 97.0 3.9 Total $ 274.6 $ 253.6 $ 9.0 $ 281.0 $ 252.1 $ 9.4
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 2016 2015 2014 Years ended December 31 (in millions) Average Recorded Investment Interest Income Recognized Average Recorded Investment Interest Income Recognized Average Recorded Investment Interest Income Recognized Commercial: Commercial real estate $ 56.7 $ 1.4 $ 65.6 $ 1.6 $ 76.6 $ 1.3 Commercial and industrial 62.6 2.1 71.6 1.8 46.4 1.1 Equipment financing 37.1 0.3 28.0 0.9 28.6 0.7 Total 156.4 3.8 165.2 4.3 151.6 3.1 Retail: Residential mortgage 71.8 1.6 75.2 1.5 71.8 1.5 Home equity 21.6 0.3 21.2 0.3 18.0 0.2 Other consumer — — — — — — Total 93.4 1.9 96.4 1.8 89.8 1.7 Total $ 249.8 $ 5.7 $ 261.6 $ 6.1 $ 241.4 $ 4.8
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, 2016 (in millions) Current 30-89 90 Days Total Total Commercial: Commercial real estate $ 9,989.9 $ 10.9 $ 11.8 $ 22.7 $ 10,012.6 Commercial and industrial 7,899.2 10.0 29.8 39.8 7,939.0 Equipment financing 2,941.5 68.4 11.0 79.4 3,020.9 Total 20,830.6 89.3 52.6 141.9 20,972.5 Retail: Residential mortgage 6,027.5 22.0 17.8 39.8 6,067.3 Home equity 2,030.3 5.2 9.4 14.6 2,044.9 Other consumer 49.7 0.3 — 0.3 50.0 Total 8,107.5 27.5 27.2 54.7 8,162.2 Total originated loans $ 28,938.1 $ 116.8 $ 79.8 $ 196.6 $ 29,134.7 Past Due As of December 31, 2015 (in millions) Current 30-89 90 Days Total Total Commercial: Commercial real estate $ 9,667.7 $ 15.0 $ 14.2 $ 29.2 $ 9,696.9 Commercial and industrial 7,466.5 13.1 46.8 59.9 7,526.4 Equipment financing 2,886.7 63.9 7.0 70.9 2,957.6 Total 20,020.9 92.0 68.0 160.0 20,180.9 Retail: Residential mortgage 5,212.9 31.1 25.4 56.5 5,269.4 Home equity 2,098.9 7.1 9.5 16.6 2,115.5 Other consumer 48.2 0.2 0.1 0.3 48.5 Total 7,360.0 38.4 35.0 73.4 7,433.4 Total originated loans $ 27,380.9 $ 130.4 $ 103.0 $ 233.4 $ 27,614.3
Summary of Credit Quality Indicators by Class of Loan	The following tables summarize, by class of loan, credit quality indicators: As of December 31, 2016 (in millions) Commercial Commercial Equipment Total Commercial: Originated loans: Pass $ 9,817.2 $ 7,580.6 $ 2,617.9 $ 20,015.7 Special mention 107.3 121.9 98.8 328.0 Substandard 87.1 233.3 304.2 624.6 Doubtful 1.0 3.2 — 4.2 Total originated loans 10,012.6 7,939.0 3,020.9 20,972.5 Acquired loans: Pass 182.9 155.5 1.0 339.4 Special mention 13.5 3.6 8.6 25.7 Substandard 37.6 27.0 2.0 66.6 Doubtful 0.7 — — 0.7 Total acquired loans 234.7 186.1 11.6 432.4 Total $ 10,247.3 $ 8,125.1 $ 3,032.5 $ 21,404.9 As of December 31, 2016 (in millions) Residential Home Other Total Retail: Originated loans: Low risk $ 3,016.4 $ 950.9 $ 31.1 $ 3,998.4 Moderate risk 2,538.9 663.9 7.2 3,210.0 High risk 512.0 430.1 11.7 953.8 Total originated loans 6,067.3 2,044.9 50.0 8,162.2 Acquired loans: Low risk 75.7 — — 75.7 Moderate risk 27.5 — — 27.5 High risk 46.2 27.7 0.7 74.6 Total acquired loans 149.4 27.7 0.7 177.8 Total $ 6,216.7 $ 2,072.6 $ 50.7 $ 8,340.0 As of December 31, 2015 (in millions) Commercial Commercial Equipment Total Commercial: Originated loans: Pass $ 9,438.6 $ 7,153.4 $ 2,550.0 $ 19,142.0 Special mention 130.6 121.0 119.1 370.7 Substandard 127.7 250.5 288.5 666.7 Doubtful — 1.5 — 1.5 Total originated loans 9,696.9 7,526.4 2,957.6 20,180.9 Acquired loans: Pass 260.9 175.9 6.1 442.9 Special mention 20.1 6.6 5.0 31.7 Substandard 49.1 39.8 4.6 93.5 Doubtful 1.8 — — 1.8 Total acquired loans 331.9 222.3 15.7 569.9 Total $ 10,028.8 $ 7,748.7 $ 2,973.3 $ 20,750.8 As of December 31, 2015 (in millions) Residential Home Other Total Retail: Originated loans: Low risk $ 2,579.3 $ 959.2 $ 25.8 $ 3,564.3 Moderate risk 2,208.6 651.2 7.9 2,867.7 High risk 481.5 505.1 14.8 1,001.4 Total originated loans 5,269.4 2,115.5 48.5 7,433.4 Acquired loans: Low risk 97.7 — — 97.7 Moderate risk 36.2 — — 36.2 High risk 53.7 38.2 0.9 92.8 Total acquired loans 187.6 38.2 0.9 226.7 Total $ 5,457.0 $ 2,153.7 $ 49.4 $ 7,660.1
Summarized Activity in Accretable Yield for Acquired Loan Portfolio	The following table summarizes activity in the accretable yield for the acquired loan portfolio: Years ended December 31 (in millions) 2016 2015 2014 Balance at beginning of period $ 296.0 $ 396.3 $ 639.7 Accretion (39.0 ) (55.5 ) (81.0 ) Reclassification from nonaccretable difference for loans — 1.1 6.7 Other changes in expected cash flows (2) (1.6 ) (45.9 ) (169.1 ) Balance at end of period $ 255.4 $ 296.0 $ 396.3 (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.

Goodwill and Other Acquisitio39

Goodwill and Other Acquisition-Related Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2016
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, 2014 $ 1,222.8 $ 681.9 $ 49.8 $ 1,954.5 Acquisition of Kesten-Brown — — 4.2 4.2 Balance at December 31, 2015 1,222.8 681.9 54.0 1,958.7 Acquisition of Gerstein Fisher — — 31.7 31.7 Acquisition of Eagle Insurance — — 2.3 2.3 Adjustments (0.7 ) (2.3 ) 3.0 — Balance at December 31, 2016 $ 1,222.1 $ 679.6 $ 91.0 $ 1,992.7
Other Acquisition-Related Intangible	The following is a summary of People’s United’s other acquisition-related intangible assets: 2016 2015 As of December 31 (in millions) Gross Accumulated Carrying Gross Accumulated Carrying Intangibles amortized: Trade name intangible $ 123.0 $ 50.3 $ 72.7 $ 122.7 $ 42.8 $ 79.9 Core deposit intangible 143.8 132.0 11.8 143.8 120.0 23.8 Trust relationships 42.7 25.6 17.1 42.7 22.8 19.9 Insurance relationships 38.1 32.0 6.1 36.5 31.0 5.5 Client relationships 24.4 0.3 24.1 — — — Favorable lease agreement 0.7 — 0.7 — — — Non-compete 0.4 — 0.4 — — — Total $ 373.1 $ 240.2 132.9 $ 345.7 $ 216.6 129.1 Mutual fund management contracts (not amortized) 16.5 — Total other acquisition-related $ 149.4 $ 129.1

Premises and Equipment (Tables)

Premises and Equipment (Tables)	12 Months Ended
	Dec. 31, 2016
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) 2016 2015 Land $ 38.1 $ 38.8 Buildings 265.1 267.6 Leasehold improvements 161.8 158.2 Furniture and equipment 236.2 225.3 Total 701.2 689.9 Less: Accumulated depreciation and amortization 456.7 432.1 Total premises and equipment, net $ 244.5 $ 257.8

Other Assets and Other Liabil41

Other Assets and Other Liabilities (Tables)	12 Months Ended
	Dec. 31, 2016
Text Block [Abstract]
Components of Other Assets	The components of other assets are as follows: As of December 31 (in millions) 2016 2015 Affordable housing investments (note 12) $ 195.2 $ 158.4 Leased equipment 176.9 194.4 Fair value of derivative financial instruments (notes 19 and 21) 174.0 158.2 Accrued interest receivable 101.8 90.6 Loans in process 63.9 13.1 Assets held in trust for supplemental retirement plans (note 17) 39.6 36.5 Receivables arising from securities brokerage and insurance businesses 32.0 33.7 Current income tax receivable (note 12) 29.9 26.3 Funded status of defined benefit pension plans (note 17) 29.5 26.6 Investment in joint venture (1) 21.3 22.0 Economic development investments 20.3 19.8 Other prepaid expenses 15.9 15.3 Net deferred tax asset (note 12) 9.4 1.9 Repossessed assets 7.2 9.5 REO: Residential 8.1 7.1 Commercial 4.0 5.5 Other (2) 38.2 36.6 Total other assets (3) $ 967.2 $ 855.5 (1) During the quarter ended June 30, 2014, the Bank formed a joint venture with Vantiv, Inc. to provide a comprehensive suite of payment solutions to businesses throughout the Bank’s footprint. The Bank retained a 49% minority interest in the joint venture and recognized a $20.6 million gain, net of related expenses, resulting from its formation. The gain represented the fair value of the Bank’s entire portfolio of merchant contracts that were contributed to the joint venture and which previously had a zero book basis. The investment in the joint venture is accounted for using the equity method of accounting. (2) During the quarter ended December 31, 2015, the Bank sold its payroll services business and recognized a $9.2 million gain, net of related expenses. The gain represented the fair value of the Bank’s entire portfolio of payroll services customer contracts, which previously had a zero book basis. In connection with this transaction, the Bank recorded a contingent receivable, which totaled $0.3 million and $2.8 million at December 31, 2016 and 2015, respectively. (3) As discussed in Notes 1 and 11, debt issuance costs totaling $5.6 million at December 31, 2015, previously included in other assets, are now included as a component of notes and debentures in the Consolidated Statements of Condition.
Components of Other Liabilities	The components of other liabilities are as follows: As of December 31 (in millions) 2016 2015 Fair value of derivative financial instruments (notes 19 and 21) $ 121.7 $ 109.5 Future contingent commitments for affordable housing investments (note 12) 92.5 74.9 Liabilities for supplemental retirement plans (note 17) 68.1 63.9 Accrued expenses payable (1) 68.0 43.7 Accrued employee benefits 50.6 48.4 Payables arising from securities brokerage and insurance businesses 33.0 34.7 Accrued interest payable 14.2 13.3 Other postretirement plan (note 17) 13.6 14.0 Liability for unsettled purchases of securities 5.0 5.0 Other 53.5 49.9 Total other liabilities $ 520.2 $ 457.3 (1) In connection with recent acquisitions, the Company recorded contingent payables, which totaled $21.4 million and $2.0 million at December 31, 2016 and 2015, respectively (see Note 2).

Deposits (Tables)

Deposits (Tables)	12 Months Ended
	Dec. 31, 2016
Banking and Thrift [Abstract]
Schedule of Deposits	The following is an analysis of People’s United’s total deposits by product type: 2016 2015 Amount Weighted Average Rate Amount Weighted Average Rate As of December 31 (dollars in millions) Non-interest-bearing $ 6,660.8 — % $ 6,178.6 — % Savings 4,397.7 0.14 4,199.9 0.13 Interest-bearing checking and money market 14,260.1 0.27 13,220.8 0.23 Time deposits maturing: Within 3 months 1,054.9 0.70 991.5 0.69 After 3 but within 6 months 852.4 0.75 679.6 0.86 After 6 months but within 1 year 835.2 0.75 1,915.6 1.10 After 1 but within 2 years 1,256.3 1.09 636.1 1.06 After 2 but within 3 years 142.7 1.26 153.5 0.98 After 3 but within 4 years 335.1 1.81 101.9 1.46 After 4 but within 5 years 65.5 1.03 339.6 1.81 After 5 years 0.1 0.93 0.3 2.44 Total 4,542.2 0.93 4,818.1 1.03 Total deposits $ 29,860.8 0.29 % $ 28,417.4 0.30 %
Schedule of Interest Expense on Deposits	Interest expense on deposits is summarized as follows: Years ended December 31 (in millions) 2016 2015 2014 Savings $ 9.6 $ 11.4 $ 10.9 Interest-bearing checking and money market 43.4 32.1 25.8 Time 47.9 52.0 44.2 Total $ 100.9 $ 95.5 $ 80.9

Borrowings (Tables)

Borrowings (Tables)	12 Months Ended
	Dec. 31, 2016
Debt Disclosure [Abstract]
Summary of Borrowings	People’s United’s borrowings are summarized as follows: 2016 2015 As of December 31 (dollars in millions) Amount Weighted Average Rate Amount Weighted Average Rate Fixed-rate FHLB advances maturing: Within 1 month $ 2,250.0 0.69 % $ 2,750.0 0.44 % After 1 month but within 1 year 550.0 0.77 450.0 0.57 After 1 but within 2 years 256.1 2.71 — — After 2 but within 3 years — — 258.6 2.71 After 5 years 5.0 1.34 5.2 1.34 Total FHLB advances 3,061.1 0.87 3,463.8 0.63 Federal funds purchased maturing: Within 1 month 617.0 0.71 374.0 0.32 Total federal funds purchased 617.0 0.71 374.0 0.32 Customer repurchase agreements maturing: Within 1 month 343.3 0.19 469.5 0.19 Total customer repurchase agreements 343.3 0.19 469.5 0.19 Other borrowings maturing: Within 1 year 35.4 0.55 — — Total other borrowings 35.4 0.55 — — Total borrowings $ 4,056.8 0.79 % $ 4,307.3 0.55 %
Interest Expense on Borrowings	Interest expense on borrowings consists of the following: Years ended December 31 (in millions) 2016 2015 2014 FHLB advances $ 19.3 $ 9.8 $ 9.2 Federal funds purchased 2.9 0.8 0.8 Customer repurchase agreements 0.6 0.9 1.0 Other borrowings — — 0.1 Total $ 22.8 $ 11.5 $ 11.1
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) 2016 2015 2014 FHLB advances: Balance at year end $ 3,061.1 $ 3,463.8 $ 2,291.7 Average outstanding during the year 3,093.7 2,306.6 2,593.7 Maximum outstanding at any month end 3,562.5 3,463.8 3,419.5 Average interest rate during the year 0.62 % 0.42 % 0.36 % Federal funds purchased: Balance at year end $ 617.0 $ 374.0 $ 913.0 Average outstanding during the year 568.1 411.0 471.8 Maximum outstanding at any month end 872.0 582.0 960.0 Average interest rate during the year 0.50 % 0.19 % 0.17 % Customer repurchase agreements: Balance at year end $ 343.3 $ 469.5 $ 486.0 Carrying amount of collateral securities at year end 350.2 478.9 495.7 Average outstanding during the year 337.2 463.6 482.0 Maximum outstanding at any month end 427.2 504.5 519.2 Average interest rate during the year 0.19 % 0.19 % 0.20 % Other borrowings: Balance at year end $ 35.4 $ — $ 1.0 Carrying amount of collateral securities at year end — — 1.1 Average outstanding during the year 2.8 0.6 57.1 Maximum outstanding at any month end 35.4 1.0 206.2 Average interest rate during the year 0.66 % 1.76 % 0.25 %

Notes and Debentures (Tables)

Notes and Debentures (Tables)	12 Months Ended
	Dec. 31, 2016
Brokers and Dealers [Abstract]
Schedule of Subordinated Borrowing	Notes and debentures are summarized as follows: As of December 31 (in millions) 2016 2015 People’s United Financial, Inc.: 3.65% senior notes due 2022 $ 496.5 $ 496.0 5.80% fixed-rate/floating-rate subordinated notes due 2017 125.0 123.7 People’s United Bank: 4.00% subordinated notes due 2024 408.6 413.4 Total notes and debentures $ 1,030.1 $ 1,033.1

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2016
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) 2016 2015 2014 Income tax expense applicable to pre-tax $ 128.5 $ 130.4 $ 128.9 Deferred income tax benefit applicable to items reported in total other comprehensive loss (note 16) (10.6 ) (5.3 ) (6.7 ) Total $ 117.9 $ 125.1 $ 122.2
Income Tax Effects Related to Items Recognized in Other Comprehensive Income	The components of income tax expense applicable to pre-tax Years ended December 31 (in millions) 2016 2015 2014 Current tax expense: Federal $ 109.7 $ 103.6 $ 111.9 State 15.1 12.7 10.3 Total current tax expense 124.8 116.3 122.2 Deferred tax expense (1) 3.7 14.1 6.7 Total income tax expense $ 128.5 $ 130.4 $ 128.9 (1) Includes the effect of decreases in the valuation allowance for state deferred tax assets of $1.3 million, $0.1 million and $1.2 million in 2016, 2015 and 2014, 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 35%, to actual income tax expense: Years ended December 31 (dollars in millions) 2016 2015 2014 Expected income tax expense $ 143.3 $ 136.7 $ 133.2 State income tax, net of federal tax effect 10.0 9.3 8.2 Tax-exempt (20.0 ) (16.4 ) (13.2 ) Federal income tax credits (5.3 ) (0.4 ) 0.8 Tax-exempt (2.0 ) (1.6 ) (2.0 ) Other, net 2.5 2.8 1.9 Actual income tax expense $ 128.5 $ 130.4 $ 128.9 Effective income tax rate 31.4 % 33.4 % 33.9 %
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) 2016 2015 Deferred tax assets: Leasing activities $ 122.2 $ 101.5 Allowance for loan losses and non-accrual 90.2 82.7 State tax net operating loss carryforwards, net of federal tax effect 66.3 68.0 Equity-based compensation 19.0 22.9 Unrealized loss on securities available for sale 18.7 10.8 Pension and other postretirement benefits 10.9 12.2 Unrealized loss on securities transferred to held to maturity 10.2 12.0 Other deductible temporary differences 37.1 35.1 Total deferred tax assets 374.6 345.2 Less: valuation allowance for state deferred tax assets (66.7 ) (68.0 ) Total deferred tax assets, net of the valuation allowance 307.9 277.2 Deferred tax liabilities: Tax over book depreciation (207.1 ) (185.4 ) Acquisition-related deferred tax liabilities (35.3 ) (39.9 ) Book over tax income recognized on consumer loans (18.4 ) (14.6 ) Mark-to-market (16.0 ) (7.3 ) Deferred cancellation-of-indebtedness (9.0 ) (13.4 ) Temporary differences related to merchant services joint venture (6.3 ) (6.8 ) Other taxable temporary differences (6.4 ) (7.9 ) Total deferred tax liabilities (298.5 ) (275.3 ) Net deferred tax asset $ 9.4 $ 1.9
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) 2016 2015 2014 Balance at beginning of year $ 2.7 $ 3.0 $ 3.0 Additions for tax positions taken in prior years 0.1 0.1 0.1 Reductions for tax positions taken in prior years — — — Reductions attributable to audit settlements/lapse of statute of limitations — (0.4 ) (0.1 ) Balance at end of year $ 2.8 $ 2.7 $ 3.0

Regulatory Capital Requiremen46

Regulatory Capital Requirements (Tables)	12 Months Ended
	Dec. 31, 2016
Basel III Capital [Member]
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 improvement in People’s United’s Tier 1 and Total risk-based capital ratios since December 31, 2015 reflects, in part, the issuance of preferred stock in October 2016, which qualifies as a Tier 1 capital instrument (see Note 13). The improvement in the Bank’s capital ratios since December 31, 2015 reflects equity contributions from People’s United (parent company) during 2016. The minimum capital required amounts as of December 31, 2016 and 2015 are based on the capital conservation buffer phase-in opt-out As of December 31, 2016 Minimum Capital Phase-In Classification as (dollars in millions) Amount Ratio Amount Ratio Amount Ratio Tier 1 Leverage Capital (1): People’s United $ 3,256.1 8.4 % $ 1,546.7 4.0 % $ 1,933.4 5.0 % Bank 3,430.5 8.9 1,537.0 4.0 1,921.2 5.0 CET 1 Risk-Based Capital (2): People’s United 3,012.0 9.9 1,565.2 5.125 1,985.1 6.5 Bank 3,430.5 11.3 1,562.5 5.125 1,981.8 6.5 Tier 1 Risk-Based Capital (3): People’s United 3,256.1 10.7 2,023.3 6.625 2,443.2 8.0 Bank 3,430.5 11.3 2,019.9 6.625 2,439.1 8.0 Total Risk-Based Capital (4): People’s United 3,802.9 12.5 2,634.1 8.625 3,054.0 10.0 Bank 4,062.1 13.3 2,629.7 8.625 3,048.9 10.0 As of December 31, 2015 Minimum Capital Phase-In Classification as Well-Capitalized (dollars in millions) Amount Ratio Amount Ratio Amount Ratio Tier 1 Leverage Capital (1): People’s United $ 2,898.1 8.0 % $ 1,440.6 4.0 % $ 1,800.8 5.0 % Bank 3,012.7 8.4 1,431.9 4.0 1,789.8 5.0 CET 1 Risk-Based Capital (2): People’s United 2,898.1 9.8 1,620.7 4.5 2,341.0 6.5 Bank 3,012.7 10.2 1,610.9 4.5 2,326.8 6.5 Tier 1 Risk-Based Capital (3): People’s United 2,898.1 9.8 1,778.8 6.0 2,371.7 8.0 Bank 3,012.7 10.2 1,777.3 6.0 2,369.7 8.0 Total Risk-Based Capital (4): People’s United 3,470.5 11.7 2,371.7 8.0 2,964.6 10.0 Bank 3,726.3 12.6 2,369.7 8.0 2,962.1 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 (ii) after-tax (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, 2016
Earnings Per Share [Abstract]
Basic and Diluted Earnings Per 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 Years ended December 31 (in millions, except per share data) 2016 2015 2014 Net income available to common shareholders $ 279.2 $ 260.1 $ 251.7 Dividends paid on and undistributed earnings allocated to participating securities (0.9 ) (1.1 ) (1.2 ) Earnings attributable to common shareholders $ 278.3 $ 259.0 $ 250.5 Weighted average common shares outstanding for basic EPS 303.1 300.4 298.2 Effect of dilutive equity-based awards 0.9 — 0.1 Weighted average common and common-equivalent shares for diluted EPS 304.0 300.4 298.3 Basic EPS $ 0.92 $ 0.86 $ 0.84 Diluted EPS $ 0.92 $ 0.86 $ 0.84

Comprehensive Income (Tables)

Comprehensive Income (Tables)	12 Months Ended
	Dec. 31, 2016
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 (in millions) Pension and Other Net Unrealized on Securities Net Unrealized Net Unrealized Cash Flow Hedges Total AOCL Balance at December 31, 2013 $ (85.0 ) $ (46.5 ) $ (23.3 ) $ (0.3 ) $ (155.1 ) Other comprehensive income (loss) before reclassifications (62.6 ) 44.6 — (0.6 ) (18.6 ) Amounts reclassified from AOCL (1) 4.7 (1.8 ) 1.8 0.8 5.5 Current period other comprehensive income (loss) (57.9 ) 42.8 1.8 0.2 (13.1 ) Balance at December 31, 2014 (142.9 ) (3.7 ) (21.5 ) (0.1 ) (168.2 ) Other comprehensive income (loss) before reclassifications (2.2 ) (14.0 ) — (0.7 ) (16.9 ) Amounts reclassified from AOCL (1) 5.1 — 2.0 0.8 7.9 Current period other comprehensive income (loss) 2.9 (14.0 ) 2.0 0.1 (9.0 ) Balance at December 31, 2015 (140.0 ) (17.7 ) (19.5 ) — (177.2 ) Other comprehensive income (loss) before reclassifications (9.6 ) (18.3 ) — (0.1 ) (28.0 ) Amounts reclassified from AOCL (1) 4.0 3.7 2.1 0.4 10.2 Current period other comprehensive income (loss) (5.6 ) (14.6 ) 2.1 0.3 (17.8 ) Balance at December 31, 2016 $ (145.6 ) $ (32.3 ) $ (17.4 ) $ 0.3 $ (195.0 ) (1) See the following table for details about these reclassifications.
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 from AOCL Affected Line Item in the Statement Where Net Income is Presented 2016 2015 2014 Details about components of AOCL: Amortization of pension and other postretirement plans items: Net actuarial loss $ (7.2 ) $ (9.1 ) $ (8.4 ) (1) Prior service credit 0.8 1.0 1.0 (1) (6.4 ) (8.1 ) (7.4 ) Income before income tax expense 2.4 3.0 2.7 Income tax expense (4.0 ) (5.1 ) (4.7 ) Net income Reclassification adjustment for net realized (losses) gains on securities available for sale (5.9 ) — 3.0 Income before income tax expense (2) 2.2 — (1.2 ) Income tax expense (3.7 ) — 1.8 Net income Amortization of unrealized losses on securities transferred to held to maturity (3.3 ) (3.1 ) (3.0 ) Income before income tax expense (3) 1.2 1.1 1.2 Income tax expense (2.1 ) (2.0 ) (1.8 ) Net income Amortization of unrealized gains and losses on cash flow hedges: Interest rate swaps (0.8 ) (1.3 ) (1.4 ) (4) Interest rate locks 0.1 0.1 0.1 (4) (0.7 ) (1.2 ) (1.3 ) Income before income tax expense 0.3 0.4 0.5 Income tax expense (0.4 ) (0.8 ) (0.8 ) Net income Total reclassifications for the period $ (10.2 ) $ (7.9 ) $ (5.5 ) (1) Included in the computation of net periodic benefit income (expense) reflected in compensation and benefits expense (see Note 17 for additional details). (2) Included in non-interest (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) 2016 2015 2014 Net actuarial loss and other amounts related to pension and other postretirement plans $ 85.0 $ 81.5 $ 83.2 Net unrealized loss on securities available for sale 18.8 10.3 2.2 Net unrealized loss on securities transferred to held to maturity 10.2 11.4 12.5 Net unrealized gain on derivatives accounted for as cash flow hedges (0.2 ) — — Total deferred income taxes $ 113.8 $ 103.2 $ 97.9
Other Comprehensive Income (Loss)	The following is a summary of the components of People’s United’s total other comprehensive loss: Pre-Tax After-Tax Year ended December 31, 2016 (in millions) Amount Tax Effect Amount Net actuarial gains and losses on pension and other postretirement plans: Net actuarial loss arising during the year $ (15.5 ) $ 5.9 $ (9.6 ) Reclassification adjustment for net actuarial loss included in net income 7.2 (2.7 ) 4.5 Net actuarial loss (8.3 ) 3.2 (5.1 ) Prior service credit on pension and other postretirement plans: Reclassification adjustment for prior service credit included in net income (0.8 ) 0.3 (0.5 ) Net actuarial loss and prior service credit (9.1 ) 3.5 (5.6 ) Net unrealized gains and losses on securities available for sale: Net unrealized holding losses arising during the year (29.0 ) 10.7 (18.3 ) Reclassification adjustment for net realized gains included in net income 5.9 (2.2 ) 3.7 Net unrealized losses (23.1 ) 8.5 (14.6 ) 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 3.3 (1.2 ) 2.1 Net unrealized gains 3.3 (1.2 ) 2.1 Net unrealized gains and losses on derivatives accounted for as cash flow hedges: Net unrealized losses arising during the year (0.2 ) 0.1 (0.1 ) Reclassification adjustment for net realized losses included in net income 0.7 (0.3 ) 0.4 Net unrealized gains 0.5 (0.2 ) 0.3 Total other comprehensive loss $ (28.4) $ 10.6 $ (17.8 ) Pre-Tax After-Tax Year ended December 31, 2015 (in millions) Amount Tax Effect Amount Net actuarial gains and losses on pension and other postretirement plans: Net actuarial loss arising during the year $ (3.5 ) $ 1.3 $ (2.2 ) Reclassification adjustment for net actuarial loss included in net income 9.1 (3.4 ) 5.7 Net actuarial gain 5.6 (2.1 ) 3.5 Prior service credit on pension and other postretirement plans: Reclassification adjustment for prior service credit included in net income (1.0 ) 0.4 (0.6 ) Net actuarial gain and prior service credit 4.6 (1.7 ) 2.9 Net unrealized gains and losses on securities available for sale: Net unrealized holding losses arising during the year (22.1 ) 8.1 (14.0 ) Net unrealized losses (22.1 ) 8.1 (14.0 ) 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 3.1 (1.1 ) 2.0 Net unrealized gains 3.1 (1.1 ) 2.0 Net unrealized gains and losses on derivatives accounted for as cash flow hedges: Net unrealized losses arising during the year (1.1 ) 0.4 (0.7 ) Reclassification adjustment for net realized losses included in net income 1.2 (0.4 ) 0.8 Net unrealized gains 0.1 — 0.1 Total other comprehensive loss $ (14.3 ) $ 5.3 $ (9.0 ) Pre-Tax After-Tax Year ended December 31, 2014 (in millions) Amount Tax Effect Amount Net actuarial gains and losses on pension and other postretirement plans: Net actuarial loss arising during the year $ (98.5 ) $ 35.9 $ (62.6 ) Reclassification adjustment for net actuarial loss included in net income 8.4 (3.1 ) 5.3 Net actuarial loss (90.1 ) 32.8 (57.3 ) Prior service credit on pension and other postretirement plans: Reclassification adjustment for prior service credit included in net income (1.0 ) 0.4 (0.6 ) Net actuarial loss and prior service credit (91.1 ) 33.2 (57.9 ) Net unrealized gains and losses on securities available for sale: Net unrealized holding gains arising during the year 70.9 (26.3 ) 44.6 Reclassification adjustment for net realized gains included in net income (3.0 ) 1.2 (1.8 ) Net unrealized gains 67.9 (25.1 ) 42.8 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 3.0 (1.2 ) 1.8 Net unrealized gains 3.0 (1.2 ) 1.8 Net unrealized gains and losses on derivatives accounted for as cash flow hedges: Net unrealized losses arising during the year (0.9 ) 0.3 (0.6 ) Reclassification adjustment for net realized losses included in net income 1.3 (0.5 ) 0.8 Net unrealized gains 0.4 (0.2 ) 0.2 Total other comprehensive loss $ (19.8 ) $ 6.7 $ (13.1 )

