Washington Trust Bancorp (WASH) 10-K 27 Feb 18 2017 Q4 Annual report Financial data

DOCUMENT AND ENTITY INFORMATION

DOCUMENT AND ENTITY INFORMATION - USD ($)	12 Months Ended
	Dec. 31, 2017	Jan. 31, 2018	Jun. 30, 2017
Document and Entity Information [Abstract]
Entity Registrant Name	Washington Trust Bancorp Inc
Entity Central Index Key	737,468
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-K
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q4
Amendment Flag	false
Entity Common Stock, Shares Outstanding		17,232,468
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 765,680,957

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Assets:
Cash and due from banks		$ 79,853	$ 106,185
Short-term investments		3,070	1,612
Mortgage loans held for sale, at fair value		26,943	29,434
Securities:
Available for sale, at fair value		780,954	739,912
Held to maturity, at amortized cost (fair value $12,721 in 2017 and $15,920 in 2016)		12,541	15,633
Total securities		793,495	755,545
Federal Home Loan Bank stock, at cost		40,517	43,129
Loans:
Total loans	[1]	3,374,071	3,234,371
Less allowance for loan losses		26,488	26,004
Net loans		3,347,583	3,208,367
Premises and equipment, net		28,333	29,020
Investment in bank-owned life insurance		73,267	71,105
Goodwill		63,909	64,059
Identifiable intangible assets, net		9,140	10,175
Other assets		63,740	62,484
Total assets		4,529,850	4,381,115
Liabilities:
Demand deposits		661,138	585,960
NOW accounts		466,605	427,707
Money market accounts		731,345	730,075
Savings accounts		368,524	358,397
Time deposits		1,015,095	961,613
Total deposits		3,242,707	3,063,752
Federal Home Loan Bank advances		791,356	848,930
Junior subordinated debentures		22,681	22,681
Other liabilities		59,822	54,948
Total liabilities		4,116,566	3,990,311
Commitments and contingencies
Shareholders’ Equity:
Common stock of $.0625 par value; authorized 60,000,000 shares; issued and outstanding 17,226,508 shares in 2017 and 17,170,820 shares in 2016		1,077	1,073
Paid-in capital		117,961	115,123
Retained earnings		317,756	294,365
Accumulated other comprehensive loss		(23,510)	(19,757)
Total shareholders’ equity		413,284	390,804
Total liabilities and shareholders’ equity		4,529,850	4,381,115
Commercial [Member]
Loans:
Total loans		1,822,829	1,771,666
Residential Real Estate [Member]
Loans:
Total loans		1,227,248	1,122,748
Consumer [Member]
Loans:
Total loans		323,994	339,957
Commercial Mortgages [Member]
Loans:
Total loans		1,072,487	1,074,186
Less allowance for loan losses		11,646	9,971
Commercial Mortgages [Member] | Commercial [Member]
Loans:
Total loans	[2]	1,072,487	1,074,186
Commercial Construction & Development [Member]
Loans:
Total loans		138,008	121,371
Less allowance for loan losses		1,083	1,195
Commercial Construction & Development [Member] | Commercial [Member]
Loans:
Total loans	[3]	138,008	121,371
Commercial & Industrial [Member]
Loans:
Total loans		612,334	576,109
Less allowance for loan losses	[4]	5,580	6,992
Commercial & Industrial [Member] | Commercial [Member]
Loans:
Total loans	[5]	$ 612,334	$ 576,109
[1]	Includes net unamortized loan origination costs of $3.8 million and $3.0 million, respectively, and net unamortized premiums on purchased loans of $878 thousand and $783 thousand, respectively, at December 31, 2017 and 2016.
[2]	Loans primarily secured by income producing property.
[3]	Loans for construction of commercial properties, loans to developers for construction of residential properties and loans for land development.
[4]	Commercial & industrial loans.
[5]	Loans to businesses and individuals, a substantial portion of which are fully or partially collateralized by real estate.

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Mortgage loans held for sale, fair value	$ 26,943	$ 29,434
Securities held to maturity, fair value	$ 12,721	$ 15,920
Common stock, par value (in dollars per share)	$ 0.0625	$ 0.0625
Common stock, shares authorized (in shares)	60,000,000	60,000,000
Common stock, shares issued (in shares)	17,226,508	17,170,820
Common stock, shares outstanding (in shares)	17,226,508	17,170,820

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Interest income:
Interest and fees on loans	$ 127,962	$ 119,491	$ 114,229
Taxable interest on securities	18,927	11,584	8,875
Nontaxable interest on securities	249	982	1,555
Dividends on corporate stock and Federal Home Loan Bank stock	1,774	1,091	953
Other interest income	674	322	138
Total interest and dividend income	149,586	133,470	125,750
Interest expense:
Deposits	15,064	12,504	13,142
Federal Home Loan Bank advances	14,377	9,992	7,746
Junior subordinated debentures	613	491	871
Other interest expense	1	5	9
Total interest expense	30,055	22,992	21,768
Net interest income	119,531	110,478	103,982
Provision for loan losses	2,600	5,650	1,050
Net interest income after provision for loan losses	116,931	104,828	102,932
Noninterest income:
Wealth management revenues	39,346	37,569	35,416
Mortgage banking revenues	11,392	13,183	9,901
Service charges on deposit accounts	3,672	3,702	3,865
Card interchange fees	3,502	3,385	3,199
Loan related derivative income	3,214	3,243	2,441
Income from bank-owned life insurance	2,161	2,659	1,982
Other income	1,522	1,388	1,536
Total noninterest income	64,809	65,129	58,340
Noninterest expense:
Salaries and employee benefits	68,487	67,221	63,024
Net occupancy	7,521	7,151	7,000
Outsourced services	6,920	5,222	5,111
Equipment	5,358	6,208	5,533
Legal, audit and professional fees	2,294	2,579	2,741
FDIC deposit insurance costs	1,647	1,878	1,846
Advertising and promotion	1,481	1,458	1,526
Amortization of intangibles	1,035	1,284	904
Debt prepayment penalties	0	431	0
Acquisition related expenses	0	0	989
Change in fair value of contingent consideration	(643)	(898)	41
Other expenses	10,000	8,569	8,214
Total noninterest expense	104,100	101,103	96,929
Income before income taxes	77,640	68,854	64,343
Income tax expense	31,715	22,373	20,878
Net income	$ 45,925	$ 46,481	$ 43,465
Weighted average common shares outstanding - basic	17,207	17,081	16,879
Weighted average common shares outstanding - diluted	17,338	17,208	17,067
Per share information:
Basic earnings per common share (in dollars per share)	$ 2.66	$ 2.72	$ 2.57
Diluted earnings per common share (in dollars per share)	2.64	2.70	2.54
Cash dividends declared per share (in dollars per share)	$ 1.54	$ 1.46	$ 1.36

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 45,925	$ 46,481	$ 43,465
Other comprehensive income (loss), net of tax:
Net change in fair value of securities available for sale	621	(7,876)	(3,171)
Net change in fair value of cash flow hedges	(52)	(257)	244
Net change in defined benefit plan obligation adjustment	(97)	(1,925)	2,037
Total other comprehensive income (loss), net of tax	472	(10,058)	(890)
Total comprehensive income	$ 46,397	$ 36,423	$ 42,575

CONSOLIDATED STATEMENTS OF CHAN

CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Common stock, shares outstanding, beginning balance at Dec. 31, 2014		16,746,000
Stockholders' equity, beginning balance at Dec. 31, 2014	$ 346,279	$ 1,047	$ 101,204	$ 252,837	$ (8,809)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	43,465			43,465
Total other comprehensive income (loss), net of tax	(890)				(890)
Cash dividends declared	(23,228)			(23,228)
Share-based compensation	2,074		2,074
Common stock issued for acquisition, shares		137,000
Common stock issued for acquisition	5,430	$ 8	5,422
Exercise of stock options and issuance of other compensation related equity instruments and related tax benefit, shares		137,000
Exercise of stock options and issuance of other compensation related equity instruments and related tax benefit	2,258	$ 9	2,249
Common stock, shares outstanding, ending balance at Dec. 31, 2015		17,020,000
Stockholders' equity, ending balance at Dec. 31, 2015	375,388	$ 1,064	110,949	273,074	(9,699)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	46,481			46,481
Total other comprehensive income (loss), net of tax	(10,058)				(10,058)
Cash dividends declared	(25,190)			(25,190)
Share-based compensation	2,190		2,190
Common stock issued for acquisition	0
Exercise of stock options and issuance of other compensation related equity instruments and related tax benefit, shares		151,000
Exercise of stock options and issuance of other compensation related equity instruments and related tax benefit	$ 1,993	$ 9	1,984
Common stock, shares outstanding, ending balance at Dec. 31, 2016	17,170,820	17,171,000
Stockholders' equity, ending balance at Dec. 31, 2016	$ 390,804	$ 1,073	115,123	294,365	(19,757)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	45,925			45,925
Total other comprehensive income (loss), net of tax	472				472
Cash dividends declared	(26,759)			(26,759)
Share-based compensation	2,577		2,577
Common stock issued for acquisition	0
Exercise of stock options, issuance of other compensation-related equity instruments and related tax benefit, shares		56,000
Exercise of stock options, issuance of other compensation-related equity instruments and related tax benefit	265	$ 4	261
Reclassification of income tax effects due to the adoption of ASU 2018-02	$ 0			4,225	(4,225)
Common stock, shares outstanding, ending balance at Dec. 31, 2017	17,226,508	17,227,000
Stockholders' equity, ending balance at Dec. 31, 2017	$ 413,284	$ 1,077	$ 117,961	$ 317,756	$ (23,510)

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net income	$ 45,925	$ 46,481	$ 43,465
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for loan losses	2,600	5,650	1,050
Depreciation of premises and equipment	3,454	3,651	3,381
Net amortization of premium and discount	3,426	2,779	1,568
Amortization of intangibles	1,035	1,284	904
Goodwill impairment	150	0	0
Share–based compensation	2,577	2,190	2,074
Tax benefit from stock option exercises and other equity instruments	508	1,016	694
Deferred income tax expense	5,687	868	1,820
Income from bank-owned life insurance	(2,161)	(2,659)	(1,982)
Net gains on loan sales and commissions on loans originated for others	(10,991)	(13,137)	(9,826)
Net gain on sale of portfolio loans	0	(135)	0
Proceeds from sales of loans	472,556	551,788	477,616
Loans originated for sale	(461,262)	(532,950)	(462,663)
Change in fair value of contingent consideration	(643)	(898)	41
(Increase) decrease in other assets	(8,794)	984	(4,165)
Increase (decrease) in other liabilities	5,318	(7,163)	(1,717)
Net cash provided by operating activities	59,385	59,749	52,260
Cash flows from investing activities:
Purchases of mortgage-backed securities available for sale	(89,194)	(431,662)	(44,682)
Purchases of other investment securities available for sale	(59,940)	(121,679)	(88,784)
Maturities and principal payments of mortgage-backed securities available for sale	84,381	65,673	50,083
Maturities and principal payments of other investment securities available for sale	22,071	108,256	60,085
Maturities and principal payments of mortgage-backed securities held to maturity	2,950	4,193	4,960
Remittance (purchases) of Federal Home Loan Bank stock	2,612	(18,813)	13,414
Net increase in loans	(120,582)	(112,966)	(152,306)
Proceeds from sale of portfolio loans	0	510	0
Purchases of loans	(20,278)	(113,562)	(3,085)
Proceeds from the sale of property acquired through foreclosure or repossession	1,053	731	1,580
Purchases of premises and equipment	(2,779)	(3,112)	(5,479)
Purchases of bank-owned life insurance	0	(5,000)	0
Proceeds from Life Insurance Policy	0	2,054	0
Cash used in business combination, net of cash acquired	0	0	(1,671)
Net cash used in investing activities	(179,706)	(625,377)	(165,885)
Cash flows from financing activities:
Net increase in deposits	178,955	129,497	179,437
Proceeds from Federal Home Loan Bank advances	1,352,501	1,428,750	495,500
Repayment of Federal Home Loan Bank advances	(1,410,075)	(958,793)	(522,824)
Proceeds from stock option exercises and issuance of other equity instruments	366	977	1,563
Cash dividends paid	(26,300)	(24,637)	(22,770)
Net cash provided by financing activities	95,447	575,794	130,906
Net (decrease) increase in cash and cash equivalents	(24,874)	10,166	17,281
Cash and cash equivalents at beginning of year	107,797	97,631	80,350
Cash and cash equivalents at end of year	82,923	107,797	97,631
Noncash Investing and Financing Activities:
Loans charged off	2,462	7,012	2,305
Loans transferred to property acquired through foreclosure or repossession	576	1,075	1,206
In conjunction with a purchase acquisition, assets were acquired and liabilities were assumed as follows:
Common stock issued for acquisition	0	0	5,430
Fair value of assets acquired, net of cash acquired	0	0	14,315
Fair value of liabilities assumed	0	0	7,214
Supplemental Disclosures:
Interest payments	29,687	22,267	21,947
Income tax payments	$ 25,988	$ 19,822	$ 20,213

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation Washington Trust Bancorp, Inc. (the “Bancorp”) is a publicly-owned registered bank holding company that has elected to be a financial holding company. The Bancorp owns all of the outstanding common stock of The Washington Trust Company, of Westerly (the “Bank”), a Rhode Island chartered commercial bank founded in 1800. Through its subsidiaries, the Bancorp offers a complete product line of financial services including commercial, residential and consumer lending, retail and commercial deposit products, and wealth management services through its offices in Rhode Island, eastern Massachusetts and Connecticut. The consolidated financial statements include the accounts of the Bancorp and its subsidiaries (collectively, the “Corporation” or “Washington Trust”). All intercompany transactions have been eliminated. Certain previously reported amounts have been reclassified to conform to current year’s presentation. The accounting and reporting policies of the Corporation conform to GAAP and to general practices of the banking industry. In preparing the financial statements, management is required to make estimates and assumptions that affect the reported amounts of assets and liabilities as of the date of the balance sheet and revenues and expenses for the period. Actual results could differ from those estimates. Material estimates that are particularly susceptible to change are the determination of the allowance for loan losses, the valuation of goodwill and identifiable intangible assets, the assessment of investment securities for impairment and the accounting for defined benefit pension plans. Short-term Investments Short-term investments consist of highly liquid investments with a maturity date of three months or less when purchased and are considered to be cash equivalents. The Corporation’s short-term investments may be comprised of overnight federal funds sold, securities purchased under resale agreements, money market mutual funds and U.S. Treasury bills. Securities Management determines the appropriate classification of securities at the time of purchase. Investments in debt securities that management has the positive intent and ability to hold to maturity are classified as held to maturity and carried at amortized cost. Investments not classified as held to maturity are classified as available for sale. Securities available for sale consist of debt securities that are available for sale to respond to changes in market interest rates, liquidity needs, changes in funding sources and other similar factors. These assets are specifically identified and are carried at fair value. Changes in fair value of available for sale securities, net of applicable income taxes, are reported as a separate component of shareholders’ equity. Washington Trust does not have a trading portfolio. Premiums and discounts are amortized and accreted over the term of the securities on a method that approximates the level yield method. The amortization and accretion is included in interest income on securities. Interest income is recognized when earned. Realized gains or losses from sales of securities are determined using the specific identification method. The fair values of securities may be based on either quoted market prices or third party pricing services. When the fair value of an investment security is less than its amortized cost basis, the Corporation assesses whether the decline in value is other-than-temporary. The Corporation considers whether evidence indicating the cost of the investment is recoverable outweighs evidence to the contrary. Evidence considered in this assessment includes the reasons for impairment, the severity and duration of the impairment, changes in the value subsequent to the reporting date, forecasted performance of the issuer, changes in the dividend or interest payment practices of the issuer, changes in the credit rating of the issuer or the specific security, and the general market condition in the geographic area or industry in which the issuer operates. In determining whether an other-than-temporary impairment has occurred for debt securities, the Corporation compares the present value of cash flows expected to be collected from the security with the amortized cost of the security. If the present value of expected cash flows is less than the amortized cost of the security, then the entire amortized cost of the security will not be recovered; that is, a credit loss exists, and an other-than-temporary impairment shall be considered to have occurred. The credit loss component of an other-than-temporary impairment write-down for debt securities is recorded in earnings while the remaining portion of the impairment loss is recognized, net of tax, in other comprehensive income provided that the Corporation does not intend to sell the underlying debt security and it is more-likely-than-not that the Corporation would not have to sell the debt security prior to recovery of the unrealized loss, which may be to maturity. If the Corporation intended to sell any securities with an unrealized loss or it is more-likely-than-not that the Corporation would be required to sell the investment securities before recovery of their amortized cost basis, then the entire unrealized loss would be recorded in earnings. See Note 4 for further discussion on the Corporation’s investment securities portfolio. Federal Home Loan Bank Stock The Bank is a member of the FHLB. The FHLB is a cooperative that provides services, including funding in the form of advances, to its member banking institutions. As a requirement of membership, the Bank must own a minimum amount of FHLB stock, calculated periodically based primarily on its level of borrowings from the FHLB. No market exists for shares of FHLB stock and therefore, they are carried at par value. FHLB stock may be redeemed at par value five years following termination of FHLB membership, subject to limitations which may be imposed by the FHLB or its regulator, the Federal Housing Finance Board, to maintain capital adequacy of the FHLB. While the Corporation currently has no intentions to terminate its FHLB membership, the ability to redeem its investment in FHLB stock would be subject to the conditions imposed by the FHLB. The Corporation monitors its investment to determine if impairment exists. Based on the capital adequacy and the liquidity position of the FHLB, management believes there is no impairment related to the carrying amount of the Corporation’s FHLB stock as of December 31, 2017 . Mortgage Banking Activities Mortgage Loans Held for Sale Residential mortgage loans originated and intended for sale in the secondary market are classified as held for sale. The Corporation has elected the fair value option pursuant to Accounting Standards Codification (“ASC”) 825, “Financial Instruments” for closed loans intended for sale. ASC 825 allows for the irrevocable option to elect fair value accounting for the initial and subsequent measurement for certain financial assets and liabilities on a contract-by-contract basis that may otherwise not be required to be measured at fair value under other accounting standards. Washington Trust elected the fair value option for residential real estate mortgage loans held for sale pursuant to forward sale commitments in order to better match changes in fair values of the loans with changes in the fair value of the derivative forward loan sale contracts used to economically hedge them. Changes in the fair value of loans held for sale are recorded in earnings and are offset by changes in fair value relating to forward sale commitments and interest rate lock commitments. For residential mortgage loans intended for sale that are not accounted for under the fair value option, lower of cost or market (“LOCOM”) accounting is applied. Such loans are carried at lower of aggregate cost, net of unamortized deferred loan origination fees and costs, or fair value. Gains and losses on residential loan sales are recognized at the time of sale and included in mortgage banking revenues. Commissions received on mortgage loans brokered to various investors are recognized when received and included in mortgage banking revenues. Loan Servicing Rights Rights to service mortgage loans for others are recognized as an asset, including rights acquired through both purchases and originations. Upon the sale of mortgage loans, a mortgage servicing asset is established, which represents the current estimated fair value based on the present value of estimated future net servicing income. The valuation model incorporates assumptions that market participants would use in estimating future net servicing income, such as the cost to service, the discount rate, ancillary income, prepayment speeds, and default rates and losses. Capitalized loan servicing rights are included in other assets. Mortgage servicing rights are amortized as an offset to mortgage banking revenues over the period of estimated net servicing income. They are periodically evaluated for impairment based on their fair value. Impairment is measured on an aggregated basis by stratifying the rights based on homogeneous characteristics such as note rate and loan type. The fair value is estimated based on the present value of expected cash flows, incorporating assumptions for discount rate, prepayment speed and servicing cost. Any impairment is recognized through a valuation allowance and as a reduction to mortgage banking revenues. Loans Portfolio Loans Loans held in the portfolio are stated at the principal amount outstanding, net of unamortized deferred loan origination fees and costs. Interest income is accrued on a level yield basis based on principal amounts outstanding. Deferred loan origination fees and costs are amortized as an adjustment to yield over the life of the related loans. Nonaccrual Loans Loans, with the exception of certain well-secured loans that are in the process of collection, are placed on nonaccrual status and interest recognition is suspended when such loans are 90 days or more overdue with respect to principal and/or interest or sooner if considered appropriate by management. Well-secured loans are permitted to remain on accrual status provided that full collection of principal and interest is assured and the loan is in the process of collection. Loans are also placed on nonaccrual status when, in the opinion of management, full collection of principal and interest is doubtful. When loans are placed on nonaccrual status, interest previously accrued but not collected is reversed against current period income. Subsequent interest payments received on nonaccrual loans are applied to the outstanding principal balance of the loan or recognized as interest income depending on management’s assessment of the ultimate collectability of the loan. Loans are removed from nonaccrual status when they have been current as to principal and interest for a period of time, the borrower has demonstrated an ability to comply with repayment terms, and when, in management’s opinion, the loans are considered to be fully collectible. Impaired Loans Impaired loans are loans for which it is probable that the Corporation will not be able to collect all amounts due according to the contractual terms of the loan agreements and loans restructured in a troubled debt restructuring. Impairment is measured on a discounted cash flow method based upon the loan’s contractual effective interest rate, or at the loan’s observable market price, or if the loan is collateral dependent, at the fair value. For collateral dependent loans for which repayment is dependent on the sale of the collateral, management adjusts the fair value for estimated costs to sell. For collateral dependent loans for which repayment is dependent on the operation of the collateral, such as accruing troubled debt restructured loans, estimated costs to sell are not incorporated into the measurement. Interest income on nonaccrual impaired loans is recognized as described above under the caption “Nonaccrual Loans.” Accruing impaired loans consist of those troubled debt restructurings for which management has concluded that the collectability of the loan is not in doubt. Troubled Debt Restructured Loans Loans are considered to be troubled debt restructurings when the Corporation has granted concessions to a borrower due to the borrower’s financial condition that it otherwise would not have considered. These concessions may include modifications of the terms of the debt such as deferral of payments, extension of maturity, reduction of principal balance, reduction of the stated interest rate other than normal market rate adjustments, or a combination of these concessions. Debt may be bifurcated with separate terms for each tranche of the restructured debt. Restructuring of a loan in lieu of aggressively enforcing the collection of the loan may benefit the Corporation by increasing the ultimate probability of collection. Restructured loans are classified as accruing or non-accruing based on management’s assessment of the collectability of the loan. Loans which are already on nonaccrual status at the time of the restructuring generally remain on nonaccrual status for approximately six months before management considers such loans for return to accruing status. Accruing restructured loans are placed into nonaccrual status if and when the borrower fails to comply with the restructured terms and management deems it unlikely that the borrower will return to a status of compliance in the near term. Troubled debt restructurings are reported as such for at least one year from the date of the restructuring. In years after the restructuring, troubled debt restructured loans are removed from this classification if the restructuring did not involve a below-market rate concession and the loan is not deemed to be impaired based on the terms specified in the restructuring agreement. Allowance for Loan Losses The allowance for loan losses is management’s best estimate of the risk of loss inherent in the loan portfolio as of the balance sheet date. The allowance is increased by provisions charged to earnings and by recoveries of amounts previously charged off, and is reduced by charge-offs on loans. Loan charge-offs are recognized when management believes the collectability of the principal balance outstanding is unlikely. Full or partial charge-offs on collateral dependent impaired loans are generally recognized when the collateral is deemed to be insufficient to support the carrying value of the loan. The level of the allowance is based on management’s ongoing review of the growth and composition of the loan portfolio, historical loss experience, estimated loss emergence period (the period from the event that triggers the eventual default until the actual loss is recognized with a charge-off), current economic conditions, analysis of asset quality and credit quality levels and trends, the performance of individual loans in relation to contract terms and other pertinent factors. A methodology is used to systematically measure the amount of estimated loan loss exposure inherent in the loan portfolio for the purposes of establishing a sufficient allowance for loan losses. The methodology includes: (1) the identification of loss allocations for individual loans deemed to be impaired and (2) the application of loss allocation factors for non-impaired loans based on historical loss experience and estimated loss emergence period, with adjustments for various exposures that management believes are not adequately represented by historical loss experience. Loss allocations for loans deemed to be impaired are measured on a discounted cash flow method based upon the loan’s contractual effective interest rate, or at the loan’s observable market price, or, if the loan is collateral dependent, at the fair value of the collateral. For collateral dependent loans for which repayment is dependent on the sale of the collateral, management adjusts the fair value for estimated costs to sell. For collateral dependent loans for which repayment is dependent on the operation of the collateral, such as accruing troubled debt restructured loans, estimated costs to sell are not incorporated into the measurement. Management may also adjust appraised values to reflect estimated market value declines or apply other discounts to appraised values for unobservable factors resulting from its knowledge of circumstances associated with the property. For loans that are collectively evaluated, loss allocation factors are derived by analyzing historical loss experience by loan segment over an established look-back period deemed to be relevant to the inherent risk of loss in the portfolios. Loans are segmented by loan type, collateral type, delinquency status and loan risk rating, where applicable. These loss allocation factors are adjusted to reflect the loss emergence period. These amounts are supplemented by certain qualitative risk factors reflecting management’s view of how losses may vary from those represented by historical loss rates. These qualitative risk factors include: 1) changes in lending policies and procedures, including changes in underwriting standards and collection, charge-off, and recovery practices not considered elsewhere in estimating credit losses; 2) changes in international, national, regional, and local economic and business conditions and developments that affect the collectability of the portfolio, including the condition of various market segments; 3) changes in the nature and volume of the portfolio and in the terms of loans; 4) changes in the experience, ability, and depth of lending management and other relevant staff; 5) changes in the volume and severity of past due loans, the volume of nonaccrual loans, and the volume and severity of adversely classified or rated loans; 6) changes in the quality of the institution’s loan review system; 7) changes in the value of underlying collateral for collateral dependent loans; 8) the existence and effect of any concentrations of credit, and changes in the level of such concentrations; and 9) the effect of other external factors such as legal and regulatory requirements on the level of estimated credit losses in the institution’s existing portfolio. Because the methodology is based upon historical experience and trends, current economic data, as well as management’s judgment, factors may arise that result in different estimations. Adversely different conditions or assumptions could lead to increases in the allowance. In addition, various regulatory agencies periodically review the allowance for loan losses. Such agencies may require additions to the allowance based on their judgments about information available to them at the time of their examination. The allowance is an estimate, and ultimate losses may vary from management’s estimate. Changes in the estimate are recorded in the results of operations in the period in which they become known, along with provisions for estimated losses incurred during that period. Premises and Equipment Premises and equipment are stated at cost less accumulated depreciation. Depreciation for financial reporting purposes is calculated on the straight-line method over the estimated useful lives of assets. Leasehold improvements are depreciated over the shorter of the lease terms or the estimated useful lives of the improvements. Expected terms include lease renewal options to the extent that the exercise of such renewals is reasonably assured. Expenditures for major additions and improvements are capitalized while the costs of current maintenance and repairs are charged to operating expenses. The estimated useful lives of premises and improvements range from 5 to 40 years. For furniture, fixtures and equipment, the estimated useful lives range from 3 to 20 years. Goodwill and Other Identifiable Intangible Assets The Corporation allocated the cost of acquired entities to the assets acquired and liabilities assumed based on their estimated fair values at the date of acquisition. Other intangible assets identified in acquisitions consist of wealth management advisory contracts. The value attributed to other intangible assets was based on the time period over which they are expected to generate economic benefits. The excess of the purchase price for acquisitions over the fair value of the net assets acquired, including other intangible assets, is recorded as goodwill. Goodwill is not amortized but is tested for impairment at the reporting unit level, defined as the segment level, at least annually in the fourth quarter or more frequently whenever events or circumstances occur that indicate that it is more-likely-than-not that an impairment loss has occurred. In assessing impairment, the Corporation has the option to perform a qualitative analysis to determine whether the existence of events or circumstances leads to a determination that it is more-likely-than-not that the fair value of the reporting unit is less than its carrying amount. If, after assessing the totality of such events or circumstances, we determine it is not more-likely-than-not that the fair value of a reporting unit is less than its carrying amount, then we would not be required to perform an impairment test. Effective April 1, 2017, the Corporation early adopted the provisions of ASU 2017-04 “Simplifying the Test for Goodwill Impairment”, which eliminated Step 2 of the annual two-step goodwill impairment test. Step 2 was a more detailed analysis, which involved measuring the excess of the fair value of the reporting unit, as determined in Step 1, over the aggregate fair value of the individual assets, liabilities, and identifiable intangibles as if the reporting unit was being acquired in a business combination. As Step 2 was eliminated, goodwill is tested for impairment using the quantitative impairment analysis described below. The quantitative impairment analysis requires a comparison of each reporting unit’s fair value to its carrying value to identify potential impairment. Goodwill impairment exists when a reporting unit’s carrying value of goodwill exceeds its implied fair value. Significant judgment is applied when goodwill is assessed for impairment. This judgment includes, but may not be limited to, the selection of appropriate discount rates, the identification of relevant market comparables and the development of cash flow projections. The selection and weighting of the various fair value techniques may result in a higher or lower fair value. Judgment is applied in determining the weightings that are most representative of fair value. Other intangible assets with definite lives are tested for impairment whenever events or circumstances occur that indicate that the carrying amount may not be recoverable. If applicable, the Corporation tests each of the intangibles by comparing the carrying value of the intangible asset to the sum of undiscounted cash flows expected to be generated by the asset. If the carrying amount of the asset exceeded its undiscounted cash flows, then an impairment loss would be recognized for the amount by which the carrying amount exceeds its fair value. Impairment of Long - Lived Assets Other than Goodwill Long-lived assets are reviewed for impairment whenever events or changes in business circumstances indicate that the the carrying amount may not be fully recoverable. If impairment is determined to exist, any related impairment loss is calculated based on fair value. Impairment losses on assets to be disposed of, if any, are based on the estimated proceeds to be received, less costs of disposal. Property Acquired through Foreclosure or Repossession Property acquired through foreclosure or repossession is carried at the lower of cost or fair value less estimated costs to sell. Fair value of such assets is determined based on independent appraisals and other relevant factors. Any write-down to fair value at the time of foreclosure or repossession is charged to the allowance for loan losses. A valuation allowance is maintained for declines in market value and for estimated selling expenses. Increases to the valuation allowance, expenses associated with ownership of these properties, and gains and losses from their sale are included in foreclosed property costs. Loans that are substantively repossessed include only those loans for which the Corporation has obtained control of the collateral, but has not completed legal foreclosure proceedings. Bank-Owned Life Insurance The investment in BOLI represents the cash surrender value of life insurance policies on the lives of certain employees who have provided positive consent allowing the Bank to be the beneficiary of such policies. Increases in the cash value of the policies, as well as insurance proceeds received, are recorded in noninterest income and are not subject to income taxes. The financial strength of the insurance carrier is reviewed prior to the purchase of BOLI and annually thereafter. Investment in Real Estate Limited Partnership Washington Trust has a 99.9% ownership interest in two real estate limited partnerships that renovate, own and operate two low-income housing complexes. Washington Trust neither actively participates nor has a controlling interest in these limited partnerships and accounts for its investments under the equity method of accounting. The carrying value of the investments is recorded in other assets on the Consolidated Balance Sheet. Net losses generated by the partnership are recorded as a reduction to Washington Trust’s investment and as a reduction of other noninterest income in the Consolidated Statements of Income. Tax credits generated by the partnership are recorded as a reduction in the income tax provision in the year they are allowed for tax reporting purposes. The results of operations of the real estate limited partnerships are periodically reviewed to determine if the partnership generates sufficient operating cash flow to fund its current obligations. In addition, the current value of the underlying properties is compared to the outstanding debt obligations. If it is determined that the investment is permanently impaired, the carrying value will be written down to the estimated realizable value. Transfers and Servicing of Assets and Extinguishments of Liabilities The accounting for transfers and servicing of financial assets and extinguishments of liabilities is based on consistent application of a financial components approach that focuses on control. This approach distinguishes transfers of financial assets that are sales from transfers that are secured borrowings. After a transfer of financial assets, the Corporation recognizes all financial and servicing assets it controls and liabilities it has incurred and derecognizes financial assets it no longer controls and liabilities that have been extinguished. This financial components approach focuses on the assets and liabilities that exist after the transfer. Many of these assets and liabilities are components of financial assets that existed prior to the transfer. If a transfer does not meet the criteria for a sale, the transfer is accounted for as a secured borrowing with a pledge of collateral. Wealth Management Assets Under Administration Assets under administration represent assets held in a fiduciary or agency capacity for wealth management clients and are not included in the Consolidated Balance Sheets, as these are not assets of the Corporation. Wealth management revenue derived from the administration, management and custody of assets under administration are referred to as asset-based revenues. Fee Revenue Wealth management revenues include asset-based revenues that are primarily accrued as earned based upon a percentage of asset values under administration. Also included in wealth management revenues are transaction-based revenues, which include financial planning fees, tax preparation fees, commissions and other service fees, which are recognized as revenue to the extent that services have been completed. Fee revenue from deposit service charges is generally recognized when earned. Pension Costs Pension benefits are accounted for using the net periodic benefit cost method, which recognizes the compensation cost of an employee’s pension benefit over that employee’s approximate service period. Pension benefit costs and benefit obligations incorporate various actuarial and other assumptions, including discount rates, mortality, rates of return on plan assets and compensation increases. Washington Trust evaluates these assumptions on an annual basis and makes modifications to the assumptions based on current rates and trends when it is appropriate to so do. The effect of modifications to those assumptions is recorded in other comprehensive income (loss) and amortized to net periodic cost over future periods. Washington Trust believes that the assumptions utilized in recording its obligations under its plans are reasonable based on its experience and market conditions. The funded status of defined benefit pension plans, measured as the difference between the fair value of plan assets and the projected benefit obligation, is recognized in the Consolidated Balance Sheet. The changes in the funded status of the defined benefit plans, including actuarial gains and losses and prior service costs and credits, are recognized in comprehensive income in the year in which the changes occur. Share-Based Compensation Share-based compensation plans provide for awards of stock options and other equity incentives, including nonvested share units and nonvested performance share units. Compensation expense for awards is recognized over the service period based on the fair value at the date of grant. The Corporation estimates grant date fair value for stock options using the Black-Scholes option-pricing model. Awards of nonvested share units and nonvested performance share units are valued at the fair market value of the Bancorp’s common stock as of the award date. Nonvested performance share unit compensation expense is based on the most recent performance assumption available and is adjusted as assumptions change. If the goals are not met, no compensation cost will be recognized and any recognized compensation costs will be reversed. Effective January 1, 2017, excess tax benefits (expenses) related to stock option exercises, settlement of other equity awards and dividends paid on nonvested share awards are recorded as a decrease (increase) to income tax expense. Prior to 2017, such excess tax benefits were recognized as additional paid in capital in shareholders' equity and did not impact income tax expense. Excess tax benefits (expenses) on the settlement of share-based awards are reflected in the Consolidated Statements of Cash Flows as an operating activity. Income Taxes Income tax expense is determined based on the asset and liability method, whereby deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The Corporation recognizes the effect of income tax positions only if those positions are more likely than not of being sustained. Recognized income tax positions are measured at the largest amount that is greater than 50% likely of being realized. Changes in recognition or measurement are reflected in the period in which the change in judgment occurs. The Corporation records interest related to unrecognized tax benefits in income tax expense. Penalties, if incurred, would be recognized as a component of income tax expense. Segment Reporting Washington Trust segregates financial information in assessing its results among its Commercial Banking and Wealth Management Services operating segments. The amounts in the Corporate unit include activity not related to the segments. The methodologies and organizational hierarchies that define the business segments are periodically reviewed and revised. Results may be restated, when necessary, to reflect changes in organizational structure or allocation methodology. Any changes in estimates and allocations that may affect the reported results of any business segment will not affect the consolidated financial position or results

