People's United Financial (PBCT) 10-Q 10 May 17 2017 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2017	Apr. 30, 2017
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q1
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 Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		344,346,175

Consolidated Statements of Cond

Consolidated Statements of Condition - (Unaudited) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Assets
Cash and due from banks	$ 380.8	$ 432.4
Short-term investments (note 2)	392.2	181.7
Total cash and cash equivalents	773	614.1
Securities (note 2):
Trading account securities, at fair value	7.8	6.8
Securities available for sale, at fair value	3,772.1	4,409.9
Securities held to maturity, at amortized cost (fair value of $2.34 billion and $2.01 billion)	2,324	2,005.4
Federal Home Loan Bank and Federal Reserve Bank stock, at cost	319.6	315.8
Total securities	6,423.5	6,737.9
Loans held for sale	17.1	39.3
Loans (note 3):
Total loans	29,687.3	29,744.9
Less allowance for loan losses	(231.3)	(229.3)
Total loans, net	29,456	29,515.6
Goodwill (note 6)	1,992.7	1,992.7
Bank-owned life insurance	348.8	349.1
Premises and equipment, net	239.4	244.5
Other acquisition-related intangible assets (note 6)	143.1	149.4
Other assets (notes 1, 3 and 11)	836	967.2
Total assets	40,229.6	40,609.8
Deposits:
Non-interest-bearing	6,669.5	6,660.8
Savings	4,451.7	4,397.7
Interest-bearing checking and money market	14,813.9	14,260.1
Time	4,570.6	4,542.2
Total deposits	30,505.7	29,860.8
Borrowings:
Federal Home Loan Bank advances	2,160.4	3,061.1
Federal funds purchased	613	617
Customer repurchase agreements	327.7	343.3
Other borrowings	81.9	35.4
Total borrowings	3,183	4,056.8
Notes and debentures	903.9	1,030.1
Other liabilities (notes 1 and 11)	442	520.2
Total liabilities	35,034.6	35,467.9
Commitments and contingencies (notes 1 and 8)
Stockholders' Equity
Preferred stock ($0.01 par value; 50.0 million shares authorized; 10.0 million shares issued and outstanding at both dates)	244.1	244.1
Common stock ($0.01 par value; 1.95 billion shares authorized; 406.4 million shares and 405.0 million shares issued)	4.1	4
Additional paid-in capital	5,472.7	5,446.1
Retained earnings	960.9	949.3
Unallocated common stock of Employee Stock Ownership Plan, at cost (6.9 million shares and 7.0 million shares) (note 7)	(142.8)	(144.6)
Accumulated other comprehensive loss (note 4)	(181.9)	(195)
Treasury stock, at cost (89.0 million shares and 89.1 million shares) (note 4)	(1,162.1)	(1,162)
Total stockholders' equity	5,195	5,141.9
Total liabilities and stockholders' equity	40,229.6	40,609.8
Commercial [Member]
Loans (note 3):
Total loans	21,113.1	21,404.9
Less allowance for loan losses	(201.2)	(204.9)
Retail Loans [Member]
Loans (note 3):
Total loans	8,574.2	8,340
Less allowance for loan losses	(30.1)	(24.4)
Commercial Real Estate Loan [Member] | Commercial [Member]
Loans (note 3):
Total loans	10,225.3	10,247.3
Commercial and Industrial [Member] | Commercial [Member]
Loans (note 3):
Total loans	7,918.3	8,125.1
Equipment Financing [Member] | Commercial [Member]
Loans (note 3):
Total loans	2,969.5	3,032.5
Residential Mortgage Loan [Member] | Retail Loans [Member]
Loans (note 3):
Total loans	6,487.7	6,216.7
Home Equity and Other Consumer [Member] | Retail Loans [Member]
Loans (note 3):
Total loans	$ 2,086.5	$ 2,123.3

Consolidated Statements of Con3

Consolidated Statements of Condition - (Unaudited) (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Securities held to maturity, at fair value	$ 2,339.5	$ 2,012.6
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	50,000,000	50,000,000
Preferred stock, shares issued	10,000,000	10,000,000
Preferred stock, shares outstanding	10,000,000	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	406,400,000	405,000,000
Unallocated common stock of Employee Stock Ownership Plan, shares	6,881,936	7,000,000
Treasury stock, shares	89,000,000	89,100,000

Consolidated Statements of Inco

Consolidated Statements of Income - (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Interest and dividend income:
Commercial real estate	$ 88.6	$ 86.8
Residential mortgage	49.3	43.9
Home equity and other consumer	18.4	18.6
Total interest on loans	252.5	242.9
Securities	37	34.5
Loans held for sale	0.3	0.2
Short-term investments	0.7	0.4
Total interest and dividend income	290.5	278
Interest expense:
Deposits	27.1	25.2
Borrowings	7.3	5
Notes and debentures	7.5	7.7
Total interest expense	41.9	37.9
Net interest income	248.6	240.1
Provision for loan losses (note 3)	4.4	10.5
Net interest income after provision for loan losses	244.2	229.6
Non-interest income:
Bank service charges	23.5	23.8
Investment management fees	16	11.1
Operating lease income	10.2	10.4
Insurance revenue	9.1	9.3
Commercial banking lending fees	8.2	8.1
Cash management fees	6.3	6
Brokerage commissions	3	3
Net gains on sales of residential mortgage loans	0.9	0.9
Net security (losses) gains (note 2)	(15.7)	0.1
Other non-interest income	23.2	9.6
Total non-interest income	84.7	82.3
Non-interest expense (note 14):
Compensation and benefits	125.6	114.1
Occupancy and equipment	38.6	37.5
Professional and outside services	15.5	17.4
Regulatory assessments	9.6	8
Operating lease expense	8.8	9.2
Amortization of other acquisition-related intangible assets (note 6)	6.3	5.8
Other non-interest expense	21.7	25.3
Total non-interest expense	226.1	217.3
Income before income tax expense	102.8	94.6
Income tax expense (notes 1 and 13)	32	31.7
Net income	70.8	62.9
Preferred stock dividend	3.5
Net income available to common shareholders	$ 67.3	$ 62.9
Earnings per common share (note 5):
Basic	$ 0.22	$ 0.21
Diluted	$ 0.22	$ 0.21
Commercial and Industrial [Member]
Interest and dividend income:
Interest and fee income	$ 64.6	$ 60.3
Equipment Financing [Member]
Interest and dividend income:
Interest and fee income	$ 31.6	$ 33.3

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 70.8	$ 62.9
Other comprehensive income, net of tax:
Net actuarial loss and prior service credit related to pension and other postretirement plans	0.9	1
Net unrealized gains and losses on securities available for sale	11.3	41
Amortization of unrealized losses on securities transferred to held to maturity	0.5	0.5
Net unrealized gains and losses on derivatives accounted for as cash flow hedges	0.4
Total other comprehensive income, net of tax (note 4)	13.1	42.5
Total comprehensive income	$ 83.9	$ 105.4

Consolidated Statements of Chan

Consolidated Statements of Changes in Stockholders' Equity - (Unaudited) - 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, 2015	$ 4,731.6		$ 3.9	$ 5,337.7	$ 880.8	$ (151.8)	$ (177.2)	$ (1,161.8)
Net income	62.9				62.9
Total other comprehensive income, net of tax (note 4)	42.5						42.5
Cash dividends on common stock	(50.7)				(50.7)
Restricted stock and performance-based share awards	2			2.1				(0.1)
Employee Stock Ownership Plan common stock committed to be released (note 7)	1.3				(0.5)	1.8
Common stock repurchased and retired upon vesting of restricted stock awards	(2.9)				(2.9)
Stock option exercises and related tax benefits	4.5			4.5
Ending Balance at Mar. 31, 2016	4,791.2		3.9	5,344.3	889.6	(150)	(134.7)	(1,161.9)
Beginning Balance at Dec. 31, 2016	5,141.9	$ 244.1	4	5,446.1	949.3	(144.6)	(195)	(1,162)
Net income	70.8				70.8
Total other comprehensive income, net of tax (note 4)	13.1						13.1
Cash dividends on common stock	(52.7)				(52.7)
Cash dividend on preferred stock	(3.5)				(3.5)
Restricted stock and performance-based share awards	3.3			3.4				(0.1)
Employee Stock Ownership Plan common stock committed to be released (note 7)	1.7				(0.1)	1.8
Common stock repurchased and retired upon vesting of restricted stock awards	(2.9)				(2.9)
Stock option exercises and related tax benefits	23.3		0.1	23.2
Ending Balance at Mar. 31, 2017	$ 5,195	$ 244.1	$ 4.1	$ 5,472.7	$ 960.9	$ (142.8)	$ (181.9)	$ (1,162.1)

Consolidated Statements of Cha7

Consolidated Statements of Changes in Stockholders' Equity - (Unaudited) (Parenthetical) - $ / shares	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Cash dividends on common stock, per share	$ 0.17	$ 0.1675
Retained Earnings [Member]
Cash dividends on common stock, per share	$ 0.17	$ 0.1675

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Cash Flows from Operating Activities:
Net income	$ 70.8	$ 62.9
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Depreciation and amortization of premises and equipment	9.3	9.2
Expense related to operating leases	8.8	9.2
Amortization of other acquisition-related intangible assets	6.3	5.8
Expense related to share-based awards	5.4	3.6
Provision for loan losses	4.4	10.5
Employee Stock Ownership Plan common stock committed to be released	1.7	1.3
Net security losses (gains)	15.7	(0.1)
Net gains on sales of residential mortgage loans	(0.9)	(0.9)
Originations of loans held-for-sale	(75.1)	(67.4)
Proceeds from sales of loans held-for-sale	98.2	71.3
Net increase in trading account securities	(1)
Excess income tax benefits from stock option exercises (note 13)	1
Net changes in other assets and other liabilities	32	10.6
Net cash provided by operating activities	176.6	116
Cash Flows from Investing Activities:
Proceeds from principal repayments and maturities of securities available for sale	177.9	178.1
Proceeds from sales of securities available for sale	472.3	138.9
Proceeds from principal repayments and maturities of securities held to maturity	24.9	22
Purchases of securities available for sale	(1)	(471)
Purchases of securities held to maturity	(345)	(90)
Net (purchases) redemptions of Federal Reserve Bank stock	(4.1)	0.6
Net redemptions of Federal Home Loan Bank stock	0.3	4.9
Proceeds from sales of loans	7
Loan disbursements, net of principal collections	48.6	(105.1)
Purchases of premises and equipment	(4.2)	(3.5)
Purchases of leased equipment	(4.4)
Proceeds from sales of real estate owned	0.5	1.8
Return of premium on bank-owned life insurance, net	0.7
Net cash provided by (used in) investing activities	373.5	(323.3)
Cash Flows from Financing Activities:
Net increase in deposits	644.9	688.1
Net decrease in borrowings with terms of three months or less	(873.1)	(589.3)
Repayments of borrowings with terms of more than three months	(0.1)	(0.1)
Repayment of notes and debentures	(125)
Cash dividends paid on common stock	(52.7)	(50.6)
Cash dividend paid on preferred stock	(3.5)
Common stock repurchases	(2.9)	(2.9)
Proceeds from stock options exercised	21.2	0.5
Net cash (used in) provided by financing activities	(391.2)	45.7
Net increase (decrease) in cash and cash equivalents	158.9	(161.6)
Cash and cash equivalents at beginning of period	614.1	715.3
Cash and cash equivalents at end of period	773	553.7
Supplemental Information:
Interest payments	40.7	37.4
Real estate properties acquired by foreclosure	4.1	3.8
Unsettled purchases of securities	3.4	6.3
Income tax payments	$ 5.8	$ 2.4

General

General	3 Months Ended
	Mar. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
General	NOTE 1. GENERAL In the opinion of management, the accompanying unaudited consolidated financial statements of People’s United Financial, Inc. (“People’s United” or the “Company”) have been prepared to reflect all adjustments necessary to present fairly the financial position and results of operations as of the dates and for the periods shown. All significant intercompany transactions and balances are eliminated in consolidation. Certain reclassifications have been made to prior period amounts to conform to the current period 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 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. Note 1 to People’s United’s audited consolidated financial statements included in the Annual Report on Form 10-K 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 (“VIEs”), are not consolidated into the Company’s Consolidated Financial Statements. These investments have historically played a role in enabling People’s United Bank, National Association (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 ($220.3 million and $195.2 million at March 31, 2017 and December 31, 2016, respectively). Included in other liabilities in the Consolidated Statements of Condition is a liability for all legally binding unfunded commitments to fund future investments ($99.9 million and $92.5 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 $4.0 million and $3.0 million for the three months ended March 31, 2017 and 2016, respectively. Certain information and footnote disclosures normally included in consolidated financial statements prepared in conformity with U.S. generally accepted accounting principles (“GAAP”) have been omitted or condensed. As a result, the accompanying consolidated financial statements should be read in conjunction with People’s United’s Annual Report on Form 10-K

Securities and Short-Term Inves

Securities and Short-Term Investments	3 Months Ended
	Mar. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Securities and Short-Term Investments	NOTE 2. SECURITIES AND SHORT-TERM INVESTMENTS 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 March 31, 2017 (in millions) Amortized Gross Gross Fair Securities available for sale: Debt securities: U.S. Treasury and agency $ 822.7 $ 0.3 $ (24.3 ) $ 798.7 GSE (1) mortgage-backed securities and CMOs (2) 2,976.5 13.5 (25.5 ) 2,964.5 Total debt securities 3,799.2 13.8 (49.8 ) 3,763.2 Equity securities (3) 9.6 — (0.7 ) 8.9 Total securities available for sale $ 3,808.8 $ 13.8 $ (50.5 ) $ 3,772.1 Securities held to maturity: Debt securities: State and municipal $ 1,663.0 $ 40.2 $ (21.7 ) $ 1,681.5 GSE mortgage-backed securities 648.8 0.2 (3.4 ) 645.6 Corporate 10.7 0.2 — 10.9 Other 1.5 — — 1.5 Total securities held to maturity $ 2,324.0 $ 40.6 $ (25.1 ) $ 2,339.5 (1) Government sponsored enterprise (2) Collateralized mortgage obligations (3) During the quarter ended March 31, 2017, the Company exchanged its ownership interest in a non-marketable equity security (previously recorded in other assets) for cash and common stock in a publicly-traded company (fair value of approximately $10.8 million at acquisition). As of December 31, 2016 (in millions) Amortized Gross Gross Fair 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 Corporate 4.0 — — 4.0 Other 1.5 — — 1.5 Total securities held to maturity $ 2,005.4 $ 33.9 $ (26.7 ) $ 2,012.6 Securities available for sale with a fair value of $1.91 billion and $1.83 billion at March 31, 2017 and December 31, 2016, respectively, were pledged as collateral for public deposits and for other purposes. The following table is a summary of the amortized cost and fair value of debt securities as of March 31, 2017, 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 (in millions) Amortized Fair Amortized Fair U.S. Treasury and agency: Within 1 year $ 1.0 $ 1.0 $ — $ — After 1 but within 5 years 238.7 235.7 — — After 5 but within 10 years 583.0 562.0 — — Total 822.7 798.7 — — GSE mortgage-backed securities and CMOs: After 5 but within 10 years 1,016.3 1,028.3 166.6 166.6 After 10 years 1,960.2 1,936.2 482.2 479.0 Total 2,976.5 2,964.5 648.8 645.6 State and municipal: Within 1 year — — 4.2 4.2 After 1 but within 5 years — — 30.7 31.3 After 5 but within 10 years — — 363.1 381.5 After 10 years — — 1,265.0 1,264.5 Total — — 1,663.0 1,681.5 Corporate: After 5 but within 10 years — — 5.7 5.8 After 10 years — — 5.0 5.1 Total — — 10.7 10.9 Other: Within 1 year — — 1.5 1.5 Total — — 1.5 1.5 Total: Within 1 year 1.0 1.0 5.7 5.7 After 1 but within 5 years 238.7 235.7 30.7 31.3 After 5 but within 10 years 1,599.3 1,590.3 535.4 553.9 After 10 years 1,960.2 1,936.2 1,752.2 1,748.6 Total $ 3,799.2 $ 3,763.2 $ 2,324.0 $ 2,339.5 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 The following tables summarize those securities with unrealized losses, segregated by the length of time the securities have been in a continuous unrealized loss position at the respective dates. Certain unrealized losses totaled less than $0.1 million. Continuous Unrealized Loss Position Less Than 12 Months 12 Months Or Longer Total As of March 31, 2017 (in millions) Fair Unrealized Fair Unrealized Fair Unrealized Securities available for sale: GSE mortgage-backed securities and CMOs $ 2,315.0 $ (23.2 ) $ 62.0 $ (2.3 ) $ 2,377.0 $ (25.5 ) U.S. Treasury and agency 768.4 (24.3 ) — — 768.4 (24.3 ) Equity securities 8.9 (0.7 ) — — 8.9 (0.7 ) Securities held to maturity: GSE mortgage-backed securities 553.1 (3.4 ) — — 553.1 (3.4 ) State and municipal 600.3 (21.7 ) 0.1 — 600.4 (21.7 ) Total $ 4,245.7 $ (73.3 ) $ 62.1 $ (2.3 ) $ 4,307.8 $ (75.6 ) Continuous Unrealized Loss Position Less Than 12 Months 12 Months Or Longer Total As of December 31, 2016 (in millions) Fair Unrealized Fair Unrealized Fair Unrealized 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 ) At March 31, 2017, approximately 33% of the 1,753 securities owned by the Company, consisting of 123 securities classified as available for sale and 464 securities classified as held to maturity, had gross unrealized losses totaling $50.5 million and $25.1 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 15 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 March 31, 2017 are temporary impairments. No other-than-temporary impairment losses were recognized in the Consolidated Statements of Income for the three months ended March 31, 2017 or 2016. Security transactions are recorded on the trade date. Realized gains and losses are determined using the specific identification method and reported in non-interest The Bank, as a member of the Federal Home Loan Bank (the “FHLB”) of Boston, is currently required to purchase and hold shares of capital stock in the FHLB of Boston (total cost of $154.7 million and $155.0 million at March 31, 2017 and December 31, 2016, 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 March 31, 2017 and December 31, 2016). 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 March 31, 2017 and the cost of the investment approximates fair value. The Bank, as a member of the Federal Reserve Bank system, is currently required to purchase and hold shares of capital stock in the Federal Reserve Bank of New York (the “FRB-NY”) FRB-NY, Included in short-term investments are interest-bearing deposits at the FRB-NY