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2016
Compensation and Retirement Disclosure [Abstract]
Changes in Benefit Obligations and Plan Assets	The following table summarizes changes in the benefit obligations and plan assets of the People’s Qualified Plan, the Chittenden Qualified Plan and the Supplemental Plans (together the “Pension Plans”) and the Other Postretirement Plan. 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) 2016 2015 2016 2015 Benefit obligations: (1) Beginning of year $ 480.4 $ 515.3 $ 14.0 $ 14.6 Service cost — — 0.3 0.3 Interest cost 18.6 21.1 0.6 0.6 Actuarial loss (gain) 10.2 (36.7 ) (0.2 ) (0.6 ) Benefits paid (17.8 ) (16.6 ) (1.1 ) (0.9 ) Settlements (2.1 ) (2.7 ) — — End of year 489.3 480.4 13.6 14.0 Fair value of plan assets: Beginning of year 466.5 439.9 — — Actual return on assets 29.2 (6.4 ) — — Employer contributions (2) 2.2 52.3 1.1 0.9 Benefits paid (17.8 ) (16.6 ) (1.1 ) (0.9 ) Settlements (2.1 ) (2.7 ) — — End of year 478.0 466.5 — — Funded status at end of year $ (11.3 ) $ (13.9 ) $ (13.6 ) $ (14.0 ) Amounts recognized in the Consolidated Statements of Condition: Other assets $ 29.5 $ 26.6 $ — $ — Other liabilities (40.8 ) (40.5 ) (13.6 ) (14.0 ) Funded status at end of year $ (11.3 ) $ (13.9 ) $ (13.6 ) $ (14.0 ) (1) Represents the projected benefit obligation for the Pension Plans and the accumulated benefit obligation for the Other Postretirement Plan. (2) During the quarter ended March 31, 2015, People’s United made voluntary employer contributions of $40.0 million to the People’s Qualified Plan and $10.0 million to the Chittenden 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) 2016 2015 Accumulated benefit obligations: Qualified Plans $ 448.5 $ 439.9 Supplemental Plans 40.8 40.5 Total $ 489.3 $ 480.4 Projected benefit obligations: Qualified Plans $ 448.5 $ 439.9 Supplemental Plans 40.8 40.5 Total $ 489.3 $ 480.4
Components of Net Periodic Benefit (Income) Expense and Other Amounts	Components of net periodic benefit (income) expense and other amounts recognized in other comprehensive loss are as follows: Pension Plans Other Years ended December 31 (in millions) 2016 2015 2014 2016 2015 2014 Net periodic benefit (income) expense: Service cost $ — $ — $ — $ 0.3 $ 0.3 $ 0.1 Interest cost 18.6 21.1 21.4 0.6 0.6 0.5 Expected return on plan assets (34.6 ) (34.4 ) (32.0 ) — — — Recognized net actuarial loss 6.1 7.7 5.1 0.2 0.3 — Recognized prior service credit (0.8 ) (0.8 ) (0.8 ) — (0.2 ) (0.2 ) Settlements (1) 0.8 1.2 3.3 — — — Net periodic benefit (income) expense (9.9 ) (5.2 ) (3.0 ) 1.1 1.0 0.4 Other changes in plan assets and benefit obligations recognized in other comprehensive loss: Net actuarial loss (gain) 8.7 (4.7 ) 85.3 (0.4 ) (0.9 ) 4.8 Prior service credit 0.8 0.8 0.8 — 0.2 0.2 Total pre-tax 9.5 (3.9 ) 86.1 (0.4 ) (0.7 ) 5.0 Total recognized in net periodic benefit (income) expense and other comprehensive loss $ (0.4 ) $ (9.1 ) $ 83.1 $ 0.7 $ 0.3 $ 5.4 (1) Settlement charges are a result of lump-sum pro-rata
Pre-Tax Amounts in Accumulated Other Comprehensive Loss	The pre-tax Pension Plans Other As of December 31 (in millions) 2016 2015 2016 2015 Net actuarial loss $ 228.0 $ 219.3 $ 3.8 $ 4.2 Prior service credit (1.2 ) (2.0 ) — — Total pre-tax $ 226.8 $ 217.3 $ 3.8 $ 4.2
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 2016 2015 2014 2016 2015 2014 Weighted-average assumptions used to determine Discount rate: People’s Qualified Plan 4.41 % 4.64 % 4.20 % 4.40 % 4.60 % 4.20 % Chittenden Qualified Plan 4.16 4.45 4.00 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 periodic benefit (income) expense for the years ended December 31: Discount rate: People’s Qualified Plan 4.64 % 4.20 % 5.10 % 4.60 % 4.20 % 5.10 % Chittenden Qualified Plan 4.45 4.00 4.90 n/a n/a n/a Expected return on plan assets 7.25 7.50 8.00 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: (1) Health care cost trend rate assumed for next year n/a n/a n/a 6.50 % 6.80 % 7.05 % Rate to which the cost trend rate is assumed to decline 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 2027 2027 n/a – not applicable (1) Changes in the net periodic benefit (income) expense and the related benefit obligation arising as a result of a one-percentage-point
Schedule of Impact in 2016 Due to Change in Accounting Estimate for Qualified Plans	The impact in 2016 of the change in accounting estimate for the Qualified Plans was as follows: (dollars in millions) People’s Chittenden Discount rates used to measure net periodic benefit income in 2016: Interest cost 4.03 % 3.70 % Discount rates that would have been used to measure net periodic benefit income Interest cost 4.64 4.45 Increase in net periodic benefit income in 2016 using specific spot rates: Interest cost $ 2.5 $ 0.3
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 5 0-20 Equity securities 65 50-75 Fixed income securities 30 20-50
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 2016 2015 As of December 31 People’s Chittenden People’s Chittenden Equity securities 69 % 67 % 69 % 69 % Cash and fixed income securities 31 33 31 31 Total 100 % 100 % 100 % 100 %
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, 2016 (in millions) Level 1 Level 2 Level 3 Total Cash and cash equivalents $ 11.7 $ — $ — $ 11.7 Equity securities: Corporate 214.8 — — 214.8 Mutual funds — 114.8 — 114.8 Fixed income securities: Corporate — 102.9 — 102.9 Mutual funds — 21.4 — 21.4 U.S. Treasury and municipals — 6.8 — 6.8 Other — 5.6 — 5.6 Total $ 226.5 $ 251.5 $ — $ 478.0 Fair Value Measurements Using As of December 31, 2015 (in millions) Level 1 Level 2 Level 3 Total Cash and cash equivalents $ 26.3 $ — $ — $ 26.3 Equity securities: Corporate 215.3 — — 215.3 Mutual funds — 105.8 — 105.8 Fixed income securities: Corporate — 81.6 — 81.6 Mutual funds — 21.8 — 21.8 Municipals — 10.5 — 10.5 Other — 5.2 — 5.2 Total $ 241.6 $ 224.9 $ — $ 466.5

Stock-Based Compensation Plans

Stock-Based Compensation Plans (Tables)	12 Months Ended
	Dec. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [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, 2015 — $ — Granted 568,596 15.22 Forfeited (15,664 ) 15.22 Vested (947 ) 15.22 Unvested performance shares outstanding at December 31, 2016 551,985 $ 15.22
Stock Option Incentive Plan	The following is a summary of stock option activity under the Incentive Plans and the SOP: Shares Weighted Weighted-Average Aggregate Options outstanding at December 31, 2013 14,217,074 $ 15.43 Granted 4,953,624 13.94 Forfeited (896,003 ) 15.13 Exercised (476,290 ) 12.48 Options outstanding at December 31, 2014 17,798,405 15.11 Granted 5,221,992 14.85 Forfeited (1,290,396 ) 16.57 Exercised (2,052,577 ) 13.35 Options outstanding at December 31, 2015 19,677,424 15.13 Granted 3,187,500 14.57 Forfeited (632,869 ) 15.65 Exercised (5,676,130 ) 15.60 Options outstanding at December 31, 2016 16,555,925 $ 14.84 6.4 $ 75.2 Options exercisable at December 31, 2016 8,837,386 $ 15.08 4.7 $ 38.2 (1) Reflects only those stock options with intrinsic value at December 31, 2016.
Options Outstanding and Options Exercisable	Additional information concerning options outstanding and options exercisable at December 31, 2016 is summarized as follows: Options Outstanding Options Exercisable Weighted Average Exercise Price Range Number Remaining Exercise Number Weighted $11.53 – $13.05 1,717,527 5.7 $ 12.85 1,717,527 $ 12.85 13.42 – 15.80 12,425,506 7.6 14.51 4,706,967 14.42 16.07 – 17.76 734,089 1.8 16.85 734,089 16.85 18.10 – 21.63 1,678,803 0.8 18.45 1,678,803 18.45
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 Fair Value Unvested restricted shares outstanding at December 31, 2013 1,533,215 $ 13.12 Granted 660,617 14.01 Forfeited (95,700 ) 13.53 Vested (730,600 ) 13.22 Unvested restricted shares outstanding at December 31, 2014 1,367,532 13.47 Granted 568,273 14.88 Forfeited (80,303 ) 14.23 Vested (623,185 ) 13.33 Unvested restricted shares outstanding at December 31, 2015 1,232,317 14.14 Granted 344,812 14.66 Forfeited (41,684 ) 14.34 Vested (649,363 ) 13.79 Unvested restricted shares outstanding at December 31, 2016 886,082 $ 14.59

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2016
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, 2016 (in millions) Level 1 Level 2 Level 3 Total Financial assets: Trading account securities: U.S. Treasury $ 6.8 $ — $ — $ 6.8 Securities available for sale: U.S. Treasury and agency 859.7 — — 859.7 GSE mortgage-backed securities and CMOs — 3,550.0 — 3,550.0 Equity securities — 0.2 — 0.2 Other assets: Exchange-traded funds 32.6 — — 32.6 Fixed income securities — 4.3 — 4.3 Mutual funds 2.7 — — 2.7 Interest rate swaps — 173.1 — 173.1 Foreign exchange contracts — 0.6 — 0.6 Forward commitments to sell residential mortgage loans — 0.3 — 0.3 Total $ 901.8 $ 3,728.5 $ — $ 4,630.3 Financial liabilities: Interest rate swaps $ — $ 121.0 $ — $ 121.0 Risk participation agreements (1) — — — — Foreign exchange contracts — 0.3 — 0.3 Interest rate-lock commitments on residential mortgage loans — 0.4 — 0.4 Total $ — $ 121.7 $ — $ 121.7 Fair Value Measurements Using As of December 31, 2015 (in millions) Level 1 Level 2 Level 3 Total Financial assets: Trading account securities: U.S. Treasury $ 6.7 $ — $ — $ 6.7 Securities available for sale: U.S. Treasury and agency 362.8 — — 362.8 GSE residential mortgage-backed securities and CMOs — 4,164.7 — 4,164.7 Equity securities — 0.2 — 0.2 Other assets: Exchange-traded funds 29.4 — — 29.4 Fixed income securities — 5.1 — 5.1 Mutual funds 2.0 — — 2.0 Interest rate swaps — 157.0 — 157.0 Foreign exchange contracts — 0.6 — 0.6 Forward commitments to sell residential mortgage loans — 0.6 — 0.6 Total $ 400.9 $ 4,328.2 $ — $ 4,729.1 Financial liabilities: Interest rate swaps $ — $ 108.5 $ — $ 108.5 Risk participation agreements (1) — — — — Foreign exchange contracts — 0.2 — 0.2 Interest rate-lock commitments on residential mortgage loans — 0.8 — 0.8 Total $ — $ 109.5 $ — $ 109.5 (1) As of December 31, 2016 and 2015, the fair value of risk participation agreements totaled less than $0.1 million (see Note 21).
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 Fair Value Measurements Using As of December 31, 2016 (in millions) Level 1 Level 2 Level 3 Total Loans held for sale (1) $ — $ 39.3 $ — $ 39.3 Impaired loans (2) — — 55.9 55.9 REO and repossessed assets (3) — — 19.3 19.3 Total $ — $ 39.3 $ 75.2 $ 114.5 Fair Value Measurements Using As of December 31, 2015 (in millions) Level 1 Level 2 Level 3 Total Loans held for sale (1) $ — $ 34.5 $ — $ 34.5 Impaired loans (2) — — 49.1 49.1 REO and repossessed assets (3) — — 22.1 22.1 Total $ — $ 34.5 $ 71.2 $ 105.7 (1) Consists of residential mortgage loans; no fair value adjustments were recorded for the years ended December 31, 2016 and 2015. (2) 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 $40.8 million of Commercial loans and $15.1 million of Retail loans at December 31, 2016. The provision for loan losses on impaired loans totaled $3.8 million and $6.7 million for the years ended December 31, 2016 and 2015, respectively. (3) Represents: (i) $8.1 million of residential REO; (ii) $4.0 million of commercial REO; and (iii) $7.2 million of repossessed assets at December 31, 2016. Charge-offs to the allowance for loan losses related to loans that were transferred to REO or repossessed assets totaled $3.7 million and $1.8 million for the years ended December 31, 2016 and 2015, respectively. Write downs and net loss on sale of foreclosed/repossessed assets charged to non-interest
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 Carrying Amount Estimated Fair Value As of December 31, 2016 (in millions) Level 1 Level 2 Level 3 Total Financial assets: Cash and due from banks $ 432.4 $ 432.4 $ — $ — $ 432.4 Short-term investments 181.7 — 181.7 — 181.7 Securities held to maturity 2,005.4 — 2,011.2 1.5 2,012.7 FHLB and FRB stock 315.8 — 315.8 — 315.8 Total loans, net (1) 29,459.7 — 6,028.4 23,238.1 29,266.5 Financial liabilities: Time deposits 4,542.2 — 4,539.7 — 4,539.7 Other deposits 25,318.6 — 25,318.6 — 25,318.6 FHLB advances 3,061.1 — 3,064.4 — 3,064.4 Federal funds purchased 617.0 — 617.0 — 617.0 Customer repurchase agreements 343.3 — 343.3 — 343.3 Other borrowings 35.4 — 35.4 — 35.4 Notes and debentures 1,030.1 — 1,000.0 — 1,000.0 (1) Excludes impaired loans totaling $55.9 million measured at fair value on a non-recurring Carrying Amount Estimated Fair Value As of December 31, 2015 (in millions) Level 1 Level 2 Level 3 Total Financial assets: Cash and due from banks $ 334.8 $ 334.8 $ — $ — $ 334.8 Short-term investments 380.5 — 380.5 — 380.5 Securities held to maturity 1,609.6 — 1,661.0 1.5 1,662.5 FHLB and FRB stock 305.4 — 305.4 — 305.4 Total loans, net (1) 28,150.8 — 5,315.3 22,893.7 28,209.0 Financial liabilities: Time deposits 4,818.1 — 4,836.5 — 4,836.5 Other deposits 23,599.3 — 23,599.3 — 23,599.3 FHLB advances 3,463.8 — 3,468.7 — 3,468.7 Customer repurchase agreements 469.5 — 469.5 — 469.5 Federal funds purchased 374.0 — 374.0 — 374.0 Notes and debentures 1,033.1 — 1,012.9 — 1,012.9 (1) Excludes impaired loans totaling $49.1 million measured at fair value on a non-recurring

Financial Instruments (Tables)

Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2016
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) 2016 2015 Lending-Related Financial Instruments: (1) Loan origination commitments and unadvanced lines of credit: Commercial and industrial $ 4,029.6 $ 3,337.0 Home equity and other consumer 2,800.7 2,558.4 Commercial real estate 701.6 831.0 Equipment financing 179.9 241.0 Residential mortgage 69.6 93.3 Letters of credit: Stand-by 105.6 121.5 Commercial 3.6 3.4 Derivative Financial Instruments: (2) Interest rate swaps: For market risk management 500.0 500.0 For commercial customers: Customer 5,612.2 4,644.8 Institutional counterparties 5,620.2 4,644.8 Risk participation agreements 251.9 244.4 Foreign exchange contracts 101.2 56.7 Forward commitments to sell residential mortgage loans 48.6 44.7 Interest rate-lock commitments on residential mortgage loans 57.0 65.4 (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 Hedge Notional Amounts Assets Liabilities As of December 31 (in millions) 2016 2015 2016 2015 2016 2015 Derivatives Not Designated as Hedging Interest rate swaps: Commercial customers N/A $ 5,612.2 $ 4,644.8 $ 93.9 $ 130.9 $ 46.9 $ 2.6 Institutional counterparties N/A 5,620.2 4,644.8 65.6 7.2 74.0 105.3 Risk participation agreements (2) N/A 251.9 244.4 — — — — Foreign exchange contracts N/A 101.2 56.7 0.6 0.6 0.3 0.2 Forward commitments to sell residential mortgage loans N/A 48.6 44.7 0.3 0.6 — — Interest rate-lock commitments on residential mortgage loans N/A 57.0 65.4 — — 0.4 0.8 Total 160.4 139.3 121.6 108.9 Derivatives Designated as Hedging Instruments: Interest rate swaps: Subordinated notes Cash flow 125.0 125.0 — — 0.1 0.6 Subordinated notes Fair value 375.0 375.0 13.6 18.9 — — Total 13.6 18.9 0.1 0.6 Total fair value of derivatives $ 174.0 $ 158.2 $ 121.7 $ 109.5 (1) Assets are recorded in other assets and liabilities are recorded in other liabilities. (2) Fair value totaled less than $0.1 million at both dates.
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 Amount of Pre-Tax Amount of Pre-Tax Type of Hedge Recognized in Earnings (1) Recognized in AOCL Years ended December 31 (in millions) 2016 2015 2014 2016 2015 2014 Derivatives Not Designated as Hedging Instruments: Interest rate swaps: Commercial customers N/A $ (11.1 ) $ 104.8 $ 165.4 $ — $ — $ — Institutional counterparties N/A 24.8 (90.3 ) (156.9 ) — — — Foreign exchange contracts N/A (0.6 ) 0.2 0.4 — — — Risk participation agreements N/A 0.5 (0.2 ) 0.1 — — — Forward commitments to sell residential mortgage loans N/A (0.2 ) 0.1 0.4 — — — Interest rate-lock commitments on residential mortgage loans N/A 0.3 (0.1 ) (0.5 ) — — — Total 13.7 14.5 8.9 — — — Derivatives Designated as Hedging Instruments: Interest rate swaps Cash flow (0.8 ) (1.3 ) (1.4 ) (0.2 ) (1.1 ) (0.9 ) Interest rate locks Cash flow 0.1 0.1 0.1 — — — Interest rate swaps Fair value 7.5 9.3 5.2 — — — Total 6.8 8.1 3.9 (0.2 ) (1.1 ) (0.9 ) Total $ 20.5 $ 22.6 $ 12.8 $ (0.2 ) $ (1.1 ) $ (0.9 ) (1) Amounts recognized in earnings are recorded in interest income, interest expense or other non-interest non-interest

Balance Sheet Offsetting (Table

Balance Sheet Offsetting (Tables)	12 Months Ended
	Dec. 31, 2016
Text Block [Abstract]
Summary of Gross Presentation, Financial Instruments that are Eligible for Offset Not Offset in Consolidated Statement of Condition	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 Amount Gross Amount Net Amount Gross Amounts Not Offset As of December 31, 2016 (in millions) Financial Collateral Net Amount Financial assets: Interest rate swaps: Counterparty A $ 1.9 $ — $ 1.9 $ (1.9 ) $ — $ — Counterparty B 1.0 — 1.0 (1.0 ) — — Counterparty C 1.7 — 1.7 (1.7 ) — — Counterparty D 3.4 — 3.4 (3.4 ) — — Counterparty E 69.6 — 69.6 (50.0 ) (19.6 ) — Other counterparties 1.6 — 1.6 (0.3 ) (1.3 ) — Foreign exchange contracts 0.6 — 0.6 — — 0.6 Total $ 79.8 $ — $ 79.8 $ (58.3 ) $ (20.9 ) $ 0.6 Financial liabilities: Interest rate swaps: Counterparty A $ 4.3 $ — $ 4.3 $ (1.9 ) $ (2.4 ) $ — Counterparty B 7.7 — 7.7 (1.0 ) (6.7 ) — Counterparty C 3.4 — 3.4 (1.7 ) (1.1 ) 0.6 Counterparty D 6.9 — 6.9 (3.4 ) (1.7 ) 1.8 Counterparty E 50.0 — 50.0 (50.0 ) — — Other counterparties 1.8 — 1.8 (0.3 ) (1.5 ) — Foreign exchange contracts 0.3 — 0.3 — — 0.3 Total $ 74.4 $ — $ 74.4 $ (58.3 ) $ (13.4 ) $ 2.7 Gross Amount Gross Amount Net Amount Gross Amounts Not Offset As of December 31, 2015 (in millions) Financial Collateral Net Amount Financial assets: Interest rate swaps: Counterparty A $ 0.6 $ — $ 0.6 $ (0.6 ) $ — $ — Counterparty B 0.7 — 0.7 (0.7 ) — — Counterparty C 0.6 — 0.6 (0.6 ) — — Counterparty D 0.7 — 0.7 (0.7 ) — — Counterparty E 22.6 — 22.6 (22.6 ) — — Other counterparties 0.8 — 0.8 (0.7 ) — 0.1 Foreign exchange contracts 0.6 — 0.6 — — 0.6 Total $ 26.6 $ — $ 26.6 $ (25.9 ) $ — $ 0.7 Financial liabilities: Interest rate swaps: Counterparty A $ 8.4 $ — $ 8.4 $ (0.6 ) $ (7.8 ) $ — Counterparty B 10.4 — 10.4 (0.7 ) (9.7 ) — Counterparty C 5.1 — 5.1 (0.6 ) (4.5 ) — Counterparty D 8.9 — 8.9 (0.7 ) (7.3 ) 0.9 Counterparty E 69.5 — 69.5 (22.6 ) (46.9 ) — Other counterparties 3.6 — 3.6 (0.7 ) (2.9 ) — Foreign exchange contracts 0.2 — 0.2 — — 0.2 Total $ 106.1 $ — $ 106.1 $ (25.9 ) $ (79.1 ) $ 1.1