Recently Issued Accounting Pron

Recently Issued Accounting Pronouncements	12 Months Ended
	Dec. 31, 2017
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements Revenue from Contracts with Customers - Topic 606 Accounting Standards Update No. 2014-09, “Revenue from Contracts with Customers” (“ASU 2014-09”), was issued in May 2014 and provides a revenue recognition framework for any entity that either enters into contracts with customers to transfer goods or services or enters into contracts for the transfer of non-financial assets unless those contracts are within the scope of other accounting standards. As originally issued, ASU 2014-09 was effective for annual periods beginning after December 15, 2016, including interim periods within that reporting period with early adoption not permitted. In August 2015, Accounting Standards Update No. 2015-14, “Deferral of the Effective Date” (“ASU 2015-14”) was issued and delayed the effective date of ASU 2014-09 to annual and interim periods in fiscal years beginning after December 15, 2017. In 2016, Accounting Standards Update No. 2016-08, “Principal versus Agent Considerations” (“ASU 2016-08”), Accounting Standards Update No. 2016-10, “Identifying Performance Obligations and Licensing” (“ASU 2016-10”) and Accounting Standards Update No. 2016-12, “Narrow-Scope Improvements and Practical Expedients” (“ASU 2016-12”) were issued. These ASUs do not change the core principle for revenue recognition in Topic 606; instead, the amendments provide more detailed guidance in a few areas and additional implementation guidance and examples, which were expected to reduce the degree of judgment necessary to comply with Topic 606. The effective date and transition requirements for ASU 2016-08, ASU 2016-10 and ASU 2016-12 are the same as those provided by ASU 2015-14. Management assembled a project team to address the changes pursuant to Topic 606. The project team completed a scope assessment and contract review for in-scope revenue streams. Washington Trust's largest source of revenue is net interest income on financial assets and liabilities, which is explicitly excluded from the scope of this ASU. Revenue streams that are within the scope of Topic 606 include wealth management revenues, service charges on deposit accounts and card interchange fees. Management does not anticipate material changes in the timing or measurement of in-scope revenues or contract acquisition costs. Management has also completed its evaluation of the expanded disclosure requirements. The Corporation plans to adopt ASU 2014-09 effective January 1, 2018 using the modified retrospective transition method. The adoption of ASU 2014-09 is not expected to have a material impact on the Corporation’s consolidated financial statements. Financial Instruments - Overall - Topic 825 Accounting Standards Update No. 2016-01, “Recognition and Measurement of Financial Assets and Financial Liabilities” (“ASU 2016-01”), was issued in January 2016 and provides revised guidance related to the accounting for and reporting of financial instruments. Some of the main provisions include: requiring most equity securities to be reported at fair value with unrealized gains and losses reported in the income statement; requiring separate presentation of financial assets and liabilities by measurement category and form (i.e. securities or loans); clarifying that entities must assess valuation allowances on a deferred tax asset related to available for sale debt securities in combination with their other deferred tax assets; and eliminating the requirement to disclose the method and significant assumptions used to estimate fair value for financial instruments measured at amortized cost on the balance sheet. ASU 2016-01 is effective for annual periods, and interim periods within those annual periods, beginning after December 15, 2017. The adoption of ASU 2016-01 is not expected to have a material impact on the Corporation’s consolidated financial statements. Leases - Topic 842 Accounting Standards Update No. 2016-02, “Leases” (“ASU 2016-02”), was issued in February 2016 and provides revised guidance related to the accounting and reporting of leases. ASU 2016-02 requires lessees to recognize most leases on the balance sheet. The recognition, measurement and presentation of expenses and cash flows arising from a lease by a lessee will depend on its classification as a finance or operating lease. ASU 2016-02 requires a modified retrospective transition, with a number of practical expedients that entities may elect to apply. ASU 2016-02 is effective for annual periods, and interim periods within those annual periods, beginning after December 15, 2018. Early adoption is permitted. Washington Trust expects to adopt the provisions of ASU 2016-02 effective January 1, 2019. Management has assembled a project team that meets regularly to evaluate the provisions of this ASU, identify additional data requirements necessary and determine an approach for implementation. The Corporation rents premises used in business operations under non-cancelable operating leases, which currently are not reflected in its Consolidated Balance Sheets. As disclosed in Note 21, the Corporation was committed to $39.3 million of minimum lease payments under these operating leases. The Corporation has not yet determined the impact ASU 2016-02 will have on its consolidated financial statements. Compensation - Stock Compensation - Topic 718 Accounting Standards Update No. 2016-09, “Improvements to Employee Share-Based Payment Accounting” (“ASU 2016-09”), was issued in March 2016. ASU 2016-09 includes multiple provisions intended to simplify several aspects of the accounting for share-based payment transactions, including income tax consequences and the classification of certain tax-related transactions on the statement of cash flows. ASU 2016-09 is effective for annual periods, and interim periods within those annual periods, beginning after December 15, 2016. Management adopted the provisions of this ASU on January 1, 2017 using the appropriate transition method as required by ASU 2016-09. For Washington Trust, the most significant provision of this ASU pertained to the accounting for excess tax benefits or tax deficiencies on share based award exercises and vestings. ASU 2016-09 requires that excess tax benefits or tax deficiencies be recognized as income tax benefit or expense in the Consolidated Statements of Income in the period that they occur. Management adopted this specific provision of the ASU on a prospective basis. The ASU also requires that the excess tax benefits or tax deficiencies be reported as an operating activity in the Consolidated Statements of Cash Flows and, in accordance with the ASU, management elected the retrospective transition method in adopting this specific provision. The adoption of ASU 2016-09 did not have a material impact on the consolidated financial statements. Financial Instruments - Credit Losses - Topic 326 Accounting Standards Update No. 2016-13, “Financial Instruments - Credit Losses” (“ASU 2016-13”), was issued in June 2016. ASU 2016-13 requires the measurement of all expected credit losses for financial assets held at the reporting date based on historical experience, current conditions, and reasonable and supportable forecasts and requires enhanced disclosures related to the significant estimates and judgments used in estimating credit losses, as well as the credit quality and underwriting standards of an organization’s portfolio. In addition, ASU 2016-13 amends the accounting for credit losses on available-for-sale debt securities and purchased financial assets with credit deterioration. ASU 2016-13 provides for a modified retrospective transition, resulting in a cumulative-effect adjustment to equity as of the beginning of the period in which the guidance is effective, except for debt securities for which an other-than-temporary impairment has previously been recognized. For these debt securities, a prospective transition approach will be adopted in order to maintain the same amortized cost prior to and subsequent to the effective date of ASU 2016-13. This ASU is effective for annual periods, and interim periods within those annual periods, beginning after December 15, 2019. Early adoption is permitted, for annual periods and interim periods within those annual periods, beginning after December 15, 2018. Washington Trust is evaluating the effect that this ASU will have on consolidated financial statements and disclosures. Management has assembled a project team that meets regularly to evaluate the provisions of this ASU, identify additional data requirements necessary and determine an approach for implementation. The Corporation has not yet determined if it will early adopt ASU 2016-13 or the impact it will have on its consolidated financial statements. Statement of Cash Flows - Topic 230 Accounting Standards Update No. 2016-15, “Classification of Certain Cash Receipts and Cash Payments” (“ASU 2016-15”), was issued in August 2016. ASU 2016-15 provides classification guidance on certain cash receipts and cash payments, including, but not limited to, debt prepayment costs, contingent consideration payments made after a business combination, proceeds from the settlement of insurance claims, proceeds from the settlement of bank-owned life insurance policies and distributions received from equity method investees. The adoption of ASU 2016-15 requires a retrospective transition method applied to each period presented. This ASU is effective for annual periods, and interim periods within those annual periods, beginning after December 15, 2017. Early adoption is permitted. The adoption of ASU 2016-15 is not expected to have a material impact on the Corporation’s consolidated financial statements. Accounting Standards Update No. 2016-18, “Restricted Cash” (“ASU 2016-18”), was issued in November 2016. ASU 2016-18 requires that a statement of cash flows explain the change during the period in the total of cash, cash equivalents and amounts generally described as restricted cash. Restricted cash should be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. The adoption of ASU 2016-18 requires a retrospective transition method applied to each period presented. This ASU is effective for annual periods, and interim periods within those annual periods, beginning after December 15, 2017. Early adoption is permitted. The adoption of ASU 2016-18 is not expected to have a material impact on the Corporation’s consolidated financial statements. Intangibles - Goodwill and Other - Topic 350 Accounting Standards Update No. 2017-04, “Simplifying the Test for Goodwill Impairment” (“ASU 2017-04”), was issued in January 2017 and eliminates Step 2 of the annual goodwill impairment test. Step 2 is a more detailed analysis, which involves measuring the excess of the fair value of the reporting unit, as determined in Step 1, over the aggregate fair value of the individual assets, liabilities, and identifiable intangibles as if the reporting unit was being acquired in a business combination. Under ASU 2017-04, an impairment charge would be recognized for the amount by which the carrying amount exceeded the reporting unit’s fair value under Step 1. ASU 2017-04 is effective for annual periods, and interim periods within those annual periods, beginning after December 15, 2019 and the provisions should be applied on a prospective basis. Effective April 1, 2017, management early adopted the provisions of this ASU, as permitted. The adoption of ASU 2017-04 did not have a material impact on the Corporation’s consolidated financial statements. Compensation - Retirement Benefits - Topic 715 Accounting Standards Update No. 2017-07, “Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost” (“ASU 2017-07”), was issued in March 2017. ASU 2017-07 requires that employers include the service cost component of net periodic benefit cost in the same line item as other employee compensation costs and all other components of net periodic benefit cost in a separate line item(s) in the statement of income. In addition, the line item in which the components of net periodic benefit cost other than the service cost are included shall be identified as such on the statement of income or in the notes to the financial statements. ASU 2017-07 is effective for annual periods, and interim periods within those annual periods, beginning after December 15, 2017. The adoption of ASU 2017-07 is not expected to have a material impact on the Corporation’s consolidated financial statements. Receivables - Nonrefundable Fees and Other Costs - Topic 310 Accounting Standards Update No. 2017-08, “Premium Amortization on Purchased Callable Debt Securities” (“ASU 2017-08”), was issued in March 2017. ASU 2017-08 shortens the amortization period for certain callable debt securities purchased at a premium by requiring that the premium be amortized to the earliest call date. Effective January 1, 2017, management early adopted the provisions of this ASU, as permitted. The adoption of ASU 2017-08 did not have a material impact on the Corporation’s consolidated financial statements. Compensation - Stock Compensation - Topic 718 Accounting Standards Update No. 2017-09, “Scope of Modification Accounting” (“ASU 2017-09”), was issued in May 2017 to provide clarity when applying the guidance in Topic 718 to a change to the terms or conditions of a share-based payment award. ASU 2017-09 is effective for annual periods, and interim periods within those annual periods, beginning after December 15, 2017 and the provisions should be applied on a prospective basis. Early adoption is permitted. The adoption of ASU 2017-09 is not expected to have a material impact on the Corporation’s consolidated financial statements. Derivatives and Hedging - Topic 815 Accounting Standards Update No. 2017-12, “Targeted Improvements to Accounting for Hedging Activities” (“ASU 2017-12”), was issued in August 2017 to better align financial reporting for hedging activities with the economic objectives of those activities. ASU 2017-12 is effective for fiscal years beginning after December 15, 2018, with early adoption, including adoption in an interim period, permitted. The provisions of ASU 2017-12 should be applied on a modified retrospective transition method in which the Corporation will recognize the cumulative effect of the change in the opening balance of retained earnings as of the adoption date. The Corporation has not yet determined the impact ASU 2017-12 will have on its consolidated financial statements. Comprehensive Income - Topic 220 Accounting Standards Update No. 2018-02, “Income Statement-Reporting Comprehensive Income: Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income” (“ASU 2018-02”), was issued in February 2018 to address accounting and regulatory capital reporting issues pertaining to income tax effects “stranded” in accumulated other comprehensive income as a result of the enactment of the Tax Act. ASU 2018-02 provided companies with the option to reclassify amounts specifically related to the Tax Act “stranded” in accumulated other comprehensive income to retained earnings. The Corporation elected to reclassify such amounts and early adopted ASU 2018-02, as permitted. The provisions of ASU 2018-02 were applied retrospectively to December 2017, the period in which the effects of the enactment of the Tax Act were recognized. As a result of the adoption of ASU 2018-02 and as reflected in the Consolidated Statements of Changes in Shareholders’ Equity, the Corporation reclassified $4.2 million from accumulated other comprehensive income to retained earnings. See Note 19 for further details.

Cash and Due from Banks

Cash and Due from Banks	12 Months Ended
	Dec. 31, 2017
Cash and Cash Equivalents [Abstract]
Cash and Due from Banks	Cash and Due from Banks The Bank maintains certain average reserve balances to meet the requirements of the Board of Governors of the Federal Reserve System (“FRB”). Some or all of these reserve requirements may be satisfied with vault cash. Reserve balances amounted to $14.1 million and $11.5 million , respectively, at December 31, 2017 and 2016 and were included in cash and due from banks in the Consolidated Balance Sheets. As of December 31, 2017 and 2016 , cash and due from banks includes interest-bearing deposits in other banks of $31.9 million and $60.3 million , respectively.

Securities

Securities	12 Months Ended
	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Securities	Securities The following tables present the amortized cost, gross unrealized holding gains, gross unrealized holding losses and fair value of securities by major security type and class of security: (Dollars in thousands) December 31, 2017 Amortized Cost Unrealized Gains Unrealized Losses Fair Value Securities Available for Sale: Obligations of U.S. government-sponsored enterprises $161,479 $— ($3,875 ) $157,604 Mortgage-backed securities issued by U.S. government agencies and U.S. government-sponsored enterprises 594,944 3,671 (7,733 ) 590,882 Obligations of states and political subdivisions 2,355 4 — 2,359 Individual name issuer trust preferred debt securities 18,106 — (1,122 ) 16,984 Corporate bonds 13,917 13 (805 ) 13,125 Total securities available for sale $790,801 $3,688 ($13,535 ) $780,954 Held to Maturity: Mortgage-backed securities issued by U.S. government agencies and U.S. government-sponsored enterprises $12,541 $180 $— $12,721 Total securities held to maturity 12,541 180 — 12,721 Total securities $803,342 $3,868 ($13,535 ) $793,675 (Dollars in thousands) December 31, 2016 Amortized Cost Unrealized Gains Unrealized Losses Fair Value Securities Available for Sale: Obligations of U.S. government-sponsored enterprises $111,483 $7 ($3,050 ) $108,440 Mortgage-backed securities issued by U.S. government agencies and U.S. government-sponsored enterprises 592,833 4,923 (9,671 ) 588,085 Obligations of states and political subdivisions 14,423 62 — 14,485 Individual name issuer trust preferred debt securities 29,851 — (3,115 ) 26,736 Corporate bonds 2,155 16 (5 ) 2,166 Total securities available for sale $750,745 $5,008 ($15,841 ) $739,912 Held to Maturity: Mortgage-backed securities issued by U.S. government agencies and U.S. government-sponsored enterprises $15,633 $287 $— $15,920 Total securities held to maturity 15,633 287 — 15,920 Total securities $766,378 $5,295 ($15,841 ) $755,832 At December 31, 2017 and 2016 , securities with a fair value of $357.8 million and $736.2 million , respectively, were pledged as collateral for Federal Home Loan Bank of Boston (“FHLBB”) borrowings, potential borrowings with the FRB, certain public deposits and for other purposes. See Note 11 for additional discussion of FHLB borrowings. The schedule of maturities of debt securities available for sale and held to maturity is presented below. Mortgage-backed securities are included based on weighted average maturities, adjusted for anticipated prepayments. All other debt securities are included based on contractual maturities. Actual maturities may differ from amounts presented because certain issuers have the right to call or prepay obligations with or without call or prepayment penalties. (Dollars in thousands) Available for Sale Held to Maturity December 31, 2017 Amortized Cost Fair Value Amortized Cost Fair Value Due in one year or less $62,120 $61,700 $1,719 $1,743 Due after one year to five years 247,054 244,392 5,374 5,451 Due after five years to ten years 285,543 280,870 4,019 4,077 Due after ten years 196,084 193,992 1,429 1,450 Total securities $790,801 $780,954 $12,541 $12,721 Included in the above table were debt securities with an amortized cost balance of $195.4 million and a fair value of $189.7 million at December 31, 2017 that are callable at the discretion of the issuers. Final maturities of the callable securities range from 5 months to 19 years, with call features ranging from 1 month to 4 years. Other-Than-Temporary Impairment Assessment Washington Trust assesses whether the decline in fair value of investment securities is other-than-temporary on a regular basis. Unrealized losses on debt securities may occur from current market conditions, increases in interest rates since the time of purchase, a structural change in an investment, volatility of earnings of a specific issuer, or deterioration in credit quality of the issuer. Management evaluates impairments in value both qualitatively and quantitatively to assess whether they are other-than-temporary. The following tables summarize temporarily impaired securities, segregated by length of time the securities have been in a continuous unrealized loss position: (Dollars in thousands) Less than 12 Months 12 Months or Longer Total December 31, 2017 # Fair Value Unrealized Losses # Fair Value Unrealized Losses # Fair Value Unrealized Losses Obligations of U.S. government-sponsored enterprises 8 $69,681 ($798 ) 8 $87,923 ($3,077 ) 16 $157,604 ($3,875 ) Mortgage-backed securities issued by U.S. government agencies and U.S. government-sponsored enterprises 20 128,965 (613 ) 22 279,693 (7,120 ) 42 408,658 (7,733 ) Individual name issuer trust preferred debt securities — — — 7 16,984 (1,122 ) 7 16,984 (1,122 ) Corporate bonds 3 921 (5 ) 3 10,980 (800 ) 6 11,901 (805 ) Total temporarily impaired securities 31 $199,567 ($1,416 ) 40 $395,580 ($12,119 ) 71 $595,147 ($13,535 ) (Dollars in thousands) Less than 12 Months 12 Months or Longer Total December 31, 2016 # Fair Value Unrealized Losses # Fair Value Unrealized Losses # Fair Value Unrealized Losses Obligations of U.S. government-sponsored enterprises 10 $98,433 ($3,050 ) — $— $— 10 $98,433 ($3,050 ) Mortgage-backed securities issued by U.S. government agencies and U.S. government-sponsored enterprises 35 407,073 (9,671 ) — — — 35 407,073 (9,671 ) Individual name issuer trust preferred debt securities — — — 10 26,736 (3,115 ) 10 26,736 (3,115 ) Corporate bonds 2 400 (5 ) — — — 2 400 (5 ) Total temporarily impaired securities 47 $505,906 ($12,726 ) 10 $26,736 ($3,115 ) 57 $532,642 ($15,841 ) Further deterioration in credit quality of the underlying issuers of the securities, further deterioration in the condition of the financial services industry, worsening of the current economic environment, or additional declines in real estate values, among other things, may further affect the fair value of these securities and increase the potential that certain unrealized losses be designated as other-than-temporary in future periods, and the Corporation may incur write-downs. U.S. Government Agency and U.S. Government-Sponsored Enterprise Securities, including Mortgage-Backed Securities The gross unrealized losses on U.S. government agency and U.S government-sponsored debt securities, including mortgage-backed securities, were primarily attributable to relative changes in interest rates since the time of purchase. The contractual cash flows for these securities are guaranteed by U.S. government agencies and U.S. government-sponsored enterprises. Based on the assessment of these factors, management believes that the unrealized losses on these debt security holdings are a function of changes in investment spreads and interest rate movements and not changes in credit quality. Management expects to recover the entire amortized cost basis of these securities. Furthermore, Washington Trust does not intend to sell these securities and it is not more-likely-than-not that Washington Trust will be required to sell these securities before recovery of their cost basis, which may be maturity. Therefore, management does not consider these investments to be other-than-temporarily impaired at December 31, 2017 . Trust Preferred Debt Securities of Individual Name Issuers Included in debt securities in an unrealized loss position at December 31, 2017 were seven trust preferred security holdings issued by five individual companies in the banking sector. Management believes the unrealized loss position in these holdings was attributable to the general widening of spreads for this category of debt securities issued by financial services companies since the time these securities were purchased. Based on the information available through the filing date of this report, all individual name trust preferred debt securities held in our portfolio continue to accrue and make payments as expected with no payment deferrals or defaults on the part of the issuers. As of December 31, 2017 , individual name issuers trust preferred debt securities with an amortized cost of $6.1 million and unrealized losses of $509 thousand were rated below investment grade by Standard & Poors, Inc. (“S&P”). Management reviewed the collectability of these securities taking into consideration such factors as the financial condition of the issuers, reported regulatory capital ratios of the issuers, credit ratings, including ratings in effect as of the reporting period date as well as credit rating changes between the reporting period date and the filing date of this report, and other information. We noted no downgrades to below investment grade between December 31, 2017 and the filing date of this report. Based on these analyses, management concluded that it expects to recover the entire amortized cost basis of these securities. Furthermore, Washington Trust does not intend to sell these securities and it is not more-likely-than-not that Washington Trust will be required to sell these securities before recovery of their cost basis, which may be maturity. Therefore, management does not consider these investments to be other-than-temporarily impaired at December 31, 2017 . Corporate Bonds At December 31, 2017 , Washington Trust had six corporate bond holdings with unrealized losses totaling $805 thousand . These investment grade corporate bonds were issued by large corporations. Management believes the unrealized losses on these bonds are a function of the changes in the investment spreads and interest rate movements and not changes in the credit quality of the issuers of the debt securities. Management expects to recover the entire amortized cost basis of these securities. Furthermore, Washington Trust does not intend to sell these securities and it is not more-likely-than-not that Washington Trust will be required to sell these securities before recovery of their cost basis, which may be maturity. Therefore, management does not consider these investments to be other-than-temporarily impaired at December 31, 2017 .

Loans

Loans	12 Months Ended
	Dec. 31, 2017
Receivables [Abstract]
Loans	Loans The following is a summary of loans: (Dollars in thousands) December 31, 2017 December 31, 2016 Amount % Amount % Commercial: Mortgages (1) $1,072,487 32 % $1,074,186 33 % Construction & development (2) 138,008 4 121,371 4 Commercial & industrial (3) 612,334 18 576,109 18 Total commercial 1,822,829 54 1,771,666 55 Residential real estate: Mortgages 1,206,458 35 1,094,824 34 Homeowner construction 20,790 1 27,924 1 Total residential real estate 1,227,248 36 1,122,748 35 Consumer: Home equity lines 258,114 8 264,200 8 Home equity loans 34,353 1 37,272 1 Other (4) 31,527 1 38,485 1 Total consumer 323,994 10 339,957 10 Total loans (5) $3,374,071 100 % $3,234,371 100 % (1) Loans primarily secured by income producing property. (2) Loans for construction of commercial properties, loans to developers for construction of residential properties and loans for land development. (3) Loans to businesses and individuals, a substantial portion of which are fully or partially collateralized by real estate. (4) Loans to individuals secured by general aviation aircraft and other personal installment loans. (5) Includes net unamortized loan origination costs of $3.8 million and $3.0 million , respectively, and net unamortized premiums on purchased loans of $878 thousand and $783 thousand , respectively, at December 31, 2017 and 2016 . At December 31, 2017 and 2016 , there were $1.6 billion and $1.4 billion , respectively, of loans pledged as collateral to the FHLB under a blanket pledge agreement and to the FRB for the discount window. See Note 11 for additional disclosure regarding borrowings. Concentrations of Credit Risk A significant portion of our loan portfolio is concentrated among borrowers in southern New England and a substantial portion of the portfolio is collateralized by real estate in this area. The ability of single family residential and consumer borrowers to honor their repayment commitments is generally dependent on the level of overall economic activity within the market area and real estate values. The ability of commercial borrowers to honor their repayment commitments is dependent on the general economy as well as the health of the real estate economic sector in the Corporation’s market area. Nonaccrual Loans The following is a summary of nonaccrual loans, segregated by class of loans: (Dollars in thousands) December 31, 2017 2016 Commercial: Mortgages $4,954 $7,811 Construction & development — — Commercial & industrial 283 1,337 Residential real estate: Mortgages 9,414 11,736 Homeowner construction — — Consumer: Home equity lines 81 — Home equity loans 463 1,058 Other 16 116 Total nonaccrual loans $15,211 $22,058 Accruing loans 90 days or more past due $— $— As of December 31, 2017 and 2016 , loans secured by one- to four-family residential property amounting to $4.4 million and $5.7 million , respectively, were in process of foreclosure. Nonaccrual loans of $3.4 million and $3.5 million , respectively, were current as to the payment of principal and interest as of December 31, 2017 and 2016 . There were no significant commitments to lend additional funds to borrowers whose loans were on nonaccrual status at December 31, 2017 . Interest income that would have been recognized had nonaccrual loans been current in accordance with their original terms was approximately $1.3 million , $1.6 million and $1.5 million in 2017 , 2016 and 2015 , respectively. Interest income included in the Consolidated Statements of Income on nonaccrual loans amounted to approximately $335 thousand , $640 thousand and $522 thousand , respectively, in 2017 , 2016 and 2015 . Past Due Loans Past due status is based on the contractual payment terms of the loan. The following tables present an aging analysis of past due loans, segregated by class of loans: (Dollars in thousands) Days Past Due December 31, 2017 30-59 60-89 Over 90 Total Past Due Current Total Loans Commercial: Mortgages $6 $— $4,954 $4,960 $1,067,527 $1,072,487 Construction & development — — — — 138,008 138,008 Commercial & industrial 3,793 2 281 4,076 608,258 612,334 Residential real estate: Mortgages 1,678 2,274 3,903 7,855 1,198,603 1,206,458 Homeowner construction — — — — 20,790 20,790 Consumer: Home equity lines 1,340 — — 1,340 256,774 258,114 Home equity loans 1,458 75 268 1,801 32,552 34,353 Other 29 — 14 43 31,484 31,527 Total loans $8,304 $2,351 $9,420 $20,075 $3,353,996 $3,374,071 (Dollars in thousands) Days Past Due December 31, 2016 30-59 60-89 Over 90 Total Past Due Current Total Loans Commercial: Mortgages $901 $— $7,807 $8,708 $1,065,478 $1,074,186 Construction & development — — — — 121,371 121,371 Commercial & industrial 409 — 745 1,154 574,955 576,109 Residential real estate: Mortgages 5,381 652 6,193 12,226 1,082,598 1,094,824 Homeowner construction — — — — 27,924 27,924 Consumer: Home equity lines 655 26 — 681 263,519 264,200 Home equity loans 776 76 658 1,510 35,762 37,272 Other 32 1 110 143 38,342 38,485 Total loans $8,154 $755 $15,513 $24,422 $3,209,949 $3,234,371 Included in past due loans as of December 31, 2017 and 2016 , were nonaccrual loans of $11.8 million and $18.6 million , respectively. All loans 90 days or more past due at December 31, 2017 and 2016 were classified as nonaccrual. Impaired Loans Impaired loans are loans for which it is probable that the Corporation will not be able to collect all amounts due according to the contractual terms of the loan agreements and loans restructured in a troubled debt restructuring. The following is a summary of impaired loans: (Dollars in thousands) Recorded Investment (1) Unpaid Principal Related Allowance December 31, 2017 2016 2017 2016 2017 2016 No Related Allowance Recorded: Commercial: Mortgages $— $4,676 $— $9,019 $— $— Construction & development — — — — — — Commercial & industrial 4,986 6,458 5,081 6,550 — — Residential real estate: Mortgages 9,069 14,385 9,256 14,569 — — Homeowner construction — — — — — — Consumer: Home equity lines 81 — 81 — — — Home equity loans 476 1,137 476 1,177 — — Other 14 116 14 116 — — Subtotal 14,626 26,772 14,908 31,431 — — With Related Allowance Recorded: Commercial: Mortgages 4,954 5,104 9,910 6,087 1,018 448 Construction & development — — — — — — Commercial & industrial 191 662 212 699 1 3 Residential real estate: Mortgages 715 1,285 741 1,310 104 151 Homeowner construction — — — — — — Consumer: Home equity lines — — — — — — Home equity loans — — — — — — Other 133 28 132 29 6 4 Subtotal 5,993 7,079 10,995 8,125 1,129 606 Total impaired loans $20,619 $33,851 $25,903 $39,556 $1,129 $606 Total: Commercial $10,131 $16,900 $15,203 $22,355 $1,019 $451 Residential real estate 9,784 15,670 9,997 15,879 104 151 Consumer 704 1,281 703 1,322 6 4 Total impaired loans $20,619 $33,851 $25,903 $39,556 $1,129 $606 (1) The recorded investment in impaired loans consists of unpaid principal balance, net of charge-offs, interest payments received applied to principal and unamortized deferred loan origination fees and costs. For accruing impaired loans (troubled debt restructurings for which management has concluded that the collectability of the loan is not in doubt), the recorded investment also includes accrued interest. The following table presents the average recorded investment balance of impaired loans and interest income recognized on impaired loans segregated by loan class: (Dollars in thousands) Average Recorded Investment Interest Income Recognized Years ended December 31, 2017 2016 2015 2017 2016 2015 Commercial: Mortgages $8,425 $13,201 $14,847 $79 $239 $327 Construction & development — — — — — — Commercial & industrial 6,445 3,540 3,415 281 99 130 Residential real estate: Mortgages 14,571 12,848 5,423 444 322 147 Homeowner construction — — — — — — Consumer: Home equity lines 79 354 228 7 10 1 Home equity loans 606 1,233 487 24 38 11 Other 143 147 210 10 11 10 Totals $30,269 $31,323 $24,610 $845 $719 $626 Troubled Debt Restructurings Troubled debt restructurings are classified as impaired loans. The Corporation identifies loss allocations for impaired loans on an individual loan basis. The recorded investment in troubled debt restructurings was $11.2 million and $22.3 million , respectively, at December 31, 2017 and 2016 . These amounts included insignificant balances of accrued interest. The allowance for loan losses included specific reserves for these troubled debt restructurings of $1.1 million and $567 thousand , respectively, at December 31, 2017 and 2016 . As of December 31, 2017 , there were no significant commitments to lend additional funds to borrowers whose loans were restructured. The following table presents loans modified as a troubled debt restructuring: (Dollars in thousands) Outstanding Recorded Investment (1) # of Loans Pre-Modifications Post-Modifications Years ended December 31, 2017 2016 2017 2016 2017 2016 Commercial: Mortgages — 1 $— $776 $— $776 Construction & development — — — — — — Commercial & industrial — 9 — 6,229 — 6,229 Residential real estate: Mortgages — 3 — 4,386 — 4,386 Homeowner construction — — — — — — Consumer: Home equity lines — — — — — — Home equity loans — — — — — — Other — — — — — — Totals — 13 $— $11,391 $— $11,391 (1) The recorded investment in troubled debt restructurings consists of unpaid principal balance, net of charge-offs and unamortized deferred loan origination fees and costs, at the time of the restructuring. For accruing troubled debt restructured loans, the recorded investment also includes accrued interest. The following table provides information on how loans were modified as a troubled debt restructuring: (Dollars in thousands) Years ended December 31, 2017 2016 Below-market interest rate concession $— $— Payment deferral — 1,111 Maturity / amortization concession — 683 Interest only payments — 4,326 Combination (1) — 5,271 Total $— $11,391 (1) Loans included in this classification were modified with a combination of any two of the concessions listed in this table. In 2017 , there were no payment defaults on troubled debt restructured loans modified within the previous 12 months. In 2016 , payment defaults on troubled debt restructured loans modified within the previous 12 months occurred on seven loans totaling $1.6 million . Credit Quality Indicators Commercial The Corporation utilizes an internal rating system to assign a risk to each of its commercial loans. Loans are rated on a scale of 1 to 10. This scale can be assigned to three broad categories including “pass” for ratings 1 through 6, “special mention” for 7-rated loans, and “classified” for loans rated 8, 9 or 10. The loan rating system takes into consideration parameters including the borrower’s financial condition, the borrower’s performance with respect to loan terms, the adequacy of collateral, the adequacy of guarantees and other credit quality characteristics. As of December 31, 2017 and 2016 , the weighted average risk rating of the Corporation’s commercial loan portfolio was 4.70 and 4.68 , respectively. For non-impaired loans, the Corporation takes the risk rating into consideration along with other credit attributes in the establishment of an appropriate allowance for loan losses. See Note 6 for additional information. A description of the commercial loan categories is as follows: Pass - Loans with acceptable credit quality, defined as ranging from superior or very strong to a status of lesser stature. Superior or very strong credit quality is characterized by a high degree of cash collateralization or strong balance sheet liquidity. Lesser stature loans have an acceptable level of credit quality but exhibit some weakness in various credit metrics such as collateral adequacy, cash flow, secondary sources of repayment, or performance inconsistency or may be in an industry or of a loan type known to have a higher degree of risk. Special Mention - Loans with potential weaknesses that deserve management’s close attention. If left uncorrected, these potential weaknesses may result in deterioration of the repayment prospects for the asset or in the Bank’s position as creditor at some future date. Special Mention assets are not adversely classified and do not expose the Bank to sufficient risk to warrant adverse classification. Examples of these conditions include but are not limited to outdated or poor quality financial data, strains on liquidity and leverage, losses or negative trends in operating results, marginal cash flow, weaknesses in occupancy rates or trends in the case of commercial real estate and frequent delinquencies. Classified - Loans identified as “substandard,” “doubtful” or “loss” based on criteria consistent with guidelines provided by banking regulators. A “substandard” loan has defined weaknesses which make payment default or principal exposure likely, but not yet certain. Such loans are apt to be dependent upon collateral liquidation, a secondary source of repayment or an event outside of the normal course of business. The loans are closely watched and are either already on nonaccrual status or may be placed on nonaccrual status when management determines there is uncertainty of collectibility. A “doubtful” loan is placed on nonaccrual status and has a high probability of loss, but the extent of the loss is difficult to quantify due to dependency upon collateral having a value that is difficult to determine or upon some near-term event which lacks certainty. A loan in the “loss” category is considered generally uncollectible or the timing or amount of payments cannot be determined. “Loss” is not intended to imply that the loan has no recovery value but rather it is not practical or desirable to continue to carry the asset. The Corporation’s procedures call for loan ratings and classifications to be revised whenever information becomes available that indicates a change is warranted. The criticized loan portfolio, which generally consists of commercial loans that are risk-rated special mention or worse, and other selected loans are reviewed by management on a quarterly basis, focusing on the current status and strategies to improve the credit. An annual loan review program is conducted by a third party to provide an independent evaluation of the creditworthiness of the commercial loan portfolio, the quality of the underwriting and credit risk management practices and the appropriateness of the risk rating classifications. This review is supplemented with selected targeted internal reviews of the commercial loan portfolio. The following table presents the commercial loan portfolio, segregated by category of credit quality indicator: (Dollars in thousands) Pass Special Mention Classified December 31, 2017 2016 2017 2016 2017 2016 Mortgages $1,067,373 $1,065,358 $— $776 $5,114 $8,052 Construction & development 138,008 121,371 — — — — Commercial & industrial 592,749 559,416 9,804 8,938 9,781 7,755 Total commercial loans $1,798,130 $1,746,145 $9,804 $9,714 $14,895 $15,807 Residential and Consumer The residential and consumer portfolios are monitored on an ongoing basis by the Corporation using delinquency information and loan type as credit quality indicators. These credit quality indicators are assessed on an aggregate basis in these relatively homogeneous portfolios. For non-impaired loans, the Corporation assigns loss allocation factors to each respective loan type. See Note 6 for additional information. Various other techniques are utilized to monitor indicators of credit deterioration in the portfolios of residential real estate mortgages and home equity lines and loans. Among these techniques is the periodic tracking of loans with an updated FICO score and an estimated loan to value (“LTV”) ratio. LTV ratio is determined via statistical modeling analyses. The indicated LTV levels are estimated based on such factors as the location, the original LTV ratio, and the date of origination of the loan and do not reflect actual appraisal amounts. The results of these analyses and other loan review procedures are taken into consideration in the determination of loss allocation factors for residential mortgage and home equity consumer credits. See Note 6 for additional information. The following table presents the residential and consumer loan portfolios, segregated by category of credit quality indicator: (Dollars in thousands) Current Past Due December 31, 2017 2016 2017 2016 Residential real estate: Self-originated mortgages $1,070,501 $954,867 $6,413 $11,017 Purchased mortgages 128,102 127,731 1,442 1,209 Homeowner construction 20,790 27,924 — — Total residential loans $1,219,393 $1,110,522 $7,855 $12,226 Consumer: Home equity lines $256,774 $263,519 $1,340 $681 Home equity loans 32,552 35,762 1,801 1,510 Other 31,484 38,342 43 143 Total consumer loans $320,810 $337,623 $3,184 $2,334 Loan Servicing Activities Loans sold with servicing retained result in the capitalization of loan servicing rights. The following table presents an analysis of loan servicing rights: (Dollars in thousands) Loan Servicing Rights Valuation Allowance Total Balance at December 31, 2014 $2,989 ($2 ) $2,987 Loan servicing rights capitalized 1,406 — 1,406 Amortization (1,047 ) — (1,047 ) Decrease in impairment reserve — 1 1 Balance at December 31, 2015 3,348 (1 ) 3,347 Loan servicing rights capitalized 1,412 — 1,412 Amortization (1,267 ) — (1,267 ) Decrease in impairment reserve — 1 1 Balance at December 31, 2016 3,493 — 3,493 Loan servicing rights capitalized 1,104 — 1,104 Amortization (984 ) — (984 ) Decrease in impairment reserve — — — Balance at December 31, 2017 $3,613 $— $3,613 The following table presents estimated aggregate amortization expense related to loan servicing assets: (Dollars in thousands) Years ending December 31: 2018 $899 2019 675 2020 507 2021 381 2022 286 Thereafter 865 Total estimated amortization expense $3,613 Loans sold to others are serviced on a fee basis under various agreements. Loans serviced for others are not included in the Consolidated Balance Sheets. The following table presents the balance of loans serviced for others by type of loan: (Dollars in thousands) December 31, 2017 2016 Residential mortgages $568,311 $522,766 Commercial loans 108,539 101,317 Total $676,850 $624,083

Allowance for Loan Losses

Allowance for Loan Losses	12 Months Ended
	Dec. 31, 2017
Receivables [Abstract]
Allowance for Loan Losses	Allowance for Loan Losses The allowance for loan losses is management’s best estimate of inherent risk of loss in the loan portfolio as of the balance sheet date. The Corporation uses a methodology to systematically measure the amount of estimated loan loss exposure inherent in the loan portfolio for purposes of establishing a sufficient allowance for loan losses. The methodology includes: (1) the identification of loss allocations for individual loans deemed to be impaired and (2) the application of loss allocation factors for non-impaired loans based on historical loss experience and estimated loss emergence period, with adjustments for various exposures that management believes are not adequately represented by historical loss experience. Prior to December 31, 2015, an unallocated allowance was maintained for measurement imprecision associated with impaired and nonaccrual loans. As a result of further enhancement and refinement of the allowance methodology to provide a more precise quantification of probable losses in the loan portfolio, management concluded that the potential risks anticipated by the unallocated allowance had been incorporated into the allocated component of the methodology, eliminating the need for the unallocated allowance in the fourth quarter of 2015. The following table presents the activity in the allowance for loan losses for the year ended December 31, 2017 : (Dollars in thousands) Commercial Mortgages Construction C&I (1) Total Commercial Residential Consumer Total Beginning Balance $9,971 $1,195 $6,992 $18,158 $5,252 $2,594 $26,004 Charge-offs (1,867 ) — (336 ) (2,203 ) (74 ) (185 ) (2,462 ) Recoveries 82 — 169 251 39 56 346 Provision 3,460 (112 ) (1,245 ) 2,103 210 287 2,600 Ending Balance $11,646 $1,083 $5,580 $18,309 $5,427 $2,752 $26,488 (1) Commercial & industrial loans. The following table presents the activity in the allowance for loan losses for the year ended December 31, 2016 : (Dollars in thousands) Commercial Mortgages Construction C&I (1) Total Commercial Residential Consumer Total Beginning Balance $9,140 $1,758 $8,202 $19,100 $5,460 $2,509 $27,069 Charge-offs (5,816 ) — (759 ) (6,575 ) (200 ) (237 ) (7,012 ) Recoveries 56 — 156 212 11 74 297 Provision 6,591 (563 ) (607 ) 5,421 (19 ) 248 5,650 Ending Balance $9,971 $1,195 $6,992 $18,158 $5,252 $2,594 $26,004 (1) Commercial & industrial loans. The following table presents the activity in the allowance for loan losses for the year ended December 31, 2015 : (Dollars in thousands) Commercial Mortgages Construction C&I (1) Total Commercial Residential Consumer Unallocated Total Beginning Balance $8,202 $1,300 $7,987 $17,489 $5,430 $2,713 $2,391 $28,023 Charge-offs (809 ) — (671 ) (1,480 ) (207 ) (618 ) — (2,305 ) Recoveries 92 — 87 179 28 94 — 301 Provision 1,655 458 799 2,912 209 320 (2,391 ) 1,050 Ending Balance $9,140 $1,758 $8,202 $19,100 $5,460 $2,509 $— $27,069 (1) Commercial & industrial loans. The following table presents the Corporation’s loan portfolio and associated allowance for loan losses by portfolio segment and by impairment methodology. (Dollars in thousands) December 31, 2017 December 31, 2016 Related Allowance Related Allowance Loans Loans Loans Individually Evaluated For Impairment: Commercial: Mortgages $4,954 $1,018 $9,776 $448 Construction & development — — — — Commercial & industrial 5,157 1 7,098 3 Residential Real Estate 9,783 104 15,661 151 Consumer 704 6 1,280 4 Subtotal 20,598 1,129 33,815 606 Loans Collectively Evaluated For Impairment: Commercial: Mortgages 1,067,533 10,628 1,064,410 9,523 Construction & development 138,008 1,083 121,371 1,195 Commercial & industrial 607,177 5,579 569,011 6,989 Residential Real Estate 1,217,465 5,323 1,107,087 5,101 Consumer 323,290 2,746 338,677 2,590 Subtotal 3,353,473 25,359 3,200,556 25,398 Total $3,374,071 $26,488 $3,234,371 $26,004

Premises and Equipment

Premises and Equipment	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Premises and Equipment	Premises and Equipment The following presents a summary of premises and equipment: (Dollars in thousands) December 31, 2017 2016 Land and improvements $6,020 $6,020 Premises and improvements 38,793 37,913 Furniture, fixtures and equipment 26,240 28,383 Total premises and equipment 71,053 72,316 Less accumulated depreciation 42,720 43,296 Total premises and equipment, net $28,333 $29,020 Depreciation of premises and equipment amounted to $3.5 million , $3.7 million and $3.4 million , respectively, for the years ended December 31, 2017 , 2016 , and 2015 .