Loans

Loans	3 Months Ended
	Mar. 31, 2017
Receivables [Abstract]
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’). 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. People’s United maintains several significant accounting policies with respect to loans, including: • Establishment of the allowance for loan losses (including the identification of ‘impaired’ loans and related impairment measurement considerations); • Income recognition (including the classification of a loan as ‘non-accrual’ • Recognition of loan charge-offs. The Company did not change its policies with respect to loans or its methodology for determining the allowance for loan losses during the three months ended March 31, 2017. The following table summarizes People’s United’s loans by loan portfolio segment and class: March 31, 2017 December 31, 2016 (in millions) Originated Acquired Total Originated Acquired Total Commercial: Commercial real estate $ 10,001.2 $ 224.1 $ 10,225.3 $ 10,012.6 $ 234.7 $ 10,247.3 Commercial and industrial 7,737.9 180.4 7,918.3 7,939.0 186.1 8,125.1 Equipment financing 2,963.0 6.5 2,969.5 3,020.9 11.6 3,032.5 Total Commercial Portfolio 20,702.1 411.0 21,113.1 20,972.5 432.4 21,404.9 Retail: Residential mortgage: Adjustable-rate 5,699.1 91.1 5,790.2 5,453.8 95.3 5,549.1 Fixed-rate 647.1 50.4 697.5 613.5 54.1 667.6 Total residential mortgage 6,346.2 141.5 6,487.7 6,067.3 149.4 6,216.7 Home equity and other consumer: Home equity 2,012.0 25.3 2,037.3 2,044.9 27.7 2,072.6 Other consumer 48.5 0.7 49.2 50.0 0.7 50.7 Total home equity and other consumer 2,060.5 26.0 2,086.5 2,094.9 28.4 2,123.3 Total Retail Portfolio 8,406.7 167.5 8,574.2 8,162.2 177.8 8,340.0 Total loans $ 29,108.8 $ 578.5 $ 29,687.3 $ 29,134.7 $ 610.2 $ 29,744.9 Net deferred loan costs, which are included in loans by respective class and accounted for as interest yield adjustments, totaled $72.3 million at March 31, 2017 and $69.9 million at December 31, 2016. The following table presents a summary, by loan portfolio segment, of activity in the allowance for loan losses for the three months ended March 31, 2017 and 2016. 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. Three months ended Commercial Retail March 31, 2017 (in millions) Originated Acquired Total Originated Acquired Total Total Balance at beginning of period $ 198.8 $ 6.1 $ 204.9 $ 24.2 $ 0.2 $ 24.4 $ 229.3 Charge-offs (2.9 ) — (2.9 ) (1.7 ) — (1.7 ) (4.6 ) Recoveries 1.6 — 1.6 0.6 — 0.6 2.2 Net loan charge-offs (1.3 ) — (1.3 ) (1.1 ) — (1.1 ) (2.4 ) Provision for loan losses (2.4 ) — (2.4 ) 6.8 — 6.8 4.4 Balance at end of period $ 195.1 $ 6.1 $ 201.2 $ 29.9 $ 0.2 $ 30.1 $ 231.3 Three months ended Commercial Retail March 31, 2016 (in millions) Originated Acquired Total Originated Acquired Total Total Balance at beginning of period $ 181.8 $ 7.9 $ 189.7 $ 21.1 $ 0.2 $ 21.3 $ 211.0 Charge-offs (4.6 ) (0.3 ) (4.9 ) (2.8 ) — (2.8 ) (7.7 ) Recoveries 0.4 — 0.4 1.3 — 1.3 1.7 Net loan charge-offs (4.2 ) (0.3 ) (4.5 ) (1.5 ) — (1.5 ) (6.0 ) Provision for loan losses 7.3 0.1 7.4 3.1 — 3.1 10.5 Balance at end of period $ 184.9 $ 7.7 $ 192.6 $ 22.7 $ 0.2 $ 22.9 $ 215.5 The following is a summary, by loan portfolio segment and impairment methodology, of the allowance for loan losses and related portfolio balances: As of March 31, 2017 Originated Loans Originated Loans Acquired Loans Total (in millions) Portfolio Allowance Portfolio Allowance Portfolio Allowance Portfolio Allowance Commercial $ 176.2 $ 8.1 $ 20,525.9 $ 187.0 $ 411.0 $ 6.1 $ 21,113.1 $ 201.2 Retail 94.1 3.2 8,312.6 26.7 167.5 0.2 8,574.2 30.1 Total $ 270.3 $ 11.3 $ 28,838.5 $ 213.7 $ 578.5 $ 6.3 $ 29,687.3 $ 231.3 As of December 31, 2016 Originated Loans Originated Loans Acquired Loans Total (in millions) 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 The recorded investments, by class of loan, of originated non-performing (in millions) March 31, December 31, Commercial: Commercial real estate $ 23.4 $ 22.3 Commercial and industrial 47.4 41.5 Equipment financing 47.4 39.4 Total (1) 118.2 103.2 Retail: Residential mortgage 26.3 27.4 Home equity 15.2 17.4 Other consumer — — Total (2) 41.5 44.8 Total $ 159.7 $ 148.0 (1) Reported net of government guarantees totaling $4.4 million and $13.1 million at March 31, 2017 and December 31, 2016, 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 March 31, 2017, the principal loan classes to which these government guarantees relate are commercial and industrial loans (99%) and commercial real estate loans (1%). (2) Includes $11.8 million and $9.8 million of loans in the process of foreclosure at March 31, 2017 and December 31, 2016, respectively. The preceding table excludes acquired loans that are (i) accounted for as purchased credit impaired loans or (ii) covered by a Federal Deposit Insurance Corporation (“FDIC”) loss-share agreement (“LSA”) totaling $19.4 million and $2.7 million, respectively, at March 31, 2017 and $21.6 million and $3.1 million, respectively, at December 31, 2016. Such loans otherwise meet People’s United’s definition of a non-performing A loan is generally considered “non-performing” non-accrual non-accrual non-accrual 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 People’s United’s recorded investment in originated loans classified as TDRs totaled $196.7 million and $189.9 million at March 31, 2017 and December 31, 2016, respectively. The related allowance for loan losses at March 31, 2017 and December 31, 2016 was $4.6 million and $4.2 million, respectively. Interest income recognized on TDRs totaled $1.3 million and $1.1 million for the three months ended March 31, 2017 and 2016, respectively. Fundings under commitments to lend additional amounts to borrowers with loans classified as TDRs were immaterial for the three months ended March 31, 2017 and 2016. Originated loans that were modified and classified as TDRs during the three months ended March 31, 2017 and 2016 principally involve reduced payment and/or payment deferral, extension of term (generally no more than two years for commercial loans and five years for retail loans) and/or a temporary reduction of interest rate (generally less than 200 basis points). The following tables summarize, by class of loan, the recorded investments in loans modified as TDRs during the three months ended March 31, 2017 and 2016. For purposes of this disclosure, recorded investments represent amounts immediately prior to and subsequent to the restructuring. Three Months Ended March 31, 2017 (dollars in millions) Number Pre-Modification Post-Modification Commercial: Commercial real estate (1) 3 $ 3.9 $ 3.9 Commercial and industrial (2) 9 8.3 8.3 Equipment financing (3) 21 5.9 5.9 Total 33 18.1 18.1 Retail: Residential mortgage (4) 7 3.8 3.8 Home equity (5) 24 2.2 2.2 Other consumer — — — Total 31 6.0 6.0 Total 64 $ 24.1 $ 24.1 (1) Represents the following concessions: reduced payment and/or payment deferral (2 contracts; recorded investment of $2.2 million); or temporary rate reduction (1 contract; recorded investment of $1.7 million). (2) Represents the following concessions: extension of term (8 contracts; recorded investment of $7.4 million); or reduced payment and/or payment deferral (1 contract; recorded investment of $0.9 million). (3) Represents the following concessions: reduced payment and/or payment deferral (7 contracts; recorded investment of $2.3 million); or a combination of concessions (14 contracts; recorded investment of $3.6 million). (4) Represents the following concessions: loans restructured through bankruptcy (1 contract; recorded investment of $0.1 million); reduced payment and/or payment deferral (4 contracts; recorded investment of $1.3 million); or a combination of concessions (2 contracts; recorded investment of $2.4 million). (5) Represents the following concessions: loans restructured through bankruptcy (14 contracts; recorded investment of $1.1 million); reduced payment and/or payment deferral (4 contracts; recorded investment of $0.3 million); or a combination of concessions (6 contracts; recorded investment of $0.8 million). Three Months Ended March 31, 2016 (dollars in millions) Number Pre-Modification Post-Modification Commercial: Commercial real estate (1) 3 $ 1.1 $ 1.1 Commercial and industrial (2) 13 5.2 5.2 Equipment financing (3) 10 6.1 6.1 Total 26 12.4 12.4 Retail: Residential mortgage (4) 19 5.3 5.3 Home equity (5) 19 1.6 1.6 Other consumer — — — Total 38 6.9 6.9 Total 64 $ 19.3 $ 19.3 (1) Represents the following concessions: extension of term (1 contract; recorded investment of $0.2 million); reduced payment and/or payment deferral (1 contract; recorded investment of $0.9 million); or a combination of concessions (1 contract; recorded investment of less than $0.1 million). (2) Represents the following concessions: extension of term (7 contracts; recorded investment of $4.4 million); reduced payment and/or payment deferral (3 contracts; recorded investment of $0.4 million); or a combination of concessions (3 contracts; recorded investment of $0.4 million). (3) Represents the following concessions: extension of term (2 contracts; recorded investment of $0.4 million); reduced payment and/or payment deferral (5 contracts; recorded investment of $4.3 million); or a combination of concessions (3 contracts; recorded investment of $1.4 million). (4) Represents the following concessions: loans restructured through bankruptcy (4 contracts; recorded investment of $1.5 million); reduced payment and/or payment deferral (5 contracts; recorded investment of $1.4 million); or a combination of concessions (10 contracts; recorded investment of $2.4 million). (5) Represents the following concessions: loans restructured through bankruptcy (14 contracts; recorded investment of $1.3 million); reduced payment and/or payment deferral (1 contract; recorded investment of $0.1 million); or a combination of concessions (4 contracts; recorded investment of $0.2 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 three months ended March 31, 2017 and 2016. For purposes of this disclosure, the previous 12 months is measured from April 1 of the respective prior year and a default represents a previously-modified loan that became past due 30 days or more during the three months ended March 31, 2017 or 2016. Three Months Ended March 31, 2017 2016 (dollars in millions) Number Recorded Number Recorded Commercial: Commercial real estate 1 $ 1.7 — $ — Commercial and industrial 2 1.4 2 0.6 Equipment financing 8 2.6 5 2.5 Total 11 5.7 7 3.1 Retail: Residential mortgage 7 2.5 6 1.3 Home equity 1 0.1 7 0.5 Other consumer — — — — Total 8 2.6 13 1.8 Total 19 $ 8.3 20 $ 4.9 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. As of March 31, 2017 As of December 31, 2016 (in millions) Unpaid Recorded Related Unpaid Recorded Related Without a related allowance for loan losses: Commercial: Commercial real estate $ 49.0 $ 47.4 $ — $ 41.4 $ 40.0 $ — Commercial and industrial 42.6 40.7 — 50.7 45.7 — Equipment financing 41.0 37.3 — 38.2 35.3 — Retail: Residential mortgage 66.6 60.7 — 63.6 58.0 — Home equity 22.2 18.5 — 22.4 18.7 — Other consumer — — — — — — Total $ 221.4 $ 204.6 $ — $ 216.3 $ 197.7 $ — With a related allowance for loan losses: Commercial: Commercial real estate $ 8.5 $ 8.3 $ 0.4 $ 12.2 $ 11.4 $ 0.6 Commercial and industrial 33.5 32.6 6.1 25.9 25.0 4.7 Equipment financing 10.9 9.9 1.6 5.0 4.4 0.5 Retail: Residential mortgage 12.5 12.5 2.2 13.1 13.1 2.3 Home equity 2.4 2.4 1.0 2.1 2.0 0.9 Other consumer — — — — — — Total $ 67.8 $ 65.7 $ 11.3 $ 58.3 $ 55.9 $ 9.0 Total impaired loans: Commercial: Commercial real estate $ 57.5 $ 55.7 $ 0.4 $ 53.6 $ 51.4 $ 0.6 Commercial and industrial 76.1 73.3 6.1 76.6 70.7 4.7 Equipment financing 51.9 47.2 1.6 43.2 39.7 0.5 Total 185.5 176.2 8.1 173.4 161.8 5.8 Retail: Residential mortgage 79.1 73.2 2.2 76.7 71.1 2.3 Home equity 24.6 20.9 1.0 24.5 20.7 0.9 Other consumer — — — — — — Total 103.7 94.1 3.2 101.2 91.8 3.2 Total $ 289.2 $ 270.3 $ 11.3 $ 274.6 $ 253.6 $ 9.0 The following tables summarize, 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 Three Months Ended March 31, 2017 2016 (in millions) Average Interest Average Interest Commercial: Commercial real estate $ 51.9 $ 0.4 $ 60.2 $ 0.3 Commercial and industrial 70.0 0.5 63.0 0.4 Equipment financing 39.8 0.1 33.1 0.1 Total 161.7 1.0 156.3 0.8 Retail: Residential mortgage 71.2 0.4 72.2 0.4 Home equity 20.4 0.1 22.4 0.1 Other consumer — — — — Total 91.6 0.5 94.6 0.5 Total $ 253.3 $ 1.5 $ 250.9 $ 1.3 The following tables summarize, by class of loan, aging information for originated loans: Past Due As of March 31, 2017 (in millions) Current 30-89 90 Days Total Total Commercial: Commercial real estate $ 9,979.5 $ 13.1 $ 8.6 $ 21.7 $ 10,001.2 Commercial and industrial 7,700.8 18.3 18.8 37.1 7,737.9 Equipment financing 2,880.7 70.0 12.3 82.3 2,963.0 Total 20,561.0 101.4 39.7 141.1 20,702.1 Retail: Residential mortgage 6,304.8 24.3 17.1 41.4 6,346.2 Home equity 1,999.5 5.6 6.9 12.5 2,012.0 Other consumer 48.3 0.2 — 0.2 48.5 Total 8,352.6 30.1 24.0 54.1 8,406.7 Total originated loans $ 28,913.6 $ 131.5 $ 63.7 $ 195.2 $ 29,108.8 Included in the “Current” and “30-89 non-performing non-accrual 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 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/loan-to-value 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 both March 31, 2017 and December 31, 2016, the allowance for loan losses on acquired loans was $6.3 million. The following is a summary, by class of loan, of credit quality indicators: As of March 31, 2017 (in millions) Commercial Commercial Equipment Total Commercial: Originated loans: Pass $ 9,788.5 $ 7,380.5 $ 2,554.0 $ 19,723.0 Special mention 117.2 115.8 98.5 331.5 Substandard 94.6 240.5 310.5 645.6 Doubtful 0.9 1.1 — 2.0 Total originated loans 10,001.2 7,737.9 2,963.0 20,702.1 Acquired loans: Pass 180.9 149.4 — 330.3 Special mention 8.0 3.5 5.0 16.5 Substandard 34.5 27.5 1.5 63.5 Doubtful 0.7 — — 0.7 Total acquired loans 224.1 180.4 6.5 411.0 Total $ 10,225.3 $ 7,918.3 $ 2,969.5 $ 21,113.1 As of March 31, 2017 (in millions) Residential Home Other Total Retail: Originated loans: Low risk $ 3,198.8 $ 935.4 $ 30.9 $ 4,165.1 Moderate risk 2,642.2 650.5 6.7 3,299.4 High risk 505.2 426.1 10.9 942.2 Total originated loans 6,346.2 2,012.0 48.5 8,406.7 Acquired loans: Low risk 69.2 — — 69.2 Moderate risk 31.0 — — 31.0 High risk 41.3 25.3 0.7 67.3 Total acquired loans 141.5 25.3 0.7 167.5 Total $ 6,487.7 $ 2,037.3 $ 49.2 $ 8,574.2 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 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 discount rate to those cash flows. Acquired loans are generally accounted for on a pool basis, with pools formed based on the loans’ common risk characteristics, such as loan collateral type and accrual status. Each pool is accounted for as a single asset with a single composite interest rate and an aggregate expectation of cash flows. Under the accounting model for 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 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 March 31, 2017, the outstanding principal balance and carrying amount of the acquired loan portfolio were $676.3 million and $578.5 million, respectively ($707.0 million and $610.2 million, respectively, at December 31, 2016). The following tables summarize activity in the accretable yield for the acquired loan portfolio: Three Months Ended March 31, (in millions) 2017 2016 Balance at beginning of period $ 255.4 $ 296.0 Accretion (7.6 ) (11.6 ) Reclassification from nonaccretable difference for loans with — — Other changes in expected cash flows (2) (6.1 ) (3.6 ) Balance at end of period $ 241.7 $ 280.8 (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. Other Real Estate Owned and Repossessed Assets (included in Other Assets) Other real estate owned (“REO”) was comprised of residential and commercial properties totaling $10.9 million and $4.1 million, respectively, at March 31, 2017, and $8.1 million and $4.0 million, respectively, at December 31, 2016. Repossessed assets totaled $8.2 million and $7.2 million at March 31, 2017 and December 31, 2016, respectively.

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2017
Equity [Abstract]
Stockholders' Equity	NOTE 4. STOCKHOLDERS’ EQUITY Preferred Stock People’s United is authorized to issue (i) 50.0 million shares of preferred stock, par value of $0.01 per share, of which 10.0 million shares were outstanding at both March 31, 2017 and December 31, 2016, and (ii) 1.95 billion shares of common stock, par value of $0.01 per share, of which 406.4 million shares and 405.0 million shares were issued at March 31, 2017 and December 31, 2016, respectively. Treasury Stock 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 both March 31, 2017 and 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”) (2.6 million and 2.7 million shares at March 31, 2017 and December 31, 2016, respectively). Following shareholder approval of the People’s United Financial, Inc. 2014 Long-Term Incentive Plan in 2014, no new awards may be granted under the RRP. 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 accumulated other comprehensive loss (“AOCL”), which are included in People’s United’s stockholders’ equity on an after-tax (in millions) Pension Net Unrealized Net Unrealized Net Unrealized Total Balance at December 31, 2016 $ (145.6 ) $ (32.3 ) $ (17.4 ) $ 0.3 $ (195.0 ) Other comprehensive income before reclassifications — 1.4 — 0.2 1.6 Amounts reclassified from AOCL (1) 1.0 9.9 0.5 0.1 11.5 Current period other comprehensive income 1.0 11.3 0.5 0.3 13.1 Balance at March 31, 2017 $ (144.6 ) $ (21.0 ) $ (16.9 ) $ 0.6 $ (181.9 ) (in millions) Pension Net Unrealized Net Unrealized Net Unrealized Total Balance at December 31, 2015 $ (140.0 ) $ (17.7 ) $ (19.5 ) $ — $ (177.2 ) Other comprehensive income (loss) before reclassifications — 41.0 — (0.2 ) 40.8 Amounts reclassified from AOCL (1) 1.0 — 0.5 0.2 1.7 Current period other comprehensive income 1.0 41.0 0.5 — 42.5 Balance at March 31, 2016 $ (139.0 ) $ 23.3 $ (19.0 ) $ — $ (134.7 ) (1) See the following table for details about these reclassifications. The following is a summary of the amounts reclassified from AOCL: Amounts Reclassified from AOCL Three Months Ended Affected Line Item (in millions) 2017 2016 Net Income is Presented Details about components of AOCL: Amortization of pension and other postretirement plans items: Net actuarial loss $ (1.7 ) $ (1.6 ) (1) Prior service credit 0.2 0.2 (1) (1.5 ) (1.4 ) Income before income tax expense 0.5 0.4 Income tax expense (1.0 ) (1.0 ) Net income Reclassification adjustment for net realized losses on securities available for sale (15.7 ) — Income before income tax expense (2) 5.8 — Income tax expense (9.9 ) — Net income Amortization of unrealized losses on securities transferred to held to maturity (0.8 ) (0.8 ) Income before income tax expense (3) 0.3 0.3 Income tax expense (0.5 ) (0.5 ) Net income Amortization of unrealized gains and losses on cash flow hedges: Interest rate swaps (0.1 ) (0.3 ) (5) Interest rate locks (4) — — (5) (0.1 ) (0.3 ) Income before income tax expense — 0.1 Income tax expense (0.1 ) (0.2 ) Net income Total reclassifications for the period $ (11.5 ) $ (1.7 ) (1) Included in the computation of net periodic benefit income (expense) reflected in compensation and benefits expense (2) Included in other non-interest (3) Included in interest and dividend income - securities. (4) Amount reclassified from AOCL totaled less than $0.1 million for both periods. (5) Included in interest expense - notes and debentures.

Earnings Per Common Share

Earnings Per Common Share	3 Months Ended
	Mar. 31, 2017
Earnings Per Share [Abstract]
Earnings Per Common Share	NOTE 5. EARNINGS PER COMMON SHARE The following is an analysis of People’s United’s basic and diluted earnings per common share (“EPS”), reflecting the application of the two-class Three Months Ended (in millions, except per common share data) 2017 2016 Net income available to common shareholders $ 67.3 $ 62.9 Dividends paid on and undistributed earnings allocated to (0.2 ) (0.2 ) Earnings attributable to common shareholders $ 67.1 $ 62.7 Weighted average common shares outstanding for basic EPS 308.8 301.9 Effect of dilutive equity-based awards 2.3 — Weighted average common and common-equivalent shares for diluted EPS 311.1 301.9 Basic EPS $ 0.22 $ 0.21 Diluted EPS $ 0.22 $ 0.21 Unvested share-based payment awards, which include the right to receive non-forfeitable two-class two-class All unallocated Employee Stock Ownership Plan (“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 9.8 million shares and 22.4 million shares for the three months ended March 31, 2017 and 2016, respectively, have also been excluded from the calculation of diluted EPS.