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2016
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, 2016 (in millions) Commercial Retail Total Treasury Other Total Net interest income (loss) $ 566.5 $ 347.5 $ 914.0 $ 87.6 $ (29.4 ) $ 972.2 Provision for loan losses 39.3 13.0 52.3 — (15.7 ) 36.6 Total non-interest 156.4 169.0 325.4 9.2 8.1 342.7 Total non-interest 322.8 508.9 831.7 9.8 27.3 868.8 Income (loss) before income tax expense (benefit) 360.8 (5.4 ) 355.4 87.0 (32.9 ) 409.5 Income tax expense (benefit) 113.4 (1.7 ) 111.7 27.5 (10.7 ) 128.5 Net income (loss) $ 247.4 $ (3.7 ) $ 243.7 $ 59.5 $ (22.2 ) $ 281.0 Average total assets $ 22,691.1 $ 8,945.8 $ 31,636.9 $ 7,443.1 $ 704.3 $ 39,784.3 Average total liabilities 6,733.7 19,207.3 25,941.0 8,628.7 355.2 34,924.9 Year ended December 31, 2015 (in millions) Commercial Retail Total Treasury Other Total Net interest income (loss) $ 551.6 $ 344.6 $ 896.2 $ 64.4 $ (28.5 ) $ 932.1 Provision for loan losses 47.7 15.2 62.9 — (29.5 ) 33.4 Total non-interest 162.0 169.7 331.7 11.1 9.6 352.4 Total non-interest 313.2 520.2 833.4 6.9 20.3 860.6 Income (loss) before income tax expense (benefit) 352.7 (21.1 ) 331.6 68.6 (9.7 ) 390.5 Income tax expense (benefit) 117.9 (7.0 ) 110.9 22.9 (3.4 ) 130.4 Net income (loss) $ 234.8 $ (14.1 ) $ 220.7 $ 45.7 $ (6.3 ) $ 260.1 Average total assets $ 21,465.7 $ 8,478.1 $ 29,943.8 $ 6,399.3 $ 583.8 $ 36,926.9 Average total liabilities 5,483.2 19,235.8 24,719.0 7,188.4 322.2 32,229.6 Year ended December 31, 2014 (in millions) Commercial Retail Total Treasury Other Total Net interest income (loss) $ 516.0 $ 408.0 $ 924.0 $ 10.7 $ (22.8 ) $ 911.9 Provision for loan losses 47.6 16.8 64.4 — (23.8 ) 40.6 Total non-interest 141.4 167.4 308.8 12.4 29.6 350.8 Total non-interest 275.7 528.0 803.7 6.2 31.6 841.5 Income (loss) before income tax expense (benefit) 334.1 30.6 364.7 16.9 (1.0 ) 380.6 Income tax expense (benefit) 113.1 10.3 123.4 5.8 (0.3 ) 128.9 Net income (loss) $ 221.0 $ 20.3 $ 241.3 $ 11.1 $ (0.7 ) $ 251.7 Average total assets $ 19,338.5 $ 8,514.8 $ 27,853.3 $ 5,261.2 $ 652.6 $ 33,767.1 Average total liabilities 4,275.1 19,109.2 23,384.3 5,418.0 339.4 29,141.7

Parent Company Financial Info55

Parent Company Financial Information (Tables) - People's United Financial, Inc. [Member]	12 Months Ended
	Dec. 31, 2016
Condensed Statements of Condition	CONDENSED STATEMENTS OF CONDITION As of December 31 (in millions) 2016 2015 Assets: Cash at bank subsidiary $ 308.7 $ 170.2 Total cash and cash equivalents 308.7 170.2 Securities available for sale, at fair value 75.3 201.4 Advances to bank subsidiary — 100.0 Investments in subsidiaries: Bank subsidiary 5,119.2 4,649.2 Non-bank 0.9 0.8 Goodwill 197.1 197.1 Due from bank subsidiary 36.5 8.1 Other assets 29.9 28.4 Total assets $ 5,767.6 $ 5,355.2 Liabilities and Stockholders’ Equity: Notes and debentures $ 621.5 $ 619.7 Other liabilities 4.2 3.9 Stockholders’ equity 5,141.9 4,731.6 Total liabilities and stockholders’ equity $ 5,767.6 $ 5,355.2
Condensed Statements of Income	CONDENSED STATEMENTS OF INCOME Years ended December 31 (in millions) 2016 2015 2014 Revenues: Interest income: Securities $ 3.4 $ 1.1 $ 0.4 Advances to bank subsidiary 1.0 4.4 4.4 Total interest income 4.4 5.5 4.8 Dividend from bank subsidiary 271.0 245.0 244.0 Security gain — — 2.3 Other non-interest 14.8 4.2 1.2 Total revenues 290.2 254.7 252.3 Expenses: Interest on notes and debentures 22.5 22.5 22.4 Non-interest 9.6 2.8 6.1 Total expenses 32.1 25.3 28.5 Income before income tax benefit and 258.1 229.4 223.8 Income tax benefit (5.0 ) (5.5 ) (6.6 ) Income before subsidiaries undistributed income 263.1 234.9 230.4 Subsidiaries undistributed income 17.9 25.2 21.3 Net income $ 281.0 $ 260.1 $ 251.7
Condensed Statements of Comprehensive Income	CONDENSED STATEMENTS OF COMPREHENSIVE INCOME Years ended December 31 (in millions) 2016 2015 2014 Net income $ 281.0 $ 260.1 $ 251.7 Other comprehensive loss, net of tax: Net unrealized losses on securities available for sale (0.1 ) (0.3 ) — Net unrealized gains on derivatives accounted for 0.3 0.1 0.2 Other comprehensive loss of bank subsidiary (18.0 ) (8.8 ) (13.3 ) Total other comprehensive loss, net of tax (17.8 ) (9.0 ) (13.1 ) Total comprehensive income $ 263.2 $ 251.1 $ 238.6
Condensed Statements of Cash Flows	CONDENSED STATEMENTS OF CASH FLOWS Years ended December 31 (in millions) 2016 2015 2014 Cash Flows from Operating Activities: Net income $ 281.0 $ 260.1 $ 251.7 Adjustments to reconcile net income to net cash provided Subsidiaries undistributed income (17.9 ) (25.2 ) (21.3 ) Security gain — — (2.3 ) Net change in other assets and other liabilities (21.5 ) (0.4 ) 0.2 Net cash provided by operating activities 241.6 234.5 228.3 Cash Flows from Investing Activities: Proceeds from principal repayments and maturities 1.4 1.2 — Proceeds from sales of securities available for sale 200.4 — 5.0 Purchases of securities available for sale (76.0 ) (202.9 ) — Increase in investment in bank subsidiary (450.0 ) — — Decrease (increase) in advances to bank subsidiary 100.0 310.0 (57.0 ) Net cash (used in) provided by investing activities (224.2 ) 108.3 (52.0 ) Cash Flows from Financing Activities: Proceeds from issuance of preferred stock, net 244.1 — — Cash dividends paid on common stock (205.7 ) (201.2 ) (196.9 ) Cash dividend paid on preferred stock (1.8 ) — — Common stock repurchases (3.4 ) (3.2 ) (3.0 ) Proceeds from stock options exercised, including 87.9 27.5 6.0 Net cash provided by (used in) financing activities 121.1 (176.9 ) (193.9 ) Net increase (decrease) in cash and cash equivalents 138.5 165.9 (17.6 ) Cash and cash equivalents at beginning of year 170.2 4.3 21.9 Cash and cash equivalents at end of year $ 308.7 $ 170.2 $ 4.3

Selected Quarterly Financial 56

Selected Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Data	The following table presents People’s United’s quarterly financial data for 2016 and 2015: 2016 2015 (dollars in millions, except per share data) First Second Third Fourth First Second Third Fourth Interest and dividend income $ 278.0 $ 278.5 $ 284.5 $ 286.3 $ 260.3 $ 264.5 $ 269.9 $ 274.2 Interest expense 37.9 38.5 39.2 39.5 32.2 34.1 35.1 35.4 Net interest income 240.1 240.0 245.3 246.8 228.1 230.4 234.8 238.8 Provision for loan losses 10.5 10.0 8.4 7.7 9.8 7.7 6.2 9.7 Net interest income after provision for loan losses 229.6 230.0 236.9 239.1 218.3 222.7 228.6 229.1 Non-interest 82.3 85.4 90.8 84.2 89.0 83.0 87.1 93.3 Non-interest 217.3 212.9 221.4 217.2 217.6 211.8 214.2 217.0 Income before income tax expense 94.6 102.5 106.3 106.1 89.7 93.9 101.5 105.4 Income tax expense 31.7 34.0 32.6 30.2 30.5 32.2 33.1 34.6 Net income 62.9 68.5 73.7 75.9 59.2 61.7 68.4 70.8 Preferred stock dividend — — — 1.8 — — — — Net income available to common shareholders $ 62.9 $ 68.5 $ 73.7 $ 74.1 $ 59.2 $ 61.7 $ 68.4 $ 70.8 Common Share Data: Basic EPS $ 0.21 $ 0.23 $ 0.24 $ 0.24 $ 0.20 $ 0.20 $ 0.23 $ 0.23 Diluted EPS 0.21 0.23 0.24 0.24 0.20 0.20 0.23 0.23 Common dividends paid 50.6 51.7 51.7 51.7 49.5 50.5 50.6 50.6 Dividends paid per common share 0.1675 0.17 0.17 0.17 0.165 0.1675 0.1675 0.1675 Common dividend payout ratio 80.6 % 75.4 % 70.1 % 69.8 % 83.7 % 81.8 % 73.9 % 71.5 % Stock price: High $ 16.27 $ 16.68 $ 16.40 $ 20.13 $ 15.45 $ 16.64 $ 16.95 $ 16.93 Low 13.62 13.80 14.22 15.28 13.97 14.92 14.69 15.00 Weighted average common shares outstanding (in millions): Basic 301.86 302.48 302.88 305.17 299.15 300.09 301.00 301.38 Diluted 301.86 302.48 303.24 306.23 299.15 300.09 301.00 301.38

Summary of Significant Accoun57

Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2016USD ($)Rating	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)
Summary Of Significant Accounting Policies [Line Items]
Accruing interest total	$ 0	$ 0	$ 0
Number of days of non accrual status	90 days
Collateral values/LTV ratios, minimum	70.00%
Borrower credit scores, minimum | Rating	680
Non accrual commercial loans	$ 750,000
Trade Name Intangible [Member] | Straight Line Amortization [Member]
Summary Of Significant Accounting Policies [Line Items]
Finite-lived intangible assets, useful life, (in years)	20 years
Trade Name Intangible [Member] | Accelerated Amortization [Member]
Summary Of Significant Accounting Policies [Line Items]
Finite-lived intangible assets, useful life, (in years)	5 years
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
Minimum [Member] | Core Deposit Intangibles [Member]
Summary Of Significant Accounting Policies [Line Items]
Finite-lived intangible assets, useful life, (in years)	7 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] | 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 - Additional Infor

Acquisitions - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended			12 Months Ended
	Nov. 30, 2016	Apr. 30, 2016	Oct. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Contingent consideration				$ 21.4	$ 2
Goodwill				1,992.7	1,958.7	$ 1,954.5
Other acquisition-related intangible assets				149.4	129.1
Tax deductible goodwill amount				77.9	24.1
People's United Financial, Inc. [Member]
Business Acquisition [Line Items]
Goodwill				197.1	$ 197.1
Gerstein Fisher & Associates, Inc [Member]
Business Acquisition [Line Items]
Assets under management, carrying amount	$ 3,000
Business acquisition, date of acquisition agreement	Nov. 30, 2016
Cash	$ 57.4
Contingent consideration	18.3
Goodwill	31.7
Other assets	1.7
Gerstein Fisher & Associates, Inc [Member] | People's United Financial, Inc. [Member]
Business Acquisition [Line Items]
Assets under management, carrying amount	21,000
Assets under discretionary management	8,000
Gerstein Fisher & Associates, Inc [Member] | Professional and Outside Services [Member]
Business Acquisition [Line Items]
Merger-related expenses				$ 1.9
Gerstein Fisher & Associates, Inc [Member] | Trade Name Intangible [Member]
Business Acquisition [Line Items]
Other acquisition-related intangible assets	42.3
Gerstein Fisher & Associates, Inc [Member] | Customer Relationships [Member]
Business Acquisition [Line Items]
Other acquisition-related intangible assets	42.3
Gerstein Fisher & Associates, Inc [Member] | Non-compete, Favorable Lease and Fund Management Contracts [Member]
Business Acquisition [Line Items]
Other acquisition-related intangible assets	$ 42.3
Eagle Insurance Group, LLC [Member]
Business Acquisition [Line Items]
Cash		$ 2.4
Contingent consideration		1.5
Goodwill		2.3
Eagle Insurance Group, LLC [Member] | Insurance Relationships [Member]
Business Acquisition [Line Items]
Other acquisition-related intangible assets		$ 1.6
Kesten Brown [Member]
Business Acquisition [Line Items]
Cash			$ 10.2
Contingent consideration			2
Goodwill			7.1
Other assets			0.1
Kesten Brown [Member] | Insurance Relationships [Member]
Business Acquisition [Line Items]
Other acquisition-related intangible assets			$ 5

Cash and Short-Term Investmen59

Cash and Short-Term Investments - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Cash and Cash Equivalents [Line Items]
Cash at bank subsidiary	$ 91.8	$ 86
Federal Reserve Bank of New York [Member]
Cash and Cash Equivalents [Line Items]
Federal funds sold and yield	0.75%	0.50%

Cash and Short-Term Investmen60

Cash and Short-Term Investments - Cash and Short-Term Investments (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Cash and Cash Equivalents [Abstract]
Interest-bearing deposits at the FRB-NY	$ 169.8	$ 333.7
Money market mutual funds	7.9	8
Other	4	38.8
Total short-term investments	$ 181.7	$ 380.5

Securities - Available-for-Sale

Securities - Available-for-Sale and Held-to-Maturity Securities Gains (Losses) (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Investment Holdings [Line Items]
Amortized Cost	$ 4,463.2	$ 4,555.2
Gross Unrealized Gains	15.3	22.5
Gross Unrealized Losses	(68.6)	(50)
Fair Value	4,409.9	4,527.7
Held to maturity Securities, Amortized Cost	2,005.4	1,609.6
Securities held to maturity, Gross Unrealized Gains	33.9	55.8
Securities held to maturity, Gross Unrealized Losses	(26.7)	(2.9)
Total securities held to maturity, Fair Value	2,012.6	1,662.5
U.S. Treasury and Agency [Member]
Investment Holdings [Line Items]
Amortized Cost	889.9	363.7
Gross Unrealized Gains	0.3	0.2
Gross Unrealized Losses	(30.5)	(1.1)
Fair Value	859.7	362.8
GSE Residential Mortgage-Backed Securities and CMOs [Member]
Investment Holdings [Line Items]
Amortized Cost	3,573.1	4,191.3
Gross Unrealized Gains	15	22.3
Gross Unrealized Losses	(38.1)	(48.9)
Fair Value	3,550	4,164.7
Held to maturity Securities, Amortized Cost	500.8	588.5
Securities held to maturity, Gross Unrealized Losses	(3.2)	(2.8)
Total securities held to maturity, Fair Value	497.6	585.7
Debt Securities [Member]
Investment Holdings [Line Items]
Amortized Cost	4,463	4,555
Gross Unrealized Gains	15.3	22.5
Gross Unrealized Losses	(68.6)	(50)
Fair Value	4,409.7	4,527.5
Equity Securities [Member]
Investment Holdings [Line Items]
Amortized Cost	0.2	0.2
Fair Value	0.2	0.2
State and Municipal [Member]
Investment Holdings [Line Items]
Held to maturity Securities, Amortized Cost	1,499.1	1,019.6
Securities held to maturity, Gross Unrealized Gains	33.9	55.8
Securities held to maturity, Gross Unrealized Losses	(23.5)	(0.1)
Total securities held to maturity, Fair Value	1,509.5	1,075.3
Other [Member]
Investment Holdings [Line Items]
Held to maturity Securities, Amortized Cost	5.5	1.5
Total securities held to maturity, Fair Value	$ 5.5	$ 1.5

Securities - Additional Informa

Securities - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2016USD ($)SecuritiesSecurity	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)
Investment [Line Items]
Security available for sale with a fair value pledged with collateral for public deposits	$ 1,830,000,000	$ 1,640,000,000
Number of securities available for sale | Security	125
Number of securities held to maturity | Securities	482
Total number of securities owned | Security	1,684
Percentage of securities available for sale	36.00%
Available for sale of securities gross unrealized losses	$ 68,600,000	50,000,000
Held to maturity securities gross unrealized losses	26,700,000
Impairment losses on securities recognized in earnings	0	0	$ 0
Amortized cost of mortgage-backed securities	4,463,000,000
Net security (losses) gains	(5,900,000)		3,000,000
Impairment of investments	0
Dividend income on capital stock	$ 140,300,000	121,500,000	96,800,000
Federal Reserve Bank stock percentage	6.00%
Federal Reserve Bank of New York [Member]
Investment [Line Items]
Acquired shares of capital stock	$ 149,500,000	140,100,000
Dividend income on capital stock	3,100,000	7,100,000
Maximum [Member]
Investment [Line Items]
Debt securities with unrealized losses	100,000
Net gains and losses on trading account securities	100,000	100,000	100,000
Investment in Federal Home Loan Bank Stock [Member]
Investment [Line Items]
Dividend income on capital stock	5,800,000	4,600,000	$ 2,800,000
State and Municipal [Member]
Investment [Line Items]
Held to maturity securities gross unrealized losses	$ 23,500,000	100,000
Available for sale securities average maturity period	14 years
GSE Residential Mortgage-Backed Securities and CMOs [Member]
Investment [Line Items]
Available for sale of securities gross unrealized losses	$ 38,100,000	48,900,000
Held to maturity securities gross unrealized losses	$ 3,200,000	2,800,000
Available for sale securities average maturity period	12 years
Amortized cost of mortgage-backed securities	$ 3,573,100,000
U.S. Treasury and CMO Securities [Member]
Investment [Line Items]
Amortized cost of mortgage-backed securities	403,000,000
Net security (losses) gains	5,900,000
Gain (loss) on sales of Mortgage Backed Securities	6,100,000
FHLB of Boston [Member]
Investment [Line Items]
Acquired shares of capital stock	155,000,000	154,000,000
FHLB of New York [Member]
Investment [Line Items]
Acquired shares of capital stock	$ 11,300,000	$ 11,300,000

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, 2016	Dec. 31, 2015
Investment [Line Items]
Available for Sale, Amortized Cost, Within 1 year	$ 1
Available for Sale, Amortized Cost, After 1 but within 5 years	187.8
Available for Sale, Amortized Cost, After 5 but within 10 years	1,571.8
Available for Sale, Amortized Cost, After 10 years	2,702.4
Available for Sale, Amortized Cost, Total	4,463
Available for Sale, Fair Value, Within 1 year	1
Available for Sale, Fair Value, After 1 but within 5 years	186.1
Available for Sale, Fair Value, After 5 but within 10 years	1,557.1
Available for Sale, Fair Value, After 10 years	2,665.5
Available for Sale, Fair Value, Total	$ 4,409.7
Available for Sale, FTE Yield, Within 1 year	0.56%
Available for Sale, FTE Yield, After 1 but within 5 years	1.31%
Available for Sale, FTE Yield, After 5 but within 10 years	1.94%
Available for Sale, FTE Yield, After 10 years	1.78%
Available for Sale, FTE Yield, Total	1.82%
Held to Maturity, Amortized Cost, Within 1 year	$ 6.1
Held to Maturity, Amortized Cost, After 1 but within 5 years	26.9
Held to Maturity, Amortized Cost, After 5 but within 10 years	369
Held to Maturity, Amortized Cost, After 10 years	1,603.4
Held to maturity Securities, Amortized Cost	2,005.4	$ 1,609.6
Held to Maturity, Fair Value, Within 1 year	6.1
Held to Maturity, Fair Value, After 1 but within 5 years	27.2
Held to Maturity, Fair Value, After 5 but within 10 years	383.3
Held to Maturity, Fair Value, After 10 years	1,596
Held to Maturity, Fair Value, Total	$ 2,012.6	1,662.5
Held to Maturity, FTE Yield, Within 1 year	3.86%
Held to Maturity, FTE Yield, After 1 but within 5 years	4.98%
Held to Maturity, FTE Yield, After 5 but within 10 years	3.37%
Held to Maturity, FTE Yield, After 10 years	3.62%
Held to Maturity, FTE Yield, Total	3.59%
U.S. Treasury and Agency [Member]
Investment [Line Items]
Available for Sale, Amortized Cost, Within 1 year	$ 1
Available for Sale, Amortized Cost, After 1 but within 5 years	187.8
Available for Sale, Amortized Cost, After 5 but within 10 years	701.1
Available for Sale, Amortized Cost, Total	889.9
Available for Sale, Fair Value, Within 1 year	1
Available for Sale, Fair Value, After 1 but within 5 years	186.1
Available for Sale, Fair Value, After 5 but within 10 years	672.6
Available for Sale, Fair Value, Total	$ 859.7
Available for Sale, FTE Yield, Within 1 year	0.56%
Available for Sale, FTE Yield, After 1 but within 5 years	1.31%
Available for Sale, FTE Yield, After 5 but within 10 years	1.38%
Available for Sale, FTE Yield, Total	1.36%
GSE Residential Mortgage-Backed Securities and CMOs [Member]
Investment [Line Items]
Available for Sale, Amortized Cost, After 5 but within 10 years	$ 870.7
Available for Sale, Amortized Cost, After 10 years	2,702.4
Available for Sale, Amortized Cost, Total	3,573.1
Available for Sale, Fair Value, After 5 but within 10 years	884.5
Available for Sale, Fair Value, After 10 years	2,665.5
Available for Sale, Fair Value, Total	$ 3,550
Available for Sale, FTE Yield, After 5 but within 10 years	2.40%
Available for Sale, FTE Yield, After 10 years	1.78%
Available for Sale, FTE Yield, Total	1.93%
Held to Maturity, Amortized Cost, After 10 years	$ 500.8
Held to maturity Securities, Amortized Cost	500.8	588.5
Held to Maturity, Fair Value, After 10 years	497.6
Held to Maturity, Fair Value, Total	$ 497.6	585.7
Held to Maturity, FTE Yield, After 10 years	2.05%
Held to Maturity, FTE Yield, Total	2.05%
State and Municipal [Member]
Investment [Line Items]
Held to Maturity, Amortized Cost, Within 1 year	$ 4.6
Held to Maturity, Amortized Cost, After 1 but within 5 years	26.9
Held to Maturity, Amortized Cost, After 5 but within 10 years	365
Held to Maturity, Amortized Cost, After 10 years	1,102.6
Held to maturity Securities, Amortized Cost	1,499.1	1,019.6
Held to Maturity, Fair Value, Within 1 year	4.6
Held to Maturity, Fair Value, After 1 but within 5 years	27.2
Held to Maturity, Fair Value, After 5 but within 10 years	379.3
Held to Maturity, Fair Value, After 10 years	1,098.4
Held to Maturity, Fair Value, Total	$ 1,509.5	1,075.3
Held to Maturity, FTE Yield, Within 1 year	4.42%
Held to Maturity, FTE Yield, After 1 but within 5 years	4.98%
Held to Maturity, FTE Yield, After 5 but within 10 years	3.35%
Held to Maturity, FTE Yield, After 10 years	4.34%
Held to Maturity, FTE Yield, Total	4.11%
Other [Member]
Investment [Line Items]
Held to Maturity, Amortized Cost, Within 1 year	$ 1.5
Held to Maturity, Amortized Cost, After 5 but within 10 years	4
Held to maturity Securities, Amortized Cost	5.5	1.5
Held to Maturity, Fair Value, Within 1 year	1.5
Held to Maturity, Fair Value, After 5 but within 10 years	4
Held to Maturity, Fair Value, Total	$ 5.5	$ 1.5
Held to Maturity, FTE Yield, Within 1 year	2.10%
Held to Maturity, FTE Yield, After 5 but within 10 years	5.00%
Held to Maturity, FTE Yield, Total	4.21%

Securities - Continuous Unreali

Securities - Continuous Unrealized Loss Position on Available-for-Sale and Held-to-Maturities Securities (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Continuous Unrealized Loss Position, Less Than 12 Months, Fair Value	$ 4,247.2	$ 3,155.1
Continuous Unrealized Loss Position, Less Than 12 Months, Unrealized Losses	(83.8)	(24.3)
Continuous Unrealized Loss Position, 12 Months Or Longer, Fair Value	396.9	937.6
Continuous Unrealized Loss Position, 12 Months Or Longer, Unrealized Losses	(11.5)	(28.6)
Continuous Unrealized Loss Position, Total, Fair Value	4,644.1	4,092.7
Continuous Unrealized Loss Position, Total, Unrealized Losses	(95.3)	(52.9)
Held To Maturity Securities, Continuous Unrealized Loss Position, Total, Unrealized Losses	(26.7)
GSE Residential Mortgage-Backed Securities and CMOs [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Held To Maturity Securities, Continuous Unrealized Loss Position, Less Than 12 Months, Fair Value	497.6	585.7
Held To Maturity Securities, Continuous Unrealized Loss Position, Less Than 12 Months, Unrealized Losses	(3.2)	(2.8)
Held To Maturity Securities, Continuous Unrealized Loss Position, 12 Months Or Longer, Unrealized Losses	0	0
Held To Maturity Securities, Continuous Unrealized Loss Position, Total, Fair Value	497.6	585.7
Held To Maturity Securities, Continuous Unrealized Loss Position, Total, Unrealized Losses	(3.2)	(2.8)
Available for Sale Securities, Continuous Unrealized Loss Position, Less Than 12 Months, Fair Value	2,339.6	2,200.8
Available for Sale Securities, Continuous Unrealized Loss Position, Less Than 12 Months, Unrealized Losses	(26.6)	(20.3)
Available for Sale Securities, Continuous Unrealized Loss Position, 12 Months Or Longer, Fair Value	396.9	933.9
Available for Sale Securities, Continuous Unrealized Loss Position, 12 Months Or Longer, Unrealized Losses	(11.5)	(28.6)
Available for Sale Securities, Continuous Unrealized Loss Position, Total, Fair Value	2,736.5	3,134.7
Available for Sale Securities, Continuous Unrealized Loss Position, Total, Unrealized Losses	(38.1)	(48.9)
U.S. Treasury and Agency [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available for Sale Securities, Continuous Unrealized Loss Position, Less Than 12 Months, Fair Value		346.3
Available for Sale Securities, Continuous Unrealized Loss Position, Less Than 12 Months, Unrealized Losses		(1.1)
Available for Sale Securities, Continuous Unrealized Loss Position, Total, Fair Value		346.3
Available for Sale Securities, Continuous Unrealized Loss Position, Total, Unrealized Losses		(1.1)
State and Municipal [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Held To Maturity Securities, Continuous Unrealized Loss Position, Less Than 12 Months, Fair Value	581.7	22.3
Held To Maturity Securities, Continuous Unrealized Loss Position, Less Than 12 Months, Unrealized Losses	(23.5)	(0.1)
Held To Maturity Securities, Continuous Unrealized Loss Position, 12 Months Or Longer, Fair Value		3.7
Held To Maturity Securities, Continuous Unrealized Loss Position, 12 Months Or Longer, Unrealized Losses	0	0
Held To Maturity Securities, Continuous Unrealized Loss Position, Total, Fair Value	581.7	26
Held To Maturity Securities, Continuous Unrealized Loss Position, Total, Unrealized Losses	(23.5)	$ (0.1)
Available for Sale Securities, Continuous Unrealized Loss Position, Less Than 12 Months, Fair Value	828.3
Available for Sale Securities, Continuous Unrealized Loss Position, Less Than 12 Months, Unrealized Losses	(30.5)
Available for Sale Securities, Continuous Unrealized Loss Position, Total, Fair Value	828.3
Available for Sale Securities, Continuous Unrealized Loss Position, Total, Unrealized Losses	$ (30.5)