Goodwill and Other Intangibles

Goodwill and Other Intangibles	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangibles	Goodwill and Other Intangibles The following table presents the carrying value of goodwill at the reporting unit (or business segment) level: (Dollars in thousands) Commercial Banking Wealth Management Services Total Balance at December 31, 2016 $22,591 $41,468 $64,059 Impairment — (150 ) (150 ) Balance at December 31, 2017 $22,591 $41,318 $63,909 The balance of goodwill in the Commercial Banking segment arose from the acquisition of First Financial Corp. in 2002. The balance of goodwill in the Wealth Management Services segment arose from the 2005 acquisition of Weston Financial and its broker-dealer and insurance agency subsidiaries, as well as the 2015 acquisition of Halsey. As the result of a decision that reduced the business activities of WSC, a broker-dealer subsidiary that largely conducted mutual fund transactions primarily for Weston Financial clients, the carrying value of WSC’s goodwill was assessed for impairment during the second quarter of 2017 . As a result of management’s assessment, an impairment charge of $150 thousand was recognized in the second quarter of 2017 and classified in other expenses in the Consolidated Statements of Income. Intangible assets consist of wealth management advisory contracts and non-compete agreements. The following table presents the components of intangible assets: (Dollars in thousands) December 31, 2017 December 31, 2016 Advisory Contracts Non-compete Agreements Advisory Contracts Non-compete Agreements Gross carrying amount $20,803 $369 $20,803 $369 Accumulated amortization 11,663 369 10,648 349 Net amount $9,140 $— $10,155 $20 The balance of intangible assets at December 31, 2017 includes wealth management advisory contracts resulting from the Weston Financial acquisition in 2005, as well as wealth management advisory contracts resulting from the acquisition of Halsey in 2015. The wealth management advisory contracts resulting from the Weston Financial acquisition are being amortized over a 20 -year life using a declining balance method, based on expected attrition for the current customer base derived from historical runoff data. The wealth management advisory contracts resulting from the acquisition of Halsey are being amortized on a straight-line basis over a 15 -year life. Amortization expense for the years ended December 31, 2017 , 2016 , and 2015 , amounted to $1.0 million , $1.3 million and $904 thousand , respectively. The following table presents estimated annual amortization expense for intangible assets at December 31, 2017 : (Dollars in thousands) Years ending December 31, 2018 $979 2019 943 2020 914 2021 890 2022 860 2023 and thereafter 4,554

Income Tax Expense

Income Tax Expense	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Tax Expense	Income Tax Expense On December 22, 2017, the Tax Act was signed into law. The enactment of the Tax Act in 2017 required companies to revalue and reassess deferred tax assets and liabilities reflecting the new federal income tax rate. As a result, in December 2017, Washington Trust's net deferred tax assets were written down by $6.2 million , with a corresponding increase to income tax expense. The majority of the provisions of the Tax Act will take effect on January 1, 2018. The provisions that impact Washington Trust include the reduction of the corporate income tax rate from 35% to 21%, changes to the deductibility of certain meals and entertainment expenses, and changes to the deductibility of executive compensation. The Tax Act also accelerates expensing of certain depreciable property for assets placed in service after September 27, 2017 and before January 1, 2023. Effective January 1, 2017, Washington Trust adopted Accounting Standards Update No. 2016-09, "Improvements to Employee Share-Based Payment Accounting." Under this accounting standard, excess tax benefits on the settlement of share-based awards are recognized as a reduction to income tax expense in the period that they occur. In 2017, income tax expense was reduced by the recognition of $508 thousand in excess tax benefits on the settlement of share-based awards. Prior to 2017, such excess tax benefits were recognized as additional paid in capital in shareholders' equity and did not impact income tax expense. The following table presents the components of income tax expense: (Dollars in thousands) Years ended December 31, 2017 2016 2015 Current tax expense: Federal $23,827 $19,444 $17,864 State 2,201 2,061 1,194 Total current tax expense 26,028 21,505 19,058 Deferred tax expense (benefit): Federal 5,717 796 2,003 State (30 ) 72 (183 ) Total deferred tax expense 5,687 868 1,820 Total income tax expense $31,715 $22,373 $20,878 Total income tax expense varies from the amount determined by applying the Federal income tax rate to income before income taxes. The following table presents the reasons for the differences: (Dollars in thousands) Years ended December 31, 2017 2016 2015 Tax expense at Federal statutory rate $27,174 $24,099 $22,520 (Decrease) increase in taxes resulting from: Tax-exempt income (1,313 ) (1,599 ) (1,604 ) Dividends received deduction (55 ) (58 ) (57 ) BOLI (757 ) (930 ) (694 ) Stock based compensation (481 ) — — Federal tax credits (364 ) (364 ) (364 ) Change in fair value of contingent consideration (225 ) (314 ) — Acquisition related expenses — — 318 State income tax expense, net of federal income tax benefit 1,411 1,387 658 Adjustment to net deferred tax assets for enacted changes in federal tax law 6,170 — — Other 155 152 101 Total income tax expense $31,715 $22,373 $20,878 The following table presents the approximate tax effects of temporary differences that give rise to deferred tax assets and deferred tax liabilities: (Dollars in thousands) December 31, 2017 2016 Deferred tax assets: Allowance for loan losses $6,225 $9,621 Defined benefit pension obligations 1,767 3,804 Deferred compensation 3,334 3,991 Deferred loan origination fees 1,325 1,999 Stock based compensation 1,240 1,519 Net unrealized losses on securities available for sale 2,314 4,008 Other 2,281 3,495 Deferred tax assets 18,486 28,437 Deferred tax liabilities: Amortization of intangibles (2,148 ) (3,765 ) Deferred loan origination costs (3,550 ) (5,156 ) Loan servicing rights (849 ) (1,293 ) Other (1,200 ) (1,419 ) Deferred tax liabilities (7,747 ) (11,633 ) Net deferred tax asset $10,739 $16,804 The Corporation’s net deferred tax asset is included in other assets in the Consolidated Balance Sheets. Management has determined that a valuation allowance is not required for any of the deferred tax assets since it is more-likely-than-not that these assets will be realized primarily through future reversals of existing taxable temporary differences or by offsetting projected future taxable income. The Corporation had no unrecognized tax benefits as of December 31, 2017 and 2016 . The Corporation files income tax returns in the U.S. federal jurisdiction and various state jurisdictions. The Corporation is no longer subject to U.S. federal and state income tax examinations by tax authorities for years before 2014 .

Time Certificates of Deposit

Time Certificates of Deposit	12 Months Ended
	Dec. 31, 2017
Deposits [Abstract]
Time Certificates of Deposit	Time Certificates of Deposit The following table presents scheduled maturities of time certificates of deposit: (Dollars in thousands) Scheduled Maturity Weighted Average Rate Years ending December 31: 2018 $479,914 0.96 % 2019 323,597 1.51 2020 90,282 1.54 2021 59,263 1.77 2022 61,991 1.94 2023 and thereafter 48 1.30 Balance at December 31, 2017 $1,015,095 1.30 % The following table presents the amount of time certificates of deposit in denominations of $100 thousand or more at December 31, 2017 , maturing during the periods indicated: (Dollars in thousands) January 1, 2018 to March 31, 2018 $100,142 April 1, 2018 to June 30, 2018 21,824 July 1, 2018 to December 31, 2018 35,239 January 1, 2019 and beyond 172,083 Balance at December 31, 2017 $329,288 Time certificates of deposit in denominations of $250 thousand or more totaled $75.1 million and $53.4 million , respectively, at December 31, 2017 and 2016 .

Borrowings

Borrowings	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Borrowings	Borrowings Federal Home Loan Bank Advances Advances payable to FHLB amounted to $791.4 million and $848.9 million , respectively, at December 31, 2017 and 2016 . The following table presents scheduled maturities and weighted average interest rates on FHLB advances outstanding as of December 31, 2017 : (Dollars in thousands) Scheduled Maturity Weighted Average Rate 2018 $465,634 1.51 % 2019 137,258 1.62 2020 67,033 1.95 2021 51,222 2.43 2022 55,447 3.58 2023 and thereafter 14,762 2.44 Total $791,356 1.85 % As of December 31, 2017 and 2016 , the Bank had access to a $40.0 million unused line of credit with the FHLB and also had remaining available borrowing capacity of $449.9 million and $594.5 million , respectively. The Bank pledges certain qualified investment securities and loans as collateral to the FHLB. Advances payable to FHLB include short-term advances with original maturity due dates of one year or less. The following table presents certain information concerning short-term FHLB advances: (Dollars in thousands) As of and for the years ended December 31, 2017 2016 2015 Average amount outstanding during the period $351,692 $275,533 $155,874 Amount outstanding at end of period $367,500 $352,500 $107,500 Highest month end balance during period $417,500 $367,500 $229,500 Weighted-average interest rate at end of period 1.57 % 0.79 % 0.55 % Weighted-average interest rate during the period 1.20 % 0.73 % 0.38 % Junior Subordinated Debentures Junior subordinated debentures amounted to $22.7 million at December 31, 2017 and 2016 . The Bancorp sponsored the creation of WT Capital Trust I (“Trust I”) and WT Capital Trust II (“Trust II”), Delaware statutory trusts created for the sole purpose of issuing trust preferred securities and investing the proceeds in junior subordinated debentures of the Bancorp. The Bancorp is the owner of all of the common securities of the trusts. In accordance with GAAP, the trusts are treated as unconsolidated subsidiaries. The common stock investment in the statutory trusts is included in “Other Assets” in the Consolidated Balance Sheet. On August 29, 2005, Trust I issued $8.3 million of capital securities (“Trust I Capital Securities”) in a private placement of trust preferred securities. The Trust I Capital Securities mature in September 2035, are redeemable at the Bancorp’s option and require quarterly distributions by Trust I to the holder of the Trust I Capital Securities equal to the three-month LIBOR rate plus 1.45% . The Bancorp has guaranteed the Trust I Capital Securities and, to the extent not paid by Trust I, accrued and unpaid distributions on the Trust I Capital Securities, as well as the redemption price payable to the Trust I Capital Securities holders. The proceeds of the Trust I Capital Securities, along with proceeds from the issuance of common securities by Trust I to the Bancorp, were used to purchase $8.3 million of the Bancorp’s junior subordinated deferrable interest notes (the “Trust I Debentures”) and constitute the primary asset of Trust I. Like the Trust I Capital Securities, the Trust I Debentures bear interest at a rate equal to the three-month LIBOR rate plus 1.45% . The Trust I Debentures mature on September 15, 2035, but may be redeemed at par at the Bancorp’s option, subject to the approval of the applicable banking regulator to the extent required under applicable guidelines or policies. On August 29, 2005, Trust II issued $14.4 million of capital securities (“Trust II Capital Securities”) in a private placement of trust preferred securities. The Trust II Capital Securities mature in November 2035, are redeemable at the Bancorp’s option and require quarterly distributions by Trust II to the holder of the Trust II Capital Securities, at a rate equal to the three-month LIBOR rate plus 1.45% . The Bancorp has guaranteed the Trust II Capital Securities and, to the extent not paid by Trust II, accrued and unpaid distributions on the Trust II Capital Securities, as well as the redemption price payable to the Trust II Capital Securities holders. The proceeds of the Trust II Capital Securities, along with proceeds from the issuance of common securities by Trust II to the Bancorp, were used to purchase $14.4 million of the Bancorp’s junior subordinated deferrable interest notes (the “Trust II Debentures”) and constitute the primary asset of Trust II. Like the Trust II Capital Securities, the Trust II Debentures bear interest at a rate equal to the three-month LIBOR rate plus 1.45% . The Trust II Debentures mature on November 23, 2035, but may be redeemed at par at the Bancorp’s option, subject to the approval of the applicable banking regulator to the extent required under applicable guidelines or policies.

Shareholders' Equity

Shareholders' Equity	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Shareholders' Equity	Shareholders’ Equity 2006 Stock Repurchase Plan In December 2006, the Bancorp’s Board of Directors approved the 2006 Stock Repurchase Plan authorizing the repurchase of up to 400,000 shares, or approximately 3% , of the Corporation’s common stock in open market transactions. This authority may be exercised from time to time and in such amounts as market conditions warrant, and subject to regulatory considerations. The repurchased shares would be held as treasury stock to be used for general corporate purposes. As of December 31, 2017 , a cumulative total of 185,400 shares have been repurchased, all of which were repurchased in 2007 at a total cost of $4.8 million . Dividends The primary source of liquidity for the Bancorp is dividends received from the Bank. The Bancorp and the Bank are regulated enterprises and their abilities to pay dividends are subject to regulatory review and restriction. Certain regulatory and statutory restrictions exist regarding dividends, loans, and advances from the Bank to the Bancorp. Generally, the Bank has the ability to pay dividends to the Bancorp subject to minimum regulatory capital requirements. The FDIC and the FRB have the authority to use their enforcement powers to prohibit a bank or bank holding company, respectively, from paying dividends if, in their opinion, the payment of dividends would constitute an unsafe or unsound practice. Under the most restrictive of these requirements, the Bank could have declared aggregate additional dividends of $209.8 million as of December 31, 2017 . Reserved Shares As of December 31, 2017 , a total of 1,989,991 common stock shares were reserved for issuance under the 2003 Stock Incentive Plan, the 2013 Stock Option and Incentive Plan and the Amended and Restated Dividend Reinvestment and Stock Purchase Plan. Regulatory Capital Requirements The Bancorp and the Bank are subject to various regulatory capital requirements administered by the FRB and the FDIC, respectively. Regulatory authorities can initiate certain mandatory actions if Bancorp or the Bank fail to meet minimum capital requirements, which could have a direct material effect on the Corporation’s financial statements. Capital adequacy guidelines and, additionally for banks, prompt corrective action regulations involve quantitative measures of assets, liabilities, and certain off-balance sheet items calculated under regulatory accounting practices. These quantitative measures, to ensure capital adequacy, require minimum amounts and ratios. Capital levels at December 31, 2017 exceeded the regulatory minimum levels to be considered “well capitalized.” The following table presents the Corporation’s and the Bank’s actual capital amounts and ratios, as well as the corresponding minimum and well capitalized regulatory amounts and ratios that were in effect during the respective periods: (Dollars in thousands) Actual For Capital Adequacy Purposes To Be “Well Capitalized” Under Prompt Corrective Action Regulations Amount Ratio Amount Ratio Amount Ratio December 31, 2017 Total Capital (to Risk-Weighted Assets): Corporation $416,038 12.45 % $267,365 8.00 % N/A N/A Bank 413,593 12.38 267,338 8.00 334,172 10.00 Tier 1 Capital (to Risk-Weighted Assets): Corporation 389,289 11.65 200,524 6.00 N/A N/A Bank 386,844 11.58 200,503 6.00 267,338 8.00 Common Equity Tier 1 Capital (to Risk-Weighted Assets): Corporation 367,291 10.99 150,383 4.50 N/A N/A Bank 386,844 11.58 150,378 4.50 217,212 6.50 Tier 1 Capital (to Average Assets): (1) Corporation 389,289 8.79 177,089 4.00 N/A N/A Bank 386,844 8.74 177,048 4.00 221,310 5.00 December 31, 2016 Total Capital (to Risk-Weighted Assets): Corporation 390,867 12.26 255,093 8.00 N/A N/A Bank 389,840 12.23 255,050 8.00 318,813 10.00 Tier 1 Capital (to Risk-Weighted Assets): Corporation 364,655 11.44 191,320 6.00 N/A N/A Bank 363,628 11.41 191,288 6.00 255,050 8.00 Common Equity Tier 1 Capital (to Risk-Weighted Assets): Corporation 342,656 10.75 143,490 4.50 N/A N/A Bank 363,628 11.41 143,466 4.50 207,228 6.50 Tier 1 Capital (to Average Assets): (1) Corporation 364,655 8.67 168,271 4.00 N/A N/A Bank 363,628 8.65 168,207 4.00 210,259 5.00 (1) Leverage ratio. In addition to the minimum regulatory capital required for capital adequacy purposes included in the table above, the Corporation is required to maintain a minimum Capital Conservation Buffer, in the form of common equity, in order to avoid restrictions on capital distributions and discretionary bonuses. The required amount of the Capital Conservation Buffer was 0.625% on January 1, 2016 and 1.25% on January 1, 2017. The Capital Conservation Buffer will increase by 0.625% each year until it reaches 2.5% on January 1, 2019.

Derivative Financial Instrument

Derivative Financial Instruments	12 Months Ended
	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Financial Instruments	Derivative Financial Instruments The Corporation’s derivative financial instruments are used to manage differences in the amount, timing, and duration of the Corporation’s known or expected cash receipts and its known or expected cash payments principally to manage the Corporation’s interest rate risk. Additionally, the Corporation enters into interest rate derivatives to accommodate the business requirements of its customers. All derivatives are recognized as either assets or liabilities on the balance sheet and are measured at fair value. The accounting for changes in the fair value of derivatives depends on the intended use of the derivative and resulting designation. Interest Rate Risk Management Agreements Interest rate risk management agreements, such as swaps, caps and floors, are used from time to time as part of the Corporation’s interest rate risk management strategy. Interest rate swaps are agreements in which the Corporation and another party agree to exchange interest payments (e.g., fixed-rate for variable-rate payments) computed on a notional principal amount. Interest rate caps and floors represent options purchased by the Corporation to manage the interest rate paid throughout the term of the option contract. The credit risk associated with these transactions is the risk of default by the counterparty. To minimize this risk, the Corporation enters into interest rate agreements only with highly rated counterparties that management believes to be creditworthy. The notional amounts of these agreements do not represent amounts exchanged by the parties and, thus, are not a measure of the potential loss exposure. Cash Flow Hedging Instruments As of December 31, 2017 and 2016 , the Bank had two interest rate swap contracts with a total notional amount of $60.0 million that were designated as cash flow hedges to hedge the interest rate risk associated with short-term variable rate FHLB advances. The interest rate swaps mature in 2021 and 2023. As of December 31, 2017 and 2016 , the Bancorp had two interest rate caps with a total notional amount of $22.7 million that were designated as cash flow hedges to hedge the interest rate risk associated with our variable rate junior subordinated debentures. For both interest rate caps, the Bancorp obtained the right to receive the difference between 3-month LIBOR and a 4.5% strike. The caps mature in 2020. During 2017 , the Bank executed three interest rate floor contracts with a total notional amount of $300.0 million that were designated as cash flow hedges to hedge the interest rate risk associated with a pool of variable rate commercial loans. The Bank obtained the right to receive the difference between 1-month LIBOR and a 1.0% strike for each of the interest rate floors. The floors mature in 2020. The effective portion of the changes in fair value of derivatives designated as cash flow hedges is recorded in other comprehensive income and subsequently reclassified to earnings when gains or losses are realized. The ineffective portion of changes in fair value of the derivatives is recognized directly in earnings. For the year ended December 31, 2017 and 2016 , there was no ineffectiveness recorded in earnings. Loan Related Derivative Contracts Interest Rate Swap Contracts with Customers The Corporation has entered into interest rate swap contracts to help commercial loan borrowers manage their interest rate risk. The interest rate swap contracts with commercial loan borrowers allow them to convert variable-rate loan payments to fixed-rate loan payments. When we enter into an interest rate swap contract with a commercial loan borrower, we simultaneously enter into a “mirror” swap contract with a third party. The third party exchanges the client’s fixed-rate loan payments for variable-rate loan payments. We retain the risk that is associated with the potential failure of counterparties and the risk inherent in originating loans. As of December 31, 2017 and 2016 , Washington Trust had interest rate swap contracts with commercial loan borrowers with notional amounts of $545.0 million and $428.7 million , respectively, and equal amounts of “mirror” swap contracts with third-party financial institutions. These derivatives are not designated as hedges and therefore, changes in fair value are recognized in earnings. Risk Participation Agreements The Corporation has entered into risk participation agreements with other banks participating in commercial loan arrangements. Participating banks guarantee the performance on borrower-related interest rate swap contracts. These derivatives are not designated as hedges and therefore, changes in fair value are recognized in earnings. Under a risk participation-out agreement, a derivative asset, the Corporation participates out a portion of the credit risk associated with the interest rate swap position executed with the commercial borrower for a fee paid to the participating bank. Under a risk participation-in agreement, a derivative liability, the Corporation assumes, or participates in, a portion of the credit risk associated with the interest rate swap position with the commercial borrower for a fee received from the other bank. As of December 31, 2017 , the notional amounts of the risk participation-out agreements and risk participation-in agreements were $52.4 million and $34.1 million , respectively, compared to $38.3 million and $28.5 million , respectively, as of December 31, 2016 . Foreign Exchange Contracts Foreign exchange contracts represent a contractual commitment to buy or sell a foreign currency on a future date at a specified price. The Corporation uses these foreign exchange contracts on a limited basis to reduce its exposure to fluctuations in currency exchange rates associated with a commercial loan that is denominated in a foreign currency. These derivatives are not designated as hedges and therefore changes in fair value are recognized in earnings. The changes in fair value on the foreign exchange contracts substantially offset the foreign currency translation gains and losses on the related commercial loan. As of December 31, 2017 , the notional amount of foreign exchange contracts was $3.0 million . Loan Commitments Interest rate lock commitments are extended to borrowers and relate to the origination of residential real estate mortgage loans held for sale. To mitigate the interest rate risk inherent in these rate locks, as well as closed residential real estate mortgage loans held for sale, forward commitments are established to sell individual residential real estate mortgage loans. Both interest rate lock commitments and commitments to sell residential real estate mortgage loans are derivative financial instruments, but do not meet criteria for hedge accounting and, as such the changes in fair value of these commitments are reflected in earnings. The Corporation has elected to carry closed residential real estate mortgage loans held for sale at fair value, as changes in fair value in these loans held for sale generally offset changes in interest rate lock and forward sale commitments. The following table presents the fair values of derivative instruments in the Corporation’s Consolidated Balance Sheets: (Dollars in thousands) Asset Derivatives Liability Derivatives Fair Value Fair Value December 31, Balance Sheet Location 2017 2016 Balance Sheet Location 2017 2016 Derivatives Designated as Cash Flow Hedging Instruments: Interest rate risk management contracts: Interest rate swaps Other assets $213 $— Other liabilities $14 $378 Interest rate caps Other assets 25 134 Other liabilities — — Interest rate floors Other assets 110 — Other liabilities — — Derivatives not Designated as Hedging Instruments: Forward loan commitments: Interest rate lock commitments Other assets 965 1,133 Other liabilities 20 88 Commitments to sell mortgage loans Other assets 26 279 Other liabilities 1,424 1,349 Loan related derivative contracts: Interest rate swaps with customers Other assets 268 2,036 Other liabilities 1,295 — Mirror swaps with counterparties Other assets 1,152 — Other liabilities 268 2,228 Risk participation agreements Other assets — — Other liabilities — — Foreign exchange contracts Other assets — — Other liabilities 26 — Total $2,759 $3,582 $3,047 $4,043 The following tables present the effect of derivative instruments in the Corporation’s Consolidated Statements of Changes in Shareholders’ Equity and Consolidated Statements of Income: (Dollars in thousands) Gain (Loss) Recognized in Other Comprehensive Income, Net of Tax (Effective Portion) Years ended December 31, 2017 2016 2015 Derivatives Designated as Cash Flow Hedging Instruments: Interest rate risk management contracts: Interest rate swaps $358 ($224 ) $288 Interest rate caps (64 ) (33 ) (44 ) Interest rate floors (346 ) — — Total ($52 ) ($257 ) $244 (Dollars in thousands) Amount of Gain (Loss) Recognized in Income on Derivatives Years ended December 31, Statement of Income Location 2017 2016 2015 Derivatives not Designated as Hedging Instruments: Forward loan commitments: Interest rate lock commitments Mortgage banking revenues ($100 ) ($175 ) $28 Commitments to sell mortgage loans Mortgage banking revenues (328 ) 942 3 Loan related derivative contracts: Interest rate swaps with customers Loan related derivative income 2,243 (598 ) 7,569 Mirror swaps with counterparties Loan related derivative income 1,198 3,854 (4,904 ) Risk participation agreements Loan related derivative income (233 ) (13 ) (224 ) Foreign exchange contracts Loan related derivative income 6 — — Total $2,786 $4,010 $2,472

Balance Sheet Offsetting

Balance Sheet Offsetting	12 Months Ended
	Dec. 31, 2017
Balance Sheet Offsetting [Abstract]
Balance Sheet Offsetting	Balance Sheet Offsetting For interest rate risk management contracts and loan related derivative contracts, the Corporation records derivative assets and derivative liabilities on a net basis. The interest rate risk management contracts and loan related derivative contracts with counterparties are subject to master netting agreements. The following tables present the Corporation’s derivative asset and derivative liability positions and the effect of netting arrangements on the Consolidated Balance Sheets: (Dollars in thousands) Gross Derivative Positions Offsetting Derivative Positions Net Amounts Presented in Balance Sheet Cash Collateral Pledged Net Amount December 31, 2017 Derivative Assets: Interest rate risk management contracts: Interest rate caps $25 $— $25 $— $25 Interest rate floors 110 — 110 — 110 Interest rate swaps 213 — 213 — 213 Loan related derivative contracts: Interest rate swaps with customers 2,857 2,589 268 — 268 Mirror swaps with counterparties 3,801 2,649 1,152 — 1,152 Total $7,006 $5,238 $1,768 $— $1,768 Derivative Liabilities: Interest rate risk management contracts: Interest rate swaps $14 $— $14 $14 $— Loan related derivative contracts: Interest rate swaps with customers 3,884 2,589 1,295 1,025 270 Mirror swaps with counterparties 2,917 2,649 268 — 268 Foreign exchange contracts 26 — 26 — 26 Total $6,841 $5,238 $1,603 $1,039 $564 (Dollars in thousands) Gross Derivative Positions Offsetting Derivative Positions Net Amounts Presented in Balance Sheet Cash Collateral Pledged Net Amount December 31, 2016 Derivative Assets: Interest rate risk management contracts: Interest rate caps $134 $— $134 $— $134 Loan related derivative contracts: Interest rate swaps with customers 4,920 2,884 2,036 — 2,036 Mirror swaps with counterparties 2,758 2,758 — — — Total $7,812 $5,642 $2,170 $— $2,170 Derivative Liabilities: Loan related derivative contracts: Interest rate swaps with customers $2,884 $2,884 $— $— $— Mirror swaps with counterparties 4,986 2,758 2,228 1,295 933 Total $8,248 $5,642 $2,606 $1,428 $1,178 As of December 31, 2017 and 2016 , Washington Trust pledged collateral to derivative counterparties in the form of cash totaling $1.0 million and $1.4 million , respectively. Washington Trust may need to post additional collateral in the future in proportion to potential increases in unrealized loss positions.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The Corporation uses fair value measurements to record fair value adjustments to certain assets and liabilities and to determine fair value disclosures. As of December 31, 2017 and 2016 , securities available for sale, residential real estate mortgage loans held for sale, derivatives and the contingent consideration liability are recorded at fair value on a recurring basis. Additionally, from time to time, we may be required to record at fair value other assets on a nonrecurring basis, such as collateral dependent impaired loans, property acquired through foreclosure or repossession and mortgage servicing rights. These nonrecurring fair value adjustments typically involve the application of lower of cost or market accounting or write-downs of individual assets. Fair value is a market-based measurement, not an entity-specific measurement. Fair value measurements are determined based on the assumptions the market participants would use in pricing the asset or liability. In addition, GAAP specifies a hierarchy of valuation techniques based on whether the types of valuation information (“inputs”) are observable or unobservable. Observable inputs reflect market data obtained from independent sources, while unobservable inputs reflect the Corporation’s market assumptions. These two types of inputs have created the following fair value hierarchy: • Level 1 – Quoted prices for identical assets or liabilities in active markets. • Level 2 – Quoted prices for similar assets or liabilities in active markets; quoted prices for identical or similar assets or liabilities in inactive markets; and model-derived valuations in which all significant inputs and significant value drivers are observable in active markets. • Level 3 – Valuations derived from valuation techniques in which one or more significant inputs or significant value drivers are unobservable in the markets and which reflect the Corporation’s market assumptions. Fair Value Option Election GAAP allows for the irrevocable option to elect fair value accounting for the initial and subsequent measurement for certain financial assets and liabilities on a contract-by-contract basis. The Corporation has elected the fair value option for residential real estate mortgage loans held for sale to better match changes in fair value of the loans with changes in the fair value of the derivative loan sale contracts used to economically hedge them. The aggregate principal amount of the residential real estate mortgage loans held for sale recorded at fair value was $26.4 million and $29.4 million , respectively, at December 31, 2017 and 2016 . The aggregate fair value of these loans as of the same dates was $26.9 million and $29.4 million , respectively. As of December 31, 2017 and 2016 , the aggregate fair value of residential real estate mortgage loans held for sale exceeded the aggregate principal amount by $543 thousand and $40 thousand , respectively. There were no residential real estate mortgage loans held for sale 90 days or more past due as of December 31, 2017 and 2016 . The following table presents the changes in fair value related to mortgage loans held for sale, interest rate lock commitments and commitments to sell residential real estate mortgage loans, for which the fair value option was elected. Changes in fair values are reported as a component of mortgage banking revenues in the Consolidated Statements of Income. (Dollars in thousands) Years ended December 31, 2017 2016 2015 Mortgage loans held for sale $503 ($691 ) ($48 ) Interest rate lock commitments (100 ) (175 ) 28 Commitments to sell (328 ) 942 3 Total changes in fair value $75 $76 ($17 ) Valuation Techniques Securities Securities available for sale are recorded at fair value on a recurring basis. When available, the Corporation uses quoted market prices to determine the fair value of securities; such items are classified as Level 1. There were no Level 1 securities held at December 31, 2017 and 2016 . Level 2 securities include debt securities with quoted prices, which are traded less frequently than exchange-traded instruments. The fair value of these securities is determined using matrix pricing with inputs that are observable in the market or can be derived principally from or corroborated by observable market data. This category includes obligations of U.S. government-sponsored enterprises, including mortgage-backed securities, obligations of states and political subdivisions, individual name issuer trust preferred debt securities and corporate bonds. Securities not actively traded whose fair value is determined through the use of cash flows utilizing inputs that are unobservable are classified as Level 3. There were no Level 3 securities held at December 31, 2017 and 2016 . Mortgage Loans Held for Sale The fair value of mortgage loans held for sale is estimated based on current market prices for similar loans in the secondary market and therefore are classified as Level 2 assets. Collateral Dependent Impaired Loans The fair value of collateral dependent loans that are deemed to be impaired is determined based upon the fair value of the underlying collateral. Such collateral primarily consists of real estate and, to a lesser extent, other business assets. For collateral dependent loans for which repayment is dependent on the sale of the collateral, management adjusts the fair value for estimated costs to sell. For collateral dependent loans for which repayment is dependent on the operation of the collateral, such as accruing troubled debt restructured loans, estimated costs to sell are not incorporated into the measurement. Management may also adjust appraised values to reflect estimated market value declines or apply other discounts to appraised values resulting from its knowledge of the property. Internal valuations are utilized to determine the fair value of other business assets. Collateral dependent impaired loans are categorized as Level 3. Property Acquired Through Foreclosure or Repossession Property acquired through foreclosure or repossession included in other assets in the Consolidated Balance Sheets is adjusted to fair value less costs to sell upon transfer out of loans through a charge to allowance for loan losses. Subsequently, it is carried at the lower of carrying value or fair value less costs to sell. Such subsequent valuation charges are charged through earnings. Fair value is generally based upon appraised values of the collateral. Management may adjust appraised values to reflect estimated market value declines or apply other discounts to appraised values for unobservable factors resulting from its knowledge of the property, and such property is categorized as Level 3. Derivatives Interest rate swap, cap and floor contracts are traded in over-the-counter markets where quoted market prices are not readily available. Fair value measurements are determined using independent pricing models that utilize primarily market observable inputs, such as swap rates of different maturities and LIBOR rates. The Corporation also evaluates the credit risk of its counterparties as well as that of the Corporation. Accordingly, Washington Trust considers factors such as the likelihood of default by the Corporation and its counterparties, its net exposures and remaining contractual life, among other factors, in determining if any fair value adjustments related to credit risk are required. Counterparty exposure is evaluated by netting positions that are subject to master netting agreements, as well as considering the amount of collateral securing the position. Although the Corporation has determined that the majority of the inputs used to value its interest rate swap, cap and floor contracts fall within Level 2 of the fair value hierarchy, the credit valuation adjustments associated with interest rate contracts and risk participation agreements utilize Level 3 inputs, such as estimates of current credit spreads to evaluate the likelihood of default by the Corporation and its counterparties. However, as of December 31, 2017 and 2016 , the Corporation has assessed the significance of the impact of the credit valuation adjustments on the overall valuation of its derivative positions and has determined that the credit valuation adjustments are not significant to the overall valuation of its derivatives. As a result, the Corporation has classified its derivative valuations in their entirety as Level 2. Fair value measurements of forward loan commitments (interest rate lock commitments and commitments to sell residential real estate mortgages) are estimated based on current market prices for similar assets in the secondary market and therefore are classified as Level 2 assets. Contingent Consideration Liability A contingent consideration liability was recognized upon the completion of the Halsey acquisition on August 1, 2015 representing the estimated present value of future earn-outs to be paid based on the future revenue growth of the acquired business during the five -year period following the acquisition. The fair value measurement is based upon unobservable inputs, therefore, the contingent liability is classified within Level 3 of the fair value hierarchy. The unobservable inputs include probability estimates regarding the likelihood of achieving revenue growth targets and the discount rates utilized the discounted cash flow calculations applied to the estimates earn-outs to be paid. The contingent consideration liability is remeasured to fair value at each reporting period taking into consideration changes in those unobservable inputs. Changes in the fair value of the contingent consideration liability are included in noninterest expenses in the Consolidated Statements of Income. One of the two earn-out periods associated with this contingent consideration liability ended December 31, 2017. As such, the applicable portion of the liability was adjusted to the payout amount based on the actual revenue growth results achieved during the first earn-out period. The discount rate used for the remaining portion of the contingent consideration liability was 4% . The fair value of the contingency represents the estimated price to transfer the liability between market participants at the measurement date under current market conditions. Items Recorded at Fair Value on a Recurring Basis The following tables present the balances of assets and liabilities reported at fair value on a recurring basis: (Dollars in thousands) Total Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs Significant Unobservable Inputs (Level 3) December 31, 2017 Assets: Securities available for sale: Obligations of U.S. government-sponsored enterprises $157,604 $— $157,604 $— Mortgage-backed securities issued by U.S. government agencies and U.S. government-sponsored enterprises 590,882 — 590,882 — Obligations of states and political subdivisions 2,359 — 2,359 — Individual name issuer trust preferred debt securities 16,984 — 16,984 — Corporate bonds 13,125 — 13,125 — Mortgage loans held for sale 26,943 — 26,943 — Derivative assets 2,759 — 2,759 — Total assets at fair value on a recurring basis $810,656 $— $810,656 $— Liabilities: Derivative liabilities $3,047 $— $3,047 $— Contingent consideration liability 1,404 — — 1,404 Total liabilities at fair value on a recurring basis $4,451 $— $3,047 $1,404 (Dollars in thousands) Total Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs Significant Unobservable Inputs (Level 3) December 31, 2016 Assets: Securities available for sale: Obligations of U.S. government-sponsored enterprises $108,440 $— $108,440 $— Mortgage-backed securities issued by U.S. government agencies and U.S. government-sponsored enterprises 588,085 — 588,085 — Obligations of states and political subdivisions 14,485 — 14,485 — Individual name issuer trust preferred debt securities 26,736 — 26,736 — Corporate bonds 2,166 — 2,166 — Mortgage loans held for sale 29,434 — 29,434 — Derivative assets 3,582 — 3,582 — Total assets at fair value on a recurring basis $772,928 $— $772,928 $— Liabilities: Derivative liabilities $4,043 $— $4,043 $— Contingent consideration liability 2,047 — — 2,047 Total liabilities at fair value on a recurring basis $6,090 $— $4,043 $2,047 It is the Corporation’s policy to review and reflect transfers between Levels as of the financial statement reporting date. There were no transfers in and/or out of Level 1, 2 or 3 during the years ended December 31, 2017 and 2016 . The contingent consideration liability is a Level 3 liability remeasured at fair value on a recurring basis. The following table presents the change in the contingent consideration liability, which is included in other liabilities in the Consolidated Balance Sheets. (Dollars in thousands) Years ended December 31, 2017 2016 Beginning Balance $2,047 $2,945 Change in fair value (643 ) (898 ) Payments — — Ending Balance $1,404 $2,047 Items Recorded at Fair Value on a Nonrecurring Basis The following table presents the carrying value of assets held at December 31, 2017 , which were written down to fair value during the year ended December 31, 2017 : (Dollars in thousands) Total Quoted Prices in Active Markets for Identical Assets Significant Other Observable Inputs Significant Unobservable Inputs Assets: Collateral dependent impaired loans $1,425 $— $— $1,425 Property acquired through foreclosure or repossession 131 — — 131 Total assets at fair value on a nonrecurring basis $1,556 $— $— $1,556 The allowance for loan losses on the collateral dependent impaired loans included in the table above amounted to $690 thousand at December 31, 2017 . The following table summarizes the carrying value of assets held at December 31, 2016 , which were written down to fair value during the year ended December 31, 2016 : (Dollars in thousands) Total Quoted Prices in Active Markets for Identical Assets Significant Other Observable Inputs Significant Unobservable Inputs Assets: Collateral dependent impaired loans $3,828 $— $— $3,828 Property acquired through foreclosure or repossession 605 — — 605 Total assets at fair value on a nonrecurring basis $4,433 $— $— $4,433 The allowance for loan losses on the collateral dependent impaired loans included in the table above amounted to $469 thousand at December 31, 2016 . The following tables present valuation techniques and unobservable inputs for assets measured at fair value on a nonrecurring basis for which the Corporation has utilized Level 3 inputs to determine fair value: (Dollars in thousands) Fair Value Valuation Technique Unobservable Input Range of Inputs Utilized (Weighted Average) December 31, 2017 Collateral dependent impaired loans $1,425 Appraisals of collateral Discount for costs to sell 0% - 15% (15%) Property acquired through foreclosure or repossession 131 Appraisals of collateral Discount for costs to sell 10% Appraisal adjustments (1) 12% - 17% (15%) (1) Management adjusts appraisal values to reflect market value declines or other discounts resulting from its knowledge of the property. (Dollars in thousands) Fair Value Valuation Technique Unobservable Input Range of Inputs Utilized (Weighted Average) December 31, 2016 Collateral dependent impaired loans $3,828 Appraisals of collateral Discount for costs to sell 10% - 20% (15%) Appraisal adjustments (1) 0% - 10% (9%) Property acquired through foreclosure or repossession 605 Appraisals of collateral Discount for costs to sell 10% - 12% (11%) Appraisal adjustments (1) 6% - 50% (24%) (1) Management adjusts appraisal values to reflect market value declines or other discounts resulting from its knowledge of the property. Valuation of Other Financial Instruments The methodologies for estimating the fair value of financial instruments that are measured at fair value on a recurring or nonrecurring basis are discussed above. The methodologies for other financial instruments are discussed below. Loans Fair values are estimated for categories of loans with similar financial characteristics. Loans are segregated by type and are then further segmented into fixed-rate and adjustable-rate interest terms to determine their fair value. The fair value of fixed-rate commercial and consumer loans is calculated by discounting scheduled cash flows through the estimated maturity of the loan using interest rates offered at the measurement date that reflect the credit and interest rate risk inherent in the loan. The estimate of maturity is based on the Corporation’s historical repayment experience. For residential mortgages, fair value is estimated by using market prices for sales of similar loans on the secondary market. The fair value of variable-rate commercial and consumer loans approximates carrying value. Fair value for impaired loans is estimated using a discounted cash flow method based upon the loan’s contractual effective interest rate, or at the loan’s observable market price, or if the loan is collateral dependent, at the fair value of the collateral. Loans are classified within Level 3 of the fair value hierarchy. Time Deposits The discounted values of cash flows using the rates currently offered for deposits of similar remaining maturities were used to estimate the fair value of time deposits. Time deposits are classified within Level 2 of the fair value hierarchy. Federal Home Loan Bank Advances Rates currently available to the Corporation for advances with similar terms and remaining maturities are used to estimate fair value of existing advances. FHLB advances are categorized as Level 2. Junior Subordinated Debentures The fair value of the junior subordinated debentures is estimated using rates currently available to the Corporation for debentures with similar terms and maturities. Junior subordinated debentures are categorized as Level 2. The following tables present the carrying amount, estimated fair value and placement in the fair value hierarchy of the Corporation’s financial instruments. The tables exclude financial instruments for which the carrying value approximates fair value such as cash and cash equivalents, FHLB stock, accrued interest receivable, bank-owned life insurance, non-maturity deposits and accrued interest payable. (Dollars in thousands) Carrying Amount Total Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs Significant Unobservable Inputs (Level 3) December 31, 2017 Financial Assets: Securities held to maturity $12,541 $12,721 $— $12,721 $— Loans, net of allowance for loan losses 3,347,583 3,369,932 — — 3,369,932 Financial Liabilities: Time deposits $1,015,095 $1,018,396 $— $1,018,396 $— FHLB advances 791,356 792,887 — 792,887 — Junior subordinated debentures 22,681 18,559 — 18,559 — (Dollars in thousands) Carrying Amount Estimated Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs Significant Unobservable Inputs (Level 3) December 31, 2016 Financial Assets: Securities held to maturity $15,633 $15,920 $— $15,920 $— Loans, net of allowance for loan losses 3,208,367 3,218,651 — — 3,218,651 Financial Liabilities: Time deposits $961,613 $962,374 $— $962,374 $— FHLB advances 848,930 852,888 — 852,888 — Junior subordinated debentures 22,681 16,970 — 16,970 —