Goodwill and Other Acquisition-

Goodwill and Other Acquisition-Related Intangible Assets	3 Months Ended
	Mar. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Acquisition-Related Intangible Assets	NOTE 6. GOODWILL AND OTHER ACQUISITION-RELATED INTANGIBLE ASSETS People’s United’s goodwill totaled $1.99 billion at both March 31, 2017 and December 31, 2016. At both dates, goodwill was allocated to People’s United’s operating segments as follows: Commercial Banking ($1.22 billion); Retail Banking ($679.6 million); and Wealth Management ($91.0 million). 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 generally paid for the acquired entities which, in turn, resulted in the recognition of goodwill, representing the excess of the respective purchase prices over the estimated fair value of the net assets acquired. All of People’s United’s tax deductible goodwill was created in transactions in which the Company purchased the assets of the target (as opposed to purchasing the issued and outstanding stock of the target). At March 31, 2017 and December 31, 2016, tax deductible goodwill totaled $76.3 million and $77.9 million, respectively. People’s United’s other acquisition-related intangible assets totaled $143.1 million and $149.4 million at March 31, 2017 and December 31, 2016, respectively. At March 31, 2017, the carrying amounts of other acquisition-related intangible assets were as follows: trade name ($70.8 million); client relationship intangible ($23.5 million); trust relationship intangible ($16.4 million); core deposit intangible ($9.0 million); insurance relationship intangible ($5.9 million); favorable lease agreement ($0.6 million); non-compete Amortization expense of other acquisition-related intangible assets subject to amortization totaled $6.3 million and $5.8 million for the three months ended March 31, 2017 and 2016, respectively. Scheduled amortization expense attributable to other acquisition-related intangible assets for the full-year of 2017 and 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; $11.7 million in 2021; and $11.1 million in 2022. There were no impairment losses relating to goodwill or other acquisition-related intangible assets recorded during the three months ended March 31, 2017 and 2016.

Employee Benefit Plans

Employee Benefit Plans	3 Months Ended
	Mar. 31, 2017
Compensation and Retirement Disclosure [Abstract]
Employee Benefit Plans	NOTE 7. 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’s funding policy is to contribute the amounts required by applicable regulations, although additional amounts may be contributed from time to time. 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. Components of net periodic benefit (income) expense and other amounts recognized in other comprehensive income for the People’s Qualified Plan, the Chittenden Qualified Plan and the Supplemental Plans (together the “Pension Plans”) and the Other Postretirement Plan are as follows: Pension Plans Other Three months ended March 31 (in millions) 2017 2016 2017 2016 Net periodic benefit (income) expense: Service cost $ — $ — $ 0.1 $ 0.1 Interest cost 4.5 4.7 0.1 0.1 Expected return on plan assets (8.9 ) (8.6 ) — — Recognized net actuarial loss 1.6 1.5 0.1 0.1 Recognized prior service credit (0.2 ) (0.2 ) — — Settlements 0.4 0.3 — — Net periodic benefit (income) expense (2.6 ) (2.3 ) 0.3 0.3 Other changes in plan assets and benefit obligations recognized in Net actuarial loss (1.6 ) (1.5 ) (0.1 ) (0.1 ) Prior service credit 0.2 0.2 — — Total pre-tax (1.4 ) (1.3 ) (0.1 ) (0.1 ) Total recognized in net periodic benefit (income) expense and $ (4.0 ) $ (3.6 ) $ 0.2 $ 0.2 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 $1.2 million for the three months ended March 31, 2017. At March 31, 2017, 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 3,571,639 shares of People’s United common stock have been allocated or committed to be released to participants’ accounts. At March 31, 2017, 6,881,936 shares of People’s United common stock, with a fair value of $125.3 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

Legal Proceedings

Legal Proceedings	3 Months Ended
	Mar. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Legal Proceedings	NOTE 8. 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 its financial condition, results of operations or liquidity.

Segment Information

Segment Information	3 Months Ended
	Mar. 31, 2017
Segment Reporting [Abstract]
Segment Information	NOTE 9. SEGMENT INFORMATION See “Segment Results” included in Item 2 for segment information for the three months ended March 31, 2017 and 2016.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurements	NOTE 10. 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. 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, 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 7, 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 March 31, 2017 (in millions) Level 1 Level 2 Level 3 Total Financial assets: Trading account securities: U.S. Treasury $ 7.8 $ — $ — $ 7.8 Securities available for sale: U.S. Treasury and agency 798.7 — — 798.7 GSE mortgage-backed securities and CMOs — 2,964.5 — 2,964.5 Equity securities 8.9 — — 8.9 Other assets: Exchange-traded funds 31.6 — — 31.6 Fixed income securities — 3.6 — 3.6 Mutual funds 3.1 — — 3.1 Interest rate swaps — 96.2 — 168.6 Foreign exchange contracts — 0.2 — 0.2 Forward commitments to sell residential mortgage loans — 0.7 — 0.7 Total $ 850.1 $ 3,065.2 $ — $ 3,987.7 Financial liabilities: Interest rate swaps $ — $ 72.7 $ — $ 116.8 Risk participation agreements (1) — — — — Foreign exchange contracts — 0.1 — 0.1 Interest rate-lock commitments on residential mortgage loans — 0.9 — 0.9 Total $ — $ 73.7 $ — $ 117.8 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 (1) At both March 31, 2017 and December 31, 2016, the fair value of risk participation agreements totaled less than $0.1 million (see Note 11). There were no transfers into or out of the Level 1 or Level 2 categories during the three months ended March 31, 2017 or 2016. 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 March 31, 2017 (in millions) Level 1 Level 2 Level 3 Total Loans held for sale (1) $ — $ 17.1 $ — $ 17.1 Impaired loans (2) — — 65.7 65.7 REO and repossessed assets (3) — — 23.2 23.2 Total $ — $ 17.1 $ 88.9 $ 106.0 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 (1) Consists of residential mortgage loans; no fair value adjustments were recorded for the three months ended March 31, 2017 and 2016. (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 $50.8 million of Commercial loans and $14.9 million of Retail loans at March 31, 2017. The provision for loan losses on impaired loans totaled $3.5 million and $2.2 million for the three months ended March 31, 2017 and 2016, respectively. (3) Represents: (i) $10.9 million of residential REO; (ii) $4.1 million of commercial REO; and (iii) $8.2 million of repossessed assets at March 31, 2017. Charge-offs to the allowance for loan losses related to loans that were transferred to REO or repossessed assets totaled $0.4 million and $0.9 million for the three months ended March 31, 2017 and 2016, 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 previously, 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 interest rate risk (“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 Estimated Fair Value As of March 31, 2017 (in millions) Level 1 Level 2 Level 3 Total Financial assets: Cash and due from banks $ 380.8 $ 380.8 $ — $ — $ 380.8 Short-term investments 392.2 — 392.2 — 392.2 Securities held to maturity 2,324.0 — 2,338.0 1.5 2,339.5 FHLB and FRB stock 319.6 — 319.6 — 319.6 Total loans, net (1) 29,390.3 — 6,310.0 22,879.7 29,189.7 Financial liabilities: Time deposits 4,570.6 — 4,564.7 — 4,564.7 Other deposits 25,935.1 — 25,935.1 — 25,935.1 FHLB advances 2,160.4 — 2,162.6 — 2,162.6 Federal funds purchased 613.0 — 613.0 — 613.0 Customer repurchase agreements 327.7 — 327.7 — 327.7 Other borrowings 81.9 — 81.9 — 81.9 Notes and debentures 903.9 — 883.0 — 883.0 (1) Excludes impaired loans totaling $65.7 million measured at fair value on a non-recurring Carrying 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

Derivative Financial Instrument

Derivative Financial Instruments and Hedging Activities	3 Months Ended
	Mar. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Financial Instruments and Hedging Activities	NOTE 11. 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. 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. 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 12), 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). There were no derivative instruments with such credit-related contingent features in a net liability position at March 31, 2017. The following sections further discuss each class of derivative financial instrument used by People’s United, including management’s principal objectives and risk management strategies. Interest Rate Swaps People’s United may, from time to time, enter into interest rate swaps that are used to manage IRR associated with certain interest-earning assets and interest-bearing liabilities. The Bank has entered into a pay floating/receive fixed interest rate swap to reduce its interest rate risk exposure to the variability in interest cash flows on certain floating-rate commercial loans. 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 $110 million. The floating-rate interest payments made under the swap are calculated using the same floating rate received on the commercial loans. The swap effectively converts the floating-rate one-month LIBOR interest payments received on the commercial loans to a fixed rate and consequently reduces the Bank’s exposure to variability in short-term interest rates. This swap is accounted for as a cash flow hedge. 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 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. People’s United had previously entered into a pay fixed/receive floating interest rate swap to hedge the LIBOR-based floating rate payments on the Company’s $125 million 5.80% fixed-rate/floating-rate subordinated notes. On February 14, 2017, the Company repaid the subordinated notes and, concurrent with the repayment, the interest rate swap designated to these subordinated notes matured. This swap was accounted for as a cash flow 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) Notional Amounts Assets Liabilities (in millions) Type of March 31, Dec. 31, March 31, Dec. 31, March 31, Dec. 31, Derivatives Not Designated as Hedging Instruments: Interest rate swaps: Commercial customers N/A $ 5,786.0 $ 5,612.2 $ 85.3 $ 93.9 $ 50.9 $ 46.9 Institutional counterparties N/A 5,793.7 5,620.2 10.9 65.6 21.8 74.0 Risk participation agreements (2) N/A 268.6 251.9 — — — — Foreign exchange contracts N/A 41.9 101.2 0.2 0.6 0.1 0.3 Forward commitments to sell residential mortgage loans N/A 39.4 48.6 0.7 0.3 — — Interest rate-lock commitments on residential mortgage loans N/A 46.9 57.0 — — 0.9 0.4 Total 97.1 160.4 73.7 121.6 Derivatives Designated as Hedging Instruments: Interest rate swaps: Subordinated notes Fair value 375.0 375.0 — 13.6 — — Loans Cash flow 110.0 — — — — — Subordinated notes Cash flow — 125.0 — — — 0.1 Total — 13.6 — 0.1 Total fair value of derivatives $ 97.1 $ 174.0 $ 73.7 $ 121.7 (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 Type of Amount of Pre-Tax Gain (Loss) Amount of Pre-Tax Gain (Loss) Three months ended March 31 (in millions) 2017 2016 2017 2016 Derivatives Not Designated as Hedging Instruments: Interest rate swaps: Commercial customers N/A $ 2.5 $ 136.1 $ — $ — Institutional counterparties N/A 0.2 (132.9 ) — — Foreign exchange contracts N/A 0.1 (1.4 ) — — Risk participation agreements N/A 0.1 — — — Forward commitments to sell residential mortgage loans N/A 0.3 — — — Interest rate-lock commitments on residential mortgage loans N/A (0.3 ) (0.1 ) — — Total 2.9 1.7 — — Derivatives Designated as Hedging Instruments: Interest rate swaps Fair value 1.7 2.3 — — Interest rate swaps Cash flow (0.1 ) (0.3 ) — (0.3 ) Interest rate locks (2) Cash flow — — — — Total 1.7 2.3 — — Total $ 4.6 $ 4.0 $ — $ — (1) Amounts recognized in earnings are recorded in interest income, interest expense or other non-interest non-interest (2) Income totaled less than $0.1 million for both periods.

Balance Sheet Offsetting

Balance Sheet Offsetting	3 Months Ended
	Mar. 31, 2017
Text Block [Abstract]
Balance Sheet Offsetting	NOTE 12. 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” Effective January 3, 2017, the Chicago Mercantile Exchange (“CME”) amended their rulebooks to legally characterize variation margin payments for over-the-counter derivatives that clear as settlements rather than collateral. Accordingly, as of that date, the Company updated its accounting policies to classify, for accounting and presentation purposes, variation margin payments deemed to be legal settlements as a single unit of account with the related derivative(s). As of March 31, 2017, this amendment impacted one of the Company’s institutional counterparties. Accordingly, People’s United has, subject to the corresponding enforceable master netting arrangement, netted the institutional counterparty’s CME derivative position and offset the counterparty’s variation margin payments in the Consolidated Statement of Condition as of March 31, 2017. 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. 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 11. The Company’s derivative contracts with commercial customers and customer repurchase agreements are not subject to master netting arrangements and, therefore, have been excluded from the tables below. Gross Gross Net Gross Amounts Not Offset Net As of March 31, 2017 (in millions) Financial Collateral Financial assets: Interest rate swaps: Counterparty A $ 2.1 $ — $ 2.1 $ (2.1 ) $ — $ — Counterparty B 1.3 — 1.3 (1.3 ) — — Counterparty C 2.0 — 2.0 (2.0 ) — — Counterparty D 3.5 — 3.5 (3.5 ) — — Other counterparties 2.0 — 2.0 (0.3 ) (1.6 ) 0.1 Foreign exchange contracts 0.2 — 0.2 — — 0.2 Total $ 11.1 $ — $ 11.1 $ (9.2 ) $ (1.6 ) $ 0.3 Financial liabilities: Interest rate swaps: Counterparty A $ 3.7 $ — $ 3.7 $ (2.1 ) $ (1.6 ) $ — Counterparty B 7.0 — 7.0 (1.3 ) (5.7 ) — Counterparty C 3.5 — 3.5 (2.0 ) (1.5 ) — Counterparty D 6.2 — 6.2 (3.5 ) (2.5 ) 0.2 Other counterparties 1.4 — 1.4 (0.3 ) (1.1 ) — Foreign exchange contracts 0.1 — 0.1 — — 0.1 Total $ 21.9 $ — $ 21.9 $ (9.2 ) $ (12.4 ) $ 0.3 Gross Gross Net Gross Amounts Not Offset Net As of December 31, 2016 (in millions) Financial Collateral 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

New Accounting Standards

New Accounting Standards	3 Months Ended
	Mar. 31, 2017
Accounting Changes and Error Corrections [Abstract]
New Accounting Standards	NOTE 13. NEW ACCOUNTING STANDARDS Standards effective in 2017 Derivatives and Hedging In March 2016, the Financial Accounting Standards Board (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. These amendments, which are being applied prospectively, became effective for People’s United on January 1, 2017 and did not 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, which is being applied prospectively, became effective for People’s United on January 1, 2017 and did not 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 payment awards, including: (i) the related income tax consequences; (ii) the classification of awards as either equity or liabilities; and (iii) the classification in the statement of cash flows. This amendment, which is being applied prospectively, became effective for People’s United on January 1, 2017. As a result, the Company realized windfall tax benefits totaling $1.0 million for the three months ended March 31, 2017. This amount, which was recognized as a discrete period income tax benefit, served to lower the Company’s effective tax rate for the period by 1%. 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 non-interest 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. While the Company continues to monitor the potential impact of the amended guidance on its Consolidated Financial Statements, such impact is indeterminable at this time as it will be dependent upon portfolio composition at the adoption date. As noted in Note 2, at March 31, 2017, the Company’s securities portfolio included equity securities with an amortized cost of $9.6 million and a fair value of $8.9 million. 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 Asset Derecognition and Accounting for Partial Sales of Nonfinancial Assets In February 2017, the FASB amended its standards to clarify the scope of its guidance on derecognition of a nonfinancial asset and provide additional guidance on the definition of in-substance Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost In March 2017, the FASB amended its standards to (i) require that the service cost component of net benefit cost associated with pension and postretirement plans be reported in the same line item in which the related employees’ compensation cost is reported and (ii) specify that only the service cost component is eligible for capitalization. The other components of net benefit cost, which may not be capitalized, are to be presented below income from operations (if presented). For public business entities, this new guidance 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 early adoption is permitted. The adoption of this amendment is not expected to have a significant impact on the Company’s Consolidated Financial Statements. 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 regulators with respect to how the impact of the amended standard is to be treated for regulatory capital purposes. Premium Amortization – Purchased Callable Debt Securities In April 2017, the FASB amended its standards to shorten the amortization period for certain callable debt securities held at a premium, requiring such premiums to be amortized to the earliest call date unless applicable guidance related to certain pools of securities is applied to consider estimated prepayments. Under prior guidance, entities were generally required to amortize premiums on individual, non-pooled 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. In addition, the Company has initiated the development of an implementation plan which includes an evaluation of selected third-party vendor solutions intended to aid in the application of the amended standards. 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 regulators 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.

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2017
Subsequent Events [Abstract]
Subsequent Events	NOTE 14. SUBSEQUENT EVENTS Acquisition of Suffolk Bancorp Effective April 1, 2017, People’s United completed its acquisition of Suffolk Bancorp (“Suffolk”) based in Riverhead, New York. Accordingly, People’s United’s consolidated financial statements as of and for the period ended March 31, 2017 do not include Suffolk. At March 31, 2017, Suffolk had total loans of $1.66 billion, total deposits of $1.85 billion and operated 27 branches in the greater Long Island area. Total consideration paid in the Suffolk acquisition consisted of approximately 26.6 million shares of People’s United common stock with a fair value of approximately $485 million. Merger-related expenses totaling $1.0 million relating to this transaction were recorded in the three months ended March 31, 2017.

Employee Benefit Plans (Policie

Employee Benefit Plans (Policies)	3 Months Ended
	Mar. 31, 2017
Compensation and Retirement Disclosure [Abstract]
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’s funding policy is to contribute the amounts required by applicable regulations, although additional amounts may be contributed from time to time. 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.
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 $1.2 million for the three months ended March 31, 2017. At March 31, 2017, 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 3,571,639 shares of People’s United common stock have been allocated or committed to be released to participants’ accounts. At March 31, 2017, 6,881,936 shares of People’s United common stock, with a fair value of $125.3 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
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. 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, 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 7, 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. 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 Financial Assets and Financial Liabilities Not Measured At Fair Value As discussed previously, 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 interest rate risk (“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.