Securities - Schedule of Gains

Securities - Schedule of Gains and Losses from Sales of Debt Securities (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Gain (Loss) on Sale of Securities, Net [Abstract]
Gains	$ 0.2	$ 0.3	$ 4.4
Losses	(6.1)	$ (0.3)	(1.4)
Net security (losses) gains	$ (5.9)		$ 3

Loans - Additional Information

Loans - Additional Information (Detail)	Apr. 16, 2010USD ($)	Dec. 31, 2016USD ($)SegmentsRating	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)	Dec. 31, 2011USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of segments | Segments		2
Net deferred loan costs		$ 69,900,000	$ 59,800,000
Construction loans		604,100,000	630,600,000
Interest-only residential mortgage loans		1,200,000,000	1,100,000,000
Net gains on sales of residential mortgage loans		6,300,000	5,500,000	$ 2,900,000
Loans held for sale		39,300,000	34,500,000
Acquired loans sold, outstanding balance		0	24,100,000	10,400,000
Acquired loans sold, carrying amount			22,300,000	10,300,000
Net gains (losses) on sales of acquired loan			1,700,000	(900,000)
Recorded investments, non-performing loans		148,000,000	159,400,000	197,000,000
Interest income that would have recognized		14,400,000	14,100,000	16,100,000
Interest Income Recognized		984,400,000	945,600,000	932,600,000
Allowance for loan losses		229,300,000	211,000,000	198,300,000	$ 187,800,000
Interest Income Recognized		$ 5,700,000	6,100,000	4,800,000
Temporary reduction of interest rate for TDRs, basis points		2.00%
Collateral values/LTV ratios, minimum		70.00%
Borrower credit scores, minimum | Rating		680
Principal and interest payments receivable						$ 7,570,000,000
Expected cash flows						7,020,000,000
Loan portfolio fair value						5,360,000,000
Aggregate loan nonaccretable difference						550,900,000
Portfolio accretable yield		$ 255,400,000	296,000,000	396,300,000	639,700,000
Portfolio outstanding balance		707,000,000	901,900,000
Portfolio carrying value		610,200,000	796,600,000
FDIC loss-share receivable		1,800,000	3,500,000
Commercial Real Estate Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Early non-performing loans		10,500,000	16,000,000
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Early non-performing loans		24,800,000	15,000,000
Equipment Financing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Early non-performing loans		28,400,000	20,500,000
Commercial Real Estate Construction Financing Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Construction loan not yet advanced		243,100,000	314,100,000
Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investments, non-performing loans		103,200,000	102,600,000	141,400,000
Allowance for loan losses		204,900,000	189,700,000	179,400,000	168,300,000
Interest Income Recognized		3,800,000	4,300,000	3,100,000
Commercial [Member] | Commercial Real Estate Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investments, non-performing loans		22,300,000	30,200,000	60,200,000
Interest Income Recognized		1,400,000	1,600,000	1,300,000
Commercial [Member] | Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investments, non-performing loans		41,500,000	44,900,000	55,800,000
Interest Income Recognized		2,100,000	1,800,000	1,100,000
Commercial [Member] | Equipment Financing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investments, non-performing loans		39,400,000	27,500,000	25,400,000
Interest Income Recognized		300,000	900,000	700,000
Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investments, non-performing loans		44,800,000	56,800,000	55,600,000
Allowance for loan losses		24,400,000	21,300,000	18,900,000	19,500,000
Interest Income Recognized		$ 1,900,000	$ 1,800,000	1,700,000
Duration of extension for payment deferral on TDRs, years		9 years
Connecticut [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of total loan portfolio representing loans to customers		26.00%
New York State [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of total loan portfolio representing loans to customers		19.00%
Massachusetts [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		59.00%	59.00%
Outside New England [Member] | Equipment Financing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of total loan portfolio representing loans to customers		96.00%	97.00%
Texas California and New York [Member] | Equipment Financing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of total loan portfolio representing loans to customers		29.00%
Outside Texas California and New York [Member] | Equipment Financing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of total loan portfolio representing loans to customers		5.00%
Maximum [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Duration of extension for payment deferral on TDRs, years		2 years
Residential Mortgage Construction Financing Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Construction loans		$ 84,200,000	$ 105,700,000
Construction loan not yet advanced		21,400,000	38,600,000
At Acquisition [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Portfolio accretable yield						$ 1,660,000,000
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%
Acquired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net gains (losses) on sales of acquired loan			1,700,000	(900,000)
Allowance for loan losses		6,300,000	8,100,000
Acquired Loans [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses		6,100,000	7,900,000	9,800,000	9,800,000
Acquired Loans [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses		200,000	200,000	400,000	$ 500,000
Non-Performing Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest Income Recognized		1,800,000	1,600,000	3,200,000
Purchased Credit Impaired Loans [Member] | Acquired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investments, non-performing loans		21,600,000	27,700,000	100,600,000
Covered by FDIC Loss-Share [Member] | Acquired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investments, non-performing loans		3,100,000	2,300,000	3,000,000
Troubled Debt Restructurings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment in originated loans classified as TDRs		189,900,000	195,700,000
Allowance for loan losses		4,200,000	5,900,000
Interest Income Recognized		4,800,000	4,600,000	$ 3,800,000
Foreclosure or Bankruptcy [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Early non-performing loans		$ 17,600,000	$ 21,800,000

Loans - Summary of Loans by Loa

Loans - Summary of Loans by Loan Portfolio Segment and Class (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 29,744.9	$ 28,410.9
Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	21,404.9	20,750.8
Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	8,340	7,660.1
Commercial Real Estate Loan [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	10,247.3	10,028.8
Commercial and Industrial [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	8,125.1	7,748.7
Equipment Financing [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	3,032.5	2,973.3
Residential Mortgage Adjustable Rate [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	5,549.1	4,851.2
Residential Mortgage Fixed Rate [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	667.6	605.8
Residential Mortgage Loan [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	6,216.7	5,457
Home Equity Loan [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,072.6	2,153.7
Other Consumer [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	50.7	49.4
Home Equity and Other Consumer [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,123.3	2,203.1
Originated [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	29,134.7	27,614.3
Originated [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	20,972.5	20,180.9
Originated [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	8,162.2	7,433.4
Originated [Member] | Commercial Real Estate Loan [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	10,012.6	9,696.9
Originated [Member] | Commercial and Industrial [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	7,939	7,526.4
Originated [Member] | Equipment Financing [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	3,020.9	2,957.6
Originated [Member] | Residential Mortgage Adjustable Rate [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	5,453.8	4,733.3
Originated [Member] | Residential Mortgage Fixed Rate [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	613.5	536.1
Originated [Member] | Residential Mortgage Loan [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	6,067.3	5,269.4
Originated [Member] | Home Equity Loan [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,044.9	2,115.5
Originated [Member] | Other Consumer [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	50	48.5
Originated [Member] | Home Equity and Other Consumer [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,094.9	2,164
Acquired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	610.2	796.6
Acquired Loans [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	432.4	569.9
Acquired Loans [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	177.8	226.7
Acquired Loans [Member] | Commercial Real Estate Loan [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	234.7	331.9
Acquired Loans [Member] | Commercial and Industrial [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	186.1	222.3
Acquired Loans [Member] | Equipment Financing [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	11.6	15.7
Acquired Loans [Member] | Residential Mortgage Adjustable Rate [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	95.3	117.9
Acquired Loans [Member] | Residential Mortgage Fixed Rate [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	54.1	69.7
Acquired Loans [Member] | Residential Mortgage Loan [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	149.4	187.6
Acquired Loans [Member] | Home Equity Loan [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	27.7	38.2
Acquired Loans [Member] | Other Consumer [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	0.7	0.9
Acquired Loans [Member] | Home Equity and Other Consumer [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 28.4	$ 39.1

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, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period				$ 211				$ 198.3	$ 211	$ 198.3	$ 187.8
Charge-offs									(23.4)	(28)	(36.1)
Recoveries									5.1	7.3	6
Net loan charge-offs									(18.3)	(20.7)	(30.1)
Provision for loan losses	$ 7.7	$ 8.4	$ 10	10.5	$ 9.7	$ 6.2	$ 7.7	9.8	36.6	33.4	40.6
Balance at end of period	229.3				211				229.3	211	198.3
Acquired Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period				8.1					8.1
Balance at end of period	6.3				8.1				6.3	8.1
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period				189.7				179.4	189.7	179.4	168.3
Charge-offs									(14.9)	(20.1)	(24.9)
Recoveries									2.1	4.9	3.6
Net loan charge-offs									(12.8)	(15.2)	(21.3)
Provision for loan losses									28	25.5	32.4
Balance at end of period	204.9				189.7				204.9	189.7	179.4
Commercial [Member] | Originated [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period				181.8				169.6	181.8	169.6	158.5
Charge-offs									(13.5)	(20.1)	(22.3)
Recoveries									2.1	4.9	3.6
Net loan charge-offs									(11.4)	(15.2)	(18.7)
Provision for loan losses									28.4	27.4	29.8
Balance at end of period	198.8				181.8				198.8	181.8	169.6
Commercial [Member] | Acquired Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period				7.9				9.8	7.9	9.8	9.8
Charge-offs									(1.4)		(2.6)
Net loan charge-offs									(1.4)		(2.6)
Provision for loan losses									(0.4)	(1.9)	2.6
Balance at end of period	6.1				7.9				6.1	7.9	9.8
Retail Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period				21.3				18.9	21.3	18.9	19.5
Charge-offs									(8.5)	(7.9)	(11.2)
Recoveries									3	2.4	2.4
Net loan charge-offs									(5.5)	(5.5)	(8.8)
Provision for loan losses									8.6	7.9	8.2
Balance at end of period	24.4				21.3				24.4	21.3	18.9
Retail Loans [Member] | Originated [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period				21.1				18.5	21.1	18.5	19
Charge-offs									(8.5)	(7.9)	(11.1)
Recoveries									3	2.4	2.4
Net loan charge-offs									(5.5)	(5.5)	(8.7)
Provision for loan losses									8.6	8.1	8.2
Balance at end of period	24.2				21.1				24.2	21.1	18.5
Retail Loans [Member] | Acquired Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period				$ 0.2				$ 0.4	0.2	0.4	0.5
Charge-offs											(0.1)
Net loan charge-offs											(0.1)
Provision for loan losses										(0.2)
Balance at end of period	$ 0.2				$ 0.2				$ 0.2	$ 0.2	$ 0.4

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, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable, Allowance for Credit Losses [Line Items]
Originated Loans Individually Evaluated for Impairment, Portfolio	$ 253.6	$ 252.1
Originated Loans Individually Evaluated for Impairment, Allowance	9	9.4
Originated Loans Collectively Evaluated for Impairment, Portfolio	28,881.1	27,362.2
Originated Loans Collectively Evaluated for Impairment, Allowance	214	193.5
Loans, Portfolio	29,744.9	28,410.9
Total Allowance	229.3	211	$ 198.3	$ 187.8
Receivables Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans, Portfolio	610.2	796.6
Total Allowance	6.3	8.1
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Originated Loans Individually Evaluated for Impairment, Portfolio	161.8	155.1
Originated Loans Individually Evaluated for Impairment, Allowance	5.8	5.5
Originated Loans Collectively Evaluated for Impairment, Portfolio	20,810.7	20,025.8
Originated Loans Collectively Evaluated for Impairment, Allowance	193	176.3
Loans, Portfolio	21,404.9	20,750.8
Total Allowance	204.9	189.7	179.4	168.3
Commercial [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans, Portfolio	432.4	569.9
Total Allowance	6.1	7.9
Retail Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Originated Loans Individually Evaluated for Impairment, Portfolio	91.8	97
Originated Loans Individually Evaluated for Impairment, Allowance	3.2	3.9
Originated Loans Collectively Evaluated for Impairment, Portfolio	8,070.4	7,336.4
Originated Loans Collectively Evaluated for Impairment, Allowance	21	17.2
Loans, Portfolio	8,340	7,660.1
Total Allowance	24.4	21.3	$ 18.9	$ 19.5
Retail Loans [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans, Portfolio	177.8	226.7
Total Allowance	$ 0.2	$ 0.2

Loans - Summarized Recorded Inv

Loans - Summarized Recorded Investments, by Class of Loan, of Originated Non-Performing Loans (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investments, non-performing loans	$ 148	$ 159.4	$ 197
Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investments, non-performing loans	103.2	102.6	141.4
Retail Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investments, non-performing loans	44.8	56.8	55.6
Commercial Real Estate Loan [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investments, non-performing loans	22.3	30.2	60.2
Commercial and Industrial [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investments, non-performing loans	41.5	44.9	55.8
Equipment Financing [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investments, non-performing loans	39.4	27.5	25.4
Residential Mortgage Loan [Member] | Retail Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investments, non-performing loans	27.4	37.2	37.6
Home Equity Loan [Member] | Retail Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investments, non-performing loans	$ 17.4	19.5	17.9
Other Consumer [Member] | Retail Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investments, non-performing loans		$ 0.1	$ 0.1

Loans - Summarized Recorded I71

Loans - Summarized Recorded Investments, by Class of Loan, of Originated Non-Performing Loans (Parenthetical) (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
Government guarantees	$ 13.1	$ 16.9	$ 17.6
Recorded investments, non-performing loans	148	159.4	197
Foreclosure [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investments, non-performing loans	$ 9.8	$ 19.9	$ 18.9
Commercial Real Estate Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Guarantee rate	1.00%
Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Guarantee rate	99.00%

Loans - Summary of Recorded Inv

Loans - Summary of Recorded Investments in TDRs by Class of Loan (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2016USD ($)Contracts	Dec. 31, 2015USD ($)Contracts
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	249	299
Pre-Modification Outstanding Recorded Investment	$ 123.8	$ 153.9
Post-Modification Outstanding Recorded Investment	$ 123.8	$ 153.9
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	130	135
Pre-Modification Outstanding Recorded Investment	$ 103.8	$ 124.3
Post-Modification Outstanding Recorded Investment	$ 103.8	$ 124.3
Retail Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	119	164
Pre-Modification Outstanding Recorded Investment	$ 20	$ 29.6
Post-Modification Outstanding Recorded Investment	$ 20	$ 29.6
Commercial Real Estate Loan [Member] | Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	18	26
Pre-Modification Outstanding Recorded Investment	$ 28.2	$ 15.2
Post-Modification Outstanding Recorded Investment	$ 28.2	$ 15.2
Commercial and Industrial [Member] | Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	51	61
Pre-Modification Outstanding Recorded Investment	$ 44.9	$ 80.6
Post-Modification Outstanding Recorded Investment	$ 44.9	$ 80.6
Equipment Financing [Member] | Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	61	48
Pre-Modification Outstanding Recorded Investment	$ 30.7	$ 28.5
Post-Modification Outstanding Recorded Investment	$ 30.7	$ 28.5
Residential Mortgage Loan [Member] | Retail Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	57	66
Pre-Modification Outstanding Recorded Investment	$ 15.5	$ 20.1
Post-Modification Outstanding Recorded Investment	$ 15.5	$ 20.1
Home Equity Loan [Member] | Retail Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	62	98
Pre-Modification Outstanding Recorded Investment	$ 4.5	$ 9.5
Post-Modification Outstanding Recorded Investment	$ 4.5	$ 9.5

Loans - Summary of Recorded I73

Loans - Summary of Recorded Investments in TDRs by Class of Loan (Parenthetical) (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2016USD ($)Contracts	Dec. 31, 2015USD ($)Contracts
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	249	299
Recorded investment | $	$ 123.8	$ 153.9
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	130	135
Recorded investment | $	$ 103.8	$ 124.3
Commercial [Member] | Commercial Real Estate Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	18	26
Recorded investment | $	$ 28.2	$ 15.2
Commercial [Member] | Commercial and Industrial [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	51	61
Recorded investment | $	$ 44.9	$ 80.6
Commercial [Member] | Equipment Financing [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	61	48
Recorded investment | $	$ 30.7	$ 28.5
Commercial [Member] | Extended Maturity [Member] | Commercial Real Estate Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	13	21
Recorded investment | $	$ 8.1	$ 8.9
Commercial [Member] | Extended Maturity [Member] | Commercial and Industrial [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	32	35
Recorded investment | $	$ 23.4	$ 41.1
Commercial [Member] | Extended Maturity [Member] | Equipment Financing [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	17	1
Recorded investment | $	$ 6.2	$ 0.1
Commercial [Member] | Payment Deferral [Member] | Commercial Real Estate Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	3	2
Recorded investment | $	$ 3	$ 1.2
Commercial [Member] | Payment Deferral [Member] | Commercial and Industrial [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	10	20
Recorded investment | $	$ 9.9	$ 35.9
Commercial [Member] | Payment Deferral [Member] | Equipment Financing [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	30	38
Recorded investment | $	$ 17.6	$ 21.5
Commercial [Member] | Combination of Concessions [Member] | Commercial Real Estate Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	2	3
Recorded investment | $	$ 17.1	$ 5.1
Commercial [Member] | Combination of Concessions [Member] | Commercial and Industrial [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	9	6
Recorded investment | $	$ 11.6	$ 3.6
Commercial [Member] | Combination of Concessions [Member] | Equipment Financing [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	14	9
Recorded investment | $	$ 6.9	$ 6.9
Retail Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	119	164
Recorded investment | $	$ 20	$ 29.6
Retail Loans [Member] | Residential Mortgage Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	57	66
Recorded investment | $	$ 15.5	$ 20.1
Retail Loans [Member] | Home Equity Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	62	98
Recorded investment | $	$ 4.5	$ 9.5
Retail Loans [Member] | Payment Deferral [Member] | Residential Mortgage Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	13	13
Recorded investment | $	$ 5.8	$ 4.7
Retail Loans [Member] | Payment Deferral [Member] | Home Equity Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	4	7
Recorded investment | $	$ 0.4	$ 0.8
Retail Loans [Member] | Combination of Concessions [Member] | Residential Mortgage Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	23	27
Recorded investment | $	$ 6	$ 9.2
Retail Loans [Member] | Combination of Concessions [Member] | Home Equity Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	20	29
Recorded investment | $	$ 1.6	$ 3
Retail Loans [Member] | Bankruptcy [Member] | Residential Mortgage Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	21	24
Recorded investment | $	$ 3.7	$ 5.9
Retail Loans [Member] | Bankruptcy [Member] | Home Equity Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	38	61
Recorded investment | $	$ 2.5	$ 5.2
Retail Loans [Member] | Contractual Interest Rate Reduction [Member] | Residential Mortgage Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts		2
Recorded investment | $		$ 0.3
Retail Loans [Member] | Contractual Interest Rate Reduction [Member] | Home Equity Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts		1
Recorded investment | $		$ 0.5

Loans - Summary of Recorded I74

Loans - Summary of Recorded Investments in TDRs by Class of Loan, Subsequently Defaulted (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2016USD ($)Contracts	Dec. 31, 2015USD ($)Contracts
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	52	51
Recorded Investment | $	$ 15.9	$ 13.3
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	28	18
Recorded Investment | $	$ 12.5	$ 8.9
Commercial [Member] | Commercial Real Estate Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	3	5
Recorded Investment | $	$ 1.1	$ 3.2
Commercial [Member] | Commercial and Industrial [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	5	4
Recorded Investment | $	$ 8.6	$ 1.2
Commercial [Member] | Equipment Financing [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	20	9
Recorded Investment | $	$ 2.8	$ 4.5
Retail Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	24	33
Recorded Investment | $	$ 3.4	$ 4.4
Retail Loans [Member] | Residential Mortgage Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	12	17
Recorded Investment | $	$ 2.6	$ 2.6
Retail Loans [Member] | Home Equity Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	12	16
Recorded Investment | $	$ 0.8	$ 1.8

Loans - Summary of Individually

Loans - Summary of Individually-Evaluated Impaired Loans by Class of Loan (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Impaired [Line Items]
With no related allowance for loan losses, Unpaid Principal Balance	$ 216.3	$ 222.8
With no related allowance for loan losses, Recorded Investment	197.7	203
With a related allowance for loan losses, Unpaid Principal Balance	58.3	58.2
With a related allowance for loan losses, Recorded Investment	55.9	49.1
Unpaid Principal Balance	274.6	281
Recorded Investment	253.6	252.1
Related Allowance for Loan Losses	9	9.4
Commercial [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	173.4	174.1
Recorded Investment	161.8	155.1
Related Allowance for Loan Losses	5.8	5.5
Commercial [Member] | Commercial Real Estate Loan [Member]
Financing Receivable, Impaired [Line Items]
With no related allowance for loan losses, Unpaid Principal Balance	41.4	46.5
With no related allowance for loan losses, Recorded Investment	40	45.3
With a related allowance for loan losses, Unpaid Principal Balance	12.2	18.8
With a related allowance for loan losses, Recorded Investment	11.4	14.7
Unpaid Principal Balance	53.6	65.3
Recorded Investment	51.4	60
Related Allowance for Loan Losses	0.6	1.9
Commercial [Member] | Commercial and Industrial [Member]
Financing Receivable, Impaired [Line Items]
With no related allowance for loan losses, Unpaid Principal Balance	50.7	53.2
With no related allowance for loan losses, Recorded Investment	45.7	50.8
With a related allowance for loan losses, Unpaid Principal Balance	25.9	19.2
With a related allowance for loan losses, Recorded Investment	25	14.7
Unpaid Principal Balance	76.6	72.4
Recorded Investment	70.7	65.5
Related Allowance for Loan Losses	4.7	3.3
Commercial [Member] | Equipment Financing [Member]
Financing Receivable, Impaired [Line Items]
With no related allowance for loan losses, Unpaid Principal Balance	38.2	32.6
With no related allowance for loan losses, Recorded Investment	35.3	26
With a related allowance for loan losses, Unpaid Principal Balance	5	3.8
With a related allowance for loan losses, Recorded Investment	4.4	3.6
Unpaid Principal Balance	43.2	36.4
Recorded Investment	39.7	29.6
Related Allowance for Loan Losses	0.5	0.3
Retail Loans [Member]
Financing Receivable, Impaired [Line Items]
With a related allowance for loan losses, Recorded Investment	15.1
Unpaid Principal Balance	101.2	106.9
Recorded Investment	91.8	97
Related Allowance for Loan Losses	3.2	3.9
Retail Loans [Member] | Residential Mortgage Loan [Member]
Financing Receivable, Impaired [Line Items]
With no related allowance for loan losses, Unpaid Principal Balance	63.6	67.2
With no related allowance for loan losses, Recorded Investment	58	60.4
With a related allowance for loan losses, Unpaid Principal Balance	13.1	14.1
With a related allowance for loan losses, Recorded Investment	13.1	14
Unpaid Principal Balance	76.7	81.3
Recorded Investment	71.1	74.4
Related Allowance for Loan Losses	2.3	2.9
Retail Loans [Member] | Home Equity Loan [Member]
Financing Receivable, Impaired [Line Items]
With no related allowance for loan losses, Unpaid Principal Balance	22.4	23.3
With no related allowance for loan losses, Recorded Investment	18.7	20.5
With a related allowance for loan losses, Unpaid Principal Balance	2.1	2.3
With a related allowance for loan losses, Recorded Investment	2	2.1
Unpaid Principal Balance	24.5	25.6
Recorded Investment	20.7	22.6
Related Allowance for Loan Losses	$ 0.9	$ 1

Loans - Schedule of Impaired Fi

Loans - Schedule of Impaired Financing Receivable (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	$ 249.8	$ 261.6	$ 241.4
Interest Income Recognized	5.7	6.1	4.8
Commercial [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	156.4	165.2	151.6
Interest Income Recognized	3.8	4.3	3.1
Commercial [Member] | Commercial Real Estate Loan [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	56.7	65.6	76.6
Interest Income Recognized	1.4	1.6	1.3
Commercial [Member] | Commercial and Industrial [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	62.6	71.6	46.4
Interest Income Recognized	2.1	1.8	1.1
Commercial [Member] | Equipment Financing [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	37.1	28	28.6
Interest Income Recognized	0.3	0.9	0.7
Retail Loans [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	93.4	96.4	89.8
Interest Income Recognized	1.9	1.8	1.7
Retail Loans [Member] | Residential Mortgage Loan [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	71.8	75.2	71.8
Interest Income Recognized	1.6	1.5	1.5
Retail Loans [Member] | Home Equity Loan [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	21.6	21.2	18
Interest Income Recognized	$ 0.3	$ 0.3	$ 0.2

Loans - Summary of Aging Inform

Loans - Summary of Aging Information by Class of Loan (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	$ 29,744.9	$ 28,410.9
Originated [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	28,938.1	27,380.9
Total Past Due	196.6	233.4
Total loans	29,134.7	27,614.3
Originated [Member] | 30-89 Days [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	116.8	130.4
Originated [Member] | 90 Days or More [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	79.8	103
Retail Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	8,340	7,660.1
Retail Loans [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	50.7	49.4
Retail Loans [Member] | Home Equity Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	2,072.6	2,153.7
Retail Loans [Member] | Residential Mortgage Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	6,216.7	5,457
Retail Loans [Member] | Originated [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	8,107.5	7,360
Total Past Due	54.7	73.4
Total loans	8,162.2	7,433.4
Retail Loans [Member] | Originated [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	49.7	48.2
Total Past Due	0.3	0.3
Total loans	50	48.5
Retail Loans [Member] | Originated [Member] | Home Equity Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	2,030.3	2,098.9
Total Past Due	14.6	16.6
Total loans	2,044.9	2,115.5
Retail Loans [Member] | Originated [Member] | Residential Mortgage Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	6,027.5	5,212.9
Total Past Due	39.8	56.5
Total loans	6,067.3	5,269.4
Retail Loans [Member] | Originated [Member] | 30-89 Days [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	27.5	38.4
Retail Loans [Member] | Originated [Member] | 30-89 Days [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0.3	0.2
Retail Loans [Member] | Originated [Member] | 30-89 Days [Member] | Home Equity Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	5.2	7.1
Retail Loans [Member] | Originated [Member] | 30-89 Days [Member] | Residential Mortgage Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	22	31.1
Retail Loans [Member] | Originated [Member] | 90 Days or More [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	27.2	35
Retail Loans [Member] | Originated [Member] | 90 Days or More [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		0.1
Retail Loans [Member] | Originated [Member] | 90 Days or More [Member] | Home Equity Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	9.4	9.5
Retail Loans [Member] | Originated [Member] | 90 Days or More [Member] | Residential Mortgage Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	17.8	25.4
Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	21,404.9	20,750.8
Commercial [Member] | Commercial Real Estate Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	10,247.3	10,028.8
Commercial [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	8,125.1	7,748.7
Commercial [Member] | Equipment Financing [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	3,032.5	2,973.3
Commercial [Member] | Originated [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	20,830.6	20,020.9
Total Past Due	141.9	160
Total loans	20,972.5	20,180.9
Commercial [Member] | Originated [Member] | Commercial Real Estate Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	9,989.9	9,667.7
Total Past Due	22.7	29.2
Total loans	10,012.6	9,696.9
Commercial [Member] | Originated [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	7,899.2	7,466.5
Total Past Due	39.8	59.9
Total loans	7,939	7,526.4
Commercial [Member] | Originated [Member] | Equipment Financing [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	2,941.5	2,886.7
Total Past Due	79.4	70.9
Total loans	3,020.9	2,957.6
Commercial [Member] | Originated [Member] | 30-89 Days [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	89.3	92
Commercial [Member] | Originated [Member] | 30-89 Days [Member] | Commercial Real Estate Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	10.9	15
Commercial [Member] | Originated [Member] | 30-89 Days [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	10	13.1
Commercial [Member] | Originated [Member] | 30-89 Days [Member] | Equipment Financing [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	68.4	63.9
Commercial [Member] | Originated [Member] | 90 Days or More [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	52.6	68
Commercial [Member] | Originated [Member] | 90 Days or More [Member] | Commercial Real Estate Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	11.8	14.2
Commercial [Member] | Originated [Member] | 90 Days or More [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	29.8	46.8
Commercial [Member] | Originated [Member] | 90 Days or More [Member] | Equipment Financing [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 11	$ 7