Employee Benefits

Employee Benefits	12 Months Ended
	Dec. 31, 2017
Retirement Benefits [Abstract]
Employee Benefits	Employee Benefits Defined Benefit Pension Plans The Corporation maintains a tax-qualified defined benefit pension plan for the benefit of certain eligible employees who were hired prior to October 1, 2007. The Corporation also has non-qualified retirement plans to provide supplemental retirement benefits to certain employees, as defined in the plans. The defined benefit pension plans were previously amended to freeze benefit accruals after a 10 -year transition period ending in December 2023. The defined benefit pension plan is funded on a current basis, in compliance with the requirements of ERISA. The non-qualified retirement plans provide for the designation of assets in rabbi trusts. Securities available for sale and other short-term investments designated for this purpose, with the carrying value of $13.3 million and $11.7 million are included in the Consolidated Balance Sheets at December 31, 2017 and 2016 , respectively. Pension benefit costs and benefit obligations incorporate various actuarial and other assumptions, including discount rates, mortality, rates of return on plan assets and compensation increases. Washington Trust evaluates these assumptions annually. The following table presents the plans’ projected benefit obligations, fair value of plan assets and funded (unfunded) status: (Dollars in thousands) Qualified Pension Plan Non-Qualified Retirement Plans At December 31, 2017 2016 2017 2016 Change in Benefit Obligation: Benefit obligation at beginning of period $72,951 $67,550 $13,154 $13,015 Service cost 2,149 2,148 129 122 Interest cost 2,673 2,576 428 432 Actuarial loss 7,017 3,888 2,275 374 Benefits paid (3,936 ) (3,072 ) (783 ) (789 ) Administrative expenses (131 ) (139 ) — — Benefit obligation at end of period 80,723 72,951 15,203 13,154 Change in Plan Assets: Fair value of plan assets at beginning of period 75,787 65,710 — — Actual return on plan assets 12,644 4,788 — — Employer contributions 3,000 8,500 783 789 Benefits paid (3,936 ) (3,072 ) (783 ) (789 ) Administrative expenses (131 ) (139 ) — — Fair value of plan assets at end of period 87,364 75,787 — — Funded (unfunded) status at end of period $6,641 $2,836 ($15,203 ) ($13,154 ) As of December 31, 2017 and 2016 , the funded status of the qualified defined benefit pension plan amounted to $6.6 million and $2.8 million , respectively, and was included in other assets in the Consolidated Balance Sheets. The unfunded status of the non-qualified defined benefit retirement plans was $15.2 million and $13.2 million , respectively, at December 31, 2017 and December 31, 2016 and was included in other liabilities in the Consolidated Balance Sheets. The following table presents components of accumulated other comprehensive income related to the qualified pension plan and non-qualified retirement plans, on a pre-tax basis: (Dollars in thousands) Qualified Pension Plan Non-Qualified Retirement Plans At December 31, 2017 2016 2017 2016 Net actuarial loss $13,795 $15,593 $6,448 $4,519 Prior service credit (39 ) (62 ) (1 ) (1 ) Total pre-tax amounts recognized in accumulated other comprehensive income $13,756 $15,531 $6,447 $4,518 The accumulated benefit obligation for the qualified pension plan was $72.9 million and $65.8 million at December 31, 2017 and 2016 , respectively. The accumulated benefit obligation for the non-qualified retirement plans amounted to $14.0 million and $12.0 million at December 31, 2017 and 2016 , respectively. The following table presents components of net periodic benefit cost and other amounts recognized in other comprehensive income (loss), on a pre-tax basis: (Dollars in thousands) Qualified Pension Plan Non-Qualified Retirement Plans Years ended December 31, 2017 2016 2015 2017 2016 2015 Net Periodic Benefit Cost: Service cost $2,149 $2,148 $2,459 $129 $122 $78 Interest cost 2,673 2,576 2,928 428 432 490 Expected return on plan assets (4,942 ) (4,633 ) (4,515 ) — — — Amortization of prior service credit (23 ) (23 ) (23 ) (1 ) (1 ) (1 ) Recognized net actuarial loss 1,114 828 1,249 347 247 245 Net periodic benefit cost 971 896 2,098 903 800 812 Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (on a pre-tax basis): Net (gain) loss (1,798 ) 2,904 (2,816 ) 1,928 127 (156 ) Prior service cost 23 23 23 1 1 1 Recognized in other comprehensive (loss) income (1,775 ) 2,927 (2,793 ) 1,929 128 (155 ) Total recognized in net periodic benefit cost and other comprehensive (loss) income ($804 ) $3,823 ($695 ) $2,832 $928 $657 For the qualified pension plan, an estimated prior service credit of $23 thousand and net losses of $1.5 million will be amortized from accumulated other comprehensive income (loss) into net periodic benefit cost during the year 2018 . For the non-qualified retirement plans, an estimated prior service credit of $1 thousand and net losses of $287 thousand will be amortized from accumulated other comprehensive income (loss) into net periodic benefit cost during the year 2018 . Assumptions The following table presents the measurement date and weighted-average assumptions used to determine benefit obligations at December 31, 2017 and 2016 : Qualified Pension Plan Non-Qualified Retirement Plans 2017 2016 2017 2016 Measurement date Dec 31, 2017 Dec 31, 2016 Dec 31, 2017 Dec 31, 2016 Discount rate 3.69% 4.18% 3.60% 4.00% Rate of compensation increase 3.75 3.75 3.75 3.75 The following table presents the measurement date and weighted-average assumptions used to determine net periodic benefit cost for the years ended December 31, 2017 , 2016 and 2015 : Qualified Pension Plan Non-Qualified Retirement Plans 2017 2016 2015 2017 2016 2015 Measurement date Dec 31, 2016 Dec 31, 2015 Dec 31, 2014 Dec 31, 2016 Dec 31, 2015 Dec 31, 2014 Discount rate N/A N/A 4.125% N/A N/A 3.90% Equivalent single discount rate for benefit obligations 4.18% 4.48 N/A 4.00% 4.20 N/A Equivalent single discount rate for service cost 4.29 4.63 N/A 4.25 4.59 N/A Equivalent single discount rate for interest cost 3.73 3.88 N/A 3.40 3.44 N/A Expected long-term return on plan assets 6.75 6.75 7.25 N/A N/A N/A Rate of compensation increase 3.75 3.75 3.75 3.75 3.75 3.75 The expected long-term rate of return on plan assets is based on what the Corporation believes is realistically achievable based on the types of assets held by the plan and the plan’s investment practices. The assumption is updated annually, taking into account the asset allocation, historical asset return trends on the types of assets held and the current and expected economic conditions. Future decreases in the long-term rate of return assumption on plan assets would increase pension costs and, in general, may increase the requirement to make funding contributions to the plans. Future increases in the long-term rate of return on plan assets would have the opposite effect. The discount rate assumption for defined benefit pension plans is reset on the measurement date. Discount rates are selected for each plan by matching expected future benefit payments stream to a yield curve based on a selection of high- quality fixed-income debt securities. Future decreases in discount rates would increase the present value of pension obligations and increase our pension costs, while future increases in discount rates would have the opposite effect. Prior to 2016, a single weighted-average discount rate was used to calculate interest and service cost components of net periodic benefit cost. For 2016 and periods thereafter, Washington Trust utilized a "spot rate approach" in the calculation of interest and service cost. The spot rate approach applies separate discount rates for each projected benefit payment in the calculation of interest and service cost. This approach provides a more precise measurement of service and interest cost by improving the correlation between projected benefit cash flows and their corresponding spot rates. Plan Assets The following tables present the fair values of the qualified pension plan’s assets: (Dollars in thousands) Fair Value Measurements Using Assets at Fair Value December 31, 2017 Level 1 Level 2 Level 3 Assets: Cash and cash equivalents $3,760 $— $— $3,760 Obligations of U.S. government-sponsored enterprises — 5,926 — 5,926 Obligations of states and political subdivisions — 2,971 — 2,971 Corporate bonds — 13,112 — 13,112 Common stocks 38,508 — — 38,508 Mutual funds 23,087 — — 23,087 Total plan assets $65,355 $22,009 $— $87,364 (Dollars in thousands) Fair Value Measurements Using Assets at Fair Value December 31, 2016 Level 1 Level 2 Level 3 Assets: Cash and cash equivalents $2,880 $— $— $2,880 Obligations of U.S. government-sponsored enterprises — 4,233 — 4,233 Obligations of states and political subdivisions — 3,418 — 3,418 Corporate bonds — 13,775 — 13,775 Common stocks 33,893 — — 33,893 Mutual funds 17,588 — — 17,588 Total plan assets $54,361 $21,426 $— $75,787 The qualified pension plan uses fair value measurements to record fair value adjustments to the securities held in its investment portfolio. When available, the qualified pension plan uses quoted market prices to determine the fair value of securities; such items are classified as Level 1. This category includes cash equivalents, common stocks and mutual funds which are exchange-traded. Level 2 securities in the qualified pension plan include debt securities with quoted prices, which are traded less frequently than exchange-traded instruments, whose values are determined using matrix pricing with inputs that are observable in the market or can be derived principally from or corroborated by observable market data. This category includes obligations of U.S. government-sponsored enterprises, obligations of states and political subdivisions and corporate bonds. In certain cases where there is limited activity or less transparency around inputs to the valuation, securities may be classified as Level 3. As of December 31, 2017 and 2016 , the qualified pension plan did not have any securities in the Level 3 category. The following table present the asset allocations of the qualified pension plan, by asset category: December 31, 2017 2016 Asset Category: Equity securities 65.7 % 63.8 % Fixed income securities 30.0 32.4 Cash and cash equivalents 4.3 3.8 Total 100.0 % 100.0 % The assets of the qualified defined benefit pension plan trust (the “Pension Trust”) are managed to balance the needs of cash flow requirements and long-term rate of return. Cash inflow is typically comprised of investment income from portfolio holdings and Bank contributions, while cash outflow is for the purpose of paying plan benefits and certain plan expenses. As early as possible each year, the trustee is advised of the projected schedule of employer contributions and estimations of benefit payments. As a general rule, the trustee shall invest the funds to produce sufficient income to cover benefit payments and maintain a funded status that exceeds the regulatory requirements for tax-qualified defined benefit plans. The investment philosophy used for the Pension Trust emphasizes consistency of results over an extended market cycle, while reducing the impact of the volatility of the security markets upon investment results. The assets of the Pension Trust should be protected by substantial diversification of investments, providing exposure to a wide range of quality investment opportunities in various asset classes, with a high degree of liquidity. The investment objective with respect to the Pension Trust assets is to provide capital appreciation with a current income component. At any time, the portfolio will typically be invested in the following ranges: 50% to 70% in equities; 30% to 50% in fixed income; and 0% to 10% in cash and cash equivalents. The trustee investment manager will have authorization to invest within these ranges, making decisions based upon market conditions. Fixed income bond investments should be limited to those in the top four categories used by the major credit rating agencies. High yield bond funds may be used to provide exposure to this asset class as a diversification tool provided they do not exceed 10% of the portfolio. In order to reduce the volatility of the annual rate of return of the bond portfolio, attention will be given to the maturity structure of the portfolio in the light of money market conditions and interest rate forecasts. The assets of the Pension Trust will typically have a laddered maturity structure, avoiding large concentrations in any single year. Equity holdings provide opportunities for dividend and capital appreciation returns. Holdings will be appropriately diversified by maintaining broad exposure to large-, mid- and small-cap stocks as well as international equities. Concentration in small-cap, mid-cap and international equities is limited to no more than 20% , 20% and 30% of the equity portfolio, respectively. Investment selection and mix of equity holdings should be influenced by forecasts of economic activity, corporate profits and allocation among different segments of the economy while ensuring efficient diversification. The fair value of equity securities of any one issuer will not be permitted to exceed 10% of the total fair value of equity holdings of the Pension Trust. Investments in publicly traded real estate investment trust securities and low-risk derivatives securities such as callable securities, variable-rate notes, mortgage-backed securities and treasury inflation protected securities, are permitted. Cash Flows Contributions The Internal Revenue Code permits flexibility in plan contributions so that normally a range of contributions is possible. The Corporation’s current funding policy has been generally to contribute the minimum required contribution and additional amounts up to the maximum deductible contribution. The Corporation expects to contribute $3.0 million to the qualified pension plan in 2018 . In addition, the Corporation expects to contribute $897 thousand in benefit payments to the non-qualified retirement plans in 2018 . Estimated Future Benefit Payments The following table presents the benefit payments, which reflect expected future service, as appropriate, expected to be paid: (Dollars in thousands) Qualified Pension Plan Non-Qualified Retirement Plans 2018 $3,964 $897 2019 2,931 891 2020 3,387 879 2021 3,784 868 2022 4,378 891 Years 2023 - 2027 28,050 4,221 401(k) Plan The Corporation’s 401(k) Plan provides a match up to a maximum of 3% of employee contributions for substantially all employees. In addition, substantially all employees hired after September 30, 2007, who are ineligible for participation in the qualified defined benefit pension plan, receive a non-elective employer contribution of 4% . Total employer matching contributions under this plan amounted to $2.3 million , $2.3 million and $1.8 million in 2017 , 2016 and 2015 , respectively. Other Incentive Plans The Corporation maintains several non-qualified incentive compensation plans. Substantially all employees participate in one of the incentive compensation plans. Incentive plans provide for annual or more frequent payments based on individual, business line and/or corporate performance targets (measured in terms of the Corporation’s net income, earnings per share and return on equity.) Total incentive based compensation in 2017 , 2016 and 2015 amounted to $16.9 million , $16.0 million and $14.3 million , respectively. In general, the terms of incentive plans are subject to annual renewal and may be terminated at any time by the Compensation Committee of the Board of Directors. Deferred Compensation Plan The Amended and Restated Nonqualified Deferred Compensation Plan provides supplemental retirement and tax benefits to directors and certain officers. The plan is funded primarily through pre-tax contributions made by the participants. The assets and liabilities of the Deferred Compensation Plan are recorded at fair value in the Corporation’s Consolidated Balance Sheets. The participants in the plan bear the risk of market fluctuations of the underlying assets. The accrued liability related to this plan amounted to $14.2 million and $10.8 million , respectively, at December 31, 2017 and 2016 , and is included in other liabilities on the accompanying Consolidated Balance Sheets. The corresponding invested assets are reported in other assets.

Share-Based Compensation Arrang

Share-Based Compensation Arrangements	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Compensation Arrangements	Share-Based Compensation Arrangements Washington Trust’s share-based compensation plans are described below. The 2013 Stock Option and Incentive Plan (the “2013 Plan”) was approved by shareholders on April 23, 2013. Under the 2013 Plan, the maximum number of shares of the Bancorp’s common stock to be issued is 1,748,250 . The 2013 Plan permits the granting of stock options and other equity incentives to officers, employees, directors and other key persons. The 2003 Stock Incentive Plan (the “2003 Plan”) was amended and restated and approved by shareholders in April 2009. Under the 2003 Plan, as amended and restated, the maximum number of shares of Bancorp’s common stock to be issued is 1,200,000 shares and the number of shares that can be issued in the form of awards other than stock options or stock appreciation rights is 400,000 . The 2003 Plan permits the granting of stock options and other equity incentives to officers, employees, directors and other key persons. The exercise price of each stock option may not be less than the fair market value of the Bancorp’s common stock on the date of grant, and options shall have a term of no more than ten years. Stock options are designated as either non-qualified or incentive stock options. In general, the stock option price is payable in cash, by the delivery of shares of common stock already owned by the grantee, or a combination thereof. With respect only to non-qualified stock option grants issued under the 2013 Plan, the exercise may also be accomplished by withholding the exercise price from the number of shares that would otherwise be delivered upon a cash exercise of the option. The fair value of stock options on the date of grant is estimated using the Black-Scholes Option-Pricing Model. Awards of nonvested share units and nonvested performance share units are valued at the fair market value of the Bancorp’s common stock as of the award date. Performance share awards are granted in order to provide certain officers of the Corporation the opportunity to earn shares of common stock, the number of which is determined pursuant to, and subject to the attainment of, performance goals during a specified measurement period. The number of shares earned will range from zero to 200% of the target number of shares dependent upon the Corporation’s core return on equity and core earnings per share growth ranking compared to an industry peer group. Vesting of stock options and share awards may accelerate or may be subject to proportional vesting if there is a change in control, disability, retirement or death (as defined in the 2013 Plan and the 2003 Plan). The following table presents share-based compensation expense and the related income tax benefit recognized in the Consolidated Statements of Income for stock options, nonvested share awards and nonvested performance shares: (Dollars in thousands) Years ended December 31, 2017 2016 2015 Share-based compensation expense $2,577 $2,190 $2,074 Related income tax benefit $606 $810 $767 Compensation expense for awards is recognized over the service period based on the fair value at the date of grant. Nonvested performance share unit compensation expense is based on the most recent performance assumption available and is adjusted as assumptions change. If the goals are not met, no compensation cost will be recognized and any recognized compensation costs will be reversed. Stock Options Washington Trust uses historical data to estimate stock option exercise and employee departure behavior used in the option-pricing model. The expected term of options granted was derived from the output of the option valuation model and represents the period of time that options granted are expected to be outstanding. Expected volatility was based on historical volatility of Washington Trust shares. The risk-free rate for periods within the contractual life of the stock option was based on the U.S. Treasury yield curve in effect at the date of grant. The following presents the assumptions used in determining the grant date fair value of the stock option awards granted to certain key employees: 2017 2016 2015 Options granted 47,725 53,400 48,600 Cliff vesting period (years) 3 3 3-5 Expected term (years) 7.0 7.5 7.5 Expected dividend yield 3.57 % 3.89 % 3.94 % Weighted average expected volatility 27.10 % 29.99 % 40.76 % Weighted average risk-free interest rate 1.70 % 1.66 % 1.95 % Weighted average grant-date fair value $10.60 $7.92 $11.15 The following table presents a summary of the status of Washington Trust’s stock options outstanding as of and for the year ended December 31, 2017 : Number of Stock Options Weighted Average Exercise Price Weighted Average Remaining Contractual Term (Years) Aggregate Intrinsic Value (000’s) Beginning of period 219,279 $32.70 Granted 47,725 58.05 Exercised (39,076 ) 28.30 Forfeited or expired (4,075 ) 43.06 End of period 223,853 $38.68 7.22 $3,487 At end of period: Options exercisable 80,003 $25.89 4.38 $2,189 Options expected to vest in future periods 143,850 $45.80 8.80 $1,298 The total intrinsic value is the amount by which the fair value of the underlying stock exceeds the exercise price of an option on the exercise date. The following table presents additional information concerning options outstanding and options exercisable at December 31, 2017 : Options Outstanding Options Exercisable Exercise Price Ranges Number of Shares Weighted Average Remaining Life (Years) Weighted Average Exercise Price Number of Shares Weighted Average Exercise Price $15.01 to $20.00 11,700 1.87 $17.52 11,700 $17.52 $20.01 to $25.00 38,593 3.88 23.14 38,593 23.14 $25.01 to $30.00 — — — — — $30.01 to $35.00 29,710 6.00 32.76 29,710 32.76 $35.01 to $40.00 46,000 7.76 39.39 — — $40.01 to $45.00 50,800 8.80 40.25 — — $45.01 to $50.00 — — — — — $50.01 to $55.00 — — — — — $55.01 to $60.00 47,050 9.80 58.05 — — 223,853 7.22 $38.68 80,003 $25.89 The total intrinsic value of stock options exercised during the years ended December 31, 2017 , 2016 and 2015 was $1.0 million , $3.2 million and $1.2 million , respectively. Nonvested Shares In 2017 , 2016 and 2015 , the Corporation granted to directors and certain key employees 15,900 , 22,175 and 16,275 nonvested share units, respectively, with 3 - to 5 -year cliff vesting. The following table presents a summary of the status of Washington Trust’s nonvested share units as of and for the year ended December 31, 2017 : Number of Shares Weighted Average Grant Date Fair Value Beginning of period 49,675 $37.12 Granted 15,900 54.46 Vested (11,325 ) 32.79 Forfeited (475 ) 40.25 End of period 53,775 $43.13 Nonvested Performance Shares The Corporation grants performance share units to certain executive officers providing the opportunity to earn shares of common stock over a 3 -year performance period based on profitability results of the Corporation in comparison to a peer group. The number of shares earned can range from zero to 200% of the target number of shares depending upon the Corporation’s core return on equity and core earnings per share growth ranking among an industry peer group. The following table presents a summary of the performance share awards as of December 31, 2017 : Grant Date Fair Value per Share Current Performance Assumption Expected Number of Shares Performance shares awarded in: 2017 $51.85 140% 36,470 2016 36.11 133% 45,220 2015 38.02 135% 35,775 Total 117,465 The following table presents a summary of the status of Washington Trust’s performance share units as of and for the year ended December 31, 2017 : Number of Shares Weighted Average Grant Date Fair Value Beginning of period 101,998 $36.58 Granted 36,470 51.85 Vested (16,707 ) 34.66 Forfeited (4,296 ) 36.93 End of period 117,465 $41.58 As of December 31, 2017 , there was $4.0 million of total unrecognized compensation cost related to share-based compensation arrangements, including stock options, nonvested share units and performance share units granted under the Plans. That cost is expected to be recognized over a weighted average period of 1.99 years.

Business Segments

Business Segments	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Business Segments	Business Segments Washington Trust segregates financial information in assessing its results among its Commercial Banking and Wealth Management Services operating segments. The amounts in the Corporate unit include activity not related to the segments. Commercial Banking The Commercial Banking segment includes commercial, residential and consumer lending activities; mortgage banking activities; deposit generation; cash management activities; and direct banking activities, which include the operation of ATMs, telephone and internet banking services and customer support and sales. Wealth Management Services Wealth Management Services includes investment management; financial planning; personal trust and estate services, including services as trustee, personal representative, custodian and guardian; and settlement of decedents’ estates. Institutional trust services are also provided, including fiduciary services. Corporate Corporate includes the Treasury Unit, which is responsible for managing the wholesale investment portfolio and wholesale funding needs. It also includes income from BOLI, as well as administrative and executive expenses not allocated to the operating segments and the residual impact of methodology allocations such as FTP offsets. The following tables present the statement of operations and total assets for Washington Trust’s reportable segments: (Dollars in thousands) Year ended December 31, 2017 Commercial Banking Wealth Management Services Corporate Consolidated Total Net interest income (expense) $98,736 ($167 ) $20,962 $119,531 Provision for loan losses 2,600 — — 2,600 Net interest income (expense) after provision for loan losses 96,136 (167 ) 20,962 116,931 Noninterest income 23,244 39,346 2,219 64,809 Noninterest expenses: Depreciation and amortization expense 2,604 1,689 196 4,489 Other noninterest expenses 60,828 26,718 12,065 99,611 Total noninterest expenses 63,432 28,407 12,261 104,100 Income before income taxes 55,948 10,772 10,920 77,640 Income tax expense 23,876 3,795 4,044 31,715 Net income $32,072 $6,977 $6,876 $45,925 Total assets at period end $3,491,845 $66,083 $971,922 $4,529,850 Expenditures for long-lived assets 2,224 360 195 2,779 (Dollars in thousands) Year ended December 31, 2016 Commercial Banking Wealth Management Services Corporate Consolidated Total Net interest income (expense) $91,221 ($66 ) $19,323 $110,478 Provision for loan losses 5,650 — — 5,650 Net interest income (expense) after provision for loan losses 85,571 (66 ) 19,323 104,828 Noninterest income 24,783 37,569 2,777 65,129 Noninterest expenses: Depreciation and amortization expense 2,771 1,940 224 4,935 Other noninterest expenses 58,452 25,239 12,477 96,168 Total noninterest expenses 61,223 27,179 12,701 101,103 Income before income taxes 49,131 10,324 9,399 68,854 Income tax expense 16,790 3,692 1,891 22,373 Net income $32,341 $6,632 $7,508 $46,481 Total assets at period end $3,354,633 $64,625 $961,857 $4,381,115 Expenditures for long-lived assets 2,267 464 381 3,112 (Dollars in thousands) Year ended December 31, 2015 Commercial Banking Wealth Management Services Corporate Consolidated Total Net interest income $84,757 ($47 ) $19,272 $103,982 Provision for loan losses 1,050 — — 1,050 Net interest income (expense) after provision for loan losses 83,707 (47 ) 19,272 102,932 Noninterest income 20,618 35,416 2,306 58,340 Noninterest expenses: Depreciation and amortization expense 2,584 1,488 213 4,285 Other noninterest expenses 55,203 25,632 11,809 92,644 Total noninterest expenses 57,787 27,120 12,022 96,929 Income before income taxes 46,538 8,249 9,556 64,343 Income tax expense 15,330 3,475 2,073 20,878 Net income $31,208 $4,774 $7,483 $43,465 Total assets at period end $3,152,231 $63,801 $555,572 $3,771,604 Expenditures for long-lived assets 4,714 411 354 5,479

Other Comprehensive Income (Los

Other Comprehensive Income (Loss)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Other Comprehensive Income (Loss)	Other Comprehensive Income (Loss) The following tables present the activity in other comprehensive income (loss): (Dollars in thousands) Year ended December 31, 2017 Pre-tax Amounts Income Taxes Net of Tax Securities available for sale: Changes in fair value of securities available for sale $986 $365 $621 Net (gains) losses on securities classified into noninterest income — — — Net change in fair value of securities available for sale $986 $365 $621 Cash flow hedges: Changes in fair value of cash flow hedges (774 ) (223 ) (551 ) Net cash flow hedge losses reclassified into earnings (1) 792 293 499 Net change in the fair value of cash flow hedges 18 70 (52 ) Defined benefit plan obligations: Defined benefit plan obligation adjustment (1,591 ) (594 ) (997 ) Amortization of net actuarial losses (2) 1,461 546 915 Amortization of net prior service credits (2) (24 ) (9 ) (15 ) Net change in defined benefit plan obligations (154 ) (57 ) (97 ) Total other comprehensive income $850 $378 $472 (1) The pre-tax amounts are included in interest expense on Federal Home Loan Bank advances, interest expense on junior subordinated debentures and interest income and fees on loans in the Consolidated Statements of Income. (2) The pre-tax amounts are included in salaries and employee benefits expense in the Consolidated Statements of Income. (Dollars in thousands) Year ended December 31, 2016 Pre-tax Amounts Income Taxes Net of Tax Securities available for sale: Changes in fair value of securities available for sale ($12,502 ) ($4,626 ) ($7,876 ) Net (gains) losses on securities classified into noninterest income — — — Net change in fair value of securities available for sale ($12,502 ) ($4,626 ) ($7,876 ) Cash flow hedges: Changes in fair value of cash flow hedges (403 ) (146 ) (257 ) Net cash flow hedge losses reclassified into earnings — — — Net change in the fair value of cash flow hedges (403 ) (146 ) (257 ) Defined benefit plan obligations: Defined benefit plan obligation adjustment (4,106 ) (1,518 ) (2,588 ) Amortization of net actuarial losses (1) 1,075 397 678 Amortization of net prior service credits (1) (24 ) (9 ) (15 ) Net change in defined benefit plan obligations (3,055 ) (1,130 ) (1,925 ) Total other comprehensive loss ($15,960 ) ($5,902 ) ($10,058 ) (1) The pre-tax amount is included in salaries and employee benefits expense in the Consolidated Statements of Income. (Dollars in thousands) Year ended December 31, 2015 Pre-tax Amounts Income Taxes Net of Tax Securities available for sale: Changes in fair value of securities available for sale ($4,926 ) ($1,755 ) ($3,171 ) Net (gains) losses on securities classified into noninterest income — — — Net change in fair value of securities available for sale (4,926 ) (1,755 ) (3,171 ) Cash flow hedges: Changes in fair value of cash flow hedges (102 ) (49 ) (53 ) Net cash flow hedge losses reclassified into earnings (1) 469 172 297 Net change in the fair value of cash flow hedges 367 123 244 Defined benefit plan obligations: Defined benefit plan obligation adjustment 1,478 376 1,102 Amortization of net actuarial losses (2) 1,494 542 952 Amortization of net prior service credits (2) (24 ) (7 ) (17 ) Net change in defined benefit plan obligations 2,948 911 2,037 Total other comprehensive loss ($1,611 ) ($721 ) ($890 ) (1) The pre-tax amount is included in interest expense on junior subordinated debentures in the Consolidated Statements of Income. (2) The pre-tax amount is included in salaries and employee benefits expense in the Consolidated Statements of Income. The following tables present the changes in accumulated other comprehensive income (loss) by component, net of tax: (Dollars in thousands) Net Unrealized (Losses) Gains on Available For Sale Securities Net Unrealized Losses on Cash Flow Hedges Pension Benefit Adjustment Total Balance at December 31, 2016 ($6,825 ) ($300 ) ($12,632 ) ($19,757 ) Other comprehensive income (loss) before reclassifications 621 (551 ) (741 ) (671 ) Amounts reclassified from accumulated other comprehensive income — 499 644 1,143 Net other comprehensive income (loss) 621 (52 ) (97 ) 472 Reclassification of income tax effects due to the adoption of ASU 2018-02 (1,330 ) (76 ) (2,819 ) (4,225 ) Balance at December 31, 2017 ($7,534 ) ($428 ) ($15,548 ) ($23,510 ) (Dollars in thousands) Net Unrealized Gains (Losses) on Available For Sale Securities Net Unrealized Losses on Cash Flow Hedges Pension Benefit Adjustment Total Balance at December 31, 2015 $1,051 ($43 ) ($10,707 ) ($9,699 ) Other comprehensive loss before reclassifications (7,876 ) (257 ) (2,588 ) (10,721 ) Amounts reclassified from accumulated other comprehensive income — — 663 663 Net other comprehensive loss (7,876 ) (257 ) (1,925 ) (10,058 ) Balance at December 31, 2016 ($6,825 ) ($300 ) ($12,632 ) ($19,757 ) (Dollars in thousands) Net Unrealized Gains (Losses) on Available For Sale Securities Net Unrealized Losses on Cash Flow Hedges Pension Benefit Adjustment Total Balance at December 31, 2014 $4,222 ($287 ) ($12,744 ) ($8,809 ) Other comprehensive (loss) income before reclassifications (3,171 ) (53 ) 1,102 (2,122 ) Amounts reclassified from accumulated other comprehensive income — 297 935 1,232 Net other comprehensive (loss) income (3,171 ) 244 2,037 (890 ) Balance at December 31, 2015 $1,051 ($43 ) ($10,707 ) ($9,699 )

Earnings Per Common Share

Earnings Per Common Share	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Earnings Per Common Share	Earnings per Common Share The following table presents the calculation of earnings per common share: (Dollars and shares in thousands, except per share amounts) Years ended December 31, 2017 2016 2015 Earnings per common share - basic: Net income $45,925 $46,481 $43,465 Less dividends and undistributed earnings allocated to participating securities (108 ) (97 ) (126 ) Net income applicable to common shareholders 45,817 46,384 43,339 Weighted average common shares 17,207 17,081 16,879 Earnings per common share - basic $2.66 $2.72 $2.57 Earnings per common share - diluted: Net income $45,925 $46,481 $43,465 Less dividends and undistributed earnings allocated to participating securities (108 ) (97 ) (126 ) Net income applicable to common shareholders 45,817 46,384 43,339 Weighted average common shares 17,207 17,081 16,879 Dilutive effect of common stock equivalents 131 127 188 Weighted average diluted common shares 17,338 17,208 17,067 Earnings per common share - diluted $2.64 $2.70 $2.54 Weighted average common stock equivalents, not included in common stock equivalents above because they were anti-dilutive, totaled 11,572 , 59,158 and 34,850 for the years ended December 31, 2017 , 2016 and 2015 , respectively.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Financial Instruments with Off-Balance Risk The Corporation is a party to financial instruments with off-balance sheet risk in the normal course of business to meet the financing needs of its customers and to manage the Corporation’s exposure to fluctuations in interest rates. These financial instruments include commitments to extend credit, standby letters of credit, forward loan commitments, loan related derivative contracts and interest rate risk management contracts. These instruments involve, to varying degrees, elements of credit risk in excess of the amount recognized in the Corporation’s Consolidated Balance Sheets. The contract or notional amounts of these instruments reflect the extent of involvement the Corporation has in particular classes of financial instruments. The Corporation’s credit policies with respect to interest rate swap agreements with commercial borrowers, commitments to extend credit and financial guarantees are similar to those used for loans. The interest rate swaps with other counterparties are generally subject to bilateral collateralization terms. The following table presents the contractual and notional amounts of financial instruments with off-balance sheet risk: (Dollars in thousands) December 31, 2017 2016 Financial instruments whose contract amounts represent credit risk: Commitments to extend credit: Commercial loans $537,310 $430,710 Home equity lines 254,855 232,375 Other loans 48,819 49,708 Standby letters of credit 6,666 6,250 Financial instruments whose notional amounts exceed the amount of credit risk: Forward loan commitments: Interest rate lock commitments 45,139 49,502 Commitments to sell mortgage loans 71,539 78,896 Loan related derivative contracts: Interest rate swaps with customers 545,049 428,723 Mirror swaps with counterparties 545,049 428,723 Risk participation-in agreements 34,052 28,460 Foreign exchange contracts 3,005 — Interest rate risk management contracts: Interest rate swaps 60,000 60,000 See Note 13 for additional disclosure pertaining to derivative financial instruments. Commitments to Extend Credit Commitments to extend credit are agreements to lend to a customer as long as there are no violations of any condition established in the contract. Commitments generally have fixed expiration dates or other termination clauses and may require payment of a fee. Since some of the commitments are expected to expire without being drawn upon, total commitment amounts do not necessarily represent future cash requirements. Each borrower’s creditworthiness is evaluated on a case-by-case basis. The amount of collateral obtained is based on management’s credit evaluation of the borrower. Standby Letters of Credit Standby letters of credit are conditional commitments issued to guarantee the performance of a customer to a third party. These standby letters of credit are primarily issued to support the financing needs of the Bank’s commercial customers. The credit risk involved in issuing standby letters of credit is essentially the same as that involved in extending loan facilities to customers. The collateral supporting those commitments is essentially the same as for other commitments. Most standby letters of credit extend for one year. At December 31, 2017 and 2016 , the maximum potential amount of undiscounted future payments, not reduced by amounts that may be recovered, totaled $6.7 million and $6.3 million , respectively. At December 31, 2017 and 2016 , there were no liabilities to beneficiaries resulting from standby letters of credit. Fee income on standby letters of credit was insignificant for the years ended December 31, 2017 , 2016 and 2015 . At December 31, 2017 and 2016 , a substantial portion of the standby letters of credit were supported by pledged collateral. The collateral obtained is determined based on management’s credit evaluation of the customer. Should the Corporation be required to make payments to the beneficiary, repayment from the customer to the Corporation is required. Forward Loan Commitments Interest rate lock commitments are extended to borrowers and relate to the origination of residential real estate mortgage loans held for sale. To mitigate the interest rate risk inherent in these rate locks, as well as closed residential real estate mortgage loans held for sale, forward commitments are established to sell individual residential real estate mortgage loans. Both interest rate lock commitments and commitments to sell residential real estate mortgage loans are derivative financial instruments. Leases At December 31, 2017 , the Corporation was committed to rent premises used in business operations under non-cancelable operating leases. Rental expense under the operating leases amounted to $4.3 million , $4.0 million and $3.5 million for December 31, 2017 , 2016 and 2015 , respectively. The following table presents the minimum annual lease payments under the terms of these leases, exclusive of renewal provisions: (Dollars in thousands) Years ending December 31: 2018 $3,518 2019 3,542 2020 2,863 2021 2,530 2022 2,158 2023 and thereafter 24,652 Total minimum lease payments $39,263 Lease expiration dates range from 7 months to 23 years, with additional renewal options on certain leases ranging from 9 months to 5 years. Other Contingencies Litigation The Corporation is involved in various claims and legal proceedings arising out of the ordinary course of business. Management is of the opinion, based on its review with counsel of the development of such matters to date, that the ultimate disposition of such matters will not materially affect the consolidated financial position or results of operations of the Corporation. Other When selling a residential real estate mortgage loan or acting as originating agent on behalf of a third party, Washington Trust generally makes various representations and warranties. The specific representations and warranties depend on the nature of the transaction and the requirements of the buyer. Contractual liability may arise when the representations and warranties are breached. In the event of a breach of these representations and warranties, Washington Trust may be required to either repurchase the residential real estate mortgage loan (generally at unpaid principal balance plus accrued interest) with the identified defects or indemnify (“make-whole”) the investor for its losses. In the case of a repurchase, the Corporation will bear any subsequent credit loss on the residential real estate mortgage loan. Washington Trust has experienced an insignificant number of repurchase demands over a period of many years. As of December 31, 2017 and 2016 , the carrying value of loans repurchased due to representation and warranty claims was $1.3 million and $524 thousand , respectively. Washington Trust has recorded a reserve for its exposure to losses for premium recapture and the obligation to repurchase previously sold residential real estate mortgage loans. The reserve balance amounted to $180 thousand at both December 31, 2017 and December 31, 2016 and is included in other liabilities in the Consolidated Balance Sheets. Any change in the estimate is recorded in mortgage banking revenues in the Consolidated Statements of Income.