Securities and Short-Term Inv24

Securities and Short-Term Investments (Tables)	3 Months Ended
	Mar. 31, 2017
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 March 31, 2017 (in millions) Amortized Gross Gross Fair Securities available for sale: Debt securities: U.S. Treasury and agency $ 822.7 $ 0.3 $ (24.3 ) $ 798.7 GSE (1) mortgage-backed securities and CMOs (2) 2,976.5 13.5 (25.5 ) 2,964.5 Total debt securities 3,799.2 13.8 (49.8 ) 3,763.2 Equity securities (3) 9.6 — (0.7 ) 8.9 Total securities available for sale $ 3,808.8 $ 13.8 $ (50.5 ) $ 3,772.1 Securities held to maturity: Debt securities: State and municipal $ 1,663.0 $ 40.2 $ (21.7 ) $ 1,681.5 GSE mortgage-backed securities 648.8 0.2 (3.4 ) 645.6 Corporate 10.7 0.2 — 10.9 Other 1.5 — — 1.5 Total securities held to maturity $ 2,324.0 $ 40.6 $ (25.1 ) $ 2,339.5 (1) Government sponsored enterprise (2) Collateralized mortgage obligations (3) During the quarter ended March 31, 2017, the Company exchanged its ownership interest in a non-marketable equity security (previously recorded in other assets) for cash and common stock in a publicly-traded company (fair value of approximately $10.8 million at acquisition). As of December 31, 2016 (in millions) Amortized Gross Gross Fair 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 Corporate 4.0 — — 4.0 Other 1.5 — — 1.5 Total securities held to maturity $ 2,005.4 $ 33.9 $ (26.7 ) $ 2,012.6
Summary of Amortized Cost and Fair Value of Debt Securities Based on Remaining Period to Contractual Maturity	The following table is a summary of the amortized cost and fair value of debt securities as of March 31, 2017, 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 (in millions) Amortized Fair Amortized Fair U.S. Treasury and agency: Within 1 year $ 1.0 $ 1.0 $ — $ — After 1 but within 5 years 238.7 235.7 — — After 5 but within 10 years 583.0 562.0 — — Total 822.7 798.7 — — GSE mortgage-backed securities and CMOs: After 5 but within 10 years 1,016.3 1,028.3 166.6 166.6 After 10 years 1,960.2 1,936.2 482.2 479.0 Total 2,976.5 2,964.5 648.8 645.6 State and municipal: Within 1 year — — 4.2 4.2 After 1 but within 5 years — — 30.7 31.3 After 5 but within 10 years — — 363.1 381.5 After 10 years — — 1,265.0 1,264.5 Total — — 1,663.0 1,681.5 Corporate: After 5 but within 10 years — — 5.7 5.8 After 10 years — — 5.0 5.1 Total — — 10.7 10.9 Other: Within 1 year — — 1.5 1.5 Total — — 1.5 1.5 Total: Within 1 year 1.0 1.0 5.7 5.7 After 1 but within 5 years 238.7 235.7 30.7 31.3 After 5 but within 10 years 1,599.3 1,590.3 535.4 553.9 After 10 years 1,960.2 1,936.2 1,752.2 1,748.6 Total $ 3,799.2 $ 3,763.2 $ 2,324.0 $ 2,339.5
Continuous Unrealized Loss Position on Available-for-Sale and Held-to-Maturities Securities	The following tables summarize those securities with unrealized losses, segregated by the length of time the securities have been in a continuous unrealized loss position at the respective dates. Certain unrealized losses totaled less than $0.1 million. Continuous Unrealized Loss Position Less Than 12 Months 12 Months Or Longer Total As of March 31, 2017 (in millions) Fair Unrealized Fair Unrealized Fair Unrealized Securities available for sale: GSE mortgage-backed securities and CMOs $ 2,315.0 $ (23.2 ) $ 62.0 $ (2.3 ) $ 2,377.0 $ (25.5 ) U.S. Treasury and agency 768.4 (24.3 ) — — 768.4 (24.3 ) Equity securities 8.9 (0.7 ) — — 8.9 (0.7 ) Securities held to maturity: GSE mortgage-backed securities 553.1 (3.4 ) — — 553.1 (3.4 ) State and municipal 600.3 (21.7 ) 0.1 — 600.4 (21.7 ) Total $ 4,245.7 $ (73.3 ) $ 62.1 $ (2.3 ) $ 4,307.8 $ (75.6 ) Continuous Unrealized Loss Position Less Than 12 Months 12 Months Or Longer Total As of December 31, 2016 (in millions) Fair Unrealized Fair Unrealized Fair Unrealized 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 )

Loans (Tables)

Loans (Tables)	3 Months Ended
	Mar. 31, 2017
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: March 31, 2017 December 31, 2016 (in millions) Originated Acquired Total Originated Acquired Total Commercial: Commercial real estate $ 10,001.2 $ 224.1 $ 10,225.3 $ 10,012.6 $ 234.7 $ 10,247.3 Commercial and industrial 7,737.9 180.4 7,918.3 7,939.0 186.1 8,125.1 Equipment financing 2,963.0 6.5 2,969.5 3,020.9 11.6 3,032.5 Total Commercial Portfolio 20,702.1 411.0 21,113.1 20,972.5 432.4 21,404.9 Retail: Residential mortgage: Adjustable-rate 5,699.1 91.1 5,790.2 5,453.8 95.3 5,549.1 Fixed-rate 647.1 50.4 697.5 613.5 54.1 667.6 Total residential mortgage 6,346.2 141.5 6,487.7 6,067.3 149.4 6,216.7 Home equity and other consumer: Home equity 2,012.0 25.3 2,037.3 2,044.9 27.7 2,072.6 Other consumer 48.5 0.7 49.2 50.0 0.7 50.7 Total home equity and other consumer 2,060.5 26.0 2,086.5 2,094.9 28.4 2,123.3 Total Retail Portfolio 8,406.7 167.5 8,574.2 8,162.2 177.8 8,340.0 Total loans $ 29,108.8 $ 578.5 $ 29,687.3 $ 29,134.7 $ 610.2 $ 29,744.9
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 three months ended March 31, 2017 and 2016. 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. Three months ended Commercial Retail March 31, 2017 (in millions) Originated Acquired Total Originated Acquired Total Total Balance at beginning of period $ 198.8 $ 6.1 $ 204.9 $ 24.2 $ 0.2 $ 24.4 $ 229.3 Charge-offs (2.9 ) — (2.9 ) (1.7 ) — (1.7 ) (4.6 ) Recoveries 1.6 — 1.6 0.6 — 0.6 2.2 Net loan charge-offs (1.3 ) — (1.3 ) (1.1 ) — (1.1 ) (2.4 ) Provision for loan losses (2.4 ) — (2.4 ) 6.8 — 6.8 4.4 Balance at end of period $ 195.1 $ 6.1 $ 201.2 $ 29.9 $ 0.2 $ 30.1 $ 231.3 Three months ended Commercial Retail March 31, 2016 (in millions) Originated Acquired Total Originated Acquired Total Total Balance at beginning of period $ 181.8 $ 7.9 $ 189.7 $ 21.1 $ 0.2 $ 21.3 $ 211.0 Charge-offs (4.6 ) (0.3 ) (4.9 ) (2.8 ) — (2.8 ) (7.7 ) Recoveries 0.4 — 0.4 1.3 — 1.3 1.7 Net loan charge-offs (4.2 ) (0.3 ) (4.5 ) (1.5 ) — (1.5 ) (6.0 ) Provision for loan losses 7.3 0.1 7.4 3.1 — 3.1 10.5 Balance at end of period $ 184.9 $ 7.7 $ 192.6 $ 22.7 $ 0.2 $ 22.9 $ 215.5
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 March 31, 2017 Originated Loans Originated Loans Acquired Loans Total (in millions) Portfolio Allowance Portfolio Allowance Portfolio Allowance Portfolio Allowance Commercial $ 176.2 $ 8.1 $ 20,525.9 $ 187.0 $ 411.0 $ 6.1 $ 21,113.1 $ 201.2 Retail 94.1 3.2 8,312.6 26.7 167.5 0.2 8,574.2 30.1 Total $ 270.3 $ 11.3 $ 28,838.5 $ 213.7 $ 578.5 $ 6.3 $ 29,687.3 $ 231.3 As of December 31, 2016 Originated Loans Originated Loans Acquired Loans Total (in millions) 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
Summarized Recorded Investments, by Class of Loan, of Originated Non-Performing Loans	The recorded investments, by class of loan, of originated non-performing (in millions) March 31, December 31, Commercial: Commercial real estate $ 23.4 $ 22.3 Commercial and industrial 47.4 41.5 Equipment financing 47.4 39.4 Total (1) 118.2 103.2 Retail: Residential mortgage 26.3 27.4 Home equity 15.2 17.4 Other consumer — — Total (2) 41.5 44.8 Total $ 159.7 $ 148.0 (1) Reported net of government guarantees totaling $4.4 million and $13.1 million at March 31, 2017 and December 31, 2016, 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 March 31, 2017, the principal loan classes to which these government guarantees relate are commercial and industrial loans (99%) and commercial real estate loans (1%). (2) Includes $11.8 million and $9.8 million of loans in the process of foreclosure at March 31, 2017 and December 31, 2016, 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 three months ended March 31, 2017 and 2016. For purposes of this disclosure, recorded investments represent amounts immediately prior to and subsequent to the restructuring. Three Months Ended March 31, 2017 (dollars in millions) Number Pre-Modification Post-Modification Commercial: Commercial real estate (1) 3 $ 3.9 $ 3.9 Commercial and industrial (2) 9 8.3 8.3 Equipment financing (3) 21 5.9 5.9 Total 33 18.1 18.1 Retail: Residential mortgage (4) 7 3.8 3.8 Home equity (5) 24 2.2 2.2 Other consumer — — — Total 31 6.0 6.0 Total 64 $ 24.1 $ 24.1 (1) Represents the following concessions: reduced payment and/or payment deferral (2 contracts; recorded investment of $2.2 million); or temporary rate reduction (1 contract; recorded investment of $1.7 million). (2) Represents the following concessions: extension of term (8 contracts; recorded investment of $7.4 million); or reduced payment and/or payment deferral (1 contract; recorded investment of $0.9 million). (3) Represents the following concessions: reduced payment and/or payment deferral (7 contracts; recorded investment of $2.3 million); or a combination of concessions (14 contracts; recorded investment of $3.6 million). (4) Represents the following concessions: loans restructured through bankruptcy (1 contract; recorded investment of $0.1 million); reduced payment and/or payment deferral (4 contracts; recorded investment of $1.3 million); or a combination of concessions (2 contracts; recorded investment of $2.4 million). (5) Represents the following concessions: loans restructured through bankruptcy (14 contracts; recorded investment of $1.1 million); reduced payment and/or payment deferral (4 contracts; recorded investment of $0.3 million); or a combination of concessions (6 contracts; recorded investment of $0.8 million). Three Months Ended March 31, 2016 (dollars in millions) Number Pre-Modification Post-Modification Commercial: Commercial real estate (1) 3 $ 1.1 $ 1.1 Commercial and industrial (2) 13 5.2 5.2 Equipment financing (3) 10 6.1 6.1 Total 26 12.4 12.4 Retail: Residential mortgage (4) 19 5.3 5.3 Home equity (5) 19 1.6 1.6 Other consumer — — — Total 38 6.9 6.9 Total 64 $ 19.3 $ 19.3 (1) Represents the following concessions: extension of term (1 contract; recorded investment of $0.2 million); reduced payment and/or payment deferral (1 contract; recorded investment of $0.9 million); or a combination of concessions (1 contract; recorded investment of less than $0.1 million). (2) Represents the following concessions: extension of term (7 contracts; recorded investment of $4.4 million); reduced payment and/or payment deferral (3 contracts; recorded investment of $0.4 million); or a combination of concessions (3 contracts; recorded investment of $0.4 million). (3) Represents the following concessions: extension of term (2 contracts; recorded investment of $0.4 million); reduced payment and/or payment deferral (5 contracts; recorded investment of $4.3 million); or a combination of concessions (3 contracts; recorded investment of $1.4 million). (4) Represents the following concessions: loans restructured through bankruptcy (4 contracts; recorded investment of $1.5 million); reduced payment and/or payment deferral (5 contracts; recorded investment of $1.4 million); or a combination of concessions (10 contracts; recorded investment of $2.4 million). (5) Represents the following concessions: loans restructured through bankruptcy (14 contracts; recorded investment of $1.3 million); reduced payment and/or payment deferral (1 contract; recorded investment of $0.1 million); or a combination of concessions (4 contracts; recorded investment of $0.2 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 three months ended March 31, 2017 and 2016. For purposes of this disclosure, the previous 12 months is measured from April 1 of the respective prior year and a default represents a previously-modified loan that became past due 30 days or more during the three months ended March 31, 2017 or 2016. Three Months Ended March 31, 2017 2016 (dollars in millions) Number Recorded Number Recorded Commercial: Commercial real estate 1 $ 1.7 — $ — Commercial and industrial 2 1.4 2 0.6 Equipment financing 8 2.6 5 2.5 Total 11 5.7 7 3.1 Retail: Residential mortgage 7 2.5 6 1.3 Home equity 1 0.1 7 0.5 Other consumer — — — — Total 8 2.6 13 1.8 Total 19 $ 8.3 20 $ 4.9
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. As of March 31, 2017 As of December 31, 2016 (in millions) Unpaid Recorded Related Unpaid Recorded Related Without a related allowance for loan losses: Commercial: Commercial real estate $ 49.0 $ 47.4 $ — $ 41.4 $ 40.0 $ — Commercial and industrial 42.6 40.7 — 50.7 45.7 — Equipment financing 41.0 37.3 — 38.2 35.3 — Retail: Residential mortgage 66.6 60.7 — 63.6 58.0 — Home equity 22.2 18.5 — 22.4 18.7 — Other consumer — — — — — — Total $ 221.4 $ 204.6 $ — $ 216.3 $ 197.7 $ — With a related allowance for loan losses: Commercial: Commercial real estate $ 8.5 $ 8.3 $ 0.4 $ 12.2 $ 11.4 $ 0.6 Commercial and industrial 33.5 32.6 6.1 25.9 25.0 4.7 Equipment financing 10.9 9.9 1.6 5.0 4.4 0.5 Retail: Residential mortgage 12.5 12.5 2.2 13.1 13.1 2.3 Home equity 2.4 2.4 1.0 2.1 2.0 0.9 Other consumer — — — — — — Total $ 67.8 $ 65.7 $ 11.3 $ 58.3 $ 55.9 $ 9.0 Total impaired loans: Commercial: Commercial real estate $ 57.5 $ 55.7 $ 0.4 $ 53.6 $ 51.4 $ 0.6 Commercial and industrial 76.1 73.3 6.1 76.6 70.7 4.7 Equipment financing 51.9 47.2 1.6 43.2 39.7 0.5 Total 185.5 176.2 8.1 173.4 161.8 5.8 Retail: Residential mortgage 79.1 73.2 2.2 76.7 71.1 2.3 Home equity 24.6 20.9 1.0 24.5 20.7 0.9 Other consumer — — — — — — Total 103.7 94.1 3.2 101.2 91.8 3.2 Total $ 289.2 $ 270.3 $ 11.3 $ 274.6 $ 253.6 $ 9.0
Schedule of Impaired Financing Receivable	The following tables summarize, 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 Three Months Ended March 31, 2017 2016 (in millions) Average Interest Average Interest Commercial: Commercial real estate $ 51.9 $ 0.4 $ 60.2 $ 0.3 Commercial and industrial 70.0 0.5 63.0 0.4 Equipment financing 39.8 0.1 33.1 0.1 Total 161.7 1.0 156.3 0.8 Retail: Residential mortgage 71.2 0.4 72.2 0.4 Home equity 20.4 0.1 22.4 0.1 Other consumer — — — — Total 91.6 0.5 94.6 0.5 Total $ 253.3 $ 1.5 $ 250.9 $ 1.3
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 March 31, 2017 (in millions) Current 30-89 90 Days Total Total Commercial: Commercial real estate $ 9,979.5 $ 13.1 $ 8.6 $ 21.7 $ 10,001.2 Commercial and industrial 7,700.8 18.3 18.8 37.1 7,737.9 Equipment financing 2,880.7 70.0 12.3 82.3 2,963.0 Total 20,561.0 101.4 39.7 141.1 20,702.1 Retail: Residential mortgage 6,304.8 24.3 17.1 41.4 6,346.2 Home equity 1,999.5 5.6 6.9 12.5 2,012.0 Other consumer 48.3 0.2 — 0.2 48.5 Total 8,352.6 30.1 24.0 54.1 8,406.7 Total originated loans $ 28,913.6 $ 131.5 $ 63.7 $ 195.2 $ 29,108.8 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
Summary of Credit Quality Indicators by Class of Loan	The following is a summary, by class of loan, of credit quality indicators: As of March 31, 2017 (in millions) Commercial Commercial Equipment Total Commercial: Originated loans: Pass $ 9,788.5 $ 7,380.5 $ 2,554.0 $ 19,723.0 Special mention 117.2 115.8 98.5 331.5 Substandard 94.6 240.5 310.5 645.6 Doubtful 0.9 1.1 — 2.0 Total originated loans 10,001.2 7,737.9 2,963.0 20,702.1 Acquired loans: Pass 180.9 149.4 — 330.3 Special mention 8.0 3.5 5.0 16.5 Substandard 34.5 27.5 1.5 63.5 Doubtful 0.7 — — 0.7 Total acquired loans 224.1 180.4 6.5 411.0 Total $ 10,225.3 $ 7,918.3 $ 2,969.5 $ 21,113.1 As of March 31, 2017 (in millions) Residential Home Other Total Retail: Originated loans: Low risk $ 3,198.8 $ 935.4 $ 30.9 $ 4,165.1 Moderate risk 2,642.2 650.5 6.7 3,299.4 High risk 505.2 426.1 10.9 942.2 Total originated loans 6,346.2 2,012.0 48.5 8,406.7 Acquired loans: Low risk 69.2 — — 69.2 Moderate risk 31.0 — — 31.0 High risk 41.3 25.3 0.7 67.3 Total acquired loans 141.5 25.3 0.7 167.5 Total $ 6,487.7 $ 2,037.3 $ 49.2 $ 8,574.2 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
Summarized Activity in Accretable Yield for Acquired Loan Portfolio	The following tables summarize activity in the accretable yield for the acquired loan portfolio: Three Months Ended March 31, (in millions) 2017 2016 Balance at beginning of period $ 255.4 $ 296.0 Accretion (7.6 ) (11.6 ) Reclassification from nonaccretable difference for loans with — — Other changes in expected cash flows (2) (6.1 ) (3.6 ) Balance at end of period $ 241.7 $ 280.8 (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.

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	3 Months Ended
	Mar. 31, 2017
Equity [Abstract]
Schedule of Accumulated Other Comprehensive Loss	The following is a summary of the changes in the components of accumulated other comprehensive loss (“AOCL”), which are included in People’s United’s stockholders’ equity on an after-tax (in millions) Pension Net Unrealized Net Unrealized Net Unrealized Total Balance at December 31, 2016 $ (145.6 ) $ (32.3 ) $ (17.4 ) $ 0.3 $ (195.0 ) Other comprehensive income before reclassifications — 1.4 — 0.2 1.6 Amounts reclassified from AOCL (1) 1.0 9.9 0.5 0.1 11.5 Current period other comprehensive income 1.0 11.3 0.5 0.3 13.1 Balance at March 31, 2017 $ (144.6 ) $ (21.0 ) $ (16.9 ) $ 0.6 $ (181.9 ) (in millions) Pension Net Unrealized Net Unrealized Net Unrealized Total Balance at December 31, 2015 $ (140.0 ) $ (17.7 ) $ (19.5 ) $ — $ (177.2 ) Other comprehensive income (loss) before reclassifications — 41.0 — (0.2 ) 40.8 Amounts reclassified from AOCL (1) 1.0 — 0.5 0.2 1.7 Current period other comprehensive income 1.0 41.0 0.5 — 42.5 Balance at March 31, 2016 $ (139.0 ) $ 23.3 $ (19.0 ) $ — $ (134.7 ) (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: Amounts Reclassified from AOCL Three Months Ended Affected Line Item (in millions) 2017 2016 Net Income is Presented Details about components of AOCL: Amortization of pension and other postretirement plans items: Net actuarial loss $ (1.7 ) $ (1.6 ) (1) Prior service credit 0.2 0.2 (1) (1.5 ) (1.4 ) Income before income tax expense 0.5 0.4 Income tax expense (1.0 ) (1.0 ) Net income Reclassification adjustment for net realized losses on securities available for sale (15.7 ) — Income before income tax expense (2) 5.8 — Income tax expense (9.9 ) — Net income Amortization of unrealized losses on securities transferred to held to maturity (0.8 ) (0.8 ) Income before income tax expense (3) 0.3 0.3 Income tax expense (0.5 ) (0.5 ) Net income Amortization of unrealized gains and losses on cash flow hedges: Interest rate swaps (0.1 ) (0.3 ) (5) Interest rate locks (4) — — (5) (0.1 ) (0.3 ) Income before income tax expense — 0.1 Income tax expense (0.1 ) (0.2 ) Net income Total reclassifications for the period $ (11.5 ) $ (1.7 ) (1) Included in the computation of net periodic benefit income (expense) reflected in compensation and benefits expense (2) Included in other non-interest (3) Included in interest and dividend income - securities. (4) Amount reclassified from AOCL totaled less than $0.1 million for both periods. (5) Included in interest expense - notes and debentures.