Loans - Summary of Credit Quali

Loans - Summary of Credit Quality Indicators by Class of Loan (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	$ 29,744.9	$ 28,410.9
Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	21,404.9	20,750.8
Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	8,340	7,660.1
Originated Loans [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	20,972.5	20,180.9
Originated Loans [Member] | Commercial [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	20,015.7	19,142
Originated Loans [Member] | Commercial [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	328	370.7
Originated Loans [Member] | Commercial [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	624.6	666.7
Originated Loans [Member] | Commercial [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	4.2	1.5
Originated Loans [Member] | Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	8,162.2	7,433.4
Originated Loans [Member] | Retail Loans [Member] | Low Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	3,998.4	3,564.3
Originated Loans [Member] | Retail Loans [Member] | Moderate Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	3,210	2,867.7
Originated Loans [Member] | Retail Loans [Member] | High Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	953.8	1,001.4
Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	610.2	796.6
Acquired Loans [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	432.4	569.9
Acquired Loans [Member] | Commercial [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	339.4	442.9
Acquired Loans [Member] | Commercial [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	25.7	31.7
Acquired Loans [Member] | Commercial [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	66.6	93.5
Acquired Loans [Member] | Commercial [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	0.7	1.8
Acquired Loans [Member] | Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	177.8	226.7
Acquired Loans [Member] | Retail Loans [Member] | Low Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	75.7	97.7
Acquired Loans [Member] | Retail Loans [Member] | Moderate Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	27.5	36.2
Acquired Loans [Member] | Retail Loans [Member] | High Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	74.6	92.8
Commercial Real Estate Loan [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	10,247.3	10,028.8
Commercial Real Estate Loan [Member] | Originated Loans [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	10,012.6	9,696.9
Commercial Real Estate Loan [Member] | Originated Loans [Member] | Commercial [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	9,817.2	9,438.6
Commercial Real Estate Loan [Member] | Originated Loans [Member] | Commercial [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	107.3	130.6
Commercial Real Estate Loan [Member] | Originated Loans [Member] | Commercial [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	87.1	127.7
Commercial Real Estate Loan [Member] | Originated Loans [Member] | Commercial [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	1
Commercial Real Estate Loan [Member] | Acquired Loans [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	234.7	331.9
Commercial Real Estate Loan [Member] | Acquired Loans [Member] | Commercial [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	182.9	260.9
Commercial Real Estate Loan [Member] | Acquired Loans [Member] | Commercial [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	13.5	20.1
Commercial Real Estate Loan [Member] | Acquired Loans [Member] | Commercial [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	37.6	49.1
Commercial Real Estate Loan [Member] | Acquired Loans [Member] | Commercial [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	0.7	1.8
Commercial and Industrial [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	8,125.1	7,748.7
Commercial and Industrial [Member] | Originated Loans [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	7,939	7,526.4
Commercial and Industrial [Member] | Originated Loans [Member] | Commercial [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	7,580.6	7,153.4
Commercial and Industrial [Member] | Originated Loans [Member] | Commercial [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	121.9	121
Commercial and Industrial [Member] | Originated Loans [Member] | Commercial [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	233.3	250.5
Commercial and Industrial [Member] | Originated Loans [Member] | Commercial [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	3.2	1.5
Commercial and Industrial [Member] | Acquired Loans [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	186.1	222.3
Commercial and Industrial [Member] | Acquired Loans [Member] | Commercial [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	155.5	175.9
Commercial and Industrial [Member] | Acquired Loans [Member] | Commercial [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	3.6	6.6
Commercial and Industrial [Member] | Acquired Loans [Member] | Commercial [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	27	39.8
Equipment Financing [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	3,032.5	2,973.3
Equipment Financing [Member] | Originated Loans [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	3,020.9	2,957.6
Equipment Financing [Member] | Originated Loans [Member] | Commercial [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	2,617.9	2,550
Equipment Financing [Member] | Originated Loans [Member] | Commercial [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	98.8	119.1
Equipment Financing [Member] | Originated Loans [Member] | Commercial [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	304.2	288.5
Equipment Financing [Member] | Acquired Loans [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	11.6	15.7
Equipment Financing [Member] | Acquired Loans [Member] | Commercial [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	1	6.1
Equipment Financing [Member] | Acquired Loans [Member] | Commercial [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	8.6	5
Equipment Financing [Member] | Acquired Loans [Member] | Commercial [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	2	4.6
Residential Mortgage Loan [Member] | Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	6,216.7	5,457
Residential Mortgage Loan [Member] | Originated Loans [Member] | Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	6,067.3	5,269.4
Residential Mortgage Loan [Member] | Originated Loans [Member] | Retail Loans [Member] | Low Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	3,016.4	2,579.3
Residential Mortgage Loan [Member] | Originated Loans [Member] | Retail Loans [Member] | Moderate Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	2,538.9	2,208.6
Residential Mortgage Loan [Member] | Originated Loans [Member] | Retail Loans [Member] | High Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	512	481.5
Residential Mortgage Loan [Member] | Acquired Loans [Member] | Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	149.4	187.6
Residential Mortgage Loan [Member] | Acquired Loans [Member] | Retail Loans [Member] | Low Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	75.7	97.7
Residential Mortgage Loan [Member] | Acquired Loans [Member] | Retail Loans [Member] | Moderate Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	27.5	36.2
Residential Mortgage Loan [Member] | Acquired Loans [Member] | Retail Loans [Member] | High Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	46.2	53.7
Home Equity Loan [Member] | Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	2,072.6	2,153.7
Home Equity Loan [Member] | Originated Loans [Member] | Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	2,044.9	2,115.5
Home Equity Loan [Member] | Originated Loans [Member] | Retail Loans [Member] | Low Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	950.9	959.2
Home Equity Loan [Member] | Originated Loans [Member] | Retail Loans [Member] | Moderate Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	663.9	651.2
Home Equity Loan [Member] | Originated Loans [Member] | Retail Loans [Member] | High Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	430.1	505.1
Home Equity Loan [Member] | Acquired Loans [Member] | Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	27.7	38.2
Home Equity Loan [Member] | Acquired Loans [Member] | Retail Loans [Member] | High Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	27.7	38.2
Other Consumer [Member] | Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	50.7	49.4
Other Consumer [Member] | Originated Loans [Member] | Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	50	48.5
Other Consumer [Member] | Originated Loans [Member] | Retail Loans [Member] | Low Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	31.1	25.8
Other Consumer [Member] | Originated Loans [Member] | Retail Loans [Member] | Moderate Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	7.2	7.9
Other Consumer [Member] | Originated Loans [Member] | Retail Loans [Member] | High Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	11.7	14.8
Other Consumer [Member] | Acquired Loans [Member] | Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	0.7	0.9
Other Consumer [Member] | Acquired Loans [Member] | Retail Loans [Member] | High Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	$ 0.7	$ 0.9

Loans - Summarized Activity in

Loans - Summarized Activity in Accretable Yield for Acquired Loan Portfolio (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Receivables [Abstract]
Balance at beginning of period	$ 296	$ 396.3	$ 639.7
Accretion	(39)	(55.5)	(81)
Reclassification from nonaccretable difference for loans with improved cash flows		1.1	6.7
Other changes in expected cash flows	(1.6)	(45.9)	(169.1)
Balance at end of period	$ 255.4	$ 296	$ 396.3

Goodwill and Other Acquisitio80

Goodwill and Other Acquisition-Related Intangible Assets - Schedule of Changes in Carrying Amount of Goodwill (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Goodwill [Line Items]
Beginning balance	$ 1,958.7	$ 1,954.5
Ending balance	1,992.7	1,958.7
Kesten Brown [Member]
Goodwill [Line Items]
Acquisition		4.2
Gerstein Fisher & Associates, Inc [Member]
Goodwill [Line Items]
Acquisition	31.7
Eagle Insurance Group, LLC [Member]
Goodwill [Line Items]
Acquisition	2.3
Commercial Banking Loan [Member]
Goodwill [Line Items]
Beginning balance	1,222.8	1,222.8
Adjustments	(0.7)
Ending balance	1,222.1	1,222.8
Retail Banking [Member]
Goodwill [Line Items]
Beginning balance	681.9	681.9
Adjustments	(2.3)
Ending balance	679.6	681.9
Wealth Management [Member]
Goodwill [Line Items]
Beginning balance	54	49.8
Adjustments	3
Ending balance	91	54
Wealth Management [Member] | Kesten Brown [Member]
Goodwill [Line Items]
Acquisition		$ 4.2
Wealth Management [Member] | Gerstein Fisher & Associates, Inc [Member]
Goodwill [Line Items]
Acquisition	31.7
Wealth Management [Member] | Eagle Insurance Group, LLC [Member]
Goodwill [Line Items]
Acquisition	$ 2.3

Goodwill and Other Acquisitio81

Goodwill and Other Acquisition-Related Intangible Assets - Other Acquisition-Related Intangibles (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Amount	$ 373.1	$ 345.7
Accumulated Amortization	240.2	216.6
Carrying Amount	132.9	129.1
Carrying Amount	149.4	129.1
Mutual Fund Management Contracts [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Carrying Amount	16.5
Trade Name Intangible [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Amount	123	122.7
Accumulated Amortization	50.3	42.8
Carrying Amount	72.7	79.9
Core Deposit Intangibles [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Amount	143.8	143.8
Accumulated Amortization	132	120
Carrying Amount	11.8	23.8
Customer Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Amount	42.7	42.7
Accumulated Amortization	25.6	22.8
Carrying Amount	17.1	19.9
Client Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Amount	24.4
Accumulated Amortization	0.3
Carrying Amount	24.1
Favorable Lease Agreement [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Amount	0.7
Carrying Amount	0.7
Noncompete Agreements [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Amount	0.4
Carrying Amount	0.4
Insurance Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Amount	38.1	36.5
Accumulated Amortization	32	31
Carrying Amount	$ 6.1	$ 5.5

Goodwill and Other Acquisitio82

Goodwill and Other Acquisition-Related Intangible Assets - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization of other acquisition-related intangible assets	$ 23,600,000	$ 23,900,000	$ 24,800,000
Amortization expense attributable to other acquisition-related intangible assets, 2017	24,700,000
Amortization expense attributable to other acquisition-related intangible assets, 2018	13,200,000
Amortization expense attributable to other acquisition-related intangible assets, 2019	12,400,000
Amortization expense attributable to other acquisition-related intangible assets, 2020	12,000,000
Amortization expense attributable to other acquisition-related intangible assets, 2021	11,700,000
Impairment losses relating to goodwill or other acquisition-related intangible assets	$ 0	$ 0	$ 0
Weighted-average amortization period, Years	14 years

Premises and Equipment - Compon

Premises and Equipment - Components of Premises and Equipment (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Land	$ 38.1	$ 38.8
Buildings	265.1	267.6
Leasehold improvements	161.8	158.2
Furniture and equipment	236.2	225.3
Total	701.2	689.9
Less: Accumulated depreciation and amortization	456.7	432.1
Total premises and equipment, net	$ 244.5	$ 257.8

Premises and Equipment - Additi

Premises and Equipment - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Depreciation and amortization expense included in occupancy and equipment expense	$ 36.9	$ 39.3	$ 39.6

Other Assets and Other Liabil85

Other Assets and Other Liabilities - Components of Other Assets (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Schedule Of Other Assets [Line Items]
Affordable housing investments (note 12)	$ 195.2	$ 158.4
Leased equipment	176.9	194.4
Fair value of derivative financial instruments (notes 19 and 21)	174	158.2
Accrued interest receivable	101.8	90.6
Loans in process	63.9	13.1
Assets held in trust for supplemental retirement plans (note 17)	39.6	36.5
Receivables arising from securities brokerage and insurance businesses	32	33.7
Current income tax receivable (note 12)	29.9	26.3
Funded status of defined benefit pension plans (note 17)	29.5	26.6
Investment in joint venture	21.3	22
Economic development investments	20.3	19.8
Other prepaid expenses	15.9	15.3
Net deferred tax asset (note 12)	9.4	1.9
Repossessed assets	7.2	9.5
Other	38.2	36.6
Total other assets	967.2	855.5
Residential Mortgage Loan [Member]
Schedule Of Other Assets [Line Items]
REO	8.1	7.1
Commercial Real Estate Loan [Member]
Schedule Of Other Assets [Line Items]
REO	$ 4	$ 5.5

Other Assets and Other Liabil86

Other Assets and Other Liabilities - Components of Other Assets (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Dec. 31, 2015	Jun. 30, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2016
Schedule Of Other Assets [Line Items]
Fair value of payroll services			$ 9.2	$ 20.6
Contingent receivable on payroll services	$ 2.8		2.8		$ 0.3
Debt issuance costs	5.6		$ 5.6
Vantiv, Inc [Member]
Schedule Of Other Assets [Line Items]
Percentage of ownership in joint venture		49.00%
Fair value of payroll services		$ 20.6
Payroll Services Sale [Member]
Schedule Of Other Assets [Line Items]
Fair value of payroll services	$ 9.2

Other Assets and Other Liabil87

Other Assets and Other Liabilities - Components of Other Liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Other Liabilities Disclosure [Abstract]
Fair value of derivative financial instruments (notes 19 and 21)	$ 121.7	$ 109.5
Future contingent commitments for affordable housing investments (note 12)	92.5	74.9
Liabilities for supplemental retirement plans (note 17)	68.1	63.9
Accrued expenses payable	68	43.7
Accrued employee benefits	50.6	48.4
Payables arising from securities brokerage and insurance businesses	33	34.7
Accrued interest payable	14.2	13.3
Other postretirement plan (note 17)	13.6	14
Liability for unsettled purchases of securities	5	5
Other	53.5	49.9
Total other liabilities	$ 520.2	$ 457.3

Other Assets and Other Liabil88

Other Assets and Other Liabilities - Components of Other Liabilities (Parenthetical) (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Other Liabilities Disclosure [Abstract]
Business Combination, Contingent payable	$ 21.4	$ 2

Deposits - Schedule of Deposits

Deposits - Schedule of Deposits (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Deposits
Non-interest-bearing, Amount	$ 6,660.8	$ 6,178.6
Savings	4,397.7	4,199.9
Interest-bearing checking and money market	14,260.1	13,220.8
Within 3 months, Amount	1,054.9	991.5
After 3 but within 6 months, Amount	852.4	679.6
After 6 months but within 1 year, Amount	835.2	1,915.6
After 1 but within 2 years, Amount	1,256.3	636.1
After 2 but within 3 years, Amount	142.7	153.5
After 3 but within 4 years, Amount	335.1	101.9
After 4 but within 5 years, Amount	65.5	339.6
After 5 years, Amount	0.1	0.3
Total, Amount	4,542.2	4,818.1
Total deposits	$ 29,860.8	$ 28,417.4
Non-interest-bearing, Weighted Average Rate	0.00%	0.00%
Savings, Weighted Average Rate	0.14%	0.13%
Interest-bearing checking and money market, Weighted Average Rate	0.27%	0.23%
Within 3 months, Weighted Average Rate	0.70%	0.69%
After 3 but within 6 months, Weighted Average Rate	0.75%	0.86%
After 6 months but within 1 year, Weighted Average Rate	0.75%	1.10%
After 1 but within 2 years, Weighted Average Rate	1.09%	1.06%
After 2 but within 3 years, Weighted Average Rate	1.26%	0.98%
After 3 but within 4 years, Weighted Average Rate	1.81%	1.46%
After 4 but within 5 years, Weighted Average Rate	1.03%	1.81%
After 5 years, Weighted Average Rate	0.93%	2.44%
Total, Weighted Average Rate	0.93%	1.03%
Total deposits, Weighted Average Rate	0.29%	0.30%

Deposits - Additional Informati

Deposits - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Banking and Thrift [Abstract]
Time deposits issued in amounts of $100,000 or more	$ 2,000	$ 2,100
Non-interest-bearing deposit overdrafts	$ 1.7	$ 1.6

Deposits - Schedule of Interest

Deposits - Schedule of Interest Expense on Deposits (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Banking and Thrift [Abstract]
Savings	$ 9.6	$ 11.4	$ 10.9
Interest-bearing checking and money market	43.4	32.1	25.8
Time	47.9	52	44.2
Total	$ 100.9	$ 95.5	$ 80.9

Borrowings - Summary of Borrowi

Borrowings - Summary of Borrowings (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Debt Disclosure [Abstract]
Fixed-rate FHLB advances maturing, within 1 month, Amount	$ 2,250	$ 2,750
Fixed-rate FHLB advances maturing, After 1 month but within 1 year, Amount	550	450
Fixed-rate FHLB advances maturing, After 1 but within 2 years, Amount	256.1
Fixed-rate FHLB advances maturing, After 2 but within 3 years, Amount		258.6
Fixed-rate FHLB advances maturing, After 5 years, Amount	5	5.2
Total FHLB advances, Amount	3,061.1	3,463.8	$ 2,291.7
Federal funds purchased maturing, within 1 month, Amount	617	374
Total federal funds purchased, Amount	617	374	486
Customer repurchase agreements maturing, within 1 month, Amount	343.3	469.5
Total customer repurchase agreements, Amount	343.3	469.5	913
Other borrowings maturing, within 1 year, Amount	35.4
Total other borrowings, Amount	35.4		$ 1
Total borrowings	$ 4,056.8	$ 4,307.3
Fixed rate FHLB advances maturing, within 1 month, Weighted Average Rate	0.69%	0.44%
Fixed rate FHLB advances maturing, After 1 month but within 1 year, Weighted Average Rate	0.77%	0.57%
Fixed-rate FHLB advances maturing, After 1 but within 2 years, Weighted Average Rate	2.71%
Fixed-rate FHLB advances maturing, After 2 but within 3 years, Weighted Average Rate		2.71%
Fixed-rate FHLB advances maturing, After 5 years, Weighted Average Rate	1.34%	1.34%
Total FHLB advances, Weighted Average Rate	0.87%	0.63%
Federal funds purchased maturing, within 1 month, Weighted Average Rate	0.71%	0.32%
Total federal funds purchased, Weighted Average Rate	0.71%	0.32%
Retail repurchase agreements maturing, within 1 month, Weighted Average Rate	0.19%	0.19%
Total customer repurchase agreements, Weighted Average Rate	0.19%	0.19%
Other borrowings maturing, within 1 year, Weighted Average Rate	0.55%
Total other borrowings, Weighted Average Rate	0.55%
Total borrowings, Weighted Average Rate	0.79%	0.55%

Borrowings - Additional Informa

Borrowings - Additional Information (Detail) $ in Billions	Dec. 31, 2016USD ($)
Debt Disclosure [Abstract]
Repurchase agreements and advances borrowing limit	$ 11.6
Unsecured borrowing capacity	$ 1

Borrowings - Interest Expense o

Borrowings - Interest Expense on Borrowings (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Debt Disclosure [Abstract]
FHLB advances	$ 19.3	$ 9.8	$ 9.2
Federal funds purchased	2.9	0.8	0.8
Customer repurchase agreements	0.6	0.9	1
Other borrowings			0.1
Total	$ 22.8	$ 11.5	$ 11.1

Borrowings - Information Concer

Borrowings - Information Concerning Parent Company Borrowings (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Debt Disclosure [Line Items]
FHLB advances, Balance at year end	$ 3,061.1	$ 3,463.8	$ 2,291.7
FHLB advances, Average outstanding during the year	3,093.7	2,306.6	2,593.7
FHLB advances, Maximum outstanding at any month end	$ 3,562.5	$ 3,463.8	$ 3,419.5
FHLB advances, Average interest rate during the year	0.62%	0.42%	0.36%
Customer repurchase agreements, Balance at year end	$ 343.3	$ 469.5	$ 913
Customer repurchase agreements, Average outstanding during the year	568.1	411	471.8
Customer repurchase agreements, Maximum outstanding at any month end	$ 872	$ 582	$ 960
Customer repurchase agreements, Average interest rate during the year	0.50%	0.19%	0.17%
Federal funds purchased and Other borrowings, Balance at year end	$ 617	$ 374	$ 486
Federal funds purchased and Other borrowings, Average outstanding during the year	337.2	463.6	482
Federal funds purchased and Other borrowings, Maximum outstanding at any month end	$ 427.2	$ 504.5	$ 519.2
Federal funds purchased and Other borrowings, Average interest rate during the year	0.19%	0.19%	0.20%
Other borrowings, Balance at year end	$ 35.4		$ 1
Other borrowings, Carrying amount of collateral securities at year end			1.1
Other borrowings, Average outstanding during the year	2.8	$ 0.6	57.1
Other borrowings, Maximum outstanding at any month end	$ 35.4	$ 1	$ 206.2
Other borrowings, Average interest rate during the year	0.66%	1.76%	0.25%
Securities Sold under Agreements to Repurchase [Member]
Debt Disclosure [Line Items]
Other borrowings, Carrying amount of collateral securities at year end	$ 350.2	$ 478.9	$ 495.7

Notes and Debentures - Schedule

Notes and Debentures - Schedule of Subordinated Borrowing (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Subordinated Borrowing [Line Items]
Notes and debentures	$ 125
Total notes and debentures	1,030.1	$ 1,033.1
People's United Financial, Inc. [Member]
Subordinated Borrowing [Line Items]
Total notes and debentures	621.5	619.7
People's United Financial, Inc. [Member] | 3.65% Senior Notes Due 2022 [Member]
Subordinated Borrowing [Line Items]
Notes and debentures	496.5	496
People's United Financial, Inc. [Member] | 5.80% Fixed Rate/Floating Rate Subordinated Notes Due 2017 [Member]
Subordinated Borrowing [Line Items]
Notes and debentures	125	123.7
People's United Bank [Member] | 4.00% Subordinated Notes Due 2024 [Member]
Subordinated Borrowing [Line Items]
Notes and debentures	$ 408.6	$ 413.4

Notes and Debentures - Addition

Notes and Debentures - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Subordinated Borrowing [Line Items]
Interest rate on debt	5.80%
Debt instrument, maturity date	Apr. 16, 2024
Redemption date description	The Bank may redeem the notes in whole, but not in part, at its option at a redemption price equal to 100% of the principal amount of the notes together with accrued but unpaid interest to, but excluding, the date fixed for redemption, within 90 days of the occurrence of a "regulatory event" (as defined). Pursuant to capital regulations of the OCC, effective January 1, 2015, the Bank may not redeem the notes prior to maturity without the prior approval of the OCC.
Debt issuance costs		$ 5.6
4.00% Subordinated Notes Due 2024 [Member]
Subordinated Borrowing [Line Items]
Interest rate on debt	4.00%
People's United Financial, Inc. [Member]
Subordinated Borrowing [Line Items]
Subordinated borrowing conversion rate	0.685%
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%
Subordinated notes due year	2,022
Frequency of payment of debt	Semi-annually
People's United Financial, Inc. [Member] | 5.80% Fixed Rate/Floating Rate Subordinated Notes Due 2017 [Member]
Subordinated Borrowing [Line Items]
Percentage of redemption price to principal amount	100.00%
Subordinated notes due year	2,017
Frequency of payment of debt	Semi-annually
Interest rate on debt	5.80%
Debt issue date	2,007
Subordinated borrowing interest rate	1.59%
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%
Frequency of payment of debt	Semi-annually
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, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Income tax expense applicable to pre-tax income	$ 30.2	$ 32.6	$ 34	$ 31.7	$ 34.6	$ 33.1	$ 32.2	$ 30.5	$ 128.5	$ 130.4	$ 128.9
Deferred income tax benefit applicable to items reported in total other comprehensive loss (note 16)									(10.6)	(5.3)	(6.7)
Total									$ 117.9	$ 125.1	$ 122.2

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, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Federal									$ 109.7	$ 103.6	$ 111.9
State									15.1	12.7	10.3
Total current tax expense									124.8	116.3	122.2
Deferred tax expense									3.7	14.1	6.7
Total income tax expense	$ 30.2	$ 32.6	$ 34	$ 31.7	$ 34.6	$ 33.1	$ 32.2	$ 30.5	$ 128.5	$ 130.4	$ 128.9

Income Taxes - Income Tax Ef100

Income Taxes - Income Tax Effects Related to Items Recognized in Other Comprehensive Income (Parenthetical) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Decrease in valuation allowance for state deferred tax assets	$ (1.3)	$ (0.1)	$ (1.2)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule Of Income Tax Expense [Line Items]
U.S. federal statutory rate	35.00%
Affordable housing investments	$ 195.2	$ 158.4
Future contingent commitments	$ 92.5	74.9
Amortization period	10 years
Income tax expense	$ 12.6	12.6	$ 10.7
Connecticut tax net operating loss carryforwards	1,400
Current income tax receivable	29.9	26.3
Accrued interest expense related to the unrecognized income tax benefits	$ 0.7	$ 0.6
Minimum [Member]
Schedule Of Income Tax Expense [Line Items]
Tax net operating loss carryforwards	2,020
Maximum [Member]
Schedule Of Income Tax Expense [Line Items]
Tax net operating loss carryforwards	2,036

Income Taxes - Summary of Incom

Income Taxes - Summary of Income Tax Reconciliation (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Expected income tax expense									$ 143.3	$ 136.7	$ 133.2
State income tax, net of federal tax effect									10	9.3	8.2
Tax-exempt interest									(20)	(16.4)	(13.2)
Federal income tax credits									(5.3)	(0.4)	0.8
Tax-exempt income from BOLI									(2)	(1.6)	(2)
Other, net									2.5	2.8	1.9
Total income tax expense	$ 30.2	$ 32.6	$ 34	$ 31.7	$ 34.6	$ 33.1	$ 32.2	$ 30.5	$ 128.5	$ 130.4	$ 128.9
Effective income tax rate									31.40%	33.40%	33.90%