Parent Company Financial Statem

Parent Company Financial Statements	12 Months Ended
	Dec. 31, 2017
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Parent Company Financial Statements	Parent Company Financial Statements The following tables present parent company only financial statements of the Bancorp, reflecting the investment in the Bank on the equity basis of accounting. The Statements of Changes in Shareholders’ Equity for the parent company only are identical to the Consolidated Statements of Changes in Shareholders’ Equity and are therefore not presented. Balance Sheets (Dollars in thousands, except par value) December 31, 2017 2016 Assets: Cash on deposit with bank subsidiary $1,664 $1,743 Investment in subsidiaries at equity value 434,831 413,613 Dividends receivable from subsidiaries 7,770 6,518 Other assets 259 332 Total assets $444,524 $422,206 Liabilities: Junior subordinated debentures $22,681 $22,681 Dividends payable 7,087 6,628 Contingent consideration liability 1,404 2,047 Other liabilities 68 46 Total liabilities 31,240 31,402 Shareholders’ Equity: Common stock of $.0625 par value; authorized 60,000,000 shares; issued and outstanding 17,226,508 shares in 2017 and 17,170,820 shares in 2016 1,077 1,073 Paid-in capital 117,961 115,123 Retained earnings 317,756 294,365 Accumulated other comprehensive loss (23,510 ) (19,757 ) Total shareholders’ equity 413,284 390,804 Total liabilities and shareholders’ equity $444,524 $422,206 Statements of Income (Dollars in thousands) Years ended December 31, 2017 2016 2015 Income: Dividends from subsidiaries $27,900 $24,542 $23,399 Other income 18 15 13 Total income 27,918 24,557 23,412 Expenses: Interest on junior subordinated debentures 613 491 871 Legal and professional fees 169 98 134 Acquisition related expenses — — 308 Change in fair value of contingent consideration (643 ) (898 ) 41 Other 298 282 254 Total expenses 437 (27 ) 1,608 Income before income taxes 27,481 24,584 21,804 Income tax benefit (expense) 340 (15 ) 557 Income before equity in undistributed earnings of subsidiaries 27,821 24,569 22,361 Equity in undistributed earnings of subsidiaries 18,104 21,912 21,104 Net income $45,925 $46,481 $43,465 Statements of Cash Flows (Dollars in thousands) Years ended December 31, 2017 2016 2015 Cash flow from operating activities: Net income $45,925 $46,481 $43,465 Adjustments to reconcile net income to net cash provided by operating activities: Equity in undistributed earnings of subsidiary (18,104 ) (21,912 ) (21,104 ) (Increase) decrease in dividend receivable (1,252 ) (1,436 ) 19 Decrease (increase) in other assets 72 45 (67 ) Increase (decrease) in accrued expenses and other liabilities 22 (12 ) 2,425 Change in fair value of contingent consideration liability (643 ) (898 ) 41 Tax benefit from stock option exercises and other equity instrument issuances 508 1,016 694 Other, net (673 ) (1,051 ) (3,363 ) Net cash provided by operating activities 25,855 22,233 22,110 Cash flows from investing activities: Cash used in business combination, net of cash acquired — — (1,671 ) Net cash used in investing activities — — (1,671 ) Cash flows from financing activities: Proceeds from stock option exercises and issuance of other equity instruments 366 978 1,563 Cash dividends paid (26,300 ) (24,637 ) (22,770 ) Net cash used in financing activities (25,934 ) (23,659 ) (21,207 ) Net decrease in cash (79 ) (1,426 ) (768 ) Cash at beginning of year 1,743 3,169 3,937 Cash at end of year $1,664 $1,743 $3,169

Selected Quarterly Consolidated

Selected Quarterly Consolidated Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Consolidated Financial Data (Unaudited)	Selected Quarterly Consolidated Financial Data (Unaudited) (Dollars and shares in thousands, except per share amounts) 2017 First Quarter Second Quarter Third Quarter Fourth Quarter Interest and dividend income $35,664 $37,153 $37,869 $38,900 Interest expense 6,985 7,249 7,810 8,011 Net interest income 28,679 29,904 30,059 30,889 Provision for loan losses 400 700 1,300 200 Net interest income after provision for loan losses 28,279 29,204 28,759 30,689 Noninterest income 14,510 16,806 17,283 16,210 Noninterest expense 25,286 26,306 26,754 25,754 Income before income taxes 17,503 19,704 19,288 21,145 Income tax expense 5,721 6,505 6,326 13,163 Net income $11,782 $13,199 $12,962 $7,982 Weighted average common shares outstanding - basic 17,186 17,206 17,212 17,223 Weighted average common shares outstanding - diluted 17,293 17,316 17,318 17,349 Per share information: Basic earnings per common share $0.68 $0.77 $0.75 $0.46 Diluted earnings per common share $0.68 $0.76 $0.75 $0.46 Cash dividends declared per share $0.38 $0.38 $0.39 $0.39 (Dollars and shares in thousands, except per share amounts) 2016 First Quarter Second Quarter Third Quarter Fourth Quarter Interest and dividend income $32,969 $32,190 $33,256 $35,055 Interest expense 5,234 5,414 5,877 6,467 Net interest income 27,735 26,776 27,379 28,588 Provision for loan losses 500 450 1,800 2,900 Net interest income after provision for loan losses 27,235 26,326 25,579 25,688 Noninterest income 14,634 15,914 17,261 17,320 Noninterest expense 25,450 26,030 24,650 24,973 Income before income taxes 16,419 16,210 18,190 18,035 Income tax expense 5,484 5,153 5,863 5,873 Net income $10,935 $11,057 $12,327 $12,162 Weighted average common shares outstanding - basic 17,023 17,067 17,090 17,142 Weighted average common shares outstanding - diluted 17,157 17,194 17,203 17,245 Per share information: Basic earnings per common share $0.64 $0.65 $0.72 $0.71 Diluted earnings per common share $0.64 $0.64 $0.72 $0.70 Cash dividends declared per share $0.36 $0.36 $0.37 $0.37

Summary of Significant Accoun31

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Consolidation	Washington Trust Bancorp, Inc. (the “Bancorp”) is a publicly-owned registered bank holding company that has elected to be a financial holding company. The Bancorp owns all of the outstanding common stock of The Washington Trust Company, of Westerly (the “Bank”), a Rhode Island chartered commercial bank founded in 1800. Through its subsidiaries, the Bancorp offers a complete product line of financial services including commercial, residential and consumer lending, retail and commercial deposit products, and wealth management services through its offices in Rhode Island, eastern Massachusetts and Connecticut. The consolidated financial statements include the accounts of the Bancorp and its subsidiaries (collectively, the “Corporation” or “Washington Trust”). All intercompany transactions have been eliminated.
Basis of Accounting	Certain previously reported amounts have been reclassified to conform to current year’s presentation. The accounting and reporting policies of the Corporation conform to GAAP and to general practices of the banking industry.
Use of Estimates	In preparing the financial statements, management is required to make estimates and assumptions that affect the reported amounts of assets and liabilities as of the date of the balance sheet and revenues and expenses for the period. Actual results could differ from those estimates. Material estimates that are particularly susceptible to change are the determination of the allowance for loan losses, the valuation of goodwill and identifiable intangible assets, the assessment of investment securities for impairment and the accounting for defined benefit pension plans.
Cash and Cash Equivalents	Short-term Investments Short-term investments consist of highly liquid investments with a maturity date of three months or less when purchased and are considered to be cash equivalents. The Corporation’s short-term investments may be comprised of overnight federal funds sold, securities purchased under resale agreements, money market mutual funds and U.S. Treasury bills. Cash Flows For purposes of reporting cash flows, cash and cash equivalents include cash on hand, amounts due from banks, and other short-term investments.
Securities	Securities Management determines the appropriate classification of securities at the time of purchase. Investments in debt securities that management has the positive intent and ability to hold to maturity are classified as held to maturity and carried at amortized cost. Investments not classified as held to maturity are classified as available for sale. Securities available for sale consist of debt securities that are available for sale to respond to changes in market interest rates, liquidity needs, changes in funding sources and other similar factors. These assets are specifically identified and are carried at fair value. Changes in fair value of available for sale securities, net of applicable income taxes, are reported as a separate component of shareholders’ equity. Washington Trust does not have a trading portfolio. Premiums and discounts are amortized and accreted over the term of the securities on a method that approximates the level yield method. The amortization and accretion is included in interest income on securities. Interest income is recognized when earned. Realized gains or losses from sales of securities are determined using the specific identification method. The fair values of securities may be based on either quoted market prices or third party pricing services. When the fair value of an investment security is less than its amortized cost basis, the Corporation assesses whether the decline in value is other-than-temporary. The Corporation considers whether evidence indicating the cost of the investment is recoverable outweighs evidence to the contrary. Evidence considered in this assessment includes the reasons for impairment, the severity and duration of the impairment, changes in the value subsequent to the reporting date, forecasted performance of the issuer, changes in the dividend or interest payment practices of the issuer, changes in the credit rating of the issuer or the specific security, and the general market condition in the geographic area or industry in which the issuer operates. In determining whether an other-than-temporary impairment has occurred for debt securities, the Corporation compares the present value of cash flows expected to be collected from the security with the amortized cost of the security. If the present value of expected cash flows is less than the amortized cost of the security, then the entire amortized cost of the security will not be recovered; that is, a credit loss exists, and an other-than-temporary impairment shall be considered to have occurred. The credit loss component of an other-than-temporary impairment write-down for debt securities is recorded in earnings while the remaining portion of the impairment loss is recognized, net of tax, in other comprehensive income provided that the Corporation does not intend to sell the underlying debt security and it is more-likely-than-not that the Corporation would not have to sell the debt security prior to recovery of the unrealized loss, which may be to maturity. If the Corporation intended to sell any securities with an unrealized loss or it is more-likely-than-not that the Corporation would be required to sell the investment securities before recovery of their amortized cost basis, then the entire unrealized loss would be recorded in earnings. See Note 4 for further discussion on the Corporation’s investment securities portfolio.
Federal Home Loan Bank Stock	Federal Home Loan Bank Stock The Bank is a member of the FHLB. The FHLB is a cooperative that provides services, including funding in the form of advances, to its member banking institutions. As a requirement of membership, the Bank must own a minimum amount of FHLB stock, calculated periodically based primarily on its level of borrowings from the FHLB. No market exists for shares of FHLB stock and therefore, they are carried at par value. FHLB stock may be redeemed at par value five years following termination of FHLB membership, subject to limitations which may be imposed by the FHLB or its regulator, the Federal Housing Finance Board, to maintain capital adequacy of the FHLB. While the Corporation currently has no intentions to terminate its FHLB membership, the ability to redeem its investment in FHLB stock would be subject to the conditions imposed by the FHLB. The Corporation monitors its investment to determine if impairment exists. Based on the capital adequacy and the liquidity position of the FHLB, management believes there is no impairment related to the carrying amount of the Corporation’s FHLB stock as of December 31, 2017 .
Mortgage Loans Held for Sale	Mortgage Loans Held for Sale Residential mortgage loans originated and intended for sale in the secondary market are classified as held for sale. The Corporation has elected the fair value option pursuant to Accounting Standards Codification (“ASC”) 825, “Financial Instruments” for closed loans intended for sale. ASC 825 allows for the irrevocable option to elect fair value accounting for the initial and subsequent measurement for certain financial assets and liabilities on a contract-by-contract basis that may otherwise not be required to be measured at fair value under other accounting standards. Washington Trust elected the fair value option for residential real estate mortgage loans held for sale pursuant to forward sale commitments in order to better match changes in fair values of the loans with changes in the fair value of the derivative forward loan sale contracts used to economically hedge them. Changes in the fair value of loans held for sale are recorded in earnings and are offset by changes in fair value relating to forward sale commitments and interest rate lock commitments. For residential mortgage loans intended for sale that are not accounted for under the fair value option, lower of cost or market (“LOCOM”) accounting is applied. Such loans are carried at lower of aggregate cost, net of unamortized deferred loan origination fees and costs, or fair value. Gains and losses on residential loan sales are recognized at the time of sale and included in mortgage banking revenues. Commissions received on mortgage loans brokered to various investors are recognized when received and included in mortgage banking revenues.
Loan Servicing Rights	Loan Servicing Rights Rights to service mortgage loans for others are recognized as an asset, including rights acquired through both purchases and originations. Upon the sale of mortgage loans, a mortgage servicing asset is established, which represents the current estimated fair value based on the present value of estimated future net servicing income. The valuation model incorporates assumptions that market participants would use in estimating future net servicing income, such as the cost to service, the discount rate, ancillary income, prepayment speeds, and default rates and losses. Capitalized loan servicing rights are included in other assets. Mortgage servicing rights are amortized as an offset to mortgage banking revenues over the period of estimated net servicing income. They are periodically evaluated for impairment based on their fair value. Impairment is measured on an aggregated basis by stratifying the rights based on homogeneous characteristics such as note rate and loan type. The fair value is estimated based on the present value of expected cash flows, incorporating assumptions for discount rate, prepayment speed and servicing cost. Any impairment is recognized through a valuation allowance and as a reduction to mortgage banking revenues.
Loans	Loans Portfolio Loans Loans held in the portfolio are stated at the principal amount outstanding, net of unamortized deferred loan origination fees and costs. Interest income is accrued on a level yield basis based on principal amounts outstanding. Deferred loan origination fees and costs are amortized as an adjustment to yield over the life of the related loans. Nonaccrual Loans Loans, with the exception of certain well-secured loans that are in the process of collection, are placed on nonaccrual status and interest recognition is suspended when such loans are 90 days or more overdue with respect to principal and/or interest or sooner if considered appropriate by management. Well-secured loans are permitted to remain on accrual status provided that full collection of principal and interest is assured and the loan is in the process of collection. Loans are also placed on nonaccrual status when, in the opinion of management, full collection of principal and interest is doubtful. When loans are placed on nonaccrual status, interest previously accrued but not collected is reversed against current period income. Subsequent interest payments received on nonaccrual loans are applied to the outstanding principal balance of the loan or recognized as interest income depending on management’s assessment of the ultimate collectability of the loan. Loans are removed from nonaccrual status when they have been current as to principal and interest for a period of time, the borrower has demonstrated an ability to comply with repayment terms, and when, in management’s opinion, the loans are considered to be fully collectible. Impaired Loans Impaired loans are loans for which it is probable that the Corporation will not be able to collect all amounts due according to the contractual terms of the loan agreements and loans restructured in a troubled debt restructuring. Impairment is measured on a discounted cash flow method based upon the loan’s contractual effective interest rate, or at the loan’s observable market price, or if the loan is collateral dependent, at the fair value. For collateral dependent loans for which repayment is dependent on the sale of the collateral, management adjusts the fair value for estimated costs to sell. For collateral dependent loans for which repayment is dependent on the operation of the collateral, such as accruing troubled debt restructured loans, estimated costs to sell are not incorporated into the measurement. Interest income on nonaccrual impaired loans is recognized as described above under the caption “Nonaccrual Loans.” Accruing impaired loans consist of those troubled debt restructurings for which management has concluded that the collectability of the loan is not in doubt. Troubled Debt Restructured Loans Loans are considered to be troubled debt restructurings when the Corporation has granted concessions to a borrower due to the borrower’s financial condition that it otherwise would not have considered. These concessions may include modifications of the terms of the debt such as deferral of payments, extension of maturity, reduction of principal balance, reduction of the stated interest rate other than normal market rate adjustments, or a combination of these concessions. Debt may be bifurcated with separate terms for each tranche of the restructured debt. Restructuring of a loan in lieu of aggressively enforcing the collection of the loan may benefit the Corporation by increasing the ultimate probability of collection. Restructured loans are classified as accruing or non-accruing based on management’s assessment of the collectability of the loan. Loans which are already on nonaccrual status at the time of the restructuring generally remain on nonaccrual status for approximately six months before management considers such loans for return to accruing status. Accruing restructured loans are placed into nonaccrual status if and when the borrower fails to comply with the restructured terms and management deems it unlikely that the borrower will return to a status of compliance in the near term. Troubled debt restructurings are reported as such for at least one year from the date of the restructuring. In years after the restructuring, troubled debt restructured loans are removed from this classification if the restructuring did not involve a below-market rate concession and the loan is not deemed to be impaired based on the terms specified in the restructuring agreement.
Allowance for Loan Losses	Allowance for Loan Losses The allowance for loan losses is management’s best estimate of the risk of loss inherent in the loan portfolio as of the balance sheet date. The allowance is increased by provisions charged to earnings and by recoveries of amounts previously charged off, and is reduced by charge-offs on loans. Loan charge-offs are recognized when management believes the collectability of the principal balance outstanding is unlikely. Full or partial charge-offs on collateral dependent impaired loans are generally recognized when the collateral is deemed to be insufficient to support the carrying value of the loan. The level of the allowance is based on management’s ongoing review of the growth and composition of the loan portfolio, historical loss experience, estimated loss emergence period (the period from the event that triggers the eventual default until the actual loss is recognized with a charge-off), current economic conditions, analysis of asset quality and credit quality levels and trends, the performance of individual loans in relation to contract terms and other pertinent factors. A methodology is used to systematically measure the amount of estimated loan loss exposure inherent in the loan portfolio for the purposes of establishing a sufficient allowance for loan losses. The methodology includes: (1) the identification of loss allocations for individual loans deemed to be impaired and (2) the application of loss allocation factors for non-impaired loans based on historical loss experience and estimated loss emergence period, with adjustments for various exposures that management believes are not adequately represented by historical loss experience. Loss allocations for loans deemed to be impaired are measured on a discounted cash flow method based upon the loan’s contractual effective interest rate, or at the loan’s observable market price, or, if the loan is collateral dependent, at the fair value of the collateral. For collateral dependent loans for which repayment is dependent on the sale of the collateral, management adjusts the fair value for estimated costs to sell. For collateral dependent loans for which repayment is dependent on the operation of the collateral, such as accruing troubled debt restructured loans, estimated costs to sell are not incorporated into the measurement. Management may also adjust appraised values to reflect estimated market value declines or apply other discounts to appraised values for unobservable factors resulting from its knowledge of circumstances associated with the property. For loans that are collectively evaluated, loss allocation factors are derived by analyzing historical loss experience by loan segment over an established look-back period deemed to be relevant to the inherent risk of loss in the portfolios. Loans are segmented by loan type, collateral type, delinquency status and loan risk rating, where applicable. These loss allocation factors are adjusted to reflect the loss emergence period. These amounts are supplemented by certain qualitative risk factors reflecting management’s view of how losses may vary from those represented by historical loss rates. These qualitative risk factors include: 1) changes in lending policies and procedures, including changes in underwriting standards and collection, charge-off, and recovery practices not considered elsewhere in estimating credit losses; 2) changes in international, national, regional, and local economic and business conditions and developments that affect the collectability of the portfolio, including the condition of various market segments; 3) changes in the nature and volume of the portfolio and in the terms of loans; 4) changes in the experience, ability, and depth of lending management and other relevant staff; 5) changes in the volume and severity of past due loans, the volume of nonaccrual loans, and the volume and severity of adversely classified or rated loans; 6) changes in the quality of the institution’s loan review system; 7) changes in the value of underlying collateral for collateral dependent loans; 8) the existence and effect of any concentrations of credit, and changes in the level of such concentrations; and 9) the effect of other external factors such as legal and regulatory requirements on the level of estimated credit losses in the institution’s existing portfolio. Because the methodology is based upon historical experience and trends, current economic data, as well as management’s judgment, factors may arise that result in different estimations. Adversely different conditions or assumptions could lead to increases in the allowance. In addition, various regulatory agencies periodically review the allowance for loan losses. Such agencies may require additions to the allowance based on their judgments about information available to them at the time of their examination. The allowance is an estimate, and ultimate losses may vary from management’s estimate. Changes in the estimate are recorded in the results of operations in the period in which they become known, along with provisions for estimated losses incurred during that period.
Premises and Equipment	Premises and Equipment Premises and equipment are stated at cost less accumulated depreciation. Depreciation for financial reporting purposes is calculated on the straight-line method over the estimated useful lives of assets. Leasehold improvements are depreciated over the shorter of the lease terms or the estimated useful lives of the improvements. Expected terms include lease renewal options to the extent that the exercise of such renewals is reasonably assured. Expenditures for major additions and improvements are capitalized while the costs of current maintenance and repairs are charged to operating expenses. The estimated useful lives of premises and improvements range from 5 to 40 years. For furniture, fixtures and equipment, the estimated useful lives range from 3 to 20 years.
Goodwill and Other Identifiable Intangible Assets	Goodwill and Other Identifiable Intangible Assets The Corporation allocated the cost of acquired entities to the assets acquired and liabilities assumed based on their estimated fair values at the date of acquisition. Other intangible assets identified in acquisitions consist of wealth management advisory contracts. The value attributed to other intangible assets was based on the time period over which they are expected to generate economic benefits. The excess of the purchase price for acquisitions over the fair value of the net assets acquired, including other intangible assets, is recorded as goodwill. Goodwill is not amortized but is tested for impairment at the reporting unit level, defined as the segment level, at least annually in the fourth quarter or more frequently whenever events or circumstances occur that indicate that it is more-likely-than-not that an impairment loss has occurred. In assessing impairment, the Corporation has the option to perform a qualitative analysis to determine whether the existence of events or circumstances leads to a determination that it is more-likely-than-not that the fair value of the reporting unit is less than its carrying amount. If, after assessing the totality of such events or circumstances, we determine it is not more-likely-than-not that the fair value of a reporting unit is less than its carrying amount, then we would not be required to perform an impairment test. Effective April 1, 2017, the Corporation early adopted the provisions of ASU 2017-04 “Simplifying the Test for Goodwill Impairment”, which eliminated Step 2 of the annual two-step goodwill impairment test. Step 2 was a more detailed analysis, which involved measuring the excess of the fair value of the reporting unit, as determined in Step 1, over the aggregate fair value of the individual assets, liabilities, and identifiable intangibles as if the reporting unit was being acquired in a business combination. As Step 2 was eliminated, goodwill is tested for impairment using the quantitative impairment analysis described below. The quantitative impairment analysis requires a comparison of each reporting unit’s fair value to its carrying value to identify potential impairment. Goodwill impairment exists when a reporting unit’s carrying value of goodwill exceeds its implied fair value. Significant judgment is applied when goodwill is assessed for impairment. This judgment includes, but may not be limited to, the selection of appropriate discount rates, the identification of relevant market comparables and the development of cash flow projections. The selection and weighting of the various fair value techniques may result in a higher or lower fair value. Judgment is applied in determining the weightings that are most representative of fair value. Other intangible assets with definite lives are tested for impairment whenever events or circumstances occur that indicate that the carrying amount may not be recoverable. If applicable, the Corporation tests each of the intangibles by comparing the carrying value of the intangible asset to the sum of undiscounted cash flows expected to be generated by the asset. If the carrying amount of the asset exceeded its undiscounted cash flows, then an impairment loss would be recognized for the amount by which the carrying amount exceeds its fair value.
Impairment of Long-Lived Assets Other than Goodwill	Impairment of Long - Lived Assets Other than Goodwill Long-lived assets are reviewed for impairment whenever events or changes in business circumstances indicate that the the carrying amount may not be fully recoverable. If impairment is determined to exist, any related impairment loss is calculated based on fair value. Impairment losses on assets to be disposed of, if any, are based on the estimated proceeds to be received, less costs of disposal.
Property Acquired through Foreclosure or Repossession	Property Acquired through Foreclosure or Repossession Property acquired through foreclosure or repossession is carried at the lower of cost or fair value less estimated costs to sell. Fair value of such assets is determined based on independent appraisals and other relevant factors. Any write-down to fair value at the time of foreclosure or repossession is charged to the allowance for loan losses. A valuation allowance is maintained for declines in market value and for estimated selling expenses. Increases to the valuation allowance, expenses associated with ownership of these properties, and gains and losses from their sale are included in foreclosed property costs. Loans that are substantively repossessed include only those loans for which the Corporation has obtained control of the collateral, but has not completed legal foreclosure proceedings.
Bank-Owned Life Insurance	Bank-Owned Life Insurance The investment in BOLI represents the cash surrender value of life insurance policies on the lives of certain employees who have provided positive consent allowing the Bank to be the beneficiary of such policies. Increases in the cash value of the policies, as well as insurance proceeds received, are recorded in noninterest income and are not subject to income taxes. The financial strength of the insurance carrier is reviewed prior to the purchase of BOLI and annually thereafter.
Investment in Real Estate Limited Partnership	Investment in Real Estate Limited Partnership Washington Trust has a 99.9% ownership interest in two real estate limited partnerships that renovate, own and operate two low-income housing complexes. Washington Trust neither actively participates nor has a controlling interest in these limited partnerships and accounts for its investments under the equity method of accounting. The carrying value of the investments is recorded in other assets on the Consolidated Balance Sheet. Net losses generated by the partnership are recorded as a reduction to Washington Trust’s investment and as a reduction of other noninterest income in the Consolidated Statements of Income. Tax credits generated by the partnership are recorded as a reduction in the income tax provision in the year they are allowed for tax reporting purposes. The results of operations of the real estate limited partnerships are periodically reviewed to determine if the partnership generates sufficient operating cash flow to fund its current obligations. In addition, the current value of the underlying properties is compared to the outstanding debt obligations. If it is determined that the investment is permanently impaired, the carrying value will be written down to the estimated realizable value.
Transfers and Servicing of Assets and Extinguishments of Liabilities	Transfers and Servicing of Assets and Extinguishments of Liabilities The accounting for transfers and servicing of financial assets and extinguishments of liabilities is based on consistent application of a financial components approach that focuses on control. This approach distinguishes transfers of financial assets that are sales from transfers that are secured borrowings. After a transfer of financial assets, the Corporation recognizes all financial and servicing assets it controls and liabilities it has incurred and derecognizes financial assets it no longer controls and liabilities that have been extinguished. This financial components approach focuses on the assets and liabilities that exist after the transfer. Many of these assets and liabilities are components of financial assets that existed prior to the transfer. If a transfer does not meet the criteria for a sale, the transfer is accounted for as a secured borrowing with a pledge of collateral.
Wealth Management Assets Under Administration	Wealth Management Assets Under Administration Assets under administration represent assets held in a fiduciary or agency capacity for wealth management clients and are not included in the Consolidated Balance Sheets, as these are not assets of the Corporation. Wealth management revenue derived from the administration, management and custody of assets under administration are referred to as asset-based revenues.
Fee Revenue	Fee Revenue Wealth management revenues include asset-based revenues that are primarily accrued as earned based upon a percentage of asset values under administration. Also included in wealth management revenues are transaction-based revenues, which include financial planning fees, tax preparation fees, commissions and other service fees, which are recognized as revenue to the extent that services have been completed. Fee revenue from deposit service charges is generally recognized when earned.
Pension Costs	Pension Costs Pension benefits are accounted for using the net periodic benefit cost method, which recognizes the compensation cost of an employee’s pension benefit over that employee’s approximate service period. Pension benefit costs and benefit obligations incorporate various actuarial and other assumptions, including discount rates, mortality, rates of return on plan assets and compensation increases. Washington Trust evaluates these assumptions on an annual basis and makes modifications to the assumptions based on current rates and trends when it is appropriate to so do. The effect of modifications to those assumptions is recorded in other comprehensive income (loss) and amortized to net periodic cost over future periods. Washington Trust believes that the assumptions utilized in recording its obligations under its plans are reasonable based on its experience and market conditions. The funded status of defined benefit pension plans, measured as the difference between the fair value of plan assets and the projected benefit obligation, is recognized in the Consolidated Balance Sheet. The changes in the funded status of the defined benefit plans, including actuarial gains and losses and prior service costs and credits, are recognized in comprehensive income in the year in which the changes occur.
Share-Based Compensation	Share-Based Compensation Share-based compensation plans provide for awards of stock options and other equity incentives, including nonvested share units and nonvested performance share units. Compensation expense for awards is recognized over the service period based on the fair value at the date of grant. The Corporation estimates grant date fair value for stock options using the Black-Scholes option-pricing model. Awards of nonvested share units and nonvested performance share units are valued at the fair market value of the Bancorp’s common stock as of the award date. Nonvested performance share unit compensation expense is based on the most recent performance assumption available and is adjusted as assumptions change. If the goals are not met, no compensation cost will be recognized and any recognized compensation costs will be reversed. Effective January 1, 2017, excess tax benefits (expenses) related to stock option exercises, settlement of other equity awards and dividends paid on nonvested share awards are recorded as a decrease (increase) to income tax expense. Prior to 2017, such excess tax benefits were recognized as additional paid in capital in shareholders' equity and did not impact income tax expense. Excess tax benefits (expenses) on the settlement of share-based awards are reflected in the Consolidated Statements of Cash Flows as an operating activity.
Income Taxes	Income Taxes Income tax expense is determined based on the asset and liability method, whereby deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The Corporation recognizes the effect of income tax positions only if those positions are more likely than not of being sustained. Recognized income tax positions are measured at the largest amount that is greater than 50% likely of being realized. Changes in recognition or measurement are reflected in the period in which the change in judgment occurs. The Corporation records interest related to unrecognized tax benefits in income tax expense. Penalties, if incurred, would be recognized as a component of income tax expense.
Segment Reporting	Segment Reporting Washington Trust segregates financial information in assessing its results among its Commercial Banking and Wealth Management Services operating segments. The amounts in the Corporate unit include activity not related to the segments. The methodologies and organizational hierarchies that define the business segments are periodically reviewed and revised. Results may be restated, when necessary, to reflect changes in organizational structure or allocation methodology. Any changes in estimates and allocations that may affect the reported results of any business segment will not affect the consolidated financial position or results of operations of Washington Trust as a whole. Management uses certain methodologies to allocate income and expenses to the business lines. A funds transfer pricing (“FTP”) methodology is used to assign interest income and interest expense to each interest-earning asset and interest-bearing liability on a matched maturity funding basis. The matched maturity funding concept considers the origination date and the earlier of the maturity date or the repricing date of a financial instrument to assign an FTP rate for loans and deposits originated. Loans are assigned a FTP rate for funds used and deposits are assigned a FTP rate for funds provided. Certain indirect expenses are allocated to segments. These include support unit expenses such as technology, operations and other support functions.
Earnings Per Share (EPS)	Earnings Per Share (“EPS”) The Corporation utilizes the two-class method earnings allocation formula to determine earnings per share of each class of stock according to dividends and participation rights in undistributed earnings. Share based payments that entitle holders to receive non-forfeitable dividends before vesting are considered participating securities and included in earnings allocation for computing basic earnings per share under this method. Undistributed income is allocated to common shareholders and participating securities under the two-class method based upon the proportion of each to the total weighted average shares available. Under the two-class method, basic earnings per common share is computed by dividing net earnings allocated to common stock by the weighted-average number of common shares outstanding. Diluted earnings per common share is computed using the weighted-average number of shares determined for the basic earnings per common share computation plus the dilutive effect of common stock equivalents.
Comprehensive Income	Comprehensive Income Comprehensive income is defined as all changes in equity, except for those resulting from transactions with shareholders. Net income is a component of comprehensive income. All other components are referred to in the aggregate as other comprehensive income (loss) .
Guarantees	Guarantees Standby letters of credit are considered a guarantee of the Corporation. Standby letters of credit are conditional commitments issued to guarantee the performance of a customer to a third party. The credit risk involved in issuing standby letters of credit is essentially the same as that involved in extending loan facilities to customers. Under the standby letters of credit, the Corporation is required to make payments to the beneficiary of the letters of credit upon request by the beneficiary contingent upon the customer’s failure to perform under the terms of the underlying contract with the beneficiary.
Derivative Insturments and Hedging Activities	Derivative Instruments and Hedging Activities Derivatives are recognized as either assets or liabilities on the balance sheet and are measured at fair value. The accounting for changes in the fair value of derivatives depends on the intended use of the derivative and resulting designation. For derivatives designated as cash flow hedges, the effective portion of changes in the fair value of the derivative are recorded in other comprehensive income (loss) and subsequently reclassified to earnings when gains or losses are realized. The ineffective portion of changes in the fair value is recognized directly in earnings as interest income or interest expense based on the item being hedged. For derivatives not designated as hedges, changes in fair value of the derivative instruments are recognized in earnings, in noninterest income. The accrued net settlements on derivatives that qualify for hedge accounting are recorded in interest income or interest expense based on the item being hedged. Changes in fair value of derivatives including accrued net settlements that do not qualify for hedge accounting are reported in noninterest income. When a cash flow hedge is discontinued, but the hedged cash flows or forecasted transaction is still expected to occur, changes in value that were accumulated in other comprehensive income (loss) are amortized or accreted into earnings over the same periods which the hedged transactions will affect earnings. By using certain derivative financial instruments, the Corporation exposes itself to credit risk. Credit risk is the failure of the counterparty to perform under the terms of the derivative contract. When the fair value of a derivative contract is positive, the counterparty owes the Corporation, which creates credit risk for the Corporation. When the fair value of a derivative contract is negative, the Corporation owes the counterparty and, therefore, it does not possess credit risk. The credit risk in derivative instruments is minimized by entering into transactions with highly rated counterparties that management believes to be creditworthy.
Fair Value Measurements	Fair Value Measurements Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. ASC Topic 820, “Fair Value Measurements and Disclosures”, establishes a framework for measuring fair value and expands disclosures about fair value measurements. The required disclosures about fair value measurements have been included in Note 15 .