Earnings Per Common Share (Tabl

Earnings Per Common Share (Tables)	3 Months Ended
	Mar. 31, 2017
Earnings Per Share [Abstract]
Basic and Diluted Earnings Per Common Share, Reflecting Application of Two-Class Method	The following is an analysis of People’s United’s basic and diluted earnings per common share (“EPS”), reflecting the application of the two-class Three Months Ended (in millions, except per common share data) 2017 2016 Net income available to common shareholders $ 67.3 $ 62.9 Dividends paid on and undistributed earnings allocated to (0.2 ) (0.2 ) Earnings attributable to common shareholders $ 67.1 $ 62.7 Weighted average common shares outstanding for basic EPS 308.8 301.9 Effect of dilutive equity-based awards 2.3 — Weighted average common and common-equivalent shares for diluted EPS 311.1 301.9 Basic EPS $ 0.22 $ 0.21 Diluted EPS $ 0.22 $ 0.21

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	3 Months Ended
	Mar. 31, 2017
Compensation and Retirement Disclosure [Abstract]
Components of Net Periodic Benefit (Income) Expense and Other Amounts	Components of net periodic benefit (income) expense and other amounts recognized in other comprehensive income for the People’s Qualified Plan, the Chittenden Qualified Plan and the Supplemental Plans (together the “Pension Plans”) and the Other Postretirement Plan are as follows: Pension Plans Other Three months ended March 31 (in millions) 2017 2016 2017 2016 Net periodic benefit (income) expense: Service cost $ — $ — $ 0.1 $ 0.1 Interest cost 4.5 4.7 0.1 0.1 Expected return on plan assets (8.9 ) (8.6 ) — — Recognized net actuarial loss 1.6 1.5 0.1 0.1 Recognized prior service credit (0.2 ) (0.2 ) — — Settlements 0.4 0.3 — — Net periodic benefit (income) expense (2.6 ) (2.3 ) 0.3 0.3 Other changes in plan assets and benefit obligations recognized in Net actuarial loss (1.6 ) (1.5 ) (0.1 ) (0.1 ) Prior service credit 0.2 0.2 — — Total pre-tax (1.4 ) (1.3 ) (0.1 ) (0.1 ) Total recognized in net periodic benefit (income) expense and $ (4.0 ) $ (3.6 ) $ 0.2 $ 0.2

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2017
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 March 31, 2017 (in millions) Level 1 Level 2 Level 3 Total Financial assets: Trading account securities: U.S. Treasury $ 7.8 $ — $ — $ 7.8 Securities available for sale: U.S. Treasury and agency 798.7 — — 798.7 GSE mortgage-backed securities and CMOs — 2,964.5 — 2,964.5 Equity securities 8.9 — — 8.9 Other assets: Exchange-traded funds 31.6 — — 31.6 Fixed income securities — 3.6 — 3.6 Mutual funds 3.1 — — 3.1 Interest rate swaps — 96.2 — 168.6 Foreign exchange contracts — 0.2 — 0.2 Forward commitments to sell residential mortgage loans — 0.7 — 0.7 Total $ 850.1 $ 3,065.2 $ — $ 3,987.7 Financial liabilities: Interest rate swaps $ — $ 72.7 $ — $ 116.8 Risk participation agreements (1) — — — — Foreign exchange contracts — 0.1 — 0.1 Interest rate-lock commitments on residential mortgage loans — 0.9 — 0.9 Total $ — $ 73.7 $ — $ 117.8 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 (1) At both March 31, 2017 and December 31, 2016, the fair value of risk participation agreements totaled less than $0.1 million (see Note 11).
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 March 31, 2017 (in millions) Level 1 Level 2 Level 3 Total Loans held for sale (1) $ — $ 17.1 $ — $ 17.1 Impaired loans (2) — — 65.7 65.7 REO and repossessed assets (3) — — 23.2 23.2 Total $ — $ 17.1 $ 88.9 $ 106.0 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 (1) Consists of residential mortgage loans; no fair value adjustments were recorded for the three months ended March 31, 2017 and 2016. (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 $50.8 million of Commercial loans and $14.9 million of Retail loans at March 31, 2017. The provision for loan losses on impaired loans totaled $3.5 million and $2.2 million for the three months ended March 31, 2017 and 2016, respectively. (3) Represents: (i) $10.9 million of residential REO; (ii) $4.1 million of commercial REO; and (iii) $8.2 million of repossessed assets at March 31, 2017. Charge-offs to the allowance for loan losses related to loans that were transferred to REO or repossessed assets totaled $0.4 million and $0.9 million for the three months ended March 31, 2017 and 2016, 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 Estimated Fair Value As of March 31, 2017 (in millions) Level 1 Level 2 Level 3 Total Financial assets: Cash and due from banks $ 380.8 $ 380.8 $ — $ — $ 380.8 Short-term investments 392.2 — 392.2 — 392.2 Securities held to maturity 2,324.0 — 2,338.0 1.5 2,339.5 FHLB and FRB stock 319.6 — 319.6 — 319.6 Total loans, net (1) 29,390.3 — 6,310.0 22,879.7 29,189.7 Financial liabilities: Time deposits 4,570.6 — 4,564.7 — 4,564.7 Other deposits 25,935.1 — 25,935.1 — 25,935.1 FHLB advances 2,160.4 — 2,162.6 — 2,162.6 Federal funds purchased 613.0 — 613.0 — 613.0 Customer repurchase agreements 327.7 — 327.7 — 327.7 Other borrowings 81.9 — 81.9 — 81.9 Notes and debentures 903.9 — 883.0 — 883.0 (1) Excludes impaired loans totaling $65.7 million measured at fair value on a non-recurring Carrying 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

Derivative Financial Instrume30

Derivative Financial Instruments and Hedging Activities (Tables)	3 Months Ended
	Mar. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
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) Notional Amounts Assets Liabilities (in millions) Type of March 31, Dec. 31, March 31, Dec. 31, March 31, Dec. 31, Derivatives Not Designated as Hedging Instruments: Interest rate swaps: Commercial customers N/A $ 5,786.0 $ 5,612.2 $ 85.3 $ 93.9 $ 50.9 $ 46.9 Institutional counterparties N/A 5,793.7 5,620.2 10.9 65.6 21.8 74.0 Risk participation agreements (2) N/A 268.6 251.9 — — — — Foreign exchange contracts N/A 41.9 101.2 0.2 0.6 0.1 0.3 Forward commitments to sell residential mortgage loans N/A 39.4 48.6 0.7 0.3 — — Interest rate-lock commitments on residential mortgage loans N/A 46.9 57.0 — — 0.9 0.4 Total 97.1 160.4 73.7 121.6 Derivatives Designated as Hedging Instruments: Interest rate swaps: Subordinated notes Fair value 375.0 375.0 — 13.6 — — Loans Cash flow 110.0 — — — — — Subordinated notes Cash flow — 125.0 — — — 0.1 Total — 13.6 — 0.1 Total fair value of derivatives $ 97.1 $ 174.0 $ 73.7 $ 121.7 (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 Type of Amount of Pre-Tax Gain (Loss) Amount of Pre-Tax Gain (Loss) Three months ended March 31 (in millions) 2017 2016 2017 2016 Derivatives Not Designated as Hedging Instruments: Interest rate swaps: Commercial customers N/A $ 2.5 $ 136.1 $ — $ — Institutional counterparties N/A 0.2 (132.9 ) — — Foreign exchange contracts N/A 0.1 (1.4 ) — — Risk participation agreements N/A 0.1 — — — Forward commitments to sell residential mortgage loans N/A 0.3 — — — Interest rate-lock commitments on residential mortgage loans N/A (0.3 ) (0.1 ) — — Total 2.9 1.7 — — Derivatives Designated as Hedging Instruments: Interest rate swaps Fair value 1.7 2.3 — — Interest rate swaps Cash flow (0.1 ) (0.3 ) — (0.3 ) Interest rate locks (2) Cash flow — — — — Total 1.7 2.3 — — Total $ 4.6 $ 4.0 $ — $ — (1) Amounts recognized in earnings are recorded in interest income, interest expense or other non-interest non-interest (2) Income totaled less than $0.1 million for both periods.

Balance Sheet Offsetting (Table

Balance Sheet Offsetting (Tables)	3 Months Ended
	Mar. 31, 2017
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 Gross Net Gross Amounts Not Offset Net As of March 31, 2017 (in millions) Financial Collateral Financial assets: Interest rate swaps: Counterparty A $ 2.1 $ — $ 2.1 $ (2.1 ) $ — $ — Counterparty B 1.3 — 1.3 (1.3 ) — — Counterparty C 2.0 — 2.0 (2.0 ) — — Counterparty D 3.5 — 3.5 (3.5 ) — — Other counterparties 2.0 — 2.0 (0.3 ) (1.6 ) 0.1 Foreign exchange contracts 0.2 — 0.2 — — 0.2 Total $ 11.1 $ — $ 11.1 $ (9.2 ) $ (1.6 ) $ 0.3 Financial liabilities: Interest rate swaps: Counterparty A $ 3.7 $ — $ 3.7 $ (2.1 ) $ (1.6 ) $ — Counterparty B 7.0 — 7.0 (1.3 ) (5.7 ) — Counterparty C 3.5 — 3.5 (2.0 ) (1.5 ) — Counterparty D 6.2 — 6.2 (3.5 ) (2.5 ) 0.2 Other counterparties 1.4 — 1.4 (0.3 ) (1.1 ) — Foreign exchange contracts 0.1 — 0.1 — — 0.1 Total $ 21.9 $ — $ 21.9 $ (9.2 ) $ (12.4 ) $ 0.3 Gross Gross Net Gross Amounts Not Offset Net As of December 31, 2016 (in millions) Financial Collateral 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

General - Additional Informatio

General - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Affordable housing investments	$ 220.3		$ 195.2
Future contingent commitments	$ 99.9		$ 92.5
Amortization period	10 years
Amortization expense included in income tax expense	$ 4	$ 3

Securities and Short-Term Inv33

Securities and Short-Term Investments - Available-for-Sale and Held-to-Maturity Securities Gains (Losses) (Detail) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Investment Holdings [Line Items]
Amortized Cost	$ 3,808.8	$ 4,463.2
Gross Unrealized Gains	13.8	15.3
Gross Unrealized Losses	(50.5)	(68.6)
Fair Value	3,772.1	4,409.9
Held to maturity Securities, Amortized Cost	2,324	2,005.4
Securities held to maturity, Gross Unrealized Gains	40.6	33.9
Securities held to maturity, Gross Unrealized Losses	(25.1)	(26.7)
Total securities held to maturity, Fair Value	2,339.5	2,012.6
State and Municipal [Member]
Investment Holdings [Line Items]
Held to maturity Securities, Amortized Cost	1,663	1,499.1
Securities held to maturity, Gross Unrealized Gains	40.2	33.9
Securities held to maturity, Gross Unrealized Losses	(21.7)	(23.5)
Total securities held to maturity, Fair Value	1,681.5	1,509.5
GSE Residential Mortgage-Backed Securities and CMOs [Member]
Investment Holdings [Line Items]
Amortized Cost	2,976.5	3,573.1
Gross Unrealized Gains	13.5	15
Gross Unrealized Losses	(25.5)	(38.1)
Fair Value	2,964.5	3,550
Held to maturity Securities, Amortized Cost	648.8	500.8
Securities held to maturity, Gross Unrealized Gains	0.2
Securities held to maturity, Gross Unrealized Losses	(3.4)	(3.2)
Total securities held to maturity, Fair Value	645.6	497.6
Debt Securities [Member]
Investment Holdings [Line Items]
Amortized Cost	3,799.2	4,463
Gross Unrealized Gains	13.8	15.3
Gross Unrealized Losses	(49.8)	(68.6)
Fair Value	3,763.2	4,409.7
Equity Securities [Member]
Investment Holdings [Line Items]
Amortized Cost	9.6	0.2
Gross Unrealized Losses	(0.7)
Fair Value	8.9	0.2
U.S. Treasury and Agency [Member]
Investment Holdings [Line Items]
Amortized Cost	822.7	889.9
Gross Unrealized Gains	0.3	0.3
Gross Unrealized Losses	(24.3)	(30.5)
Fair Value	798.7	859.7
Corporate [Member]
Investment Holdings [Line Items]
Held to maturity Securities, Amortized Cost	10.7	4
Securities held to maturity, Gross Unrealized Gains	0.2
Total securities held to maturity, Fair Value	10.9	4
Other [Member]
Investment Holdings [Line Items]
Held to maturity Securities, Amortized Cost	1.5	1.5
Total securities held to maturity, Fair Value	$ 1.5	$ 1.5

Securities and Short-Term Inv34

Securities and Short-Term Investments - Available-for-Sale and Held-to-Maturity Securities Gains (Losses) (Parenthetical) (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2017USD ($)
Amortized Cost and Fair Value Debt Securities [Abstract]
Fair value of ownership interest exchanged	$ 10.8

Securities and Short-Term Inv35

Securities and Short-Term Investments - Additional Information (Detail)	3 Months Ended		12 Months Ended
	Mar. 31, 2017USD ($)SecuritiesSecurity	Mar. 31, 2016USD ($)	Dec. 31, 2016USD ($)
Investment [Line Items]
Security available for sale with a fair value pledged with collateral for public deposits	$ 1,910,000,000		$ 1,830,000,000
Number of securities available for sale | Security	123
Number of securities held to maturity | Securities	464
Total number of securities owned | Security	1,753
Percentage of securities available for sale	33.00%
Available for sale of securities gross unrealized losses	$ 50,500,000		68,600,000
Held to maturity securities gross unrealized losses	25,100,000
Impairment losses on securities recognized in earnings	0	$ 0
Amortized cost of mortgage-backed securities	3,799,200,000
Impairment of investments	$ 0
Federal Reserve Bank stock percentage	6.00%
Federal Reserve Bank of New York [Member]
Investment [Line Items]
Acquired shares of capital stock	$ 153,600,000		149,500,000
Interest-bearing deposits	$ 355,400,000		$ 169,800,000
Federal funds sold and yield	1.00%		0.75%
Maximum [Member]
Investment [Line Items]
Debt securities with unrealized losses	$ 100,000
State and Municipal [Member]
Investment [Line Items]
Held to maturity securities gross unrealized losses	$ 21,700,000		$ 23,500,000
Available for sale securities average maturity period	15 years
GSE Residential Mortgage-Backed Securities and CMOs [Member]
Investment [Line Items]
Available for sale of securities gross unrealized losses	$ 25,500,000		38,100,000
Held to maturity securities gross unrealized losses	$ 3,400,000		3,200,000
Available for sale securities average maturity period	12 years
Amortized cost of mortgage-backed securities	$ 2,976,500,000
U.S. Treasury and CMO Securities [Member]
Investment [Line Items]
Amortized cost of mortgage-backed securities	487,000,000
Gain (loss) on sales of Mortgage Backed Securities	15,700,000
FHLB of Boston [Member]
Investment [Line Items]
Acquired shares of capital stock	154,700,000		155,000,000
FHLB of New York [Member]
Investment [Line Items]
Acquired shares of capital stock	$ 11,300,000		$ 11,300,000

Securities and Short-Term Inv36

Securities and Short-Term Investments - Summary of Amortized Cost and Fair Value of Debt Securities Based on Remaining Period to Contractual Maturity (Detail) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Investment [Line Items]
Available for Sale, Amortized Cost, Within 1 year	$ 1
Available for Sale, Amortized Cost, After 1 but within 5 years	238.7
Available for Sale, Amortized Cost, After 5 but within 10 years	1,599.3
Available for Sale, Amortized Cost, After 10 years	1,960.2
Available for Sale, Amortized Cost, Total	3,799.2
Available for Sale, Fair Value, Within 1 year	1
Available for Sale, Fair Value, After 1 but within 5 years	235.7
Available for Sale, Fair Value, After 5 but within 10 years	1,590.3
Available for Sale, Fair Value, After 10 years	1,936.2
Available for Sale, Fair Value, Total	3,763.2
Held to Maturity, Amortized Cost, Within 1 year	5.7
Held to Maturity, Amortized Cost, After 1 but within 5 years	30.7
Held to Maturity, Amortized Cost, After 5 but within 10 years	535.4
Held to Maturity, Amortized Cost, After 10 years	1,752.2
Held to maturity Securities, Amortized Cost	2,324	$ 2,005.4
Held to Maturity, Fair Value, Within 1 year	5.7
Held to Maturity, Fair Value, After 1 but within 5 years	31.3
Held to Maturity, Fair Value, After 5 but within 10 years	553.9
Held to Maturity, Fair Value, After 10 years	1,748.6
Held to Maturity, Fair Value, Total	2,339.5	2,012.6
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	238.7
Available for Sale, Amortized Cost, After 5 but within 10 years	583
Available for Sale, Amortized Cost, Total	822.7
Available for Sale, Fair Value, Within 1 year	1
Available for Sale, Fair Value, After 1 but within 5 years	235.7
Available for Sale, Fair Value, After 5 but within 10 years	562
Available for Sale, Fair Value, Total	798.7
GSE Residential Mortgage-Backed Securities and CMOs [Member]
Investment [Line Items]
Available for Sale, Amortized Cost, After 5 but within 10 years	1,016.3
Available for Sale, Amortized Cost, After 10 years	1,960.2
Available for Sale, Amortized Cost, Total	2,976.5
Available for Sale, Fair Value, After 5 but within 10 years	1,028.3
Available for Sale, Fair Value, After 10 years	1,936.2
Available for Sale, Fair Value, Total	2,964.5
Held to Maturity, Amortized Cost, After 5 but within 10 years	166.6
Held to Maturity, Amortized Cost, After 10 years	482.2
Held to maturity Securities, Amortized Cost	648.8	500.8
Held to Maturity, Fair Value, After 5 but within 10 years	166.6
Held to Maturity, Fair Value, After 10 years	479
Held to Maturity, Fair Value, Total	645.6	497.6
State and Municipal [Member]
Investment [Line Items]
Held to Maturity, Amortized Cost, Within 1 year	4.2
Held to Maturity, Amortized Cost, After 1 but within 5 years	30.7
Held to Maturity, Amortized Cost, After 5 but within 10 years	363.1
Held to Maturity, Amortized Cost, After 10 years	1,265
Held to maturity Securities, Amortized Cost	1,663	1,499.1
Held to Maturity, Fair Value, Within 1 year	4.2
Held to Maturity, Fair Value, After 1 but within 5 years	31.3
Held to Maturity, Fair Value, After 5 but within 10 years	381.5
Held to Maturity, Fair Value, After 10 years	1,264.5
Held to Maturity, Fair Value, Total	1,681.5	1,509.5
Corporate [Member]
Investment [Line Items]
Held to Maturity, Amortized Cost, After 5 but within 10 years	5.7
Held to Maturity, Amortized Cost, After 10 years	5
Held to maturity Securities, Amortized Cost	10.7	4
Held to Maturity, Fair Value, After 5 but within 10 years	5.8
Held to Maturity, Fair Value, After 10 years	5.1
Held to Maturity, Fair Value, Total	10.9	4
Other [Member]
Investment [Line Items]
Held to Maturity, Amortized Cost, Within 1 year	1.5
Held to maturity Securities, Amortized Cost	1.5	1.5
Held to Maturity, Fair Value, Within 1 year	1.5
Held to Maturity, Fair Value, Total	$ 1.5	$ 1.5