Income Taxes - Deferred Tax Ass

Income Taxes - Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Leasing activities	$ 122.2	$ 101.5
Allowance for loan losses and non-accrual interest	90.2	82.7
State tax net operating loss carryforwards, net of federal tax effect	66.3	68
Equity-based compensation	19	22.9
Unrealized loss on securities available for sale	18.7	10.8
Pension and other postretirement benefits	10.9	12.2
Unrealized loss on securities transferred to held to maturity	10.2	12
Other deductible temporary differences	37.1	35.1
Total deferred tax assets	374.6	345.2
Less: valuation allowance for state deferred tax assets	(66.7)	(68)
Total deferred tax assets, net of the valuation allowance	307.9	277.2
Tax over book depreciation	(207.1)	(185.4)
Acquisition-related deferred tax liabilities	(35.3)	(39.9)
Book over tax income recognized on consumer loans	(18.4)	(14.6)
Mark-to-market and original issue discounts for tax purposes	(16)	(7.3)
Deferred cancellation-of-indebtedness income	(9)	(13.4)
Temporary differences related to merchant services joint venture	(6.3)	(6.8)
Other taxable temporary differences	(6.4)	(7.9)
Total deferred tax liabilities	(298.5)	(275.3)
Net deferred tax asset	$ 9.4	$ 1.9

Income Taxes - Unrecognized Inc

Income Taxes - Unrecognized Income Tax Benefits (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Banking and Thrift, Interest [Abstract]
Balance at beginning of year	$ 2.7	$ 3	$ 3
Additions for tax positions taken in prior years	0.1	0.1	0.1
Reductions for tax positions taken in prior years	0	0	0
Reductions attributable to audit settlements/lapse of statue of limitations		(0.4)	(0.1)
Balance at end of year	$ 2.8	$ 2.7	$ 3

Stockholders' Equity and Div105

Stockholders' Equity and Dividends - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	Oct. 31, 2016	Apr. 30, 2007	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule Of Stockholders Equity [Line Items]
Preferred stock, shares authorized			50,000,000								50,000,000
Preferred stock par value, per share			$ 0.01								$ 0.01
Common stock, shares authorized			1,950,000,000				1,950,000,000				1,950,000,000	1,950,000,000
Common stock, par value			$ 0.01				$ 0.01				$ 0.01	$ 0.01
Common stock, shares issued			405,000,000				399,200,000				405,000,000	399,200,000
Preferred stock, shares outstanding			10,000,000								10,000,000
Preferred stock, shares issued			10,000,000								10,000,000
Number of common stock purchased			89,100,000				89,100,000				89,100,000	89,100,000
Original loan amount ESOP		$ 216.8
ESOP shares purchased in open market		10,500,000
Employee stock ownership plan (ESOP), number of shares			6,969,050				7,300,000				6,969,050	7,300,000
Unallocated common stock of employee stock ownership plan, Value			$ 144.6				$ 151.8				$ 144.6	$ 151.8
Dividends paid per common share											$ 0.6775	$ 0.6675	$ 0.6575
Dividend payout ratio			69.80%	70.10%	75.40%	80.60%	71.50%	73.90%	81.80%	83.70%	73.70%	77.30%	78.20%
Cash dividends payable to parent company											$ 271	$ 245	$ 244
Repurchases Authorized by Board of Directors [Member]
Schedule Of Stockholders Equity [Line Items]
Number of common stock purchased			86,400,000								86,400,000
2007 Recognition and Retention Plan [Member]
Schedule Of Stockholders Equity [Line Items]
Number of common stock purchased			2,700,000								2,700,000
2014 Long-Term Incentive Plan [Member] | 2007 Recognition and Retention Plan [Member]
Schedule Of Stockholders Equity [Line Items]
Additional awards under RRP			0								0
Fixed - to - Floating Rate Non-cumulative Perpetual Preferred Stock, Series A [Member]
Schedule Of Stockholders Equity [Line Items]
Preferred stock par value, per share	$ 0.01
Preferred stock, shares issued	10,000,000
Preferred stock liquidation preference, per share	$ 25
Dividend payable rate	5.625%
Proceed from issuance of preferred stock, net of issuance cost											$ 5.9
Preferred stock, frequency of periodic payment											Payable quarterly in arrears on March 15, June 15, September 15 and December 15 of each year,
Preferred stock, date of first required payment											Dec. 15, 2016
Dividend payment fixed rate description											Up to and including December 14, 2026, the dividend will be based on a fixed-rate of 5.625% per annum.
Dividend payment floating rate description											From and including December 15, 2026, the dividend will be based on a floating-rate equal to three-month LIBOR plus a spread of 4.02% per annum.
Preferred stock dividend, description of variable rate basis											Three-month LIBOR
Dividend payable floating rate	4.02%
Preferred stock, redemption terms											The Company may redeem the preferred stock at its option, from time to time, on or after December 15, 2026, at a redemption price equal to $25.00 per share.
Redemption price	$ 25
People's United Financial, Inc. [Member]
Schedule Of Stockholders Equity [Line Items]
Preferred stock, shares authorized			50,000,000								50,000,000
Preferred stock par value, per share			$ 0.01								$ 0.01
Common stock, shares authorized			1,950,000,000								1,950,000,000
Common stock, par value			$ 0.01								$ 0.01
Common stock, shares issued			405,000,000								405,000,000
Preferred stock, shares outstanding			10								10
Cash dividends payable to parent company											$ 271	$ 245	$ 244
People's United Bank [Member]
Schedule Of Stockholders Equity [Line Items]
Retained net income under federal regulations											$ 42.8

Regulatory Capital Requireme106

Regulatory Capital Requirements - Additional Information (Detail) - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
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%
Common Tier 1 buffer phase start year	2,016
Risk-based capital tier 1, Ratio, Minimum capital adequacy	6.00%
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	0.625%
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	5.125%	4.50%
Risk-based capital tier 1, Ratio, Minimum capital adequacy	6.625%	6.00%
Total, Ratio, Minimum capital adequacy	12.50%	11.70%
Leverage (core) capital, Ratio	8.40%	8.00%
Risk-weighted assets	$ 30.5	$ 29.6
Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common equity tier 1 capital, Ratio, Minimum capital adequacy	5.125%	4.50%
Risk-based capital tier 1, Ratio, Minimum capital adequacy	6.625%	6.00%
Total, Ratio, Minimum capital adequacy	13.30%	12.60%
Leverage (core) capital, Ratio	8.90%	8.40%
Risk-weighted assets	$ 30.5	$ 29.6
Minimum [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Estimated basis point that negatively impacted on risk-based capital ratios	0.10%
Maximum [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Estimated basis point that negatively impacted on risk-based capital ratios	0.20%

Regulatory Capital Requireme107

Regulatory Capital Requirements - Regulatory Capital Requirements and Ratio under Basel III Capital Rules (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
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%
People's United Financial, Inc. [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 Leverage Capital, Amount	$ 3,256.1	$ 2,898.1
CET 1 Risk-Based Capital, Amount	3,012	2,898.1
Tier 1 Risk-Based Capital	3,256.1	2,898.1
Total, Amount	$ 3,802.9	$ 3,470.5
Tier 1 Leverage Capital, Ratio	8.40%	8.00%
CET 1 Risk-Based Capital, Ratio	9.90%	9.80%
Tier 1 Risk-Based Capital, Ratio	10.70%	9.80%
Total, Ratio	12.50%	11.70%
Tier 1 Leverage Capital, Minimum Capital Required, Amount	$ 1,546.7	$ 1,440.6
CET 1 Risk-Based Capital, Minimum Capital Required, Amount	1,565.2	1,620.7
Tier 1 Risk-Based Capital, Minimum Capital Required, Amount	2,023.3	1,778.8
Total, Minimum Capital Required, Amount	$ 2,634.1	$ 2,371.7
Tier 1 Leverage Capital, Ratio, Minimum Capital Required	4.00%	4.00%
CET 1 Risk-Based Capital, Ratio, Minimum Capital Required	5.125%	4.50%
Tier 1 Risk-Based Capital, Ratio, Minimum Capital Required	6.625%	6.00%
Total, Ratio, Minimum Capital Required	8.625%	8.00%
Tier 1 Leverage Capital, Well-Capitalized, Amount	$ 1,933.4	$ 1,800.8
CET 1 Risk-Based Capital, Well-Capitalized, Amount	1,985.1	2,341
Tier 1 Risk-Based Capital, Well-Capitalized, Amount	2,443.2	2,371.7
Total, Well-Capitalized, Amount	$ 3,054	$ 2,964.6
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%
Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 Leverage Capital, Amount	$ 3,430.5	$ 3,012.7
CET 1 Risk-Based Capital, Amount	3,430.5	3,012.7
Tier 1 Risk-Based Capital	3,430.5	3,012.7
Total, Amount	$ 4,062.1	$ 3,726.3
Tier 1 Leverage Capital, Ratio	8.90%	8.40%
CET 1 Risk-Based Capital, Ratio	11.30%	10.20%
Tier 1 Risk-Based Capital, Ratio	11.30%	10.20%
Total, Ratio	13.30%	12.60%
Tier 1 Leverage Capital, Minimum Capital Required, Amount	$ 1,537	$ 1,431.9
CET 1 Risk-Based Capital, Minimum Capital Required, Amount	1,562.5	1,610.9
Tier 1 Risk-Based Capital, Minimum Capital Required, Amount	2,019.9	1,777.3
Total, Minimum Capital Required, Amount	$ 2,629.7	$ 2,369.7
Tier 1 Leverage Capital, Ratio, Minimum Capital Required	4.00%	4.00%
CET 1 Risk-Based Capital, Ratio, Minimum Capital Required	5.125%	4.50%
Tier 1 Risk-Based Capital, Ratio, Minimum Capital Required	6.625%	6.00%
Total, Ratio, Minimum Capital Required	8.625%	8.00%
Tier 1 Leverage Capital, Well-Capitalized, Amount	$ 1,921.2	$ 1,789.8
CET 1 Risk-Based Capital, Well-Capitalized, Amount	1,981.8	2,326.8
Tier 1 Risk-Based Capital, Well-Capitalized, Amount	2,439.1	2,369.7
Total, Well-Capitalized, Amount	$ 3,048.9	$ 2,962.1
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%

Regulatory Capital Requireme108

Regulatory Capital Requirements - Regulatory Capital Requirements and Ratio under Basel III Capital Rules (Parenthetical) (Detail)	Dec. 31, 2016	Dec. 31, 2015
Banking and Thrift [Abstract]
Total Risk-Weighted Assets for allowance for loan losses	1.25%	1.25%

Earnings Per Common Share - Bas

Earnings Per Common Share - Basic and Diluted Earnings Per 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, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share [Abstract]
Net income available to common shareholders	$ 74.1	$ 73.7	$ 68.5	$ 62.9	$ 70.8	$ 68.4	$ 61.7	$ 59.2	$ 279.2	$ 260.1	$ 251.7
Dividends paid on and undistributed earnings allocated to participating securities									(0.9)	(1.1)	(1.2)
Earnings attributable to common shareholders									$ 278.3	$ 259	$ 250.5
Weighted average common shares outstanding for basic EPS	305,170	302,880	302,480	301,860	301,380	301,000	300,090	299,150	303,100	300,400	298,200
Effect of dilutive equity-based awards									900		100
Weighted average common and common-equivalent shares for diluted EPS	306,230	303,240	302,480	301,860	301,380	301,000	300,090	299,150	304,000	300,400	298,300
Basic EPS	$ 0.24	$ 0.24	$ 0.23	$ 0.21	$ 0.23	$ 0.23	$ 0.20	$ 0.20	$ 0.92	$ 0.86	$ 0.84
Diluted EPS	$ 0.24	$ 0.24	$ 0.23	$ 0.21	$ 0.23	$ 0.23	$ 0.20	$ 0.20	$ 0.92	$ 0.86	$ 0.84

Earnings Per Common Share - Add

Earnings Per Common Share - Additional Information (Detail) - shares shares in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share [Abstract]
Anti-dilutive equity-based awards excluded from calculation of diluted EPS	13.6	19.7	17.7

Comprehensive Income - Schedule

Comprehensive Income - Schedule of Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 4,731.6	$ 4,633.1	$ 4,568.4
Amounts reclassified from AOCL	10.2	7.9	5.5
Current period other comprehensive income (loss)	(17.8)	(9)	(13.1)
Ending Balance	5,141.9	4,731.6	4,633.1
Pension and Other Postretirement Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(140)	(142.9)	(85)
Other comprehensive income (loss) before reclassifications	(9.6)	(2.2)	(62.6)
Amounts reclassified from AOCL	4	5.1	4.7
Current period other comprehensive income (loss)	(5.6)	2.9	(57.9)
Ending Balance	(145.6)	(140)	(142.9)
Net Unrealized Gains (Losses) on Securities Available for Sale [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(17.7)	(3.7)	(46.5)
Other comprehensive income (loss) before reclassifications	(18.3)	(14)	44.6
Amounts reclassified from AOCL	3.7		(1.8)
Current period other comprehensive income (loss)	(14.6)	(14)	42.8
Ending Balance	(32.3)	(17.7)	(3.7)
Net Unrealized Gain (Losses) On Securities Transferred To Held To Maturity [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(19.5)	(21.5)	(23.3)
Amounts reclassified from AOCL	2.1	2	1.8
Current period other comprehensive income (loss)	2.1	2	1.8
Ending Balance	(17.4)	(19.5)	(21.5)
Net Unrealized Gains (Losses) on Derivatives Accounted for as Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		(0.1)	(0.3)
Other comprehensive income (loss) before reclassifications	(0.1)	(0.7)	(0.6)
Amounts reclassified from AOCL	0.4	0.8	0.8
Current period other comprehensive income (loss)	0.3	0.1	0.2
Ending Balance	0.3		(0.1)
Accumulated Other Comprehensive Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(177.2)	(168.2)	(155.1)
Other comprehensive income (loss) before reclassifications	(28)	(16.9)	(18.6)
Amounts reclassified from AOCL	10.2	7.9	5.5
Current period other comprehensive income (loss)	(17.8)	(9)	(13.1)
Ending Balance	$ (195)	$ (177.2)	$ (168.2)

Comprehensive Income - Summary

Comprehensive Income - Summary of Amounts Reclassified from AOCL (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income before income tax expense	$ (106.1)	$ (106.3)	$ (102.5)	$ (94.6)	$ (105.4)	$ (101.5)	$ (93.9)	$ (89.7)	$ (409.5)	$ (390.5)	$ (380.6)
Income tax expense	30.2	32.6	34	31.7	34.6	33.1	32.2	30.5	128.5	130.4	128.9
Net income	$ (75.9)	$ (73.7)	$ (68.5)	$ (62.9)	$ (70.8)	$ (68.4)	$ (61.7)	$ (59.2)	(281)	(260.1)	(251.7)
Total reclassifications for the period									(10.2)	(7.9)	(5.5)
Pension and Other Postretirement Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net actuarial loss									(7.2)	(9.1)	(8.4)
Prior service credit									0.8	1	1
Income before income tax expense									(6.4)	(8.1)	(7.4)
Income tax expense									2.4	3	2.7
Net income									(4)	(5.1)	(4.7)
Total reclassifications for the period									(4)	(5.1)	(4.7)
Net Unrealized Gains (Losses) on Securities Available for Sale [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income before income tax expense									(5.9)		3
Income tax expense									2.2		(1.2)
Net income									(3.7)		1.8
Total reclassifications for the period									(3.7)		1.8
Net Unrealized Gain (Losses) On Securities Transferred To Held To Maturity [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income before income tax expense									(3.3)	(3.1)	(3)
Income tax expense									1.2	1.1	1.2
Net income									(2.1)	(2)	(1.8)
Total reclassifications for the period									(2.1)	(2)	(1.8)
Net Unrealized Gains (Losses) on Derivatives Accounted for as Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income before income tax expense									(0.7)	(1.2)	(1.3)
Income tax expense									0.3	0.4	0.5
Net income									(0.4)	(0.8)	(0.8)
Total reclassifications for the period									(0.4)	(0.8)	(0.8)
Net Unrealized Gains (Losses) on Derivatives Accounted for as Cash Flow Hedges [Member] | Interest Rate Swaps [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest expense - notes and debentures									(0.8)	(1.3)	(1.4)
Net Unrealized Gains (Losses) on Derivatives Accounted for as Cash Flow Hedges [Member] | Interest Rate Locks [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest expense - notes and debentures									$ 0.1	$ 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, 2016	Dec. 31, 2015	Dec. 31, 2014
Equity [Abstract]
Net actuarial loss and other amounts related to pension and other postretirement plans	$ 85	$ 81.5	$ 83.2
Net unrealized loss on securities available for sale	18.8	10.3	2.2
Net unrealized loss on securities transferred to held to maturity	10.2	11.4	12.5
Net unrealized gain on derivatives accounted for as cash flow hedges	(0.2)
Total deferred income taxes	$ 113.8	$ 103.2	$ 97.9

Comprehensive Income - Other Co

Comprehensive Income - Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Equity [Abstract]
Net actuarial gain (loss) arising during the year, Pre-Tax	$ (15.5)	$ (3.5)	$ (98.5)
Reclassification adjustment for net actuarial loss included in net income, Pre-Tax	7.2	9.1	8.4
Net actuarial gain (loss), Pre-Tax	(8.3)	5.6	(90.1)
Reclassification adjustment for prior service credit included in net income, Pre-Tax	(0.8)	(1)	(1)
Net actuarial gain (loss) and prior service credit, Pre-Tax	(9.1)	4.6	(91.1)
Net unrealized holding gains (losses) arising during the year, Pre-Tax	(29)	(22.1)	70.9
Reclassification adjustment for net realized gains included in net income, Pre-Tax	5.9		(3)
Net unrealized gains (losses), Pre-Tax	(23.1)	(22.1)	67.9
Reclassification adjustment for amortization of unrealized losses on securities transferred to held to maturity included in net income, Pre-Tax	3.3	3.1	3
Net unrealized gains (losses), Pre-Tax	3.3	3.1	3
Net unrealized gains (losses) arising during the year, Pre-Tax	(0.2)	(1.1)	(0.9)
Reclassification adjustment for net realized loss included in net income, Pre-Tax	0.7	1.2	1.3
Net unrealized gains, Pre-Tax	0.5	0.1	0.4
Total other comprehensive loss, Pre-Tax	(28.4)	(14.3)	(19.8)
Net actuarial gain (loss) arising during the year, Tax Effect	5.9	1.3	35.9
Reclassification adjustment for net actuarial loss included in net income, Tax Effect	(2.7)	(3.4)	(3.1)
Net actuarial gain (loss), Tax Effect	3.2	(2.1)	32.8
Reclassification adjustment for prior service credit included in net income, Tax Effect	0.3	0.4	0.4
Net actuarial gain (loss) and prior service credit, Tax Effect	3.5	(1.7)	33.2
Net unrealized holding gains (losses) arising during the year, Tax Effect	10.7	8.1	(26.3)
Reclassification adjustment for net realized gains included in net income, Tax Effect	(2.2)		1.2
Net unrealized gains (losses), Tax Effect	8.5	8.1	(25.1)
Reclassification adjustment for amortization of unrealized losses on securities transferred to held to maturity included in net income, Tax Effect	(1.2)	(1.1)	(1.2)
Net unrealized gains (losses), Tax Effect	(1.2)	(1.1)	(1.2)
Net unrealized gains (losses) arising during the year, Tax Effect	0.1	0.4	0.3
Reclassification adjustment for net realized losses included in net income, Tax Effect	(0.3)	(0.4)	(0.5)
Net unrealized gains, Tax Effect	(0.2)		(0.2)
Total other comprehensive loss, Tax Effect	10.6	5.3	6.7
Net actuarial gain (loss) arising during the year, After Tax	(9.6)	(2.2)	(62.6)
Reclassification adjustment for net actuarial loss included in net income, After Tax	4.5	5.7	5.3
Net actuarial gain (loss), After Tax	(5.1)	3.5	(57.3)
Reclassification adjustment for prior service credit included in net income, After Tax	(0.5)	(0.6)	(0.6)
Net actuarial gain (loss) and prior service credit, After Tax	(5.6)	2.9	(57.9)
Net unrealized holding gains (losses) arising during the year, After Tax	(18.3)	(14)	44.6
Reclassification adjustment for net realized gains included in net income, After Tax	3.7		(1.8)
Net unrealized gains (losses), After Tax	(14.6)	(14)	42.8
Reclassification adjustment for amortization of unrealized losses on securities transferred to held to maturity included in net income, After Tax	2.1	2	1.8
Net unrealized gains (losses), After Tax	2.1	2	1.8
Net unrealized gains (losses) arising during the year, After Tax	(0.1)	(0.7)	(0.6)
Reclassification adjustment for net realized losses included in net income, After Tax	0.4	0.8	0.8
Net unrealized gains, After Tax	0.3	0.1	0.2
Total other comprehensive loss, After Tax	$ (17.8)	$ (9)	$ (13.1)

Employee Benefit Plans - People

Employee Benefit Plans - People's United Employee Pension and Other Postretirement Plans - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
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
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	$ 478,000,000	$ 466,500,000
Defined benefit plan, accumulated benefit obligations	68,100,000	63,900,000
Trust assets	$ 39,600,000	$ 36,500,000
Maximum percentage of any individual security	3.00%
Percentage of equity holdings invested in international equities	50.00%
Maximum percentage of fixed income holdings invested in issues rated below Baa	30.00%
Market value of total plan assets	2.50%
Qualified Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected long-term rate of return assumption	7.25%	7.50%	8.00%
Net periodic benefit income	$ 14,300,000
Expected long-term rate of return assumption	7.25%
Defined benefit plan, mortality rate impact to benefit obligations	$ 6,000,000
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, accumulated benefit obligations	489,300,000	$ 480,400,000
Defined benefit plan, projected benefit obligations	489,300,000	480,400,000	$ 515,300,000
Expected actuarial net gain (loss)	6,500,000
Prior service credit	800,000
Defined benefit plan, expected future benefit payments in year one	23,000,000
Defined benefit plan, expected future benefit payments in year two	20,800,000
Defined benefit plan, expected future benefit payments in year three	20,400,000
Defined benefit plan, expected future benefit payments in year four	20,300,000
Defined benefit plan, expected future benefit payments in year five	23,400,000
Defined benefit plan, expected future benefit payments after five years	125,100,000
Pension Plans [Member] | Qualified Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, accumulated benefit obligations	448,500,000	439,900,000
Defined benefit plan, projected benefit obligations	448,500,000	439,900,000
Pension Plans [Member] | Supplemental Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, accumulated benefit obligations	40,800,000	40,500,000
Defined benefit plan, projected benefit obligations	40,800,000	40,500,000
Trust assets	31,600,000
Other Pension Plan, Postretirement or Supplemental Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, expected future benefit payments in year one	300,000
Expected employer contributions	8,100,000
Other Postretirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, projected benefit obligations	13,600,000	$ 14,000,000	$ 14,600,000
Expected actuarial net gain (loss)	200,000
Defined benefit plan, expected future benefit payments in year one	2,500,000
Defined benefit plan, expected future benefit payments in year two	2,700,000
Defined benefit plan, expected future benefit payments in year three	2,200,000
Defined benefit plan, expected future benefit payments in year four	2,600,000
Defined benefit plan, expected future benefit payments in year five	2,700,000
Defined benefit plan, expected future benefit payments after five years	$ 15,500,000
Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated unrecognized gain or loss percentage for amortization of actuarial gain loss	10.00%
Minimum [Member] | Pension Plans [Member] | Supplemental Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate used to determine benefit obligation	3.60%	3.95%
Discount rate used to calculate net periodic benefit cost	3.95%	4.20%
Maximum [Member] | Pension Plans [Member] | Supplemental Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate used to determine benefit obligation	4.40%	4.60%
Discount rate used to calculate net periodic benefit cost	4.60%
People's Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of covered employee's eligible compensation	3.00%
Pension plan assets measured at fair value	$ 430,400,000
Amortization of unrecognized gain loss over average remaining life of plan participants	28 years
Expected employer contributions	$ 0
People's Qualified Plan [Member] | Qualified Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, accumulated benefit obligations	$ 405,500,000
Discount rate used to determine benefit obligation	4.41%	4.64%	4.20%
Discount rate used to calculate net periodic benefit cost	4.64%	4.20%	5.10%
Discount rate	4.41%
People's Qualified Plan [Member] | Other Postretirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate used to determine benefit obligation	4.40%	4.60%	4.20%
Discount rate used to calculate net periodic benefit cost	4.60%	4.20%	5.10%
Chittenden Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	$ 47,600,000
Amortization of unrecognized gain loss over average remaining life of plan participants	9 years
Expected employer contributions	$ 0
Chittenden Qualified Plan [Member] | Qualified Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, projected benefit obligations	$ 43,000,000
Discount rate used to determine benefit obligation	4.16%	4.45%	4.00%
Discount rate used to calculate net periodic benefit cost	4.45%	4.00%	4.90%
Discount rate	4.16%

Employee Benefit Plans - Change

Employee Benefit Plans - Changes in Benefit Obligations and Plan Assets (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Beginning of year	$ 466.5
End of year	478	$ 466.5
Other assets	967.2	855.5
Other liabilities	(520.2)	(457.3)
Funded status at end of year	(13.6)	(14)
Other Postretirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Beginning of year	14	14.6
Service cost	0.3	0.3	$ 0.1
Interest cost	0.6	0.6	0.5
Actuarial loss (gain)	(0.2)	(0.6)
Benefits paid	(1.1)	(0.9)
End of year	13.6	14	14.6
Other liabilities	(13.6)	(14)
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Beginning of year	480.4	515.3
Interest cost	18.6	21.1	21.4
Actuarial loss (gain)	10.2	(36.7)
Benefits paid	(17.8)	(16.6)
Settlements	(2.1)	(2.7)
End of year	489.3	480.4	515.3
Other assets	29.5	26.6
Other liabilities	(40.8)	(40.5)
Funded status at end of year	(11.3)	(13.9)
Fair Value of Plan Assets [Member] | Other Postretirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	1.1	0.9
Benefits paid	(1.1)	(0.9)
Funded status at end of year	(13.6)	(14)
Fair Value of Plan Assets [Member] | Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Beginning of year	466.5	439.9
Actual return on assets	29.2	(6.4)
Employer contributions	2.2	52.3
Benefits paid	(17.8)	(16.6)
Settlements	2.1	2.7
End of year	478	466.5	$ 439.9
Funded status at end of year	$ (11.3)	$ (13.9)

Employee Benefit Plans - Cha117

Employee Benefit Plans - Changes in Benefit Obligations and Plan Assets (Parenthetical) (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2015USD ($)
People's Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 40
Chittenden Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 10

Employee Benefit Plans - Accumu

Employee Benefit Plans - Accumulated and Projected Benefit Obligations (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, accumulated benefit obligations	$ 68.1	$ 63.9
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, accumulated benefit obligations	489.3	480.4
Defined benefit plan, projected benefit obligations	489.3	480.4	$ 515.3
Qualified Plans [Member] | Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, accumulated benefit obligations	448.5	439.9
Defined benefit plan, projected benefit obligations	448.5	439.9
Supplemental Plans [Member] | Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, accumulated benefit obligations	40.8	40.5
Defined benefit plan, projected benefit obligations	$ 40.8	$ 40.5