Securities (Tables)

Securities (Tables)	12 Months Ended
	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Summary of Investments	The following tables present the amortized cost, gross unrealized holding gains, gross unrealized holding losses and fair value of securities by major security type and class of security: (Dollars in thousands) December 31, 2017 Amortized Cost Unrealized Gains Unrealized Losses Fair Value Securities Available for Sale: Obligations of U.S. government-sponsored enterprises $161,479 $— ($3,875 ) $157,604 Mortgage-backed securities issued by U.S. government agencies and U.S. government-sponsored enterprises 594,944 3,671 (7,733 ) 590,882 Obligations of states and political subdivisions 2,355 4 — 2,359 Individual name issuer trust preferred debt securities 18,106 — (1,122 ) 16,984 Corporate bonds 13,917 13 (805 ) 13,125 Total securities available for sale $790,801 $3,688 ($13,535 ) $780,954 Held to Maturity: Mortgage-backed securities issued by U.S. government agencies and U.S. government-sponsored enterprises $12,541 $180 $— $12,721 Total securities held to maturity 12,541 180 — 12,721 Total securities $803,342 $3,868 ($13,535 ) $793,675 (Dollars in thousands) December 31, 2016 Amortized Cost Unrealized Gains Unrealized Losses Fair Value Securities Available for Sale: Obligations of U.S. government-sponsored enterprises $111,483 $7 ($3,050 ) $108,440 Mortgage-backed securities issued by U.S. government agencies and U.S. government-sponsored enterprises 592,833 4,923 (9,671 ) 588,085 Obligations of states and political subdivisions 14,423 62 — 14,485 Individual name issuer trust preferred debt securities 29,851 — (3,115 ) 26,736 Corporate bonds 2,155 16 (5 ) 2,166 Total securities available for sale $750,745 $5,008 ($15,841 ) $739,912 Held to Maturity: Mortgage-backed securities issued by U.S. government agencies and U.S. government-sponsored enterprises $15,633 $287 $— $15,920 Total securities held to maturity 15,633 287 — 15,920 Total securities $766,378 $5,295 ($15,841 ) $755,832
Securities by Contractual Maturity	The schedule of maturities of debt securities available for sale and held to maturity is presented below. Mortgage-backed securities are included based on weighted average maturities, adjusted for anticipated prepayments. All other debt securities are included based on contractual maturities. Actual maturities may differ from amounts presented because certain issuers have the right to call or prepay obligations with or without call or prepayment penalties. (Dollars in thousands) Available for Sale Held to Maturity December 31, 2017 Amortized Cost Fair Value Amortized Cost Fair Value Due in one year or less $62,120 $61,700 $1,719 $1,743 Due after one year to five years 247,054 244,392 5,374 5,451 Due after five years to ten years 285,543 280,870 4,019 4,077 Due after ten years 196,084 193,992 1,429 1,450 Total securities $790,801 $780,954 $12,541 $12,721 Included in the above table were debt securities with an amortized cost balance of $195.4 million and a fair value of $189.7 million at December 31, 2017 that are callable at the discretion of the issuers. Final maturities of the callable securities range from 5 months to 19 years, with call features ranging from 1 month to 4 years.
Securities in a Continuous Unrealized Loss Position	The following tables summarize temporarily impaired securities, segregated by length of time the securities have been in a continuous unrealized loss position: (Dollars in thousands) Less than 12 Months 12 Months or Longer Total December 31, 2017 # Fair Value Unrealized Losses # Fair Value Unrealized Losses # Fair Value Unrealized Losses Obligations of U.S. government-sponsored enterprises 8 $69,681 ($798 ) 8 $87,923 ($3,077 ) 16 $157,604 ($3,875 ) Mortgage-backed securities issued by U.S. government agencies and U.S. government-sponsored enterprises 20 128,965 (613 ) 22 279,693 (7,120 ) 42 408,658 (7,733 ) Individual name issuer trust preferred debt securities — — — 7 16,984 (1,122 ) 7 16,984 (1,122 ) Corporate bonds 3 921 (5 ) 3 10,980 (800 ) 6 11,901 (805 ) Total temporarily impaired securities 31 $199,567 ($1,416 ) 40 $395,580 ($12,119 ) 71 $595,147 ($13,535 ) (Dollars in thousands) Less than 12 Months 12 Months or Longer Total December 31, 2016 # Fair Value Unrealized Losses # Fair Value Unrealized Losses # Fair Value Unrealized Losses Obligations of U.S. government-sponsored enterprises 10 $98,433 ($3,050 ) — $— $— 10 $98,433 ($3,050 ) Mortgage-backed securities issued by U.S. government agencies and U.S. government-sponsored enterprises 35 407,073 (9,671 ) — — — 35 407,073 (9,671 ) Individual name issuer trust preferred debt securities — — — 10 26,736 (3,115 ) 10 26,736 (3,115 ) Corporate bonds 2 400 (5 ) — — — 2 400 (5 ) Total temporarily impaired securities 47 $505,906 ($12,726 ) 10 $26,736 ($3,115 ) 57 $532,642 ($15,841 )

Loans (Tables)

Loans (Tables)	12 Months Ended
	Dec. 31, 2017
Receivables [Abstract]
Summary of Loans	The following is a summary of loans: (Dollars in thousands) December 31, 2017 December 31, 2016 Amount % Amount % Commercial: Mortgages (1) $1,072,487 32 % $1,074,186 33 % Construction & development (2) 138,008 4 121,371 4 Commercial & industrial (3) 612,334 18 576,109 18 Total commercial 1,822,829 54 1,771,666 55 Residential real estate: Mortgages 1,206,458 35 1,094,824 34 Homeowner construction 20,790 1 27,924 1 Total residential real estate 1,227,248 36 1,122,748 35 Consumer: Home equity lines 258,114 8 264,200 8 Home equity loans 34,353 1 37,272 1 Other (4) 31,527 1 38,485 1 Total consumer 323,994 10 339,957 10 Total loans (5) $3,374,071 100 % $3,234,371 100 % (1) Loans primarily secured by income producing property. (2) Loans for construction of commercial properties, loans to developers for construction of residential properties and loans for land development. (3) Loans to businesses and individuals, a substantial portion of which are fully or partially collateralized by real estate. (4) Loans to individuals secured by general aviation aircraft and other personal installment loans. (5) Includes net unamortized loan origination costs of $3.8 million and $3.0 million , respectively, and net unamortized premiums on purchased loans of $878 thousand and $783 thousand , respectively, at December 31, 2017 and 2016 .
Nonaccrual Loans	The following is a summary of nonaccrual loans, segregated by class of loans: (Dollars in thousands) December 31, 2017 2016 Commercial: Mortgages $4,954 $7,811 Construction & development — — Commercial & industrial 283 1,337 Residential real estate: Mortgages 9,414 11,736 Homeowner construction — — Consumer: Home equity lines 81 — Home equity loans 463 1,058 Other 16 116 Total nonaccrual loans $15,211 $22,058 Accruing loans 90 days or more past due $— $—
Past Due Loans	The following tables present an aging analysis of past due loans, segregated by class of loans: (Dollars in thousands) Days Past Due December 31, 2017 30-59 60-89 Over 90 Total Past Due Current Total Loans Commercial: Mortgages $6 $— $4,954 $4,960 $1,067,527 $1,072,487 Construction & development — — — — 138,008 138,008 Commercial & industrial 3,793 2 281 4,076 608,258 612,334 Residential real estate: Mortgages 1,678 2,274 3,903 7,855 1,198,603 1,206,458 Homeowner construction — — — — 20,790 20,790 Consumer: Home equity lines 1,340 — — 1,340 256,774 258,114 Home equity loans 1,458 75 268 1,801 32,552 34,353 Other 29 — 14 43 31,484 31,527 Total loans $8,304 $2,351 $9,420 $20,075 $3,353,996 $3,374,071 (Dollars in thousands) Days Past Due December 31, 2016 30-59 60-89 Over 90 Total Past Due Current Total Loans Commercial: Mortgages $901 $— $7,807 $8,708 $1,065,478 $1,074,186 Construction & development — — — — 121,371 121,371 Commercial & industrial 409 — 745 1,154 574,955 576,109 Residential real estate: Mortgages 5,381 652 6,193 12,226 1,082,598 1,094,824 Homeowner construction — — — — 27,924 27,924 Consumer: Home equity lines 655 26 — 681 263,519 264,200 Home equity loans 776 76 658 1,510 35,762 37,272 Other 32 1 110 143 38,342 38,485 Total loans $8,154 $755 $15,513 $24,422 $3,209,949 $3,234,371
Impaired Loans	The following is a summary of impaired loans: (Dollars in thousands) Recorded Investment (1) Unpaid Principal Related Allowance December 31, 2017 2016 2017 2016 2017 2016 No Related Allowance Recorded: Commercial: Mortgages $— $4,676 $— $9,019 $— $— Construction & development — — — — — — Commercial & industrial 4,986 6,458 5,081 6,550 — — Residential real estate: Mortgages 9,069 14,385 9,256 14,569 — — Homeowner construction — — — — — — Consumer: Home equity lines 81 — 81 — — — Home equity loans 476 1,137 476 1,177 — — Other 14 116 14 116 — — Subtotal 14,626 26,772 14,908 31,431 — — With Related Allowance Recorded: Commercial: Mortgages 4,954 5,104 9,910 6,087 1,018 448 Construction & development — — — — — — Commercial & industrial 191 662 212 699 1 3 Residential real estate: Mortgages 715 1,285 741 1,310 104 151 Homeowner construction — — — — — — Consumer: Home equity lines — — — — — — Home equity loans — — — — — — Other 133 28 132 29 6 4 Subtotal 5,993 7,079 10,995 8,125 1,129 606 Total impaired loans $20,619 $33,851 $25,903 $39,556 $1,129 $606 Total: Commercial $10,131 $16,900 $15,203 $22,355 $1,019 $451 Residential real estate 9,784 15,670 9,997 15,879 104 151 Consumer 704 1,281 703 1,322 6 4 Total impaired loans $20,619 $33,851 $25,903 $39,556 $1,129 $606 (1) The recorded investment in impaired loans consists of unpaid principal balance, net of charge-offs, interest payments received applied to principal and unamortized deferred loan origination fees and costs. For accruing impaired loans (troubled debt restructurings for which management has concluded that the collectability of the loan is not in doubt), the recorded investment also includes accrued interest. The following table presents the average recorded investment balance of impaired loans and interest income recognized on impaired loans segregated by loan class: (Dollars in thousands) Average Recorded Investment Interest Income Recognized Years ended December 31, 2017 2016 2015 2017 2016 2015 Commercial: Mortgages $8,425 $13,201 $14,847 $79 $239 $327 Construction & development — — — — — — Commercial & industrial 6,445 3,540 3,415 281 99 130 Residential real estate: Mortgages 14,571 12,848 5,423 444 322 147 Homeowner construction — — — — — — Consumer: Home equity lines 79 354 228 7 10 1 Home equity loans 606 1,233 487 24 38 11 Other 143 147 210 10 11 10 Totals $30,269 $31,323 $24,610 $845 $719 $626
Troubled Debt Restructurings	The following table presents loans modified as a troubled debt restructuring: (Dollars in thousands) Outstanding Recorded Investment (1) # of Loans Pre-Modifications Post-Modifications Years ended December 31, 2017 2016 2017 2016 2017 2016 Commercial: Mortgages — 1 $— $776 $— $776 Construction & development — — — — — — Commercial & industrial — 9 — 6,229 — 6,229 Residential real estate: Mortgages — 3 — 4,386 — 4,386 Homeowner construction — — — — — — Consumer: Home equity lines — — — — — — Home equity loans — — — — — — Other — — — — — — Totals — 13 $— $11,391 $— $11,391 (1) The recorded investment in troubled debt restructurings consists of unpaid principal balance, net of charge-offs and unamortized deferred loan origination fees and costs, at the time of the restructuring. For accruing troubled debt restructured loans, the recorded investment also includes accrued interest.
Troubled Debt Restructurings, Type of Modification	The following table provides information on how loans were modified as a troubled debt restructuring: (Dollars in thousands) Years ended December 31, 2017 2016 Below-market interest rate concession $— $— Payment deferral — 1,111 Maturity / amortization concession — 683 Interest only payments — 4,326 Combination (1) — 5,271 Total $— $11,391 (1) Loans included in this classification were modified with a combination of any two of the concessions listed in this table.
Credit Quality Indicators - Commercial	The following table presents the commercial loan portfolio, segregated by category of credit quality indicator: (Dollars in thousands) Pass Special Mention Classified December 31, 2017 2016 2017 2016 2017 2016 Mortgages $1,067,373 $1,065,358 $— $776 $5,114 $8,052 Construction & development 138,008 121,371 — — — — Commercial & industrial 592,749 559,416 9,804 8,938 9,781 7,755 Total commercial loans $1,798,130 $1,746,145 $9,804 $9,714 $14,895 $15,807
Credit Quality Indicators - Residential & Consumer	The following table presents the residential and consumer loan portfolios, segregated by category of credit quality indicator: (Dollars in thousands) Current Past Due December 31, 2017 2016 2017 2016 Residential real estate: Self-originated mortgages $1,070,501 $954,867 $6,413 $11,017 Purchased mortgages 128,102 127,731 1,442 1,209 Homeowner construction 20,790 27,924 — — Total residential loans $1,219,393 $1,110,522 $7,855 $12,226 Consumer: Home equity lines $256,774 $263,519 $1,340 $681 Home equity loans 32,552 35,762 1,801 1,510 Other 31,484 38,342 43 143 Total consumer loans $320,810 $337,623 $3,184 $2,334
Analysis of Loan Servicing Rights	The following table presents an analysis of loan servicing rights: (Dollars in thousands) Loan Servicing Rights Valuation Allowance Total Balance at December 31, 2014 $2,989 ($2 ) $2,987 Loan servicing rights capitalized 1,406 — 1,406 Amortization (1,047 ) — (1,047 ) Decrease in impairment reserve — 1 1 Balance at December 31, 2015 3,348 (1 ) 3,347 Loan servicing rights capitalized 1,412 — 1,412 Amortization (1,267 ) — (1,267 ) Decrease in impairment reserve — 1 1 Balance at December 31, 2016 3,493 — 3,493 Loan servicing rights capitalized 1,104 — 1,104 Amortization (984 ) — (984 ) Decrease in impairment reserve — — — Balance at December 31, 2017 $3,613 $— $3,613
Amortization Expense Related to Loan Servicing Assets	The following table presents estimated aggregate amortization expense related to loan servicing assets: (Dollars in thousands) Years ending December 31: 2018 $899 2019 675 2020 507 2021 381 2022 286 Thereafter 865 Total estimated amortization expense $3,613
Loans Serviced for Others, by Type of Loan	The following table presents the balance of loans serviced for others by type of loan: (Dollars in thousands) December 31, 2017 2016 Residential mortgages $568,311 $522,766 Commercial loans 108,539 101,317 Total $676,850 $624,083

Allowance for Loan Losses (Tabl

Allowance for Loan Losses (Tables)	12 Months Ended
	Dec. 31, 2017
Receivables [Abstract]
Allowance for Loan Losses Rollforward Analysis	The following table presents the activity in the allowance for loan losses for the year ended December 31, 2017 : (Dollars in thousands) Commercial Mortgages Construction C&I (1) Total Commercial Residential Consumer Total Beginning Balance $9,971 $1,195 $6,992 $18,158 $5,252 $2,594 $26,004 Charge-offs (1,867 ) — (336 ) (2,203 ) (74 ) (185 ) (2,462 ) Recoveries 82 — 169 251 39 56 346 Provision 3,460 (112 ) (1,245 ) 2,103 210 287 2,600 Ending Balance $11,646 $1,083 $5,580 $18,309 $5,427 $2,752 $26,488 (1) Commercial & industrial loans. The following table presents the activity in the allowance for loan losses for the year ended December 31, 2016 : (Dollars in thousands) Commercial Mortgages Construction C&I (1) Total Commercial Residential Consumer Total Beginning Balance $9,140 $1,758 $8,202 $19,100 $5,460 $2,509 $27,069 Charge-offs (5,816 ) — (759 ) (6,575 ) (200 ) (237 ) (7,012 ) Recoveries 56 — 156 212 11 74 297 Provision 6,591 (563 ) (607 ) 5,421 (19 ) 248 5,650 Ending Balance $9,971 $1,195 $6,992 $18,158 $5,252 $2,594 $26,004 (1) Commercial & industrial loans. The following table presents the activity in the allowance for loan losses for the year ended December 31, 2015 : (Dollars in thousands) Commercial Mortgages Construction C&I (1) Total Commercial Residential Consumer Unallocated Total Beginning Balance $8,202 $1,300 $7,987 $17,489 $5,430 $2,713 $2,391 $28,023 Charge-offs (809 ) — (671 ) (1,480 ) (207 ) (618 ) — (2,305 ) Recoveries 92 — 87 179 28 94 — 301 Provision 1,655 458 799 2,912 209 320 (2,391 ) 1,050 Ending Balance $9,140 $1,758 $8,202 $19,100 $5,460 $2,509 $— $27,069 (1) Commercial & industrial loans.
Schedule of Allowance for Loan Loss by Segment & Impairment Methodology	The following table presents the Corporation’s loan portfolio and associated allowance for loan losses by portfolio segment and by impairment methodology. (Dollars in thousands) December 31, 2017 December 31, 2016 Related Allowance Related Allowance Loans Loans Loans Individually Evaluated For Impairment: Commercial: Mortgages $4,954 $1,018 $9,776 $448 Construction & development — — — — Commercial & industrial 5,157 1 7,098 3 Residential Real Estate 9,783 104 15,661 151 Consumer 704 6 1,280 4 Subtotal 20,598 1,129 33,815 606 Loans Collectively Evaluated For Impairment: Commercial: Mortgages 1,067,533 10,628 1,064,410 9,523 Construction & development 138,008 1,083 121,371 1,195 Commercial & industrial 607,177 5,579 569,011 6,989 Residential Real Estate 1,217,465 5,323 1,107,087 5,101 Consumer 323,290 2,746 338,677 2,590 Subtotal 3,353,473 25,359 3,200,556 25,398 Total $3,374,071 $26,488 $3,234,371 $26,004

Premises and Equipment (Tables)

Premises and Equipment (Tables)	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Summary of Premises and Equipment	The following presents a summary of premises and equipment: (Dollars in thousands) December 31, 2017 2016 Land and improvements $6,020 $6,020 Premises and improvements 38,793 37,913 Furniture, fixtures and equipment 26,240 28,383 Total premises and equipment 71,053 72,316 Less accumulated depreciation 42,720 43,296 Total premises and equipment, net $28,333 $29,020

Goodwill and Other Intangibles

Goodwill and Other Intangibles (Tables)	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Carrying Value of Goodwill	The following table presents the carrying value of goodwill at the reporting unit (or business segment) level: (Dollars in thousands) Commercial Banking Wealth Management Services Total Balance at December 31, 2016 $22,591 $41,468 $64,059 Impairment — (150 ) (150 ) Balance at December 31, 2017 $22,591 $41,318 $63,909
Schedule of Carrying Value of Other Intangible Assets	The following table presents the components of intangible assets: (Dollars in thousands) December 31, 2017 December 31, 2016 Advisory Contracts Non-compete Agreements Advisory Contracts Non-compete Agreements Gross carrying amount $20,803 $369 $20,803 $369 Accumulated amortization 11,663 369 10,648 349 Net amount $9,140 $— $10,155 $20
Schedule of Estimated Annual Amortization Expense	The following table presents estimated annual amortization expense for intangible assets at December 31, 2017 : (Dollars in thousands) Years ending December 31, 2018 $979 2019 943 2020 914 2021 890 2022 860 2023 and thereafter 4,554

Income Tax Expense (Tables)

Income Tax Expense (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Schedule of Components of Income Tax Expense	The following table presents the components of income tax expense: (Dollars in thousands) Years ended December 31, 2017 2016 2015 Current tax expense: Federal $23,827 $19,444 $17,864 State 2,201 2,061 1,194 Total current tax expense 26,028 21,505 19,058 Deferred tax expense (benefit): Federal 5,717 796 2,003 State (30 ) 72 (183 ) Total deferred tax expense 5,687 868 1,820 Total income tax expense $31,715 $22,373 $20,878
Schedule of Effective Income Tax Rate Reconciliation	Total income tax expense varies from the amount determined by applying the Federal income tax rate to income before income taxes. The following table presents the reasons for the differences: (Dollars in thousands) Years ended December 31, 2017 2016 2015 Tax expense at Federal statutory rate $27,174 $24,099 $22,520 (Decrease) increase in taxes resulting from: Tax-exempt income (1,313 ) (1,599 ) (1,604 ) Dividends received deduction (55 ) (58 ) (57 ) BOLI (757 ) (930 ) (694 ) Stock based compensation (481 ) — — Federal tax credits (364 ) (364 ) (364 ) Change in fair value of contingent consideration (225 ) (314 ) — Acquisition related expenses — — 318 State income tax expense, net of federal income tax benefit 1,411 1,387 658 Adjustment to net deferred tax assets for enacted changes in federal tax law 6,170 — — Other 155 152 101 Total income tax expense $31,715 $22,373 $20,878
Schedule of Deferred Tax Assets and Liabilities	The following table presents the approximate tax effects of temporary differences that give rise to deferred tax assets and deferred tax liabilities: (Dollars in thousands) December 31, 2017 2016 Deferred tax assets: Allowance for loan losses $6,225 $9,621 Defined benefit pension obligations 1,767 3,804 Deferred compensation 3,334 3,991 Deferred loan origination fees 1,325 1,999 Stock based compensation 1,240 1,519 Net unrealized losses on securities available for sale 2,314 4,008 Other 2,281 3,495 Deferred tax assets 18,486 28,437 Deferred tax liabilities: Amortization of intangibles (2,148 ) (3,765 ) Deferred loan origination costs (3,550 ) (5,156 ) Loan servicing rights (849 ) (1,293 ) Other (1,200 ) (1,419 ) Deferred tax liabilities (7,747 ) (11,633 ) Net deferred tax asset $10,739 $16,804

Time Certificates of Deposit (T

Time Certificates of Deposit (Tables)	12 Months Ended
	Dec. 31, 2017
Deposits [Abstract]
Schedule of Time Certificates of Deposit Maturities	The following table presents scheduled maturities of time certificates of deposit: (Dollars in thousands) Scheduled Maturity Weighted Average Rate Years ending December 31: 2018 $479,914 0.96 % 2019 323,597 1.51 2020 90,282 1.54 2021 59,263 1.77 2022 61,991 1.94 2023 and thereafter 48 1.30 Balance at December 31, 2017 $1,015,095 1.30 %
Schedule of Time Certificates of Deposit $100 Thousand or More Maturities	The following table presents the amount of time certificates of deposit in denominations of $100 thousand or more at December 31, 2017 , maturing during the periods indicated: (Dollars in thousands) January 1, 2018 to March 31, 2018 $100,142 April 1, 2018 to June 30, 2018 21,824 July 1, 2018 to December 31, 2018 35,239 January 1, 2019 and beyond 172,083 Balance at December 31, 2017 $329,288

Borrowings (Tables)

Borrowings (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
FHLBB Advances Maturity Summary	The following table presents scheduled maturities and weighted average interest rates on FHLB advances outstanding as of December 31, 2017 : (Dollars in thousands) Scheduled Maturity Weighted Average Rate 2018 $465,634 1.51 % 2019 137,258 1.62 2020 67,033 1.95 2021 51,222 2.43 2022 55,447 3.58 2023 and thereafter 14,762 2.44 Total $791,356 1.85 %
Schedule of Short-Term FHLBB Advances	The following table presents certain information concerning short-term FHLB advances: (Dollars in thousands) As of and for the years ended December 31, 2017 2016 2015 Average amount outstanding during the period $351,692 $275,533 $155,874 Amount outstanding at end of period $367,500 $352,500 $107,500 Highest month end balance during period $417,500 $367,500 $229,500 Weighted-average interest rate at end of period 1.57 % 0.79 % 0.55 % Weighted-average interest rate during the period 1.20 % 0.73 % 0.38 %

Shareholders' Equity (Tables)

Shareholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Regulatory Capital Requirements	The following table presents the Corporation’s and the Bank’s actual capital amounts and ratios, as well as the corresponding minimum and well capitalized regulatory amounts and ratios that were in effect during the respective periods: (Dollars in thousands) Actual For Capital Adequacy Purposes To Be “Well Capitalized” Under Prompt Corrective Action Regulations Amount Ratio Amount Ratio Amount Ratio December 31, 2017 Total Capital (to Risk-Weighted Assets): Corporation $416,038 12.45 % $267,365 8.00 % N/A N/A Bank 413,593 12.38 267,338 8.00 334,172 10.00 Tier 1 Capital (to Risk-Weighted Assets): Corporation 389,289 11.65 200,524 6.00 N/A N/A Bank 386,844 11.58 200,503 6.00 267,338 8.00 Common Equity Tier 1 Capital (to Risk-Weighted Assets): Corporation 367,291 10.99 150,383 4.50 N/A N/A Bank 386,844 11.58 150,378 4.50 217,212 6.50 Tier 1 Capital (to Average Assets): (1) Corporation 389,289 8.79 177,089 4.00 N/A N/A Bank 386,844 8.74 177,048 4.00 221,310 5.00 December 31, 2016 Total Capital (to Risk-Weighted Assets): Corporation 390,867 12.26 255,093 8.00 N/A N/A Bank 389,840 12.23 255,050 8.00 318,813 10.00 Tier 1 Capital (to Risk-Weighted Assets): Corporation 364,655 11.44 191,320 6.00 N/A N/A Bank 363,628 11.41 191,288 6.00 255,050 8.00 Common Equity Tier 1 Capital (to Risk-Weighted Assets): Corporation 342,656 10.75 143,490 4.50 N/A N/A Bank 363,628 11.41 143,466 4.50 207,228 6.50 Tier 1 Capital (to Average Assets): (1) Corporation 364,655 8.67 168,271 4.00 N/A N/A Bank 363,628 8.65 168,207 4.00 210,259 5.00 (1) Leverage ratio.

Derivative Financial Instrume41

Derivative Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Fair Value of Derivatives by Balance Sheet Location	The following table presents the fair values of derivative instruments in the Corporation’s Consolidated Balance Sheets: (Dollars in thousands) Asset Derivatives Liability Derivatives Fair Value Fair Value December 31, Balance Sheet Location 2017 2016 Balance Sheet Location 2017 2016 Derivatives Designated as Cash Flow Hedging Instruments: Interest rate risk management contracts: Interest rate swaps Other assets $213 $— Other liabilities $14 $378 Interest rate caps Other assets 25 134 Other liabilities — — Interest rate floors Other assets 110 — Other liabilities — — Derivatives not Designated as Hedging Instruments: Forward loan commitments: Interest rate lock commitments Other assets 965 1,133 Other liabilities 20 88 Commitments to sell mortgage loans Other assets 26 279 Other liabilities 1,424 1,349 Loan related derivative contracts: Interest rate swaps with customers Other assets 268 2,036 Other liabilities 1,295 — Mirror swaps with counterparties Other assets 1,152 — Other liabilities 268 2,228 Risk participation agreements Other assets — — Other liabilities — — Foreign exchange contracts Other assets — — Other liabilities 26 — Total $2,759 $3,582 $3,047 $4,043
Derivative Instruments Effect in Statements of Income and Changes in Shareholders' Equity	The following tables present the effect of derivative instruments in the Corporation’s Consolidated Statements of Changes in Shareholders’ Equity and Consolidated Statements of Income: (Dollars in thousands) Gain (Loss) Recognized in Other Comprehensive Income, Net of Tax (Effective Portion) Years ended December 31, 2017 2016 2015 Derivatives Designated as Cash Flow Hedging Instruments: Interest rate risk management contracts: Interest rate swaps $358 ($224 ) $288 Interest rate caps (64 ) (33 ) (44 ) Interest rate floors (346 ) — — Total ($52 ) ($257 ) $244 (Dollars in thousands) Amount of Gain (Loss) Recognized in Income on Derivatives Years ended December 31, Statement of Income Location 2017 2016 2015 Derivatives not Designated as Hedging Instruments: Forward loan commitments: Interest rate lock commitments Mortgage banking revenues ($100 ) ($175 ) $28 Commitments to sell mortgage loans Mortgage banking revenues (328 ) 942 3 Loan related derivative contracts: Interest rate swaps with customers Loan related derivative income 2,243 (598 ) 7,569 Mirror swaps with counterparties Loan related derivative income 1,198 3,854 (4,904 ) Risk participation agreements Loan related derivative income (233 ) (13 ) (224 ) Foreign exchange contracts Loan related derivative income 6 — — Total $2,786 $4,010 $2,472

Balance Sheet Offsetting (Table

Balance Sheet Offsetting (Tables)	12 Months Ended
	Dec. 31, 2017
Balance Sheet Offsetting [Abstract]
Balance Sheet Offsetting	The following tables present the Corporation’s derivative asset and derivative liability positions and the effect of netting arrangements on the Consolidated Balance Sheets: (Dollars in thousands) Gross Derivative Positions Offsetting Derivative Positions Net Amounts Presented in Balance Sheet Cash Collateral Pledged Net Amount December 31, 2017 Derivative Assets: Interest rate risk management contracts: Interest rate caps $25 $— $25 $— $25 Interest rate floors 110 — 110 — 110 Interest rate swaps 213 — 213 — 213 Loan related derivative contracts: Interest rate swaps with customers 2,857 2,589 268 — 268 Mirror swaps with counterparties 3,801 2,649 1,152 — 1,152 Total $7,006 $5,238 $1,768 $— $1,768 Derivative Liabilities: Interest rate risk management contracts: Interest rate swaps $14 $— $14 $14 $— Loan related derivative contracts: Interest rate swaps with customers 3,884 2,589 1,295 1,025 270 Mirror swaps with counterparties 2,917 2,649 268 — 268 Foreign exchange contracts 26 — 26 — 26 Total $6,841 $5,238 $1,603 $1,039 $564 (Dollars in thousands) Gross Derivative Positions Offsetting Derivative Positions Net Amounts Presented in Balance Sheet Cash Collateral Pledged Net Amount December 31, 2016 Derivative Assets: Interest rate risk management contracts: Interest rate caps $134 $— $134 $— $134 Loan related derivative contracts: Interest rate swaps with customers 4,920 2,884 2,036 — 2,036 Mirror swaps with counterparties 2,758 2,758 — — — Total $7,812 $5,642 $2,170 $— $2,170 Derivative Liabilities: Loan related derivative contracts: Interest rate swaps with customers $2,884 $2,884 $— $— $— Mirror swaps with counterparties 4,986 2,758 2,228 1,295 933 Total $8,248 $5,642 $2,606 $1,428 $1,178

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value Mortgage Loans Held For Sale, Interest Rate Lock Commitments and Commitments to Sell	The following table presents the changes in fair value related to mortgage loans held for sale, interest rate lock commitments and commitments to sell residential real estate mortgage loans, for which the fair value option was elected. Changes in fair values are reported as a component of mortgage banking revenues in the Consolidated Statements of Income. (Dollars in thousands) Years ended December 31, 2017 2016 2015 Mortgage loans held for sale $503 ($691 ) ($48 ) Interest rate lock commitments (100 ) (175 ) 28 Commitments to sell (328 ) 942 3 Total changes in fair value $75 $76 ($17 )
Assets and Liabilities Measured at Fair Value on a Recurring Basis	The following tables present the balances of assets and liabilities reported at fair value on a recurring basis: (Dollars in thousands) Total Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs Significant Unobservable Inputs (Level 3) December 31, 2017 Assets: Securities available for sale: Obligations of U.S. government-sponsored enterprises $157,604 $— $157,604 $— Mortgage-backed securities issued by U.S. government agencies and U.S. government-sponsored enterprises 590,882 — 590,882 — Obligations of states and political subdivisions 2,359 — 2,359 — Individual name issuer trust preferred debt securities 16,984 — 16,984 — Corporate bonds 13,125 — 13,125 — Mortgage loans held for sale 26,943 — 26,943 — Derivative assets 2,759 — 2,759 — Total assets at fair value on a recurring basis $810,656 $— $810,656 $— Liabilities: Derivative liabilities $3,047 $— $3,047 $— Contingent consideration liability 1,404 — — 1,404 Total liabilities at fair value on a recurring basis $4,451 $— $3,047 $1,404 (Dollars in thousands) Total Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs Significant Unobservable Inputs (Level 3) December 31, 2016 Assets: Securities available for sale: Obligations of U.S. government-sponsored enterprises $108,440 $— $108,440 $— Mortgage-backed securities issued by U.S. government agencies and U.S. government-sponsored enterprises 588,085 — 588,085 — Obligations of states and political subdivisions 14,485 — 14,485 — Individual name issuer trust preferred debt securities 26,736 — 26,736 — Corporate bonds 2,166 — 2,166 — Mortgage loans held for sale 29,434 — 29,434 — Derivative assets 3,582 — 3,582 — Total assets at fair value on a recurring basis $772,928 $— $772,928 $— Liabilities: Derivative liabilities $4,043 $— $4,043 $— Contingent consideration liability 2,047 — — 2,047 Total liabilities at fair value on a recurring basis $6,090 $— $4,043 $2,047
Fair value of Contingent Consideration Rollforward	The following table presents the change in the contingent consideration liability, which is included in other liabilities in the Consolidated Balance Sheets. (Dollars in thousands) Years ended December 31, 2017 2016 Beginning Balance $2,047 $2,945 Change in fair value (643 ) (898 ) Payments — — Ending Balance $1,404 $2,047
Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis	The following table presents the carrying value of assets held at December 31, 2017 , which were written down to fair value during the year ended December 31, 2017 : (Dollars in thousands) Total Quoted Prices in Active Markets for Identical Assets Significant Other Observable Inputs Significant Unobservable Inputs Assets: Collateral dependent impaired loans $1,425 $— $— $1,425 Property acquired through foreclosure or repossession 131 — — 131 Total assets at fair value on a nonrecurring basis $1,556 $— $— $1,556 The allowance for loan losses on the collateral dependent impaired loans included in the table above amounted to $690 thousand at December 31, 2017 . The following table summarizes the carrying value of assets held at December 31, 2016 , which were written down to fair value during the year ended December 31, 2016 : (Dollars in thousands) Total Quoted Prices in Active Markets for Identical Assets Significant Other Observable Inputs Significant Unobservable Inputs Assets: Collateral dependent impaired loans $3,828 $— $— $3,828 Property acquired through foreclosure or repossession 605 — — 605 Total assets at fair value on a nonrecurring basis $4,433 $— $— $4,433 The allowance for loan losses on the collateral dependent impaired loans included in the table above amounted to $469 thousand at December 31, 2016 .
Qualitative Information About Level 3 Assets Measured at Fair Value on a Nonrecurring Basis	The following tables present valuation techniques and unobservable inputs for assets measured at fair value on a nonrecurring basis for which the Corporation has utilized Level 3 inputs to determine fair value: (Dollars in thousands) Fair Value Valuation Technique Unobservable Input Range of Inputs Utilized (Weighted Average) December 31, 2017 Collateral dependent impaired loans $1,425 Appraisals of collateral Discount for costs to sell 0% - 15% (15%) Property acquired through foreclosure or repossession 131 Appraisals of collateral Discount for costs to sell 10% Appraisal adjustments (1) 12% - 17% (15%) (1) Management adjusts appraisal values to reflect market value declines or other discounts resulting from its knowledge of the property. (Dollars in thousands) Fair Value Valuation Technique Unobservable Input Range of Inputs Utilized (Weighted Average) December 31, 2016 Collateral dependent impaired loans $3,828 Appraisals of collateral Discount for costs to sell 10% - 20% (15%) Appraisal adjustments (1) 0% - 10% (9%) Property acquired through foreclosure or repossession 605 Appraisals of collateral Discount for costs to sell 10% - 12% (11%) Appraisal adjustments (1) 6% - 50% (24%) (1) Management adjusts appraisal values to reflect market value declines or other discounts resulting from its knowledge of the property.
Carrying Amounts, Estimated Fair Values and Fair Value Hierarchy of Financial Instruments	The following tables present the carrying amount, estimated fair value and placement in the fair value hierarchy of the Corporation’s financial instruments. The tables exclude financial instruments for which the carrying value approximates fair value such as cash and cash equivalents, FHLB stock, accrued interest receivable, bank-owned life insurance, non-maturity deposits and accrued interest payable. (Dollars in thousands) Carrying Amount Total Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs Significant Unobservable Inputs (Level 3) December 31, 2017 Financial Assets: Securities held to maturity $12,541 $12,721 $— $12,721 $— Loans, net of allowance for loan losses 3,347,583 3,369,932 — — 3,369,932 Financial Liabilities: Time deposits $1,015,095 $1,018,396 $— $1,018,396 $— FHLB advances 791,356 792,887 — 792,887 — Junior subordinated debentures 22,681 18,559 — 18,559 — (Dollars in thousands) Carrying Amount Estimated Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs Significant Unobservable Inputs (Level 3) December 31, 2016 Financial Assets: Securities held to maturity $15,633 $15,920 $— $15,920 $— Loans, net of allowance for loan losses 3,208,367 3,218,651 — — 3,218,651 Financial Liabilities: Time deposits $961,613 $962,374 $— $962,374 $— FHLB advances 848,930 852,888 — 852,888 — Junior subordinated debentures 22,681 16,970 — 16,970 —

Employee Benefits (Tables)