Securities and Short-Term Inv37

Securities and Short-Term Investments - Continuous Unrealized Loss Position on Available-for-Sale and Held-to-Maturities Securities (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Continuous Unrealized Loss Position, Less Than 12 Months, Fair Value	$ 4,245.7	$ 4,247.2
Continuous Unrealized Loss Position, Less Than 12 Months, Unrealized Losses	(73.3)	(83.8)
Continuous Unrealized Loss Position, 12 Months Or Longer, Fair Value	62.1	396.9
Continuous Unrealized Loss Position, 12 Months Or Longer, Unrealized Losses	(2.3)	(11.5)
Continuous Unrealized Loss Position, Total, Fair Value	4,307.8	4,644.1
Continuous Unrealized Loss Position, Total, Unrealized Losses	(75.6)	(95.3)
Held To Maturity Securities, Continuous Unrealized Loss Position, Total, Unrealized Losses	(25.1)
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	553.1	497.6
Held To Maturity Securities, Continuous Unrealized Loss Position, Less Than 12 Months, Unrealized Losses	(3.4)	(3.2)
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	553.1	497.6
Held To Maturity Securities, Continuous Unrealized Loss Position, Total, Unrealized Losses	(3.4)	(3.2)
Available for Sale Securities, Continuous Unrealized Loss Position, Less Than 12 Months, Fair Value	2,315	2,339.6
Available for Sale Securities, Continuous Unrealized Loss Position, Less Than 12 Months, Unrealized Losses	(23.2)	(26.6)
Available for Sale Securities, Continuous Unrealized Loss Position, 12 Months Or Longer, Fair Value	62	396.9
Available for Sale Securities, Continuous Unrealized Loss Position, 12 Months Or Longer, Unrealized Losses	(2.3)	(11.5)
Available for Sale Securities, Continuous Unrealized Loss Position, Total, Fair Value	2,377	2,736.5
Available for Sale Securities, Continuous Unrealized Loss Position, Total, Unrealized Losses	(25.5)	(38.1)
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	768.4	828.3
Available for Sale Securities, Continuous Unrealized Loss Position, Less Than 12 Months, Unrealized Losses	(24.3)	(30.5)
Available for Sale Securities, Continuous Unrealized Loss Position, Total, Fair Value	768.4	828.3
Available for Sale Securities, Continuous Unrealized Loss Position, Total, Unrealized Losses	(24.3)	(30.5)
Equity Securities [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	8.9
Available for Sale Securities, Continuous Unrealized Loss Position, Less Than 12 Months, Unrealized Losses	(0.7)
Available for Sale Securities, Continuous Unrealized Loss Position, Total, Fair Value	8.9
Available for Sale Securities, Continuous Unrealized Loss Position, Total, Unrealized Losses	(0.7)
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	600.3	581.7
Held To Maturity Securities, Continuous Unrealized Loss Position, Less Than 12 Months, Unrealized Losses	(21.7)	(23.5)
Held To Maturity Securities, Continuous Unrealized Loss Position, 12 Months Or Longer, Fair Value	0.1
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	600.4	581.7
Held To Maturity Securities, Continuous Unrealized Loss Position, Total, Unrealized Losses	$ (21.7)	$ (23.5)

Loans - Additional Information

Loans - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2017USD ($)SegmentsRating	Mar. 31, 2016USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2011USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of segments | Segments	2
Net deferred loan costs	$ 72,300,000		$ 69,900,000
Recorded investments, non-performing loans	159,700,000		148,000,000
Accruing interest total	$ 0		0
Number of days of non accrual status	90 days
Allowance for loan losses	$ 231,300,000	$ 215,500,000	229,300,000	$ 211,000,000
Interest Income Recognized	$ 1,500,000	1,300,000
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	$ 241,700,000	280,800,000	255,400,000	296,000,000
Portfolio outstanding balance	676,300,000		707,000,000
Portfolio carrying value	578,500,000		610,200,000
Repossessed assets	8,200,000		7,200,000
Commercial Real Estate Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Early non-performing loans	14,800,000		10,500,000
Real estate owned	4,100,000		4,000,000
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Early non-performing loans	33,000,000		24,800,000
Equipment Financing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Early non-performing loans	35,100,000		28,400,000
Residential Mortgage Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Real estate owned	10,900,000		8,100,000
Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investments, non-performing loans	118,200,000		103,200,000
Allowance for loan losses	201,200,000	192,600,000	204,900,000	189,700,000
Interest Income Recognized	1,000,000	800,000
Commercial [Member] | Commercial Real Estate Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investments, non-performing loans	23,400,000		22,300,000
Interest Income Recognized	400,000	300,000
Commercial [Member] | Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investments, non-performing loans	47,400,000		41,500,000
Interest Income Recognized	500,000	400,000
Commercial [Member] | Equipment Financing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investments, non-performing loans	47,400,000		39,400,000
Interest Income Recognized	100,000	100,000
Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investments, non-performing loans	41,500,000		44,800,000
Allowance for loan losses	30,100,000	22,900,000	24,400,000	21,300,000
Interest Income Recognized	$ 500,000	500,000
Duration of extension for payment deferral on TDRs, years	5 years
Retail Loans [Member] | Residential Mortgage Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investments, non-performing loans	$ 26,300,000		27,400,000
Interest Income Recognized	$ 400,000	400,000
Maximum [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Duration of extension for payment deferral on TDRs, years	2 years
Minimum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan agreement	6 months
At Acquisition [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Portfolio accretable yield					$ 1,660,000,000
Acquired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	$ 6,300,000		6,300,000
Acquired Loans [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	6,100,000	7,700,000	6,100,000	7,900,000
Acquired Loans [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	200,000	200,000	200,000	$ 200,000
Purchased Credit Impaired Loans [Member] | Acquired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investments, non-performing loans	19,400,000		21,600,000
Covered by FDIC Loss-Share [Member] | Acquired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investments, non-performing loans	2,700,000		3,100,000
Troubled Debt Restructurings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment in originated loans classified as TDRs	196,700,000		189,900,000
Allowance for loan losses	4,600,000		4,200,000
Interest Income Recognized	1,300,000	$ 1,100,000
Foreclosure or Bankruptcy [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Early non-performing loans	$ 17,500,000		$ 17,600,000

Loans - Summary of Loans by Loa

Loans - Summary of Loans by Loan Portfolio Segment and Class (Detail) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 29,687.3	$ 29,744.9
Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	21,113.1	21,404.9
Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	8,574.2	8,340
Commercial Real Estate Loan [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	10,225.3	10,247.3
Commercial and Industrial [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	7,918.3	8,125.1
Equipment Financing [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,969.5	3,032.5
Residential Mortgage Adjustable Rate [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	5,790.2	5,549.1
Residential Mortgage Fixed Rate [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	697.5	667.6
Residential Mortgage Loan [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	6,487.7	6,216.7
Home Equity Loan [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,037.3	2,072.6
Other Consumer [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	49.2	50.7
Home Equity and Other Consumer [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,086.5	2,123.3
Originated [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	29,108.8	29,134.7
Originated [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	20,702.1	20,972.5
Originated [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	8,406.7	8,162.2
Originated [Member] | Commercial Real Estate Loan [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	10,001.2	10,012.6
Originated [Member] | Commercial and Industrial [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	7,737.9	7,939
Originated [Member] | Equipment Financing [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,963	3,020.9
Originated [Member] | Residential Mortgage Adjustable Rate [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	5,699.1	5,453.8
Originated [Member] | Residential Mortgage Fixed Rate [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	647.1	613.5
Originated [Member] | Residential Mortgage Loan [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	6,346.2	6,067.3
Originated [Member] | Home Equity Loan [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,012	2,044.9
Originated [Member] | Other Consumer [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	48.5	50
Originated [Member] | Home Equity and Other Consumer [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,060.5	2,094.9
Acquired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	578.5	610.2
Acquired Loans [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	411	432.4
Acquired Loans [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	167.5	177.8
Acquired Loans [Member] | Commercial Real Estate Loan [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	224.1	234.7
Acquired Loans [Member] | Commercial and Industrial [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	180.4	186.1
Acquired Loans [Member] | Equipment Financing [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	6.5	11.6
Acquired Loans [Member] | Residential Mortgage Adjustable Rate [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	91.1	95.3
Acquired Loans [Member] | Residential Mortgage Fixed Rate [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	50.4	54.1
Acquired Loans [Member] | Residential Mortgage Loan [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	141.5	149.4
Acquired Loans [Member] | Home Equity Loan [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	25.3	27.7
Acquired Loans [Member] | Other Consumer [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	0.7	0.7
Acquired Loans [Member] | Home Equity and Other Consumer [Member] | Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 26	$ 28.4

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
	Mar. 31, 2017	Mar. 31, 2016
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	$ 229.3	$ 211
Charge-offs	(4.6)	(7.7)
Recoveries	2.2	1.7
Net loan charge-offs	(2.4)	(6)
Provision for loan losses	4.4	10.5
Balance at end of period	231.3	215.5
Acquired Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	6.3
Balance at end of period	6.3
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	204.9	189.7
Charge-offs	(2.9)	(4.9)
Recoveries	1.6	0.4
Net loan charge-offs	(1.3)	(4.5)
Provision for loan losses	(2.4)	7.4
Balance at end of period	201.2	192.6
Commercial [Member] | Originated [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	198.8	181.8
Charge-offs	(2.9)	(4.6)
Recoveries	1.6	0.4
Net loan charge-offs	(1.3)	(4.2)
Provision for loan losses	(2.4)	7.3
Balance at end of period	195.1	184.9
Commercial [Member] | Acquired Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	6.1	7.9
Charge-offs		(0.3)
Net loan charge-offs		(0.3)
Provision for loan losses		0.1
Balance at end of period	6.1	7.7
Retail Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	24.4	21.3
Charge-offs	(1.7)	(2.8)
Recoveries	0.6	1.3
Net loan charge-offs	(1.1)	(1.5)
Provision for loan losses	6.8	3.1
Balance at end of period	30.1	22.9
Retail Loans [Member] | Originated [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	24.2	21.1
Charge-offs	(1.7)	(2.8)
Recoveries	0.6	1.3
Net loan charge-offs	(1.1)	(1.5)
Provision for loan losses	6.8	3.1
Balance at end of period	29.9	22.7
Retail Loans [Member] | Acquired Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	0.2	0.2
Balance at end of period	$ 0.2	$ 0.2

Loans - Summary of Allowance fo

Loans - Summary of Allowance for Loan Losses by Loan Portfolio Segment and Impairment Methodology (Detail) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Originated Loans Individually Evaluated for Impairment, Portfolio	$ 270.3	$ 253.6
Originated Loans Individually Evaluated for Impairment, Allowance	11.3	9
Originated Loans Collectively Evaluated for Impairment, Portfolio	28,838.5	28,881.1
Originated Loans Collectively Evaluated for Impairment, Allowance	213.7	214
Loans, Portfolio	29,687.3	29,744.9
Total Allowance	231.3	229.3	$ 215.5	$ 211
Receivables Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans, Portfolio	578.5	610.2
Total Allowance	6.3	6.3
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Originated Loans Individually Evaluated for Impairment, Portfolio	176.2	161.8
Originated Loans Individually Evaluated for Impairment, Allowance	8.1	5.8
Originated Loans Collectively Evaluated for Impairment, Portfolio	20,525.9	20,810.7
Originated Loans Collectively Evaluated for Impairment, Allowance	187	193
Loans, Portfolio	21,113.1	21,404.9
Total Allowance	201.2	204.9	192.6	189.7
Commercial [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans, Portfolio	411	432.4
Total Allowance	6.1	6.1
Retail Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Originated Loans Individually Evaluated for Impairment, Portfolio	94.1	91.8
Originated Loans Individually Evaluated for Impairment, Allowance	3.2	3.2
Originated Loans Collectively Evaluated for Impairment, Portfolio	8,312.6	8,070.4
Originated Loans Collectively Evaluated for Impairment, Allowance	26.7	21
Loans, Portfolio	8,574.2	8,340
Total Allowance	30.1	24.4	$ 22.9	$ 21.3
Retail Loans [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans, Portfolio	167.5	177.8
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	Mar. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investments, non-performing loans	$ 159.7	$ 148
Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investments, non-performing loans	118.2	103.2
Retail Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investments, non-performing loans	41.5	44.8
Commercial Real Estate Loan [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investments, non-performing loans	23.4	22.3
Commercial and Industrial [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investments, non-performing loans	47.4	41.5
Equipment Financing [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investments, non-performing loans	47.4	39.4
Residential Mortgage Loan [Member] | Retail Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investments, non-performing loans	26.3	27.4
Home Equity Loan [Member] | Retail Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investments, non-performing loans	$ 15.2	$ 17.4

Loans - Summarized Recorded I43

Loans - Summarized Recorded Investments, by Class of Loan, of Originated Non-Performing Loans (Parenthetical) (Detail) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Government guarantees	$ 4.4	$ 13.1
Recorded investments, non-performing loans	159.7	148
Foreclosure [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investments, non-performing loans	$ 11.8	$ 9.8
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	3 Months Ended
	Mar. 31, 2017USD ($)Contracts	Mar. 31, 2016USD ($)Contracts
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	64	64
Pre-Modification Outstanding Recorded Investment	$ 24.1	$ 19.3
Post-Modification Outstanding Recorded Investment	$ 24.1	$ 19.3
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	33	26
Pre-Modification Outstanding Recorded Investment	$ 18.1	$ 12.4
Post-Modification Outstanding Recorded Investment	$ 18.1	$ 12.4
Retail Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	31	38
Pre-Modification Outstanding Recorded Investment	$ 6	$ 6.9
Post-Modification Outstanding Recorded Investment	$ 6	$ 6.9
Commercial Real Estate Loan [Member] | Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	3	3
Pre-Modification Outstanding Recorded Investment	$ 3.9	$ 1.1
Post-Modification Outstanding Recorded Investment	$ 3.9	$ 1.1
Commercial and Industrial [Member] | Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	9	13
Pre-Modification Outstanding Recorded Investment	$ 8.3	$ 5.2
Post-Modification Outstanding Recorded Investment	$ 8.3	$ 5.2
Equipment Financing [Member] | Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	21	10
Pre-Modification Outstanding Recorded Investment	$ 5.9	$ 6.1
Post-Modification Outstanding Recorded Investment	$ 5.9	$ 6.1
Residential Mortgage Loan [Member] | Retail Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	7	19
Pre-Modification Outstanding Recorded Investment	$ 3.8	$ 5.3
Post-Modification Outstanding Recorded Investment	$ 3.8	$ 5.3
Home Equity Loan [Member] | Retail Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	24	19
Pre-Modification Outstanding Recorded Investment	$ 2.2	$ 1.6
Post-Modification Outstanding Recorded Investment	$ 2.2	$ 1.6

Loans - Summary of Recorded I45

Loans - Summary of Recorded Investments in TDRs by Class of Loan (Parenthetical) (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2017USD ($)Contracts	Mar. 31, 2016USD ($)Contracts
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	64	64
Recorded investment | $	$ 24.1	$ 19.3
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	33	26
Recorded investment | $	$ 18.1	$ 12.4
Commercial [Member] | Commercial Real Estate Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	3	3
Recorded investment | $	$ 3.9	$ 1.1
Commercial [Member] | Commercial and Industrial [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	9	13
Recorded investment | $	$ 8.3	$ 5.2
Commercial [Member] | Equipment Financing [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	21	10
Recorded investment | $	$ 5.9	$ 6.1
Commercial [Member] | Extended Maturity [Member] | Commercial Real Estate Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts		1
Recorded investment | $		$ 0.2
Commercial [Member] | Extended Maturity [Member] | Commercial and Industrial [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	8	7
Recorded investment | $	$ 7.4	$ 4.4
Commercial [Member] | Extended Maturity [Member] | Equipment Financing [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts		2
Recorded investment | $		$ 0.4
Commercial [Member] | Payment Deferral [Member] | Commercial Real Estate Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	2	1
Recorded investment | $	$ 2.2	$ 0.9
Commercial [Member] | Payment Deferral [Member] | Commercial and Industrial [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	1	3
Recorded investment | $	$ 0.9	$ 0.4
Commercial [Member] | Payment Deferral [Member] | Equipment Financing [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	7	5
Recorded investment | $	$ 2.3	$ 4.3
Commercial [Member] | Combination of Concessions [Member] | Commercial Real Estate Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts		1
Recorded investment | $		$ 0.1
Commercial [Member] | Combination of Concessions [Member] | Commercial and Industrial [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts		3
Recorded investment | $		$ 0.4
Commercial [Member] | Combination of Concessions [Member] | Equipment Financing [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	14	3
Recorded investment | $	$ 3.6	$ 1.4
Commercial [Member] | Temporary Rate Reduction [Member] | Commercial Real Estate Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	1
Recorded investment | $	$ 1.7
Retail Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	31	38
Recorded investment | $	$ 6	$ 6.9
Retail Loans [Member] | Residential Mortgage Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	7	19
Recorded investment | $	$ 3.8	$ 5.3
Retail Loans [Member] | Home Equity Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	24	19
Recorded investment | $	$ 2.2	$ 1.6
Retail Loans [Member] | Payment Deferral [Member] | Residential Mortgage Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	4	5
Recorded investment | $	$ 1.3	$ 1.4
Retail Loans [Member] | Payment Deferral [Member] | Home Equity Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	4	1
Recorded investment | $	$ 0.3	$ 0.1
Retail Loans [Member] | Combination of Concessions [Member] | Residential Mortgage Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	2	10
Recorded investment | $	$ 2.4	$ 2.4
Retail Loans [Member] | Combination of Concessions [Member] | Home Equity Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	6	4
Recorded investment | $	$ 0.8	$ 0.2
Retail Loans [Member] | Bankruptcy [Member] | Residential Mortgage Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	1	4
Recorded investment | $	$ 0.1	$ 1.5
Retail Loans [Member] | Bankruptcy [Member] | Home Equity Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	14	14
Recorded investment | $	$ 1.1	$ 1.3

Loans - Summary of Recorded I46

Loans - Summary of Recorded Investments in TDRs by Class of Loan, Subsequently Defaulted (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2017USD ($)Contracts	Mar. 31, 2016USD ($)Contracts
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	19	20
Recorded Investment | $	$ 8.3	$ 4.9
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	11	7
Recorded Investment | $	$ 5.7	$ 3.1
Commercial [Member] | Commercial Real Estate Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	1
Recorded Investment | $	$ 1.7
Commercial [Member] | Commercial and Industrial [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	2	2
Recorded Investment | $	$ 1.4	$ 0.6
Commercial [Member] | Equipment Financing [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	8	5
Recorded Investment | $	$ 2.6	$ 2.5
Retail Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	8	13
Recorded Investment | $	$ 2.6	$ 1.8
Retail Loans [Member] | Residential Mortgage Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	7	6
Recorded Investment | $	$ 2.5	$ 1.3
Retail Loans [Member] | Home Equity Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contracts	1	7
Recorded Investment | $	$ 0.1	$ 0.5