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, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain)	$ 15.5	$ 3.5	$ 98.5
Total pre-tax changes recognized in other comprehensive loss	9.1	(4.6)	91.1
Other Postretirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0.3	0.3	0.1
Interest cost	0.6	0.6	0.5
Recognized net actuarial loss	0.2	0.3
Recognized prior service credit		(0.2)	(0.2)
Net periodic benefit (income) expense	1.1	1	0.4
Net actuarial loss (gain)	(0.4)	(0.9)	4.8
Prior service credit		0.2	0.2
Total pre-tax changes recognized in other comprehensive loss	(0.4)	(0.7)	5
Total recognized in net periodic benefit (income) expense and other comprehensive loss	0.7	0.3	5.4
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	18.6	21.1	21.4
Expected return on plan assets	(34.6)	(34.4)	(32)
Recognized net actuarial loss	6.1	7.7	5.1
Recognized prior service credit	(0.8)	(0.8)	(0.8)
Settlements	0.8	1.2	3.3
Net periodic benefit (income) expense	(9.9)	(5.2)	(3)
Net actuarial loss (gain)	8.7	(4.7)	85.3
Prior service credit	0.8	0.8	0.8
Total pre-tax changes recognized in other comprehensive loss	9.5	(3.9)	86.1
Total recognized in net periodic benefit (income) expense and other comprehensive loss	$ (0.4)	$ (9.1)	$ 83.1

Employee Benefit Plans - Pre-Ta

Employee Benefit Plans - Pre-Tax Amounts in Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Other Postretirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	$ 3.8	$ 4.2
Total pre-tax amounts included in AOCL	3.8	4.2
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	228	219.3
Prior service credit	(1.2)	(2)
Total pre-tax amounts included in AOCL	$ 226.8	$ 217.3

Employee Benefit Plans - Assump

Employee Benefit Plans - Assumptions Used in Determining Benefit Obligations and Net Periodic Benefit Expense (Detail)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Qualified Plans [Member]
Weighted-average assumptions used to determine net periodic benefit (income) expense for the years ended December 31:
Expected return on plan assets	7.25%	7.50%	8.00%
People's Qualified Plan [Member] | Qualified Plans [Member]
Weighted-average assumptions used to determine benefit obligations at December 31:
Discount rate	4.41%	4.64%	4.20%
Weighted-average assumptions used to determine net periodic benefit (income) expense for the years ended December 31:
Discount rate	4.64%	4.20%	5.10%
Chittenden Qualified Plan [Member] | Qualified Plans [Member]
Weighted-average assumptions used to determine benefit obligations at December 31:
Discount rate	4.16%	4.45%	4.00%
Weighted-average assumptions used to determine net periodic benefit (income) expense for the years ended December 31:
Discount rate	4.45%	4.00%	4.90%
Other Postretirement Plan [Member]
Assumed health care cost trend rates at December 31:
Health care cost trend rate assumed for next year	6.50%	6.80%	7.05%
Rate to which the cost trend rate is assumed to decline (the ultimate trend rate)	4.50%	4.50%	4.50%
Year that the rate reaches the ultimate trend rate	2,037	2,027	2,027
Other Postretirement Plan [Member] | People's Qualified Plan [Member]
Weighted-average assumptions used to determine benefit obligations at December 31:
Discount rate	4.40%	4.60%	4.20%
Weighted-average assumptions used to determine net periodic benefit (income) expense for the years ended December 31:
Discount rate	4.60%	4.20%	5.10%

Employee Benefit Plans - Schedu

Employee Benefit Plans - Schedule of Impact in 2016 Due to Change in Accounting Estimate for Qualified Plans (Detail) - Adjustments for New Accounting Pronouncement [Member] $ in Millions	12 Months Ended
	Dec. 31, 2016USD ($)
People's Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	4.03%
Discount rates that would have been used to measure net periodic benefit income under prior actuarial methodology, Interest cost	4.64%
Increase in net periodic benefit income in 2016 using specific spot rates, Interest cost	$ 2.5
Chittenden Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.70%
Discount rates that would have been used to measure net periodic benefit income under prior actuarial methodology, Interest cost	4.45%
Increase in net periodic benefit income in 2016 using specific spot rates, Interest cost	$ 0.3

Employee Benefit Plans - Assets

Employee Benefit Plans - Assets Allocation (Detail)	12 Months Ended
	Dec. 31, 2016
Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Policy Target Rate	5.00%
Policy Range Rate Minimum	0.00%
Policy Range Rate Maximum	20.00%
Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Policy Target Rate	65.00%
Policy Range Rate Minimum	50.00%
Policy Range Rate Maximum	75.00%
Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Policy Target Rate	30.00%
Policy Range Rate Minimum	20.00%
Policy Range Rate Maximum	50.00%

Employee Benefit Plans - Fair V

Employee Benefit Plans - Fair Value of Assets in Qualified Plans (Detail)	Dec. 31, 2016	Dec. 31, 2015
People's Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	100.00%	100.00%
Chittenden Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	100.00%	100.00%
Equity Securities [Member] | People's Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	69.00%	69.00%
Equity Securities [Member] | Chittenden Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	67.00%	69.00%
Cash and Fixed Income Securities [Member] | People's Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	31.00%	31.00%
Cash and Fixed Income Securities [Member] | Chittenden Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	33.00%	31.00%

Employee Benefit Plans - Plan A

Employee Benefit Plans - Plan Assets Measured at Fair Value (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	$ 478	$ 466.5
Corporate, Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	214.8	215.3
Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	11.7	26.3
Equity Securities [Member] | Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	114.8	105.8
Fixed Income Securities [Member] | Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	21.4	21.8
Fixed Income Securities [Member] | Corporate [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	102.9	81.6
Fixed Income Securities [Member] | State and Municipal [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	6.8	10.5
Fixed Income Securities [Member] | Other [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	5.6	5.2
Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	226.5	241.6
Level 1 [Member] | Corporate, Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	214.8	215.3
Level 1 [Member] | Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	11.7	26.3
Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	251.5	224.9
Level 2 [Member] | Equity Securities [Member] | Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	114.8	105.8
Level 2 [Member] | Fixed Income Securities [Member] | Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	21.4	21.8
Level 2 [Member] | Fixed Income Securities [Member] | Corporate [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	102.9	81.6
Level 2 [Member] | Fixed Income Securities [Member] | State and Municipal [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	6.8	10.5
Level 2 [Member] | Fixed Income Securities [Member] | Other [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at fair value	$ 5.6	$ 5.2

Employee Benefit Plans - Employ

Employee Benefit Plans - Employee Stock Ownership Plan - Additional Information (Detail) - USD ($) $ in Millions	Apr. 30, 2007	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
ESOP, shares to be purchased	10,453,575
ESOP loan	$ 216.8	$ 184.9
Loan repayments expected annual through 2036		18.8
Cash dividends paid on unallocated ESOP shares		$ 5	$ 5.1	$ 5.3
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		3,484,525
Unallocated common stock of Employee Stock Ownership Plan, shares		6,969,050	7,300,000
Fair value of deferred ESOP shares		$ 134.9
ESOP compensation expense		$ 5.5	$ 5.4	$ 5.1

Employee Benefit Plans - Emp127

Employee Benefit Plans - Employee Savings Plans - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
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	$ 39.6	$ 36.5
Related benefit obligation	27.3
Employee savings plan expense	455.6	449.5	$ 436
Employee Savings Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Trust assets	8
Employee savings plan expense	$ 22.9	$ 22.1	$ 20.1
Employee Savings Plan [Member] | 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)	3 Months Ended	12 Months Ended
	Jun. 30, 2014shares	Dec. 31, 2016USD ($)$ / sharesshares	Dec. 31, 2015USD ($)$ / sharesshares	Dec. 31, 2014USD ($)$ / sharesshares	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted, vesting period						4 years
Options granted, vesting period					1 year
Expense related to share-based awards		$ 15,200,000	$ 17,100,000	$ 14,900,000
Long-term incentive plan | shares		3,187,500	5,221,992	4,953,624
Total cost of shares repurchased and retired		$ 3,400,000	$ 3,200,000	$ 3,000,000
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expense related to share-based awards		$ 5,700,000	6,800,000	5,400,000
Unamortized cost for share-based awards estimated forfeiture rate		5.00%
Unamortized cost for unvested options and awards		$ 5,300,000
Weighted-average vesting period, years		1 year 4 months 24 days
Intrinsic value of stock options exercised		$ 15,600,000	5,100,000	1,100,000
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expense related to share-based awards		$ 6,500,000	9,400,000	8,700,000
Unamortized cost for share-based awards estimated forfeiture rate		0.05%
Unamortized cost for unvested options and awards		$ 6,400,000
Weighted-average vesting period, years		1 year 3 months 18 days
Fair value of restricted stock awards		$ 9,800,000	$ 9,400,000	$ 10,300,000
Minimum tax withholding obligations upon the vesting of restricted stock awards granted | shares		289,992	230,459	229,635
Total cost of shares repurchased and retired		$ 3,400,000	$ 3,200,000	$ 3,000,000
Share based compensation arrangement by share based payment award grants in period weighted average grant date fair value | $ / shares		$ 14.66	$ 14.88	$ 14.01
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expense related to share-based awards		$ 2,100,000
Unamortized cost for share-based awards estimated forfeiture rate		5.00%
Unamortized cost for unvested options and awards		$ 5,300,000
Weighted-average vesting period, years		2 years 2 months 12 days
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%
Options granted, vesting period					2 years	2 years
Options granted, vesting period					3 years	3 years
New awards granted | shares	0
Long-term incentive plan | shares		3,187,500	5,221,992	562,355
Weighted-average grant-date fair value of options | $ / shares		$ 1.33	$ 1.46	$ 1.51
Dividend yield		4.60%	4.40%	4.70%
Expected volatility rate		20.00%	20.00%	22.00%
Risk-free interest rate		1.30%	1.60%	1.60%
Expected option life, years		5 years	5 years	5 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 | shares		1,192,500
Reserved shares remaining, available for future awards | shares		193,051
Expense related to share-based awards		$ 900,000	$ 900,000	$ 800,000
New awards granted | shares		58,020	62,690	57,330
Director's equity compensation plan fair value		$ 95,000
Share based compensation arrangement by share based payment award grants in period weighted average grant date fair value | $ / shares		$ 16.24	$ 15.23	$ 14.63
2014 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock reserved for issuance under the Directors' Equity Plan | shares		34,000,000
Reserved shares remaining, available for future awards | shares		15,833,453
Number of shares depleted, Terms		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.
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		5.32
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		7.98
Options granted, vesting period		3 years
Share based compensation arrangement by share based payment award grants in period weighted average grant date fair value | $ / shares		$ 15.22
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%
Long-term incentive plan | shares		4,391,269

Stock-Based Compensation Pla129

Stock-Based Compensation Plans - Summary of Performance Share Activity (Detail) - 2014 Plan [Member] - Performance Shares [Member]	12 Months Ended
	Dec. 31, 2016$ / sharesshares
Shares
Shares, granted | shares	568,596
Shares, forfeited | shares	(15,664)
Shares, vested | shares	(947)
Unvested shares outstanding, ending balance | shares	551,985
Weighted-average grant date fair value
Weighted-average grant date fair value, granted | $ / shares	$ 15.22
Weighted-average grant date fair value, forfeited | $ / shares	15.22
Weighted-average grant date fair value, vested | $ / shares	15.22
Unvested shares outstanding, Weighted-Average Grant Date Fair Value, Ending balance | $ / shares	$ 15.22

Stock Based Compensation Pla130

Stock Based Compensation Plans - Summary of Stock Option Incentive Plan (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Options outstanding Beginning Balance	19,677,424	17,798,405	14,217,074
Granted	3,187,500	5,221,992	4,953,624
Forfeited	(632,869)	(1,290,396)	(896,003)
Exercised	(5,676,130)	(2,052,577)	(476,290)
Options outstanding at Ending Balance	16,555,925	19,677,424	17,798,405
Options Exercisable Ending Balance	8,837,386
Options outstanding Weighted Exercise Price Beginning Balance	$ 15.13	$ 15.11	$ 15.43
Granted	14.57	14.85	13.94
Forfeited	15.65	16.57	15.13
Exercised	15.60	13.35	12.48
Options outstanding Weighted Average Exercise Price Ending Balance Years	14.84	$ 15.13	$ 15.11
Options Exercisable Weighted Average Exercise Price	$ 15.08
Options Outstanding Weighted Average Remaining Contractual Term, in years	6 years 4 months 24 days
Options Exercisable Weighted Average Remaining Contractual Term	4 years 8 months 12 days
Options Outstanding Aggregate Intrinsic Value	$ 75.2
Options Exercisable Aggregate Intrinsic Value	$ 38.2

Stock Based Compensation Pla131

Stock Based Compensation Plans - Summary of Option Outstanding and Exercisable (Detail)	12 Months Ended
	Dec. 31, 2016$ / sharesshares
11.53 - 13.05 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Exercise Price minimum	$ 11.53
Options Exercise Price maximum	$ 13.05
Number of options outstanding | shares	1,717,527
Remaining Life	5 years 8 months 12 days
Exercise Price	$ 12.85
Number of options exercisable | shares	1,717,527
Weighted Average Exercise Price	$ 12.85
13.42 - 15.80 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Exercise Price minimum	13.42
Options Exercise Price maximum	$ 15.80
Number of options outstanding | shares	12,425,506
Remaining Life	7 years 7 months 6 days
Exercise Price	$ 14.51
Number of options exercisable | shares	4,706,967
Weighted Average Exercise Price	$ 14.42
16.07 - 17.76 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Exercise Price minimum	16.07
Options Exercise Price maximum	$ 17.76
Number of options outstanding | shares	734,089
Remaining Life	1 year 9 months 18 days
Exercise Price	$ 16.85
Number of options exercisable | shares	734,089
Weighted Average Exercise Price	$ 16.85
18.10 - 21.63 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Exercise Price minimum	18.10
Options Exercise Price maximum	$ 21.63
Number of options outstanding | shares	1,678,803
Remaining Life	9 months 18 days
Exercise Price	$ 18.45
Number of options exercisable | shares	1,678,803
Weighted Average Exercise Price	$ 18.45

Stock Based Compensation Pla132

Stock Based Compensation Plans - Summary of Stock Award Incentive Plans (Detail) - Restricted Stock [Member] - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted	344,812	568,273	660,617
Forfeited	(41,684)	(80,303)	(95,700)
Vested	(649,363)	(623,185)	(730,600)
Unvested restricted shares outstanding	886,082	1,232,317	1,367,532	1,533,215
Granted	$ 14.66	$ 14.88	$ 14.01
Forfeited	14.34	14.23	13.53
Vested	13.79	13.33	13.22
Unvested restricted shares outstanding, Weighted-Average Grant Date Fair Value	$ 14.59	$ 14.14	$ 13.47	$ 13.12

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value transfers between level 1 and level 2	$ 0	$ 0
GSE Residential Mortgage-Backed Securities and CMOs [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	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 ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account securities	$ 6.8	$ 6.7
Securities available for sale, at fair value	4,409.9	4,527.7
Other assets	967.2	855.5
Fair Values, Assets	174	158.2
Fair Values, Liabilities	121.7	109.5
Fair value of total assets measured at fair value on a recurring basis	4,630.3	4,729.1
Fair value of total liabilities measured at fair value on a recurring basis	121.7	109.5
Exchange Traded Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	32.6	29.4
Fixed Income Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	4.3	5.1
Equity Mutual Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	2.7	2
US Treasury [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account securities	6.8	6.7
U.S. Treasury and Agency [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	859.7	362.8
GSE Residential Mortgage-Backed Securities and CMOs [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	3,550	4,164.7
Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	0.2	0.2
Interest Rate Swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Values, Assets	173.1	157
Fair Values, Liabilities	121	108.5
Foreign Exchange Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Values, Assets	0.6	0.6
Fair Values, Liabilities	0.3	0.2
Forward Commitments to Sell Residential Mortgage Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Values, Assets	0.3	0.6
Interest Rate-Lock Commitments on Residential Mortgage Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Values, Liabilities	0.4	0.8
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of total assets measured at fair value on a recurring basis	901.8	400.9
Level 1 [Member] | Exchange Traded Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	32.6	29.4
Level 1 [Member] | Equity Mutual Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	2.7	2
Level 1 [Member] | US Treasury [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account securities	6.8	6.7
Level 1 [Member] | U.S. Treasury and Agency [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	859.7	362.8
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of total assets measured at fair value on a recurring basis	3,728.5	4,328.2
Fair value of total liabilities measured at fair value on a recurring basis	121.7	109.5
Level 2 [Member] | Fixed Income Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	4.3	5.1
Level 2 [Member] | GSE Residential Mortgage-Backed Securities and CMOs [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	3,550	4,164.7
Level 2 [Member] | Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	0.2	0.2
Level 2 [Member] | Interest Rate Swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Values, Assets	173.1	157
Fair Values, Liabilities	121	108.5
Level 2 [Member] | Foreign Exchange Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Values, Assets	0.6	0.6
Fair Values, Liabilities	0.3	0.2
Level 2 [Member] | Forward Commitments to Sell Residential Mortgage Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Values, Assets	0.3	0.6
Level 2 [Member] | Interest Rate-Lock Commitments on Residential Mortgage Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Values, Liabilities	$ 0.4	$ 0.8

Fair Value Measurements - As135

Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Recurring Basis (Parenthetical) (Detail) - USD ($)	Dec. 31, 2016	Dec. 31, 2015
Maximum [Member] | Risk Participation Agreements [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value of Derivatives, Net	$ 100,000	$ 100,000

Fair Value Measurements - As136

Fair Value Measurements - Assets Measured at Fair Value on Non-Recurring Basis (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale	$ 39.3	$ 34.5
Impaired loans	55.9	49.1
REO and repossessed assets	19.3	22.1
Total assets measured at fair value on non-recurring basis	114.5	105.7
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale	39.3	34.5
Total assets measured at fair value on non-recurring basis	39.3	34.5
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	55.9	49.1
REO and repossessed assets	19.3	22.1
Total assets measured at fair value on non-recurring basis	$ 75.2	$ 71.2

Fair Value Measurements - As137

Fair Value Measurements - Assets Measured at Fair Value on Non-Recurring Basis (Parenthetical) (Detail) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	$ 55,900,000				$ 49,100,000				$ 55,900,000	$ 49,100,000
Charge-offs to the allowance for loan losses related to loans	7,700,000	$ 8,400,000	$ 10,000,000	$ 10,500,000	9,700,000	$ 6,200,000	$ 7,700,000	$ 9,800,000	36,600,000	33,400,000	$ 40,600,000
Repossessed assets	7,200,000				9,500,000				7,200,000	9,500,000
Write downs and net loss on sale of foreclosed/repossessed assets charged to non-interest expense total	217,200,000	$ 221,400,000	$ 212,900,000	$ 217,300,000	217,000,000	$ 214,200,000	$ 211,800,000	$ 217,600,000	868,800,000	860,600,000	841,500,000
Write Down Net Loss on Sale of Foreclosed Assets [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									3,200,000	2,800,000
Residential Mortgage Loan [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value adjustments									0	0
Real estate owned	8,100,000				7,100,000				8,100,000	7,100,000
Commercial Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	40,800,000								40,800,000
Commercial Real Estate Loan [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Real estate owned	4,000,000				5,500,000				4,000,000	5,500,000
Impaired Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Charge-offs to the allowance for loan losses related to loans									3,800,000	6,700,000
REO and Repossessed Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Charge-offs to the allowance for loan losses related to loans									3,700,000	1,800,000
Retail Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	15,100,000								15,100,000
Charge-offs to the allowance for loan losses related to loans									8,600,000	7,900,000	$ 8,200,000
Retail Loans [Member] | Residential Mortgage Loan [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	$ 13,100,000				$ 14,000,000				$ 13,100,000	$ 14,000,000

Fair Value Measurements - Carry

Fair Value Measurements - Carrying Amounts and Estimated Fair Values of Financial Instruments (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	$ 432.4	$ 334.8
Short-term investments	181.7	380.5
Securities held to maturity	2,005.4	1,609.6
FHLB and FRB stock	315.8	305.4
Total loans, net	29,459.7	28,150.8
Time deposits	4,542.2	4,818.1
Other deposits	25,318.6	23,599.3
FHLB advances	3,061.1	3,463.8
Federal funds purchased	617	374
Customer repurchase agreements	343.3	469.5
Other borrowings	35.4
Notes and debentures	1,030.1	1,033.1
Estimated Fair Value Measurements [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	432.4	334.8
Short-term investments	181.7	380.5
Securities held to maturity	2,012.7	1,662.5
FHLB and FRB stock	315.8	305.4
Total loans, net	29,266.5	28,209
Time deposits	4,539.7	4,836.5
Other deposits	25,318.6	23,599.3
FHLB advances	3,064.4	3,468.7
Federal funds purchased	617	374
Customer repurchase agreements	343.3	469.5
Other borrowings	35.4
Notes and debentures	1,000	1,012.9
Estimated Fair Value Measurements [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	432.4	334.8
Estimated Fair Value Measurements [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	181.7	380.5
Securities held to maturity	2,011.2	1,661
FHLB and FRB stock	315.8	305.4
Total loans, net	6,028.4	5,315.3
Time deposits	4,539.7	4,836.5
Other deposits	25,318.6	23,599.3
FHLB advances	3,064.4	3,468.7
Federal funds purchased	617	374
Customer repurchase agreements	343.3	469.5
Other borrowings	35.4
Notes and debentures	1,000	1,012.9
Estimated Fair Value Measurements [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities held to maturity	1.5	1.5
Total loans, net	23,238.1	22,893.7
Cash and due from banks	432.4	334.8
Short-term investments	181.7	380.5
Securities held to maturity	2,005.4	1,609.6
FHLB and FRB stock	315.8	305.4
Time deposits	4,542.2	4,818.1
FHLB advances	3,061.1	3,463.8	$ 2,291.7
Federal funds purchased	617	374	486
Customer repurchase agreements	343.3	469.5	913
Other borrowings	35.4		$ 1
Notes and debentures	$ 1,030.1	$ 1,033.1

Fair Value Measurements - Ca139

Fair Value Measurements - Carrying Amounts and Estimated Fair Values of Financial Instruments (Parenthetical) (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Impaired loans	$ 55.9	$ 49.1

Legal Proceedings and Lease 140

Legal Proceedings and Lease Commitments - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
2,017	$ 58.8
2,018	54.3
2,019	49.5
2,020	45.6
2,021	42.5
2022 through 2055	106.6
Rent expense under operating leases	$ 59.8	$ 58.9	$ 59.1

Financial Instruments - Summary

Financial Instruments - Summary of Contractual or Notional Amounts of Financial Instruments (Detail) - USD ($)	Dec. 31, 2016	Dec. 31, 2015
Commercial and Industrial [Member]
Derivative Instruments And Hedging Activities [Line Items]
Loan origination commitments and unadvanced of credit	$ 4,029,600,000	$ 3,337,000,000
Home Equity and Other Consumer [Member]
Derivative Instruments And Hedging Activities [Line Items]
Loan origination commitments and unadvanced of credit	2,800,700,000	2,558,400,000
Commercial Real Estate [Member]
Derivative Instruments And Hedging Activities [Line Items]
Loan origination commitments and unadvanced of credit	701,600,000	831,000,000
Equipment Financing [Member]
Derivative Instruments And Hedging Activities [Line Items]
Loan origination commitments and unadvanced of credit	179,900,000	241,000,000
Residential Mortgage [Member]
Derivative Instruments And Hedging Activities [Line Items]
Loan origination commitments and unadvanced of credit	69,600,000	93,300,000
Forward Commitments to Sell Residential Mortgage Loans [Member]
Derivative Instruments And Hedging Activities [Line Items]
Derivative Financial Instruments	48,600,000	44,700,000
Interest Rate-Lock Commitments on Residential Mortgage Loans [Member]
Derivative Instruments And Hedging Activities [Line Items]
Derivative Financial Instruments	57,000,000	65,400,000
Stand-By Letters of Credit [Member]
Derivative Instruments And Hedging Activities [Line Items]
Lending-Related Financial Instruments	105,600,000	121,500,000
Commercial Letters of Credit [Member]
Derivative Instruments And Hedging Activities [Line Items]
Lending-Related Financial Instruments	3,600,000	3,400,000
Interest Rate Swaps [Member]
Derivative Instruments And Hedging Activities [Line Items]
Derivative Financial Instruments	125,000,000
Interest Rate Swaps [Member] | Subordinated Notes [Member]
Derivative Instruments And Hedging Activities [Line Items]
Derivative Financial Instruments	500,000,000	500,000,000
Interest Rate Swaps [Member] | Customer [Member]
Derivative Instruments And Hedging Activities [Line Items]
Derivative Financial Instruments	5,612,200,000	4,644,800,000
Interest Rate Swaps [Member] | Counterparty [Member]
Derivative Instruments And Hedging Activities [Line Items]
Derivative Financial Instruments	5,620,200,000	4,644,800,000
Risk Participation Agreements [Member]
Derivative Instruments And Hedging Activities [Line Items]
Derivative Financial Instruments	251,900,000	244,400,000
Foreign Exchange Contracts [Member]
Derivative Instruments And Hedging Activities [Line Items]
Derivative Financial Instruments	$ 101,200,000	$ 56,700,000