Employee Benefits (Tables)	12 Months Ended
	Dec. 31, 2017
Retirement Benefits [Abstract]
Schedule of Projected Benefit Obligations, Fair Value of Plan Assets and Funded (Unfunded) Status	The following table presents the plans’ projected benefit obligations, fair value of plan assets and funded (unfunded) status: (Dollars in thousands) Qualified Pension Plan Non-Qualified Retirement Plans At December 31, 2017 2016 2017 2016 Change in Benefit Obligation: Benefit obligation at beginning of period $72,951 $67,550 $13,154 $13,015 Service cost 2,149 2,148 129 122 Interest cost 2,673 2,576 428 432 Actuarial loss 7,017 3,888 2,275 374 Benefits paid (3,936 ) (3,072 ) (783 ) (789 ) Administrative expenses (131 ) (139 ) — — Benefit obligation at end of period 80,723 72,951 15,203 13,154 Change in Plan Assets: Fair value of plan assets at beginning of period 75,787 65,710 — — Actual return on plan assets 12,644 4,788 — — Employer contributions 3,000 8,500 783 789 Benefits paid (3,936 ) (3,072 ) (783 ) (789 ) Administrative expenses (131 ) (139 ) — — Fair value of plan assets at end of period 87,364 75,787 — — Funded (unfunded) status at end of period $6,641 $2,836 ($15,203 ) ($13,154 )
Schedule of Components of Accumulated Other Comprehensive Income (Loss) Related to Retirements Plans	The following table presents components of accumulated other comprehensive income related to the qualified pension plan and non-qualified retirement plans, on a pre-tax basis: (Dollars in thousands) Qualified Pension Plan Non-Qualified Retirement Plans At December 31, 2017 2016 2017 2016 Net actuarial loss $13,795 $15,593 $6,448 $4,519 Prior service credit (39 ) (62 ) (1 ) (1 ) Total pre-tax amounts recognized in accumulated other comprehensive income $13,756 $15,531 $6,447 $4,518
Schedule of Net Periodic Benefit Costs and Other Amounts Recognized in Other Comprehensive Income (Loss)	The following table presents components of net periodic benefit cost and other amounts recognized in other comprehensive income (loss), on a pre-tax basis: (Dollars in thousands) Qualified Pension Plan Non-Qualified Retirement Plans Years ended December 31, 2017 2016 2015 2017 2016 2015 Net Periodic Benefit Cost: Service cost $2,149 $2,148 $2,459 $129 $122 $78 Interest cost 2,673 2,576 2,928 428 432 490 Expected return on plan assets (4,942 ) (4,633 ) (4,515 ) — — — Amortization of prior service credit (23 ) (23 ) (23 ) (1 ) (1 ) (1 ) Recognized net actuarial loss 1,114 828 1,249 347 247 245 Net periodic benefit cost 971 896 2,098 903 800 812 Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (on a pre-tax basis): Net (gain) loss (1,798 ) 2,904 (2,816 ) 1,928 127 (156 ) Prior service cost 23 23 23 1 1 1 Recognized in other comprehensive (loss) income (1,775 ) 2,927 (2,793 ) 1,929 128 (155 ) Total recognized in net periodic benefit cost and other comprehensive (loss) income ($804 ) $3,823 ($695 ) $2,832 $928 $657
Schedule of Assumptions Used for Net Periodic Benefit Cost	The following table presents the measurement date and weighted-average assumptions used to determine benefit obligations at December 31, 2017 and 2016 : Qualified Pension Plan Non-Qualified Retirement Plans 2017 2016 2017 2016 Measurement date Dec 31, 2017 Dec 31, 2016 Dec 31, 2017 Dec 31, 2016 Discount rate 3.69% 4.18% 3.60% 4.00% Rate of compensation increase 3.75 3.75 3.75 3.75 The following table presents the measurement date and weighted-average assumptions used to determine net periodic benefit cost for the years ended December 31, 2017 , 2016 and 2015 : Qualified Pension Plan Non-Qualified Retirement Plans 2017 2016 2015 2017 2016 2015 Measurement date Dec 31, 2016 Dec 31, 2015 Dec 31, 2014 Dec 31, 2016 Dec 31, 2015 Dec 31, 2014 Discount rate N/A N/A 4.125% N/A N/A 3.90% Equivalent single discount rate for benefit obligations 4.18% 4.48 N/A 4.00% 4.20 N/A Equivalent single discount rate for service cost 4.29 4.63 N/A 4.25 4.59 N/A Equivalent single discount rate for interest cost 3.73 3.88 N/A 3.40 3.44 N/A Expected long-term return on plan assets 6.75 6.75 7.25 N/A N/A N/A Rate of compensation increase 3.75 3.75 3.75 3.75 3.75 3.75
Schedule of Fair Value and Allocation of Plan Assets	The following table present the asset allocations of the qualified pension plan, by asset category: December 31, 2017 2016 Asset Category: Equity securities 65.7 % 63.8 % Fixed income securities 30.0 32.4 Cash and cash equivalents 4.3 3.8 Total 100.0 % 100.0 % The following tables present the fair values of the qualified pension plan’s assets: (Dollars in thousands) Fair Value Measurements Using Assets at Fair Value December 31, 2017 Level 1 Level 2 Level 3 Assets: Cash and cash equivalents $3,760 $— $— $3,760 Obligations of U.S. government-sponsored enterprises — 5,926 — 5,926 Obligations of states and political subdivisions — 2,971 — 2,971 Corporate bonds — 13,112 — 13,112 Common stocks 38,508 — — 38,508 Mutual funds 23,087 — — 23,087 Total plan assets $65,355 $22,009 $— $87,364 (Dollars in thousands) Fair Value Measurements Using Assets at Fair Value December 31, 2016 Level 1 Level 2 Level 3 Assets: Cash and cash equivalents $2,880 $— $— $2,880 Obligations of U.S. government-sponsored enterprises — 4,233 — 4,233 Obligations of states and political subdivisions — 3,418 — 3,418 Corporate bonds — 13,775 — 13,775 Common stocks 33,893 — — 33,893 Mutual funds 17,588 — — 17,588 Total plan assets $54,361 $21,426 $— $75,787
Schedule of Expected Future Benefit Payments	The following table presents the benefit payments, which reflect expected future service, as appropriate, expected to be paid: (Dollars in thousands) Qualified Pension Plan Non-Qualified Retirement Plans 2018 $3,964 $897 2019 2,931 891 2020 3,387 879 2021 3,784 868 2022 4,378 891 Years 2023 - 2027 28,050 4,221

Share-Based Compensation Arra45

Share-Based Compensation Arrangements (Tables)	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Compensation Cost for Share-based Compensation Arrangements	The following table presents share-based compensation expense and the related income tax benefit recognized in the Consolidated Statements of Income for stock options, nonvested share awards and nonvested performance shares: (Dollars in thousands) Years ended December 31, 2017 2016 2015 Share-based compensation expense $2,577 $2,190 $2,074 Related income tax benefit $606 $810 $767
Stock Options Fair Value Assumptions	The following presents the assumptions used in determining the grant date fair value of the stock option awards granted to certain key employees: 2017 2016 2015 Options granted 47,725 53,400 48,600 Cliff vesting period (years) 3 3 3-5 Expected term (years) 7.0 7.5 7.5 Expected dividend yield 3.57 % 3.89 % 3.94 % Weighted average expected volatility 27.10 % 29.99 % 40.76 % Weighted average risk-free interest rate 1.70 % 1.66 % 1.95 % Weighted average grant-date fair value $10.60 $7.92 $11.15
Stock Options Activity	The following table presents a summary of the status of Washington Trust’s stock options outstanding as of and for the year ended December 31, 2017 : Number of Stock Options Weighted Average Exercise Price Weighted Average Remaining Contractual Term (Years) Aggregate Intrinsic Value (000’s) Beginning of period 219,279 $32.70 Granted 47,725 58.05 Exercised (39,076 ) 28.30 Forfeited or expired (4,075 ) 43.06 End of period 223,853 $38.68 7.22 $3,487 At end of period: Options exercisable 80,003 $25.89 4.38 $2,189 Options expected to vest in future periods 143,850 $45.80 8.80 $1,298
Schedule of Stock Options Outstanding and Options Exercisable	The following table presents additional information concerning options outstanding and options exercisable at December 31, 2017 : Options Outstanding Options Exercisable Exercise Price Ranges Number of Shares Weighted Average Remaining Life (Years) Weighted Average Exercise Price Number of Shares Weighted Average Exercise Price $15.01 to $20.00 11,700 1.87 $17.52 11,700 $17.52 $20.01 to $25.00 38,593 3.88 23.14 38,593 23.14 $25.01 to $30.00 — — — — — $30.01 to $35.00 29,710 6.00 32.76 29,710 32.76 $35.01 to $40.00 46,000 7.76 39.39 — — $40.01 to $45.00 50,800 8.80 40.25 — — $45.01 to $50.00 — — — — — $50.01 to $55.00 — — — — — $55.01 to $60.00 47,050 9.80 58.05 — — 223,853 7.22 $38.68 80,003 $25.89
Nonvested Shares Activity	The following table presents a summary of the status of Washington Trust’s nonvested share units as of and for the year ended December 31, 2017 : Number of Shares Weighted Average Grant Date Fair Value Beginning of period 49,675 $37.12 Granted 15,900 54.46 Vested (11,325 ) 32.79 Forfeited (475 ) 40.25 End of period 53,775 $43.13
Nonvested Performance Shares Outstanding	The following table presents a summary of the performance share awards as of December 31, 2017 : Grant Date Fair Value per Share Current Performance Assumption Expected Number of Shares Performance shares awarded in: 2017 $51.85 140% 36,470 2016 36.11 133% 45,220 2015 38.02 135% 35,775 Total 117,465
Nonvested Performance Shares Activity	The following table presents a summary of the status of Washington Trust’s performance share units as of and for the year ended December 31, 2017 : Number of Shares Weighted Average Grant Date Fair Value Beginning of period 101,998 $36.58 Granted 36,470 51.85 Vested (16,707 ) 34.66 Forfeited (4,296 ) 36.93 End of period 117,465 $41.58

Business Segments (Tables)

Business Segments (Tables)	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Statement of Operations and Total Assets by Reportable Segment	The following tables present the statement of operations and total assets for Washington Trust’s reportable segments: (Dollars in thousands) Year ended December 31, 2017 Commercial Banking Wealth Management Services Corporate Consolidated Total Net interest income (expense) $98,736 ($167 ) $20,962 $119,531 Provision for loan losses 2,600 — — 2,600 Net interest income (expense) after provision for loan losses 96,136 (167 ) 20,962 116,931 Noninterest income 23,244 39,346 2,219 64,809 Noninterest expenses: Depreciation and amortization expense 2,604 1,689 196 4,489 Other noninterest expenses 60,828 26,718 12,065 99,611 Total noninterest expenses 63,432 28,407 12,261 104,100 Income before income taxes 55,948 10,772 10,920 77,640 Income tax expense 23,876 3,795 4,044 31,715 Net income $32,072 $6,977 $6,876 $45,925 Total assets at period end $3,491,845 $66,083 $971,922 $4,529,850 Expenditures for long-lived assets 2,224 360 195 2,779 (Dollars in thousands) Year ended December 31, 2016 Commercial Banking Wealth Management Services Corporate Consolidated Total Net interest income (expense) $91,221 ($66 ) $19,323 $110,478 Provision for loan losses 5,650 — — 5,650 Net interest income (expense) after provision for loan losses 85,571 (66 ) 19,323 104,828 Noninterest income 24,783 37,569 2,777 65,129 Noninterest expenses: Depreciation and amortization expense 2,771 1,940 224 4,935 Other noninterest expenses 58,452 25,239 12,477 96,168 Total noninterest expenses 61,223 27,179 12,701 101,103 Income before income taxes 49,131 10,324 9,399 68,854 Income tax expense 16,790 3,692 1,891 22,373 Net income $32,341 $6,632 $7,508 $46,481 Total assets at period end $3,354,633 $64,625 $961,857 $4,381,115 Expenditures for long-lived assets 2,267 464 381 3,112 (Dollars in thousands) Year ended December 31, 2015 Commercial Banking Wealth Management Services Corporate Consolidated Total Net interest income $84,757 ($47 ) $19,272 $103,982 Provision for loan losses 1,050 — — 1,050 Net interest income (expense) after provision for loan losses 83,707 (47 ) 19,272 102,932 Noninterest income 20,618 35,416 2,306 58,340 Noninterest expenses: Depreciation and amortization expense 2,584 1,488 213 4,285 Other noninterest expenses 55,203 25,632 11,809 92,644 Total noninterest expenses 57,787 27,120 12,022 96,929 Income before income taxes 46,538 8,249 9,556 64,343 Income tax expense 15,330 3,475 2,073 20,878 Net income $31,208 $4,774 $7,483 $43,465 Total assets at period end $3,152,231 $63,801 $555,572 $3,771,604 Expenditures for long-lived assets 4,714 411 354 5,479

Other Comprehensive Income (L47

Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Activity in Other Comprehensive Income (Loss)	The following tables present the activity in other comprehensive income (loss): (Dollars in thousands) Year ended December 31, 2017 Pre-tax Amounts Income Taxes Net of Tax Securities available for sale: Changes in fair value of securities available for sale $986 $365 $621 Net (gains) losses on securities classified into noninterest income — — — Net change in fair value of securities available for sale $986 $365 $621 Cash flow hedges: Changes in fair value of cash flow hedges (774 ) (223 ) (551 ) Net cash flow hedge losses reclassified into earnings (1) 792 293 499 Net change in the fair value of cash flow hedges 18 70 (52 ) Defined benefit plan obligations: Defined benefit plan obligation adjustment (1,591 ) (594 ) (997 ) Amortization of net actuarial losses (2) 1,461 546 915 Amortization of net prior service credits (2) (24 ) (9 ) (15 ) Net change in defined benefit plan obligations (154 ) (57 ) (97 ) Total other comprehensive income $850 $378 $472 (1) The pre-tax amounts are included in interest expense on Federal Home Loan Bank advances, interest expense on junior subordinated debentures and interest income and fees on loans in the Consolidated Statements of Income. (2) The pre-tax amounts are included in salaries and employee benefits expense in the Consolidated Statements of Income. (Dollars in thousands) Year ended December 31, 2016 Pre-tax Amounts Income Taxes Net of Tax Securities available for sale: Changes in fair value of securities available for sale ($12,502 ) ($4,626 ) ($7,876 ) Net (gains) losses on securities classified into noninterest income — — — Net change in fair value of securities available for sale ($12,502 ) ($4,626 ) ($7,876 ) Cash flow hedges: Changes in fair value of cash flow hedges (403 ) (146 ) (257 ) Net cash flow hedge losses reclassified into earnings — — — Net change in the fair value of cash flow hedges (403 ) (146 ) (257 ) Defined benefit plan obligations: Defined benefit plan obligation adjustment (4,106 ) (1,518 ) (2,588 ) Amortization of net actuarial losses (1) 1,075 397 678 Amortization of net prior service credits (1) (24 ) (9 ) (15 ) Net change in defined benefit plan obligations (3,055 ) (1,130 ) (1,925 ) Total other comprehensive loss ($15,960 ) ($5,902 ) ($10,058 ) (1) The pre-tax amount is included in salaries and employee benefits expense in the Consolidated Statements of Income. (Dollars in thousands) Year ended December 31, 2015 Pre-tax Amounts Income Taxes Net of Tax Securities available for sale: Changes in fair value of securities available for sale ($4,926 ) ($1,755 ) ($3,171 ) Net (gains) losses on securities classified into noninterest income — — — Net change in fair value of securities available for sale (4,926 ) (1,755 ) (3,171 ) Cash flow hedges: Changes in fair value of cash flow hedges (102 ) (49 ) (53 ) Net cash flow hedge losses reclassified into earnings (1) 469 172 297 Net change in the fair value of cash flow hedges 367 123 244 Defined benefit plan obligations: Defined benefit plan obligation adjustment 1,478 376 1,102 Amortization of net actuarial losses (2) 1,494 542 952 Amortization of net prior service credits (2) (24 ) (7 ) (17 ) Net change in defined benefit plan obligations 2,948 911 2,037 Total other comprehensive loss ($1,611 ) ($721 ) ($890 ) (1) The pre-tax amount is included in interest expense on junior subordinated debentures in the Consolidated Statements of Income. (2) The pre-tax amount is included in salaries and employee benefits expense in the Consolidated Statements of Income.
Changes in Components of Accumulated Other Comprehensive Income (Loss)	The following tables present the changes in accumulated other comprehensive income (loss) by component, net of tax: (Dollars in thousands) Net Unrealized (Losses) Gains on Available For Sale Securities Net Unrealized Losses on Cash Flow Hedges Pension Benefit Adjustment Total Balance at December 31, 2016 ($6,825 ) ($300 ) ($12,632 ) ($19,757 ) Other comprehensive income (loss) before reclassifications 621 (551 ) (741 ) (671 ) Amounts reclassified from accumulated other comprehensive income — 499 644 1,143 Net other comprehensive income (loss) 621 (52 ) (97 ) 472 Reclassification of income tax effects due to the adoption of ASU 2018-02 (1,330 ) (76 ) (2,819 ) (4,225 ) Balance at December 31, 2017 ($7,534 ) ($428 ) ($15,548 ) ($23,510 ) (Dollars in thousands) Net Unrealized Gains (Losses) on Available For Sale Securities Net Unrealized Losses on Cash Flow Hedges Pension Benefit Adjustment Total Balance at December 31, 2015 $1,051 ($43 ) ($10,707 ) ($9,699 ) Other comprehensive loss before reclassifications (7,876 ) (257 ) (2,588 ) (10,721 ) Amounts reclassified from accumulated other comprehensive income — — 663 663 Net other comprehensive loss (7,876 ) (257 ) (1,925 ) (10,058 ) Balance at December 31, 2016 ($6,825 ) ($300 ) ($12,632 ) ($19,757 ) (Dollars in thousands) Net Unrealized Gains (Losses) on Available For Sale Securities Net Unrealized Losses on Cash Flow Hedges Pension Benefit Adjustment Total Balance at December 31, 2014 $4,222 ($287 ) ($12,744 ) ($8,809 ) Other comprehensive (loss) income before reclassifications (3,171 ) (53 ) 1,102 (2,122 ) Amounts reclassified from accumulated other comprehensive income — 297 935 1,232 Net other comprehensive (loss) income (3,171 ) 244 2,037 (890 ) Balance at December 31, 2015 $1,051 ($43 ) ($10,707 ) ($9,699 )

Earnings Per Common Share (Tabl

Earnings Per Common Share (Tables)	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Calculation of Earnings Per Common Share	The following table presents the calculation of earnings per common share: (Dollars and shares in thousands, except per share amounts) Years ended December 31, 2017 2016 2015 Earnings per common share - basic: Net income $45,925 $46,481 $43,465 Less dividends and undistributed earnings allocated to participating securities (108 ) (97 ) (126 ) Net income applicable to common shareholders 45,817 46,384 43,339 Weighted average common shares 17,207 17,081 16,879 Earnings per common share - basic $2.66 $2.72 $2.57 Earnings per common share - diluted: Net income $45,925 $46,481 $43,465 Less dividends and undistributed earnings allocated to participating securities (108 ) (97 ) (126 ) Net income applicable to common shareholders 45,817 46,384 43,339 Weighted average common shares 17,207 17,081 16,879 Dilutive effect of common stock equivalents 131 127 188 Weighted average diluted common shares 17,338 17,208 17,067 Earnings per common share - diluted $2.64 $2.70 $2.54

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Financial Instruments with Off Balance Sheet Risk	The following table presents the contractual and notional amounts of financial instruments with off-balance sheet risk: (Dollars in thousands) December 31, 2017 2016 Financial instruments whose contract amounts represent credit risk: Commitments to extend credit: Commercial loans $537,310 $430,710 Home equity lines 254,855 232,375 Other loans 48,819 49,708 Standby letters of credit 6,666 6,250 Financial instruments whose notional amounts exceed the amount of credit risk: Forward loan commitments: Interest rate lock commitments 45,139 49,502 Commitments to sell mortgage loans 71,539 78,896 Loan related derivative contracts: Interest rate swaps with customers 545,049 428,723 Mirror swaps with counterparties 545,049 428,723 Risk participation-in agreements 34,052 28,460 Foreign exchange contracts 3,005 — Interest rate risk management contracts: Interest rate swaps 60,000 60,000
Schedule of Future Minimum Annual Lease Payments	The following table presents the minimum annual lease payments under the terms of these leases, exclusive of renewal provisions: (Dollars in thousands) Years ending December 31: 2018 $3,518 2019 3,542 2020 2,863 2021 2,530 2022 2,158 2023 and thereafter 24,652 Total minimum lease payments $39,263

Parent Company Financial Stat50

Parent Company Financial Statements (Tables)	12 Months Ended
	Dec. 31, 2017
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Parent Company Only Balance Sheet	The following tables present parent company only financial statements of the Bancorp, reflecting the investment in the Bank on the equity basis of accounting. The Statements of Changes in Shareholders’ Equity for the parent company only are identical to the Consolidated Statements of Changes in Shareholders’ Equity and are therefore not presented. Balance Sheets (Dollars in thousands, except par value) December 31, 2017 2016 Assets: Cash on deposit with bank subsidiary $1,664 $1,743 Investment in subsidiaries at equity value 434,831 413,613 Dividends receivable from subsidiaries 7,770 6,518 Other assets 259 332 Total assets $444,524 $422,206 Liabilities: Junior subordinated debentures $22,681 $22,681 Dividends payable 7,087 6,628 Contingent consideration liability 1,404 2,047 Other liabilities 68 46 Total liabilities 31,240 31,402 Shareholders’ Equity: Common stock of $.0625 par value; authorized 60,000,000 shares; issued and outstanding 17,226,508 shares in 2017 and 17,170,820 shares in 2016 1,077 1,073 Paid-in capital 117,961 115,123 Retained earnings 317,756 294,365 Accumulated other comprehensive loss (23,510 ) (19,757 ) Total shareholders’ equity 413,284 390,804 Total liabilities and shareholders’ equity $444,524 $422,206
Parent Company Only Income Statement	Statements of Income (Dollars in thousands) Years ended December 31, 2017 2016 2015 Income: Dividends from subsidiaries $27,900 $24,542 $23,399 Other income 18 15 13 Total income 27,918 24,557 23,412 Expenses: Interest on junior subordinated debentures 613 491 871 Legal and professional fees 169 98 134 Acquisition related expenses — — 308 Change in fair value of contingent consideration (643 ) (898 ) 41 Other 298 282 254 Total expenses 437 (27 ) 1,608 Income before income taxes 27,481 24,584 21,804 Income tax benefit (expense) 340 (15 ) 557 Income before equity in undistributed earnings of subsidiaries 27,821 24,569 22,361 Equity in undistributed earnings of subsidiaries 18,104 21,912 21,104 Net income $45,925 $46,481 $43,465
Parent Company Only Cash Flow Statement	Statements of Cash Flows (Dollars in thousands) Years ended December 31, 2017 2016 2015 Cash flow from operating activities: Net income $45,925 $46,481 $43,465 Adjustments to reconcile net income to net cash provided by operating activities: Equity in undistributed earnings of subsidiary (18,104 ) (21,912 ) (21,104 ) (Increase) decrease in dividend receivable (1,252 ) (1,436 ) 19 Decrease (increase) in other assets 72 45 (67 ) Increase (decrease) in accrued expenses and other liabilities 22 (12 ) 2,425 Change in fair value of contingent consideration liability (643 ) (898 ) 41 Tax benefit from stock option exercises and other equity instrument issuances 508 1,016 694 Other, net (673 ) (1,051 ) (3,363 ) Net cash provided by operating activities 25,855 22,233 22,110 Cash flows from investing activities: Cash used in business combination, net of cash acquired — — (1,671 ) Net cash used in investing activities — — (1,671 ) Cash flows from financing activities: Proceeds from stock option exercises and issuance of other equity instruments 366 978 1,563 Cash dividends paid (26,300 ) (24,637 ) (22,770 ) Net cash used in financing activities (25,934 ) (23,659 ) (21,207 ) Net decrease in cash (79 ) (1,426 ) (768 ) Cash at beginning of year 1,743 3,169 3,937 Cash at end of year $1,664 $1,743 $3,169

Selected Quarterly Consolidat51

Selected Quarterly Consolidated Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Consolidated Financial Data (Unaudited)	(Dollars and shares in thousands, except per share amounts) 2017 First Quarter Second Quarter Third Quarter Fourth Quarter Interest and dividend income $35,664 $37,153 $37,869 $38,900 Interest expense 6,985 7,249 7,810 8,011 Net interest income 28,679 29,904 30,059 30,889 Provision for loan losses 400 700 1,300 200 Net interest income after provision for loan losses 28,279 29,204 28,759 30,689 Noninterest income 14,510 16,806 17,283 16,210 Noninterest expense 25,286 26,306 26,754 25,754 Income before income taxes 17,503 19,704 19,288 21,145 Income tax expense 5,721 6,505 6,326 13,163 Net income $11,782 $13,199 $12,962 $7,982 Weighted average common shares outstanding - basic 17,186 17,206 17,212 17,223 Weighted average common shares outstanding - diluted 17,293 17,316 17,318 17,349 Per share information: Basic earnings per common share $0.68 $0.77 $0.75 $0.46 Diluted earnings per common share $0.68 $0.76 $0.75 $0.46 Cash dividends declared per share $0.38 $0.38 $0.39 $0.39 (Dollars and shares in thousands, except per share amounts) 2016 First Quarter Second Quarter Third Quarter Fourth Quarter Interest and dividend income $32,969 $32,190 $33,256 $35,055 Interest expense 5,234 5,414 5,877 6,467 Net interest income 27,735 26,776 27,379 28,588 Provision for loan losses 500 450 1,800 2,900 Net interest income after provision for loan losses 27,235 26,326 25,579 25,688 Noninterest income 14,634 15,914 17,261 17,320 Noninterest expense 25,450 26,030 24,650 24,973 Income before income taxes 16,419 16,210 18,190 18,035 Income tax expense 5,484 5,153 5,863 5,873 Net income $10,935 $11,057 $12,327 $12,162 Weighted average common shares outstanding - basic 17,023 17,067 17,090 17,142 Weighted average common shares outstanding - diluted 17,157 17,194 17,203 17,245 Per share information: Basic earnings per common share $0.64 $0.65 $0.72 $0.71 Diluted earnings per common share $0.64 $0.64 $0.72 $0.70 Cash dividends declared per share $0.36 $0.36 $0.37 $0.37

Summary of Significant Accoun52

Summary of Significant Accounting Policies (Details)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Line Items]
Federal Home Loan Bank Stock, redemption period, years after membership termination	5 years
Number of days overdue to be classified as nonaccrual	90 days
Troubled debt restructured loans, management determination of loans on nonaccrual status to return to accrual status, period	6 months
Time loan is reported as TDR from date of restructuring	1 year
Equity Method Investment, Number of Investments	2
Number of low-income housing complexes included in equity method investments	2
Equity Method Investee, One [Member]
Accounting Policies [Line Items]
Equity method investment, ownership percentage	99.90%
Equity Method Investee, Two [Member]
Accounting Policies [Line Items]
Equity method investment, ownership percentage	99.90%
Premises and Improvements [Member] | Minimum [Member]
Accounting Policies [Line Items]
Estimated useful life (in years)	5 years
Premises and Improvements [Member] | Maximum [Member]
Accounting Policies [Line Items]
Estimated useful life (in years)	40 years
Furniture, Fixtures and Equipment [Member] | Minimum [Member]
Accounting Policies [Line Items]
Estimated useful life (in years)	3 years
Furniture, Fixtures and Equipment [Member] | Maximum [Member]
Accounting Policies [Line Items]
Estimated useful life (in years)	20 years

Recently Issued Accounting Pr53

Recently Issued Accounting Pronouncements (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)
Reclassification of income tax effects due to the adoption of ASU 2018-02	$ 0
Total minimum lease payments	39,263
Retained Earnings [Member]
Reclassification of income tax effects due to the adoption of ASU 2018-02	$ 4,225

Cash and Due from Banks (Narrat

Cash and Due from Banks (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Cash and Cash Equivalents [Abstract]
Average reserve deposited with the Board of Governors of the Federal Reserve Bank	$ 14.1	$ 11.5
Interest-bearing deposits in other banks	$ 31.9	$ 60.3

Securities (Narrative) (Details

Securities (Narrative) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)security	Dec. 31, 2016USD ($)security
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Securities available for sale and held to maturity pledged as collateral, fair value	$ 357,800	$ 736,200
Amortized cost of callable debt securities	195,400
Fair value of callable debt securities	$ 189,700
Number of individual name issuer trust preferred securities in a continuous unrealized loss position total | security	71	57
Unrealized losses of securities in a continuous unrealized loss position total	$ 13,535	$ 15,841
Minimum [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Callable debt securities, maturity period	5 months
Callable debt securities, call feature period	1 month
Maximum [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Callable debt securities, maturity period	19 years
Callable debt securities, call feature period	4 years
Individual name issuer trust preferred debt securities [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Number of individual name issuer trust preferred securities in a continuous unrealized loss position total | security	7	10
Number of companies issuing securities in continuous unrealized loss position | security	5
Amortized cost of trust preferred securities of individual name issuers that are below investment grade	$ 6,100
Unrealized losses of trust preferred securities of individual name issuers that are below investment grade	509
Unrealized losses of securities in a continuous unrealized loss position total	$ 1,122	$ 3,115
Corporate bonds [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Number of individual name issuer trust preferred securities in a continuous unrealized loss position total | security	6	2
Unrealized losses of securities in a continuous unrealized loss position total	$ 805	$ 5

Securities (Summary of Investme

Securities (Summary of Investments) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Available for sale securities amortized cost	$ 790,801	$ 750,745
Available for sale securities unrealized gains	3,688	5,008
Available for sale securities unrealized losses	(13,535)	(15,841)
Available for sale, at fair value	780,954	739,912
Held to maturity securities amortized cost	12,541	15,633
Held to maturity securities unrealized gains	180	287
Held to Matruity securities unrealized losses	0	0
Held to maturity securities fair value	12,721	15,920
Total securities amortized cost	803,342	766,378
Total securities unrealized gains	3,868	5,295
Total securities unrealized losses	(13,535)	(15,841)
Total securities fair value	793,675	755,832
Available for sale securities amortized cost	790,801
Obligations of U.S. government-sponsored enterprises [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Available for sale securities amortized cost	161,479	111,483
Available for sale securities unrealized gains	0	7
Available for sale securities unrealized losses	(3,875)	(3,050)
Available for sale, at fair value	157,604	108,440
Mortgage-backed securities issued by U.S. government-sponsored agencies and U.S. government-sponsored enterprises [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Available for sale securities amortized cost	594,944	592,833
Available for sale securities unrealized gains	3,671	4,923
Available for sale securities unrealized losses	(7,733)	(9,671)
Available for sale, at fair value	590,882	588,085
Held to maturity securities amortized cost	12,541	15,633
Held to maturity securities unrealized gains	180	287
Held to Matruity securities unrealized losses	0	0
Held to maturity securities fair value	12,721	15,920
Obligations of states and political subdivisions [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Available for sale securities amortized cost	2,355	14,423
Available for sale securities unrealized gains	4	62
Available for sale securities unrealized losses	0	0
Available for sale, at fair value	2,359	14,485
Individual name issuer trust preferred debt securities [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Available for sale securities amortized cost	18,106	29,851
Available for sale securities unrealized gains	0	0
Available for sale securities unrealized losses	(1,122)	(3,115)
Available for sale, at fair value	16,984	26,736
Corporate bonds [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Available for sale securities amortized cost	13,917	2,155
Available for sale securities unrealized gains	13	16
Available for sale securities unrealized losses	(805)	(5)
Available for sale, at fair value	$ 13,125	$ 2,166

Securities (Securities by Contr

Securities (Securities by Contractual Maturity) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Available for sale debt securities maturities wIthin 1 year amortized cost	$ 62,120
Available for sale debt securities maturities 1-5 years amortized cost	247,054
Available for sale debt securities maturities 5-10 years amortized cost	285,543
Available for sale debt securities maturities after 10 years amortized cost	196,084
Available for sale securities amortized cost	790,801
Available for sale debt securities maturities within 1 year fair value	61,700
Available for sale debt securities maturities 1-5 years fair value	244,392
Available for sale debt securities maturities 5-10 years fair value	280,870
Available for sale debt securities maturities after 10 years fair value	193,992
Available for sale debt securities fair value	780,954
Held to maturity debt securities maturities within 1 year amortized cost	1,719
Held to maturity debt securities maturities 1-5 years amortized cost	5,374
Held to maturity debt securities maturities 5-10 years amortized cost	4,019
Held to maturity debt securities maturities after 10 years amortized cost	1,429
Held to maturity securities amortized cost	12,541	$ 15,633
Held to maturity debt securities maturities within 1 year fair value	1,743
Held to maturity debt securities maturities 1-5 years fair value	5,451
Held to maturity debt securities maturities 5-10 years fair value	4,077
Held to maturity debt securities maturities after 10 years fair value	1,450
Held to maturity securities fair value	12,721	15,920
Mortgage-backed securities issued by U.S. government-sponsored agencies and U.S. government-sponsored enterprises [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Held to maturity securities amortized cost	12,541	15,633
Held to maturity securities fair value	$ 12,721	$ 15,920

Securities (Securities in a Con

Securities (Securities in a Continuous Unrealized Loss Position) (Details) $ in Thousands	Dec. 31, 2017USD ($)security	Dec. 31, 2016USD ($)security
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Number of securities in a continuous unrealized loss position for less than 12 months | security	31	47
Fair value of securities in a continuous unrealized loss position for less than 12 months	$ 199,567	$ 505,906
Unrealized losses of securities in a continuous unrealized loss position for less than 12 months	$ (1,416)	$ (12,726)
Number of securities in a continuous unrealized loss position for 12 months or longer | security	40	10
Fair value of securities in a continuous unrealized loss position for 12 months or longer	$ 395,580	$ 26,736
Unrealized losses of securities in a continuous unrealized loss position for 12 months or longer	$ (12,119)	$ (3,115)
Number of individual name issuer trust preferred securities in a continuous unrealized loss position total | security	71	57
Fair value of securities in a continuous unrealized loss position total	$ 595,147	$ 532,642
Unrealized losses of securities in a continuous unrealized loss position total	$ (13,535)	$ (15,841)
Obligations of U.S. government-sponsored enterprises [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Number of securities in a continuous unrealized loss position for less than 12 months | security	8	10
Fair value of securities in a continuous unrealized loss position for less than 12 months	$ 69,681	$ 98,433
Unrealized losses of securities in a continuous unrealized loss position for less than 12 months	$ (798)	$ (3,050)
Number of securities in a continuous unrealized loss position for 12 months or longer | security	8	0
Fair value of securities in a continuous unrealized loss position for 12 months or longer	$ 87,923	$ 0
Unrealized losses of securities in a continuous unrealized loss position for 12 months or longer	$ (3,077)	$ 0
Number of individual name issuer trust preferred securities in a continuous unrealized loss position total | security	16	10
Fair value of securities in a continuous unrealized loss position total	$ 157,604	$ 98,433
Unrealized losses of securities in a continuous unrealized loss position total	$ (3,875)	$ (3,050)
Mortgage-backed securities issued by U.S. government-sponsored agencies and U.S. government-sponsored enterprises [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Number of securities in a continuous unrealized loss position for less than 12 months | security	20	35
Fair value of securities in a continuous unrealized loss position for less than 12 months	$ 128,965	$ 407,073
Unrealized losses of securities in a continuous unrealized loss position for less than 12 months	$ (613)	$ (9,671)
Number of securities in a continuous unrealized loss position for 12 months or longer | security	22	0
Fair value of securities in a continuous unrealized loss position for 12 months or longer	$ 279,693	$ 0
Unrealized losses of securities in a continuous unrealized loss position for 12 months or longer	$ (7,120)	$ 0
Number of individual name issuer trust preferred securities in a continuous unrealized loss position total | security	42	35
Fair value of securities in a continuous unrealized loss position total	$ 408,658	$ 407,073
Unrealized losses of securities in a continuous unrealized loss position total	$ (7,733)	$ (9,671)
Individual name issuer trust preferred debt securities [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Number of securities in a continuous unrealized loss position for less than 12 months | security	0	0
Fair value of securities in a continuous unrealized loss position for less than 12 months	$ 0	$ 0
Unrealized losses of securities in a continuous unrealized loss position for less than 12 months	$ 0	$ 0
Number of securities in a continuous unrealized loss position for 12 months or longer | security	7	10
Fair value of securities in a continuous unrealized loss position for 12 months or longer	$ 16,984	$ 26,736
Unrealized losses of securities in a continuous unrealized loss position for 12 months or longer	$ (1,122)	$ (3,115)
Number of individual name issuer trust preferred securities in a continuous unrealized loss position total | security	7	10
Fair value of securities in a continuous unrealized loss position total	$ 16,984	$ 26,736
Unrealized losses of securities in a continuous unrealized loss position total	$ (1,122)	$ (3,115)
Corporate bonds [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Number of securities in a continuous unrealized loss position for less than 12 months | security	3	2
Fair value of securities in a continuous unrealized loss position for less than 12 months	$ 921	$ 400
Unrealized losses of securities in a continuous unrealized loss position for less than 12 months	$ (5)	$ (5)
Number of securities in a continuous unrealized loss position for 12 months or longer | security	3	0
Fair value of securities in a continuous unrealized loss position for 12 months or longer	$ 10,980	$ 0
Unrealized losses of securities in a continuous unrealized loss position for 12 months or longer	$ (800)	$ 0
Number of individual name issuer trust preferred securities in a continuous unrealized loss position total | security	6	2
Fair value of securities in a continuous unrealized loss position total	$ 11,901	$ 400
Unrealized losses of securities in a continuous unrealized loss position total	$ (805)	$ (5)

Loans (Narrative) (Details)

Loans (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Receivables [Abstract]
Net unamortized loan origination costs	$ 3,800	$ 3,000
Net unamortized premiums on purchased loans	878	783
Loans pledged as collateral	1,600,000	1,400,000
Residential loans in process of foreclosure	4,400	5,700
Interest lost on nonaccrual loans	1,300	1,600	$ 1,500
Interest income recognized for nonaccrual loans	335	640	$ 522
Nonaccrual loans	$ 11,800	$ 18,600

Loans (Narrative - Troubled Deb

Loans (Narrative - Troubled Debt Restructurings) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Receivables [Abstract]
Recorded investment	$ 11,200	$ 22,300
Specific reserves on troubled debt restructurings	$ 1,100	$ 567

Loans (Narrative - Credit Quali

Loans (Narrative - Credit Quality Indicators) (Details) - rating	Dec. 31, 2017	Dec. 31, 2016
Receivables [Abstract]
Weighted Average Risk Rating, Commercial Loans	4.70	4.68

Loans (Summary of Loans) (Detai

Loans (Summary of Loans) (Details) - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	[1]	$ 3,374,071	$ 3,234,371
Percent of total loans	[1]	100.00%	100.00%
Commercial Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans		$ 1,072,487	$ 1,074,186
Commercial Construction & Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans		138,008	121,371
Commercial & Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans		612,334	576,109
Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans		1,206,458	1,094,824
Homeowner Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans		20,790	27,924
Home Equity Lines [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans		258,114	264,200
Home Equity Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans		34,353	37,272
Other Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans		31,527	38,485
Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans		$ 1,822,829	$ 1,771,666
Percent of total loans		54.00%	55.00%
Commercial [Member] | Commercial Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	[2]	$ 1,072,487	$ 1,074,186
Percent of total loans	[2]	32.00%	33.00%
Commercial [Member] | Commercial Construction & Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	[3]	$ 138,008	$ 121,371
Percent of total loans	[3]	4.00%	4.00%
Commercial [Member] | Commercial & Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	[4]	$ 612,334	$ 576,109
Percent of total loans	[4]	18.00%	18.00%
Residential Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans		$ 1,227,248	$ 1,122,748
Percent of total loans		36.00%	35.00%
Residential Real Estate [Member] | Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans		$ 1,206,458	$ 1,094,824
Percent of total loans		35.00%	34.00%
Residential Real Estate [Member] | Homeowner Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans		$ 20,790	$ 27,924
Percent of total loans		1.00%	1.00%
Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans		$ 323,994	$ 339,957
Percent of total loans		10.00%	10.00%
Consumer [Member] | Home Equity Lines [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans		$ 258,114	$ 264,200
Percent of total loans		8.00%	8.00%
Consumer [Member] | Home Equity Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans		$ 34,353	$ 37,272
Percent of total loans		1.00%	1.00%
Consumer [Member] | Other Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	[5]	$ 31,527	$ 38,485
Percent of total loans	[5]	1.00%	1.00%
[1]	Includes net unamortized loan origination costs of $3.8 million and $3.0 million, respectively, and net unamortized premiums on purchased loans of $878 thousand and $783 thousand, respectively, at December 31, 2017 and 2016.
[2]	Loans primarily secured by income producing property.
[3]	Loans for construction of commercial properties, loans to developers for construction of residential properties and loans for land development.
[4]	Loans to businesses and individuals, a substantial portion of which are fully or partially collateralized by real estate.
[5]	Loans to individuals secured by general aviation aircraft and other personal installment loans.