Loans - Summary of Individually

Loans - Summary of Individually-Evaluated Impaired Loans by Class of Loan (Detail) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Financing Receivable, Impaired [Line Items]
With no related allowance for loan losses, Unpaid Principal Balance	$ 221.4	$ 216.3
With no related allowance for loan losses, Recorded Investment	204.6	197.7
With a related allowance for loan losses, Unpaid Principal Balance	67.8	58.3
With a related allowance for loan losses, Recorded Investment	65.7	55.9
Unpaid Principal Balance	289.2	274.6
Recorded Investment	270.3	253.6
Related Allowance for Loan Losses	11.3	9
Commercial [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	185.5	173.4
Recorded Investment	176.2	161.8
Related Allowance for Loan Losses	8.1	5.8
Commercial [Member] | Commercial Real Estate Loan [Member]
Financing Receivable, Impaired [Line Items]
With no related allowance for loan losses, Unpaid Principal Balance	49	41.4
With no related allowance for loan losses, Recorded Investment	47.4	40
With a related allowance for loan losses, Unpaid Principal Balance	8.5	12.2
With a related allowance for loan losses, Recorded Investment	8.3	11.4
Unpaid Principal Balance	57.5	53.6
Recorded Investment	55.7	51.4
Related Allowance for Loan Losses	0.4	0.6
Commercial [Member] | Commercial and Industrial [Member]
Financing Receivable, Impaired [Line Items]
With no related allowance for loan losses, Unpaid Principal Balance	42.6	50.7
With no related allowance for loan losses, Recorded Investment	40.7	45.7
With a related allowance for loan losses, Unpaid Principal Balance	33.5	25.9
With a related allowance for loan losses, Recorded Investment	32.6	25
Unpaid Principal Balance	76.1	76.6
Recorded Investment	73.3	70.7
Related Allowance for Loan Losses	6.1	4.7
Commercial [Member] | Equipment Financing [Member]
Financing Receivable, Impaired [Line Items]
With no related allowance for loan losses, Unpaid Principal Balance	41	38.2
With no related allowance for loan losses, Recorded Investment	37.3	35.3
With a related allowance for loan losses, Unpaid Principal Balance	10.9	5
With a related allowance for loan losses, Recorded Investment	9.9	4.4
Unpaid Principal Balance	51.9	43.2
Recorded Investment	47.2	39.7
Related Allowance for Loan Losses	1.6	0.5
Retail Loans [Member]
Financing Receivable, Impaired [Line Items]
With a related allowance for loan losses, Recorded Investment	14.9
Unpaid Principal Balance	103.7	101.2
Recorded Investment	94.1	91.8
Related Allowance for Loan Losses	3.2	3.2
Retail Loans [Member] | Residential Mortgage Loan [Member]
Financing Receivable, Impaired [Line Items]
With no related allowance for loan losses, Unpaid Principal Balance	66.6	63.6
With no related allowance for loan losses, Recorded Investment	60.7	58
With a related allowance for loan losses, Unpaid Principal Balance	12.5	13.1
With a related allowance for loan losses, Recorded Investment	12.5	13.1
Unpaid Principal Balance	79.1	76.7
Recorded Investment	73.2	71.1
Related Allowance for Loan Losses	2.2	2.3
Retail Loans [Member] | Home Equity Loan [Member]
Financing Receivable, Impaired [Line Items]
With no related allowance for loan losses, Unpaid Principal Balance	22.2	22.4
With no related allowance for loan losses, Recorded Investment	18.5	18.7
With a related allowance for loan losses, Unpaid Principal Balance	2.4	2.1
With a related allowance for loan losses, Recorded Investment	2.4	2
Unpaid Principal Balance	24.6	24.5
Recorded Investment	20.9	20.7
Related Allowance for Loan Losses	$ 1	$ 0.9

Loans - Schedule of Impaired Fi

Loans - Schedule of Impaired Financing Receivable (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	$ 253.3	$ 250.9
Interest Income Recognized	1.5	1.3
Commercial [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	161.7	156.3
Interest Income Recognized	1	0.8
Commercial [Member] | Commercial Real Estate Loan [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	51.9	60.2
Interest Income Recognized	0.4	0.3
Commercial [Member] | Commercial and Industrial [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	70	63
Interest Income Recognized	0.5	0.4
Commercial [Member] | Equipment Financing [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	39.8	33.1
Interest Income Recognized	0.1	0.1
Retail Loans [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	91.6	94.6
Interest Income Recognized	0.5	0.5
Retail Loans [Member] | Residential Mortgage Loan [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	71.2	72.2
Interest Income Recognized	0.4	0.4
Retail Loans [Member] | Home Equity Loan [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	20.4	22.4
Interest Income Recognized	$ 0.1	$ 0.1

Loans - Summary of Aging Inform

Loans - Summary of Aging Information by Class of Loan (Detail) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	$ 29,687.3	$ 29,744.9
Originated [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	28,913.6	28,938.1
Total Past Due	195.2	196.6
Total loans	29,108.8	29,134.7
Originated [Member] | 30-89 Days [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	131.5	116.8
Originated [Member] | 90 Days or More [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	63.7	79.8
Retail Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	8,574.2	8,340
Retail Loans [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	49.2	50.7
Retail Loans [Member] | Home Equity Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	2,037.3	2,072.6
Retail Loans [Member] | Residential Mortgage Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	6,487.7	6,216.7
Retail Loans [Member] | Originated [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	8,352.6	8,107.5
Total Past Due	54.1	54.7
Total loans	8,406.7	8,162.2
Retail Loans [Member] | Originated [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	48.3	49.7
Total Past Due	0.2	0.3
Total loans	48.5	50
Retail Loans [Member] | Originated [Member] | Home Equity Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	1,999.5	2,030.3
Total Past Due	12.5	14.6
Total loans	2,012	2,044.9
Retail Loans [Member] | Originated [Member] | Residential Mortgage Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	6,304.8	6,027.5
Total Past Due	41.4	39.8
Total loans	6,346.2	6,067.3
Retail Loans [Member] | Originated [Member] | 30-89 Days [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	30.1	27.5
Retail Loans [Member] | Originated [Member] | 30-89 Days [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0.2	0.3
Retail Loans [Member] | Originated [Member] | 30-89 Days [Member] | Home Equity Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	5.6	5.2
Retail Loans [Member] | Originated [Member] | 30-89 Days [Member] | Residential Mortgage Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	24.3	22
Retail Loans [Member] | Originated [Member] | 90 Days or More [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	24	27.2
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	6.9	9.4
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	17.1	17.8
Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	21,113.1	21,404.9
Commercial [Member] | Commercial Real Estate Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	10,225.3	10,247.3
Commercial [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	7,918.3	8,125.1
Commercial [Member] | Equipment Financing [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	2,969.5	3,032.5
Commercial [Member] | Originated [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	20,561	20,830.6
Total Past Due	141.1	141.9
Total loans	20,702.1	20,972.5
Commercial [Member] | Originated [Member] | Commercial Real Estate Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	9,979.5	9,989.9
Total Past Due	21.7	22.7
Total loans	10,001.2	10,012.6
Commercial [Member] | Originated [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	7,700.8	7,899.2
Total Past Due	37.1	39.8
Total loans	7,737.9	7,939
Commercial [Member] | Originated [Member] | Equipment Financing [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	2,880.7	2,941.5
Total Past Due	82.3	79.4
Total loans	2,963	3,020.9
Commercial [Member] | Originated [Member] | 30-89 Days [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	101.4	89.3
Commercial [Member] | Originated [Member] | 30-89 Days [Member] | Commercial Real Estate Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	13.1	10.9
Commercial [Member] | Originated [Member] | 30-89 Days [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	18.3	10
Commercial [Member] | Originated [Member] | 30-89 Days [Member] | Equipment Financing [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	70	68.4
Commercial [Member] | Originated [Member] | 90 Days or More [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	39.7	52.6
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	8.6	11.8
Commercial [Member] | Originated [Member] | 90 Days or More [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	18.8	29.8
Commercial [Member] | Originated [Member] | 90 Days or More [Member] | Equipment Financing [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 12.3	$ 11

Loans - Summary of Credit Quali

Loans - Summary of Credit Quality Indicators by Class of Loan (Detail) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	$ 29,687.3	$ 29,744.9
Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	21,113.1	21,404.9
Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	8,574.2	8,340
Originated Loans [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	20,702.1	20,972.5
Originated Loans [Member] | Commercial [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	19,723	20,015.7
Originated Loans [Member] | Commercial [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	331.5	328
Originated Loans [Member] | Commercial [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	645.6	624.6
Originated Loans [Member] | Commercial [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	2	4.2
Originated Loans [Member] | Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	8,406.7	8,162.2
Originated Loans [Member] | Retail Loans [Member] | Low Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	4,165.1	3,998.4
Originated Loans [Member] | Retail Loans [Member] | Moderate Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	3,299.4	3,210
Originated Loans [Member] | Retail Loans [Member] | High Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	942.2	953.8
Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	578.5	610.2
Acquired Loans [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	411	432.4
Acquired Loans [Member] | Commercial [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	330.3	339.4
Acquired Loans [Member] | Commercial [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	16.5	25.7
Acquired Loans [Member] | Commercial [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	63.5	66.6
Acquired Loans [Member] | Commercial [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	0.7	0.7
Acquired Loans [Member] | Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	167.5	177.8
Acquired Loans [Member] | Retail Loans [Member] | Low Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	69.2	75.7
Acquired Loans [Member] | Retail Loans [Member] | Moderate Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	31	27.5
Acquired Loans [Member] | Retail Loans [Member] | High Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	67.3	74.6
Commercial Real Estate Loan [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	10,225.3	10,247.3
Commercial Real Estate Loan [Member] | Originated Loans [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	10,001.2	10,012.6
Commercial Real Estate Loan [Member] | Originated Loans [Member] | Commercial [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	9,788.5	9,817.2
Commercial Real Estate Loan [Member] | Originated Loans [Member] | Commercial [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	117.2	107.3
Commercial Real Estate Loan [Member] | Originated Loans [Member] | Commercial [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	94.6	87.1
Commercial Real Estate Loan [Member] | Originated Loans [Member] | Commercial [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	0.9	1
Commercial Real Estate Loan [Member] | Acquired Loans [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	224.1	234.7
Commercial Real Estate Loan [Member] | Acquired Loans [Member] | Commercial [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	180.9	182.9
Commercial Real Estate Loan [Member] | Acquired Loans [Member] | Commercial [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	8	13.5
Commercial Real Estate Loan [Member] | Acquired Loans [Member] | Commercial [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	34.5	37.6
Commercial Real Estate Loan [Member] | Acquired Loans [Member] | Commercial [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	0.7	0.7
Commercial and Industrial [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	7,918.3	8,125.1
Commercial and Industrial [Member] | Originated Loans [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	7,737.9	7,939
Commercial and Industrial [Member] | Originated Loans [Member] | Commercial [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	7,380.5	7,580.6
Commercial and Industrial [Member] | Originated Loans [Member] | Commercial [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	115.8	121.9
Commercial and Industrial [Member] | Originated Loans [Member] | Commercial [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	240.5	233.3
Commercial and Industrial [Member] | Originated Loans [Member] | Commercial [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	1.1	3.2
Commercial and Industrial [Member] | Acquired Loans [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	180.4	186.1
Commercial and Industrial [Member] | Acquired Loans [Member] | Commercial [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	149.4	155.5
Commercial and Industrial [Member] | Acquired Loans [Member] | Commercial [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	3.5	3.6
Commercial and Industrial [Member] | Acquired Loans [Member] | Commercial [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	27.5	27
Equipment Financing [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	2,969.5	3,032.5
Equipment Financing [Member] | Originated Loans [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	2,963	3,020.9
Equipment Financing [Member] | Originated Loans [Member] | Commercial [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	2,554	2,617.9
Equipment Financing [Member] | Originated Loans [Member] | Commercial [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	98.5	98.8
Equipment Financing [Member] | Originated Loans [Member] | Commercial [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	310.5	304.2
Equipment Financing [Member] | Acquired Loans [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	6.5	11.6
Equipment Financing [Member] | Acquired Loans [Member] | Commercial [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable		1
Equipment Financing [Member] | Acquired Loans [Member] | Commercial [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	5	8.6
Equipment Financing [Member] | Acquired Loans [Member] | Commercial [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	1.5	2
Residential Mortgage Loan [Member] | Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	6,487.7	6,216.7
Residential Mortgage Loan [Member] | Originated Loans [Member] | Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	6,346.2	6,067.3
Residential Mortgage Loan [Member] | Originated Loans [Member] | Retail Loans [Member] | Low Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	3,198.8	3,016.4
Residential Mortgage Loan [Member] | Originated Loans [Member] | Retail Loans [Member] | Moderate Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	2,642.2	2,538.9
Residential Mortgage Loan [Member] | Originated Loans [Member] | Retail Loans [Member] | High Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	505.2	512
Residential Mortgage Loan [Member] | Acquired Loans [Member] | Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	141.5	149.4
Residential Mortgage Loan [Member] | Acquired Loans [Member] | Retail Loans [Member] | Low Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	69.2	75.7
Residential Mortgage Loan [Member] | Acquired Loans [Member] | Retail Loans [Member] | Moderate Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	31	27.5
Residential Mortgage Loan [Member] | Acquired Loans [Member] | Retail Loans [Member] | High Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	41.3	46.2
Home Equity Loan [Member] | Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	2,037.3	2,072.6
Home Equity Loan [Member] | Originated Loans [Member] | Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	2,012	2,044.9
Home Equity Loan [Member] | Originated Loans [Member] | Retail Loans [Member] | Low Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	935.4	950.9
Home Equity Loan [Member] | Originated Loans [Member] | Retail Loans [Member] | Moderate Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	650.5	663.9
Home Equity Loan [Member] | Originated Loans [Member] | Retail Loans [Member] | High Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	426.1	430.1
Home Equity Loan [Member] | Acquired Loans [Member] | Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	25.3	27.7
Home Equity Loan [Member] | Acquired Loans [Member] | Retail Loans [Member] | High Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	25.3	27.7
Other Consumer [Member] | Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	49.2	50.7
Other Consumer [Member] | Originated Loans [Member] | Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	48.5	50
Other Consumer [Member] | Originated Loans [Member] | Retail Loans [Member] | Low Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	30.9	31.1
Other Consumer [Member] | Originated Loans [Member] | Retail Loans [Member] | Moderate Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	6.7	7.2
Other Consumer [Member] | Originated Loans [Member] | Retail Loans [Member] | High Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	10.9	11.7
Other Consumer [Member] | Acquired Loans [Member] | Retail Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	0.7	0.7
Other Consumer [Member] | Acquired Loans [Member] | Retail Loans [Member] | High Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	$ 0.7	$ 0.7

Loans - Summarized Activity in

Loans - Summarized Activity in Accretable Yield for Acquired Loan Portfolio (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Receivables [Abstract]
Balance at beginning of period	$ 255.4	$ 296
Accretion	(7.6)	(11.6)
Reclassification from nonaccretable difference for loans with improved cash flows	0	0
Other changes in expected cash flows	(6.1)	(3.6)
Balance at end of period	$ 241.7	$ 280.8

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - $ / shares	Mar. 31, 2017	Dec. 31, 2016
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	406,400,000	405,000,000
Preferred stock, shares outstanding	10,000,000	10,000,000
Number of common stock purchased	89,000,000	89,100,000
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	2,600,000	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
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	406,400,000	405,000,000
Preferred stock, shares outstanding	10,000,000	10,000,000

Stockholders' Equity - Schedule

Stockholders' Equity - Schedule of Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 5,141.9	$ 4,731.6
Amounts reclassified from AOCL	11.5	1.7
Total other comprehensive income , net of tax	13.1	42.5
Ending Balance	5,195	4,791.2
Pension and Other Postretirement Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(145.6)	(140)
Amounts reclassified from AOCL	1	1
Total other comprehensive income , net of tax	1	1
Ending Balance	(144.6)	(139)
Net Unrealized Gains (Losses) on Securities Available for Sale [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(32.3)	(17.7)
Other comprehensive income (loss) before reclassifications	1.4	41
Amounts reclassified from AOCL	9.9
Total other comprehensive income , net of tax	11.3	41
Ending Balance	(21)	23.3
Net Unrealized Gain (Losses) On Securities Transferred To Held To Maturity [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(17.4)	(19.5)
Amounts reclassified from AOCL	0.5	0.5
Total other comprehensive income , net of tax	0.5	0.5
Ending Balance	(16.9)	(19)
Net Unrealized Gains (Losses) on Derivatives Accounted for as Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	0.3
Other comprehensive income (loss) before reclassifications	0.2	(0.2)
Amounts reclassified from AOCL	0.1	0.2
Total other comprehensive income , net of tax	0.3
Ending Balance	0.6
Accumulated Other Comprehensive Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(195)	(177.2)
Other comprehensive income (loss) before reclassifications	1.6	40.8
Amounts reclassified from AOCL	11.5	1.7
Total other comprehensive income , net of tax	13.1	42.5
Ending Balance	$ (181.9)	$ (134.7)

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Amounts Reclassified from AOCL (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income before income tax expense	$ (102.8)	$ (94.6)
Income tax expense	32	31.7
Net income	(70.8)	(62.9)
Interest expense - notes and debentures	7.5	7.7
Total reclassifications for the period	(11.5)	(1.7)
Pension and Other Postretirement Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net actuarial loss	(1.7)	(1.6)
Prior service credit	0.2	0.2
Income before income tax expense	(1.5)	(1.4)
Income tax expense	0.5	0.4
Net income	(1)	(1)
Total reclassifications for the period	(1)	(1)
Net Unrealized Gains (Losses) on Securities Available for Sale [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income before income tax expense	(15.7)
Income tax expense	5.8
Net income	(9.9)
Total reclassifications for the period	(9.9)
Net Unrealized Gain (Losses) On Securities Transferred To Held To Maturity [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income before income tax expense	(0.8)	(0.8)
Income tax expense	0.3	0.3
Net income	(0.5)	(0.5)
Total reclassifications for the period	(0.5)	(0.5)
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	(0.1)	(0.3)
Income tax expense		0.1
Net income	(0.1)	(0.2)
Total reclassifications for the period	(0.1)	(0.2)
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	$ 0.1	$ 0.3

Stockholders' Equity - Summar55

Stockholders' Equity - Summary of Amounts Reclassified from AOCL (Parenthetical) (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amount Reclassified from accumulated other comprehensive loss	$ 7,500,000	$ 7,700,000
Interest Rate Locks [Member] | Maximum [Member] | Net Unrealized Gains (Losses) on Derivatives Accounted for as Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amount Reclassified from accumulated other comprehensive loss	$ 100,000	$ 100,000

Earnings Per Common Share - Bas

Earnings Per Common Share - Basic and Diluted Earnings Per Common Share, Reflecting Application of Two-Class Method (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Earnings Per Share [Abstract]
Net income available to common shareholders	$ 67.3	$ 62.9
Dividends paid on and undistributed earnings allocated to participating securities	(0.2)	(0.2)
Earnings attributable to common shareholders	$ 67.1	$ 62.7
Weighted average common shares outstanding for basic EPS	308.8	301.9
Effect of dilutive equity-based awards	2.3
Weighted average common and common-equivalent shares for diluted EPS	311.1	301.9
Basic EPS	$ 0.22	$ 0.21
Diluted EPS	$ 0.22	$ 0.21

Earnings Per Common Share - Add

Earnings Per Common Share - Additional Information (Detail) - shares shares in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Earnings Per Share [Abstract]
Anti-dilutive equity-based awards excluded from calculation of diluted EPS	9.8	22.4

Goodwill and Other Acquisitio58

Goodwill and Other Acquisition-Related Intangible Assets - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Goodwill And Other Intangible Assets [Line Items]
Goodwill	$ 1,992,700,000		$ 1,992,700,000
Tax deductible goodwill amount	76,300,000		77,900,000
Other acquisition-related intangible assets	143,100,000		149,400,000
Amortization of other acquisition-related intangible assets	6,300,000	$ 5,800,000
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
Amortization expense attributable to other acquisition-related intangible assets, 2022	11,100,000
Impairment losses relating to goodwill or other acquisition-related intangible assets	0	$ 0
Commercial Banking Loan [Member]
Goodwill And Other Intangible Assets [Line Items]
Goodwill	1,220,000,000		1,220,000,000
Retail Banking [Member]
Goodwill And Other Intangible Assets [Line Items]
Goodwill	679,600,000		679,600,000
Wealth Management [Member]
Goodwill And Other Intangible Assets [Line Items]
Goodwill	91,000,000		$ 91,000,000
Mutual Fund Management Contracts [Member]
Goodwill And Other Intangible Assets [Line Items]
Mutual fund management contracts (not amortized)	16,500,000
Trade Name [Member]
Goodwill And Other Intangible Assets [Line Items]
Other acquisition-related intangible assets	70,800,000
Customer Relationships [Member]
Goodwill And Other Intangible Assets [Line Items]
Other acquisition-related intangible assets	16,400,000
Core Deposit Intangibles [Member]
Goodwill And Other Intangible Assets [Line Items]
Other acquisition-related intangible assets	9,000,000
Insurance Relationships [Member]
Goodwill And Other Intangible Assets [Line Items]
Other acquisition-related intangible assets	5,900,000
Client Relationship [Member]
Goodwill And Other Intangible Assets [Line Items]
Other acquisition-related intangible assets	23,500,000
Favorable Lease Agreement [Member]
Goodwill And Other Intangible Assets [Line Items]
Other acquisition-related intangible assets	600,000
Noncompete Agreements [Member]
Goodwill And Other Intangible Assets [Line Items]
Other acquisition-related intangible assets	$ 400,000

Employee Benefit Plans - People

Employee Benefit Plans - People's United Employee Pension and Other Postretirement Plans - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2017
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
People's Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of covered employee's eligible compensation	3.00%