Financial Instruments - Additio

Financial Instruments - Additional Information (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Derivative [Line Items]
Average period extended for letter of credit		1 year
Loan commitments and letters of credit		$ 2,300,000	$ 2,500,000
Aggregate fair value of derivative instruments		7,500,000
Collateral posted in normal course of business		5,400,000
Additional collateral required if senior unsecured debt had fallen below investment grade		2,100,000
Subordinated notes		$ 125,000,000
Subordinated notes fixed interest rate		5.80%
Unrealized gain on derivatives		$ (200,000)	(1,100,000)	$ (900,000)
Subordinated Notes [Member]
Derivative [Line Items]
LIBOR basis points		Three-month LIBOR
Basis points		0.685%
Interest Rate Swaps [Member]
Derivative [Line Items]
Derivative; fixed-rate (Pay fixed/receive floating interest Interest rate swap)		1.99%
Notional amount of derivatives		$ 125,000,000
Interest Rate Swaps [Member] | Subordinated Notes [Member]
Derivative [Line Items]
Notional amount of derivatives		500,000,000	$ 500,000,000
Interest Rate Swaps [Member] | Fair Value [Member]
Derivative [Line Items]
Subordinated notes		$ 400,000,000
LIBOR basis points		Three-month LIBOR
Basis points		1.265%
Notional amount of derivatives		$ 375,000,000
Treasury Forward Interest Rate Locks ("T-Locks") [Member]
Derivative [Line Items]
Derivative instruments hedge description		To hedge the risk that the 10-year U.S. Treasury yield would rise
Unrealized gain on derivatives	$ 900,000
Period hedged items affected earnings, years	10 years
Total unrecognized gain		$ 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, 2016	Dec. 31, 2015
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Forward commitments to sell residential mortgage loans	$ 160,400,000	$ 139,300,000
Total, Derivatives Designated as Hedging Instruments, Fair Values, Assets	13,600,000	18,900,000
Total Derivatives Fair value,Assets	174,000,000	158,200,000
Total, Derivatives Not Designated as Hedging Instruments, Fair Values, Liabilities	121,600,000	108,900,000
Total, Derivatives Designated as Hedging Instruments, Fair Values, Liabilities	100,000	600,000
Fair Values, Liabilities	121,700,000	109,500,000
Forward Commitments to Sell Residential Mortgage Loans [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amounts	48,600,000	44,700,000
Forward commitments to sell residential mortgage loans	300,000	600,000
Total Derivatives Fair value,Assets	300,000	600,000
Interest Rate-Lock Commitments on Residential Mortgage Loans [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amounts	57,000,000	65,400,000
Derivatives Not Designated as Hedging Instruments, Foreign exchange contracts, Fair Values, Liabilities	400,000	800,000
Fair Values, Liabilities	400,000	800,000
Risk Participation Agreements [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amounts	251,900,000	244,400,000
Interest Rate Swaps [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amounts	125,000,000
Interest Rate Swaps [Member] | Fair Value [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amounts	375,000,000
Interest Rate Swaps [Member] | Commercial Customers [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amounts	5,612,200,000	4,644,800,000
Derivatives Not Designated as Hedging Instruments, Interest rate swaps, Fair Values, Assets	93,900,000	130,900,000
Derivatives Not Designated as Hedging Instruments, Foreign exchange contracts, Fair Values, Liabilities	46,900,000	2,600,000
Interest Rate Swaps [Member] | Institutional Counterparties [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amounts	5,620,200,000	4,644,800,000
Derivatives Not Designated as Hedging Instruments, Interest rate swaps, Fair Values, Assets	65,600,000	7,200,000
Derivatives Not Designated as Hedging Instruments, Foreign exchange contracts, Fair Values, Liabilities	74,000,000	105,300,000
Interest Rate Swaps [Member] | Subordinated Notes [Member] | Cash Flow [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amounts	125,000,000	125,000,000
Derivative Assets Designated as Hedging Instruments, Fair Values, Assets	0	0
Total, Derivatives Designated as Hedging Instruments, Fair Values, Liabilities	100,000	600,000
Interest Rate Swaps [Member] | Subordinated Notes [Member] | Fair Value [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amounts	375,000,000	375,000,000
Derivative Assets Designated as Hedging Instruments, Fair Values, Assets	13,600,000	18,900,000
Total, Derivatives Designated as Hedging Instruments, Fair Values, Liabilities	0	0
Foreign Exchange Contracts [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amounts	101,200,000	56,700,000
Derivatives Not Designated as Hedging Instruments, Foreign exchange contracts, Fair Values, Assets	600,000	600,000
Total Derivatives Fair value,Assets	600,000	600,000
Derivatives Not Designated as Hedging Instruments, Interest rate swaps, Fair Values, Liabilities	300,000	200,000
Fair Values, Liabilities	$ 300,000	$ 200,000

Financial Instruments - Sche144

Financial Instruments - Schedule of Notional Amounts and Fair Values of Derivatives Outstanding (Parenthetical) (Detail) - USD ($)	Dec. 31, 2016	Dec. 31, 2015
Risk Participation Agreements [Member] | Maximum [Member] | Derivatives Not Designated as Hedging Instruments [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Fair Value of Derivatives, Net	$ 100,000	$ 100,000

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, 2016	Dec. 31, 2015	Dec. 31, 2014
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of Pre-Tax Gain (Loss) Recognized in Earnings	$ 20.5	$ 22.6	$ 12.8
Amount of Pre-Tax Gain (Loss) Recognized in AOCL	(0.2)	(1.1)	(0.9)
Derivatives Not Designated as Hedging Instruments [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of Pre-Tax Gain (Loss) Recognized in Earnings	13.7	14.5	8.9
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	0.3	(0.1)	(0.5)
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	(0.2)	0.1	0.4
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	(11.1)	104.8	165.4
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	24.8	(90.3)	(156.9)
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	(0.6)	0.2	0.4
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	0.5	(0.2)	0.1
Derivatives Designated as Hedging Instruments [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of Pre-Tax Gain (Loss) Recognized in Earnings	6.8	8.1	3.9
Amount of Pre-Tax Gain (Loss) Recognized in AOCL	(0.2)	(1.1)	(0.9)
Derivatives Designated as Hedging Instruments [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
Derivatives Designated as Hedging Instruments [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	(0.8)	(1.3)	(1.4)
Amount of Pre-Tax Gain (Loss) Recognized in AOCL	(0.2)	(1.1)	(0.9)
Derivatives Designated as Hedging Instruments [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	$ 7.5	$ 9.3	$ 5.2

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, 2016	Dec. 31, 2015
Offsetting Assets And Liabilities [Line Items]
Financial assets, Gross Amount Recognized	$ 174	$ 158.2
Financial liabilities, Gross Amount Recognized	121.7	109.5
Financial assets, Gross Amount Recognized	79.8	26.6
Financial assets, Gross Amount Offset	0	0
Financial assets, Net Amount Presented	79.8	26.6
Financial assets, Financial Instruments	(58.3)	(25.9)
Financial assets, Collateral	(20.9)
Financial assets, Net Amount	0.6	0.7
Financial liabilities, Gross Amount Recognized	74.4	106.1
Financial liabilities, Gross Amount Offset	0	0
Financial liabilities, Net Amount Presented	74.4	106.1
Financial liabilities, Financial Instruments	(58.3)	(25.9)
Financial liabilities, Collateral	(13.4)	(79.1)
Financial liabilities, Net Amount	2.7	1.1
Foreign Exchange Contracts [Member]
Offsetting Assets And Liabilities [Line Items]
Financial assets, Gross Amount Recognized	0.6	0.6
Financial assets, Gross Amount Offset	0	0
Financial assets, Net Amount Presented	0.6	0.6
Financial assets, Net Amount	0.6	0.6
Financial liabilities, Gross Amount Recognized	0.3	0.2
Financial liabilities, Gross Amount Offset	0	0
Financial liabilities, Net Amount Presented	0.3	0.2
Financial liabilities, Net Amount	0.3	0.2
Counterparty A [Member] | Interest Rate Swaps [Member]
Offsetting Assets And Liabilities [Line Items]
Financial assets, Gross Amount Recognized	1.9	0.6
Financial assets, Gross Amount Offset	0	0
Financial assets, Net Amount Presented	1.9	0.6
Financial assets, Financial Instruments	(1.9)	(0.6)
Financial liabilities, Gross Amount Recognized	4.3	8.4
Financial liabilities, Gross Amount Offset	0	0
Financial liabilities, Net Amount Presented	4.3	8.4
Financial liabilities, Financial Instruments	(1.9)	(0.6)
Financial liabilities, Collateral	(2.4)	(7.8)
Counterparty B [Member] | Interest Rate Swaps [Member]
Offsetting Assets And Liabilities [Line Items]
Financial assets, Gross Amount Recognized	1	0.7
Financial assets, Gross Amount Offset	0	0
Financial assets, Net Amount Presented	1	0.7
Financial assets, Financial Instruments	(1)	(0.7)
Financial liabilities, Gross Amount Recognized	7.7	10.4
Financial liabilities, Gross Amount Offset	0	0
Financial liabilities, Net Amount Presented	7.7	10.4
Financial liabilities, Financial Instruments	(1)	(0.7)
Financial liabilities, Collateral	(6.7)	(9.7)
Counterparty C [Member] | Interest Rate Swaps [Member]
Offsetting Assets And Liabilities [Line Items]
Financial assets, Gross Amount Recognized	1.7	0.6
Financial assets, Gross Amount Offset	0	0
Financial assets, Net Amount Presented	1.7	0.6
Financial assets, Financial Instruments	(1.7)	(0.6)
Financial liabilities, Gross Amount Recognized	3.4	5.1
Financial liabilities, Gross Amount Offset	0	0
Financial liabilities, Net Amount Presented	3.4	5.1
Financial liabilities, Financial Instruments	(1.7)	(0.6)
Financial liabilities, Collateral	(1.1)	(4.5)
Financial liabilities, Net Amount	0.6
Counterparty D [Member] | Interest Rate Swaps [Member]
Offsetting Assets And Liabilities [Line Items]
Financial assets, Gross Amount Recognized	3.4	0.7
Financial assets, Gross Amount Offset	0	0
Financial assets, Net Amount Presented	3.4	0.7
Financial assets, Financial Instruments	(3.4)	(0.7)
Financial liabilities, Gross Amount Recognized	6.9	8.9
Financial liabilities, Gross Amount Offset	0	0
Financial liabilities, Net Amount Presented	6.9	8.9
Financial liabilities, Financial Instruments	(3.4)	(0.7)
Financial liabilities, Collateral	(1.7)	(7.3)
Financial liabilities, Net Amount	1.8	0.9
Counterparty E [Member] | Interest Rate Swaps [Member]
Offsetting Assets And Liabilities [Line Items]
Financial assets, Gross Amount Recognized	69.6	22.6
Financial assets, Gross Amount Offset	0	0
Financial assets, Net Amount Presented	69.6	22.6
Financial assets, Financial Instruments	(50)	(22.6)
Financial assets, Collateral	(19.6)
Financial liabilities, Gross Amount Recognized	50	69.5
Financial liabilities, Gross Amount Offset	0	0
Financial liabilities, Net Amount Presented	50	69.5
Financial liabilities, Financial Instruments	(50)	(22.6)
Financial liabilities, Collateral		(46.9)
Other Counterparties [Member] | Interest Rate Swaps [Member]
Offsetting Assets And Liabilities [Line Items]
Financial assets, Gross Amount Recognized	1.6	0.8
Financial assets, Gross Amount Offset	0	0
Financial assets, Net Amount Presented	1.6	0.8
Financial assets, Financial Instruments	(0.3)	(0.7)
Financial assets, Collateral	(1.3)
Financial assets, Net Amount		0.1
Financial liabilities, Gross Amount Recognized	1.8	3.6
Financial liabilities, Gross Amount Offset	0	0
Financial liabilities, Net Amount Presented	1.8	3.6
Financial liabilities, Financial Instruments	(0.3)	(0.7)
Financial liabilities, Collateral	$ (1.5)	$ (2.9)

Segment Information - Additiona

Segment Information - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2016USD ($)Segment	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)
Segment Reporting [Abstract]
Number of primary operating segments | Segment	3
Number of operating reportable segments | Segment	2
Other non-interest expense | $	$ 4.7	$ 12.9	$ 9.5
Other non-interest income | $	$ 7.5	$ 9.2	$ 20.6

Segment Information - Selected

Segment Information - Selected Financial Information Business Segments (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Net interest income (loss)	$ 246.8	$ 245.3	$ 240	$ 240.1	$ 238.8	$ 234.8	$ 230.4	$ 228.1	$ 972.2	$ 932.1	$ 911.9
Provision for loan losses	7.7	8.4	10	10.5	9.7	6.2	7.7	9.8	36.6	33.4	40.6
Total non-interest income	84.2	90.8	85.4	82.3	93.3	87.1	83	89	342.7	352.4	350.8
Total non-interest expense	217.2	221.4	212.9	217.3	217	214.2	211.8	217.6	868.8	860.6	841.5
Income (loss) before income tax expense (benefit)									409.5	390.5	380.6
Income tax expense (benefit)	30.2	32.6	34	31.7	34.6	33.1	32.2	30.5	128.5	130.4	128.9
Net income	$ 75.9	$ 73.7	$ 68.5	$ 62.9	$ 70.8	$ 68.4	$ 61.7	$ 59.2	281	260.1	251.7
Average total assets									39,784.3	36,926.9	33,767.1
Average total liabilities									34,924.9	32,229.6	29,141.7
Operating Segments [Member]
Segment Reporting Information [Line Items]
Net interest income (loss)									914	896.2	924
Provision for loan losses									52.3	62.9	64.4
Total non-interest income									325.4	331.7	308.8
Total non-interest expense									831.7	833.4	803.7
Income (loss) before income tax expense (benefit)									355.4	331.6	364.7
Income tax expense (benefit)									111.7	110.9	123.4
Net income									243.7	220.7	241.3
Average total assets									31,636.9	29,943.8	27,853.3
Average total liabilities									25,941	24,719	23,384.3
Operating Segments [Member] | Commercial Banking Loan [Member]
Segment Reporting Information [Line Items]
Net interest income (loss)									566.5	551.6	516
Provision for loan losses									39.3	47.7	47.6
Total non-interest income									156.4	162	141.4
Total non-interest expense									322.8	313.2	275.7
Income (loss) before income tax expense (benefit)									360.8	352.7	334.1
Income tax expense (benefit)									113.4	117.9	113.1
Net income									247.4	234.8	221
Average total assets									22,691.1	21,465.7	19,338.5
Average total liabilities									6,733.7	5,483.2	4,275.1
Operating Segments [Member] | Retail Banking [Member]
Segment Reporting Information [Line Items]
Net interest income (loss)									347.5	344.6	408
Provision for loan losses									13	15.2	16.8
Total non-interest income									169	169.7	167.4
Total non-interest expense									508.9	520.2	528
Income (loss) before income tax expense (benefit)									(5.4)	(21.1)	30.6
Income tax expense (benefit)									(1.7)	(7)	10.3
Net income									(3.7)	(14.1)	20.3
Average total assets									8,945.8	8,478.1	8,514.8
Average total liabilities									19,207.3	19,235.8	19,109.2
Treasury [Member]
Segment Reporting Information [Line Items]
Net interest income (loss)									87.6	64.4	10.7
Total non-interest income									9.2	11.1	12.4
Total non-interest expense									9.8	6.9	6.2
Income (loss) before income tax expense (benefit)									87	68.6	16.9
Income tax expense (benefit)									27.5	22.9	5.8
Net income									59.5	45.7	11.1
Average total assets									7,443.1	6,399.3	5,261.2
Average total liabilities									8,628.7	7,188.4	5,418
Other [Member]
Segment Reporting Information [Line Items]
Net interest income (loss)									(29.4)	(28.5)	(22.8)
Provision for loan losses									(15.7)	(29.5)	(23.8)
Total non-interest income									8.1	9.6	29.6
Total non-interest expense									27.3	20.3	31.6
Income (loss) before income tax expense (benefit)									(32.9)	(9.7)	(1)
Income tax expense (benefit)									(10.7)	(3.4)	(0.3)
Net income									(22.2)	(6.3)	(0.7)
Average total assets									704.3	583.8	652.6
Average total liabilities									$ 355.2	$ 322.2	$ 339.4

Parent Company Financial Inf149

Parent Company Financial Information - Condensed Statements of Condition (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Assets:
Cash at bank subsidiary	$ 432.4	$ 334.8
Total cash and cash equivalents	614.1	715.3	$ 1,013.7	$ 474.4
Securities available for sale, at fair value	4,409.9	4,527.7
Goodwill	1,992.7	1,958.7	1,954.5
Other assets	967.2	855.5
Total assets	40,609.8	38,946.7
Liabilities and Stockholders' Equity:
Notes and debentures	1,030.1	1,033.1
Other liabilities	520.2	457.3
Stockholders' equity	5,141.9	4,731.6	4,633.1	4,568.4
Total liabilities and stockholders' equity	40,609.8	38,946.7
People's United Financial, Inc. [Member]
Assets:
Cash at bank subsidiary	308.7	170.2
Total cash and cash equivalents	308.7	170.2	$ 4.3	$ 21.9
Securities available for sale, at fair value	75.3	201.4
Advances to bank subsidiary		100
Goodwill	197.1	197.1
Due from bank subsidiary	36.5	8.1
Other assets	29.9	28.4
Total assets	5,767.6	5,355.2
Liabilities and Stockholders' Equity:
Notes and debentures	621.5	619.7
Other liabilities	4.2	3.9
Stockholders' equity	5,141.9	4,731.6
Total liabilities and stockholders' equity	5,767.6	5,355.2
People's United Financial, Inc. [Member] | Bank Subsidiary [Member]
Assets:
Bank subsidiary	5,119.2	4,649.2
People's United Financial, Inc. [Member] | Non Bank Subsidiary [Member]
Assets:
Bank subsidiary	$ 0.9	$ 0.8

Parent Company Financial Inf150

Parent Company Financial Information - Condensed Statements of Income (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues:
Securities									$ 140.3	$ 121.5	$ 96.8
Advances to bank subsidiary									984.4	945.6	932.6
Total interest and dividend income	$ 286.3	$ 284.5	$ 278.5	$ 278	$ 274.2	$ 269.9	$ 264.5	$ 260.3	1,127.3	1,068.9	1,030.6
Dividend from bank subsidiary									271	245	244
Security gain									(5.9)		3
Other non-interest income									53.1	40.6	32.6
Expenses:
Interest on notes and debentures									31.4	29.8	26.7
Non-interest expense	217.2	221.4	212.9	217.3	217	214.2	211.8	217.6	868.8	860.6	841.5
Income before income tax benefit and subsidiaries undistributed income									409.5	390.5	380.6
Income tax benefit	30.2	32.6	34	31.7	34.6	33.1	32.2	30.5	128.5	130.4	128.9
Net income	$ 75.9	$ 73.7	$ 68.5	$ 62.9	$ 70.8	$ 68.4	$ 61.7	$ 59.2	281	260.1	251.7
People's United Financial, Inc. [Member]
Revenues:
Securities									3.4	1.1	0.4
Advances to bank subsidiary									1	4.4	4.4
Total interest and dividend income									4.4	5.5	4.8
Dividend from bank subsidiary									271	245	244
Security gain											2.3
Other non-interest income									14.8	4.2	1.2
Total revenues									290.2	254.7	252.3
Expenses:
Interest on notes and debentures									22.5	22.5	22.4
Non-interest expense									9.6	2.8	6.1
Total expenses									32.1	25.3	28.5
Income before income tax benefit and subsidiaries undistributed income									258.1	229.4	223.8
Income tax benefit									(5)	(5.5)	(6.6)
Income before subsidiaries undistributed income									263.1	234.9	230.4
Subsidiaries undistributed income									17.9	25.2	21.3
Net income									$ 281	$ 260.1	$ 251.7

Parent Company Financial Inf151

Parent Company Financial Information - Condensed Statements of Comprehensive Income (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Condensed Financial Statements, Captions [Line Items]
Net income	$ 75.9	$ 73.7	$ 68.5	$ 62.9	$ 70.8	$ 68.4	$ 61.7	$ 59.2	$ 281	$ 260.1	$ 251.7
Other comprehensive (loss), net of tax:
Net unrealized losses on securities available for sale									(14.6)	(14)	42.8
Net unrealized gains on derivatives accounted for as cash flow hedges									0.3	0.1	0.2
Current period other comprehensive income (loss)									(17.8)	(9)	(13.1)
Total comprehensive income									263.2	251.1	238.6
People's United Financial, Inc. [Member]
Condensed Financial Statements, Captions [Line Items]
Net income									281	260.1	251.7
Other comprehensive (loss), net of tax:
Net unrealized losses on securities available for sale									(0.1)	(0.3)
Net unrealized gains on derivatives accounted for as cash flow hedges									0.3	0.1	0.2
Other comprehensive loss of bank subsidiary									(18)	(8.8)	(13.3)
Current period other comprehensive income (loss)									(17.8)	(9)	(13.1)
Total comprehensive income									$ 263.2	$ 251.1	$ 238.6

Parent Company Financial Inf152

Parent Company Financial Information - Condensed Statements of Cash Flows (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash Flows from Operating Activities:
Net income	$ 75.9	$ 73.7	$ 68.5	$ 62.9	$ 70.8	$ 68.4	$ 61.7	$ 59.2	$ 281	$ 260.1	$ 251.7
Security gain									5.9		(3)
Net change in other assets and other liabilities									(104.2)	(92.5)	(37.2)
Net cash provided by operating activities									335.6	328.3	350
Cash Flows from Investing Activities:
Proceeds from principal repayments and maturities of securities available for sale									925	821.4	686.7
Proceeds from sales of securities available for sale									647.2	305.9	539.2
Purchases of securities available for sale									(1,486)	(1,766.4)	(879.8)
Net cash used in investing activities									(1,753.4)	(3,347.2)	(2,210.3)
Cash Flows from Financing Activities:
Proceeds from issuance of preferred stock, net									244.1
Cash dividends paid on common stock									(205.7)	(201.2)	(196.9)
Cash dividend paid on preferred stock									(1.8)
Common stock repurchases									(3.4)	(3.2)	(3)
Proceeds from stock options exercised, including excess income tax benefits									87.9	27.5	6
Net cash provided by financing activities									1,316.6	2,720.5	2,399.6
Net increase (decrease) in cash and cash equivalents									(101.2)	(298.4)	539.3
Cash and cash equivalents at beginning of year				715.3				1,013.7	715.3	1,013.7	474.4
Cash and cash equivalents at end of year	614.1				715.3				614.1	715.3	1,013.7
People's United Financial, Inc. [Member]
Cash Flows from Operating Activities:
Net income									281	260.1	251.7
Subsidiaries undistributed income									(17.9)	(25.2)	(21.3)
Security gain											(2.3)
Net change in other assets and other liabilities									(21.5)	(0.4)	0.2
Net cash provided by operating activities									241.6	234.5	228.3
Cash Flows from Investing Activities:
Proceeds from principal repayments and maturities of securities available for sale									1.4	1.2
Proceeds from sales of securities available for sale									200.4		5
Purchases of securities available for sale									(76)	(202.9)
Increase in investment in bank subsidiary									(450)
Decrease (increase) in advances to bank subsidiary									100	310	(57)
Net cash used in investing activities									(224.2)	108.3	(52)
Cash Flows from Financing Activities:
Proceeds from issuance of preferred stock, net									244.1
Cash dividends paid on common stock									(205.7)	(201.2)	(196.9)
Cash dividend paid on preferred stock									(1.8)
Common stock repurchases									(3.4)	(3.2)	(3)
Proceeds from stock options exercised, including excess income tax benefits									87.9	27.5	6
Net cash provided by financing activities									121.1	(176.9)	(193.9)
Net increase (decrease) in cash and cash equivalents									138.5	165.9	(17.6)
Cash and cash equivalents at beginning of year				$ 170.2				$ 4.3	170.2	4.3	21.9
Cash and cash equivalents at end of year	$ 308.7				$ 170.2				$ 308.7	$ 170.2	$ 4.3

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) $ in Millions	Feb. 14, 2017USD ($)	Sep. 30, 2016USD ($)Branches	Dec. 31, 2016USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2015USD ($)
Subsequent Event [Line Items]
Total assets			$ 40,609.8		$ 38,946.7
Total deposits			$ 29,860.8		28,417.4
Repayment of subordinated notes				$ 19
Subordinated borrowing interest rate			5.80%
People's United Financial, Inc. [Member]
Subsequent Event [Line Items]
Total assets			$ 5,767.6		$ 5,355.2
5.80% Fixed Rate/Floating Rate Subordinated Notes Due 2017 [Member] | People's United Financial, Inc. [Member]
Subsequent Event [Line Items]
Subordinated borrowing interest rate			5.80%
Subsequent Event [Member] | 5.80% Fixed Rate/Floating Rate Subordinated Notes Due 2017 [Member] | People's United Financial, Inc. [Member]
Subsequent Event [Line Items]
Repayment of subordinated notes	$ 125
Subordinated borrowing interest rate	5.80%
Suffolk Bancorp [Member]
Subsequent Event [Line Items]
Total assets		$ 2,200
Business acquisition, date of acquisition agreement			Jun. 27, 2016
Total deposits		$ 1,900
Number of branches to be acquired | Branches		27
Stock conversion ratio			2.225%
Total transaction value			$ 518
Merger-related expenses			$ 2.8

Selected Quarterly Financial154

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, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Quarterly Financial Information [Line Items]
Interest and dividend income	$ 286.3	$ 284.5	$ 278.5	$ 278	$ 274.2	$ 269.9	$ 264.5	$ 260.3	$ 1,127.3	$ 1,068.9	$ 1,030.6
Interest expense	39.5	39.2	38.5	37.9	35.4	35.1	34.1	32.2	155.1	136.8	118.7
Net interest income	246.8	245.3	240	240.1	238.8	234.8	230.4	228.1	972.2	932.1	911.9
Provision for loan losses	7.7	8.4	10	10.5	9.7	6.2	7.7	9.8	36.6	33.4	40.6
Net interest income after provision for loan losses	239.1	236.9	230	229.6	229.1	228.6	222.7	218.3	935.6	898.7	871.3
Non-interest income	84.2	90.8	85.4	82.3	93.3	87.1	83	89	342.7	352.4	350.8
Non-interest expense	217.2	221.4	212.9	217.3	217	214.2	211.8	217.6	868.8	860.6	841.5
Income before income tax expense	106.1	106.3	102.5	94.6	105.4	101.5	93.9	89.7	409.5	390.5	380.6
Income tax expense	30.2	32.6	34	31.7	34.6	33.1	32.2	30.5	128.5	130.4	128.9
Net income	75.9	73.7	68.5	62.9	70.8	68.4	61.7	59.2	281	260.1	251.7
Preferred stock dividend	1.8								1.8
Net income available to common shareholders	$ 74.1	$ 73.7	$ 68.5	$ 62.9	$ 70.8	$ 68.4	$ 61.7	$ 59.2	$ 279.2	$ 260.1	$ 251.7
Basic EPS	$ 0.24	$ 0.24	$ 0.23	$ 0.21	$ 0.23	$ 0.23	$ 0.20	$ 0.20	$ 0.92	$ 0.86	$ 0.84
Diluted EPS	$ 0.24	$ 0.24	$ 0.23	$ 0.21	$ 0.23	$ 0.23	$ 0.20	$ 0.20	$ 0.92	$ 0.86	$ 0.84
Common dividends paid	$ 51.7	$ 51.7	$ 51.7	$ 50.6	$ 50.6	$ 50.6	$ 50.5	$ 49.5	$ 205.7	$ 201.2	$ 196.9
Dividends paid per common share	$ 0.1700	$ 0.1700	$ 0.1700	$ 0.1675	$ 0.1675	$ 0.1675	$ 0.1675	$ 0.1650	$ 0.1700	$ 0.1675
Common dividend payout ratio	69.80%	70.10%	75.40%	80.60%	71.50%	73.90%	81.80%	83.70%	73.70%	77.30%	78.20%
Basic	305,170	302,880	302,480	301,860	301,380	301,000	300,090	299,150	303,100	300,400	298,200
Diluted	306,230	303,240	302,480	301,860	301,380	301,000	300,090	299,150	304,000	300,400	298,300
Maximum [Member]
Quarterly Financial Information [Line Items]
Stock price	$ 20.13	$ 16.40	$ 16.68	$ 16.27	$ 16.93	$ 16.95	$ 16.64	$ 15.45	$ 20.13	$ 16.93
Minimum [Member]
Quarterly Financial Information [Line Items]
Stock price	$ 15.28	$ 14.22	$ 13.80	$ 13.62	$ 15	$ 14.69	$ 14.92	$ 13.97	$ 15.28	$ 15