Employee Benefit Plans - Compon

Employee Benefit Plans - Components of Net Periodic Benefit (Income) Expense and Other Amounts (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Other Postretirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0.1	$ 0.1
Interest cost	0.1	0.1
Recognized net actuarial loss	0.1	0.1
Net periodic benefit (income) expense	0.3	0.3
Net actuarial loss	(0.1)	(0.1)
Total pre-tax changes recognized in other comprehensive income	(0.1)	(0.1)
Total recognized in net periodic benefit (income) expense and other comprehensive income	0.2	0.2
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	4.5	4.7
Expected return on plan assets	(8.9)	(8.6)
Recognized net actuarial loss	1.6	1.5
Recognized prior service credit	(0.2)	(0.2)
Settlements	0.4	0.3
Net periodic benefit (income) expense	(2.6)	(2.3)
Net actuarial loss	(1.6)	(1.5)
Prior service credit	0.2	0.2
Total pre-tax changes recognized in other comprehensive income	(1.4)	(1.3)
Total recognized in net periodic benefit (income) expense and other comprehensive income	$ (4)	$ (3.6)

Employee Benefit Plans - Employ

Employee Benefit Plans - Employee Stock Ownership Plan - Additional Information (Detail) - USD ($) $ in Millions	Apr. 30, 2007	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
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		$ 1.2
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		3,571,639
Unallocated common stock of Employee Stock Ownership Plan, shares		6,881,936		7,000,000
Fair value of deferred ESOP shares		$ 125.3
ESOP compensation expense		$ 1.7	$ 1.3

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
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	Mar. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account securities	$ 7.8	$ 6.8
Securities available for sale, at fair value	3,772.1	4,409.9
Other assets	836	967.2
Fair Values, Assets	97.1	174
Fair Values, Liabilities	73.7	121.7
Fair value of total assets measured at fair value on a recurring basis	3,987.7	4,630.3
Fair value of total liabilities measured at fair value on a recurring basis	117.8	121.7
Exchange Traded Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	31.6	32.6
Fixed Income Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	3.6	4.3
Equity Mutual Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	3.1	2.7
US Treasury [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account securities	7.8	6.8
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	798.7	859.7
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	2,964.5	3,550
Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	8.9	0.2
Interest Rate Swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Values, Assets	168.6	173.1
Fair Values, Liabilities	116.8	121
Foreign Exchange Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Values, Assets	0.2	0.6
Fair Values, Liabilities	0.1	0.3
Forward Commitments to Sell Residential Mortgage Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Values, Assets	0.7	0.3
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	0.9	0.4
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	850.1	901.8
Level 1 [Member] | Exchange Traded Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	31.6	32.6
Level 1 [Member] | Equity Mutual Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	3.1	2.7
Level 1 [Member] | US Treasury [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading account securities	7.8	6.8
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	798.7	859.7
Level 1 [Member] | Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at fair value	8.9
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	3,065.2	3,728.5
Fair value of total liabilities measured at fair value on a recurring basis	73.7	121.7
Level 2 [Member] | Fixed Income Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	3.6	4.3
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	2,964.5	3,550
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
Level 2 [Member] | Interest Rate Swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Values, Assets	96.2	173.1
Fair Values, Liabilities	72.7	121
Level 2 [Member] | Foreign Exchange Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Values, Assets	0.2	0.6
Fair Values, Liabilities	0.1	0.3
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	0.7	0.3
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	$ 0.9	$ 0.4

Fair Value Measurements - Ass64

Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Recurring Basis (Parenthetical) (Detail) - USD ($)	Mar. 31, 2017	Dec. 31, 2016
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 - Ass65

Fair Value Measurements - Assets Measured at Fair Value on Non-Recurring Basis (Detail) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale	$ 17.1	$ 39.3
Impaired loans	65.7	55.9
REO and repossessed assets	23.2	19.3
Total assets measured at fair value on non-recurring basis	106	114.5
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale	17.1	39.3
Total assets measured at fair value on non-recurring basis	17.1	39.3
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	65.7	55.9
REO and repossessed assets	23.2	19.3
Total assets measured at fair value on non-recurring basis	$ 88.9	$ 75.2

Fair Value Measurements - Ass66

Fair Value Measurements - Assets Measured at Fair Value on Non-Recurring Basis (Parenthetical) (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	$ 65,700,000		$ 55,900,000
Charge-offs to the allowance for loan losses related to loans	4,400,000	$ 10,500,000
Repossessed assets	8,200,000		7,200,000
Write downs and net loss on sale of foreclosed/repossessed assets charged to non-interest expense total	226,100,000	217,300,000
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	900,000	1,000,000
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	10,900,000		8,100,000
Commercial Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	50,800,000
Commercial Real Estate Loan [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Real estate owned	4,100,000		4,000,000
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	3,500,000	2,200,000
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	400,000	900,000
Retail Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	14,900,000
Charge-offs to the allowance for loan losses related to loans	6,800,000	$ 3,100,000
Retail Loans [Member] | Residential Mortgage Loan [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	$ 12,500,000		$ 13,100,000

Fair Value Measurements - Carry

Fair Value Measurements - Carrying Amounts and Estimated Fair Values of Financial Instruments (Detail) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	$ 380.8	$ 432.4
Short-term investments	392.2	181.7
Securities held to maturity	2,324	2,005.4
FHLB and FRB stock	319.6	315.8
Time deposits	4,570.6	4,542.2
FHLB advances	2,160.4	3,061.1
Federal funds purchased	613	617
Customer repurchase agreements	327.7	343.3
Other borrowings	81.9	35.4
Notes and debentures	903.9	1,030.1
Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	380.8	432.4
Short-term investments	392.2	181.7
Securities held to maturity	2,324	2,005.4
FHLB and FRB stock	319.6	315.8
Total loans, net	29,390.3	29,459.7
Time deposits	4,570.6	4,542.2
Other deposits	25,935.1	25,318.6
FHLB advances	2,160.4	3,061.1
Federal funds purchased	613	617
Customer repurchase agreements	327.7	343.3
Other borrowings	81.9	35.4
Notes and debentures	903.9	1,030.1
Estimated Fair Value Measurements [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	380.8	432.4
Short-term investments	392.2	181.7
Securities held to maturity	2,339.5	2,012.7
FHLB and FRB stock	319.6	315.8
Total loans, net	29,189.7	29,266.5
Time deposits	4,564.7	4,539.7
Other deposits	25,935.1	25,318.6
FHLB advances	2,162.6	3,064.4
Federal funds purchased	613	617
Customer repurchase agreements	327.7	343.3
Other borrowings	81.9	35.4
Notes and debentures	883	1,000
Estimated Fair Value Measurements [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	380.8	432.4
Estimated Fair Value Measurements [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	392.2	181.7
Securities held to maturity	2,338	2,011.2
FHLB and FRB stock	319.6	315.8
Total loans, net	6,310	6,028.4
Time deposits	4,564.7	4,539.7
Other deposits	25,935.1	25,318.6
FHLB advances	2,162.6	3,064.4
Federal funds purchased	613	617
Customer repurchase agreements	327.7	343.3
Other borrowings	81.9	35.4
Notes and debentures	883	1,000
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	$ 22,879.7	$ 23,238.1

Fair Value Measurements - Car68

Fair Value Measurements - Carrying Amounts and Estimated Fair Values of Financial Instruments (Parenthetical) (Detail) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Impaired loans	$ 65.7	$ 55.9

Derivative Financial Instrume69

Derivative Financial Instruments and Hedging Activities - Additional Information (Detail) - USD ($)	Feb. 14, 2017	Mar. 31, 2017
Derivative [Line Items]
Aggregate fair value of derivative instruments		$ 0
Subordinated notes fixed interest rate		5.80%
Repayment of subordinated notes		$ 125,000,000
5.80% Fixed Rate/Floating Rate Subordinated Notes Due 2017 [Member] | People's United Financial, Inc. [Member]
Derivative [Line Items]
Repayment of subordinated notes	$ 125,000,000
Interest Rate Swaps [Member] | Fair Value [Member]
Derivative [Line Items]
LIBOR basis points		Three-month LIBOR
Notional amount of derivatives		$ 375,000,000
Subordinated notes		$ 400,000,000
Basis points		1.265%
Interest Rate Swaps [Member] | Cash Flow [Member]
Derivative [Line Items]
Subordinated notes		$ 125,000,000
Interest Rate Swaps [Member] | Cash Flow [Member] | Loans [Member]
Derivative [Line Items]
LIBOR basis points		One-month LIBOR
Notional amount of derivatives		$ 110,000,000
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
Treasury Forward Interest Rate Locks ("T-Locks") [Member] | Subordinated Notes [Member]
Derivative [Line Items]
Senior notes issuance		$ 500,000,000

Derivative Financial Instrume70

Derivative Financial Instruments and Hedging Activities - Schedule of Notional Amounts and Fair Values of Derivatives Outstanding (Detail) - USD ($)	Mar. 31, 2017	Dec. 31, 2016
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Forward commitments to sell residential mortgage loans	$ 97,100,000	$ 160,400,000
Total, Derivatives Designated as Hedging Instruments, Fair Values, Assets		13,600,000
Total Derivatives Fair value,Assets	97,100,000	174,000,000
Total, Derivatives Not Designated as Hedging Instruments, Fair Values, Liabilities	73,700,000	121,600,000
Total, Derivatives Designated as Hedging Instruments, Fair Values, Liabilities		100,000
Fair Values, Liabilities	73,700,000	121,700,000
Forward Commitments to Sell Residential Mortgage Loans [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amounts	39,400,000	48,600,000
Forward commitments to sell residential mortgage loans	700,000	300,000
Total Derivatives Fair value,Assets	700,000	300,000
Interest Rate-Lock Commitments on Residential Mortgage Loans [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amounts	46,900,000	57,000,000
Derivatives Not Designated as Hedging Instruments, Foreign exchange contracts, Fair Values, Liabilities	900,000	400,000
Fair Values, Liabilities	900,000	400,000
Interest Rate Swaps [Member] | Fair Value [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amounts	375,000,000
Interest Rate Swaps [Member] | Cash Flow [Member] | Loans [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amounts	110,000,000
Derivative Assets Designated as Hedging Instruments, Fair Values, Assets	0	0
Interest Rate Swaps [Member] | Commercial Customers [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amounts	5,786,000,000	5,612,200,000
Derivatives Not Designated as Hedging Instruments, Interest rate swaps, Fair Values, Assets	85,300,000	93,900,000
Derivatives Not Designated as Hedging Instruments, Foreign exchange contracts, Fair Values, Liabilities	50,900,000	46,900,000
Interest Rate Swaps [Member] | Institutional Counterparties [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amounts	5,793,700,000	5,620,200,000
Derivatives Not Designated as Hedging Instruments, Interest rate swaps, Fair Values, Assets	10,900,000	65,600,000
Derivatives Not Designated as Hedging Instruments, Foreign exchange contracts, Fair Values, Liabilities	21,800,000	74,000,000
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
Total, Derivatives Designated as Hedging Instruments, Fair Values, Liabilities	0	0
Interest Rate Swaps [Member] | Subordinated Notes [Member] | Cash Flow [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amounts		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
Risk Participation Agreements [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amounts	268,600,000	251,900,000
Foreign Exchange Contracts [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amounts	41,900,000	101,200,000
Derivatives Not Designated as Hedging Instruments, Foreign exchange contracts, Fair Values, Assets	200,000	600,000
Total Derivatives Fair value,Assets	200,000	600,000
Derivatives Not Designated as Hedging Instruments, Interest rate swaps, Fair Values, Liabilities	100,000	300,000
Fair Values, Liabilities	$ 100,000	$ 300,000

Derivative Financial Instrume71

Derivative Financial Instruments and Hedging Activities - Schedule of Notional Amounts and Fair Values of Derivatives Outstanding (Parenthetical) (Detail) - USD ($)	Mar. 31, 2017	Dec. 31, 2016
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

Derivative Financial Instrume72

Derivative Financial Instruments and Hedging Activities - Impact of Derivatives on Pre-Tax Income and Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of Pre-Tax Gain (Loss) Recognized in Earnings	$ 4.6	$ 4
Derivatives Not Designated as Hedging Instruments [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of Pre-Tax Gain (Loss) Recognized in Earnings	2.9	1.7
Derivatives Not Designated as Hedging Instruments [Member] | Forward Commitments to Sell Residential Mortgage Loans [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of Pre-Tax Gain (Loss) Recognized in Earnings	0.3
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)
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	2.5	136.1
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	0.2	(132.9)
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	0.1	(1.4)
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	0.1
Derivatives Designated as Hedging Instruments [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of Pre-Tax Gain (Loss) Recognized in Earnings	1.7	2.3
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	1.7	2.3
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	$ (0.1)	(0.3)
Amount of Pre-Tax Gain (Loss) Recognized in AOCL		$ (0.3)

Derivative Financial Instrume73

Derivative Financial Instruments and Hedging Activities - Impact of Derivatives on Pre-Tax Income and Accumulated Other Comprehensive Loss (Parenthetical) (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative income	$ 4,600,000	$ 4,000,000
Derivatives Designated as Hedging Instruments [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative income	1,700,000	2,300,000
Interest Rate-Lock Commitments on Residential Mortgage Loans [Member] | Maximum [Member] | Derivatives Designated as Hedging Instruments [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative income	$ 100,000	$ 100,000

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	Mar. 31, 2017	Dec. 31, 2016
Offsetting Assets And Liabilities [Line Items]
Financial assets, Gross Amount Recognized	$ 97.1	$ 174
Financial liabilities, Gross Amount Recognized	73.7	121.7
Financial assets, Gross Amount Recognized	11.1	79.8
Financial assets, Gross Amount Offset	0	0
Financial assets, Net Amount Presented	11.1	79.8
Financial assets, Financial Instruments	(9.2)	(58.3)
Financial assets, Collateral	(1.6)	(20.9)
Financial assets, Net Amount	0.3	0.6
Financial liabilities, Gross Amount Recognized	21.9	74.4
Financial liabilities, Gross Amount Offset	0	0
Financial liabilities, Net Amount Presented	21.9	74.4
Financial liabilities, Financial Instruments	(9.2)	(58.3)
Financial liabilities, Collateral	(12.4)	(13.4)
Financial liabilities, Net Amount	0.3	2.7
Foreign Exchange Contracts [Member]
Offsetting Assets And Liabilities [Line Items]
Financial assets, Gross Amount Recognized	0.2	0.6
Financial assets, Gross Amount Offset	0	0
Financial assets, Net Amount Presented	0.2	0.6
Financial assets, Net Amount	0.2	0.6
Financial liabilities, Gross Amount Recognized	0.1	0.3
Financial liabilities, Gross Amount Offset	0	0
Financial liabilities, Net Amount Presented	0.1	0.3
Financial liabilities, Net Amount	0.1	0.3
Counterparty A [Member] | Interest Rate Swaps [Member]
Offsetting Assets And Liabilities [Line Items]
Financial assets, Gross Amount Recognized	2.1	1.9
Financial assets, Gross Amount Offset	0	0
Financial assets, Net Amount Presented	2.1	1.9
Financial assets, Financial Instruments	(2.1)	(1.9)
Financial liabilities, Gross Amount Recognized	3.7	4.3
Financial liabilities, Gross Amount Offset	0	0
Financial liabilities, Net Amount Presented	3.7	4.3
Financial liabilities, Financial Instruments	(2.1)	(1.9)
Financial liabilities, Collateral	(1.6)	(2.4)
Counterparty B [Member] | Interest Rate Swaps [Member]
Offsetting Assets And Liabilities [Line Items]
Financial assets, Gross Amount Recognized	1.3	1
Financial assets, Gross Amount Offset	0	0
Financial assets, Net Amount Presented	1.3	1
Financial assets, Financial Instruments	(1.3)	(1)
Financial liabilities, Gross Amount Recognized	7	7.7
Financial liabilities, Gross Amount Offset	0	0
Financial liabilities, Net Amount Presented	7	7.7
Financial liabilities, Financial Instruments	(1.3)	(1)
Financial liabilities, Collateral	(5.7)	(6.7)
Counterparty C [Member] | Interest Rate Swaps [Member]
Offsetting Assets And Liabilities [Line Items]
Financial assets, Gross Amount Recognized	2	1.7
Financial assets, Gross Amount Offset	0	0
Financial assets, Net Amount Presented	2	1.7
Financial assets, Financial Instruments	(2)	(1.7)
Financial liabilities, Gross Amount Recognized	3.5	3.4
Financial liabilities, Gross Amount Offset	0	0
Financial liabilities, Net Amount Presented	3.5	3.4
Financial liabilities, Financial Instruments	(2)	(1.7)
Financial liabilities, Collateral	(1.5)	(1.1)
Financial liabilities, Net Amount		0.6
Counterparty D [Member] | Interest Rate Swaps [Member]
Offsetting Assets And Liabilities [Line Items]
Financial assets, Gross Amount Recognized	3.5	3.4
Financial assets, Gross Amount Offset	0	0
Financial assets, Net Amount Presented	3.5	3.4
Financial assets, Financial Instruments	(3.5)	(3.4)
Financial liabilities, Gross Amount Recognized	6.2	6.9
Financial liabilities, Gross Amount Offset	0	0
Financial liabilities, Net Amount Presented	6.2	6.9
Financial liabilities, Financial Instruments	(3.5)	(3.4)
Financial liabilities, Collateral	(2.5)	(1.7)
Financial liabilities, Net Amount	0.2	1.8
Counterparty E [Member] | Interest Rate Swaps [Member]
Offsetting Assets And Liabilities [Line Items]
Financial assets, Gross Amount Recognized		69.6
Financial assets, Gross Amount Offset		0
Financial assets, Net Amount Presented		69.6
Financial assets, Financial Instruments		(50)
Financial assets, Collateral		(19.6)
Financial liabilities, Gross Amount Recognized		50
Financial liabilities, Gross Amount Offset		0
Financial liabilities, Net Amount Presented		50
Financial liabilities, Financial Instruments		(50)
Other Counterparties [Member] | Interest Rate Swaps [Member]
Offsetting Assets And Liabilities [Line Items]
Financial assets, Gross Amount Recognized	2	1.6
Financial assets, Gross Amount Offset	0	0
Financial assets, Net Amount Presented	2	1.6
Financial assets, Financial Instruments	(0.3)	(0.3)
Financial assets, Collateral	(1.6)	(1.3)
Financial assets, Net Amount	0.1
Financial liabilities, Gross Amount Recognized	1.4	1.8
Financial liabilities, Gross Amount Offset	0	0
Financial liabilities, Net Amount Presented	1.4	1.8
Financial liabilities, Financial Instruments	(0.3)	(0.3)
Financial liabilities, Collateral	$ (1.1)	$ (1.5)

New Accounting Standards - Addi

New Accounting Standards - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other windfall tax benefits	$ 1
Decrease in effective tax rate	1.00%
Percentage of interest income on financial assets and financial liabilities	75.00%
Percentage of non-interest income on financial assets and financial liabilities	25.00%
Percentage of other recurring revenue	10.00%
Equity securities, amortized cost	$ 3,808.8	$ 4,463.2
Equity securities, fair value	3,772.1	4,409.9
Equity Securities [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Equity securities, amortized cost	9.6	0.2
Equity securities, fair value	$ 8.9	$ 0.2

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) shares in Millions, $ in Millions	Apr. 01, 2017USD ($)shares	Mar. 31, 2017USD ($)Branches	Dec. 31, 2016USD ($)
Subsequent Event [Line Items]
Total loans		$ 29,456	$ 29,515.6
Total deposits		30,505.7	$ 29,860.8
Suffolk Bancorp [Member]
Subsequent Event [Line Items]
Total loans		$ 1,660
Business acquisition, date of acquisition agreement		Apr. 1, 2017
Total deposits		$ 1,850
Number of branches to be acquired | Branches		27
Merger-related expenses		$ 1
Suffolk Bancorp [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Business acquisition common stock shares | shares	26.6
Business acquisition common stock fair value	$ 485