Loans (Nonaccrual Loans) (Detai

Loans (Nonaccrual Loans) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual loans	$ 15,211	$ 22,058
Accruing loans 90 days or more past due	0	0
Current Payment Status [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual loans current on payment	3,400	3,500
Commercial Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual loans	4,954	7,811
Commercial Construction & Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual loans	0	0
Commercial & Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual loans	283	1,337
Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual loans	9,414	11,736
Homeowner Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual loans	0	0
Home Equity Lines [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual loans	81	0
Home Equity Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual loans	463	1,058
Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual loans	$ 16	$ 116

Loans (Past Due Loans) (Details

Loans (Past Due Loans) (Details) - USD ($)		Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due loans		$ 20,075,000	$ 24,422,000
Current loans		3,353,996,000	3,209,949,000
Total loans	[1]	3,374,071,000	3,234,371,000
Commercial Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due loans		4,960,000	8,708,000
Current loans		1,067,527,000	1,065,478,000
Total loans		1,072,487,000	1,074,186,000
Commercial Construction & Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due loans		0	0
Current loans		138,008,000	121,371,000
Total loans		138,008,000	121,371,000
Commercial & Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due loans		4,076,000	1,154,000
Current loans		608,258,000	574,955,000
Total loans		612,334,000	576,109,000
Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due loans		7,855,000	12,226,000
Current loans		1,198,603,000	1,082,598,000
Total loans		1,206,458,000	1,094,824,000
Homeowner Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due loans		0	0
Current loans		20,790,000	27,924,000
Total loans		20,790,000	27,924,000
Home Equity Lines [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due loans		1,340,000	681,000
Current loans		256,774,000	263,519,000
Total loans		258,114,000	264,200,000
Home Equity Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due loans		1,801,000	1,510,000
Current loans		32,552,000	35,762,000
Total loans		34,353,000	37,272,000
Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due loans		43,000	143,000
Current loans		31,484,000	38,342,000
Total loans		31,527,000	38,485,000
30-59
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due loans		8,304,000	8,154,000
30-59 | Commercial Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due loans		6,000	901,000
30-59 | Commercial Construction & Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due loans		0	0
30-59 | Commercial & Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due loans		3,793,000	409,000
30-59 | Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due loans		1,678,000	5,381,000
30-59 | Homeowner Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due loans		0	0
30-59 | Home Equity Lines [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due loans		1,340,000	655,000
30-59 | Home Equity Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due loans		1,458,000	776,000
30-59 | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due loans		29,000	32,000
60-89
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due loans		2,351,000	755,000
60-89 | Commercial Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due loans		0	0
60-89 | Commercial Construction & Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due loans		0	0
60-89 | Commercial & Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due loans		2,000	0
60-89 | Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due loans		2,274,000	652,000
60-89 | Homeowner Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due loans		0	0
60-89 | Home Equity Lines [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due loans		0	26,000
60-89 | Home Equity Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due loans		75,000	76,000
60-89 | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due loans		0	1,000
Over 90
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due loans		9,420,000	15,513,000
Over 90 | Commercial Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due loans		4,954,000	7,807,000
Over 90 | Commercial Construction & Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due loans		0	0
Over 90 | Commercial & Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due loans		281,000	745,000
Over 90 | Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due loans		3,903,000	6,193,000
Over 90 | Homeowner Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due loans		0	0
Over 90 | Home Equity Lines [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due loans		0	0
Over 90 | Home Equity Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due loans		268,000	658,000
Over 90 | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due loans		$ 14,000	$ 110,000
[1]	Includes net unamortized loan origination costs of $3.8 million and $3.0 million, respectively, and net unamortized premiums on purchased loans of $878 thousand and $783 thousand, respectively, at December 31, 2017 and 2016.

Loans (Impaired Loans) (Details

Loans (Impaired Loans) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Impaired [Line Items]
Recorded Investment of Impaired Loans with No Related Allowance	[1]	$ 14,626	$ 26,772
Collateral dependent impaired loans	[1]	5,993	7,079
Total Recorded Investment of Impaired Loans	[1]	20,619	33,851
Unpaid Principal of Impaired Loans with No Related Allowance		14,908	31,431
Unpaid Principal of Impaired Loans with Related Allowance		10,995	8,125
Total Unpaid Principal of Impaired Loans		25,903	39,556
No Related Allowance on Impaired Loans		0	0
Related Allowance on Impaired Loans		1,129	606
Average Recorded Investment of Impaired Loans		30,269	31,323	$ 24,610
Interest Income Recognized on Impaired Loans		845	719	626
Commercial Mortgages [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment of Impaired Loans with No Related Allowance	[1]	0	4,676
Collateral dependent impaired loans	[1]	4,954	5,104
Unpaid Principal of Impaired Loans with No Related Allowance		0	9,019
Unpaid Principal of Impaired Loans with Related Allowance		9,910	6,087
No Related Allowance on Impaired Loans		0	0
Related Allowance on Impaired Loans		1,018	448
Average Recorded Investment of Impaired Loans		8,425	13,201	14,847
Interest Income Recognized on Impaired Loans		79	239	327
Commercial Construction & Development [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment of Impaired Loans with No Related Allowance	[1]	0	0
Collateral dependent impaired loans	[1]	0	0
Unpaid Principal of Impaired Loans with No Related Allowance		0	0
Unpaid Principal of Impaired Loans with Related Allowance		0	0
No Related Allowance on Impaired Loans		0	0
Related Allowance on Impaired Loans		0	0
Average Recorded Investment of Impaired Loans		0	0	0
Interest Income Recognized on Impaired Loans		0	0	0
Commercial & Industrial [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment of Impaired Loans with No Related Allowance	[1]	4,986	6,458
Collateral dependent impaired loans	[1]	191	662
Unpaid Principal of Impaired Loans with No Related Allowance		5,081	6,550
Unpaid Principal of Impaired Loans with Related Allowance		212	699
No Related Allowance on Impaired Loans		0	0
Related Allowance on Impaired Loans		1	3
Average Recorded Investment of Impaired Loans		6,445	3,540	3,415
Interest Income Recognized on Impaired Loans		281	99	130
Residential Mortgage [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment of Impaired Loans with No Related Allowance	[1]	9,069	14,385
Collateral dependent impaired loans	[1]	715	1,285
Unpaid Principal of Impaired Loans with No Related Allowance		9,256	14,569
Unpaid Principal of Impaired Loans with Related Allowance		741	1,310
No Related Allowance on Impaired Loans		0	0
Related Allowance on Impaired Loans		104	151
Average Recorded Investment of Impaired Loans		14,571	12,848	5,423
Interest Income Recognized on Impaired Loans		444	322	147
Homeowner Construction [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment of Impaired Loans with No Related Allowance	[1]	0	0
Collateral dependent impaired loans	[1]	0	0
Unpaid Principal of Impaired Loans with No Related Allowance		0	0
Unpaid Principal of Impaired Loans with Related Allowance		0	0
No Related Allowance on Impaired Loans		0	0
Related Allowance on Impaired Loans		0	0
Average Recorded Investment of Impaired Loans		0	0	0
Interest Income Recognized on Impaired Loans		0	0	0
Home Equity Lines [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment of Impaired Loans with No Related Allowance	[1]	81	0
Collateral dependent impaired loans	[1]	0	0
Unpaid Principal of Impaired Loans with No Related Allowance		81	0
Unpaid Principal of Impaired Loans with Related Allowance		0	0
No Related Allowance on Impaired Loans		0	0
Related Allowance on Impaired Loans		0	0
Average Recorded Investment of Impaired Loans		79	354	228
Interest Income Recognized on Impaired Loans		7	10	1
Home Equity Loans [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment of Impaired Loans with No Related Allowance	[1]	476	1,137
Collateral dependent impaired loans	[1]	0	0
Unpaid Principal of Impaired Loans with No Related Allowance		476	1,177
Unpaid Principal of Impaired Loans with Related Allowance		0	0
No Related Allowance on Impaired Loans		0	0
Related Allowance on Impaired Loans		0	0
Average Recorded Investment of Impaired Loans		606	1,233	487
Interest Income Recognized on Impaired Loans		24	38	11
Other Consumer [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment of Impaired Loans with No Related Allowance	[1]	14	116
Collateral dependent impaired loans	[1]	133	28
Unpaid Principal of Impaired Loans with No Related Allowance		14	116
Unpaid Principal of Impaired Loans with Related Allowance		132	29
No Related Allowance on Impaired Loans		0	0
Related Allowance on Impaired Loans		6	4
Average Recorded Investment of Impaired Loans		143	147	210
Interest Income Recognized on Impaired Loans		10	11	$ 10
Commercial [Member]
Financing Receivable, Impaired [Line Items]
Total Recorded Investment of Impaired Loans	[1]	10,131	16,900
Total Unpaid Principal of Impaired Loans		15,203	22,355
Related Allowance on Impaired Loans		1,019	451
Residential Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Total Recorded Investment of Impaired Loans	[1]	9,784	15,670
Total Unpaid Principal of Impaired Loans		9,997	15,879
Related Allowance on Impaired Loans		104	151
Consumer [Member]
Financing Receivable, Impaired [Line Items]
Total Recorded Investment of Impaired Loans	[1]	704	1,281
Total Unpaid Principal of Impaired Loans		703	1,322
Related Allowance on Impaired Loans		$ 6	$ 4
[1]	The recorded investment in impaired loans consists of unpaid principal balance, net of charge-offs, interest payments received applied to principal and unamortized deferred loan origination fees and costs. For accruing impaired loans (troubled debt restructurings for which management has concluded that the collectability of the loan is not in doubt), the recorded investment also includes accrued interest.

Loans (Troubled Debt Restructur

Loans (Troubled Debt Restructurings) (Details) $ in Thousands		12 Months Ended
		Dec. 31, 2017USD ($)loan	Dec. 31, 2016USD ($)loan
Financing Receivable, Modifications [Line Items]
Number of Loans Modified as a Troubled Debt Restructuring | loan		0	13
Pre-Modification Recorded Investment	[1]	$ 0	$ 11,391
Post-Modification Recorded Investment	[1]	$ 0	$ 11,391
Commercial Mortgages [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans Modified as a Troubled Debt Restructuring | loan		0	1
Pre-Modification Recorded Investment	[1]	$ 0	$ 776
Post-Modification Recorded Investment	[1]	$ 0	$ 776
Commercial Construction & Development [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans Modified as a Troubled Debt Restructuring | loan		0	0
Pre-Modification Recorded Investment	[1]	$ 0	$ 0
Post-Modification Recorded Investment	[1]	$ 0	$ 0
Commercial & Industrial [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans Modified as a Troubled Debt Restructuring | loan		0	9
Pre-Modification Recorded Investment	[1]	$ 0	$ 6,229
Post-Modification Recorded Investment	[1]	$ 0	$ 6,229
Residential Mortgage [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans Modified as a Troubled Debt Restructuring | loan		0	3
Pre-Modification Recorded Investment	[1]	$ 0	$ 4,386
Post-Modification Recorded Investment	[1]	$ 0	$ 4,386
Homeowner Construction [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans Modified as a Troubled Debt Restructuring | loan		0	0
Pre-Modification Recorded Investment	[1]	$ 0	$ 0
Post-Modification Recorded Investment	[1]	$ 0	$ 0
Home Equity Lines [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans Modified as a Troubled Debt Restructuring | loan		0	0
Pre-Modification Recorded Investment	[1]	$ 0	$ 0
Post-Modification Recorded Investment	[1]	$ 0	$ 0
Home Equity Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans Modified as a Troubled Debt Restructuring | loan		0	0
Pre-Modification Recorded Investment	[1]	$ 0	$ 0
Post-Modification Recorded Investment	[1]	$ 0	$ 0
Other Consumer [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans Modified as a Troubled Debt Restructuring | loan		0	0
Pre-Modification Recorded Investment	[1]	$ 0	$ 0
Post-Modification Recorded Investment	[1]	$ 0	$ 0
Payment Default [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans Modified as a Troubled Debt Restructuring | loan		0	7
[1]	The recorded investment in troubled debt restructurings consists of unpaid principal balance, net of charge-offs and unamortized deferred loan origination fees and costs, at the time of the restructuring. For accruing troubled debt restructured loans, the recorded investment also includes accrued interest.

Loans (Troubled Debt Restruct67

Loans (Troubled Debt Restructurings Type of Modification) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Modifications [Line Items]
Pre-Modification Recorded Investment	[1]	$ 0	$ 11,391
Below-market interest rate concession [Member]
Financing Receivable, Modifications [Line Items]
Pre-Modification Recorded Investment		0	0
Payment deferral [Member]
Financing Receivable, Modifications [Line Items]
Pre-Modification Recorded Investment		0	1,111
Maturity / amortization concession [Member]
Financing Receivable, Modifications [Line Items]
Pre-Modification Recorded Investment		0	683
Interest only payments [Member]
Financing Receivable, Modifications [Line Items]
Pre-Modification Recorded Investment		0	4,326
Combination [Member]
Financing Receivable, Modifications [Line Items]
Pre-Modification Recorded Investment	[2]	$ 0	$ 5,271
[1]	The recorded investment in troubled debt restructurings consists of unpaid principal balance, net of charge-offs and unamortized deferred loan origination fees and costs, at the time of the restructuring. For accruing troubled debt restructured loans, the recorded investment also includes accrued interest.
[2]	Loans included in this classification were modified with a combination of any two of the concessions listed in this table.

Loans (Troubled Debt Restruct68

Loans (Troubled Debt Restructurings Subsequent Default) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017loan	Dec. 31, 2016USD ($)loan
Financing Receivable, Modifications [Line Items]
Number of Loans Modified as a Troubled Debt Restructuring	0	13
Payment Default [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans Modified as a Troubled Debt Restructuring	0	7
Recorded Investment on Modifications with Subsequent Default | $		$ 1.6

Loans (Credit Quality Indicator

Loans (Credit Quality Indicators - Commercial) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans by credit quality indicator	$ 1,798,130	$ 1,746,145
Pass [Member] | Commercial Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans by credit quality indicator	1,067,373	1,065,358
Pass [Member] | Commercial Construction & Development [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans by credit quality indicator	138,008	121,371
Pass [Member] | Commercial & Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans by credit quality indicator	592,749	559,416
Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans by credit quality indicator	9,804	9,714
Special Mention [Member] | Commercial Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans by credit quality indicator	0	776
Special Mention [Member] | Commercial Construction & Development [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans by credit quality indicator	0	0
Special Mention [Member] | Commercial & Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans by credit quality indicator	9,804	8,938
Classified [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans by credit quality indicator	14,895	15,807
Classified [Member] | Commercial Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans by credit quality indicator	5,114	8,052
Classified [Member] | Commercial Construction & Development [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans by credit quality indicator	0	0
Classified [Member] | Commercial & Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans by credit quality indicator	$ 9,781	$ 7,755

Loans (Credit Quality Indicat70

Loans (Credit Quality Indicators - Residential, Consumer) (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment [Line Items]
Current loans	$ 3,353,996,000	$ 3,209,949,000
Past due loans	20,075,000	24,422,000
Accruing Residential Mortgage [Member]
Financing Receivable, Recorded Investment [Line Items]
Current loans	1,070,501,000	954,867,000
Past due loans	6,413,000	11,017,000
Nonaccrual Residential Mortgage [Member]
Financing Receivable, Recorded Investment [Line Items]
Current loans	128,102,000	127,731,000
Past due loans	1,442,000	1,209,000
Homeowner Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Current loans	20,790,000	27,924,000
Past due loans	0	0
Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Current loans	1,219,393,000	1,110,522,000
Past due loans	7,855,000	12,226,000
Home Equity Lines [Member]
Financing Receivable, Recorded Investment [Line Items]
Current loans	256,774,000	263,519,000
Past due loans	1,340,000	681,000
Home Equity Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Current loans	32,552,000	35,762,000
Past due loans	1,801,000	1,510,000
Other Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Current loans	31,484,000	38,342,000
Past due loans	43,000	143,000
Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Current loans	320,810,000	337,623,000
Past due loans	$ 3,184,000	$ 2,334,000

Loans (Analysis of Loan Servici

Loans (Analysis of Loan Servicing Rights) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Loan Servicing Rights [Roll Forward]
Beginning balance	$ 3,493	$ 3,348	$ 2,989
Loan servicing rights capitalized	1,104	1,412	1,406
Amortization	(984)	(1,267)	(1,047)
Decrease in impairment reserve	0	0	0
Ending balance	3,613	3,493	3,348
Valuation Allowance [Roll Forward]
Beginning balance	0	(1)	(2)
Loan servicing rights capitalized	0	0	0
Amortization	0	0	0
Decrease in impairment reserve	0	1	1
Ending balance	0	0	(1)
Total Loan Servicing Rights [Roll Forward]
Beginning Balance	3,493	3,347	2,987
Loan servicing rights capitalized	1,104	1,412	1,406
Amortization	(984)	(1,267)	(1,047)
Decrease in impairment reserve	0	1	1
Ending balance	$ 3,613	$ 3,493	$ 3,347

Loans (Estimated Aggregate Amor

Loans (Estimated Aggregate Amortization Expense) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Receivables [Abstract]
Amortization Expense, Next Twelve Months	$ 899
Amortization Expense, Year Two	675
Amortization Expense, Year Three	507
Amortization Expense, Year Four	381
Amortization Expense, Year Five	286
Amortization Expense, Thereafter	865
Total estimated amortization expense	$ 3,613	$ 3,493	$ 3,348	$ 2,989

Loans (Loans Serviced for Other

Loans (Loans Serviced for Others, by Type of Loan) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Balance of loans being serviced	$ 676,850	$ 624,083
Residential Mortgage [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Balance of loans being serviced	568,311	522,766
Commercial Loan [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Balance of loans being serviced	$ 108,539	$ 101,317

Allowance for Loan Losses (Allo

Allowance for Loan Losses (Allowance for Loan Losses Rollforward Analysis) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance		$ 26,004		$ 27,069		$ 28,023
Charge-offs		(2,462)		(7,012)		(2,305)
Recoveries		346		297		301
Provision		2,600		5,650		1,050
Ending Balance		26,488		26,004		27,069
Commercial Mortgages [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance		9,971		9,140		8,202
Charge-offs		(1,867)		(5,816)		(809)
Recoveries		82		56		92
Provision		3,460		6,591		1,655
Ending Balance		11,646		9,971		9,140
Commercial Construction & Development [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance		1,195		1,758		1,300
Charge-offs		0		0		0
Recoveries		0		0		0
Provision		(112)		(563)		458
Ending Balance		1,083		1,195		1,758
Commercial & Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance		6,992	[1]	8,202	[1],[2]	7,987	[2]
Charge-offs		(336)	[1]	(759)	[1]	(671)	[2]
Recoveries		169	[1]	156	[1]	87	[2]
Provision		(1,245)	[1]	(607)	[1]	799	[2]
Ending Balance	[1]	5,580		6,992		8,202	[2]
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance		18,158		19,100		17,489
Charge-offs		(2,203)		(6,575)		(1,480)
Recoveries		251		212		179
Provision		2,103		5,421		2,912
Ending Balance		18,309		18,158		19,100
Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance		5,252		5,460		5,430
Charge-offs		(74)		(200)		(207)
Recoveries		39		11		28
Provision		210		(19)		209
Ending Balance		5,427		5,252		5,460
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance		2,594		2,509		2,713
Charge-offs		(185)		(237)		(618)
Recoveries		56		74		94
Provision		287		248		320
Ending Balance		$ 2,752		2,594		2,509
Unallocated [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance				$ 0		2,391
Charge-offs						0
Recoveries						0
Provision						(2,391)
Ending Balance						$ 0
[1]	Commercial & industrial loans.
[2]	Commercial & industrial loans.

Allowance for Loan Losses (Al75

Allowance for Loan Losses (Allowance for Loan Losses by Segment & Impairment Methodology) (Details) - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment		$ 20,598	$ 33,815
Loans related allowance individually evaluated for impairment		1,129	606
Loans collectively evaluated for impairment		3,353,473	3,200,556
Loans related allowance collectively evaluated for impairment		25,359	25,398
Total loans	[1]	3,374,071	3,234,371
Allowance		26,488	26,004
Commercial Mortgages [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment		4,954	9,776
Loans related allowance individually evaluated for impairment		1,018	448
Loans collectively evaluated for impairment		1,067,533	1,064,410
Loans related allowance collectively evaluated for impairment		10,628	9,523
Total loans		1,072,487	1,074,186
Commercial Construction & Development [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment		0	0
Loans related allowance individually evaluated for impairment		0	0
Loans collectively evaluated for impairment		138,008	121,371
Loans related allowance collectively evaluated for impairment		1,083	1,195
Total loans		138,008	121,371
Commercial & Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment		5,157	7,098
Loans related allowance individually evaluated for impairment		1	3
Loans collectively evaluated for impairment		607,177	569,011
Loans related allowance collectively evaluated for impairment		5,579	6,989
Total loans		612,334	576,109
Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment		9,783	15,661
Loans related allowance individually evaluated for impairment		104	151
Loans collectively evaluated for impairment		1,217,465	1,107,087
Loans related allowance collectively evaluated for impairment		5,323	5,101
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment		704	1,280
Loans related allowance individually evaluated for impairment		6	4
Loans collectively evaluated for impairment		323,290	338,677
Loans related allowance collectively evaluated for impairment		$ 2,746	$ 2,590
[1]	Includes net unamortized loan origination costs of $3.8 million and $3.0 million, respectively, and net unamortized premiums on purchased loans of $878 thousand and $783 thousand, respectively, at December 31, 2017 and 2016.

Premises and Equipment (Details

Premises and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 71,053	$ 72,316
Less accumulated depreciation	42,720	43,296
Total premises and equipment, net	28,333	29,020
Depreciation expense	3,500	3,700	$ 3,400
Land and Improvements [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	6,020	6,020
Premises and Improvements [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	38,793	37,913
Furniture, Fixtures and Equipment [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 26,240	$ 28,383

Goodwill and Other Intangible77

Goodwill and Other Intangibles (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Impairment	$ 150	$ 0	$ 0
Amortization of intangibles	$ 1,035	$ 1,284	$ 904
Weston Financial acquisition [Member] | Advisory Contracts [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible asset useful life (in years)	20 years
Halsey acquisition [Member] | Advisory Contracts [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible asset useful life (in years)	15 years
Wealth Management Services [Member]
Finite-Lived Intangible Assets [Line Items]
Impairment	$ 150

Goodwill and Other Intangible78

Goodwill and Other Intangibles (Schedule of Goodwill) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill [Roll Forward]
Goodwill, Beginning Balance	$ 64,059
Impairment	(150)	$ 0	$ 0
Goodwill, Ending Balance	63,909	64,059
Commercial Banking [Member]
Goodwill [Roll Forward]
Goodwill, Beginning Balance	22,591
Impairment	0
Goodwill, Ending Balance	22,591	22,591
Wealth Management Services [Member]
Goodwill [Roll Forward]
Goodwill, Beginning Balance	41,468
Impairment	(150)
Goodwill, Ending Balance	$ 41,318	$ 41,468

Goodwill and Other Intangible79

Goodwill and Other Intangibles (Schedule of Components of Intangible Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Advisory Contracts [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 20,803	$ 20,803
Accumulated amortization	11,663	10,648
Net amount	9,140	10,155
Non-compete Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	369	369
Accumulated amortization	369	349
Net amount	$ 0	$ 20

Goodwill and Other Intangible80

Goodwill and Other Intangibles (Schedule of Amortization Annual Expense) (Details) $ in Thousands	Dec. 31, 2017USD ($)
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	$ 979
Finite-Lived Intangible Assets, Amortization Expense, Year Two	943
Finite-Lived Intangible Assets, Amortization Expense, Year Three	914
Finite-Lived Intangible Assets, Amortization Expense, Year Four	890
Finite-Lived Intangible Assets, Amortization Expense, Year Five	860
Finite-Lived Intangible Assets, Amortization Expense, after Year Five	$ 4,554

Income Tax Expense (Narrative)

Income Tax Expense (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Adjustment to net deferred tax asset for enacted changes in federal tax law	$ 6,170	$ 0	$ 0
Tax benefit from stock option exercises and other equity instruments	508	1,016	$ 694
Unrecognized tax benefits	$ 0	$ 0

Income Tax Expense (Schedule of

Income Tax Expense (Schedule of Components of Income Tax Expense) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current tax expense:
Federal									$ 23,827	$ 19,444	$ 17,864
State									2,201	2,061	1,194
Total current tax expense									26,028	21,505	19,058
Deferred tax expense (benefit):
Federal									5,717	796	2,003
State									(30)	72	(183)
Total deferred tax expense									5,687	868	1,820
Total income tax expense	$ 13,163	$ 6,326	$ 6,505	$ 5,721	$ 5,873	$ 5,863	$ 5,153	$ 5,484	$ 31,715	$ 22,373	$ 20,878

Income Tax Expense (Schedule 83

Income Tax Expense (Schedule of Income Tax Rate Reconciliation) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Effective Income Tax Rate, Continuing Operations, Tax Rate Reconciliation [Abstract]
Tax expense at Federal statutory rate									$ 27,174	$ 24,099	$ 22,520
(Decrease) increase in taxes resulting from:
Tax-exempt income									(1,313)	(1,599)	(1,604)
Dividends received deduction									(55)	(58)	(57)
BOLI									(757)	(930)	(694)
Stock based compensation									(481)	0
Federal tax credits									(364)	(364)	(364)
Change in fair value of contingent consideration									(225)	(314)	0
Acquisition related expenses									0	0	318
State income tax expense, net of federal income tax benefit									1,411	1,387	658
Adjustment to net deferred tax asset for enacted changes in federal tax law									6,170	0	0
Other									155	152	101
Total income tax expense	$ 13,163	$ 6,326	$ 6,505	$ 5,721	$ 5,873	$ 5,863	$ 5,153	$ 5,484	$ 31,715	$ 22,373	$ 20,878

Income Tax Expense (Schedule 84

Income Tax Expense (Schedule of Gross Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Allowance for loan losses	$ 6,225	$ 9,621
Defined benefit pension obligations	1,767	3,804
Deferred compensation	3,334	3,991
Deferred loan origination fees	1,325	1,999
Stock based compensation	1,240	1,519
Net unrealized losses on available for sale securities	2,314	4,008
Other	2,281	3,495
Deferred tax assets	18,486	28,437
Deferred tax liabilities:
Amortization of intangibles	(2,148)	(3,765)
Deferred loan origination costs	(3,550)	(5,156)
Loan servicing rights	(849)	(1,293)
Other	(1,200)	(1,419)
Deferred tax liabilities	(7,747)	(11,633)
Net deferred tax asset	$ 10,739	$ 16,804

Time Certificates of Deposit (N

Time Certificates of Deposit (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Time Certificates of Deposit [Abstract]
Time deposits greater than FDIC limit	$ 75.1	$ 53.4

Time Certificates of Deposit (S

Time Certificates of Deposit (Schedule of Time Certifcates of Deposit Maturities) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule Maturity Abstract]
Time Deposits Scheduled Maturity, Next Twelve Months	$ 479,914
Time Deposits Scheduled Maturity, Year Two	323,597
Time Deposits Scheduled Maturity, Year Three	90,282
Time Deposits Scheduled Maturity, Year Four	59,263
Time Deposits Scheduled Maturity, Year Five	61,991
Time Deposits Scheduled Maturity, Thereafter	48
Time deposits	$ 1,015,095	$ 961,613
Weighted Average Rate [Abstract]
Time Deposits Weighted Average Rate, Next Twelve Months	0.96%
Time Deposits Weighted Average Rate, Year Two	1.51%
Time Deposits Weighted Average Rate, Year Three	1.54%
Time Deposits Weighted Average Rate, Year Four	1.77%
Time Deposits Weighted Average Rate, Year Five	1.94%
Time Deposits Weighted Average Rate, Thereafter	1.30%
Total Time Deposits Weighted Average Rate	1.30%

Time Certificates of Deposit 87

Time Certificates of Deposit (Schedule of Time Certificates of Deposit $100 Thousand or More Maturities) (Details) $ in Thousands	Dec. 31, 2017USD ($)
Deposits [Abstract]
Time Deposits $100,000 or More Maturing in Three Months or Less	$ 100,142
Time Deposits $100,000 or More Maturing in Three Months Through Six Months	21,824
Time Deposits $100,000 or More Maturing in Six Months Through Twelve Months	35,239
Time Deposits $100,000 or More Maturing After 12 Months	172,083
Time Deposits $100,000 or More Balance at Year End	$ 329,288

Borrowings (Narrative - Federal

Borrowings (Narrative - Federal Home Loan Bank Advances) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Federal Home Loan Bank advances	$ 791,356	$ 848,930
Federal Home Loan Bank of Boston [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Federal Home Loan Bank advances	791,356	848,930
Unused line of credit with Federal Home Loan Bank	40,000	40,000
Line of Credit Facility, Remaining Borrowing Capacity	$ 449,900	$ 594,500

Borrowings (Narrative - Junior

Borrowings (Narrative - Junior Subordinated Debentures) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Aug. 29, 2005
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Junior subordinated debentures	$ 22,681	$ 22,681
Trust Preferred Securities [Member] | Trust I Capital Securities [Member] | Private Placement [Member]
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Amount of capital securities issued			$ 8,300
Description of variable rate basis	three-month LIBOR
Basis spread on variable rate	1.45%
Trust Preferred Securities [Member] | Trust I Debentures [Member]
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Junior subordinated debentures			8,300
Description of variable rate basis	three-month LIBOR
Basis spread on variable rate	1.45%
Trust Preferred Securities [Member] | Trust II Capital Securities [Member] | Private Placement [Member]
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Amount of capital securities issued			14,400
Description of variable rate basis	three-month LIBOR
Basis spread on variable rate	1.45%
Trust Preferred Securities [Member] | Trust II Debentures [Member]
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Junior subordinated debentures			$ 14,400
Description of variable rate basis	three-month LIBOR
Basis spread on variable rate	1.45%

Borrowings (Federal Home Loan B

Borrowings (Federal Home Loan Bank Advances Maturity Schedule) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Federal Home Loan Bank, Advances, Fiscal Year Maturity [Abstract]
Federal Home Loan Bank advances	$ 791,356	$ 848,930
Federal Home Loan Bank of Boston [Member]
Federal Home Loan Bank, Advances, Fiscal Year Maturity [Abstract]
Scheduled Maturity, Next 12 months	465,634
Scheduled Maturity, Year Two	137,258
Scheduled Maturity, Year Three	67,033
Scheduled Maturity, Year Four	51,222
Scheduled Maturity, Year Five	55,447
Scheduled Maturity, Thereafter	14,762
Federal Home Loan Bank advances	$ 791,356	$ 848,930
Federal Home Loan Bank, Advances, Maturities Summary, Average Interest Rate of Amounts Due [Abstract]
Weighted Average Rate, Next 12 months	1.51%
Weighted Average Rate, Year Two	1.62%
Weighted Average Rate, Year Three	1.95%
Weighted Average Rate, Year Four	2.43%
Weighted Average Rate, Year Five	3.58%
Weighted Average Rate, Thereafter	2.44%
Weighted Average Rate, Total	1.85%

Borrowings (Certain Information

Borrowings (Certain Information of Federal Home Loan Bank of Boston Advances) (Details) - Federal Home Loan Bank of Boston [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Average amount outstanding during the period	$ 351,692	$ 275,533	$ 155,874
Amount outstanding at end of period	367,500	352,500	107,500
Highest month end balance during period	$ 417,500	$ 367,500	$ 229,500
Weighted-average interest rate at end of period	1.57%	0.79%	0.55%
Weighted-average interest rate during the period	1.20%	0.73%	0.38%

Shareholders' Equity (Narrative

Shareholders' Equity (Narrative) (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Dec. 31, 2006	Dec. 31, 2007	Dec. 31, 2017
Dividends:
Amount of additional dividends the bank could have declared			$ 209.8
Reserved Shares:
Reserved shares available for grant			1,989,991
2006 Stock Repurchase Plan [Member]
Stock Repurchase Program:
Authorized amount (in shares)	400,000
Authorized amount as a percentage of total common stock	3.00%
Cumulative amount of shares purchased			185,400
Shares repurchased, value		$ 4.8

Shareholders' Equity (Regulator

Shareholders' Equity (Regulatory Captial Requirements) (Details) - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Parent Company [Member]
Total Capital (to Risk-Weighted Assets):
Total Capital		$ 416,038	$ 390,867
Total Capital to Risk-Weighted Assets		12.45%	12.26%
Total Capital for Capital Adequacy Purposes		$ 267,365	$ 255,093
Total Capital for Capital Adequacy Purposes to Risk-Weighted Assets		8.00%	8.00%
Tier 1 Capital (to Risk-Weighted Assets):
Tier 1 Capital		$ 389,289	$ 364,655
Tier 1 Capital to Risk Weighted-Assets		11.65%	11.44%
Tier 1 Capital Required For Capital Adequacy Purposes		$ 200,524	$ 191,320
Tier 1 Capital Required for Capital Adequacy Purposes to Risk Weighted-Assets		6.00%	6.00%
Common Equity Tier 1 Capital [Abstract]
Common Equity Tier 1 Capital		$ 367,291	$ 342,656
Common Equity Tier 1 Capital to Risk Weighted Assets		10.99%	10.75%
Common Equity Tier 1 Required for Capital Adequacy		$ 150,383	$ 143,490
Common Equity Tier 1 Capital for Capital Adequacy to Risk Weighted Assets		4.50%	4.50%
Tier 1 Capital (to Average Assets):
Tier 1 Leverage Capital	[1]	$ 389,289	$ 364,655
Tier 1 Leverage Capital to Average Assets	[1]	8.79%	8.67%
Tier 1 Leverage Capital Required for Capital Adequacy Purposes	[1]	$ 177,089	$ 168,271
Tier 1 Leverage Capital Required for Capital Adequacy Purposes to Average Assets	[1]	4.00%	4.00%
Bank [Member]
Total Capital (to Risk-Weighted Assets):
Total Capital		$ 413,593	$ 389,840
Total Capital to Risk-Weighted Assets		12.38%	12.23%
Total Capital for Capital Adequacy Purposes		$ 267,338	$ 255,050
Total Capital for Capital Adequacy Purposes to Risk-Weighted Assets		8.00%	8.00%
Total Capital To Be Well Capitalized		$ 334,172	$ 318,813
Total Capital To Be Well Capitalized to Risk Weighted-Assets		10.00%	10.00%
Tier 1 Capital (to Risk-Weighted Assets):
Tier 1 Capital		$ 386,844	$ 363,628
Tier 1 Capital to Risk Weighted-Assets		11.58%	11.41%
Tier 1 Capital Required For Capital Adequacy Purposes		$ 200,503	$ 191,288
Tier 1 Capital Required for Capital Adequacy Purposes to Risk Weighted-Assets		6.00%	6.00%
Tier 1 Capital Required To Be Well Capitalized		$ 267,338	$ 255,050
Tier 1 Capital Required To Be Well Capitalized to Risk Weighted-Assets		8.00%	8.00%
Common Equity Tier 1 Capital [Abstract]
Common Equity Tier 1 Capital		$ 386,844	$ 363,628
Common Equity Tier 1 Capital to Risk Weighted Assets		11.58%	11.41%
Common Equity Tier 1 Required for Capital Adequacy		$ 150,378	$ 143,466
Common Equity Tier 1 Capital for Capital Adequacy to Risk Weighted Assets		4.50%	4.50%
Common Equity Tier 1 Capital Required to be Well Capitalized		$ 217,212	$ 207,228
Common Equity Tier 1 Capital Required to be Well Capitalized to Risk Weighted Assets		6.50%	6.50%
Tier 1 Capital (to Average Assets):
Tier 1 Leverage Capital	[1]	$ 386,844	$ 363,628
Tier 1 Leverage Capital to Average Assets	[1]	8.74%	8.65%
Tier 1 Leverage Capital Required for Capital Adequacy Purposes	[1]	$ 177,048	$ 168,207
Tier 1 Leverage Capital Required for Capital Adequacy Purposes to Average Assets	[1]	4.00%	4.00%
Tier 1 Leverage Capital Required To Be Well Capitalized	[1]	$ 221,310	$ 210,259
Tier 1 Leverage Capital Required To Be Well Capitalized to Average Assets	[1]	5.00%	5.00%
[1]	Leverage ratio.

Derivative Financial Instrume94

Derivative Financial Instruments (Narrative) (Details) $ in Thousands	Dec. 31, 2017USD ($)derivative_instrument	Dec. 31, 2016USD ($)derivative_instrument
Interest rate swaps [Member]
Derivatives, Fair Value [Line Items]
Notional amount	$ 60,000	$ 60,000
Interest rate swaps with customers [Member]
Derivatives, Fair Value [Line Items]
Notional amount	545,049	428,723
Mirror swaps with counterparties [Member]
Derivatives, Fair Value [Line Items]
Notional amount	545,049	428,723
Risk participation-in agreement [Member]
Derivatives, Fair Value [Line Items]
Notional amount	34,052	28,460
Foreign exchange contract [Member]
Derivatives, Fair Value [Line Items]
Notional amount	$ 3,005	0
Designated as Hedging Instrument [Member] | Interest rate caps [Member]
Derivatives, Fair Value [Line Items]
Number of derivative instruments held | derivative_instrument	2
Notional amount	$ 22,700	$ 22,700
Interest rate cap strike	4.50%
Designated as Hedging Instrument [Member] | Interest rate swaps [Member]
Derivatives, Fair Value [Line Items]
Number of derivative instruments held | derivative_instrument	2	2
Notional amount	$ 60,000	$ 60,000
Designated as Hedging Instrument [Member] | Interest rate floors [Member]
Derivatives, Fair Value [Line Items]
Number of derivative instruments held | derivative_instrument	3
Notional amount	$ 300,000
Interest rate floor strike	1.00%
Not Designated as Hedging Instrument [Member] | Interest rate swaps with customers [Member]
Derivatives, Fair Value [Line Items]
Notional amount	$ 545,000	428,700
Not Designated as Hedging Instrument [Member] | Risk participation-out agreement [Member]
Derivatives, Fair Value [Line Items]
Notional amount	52,400	38,300
Not Designated as Hedging Instrument [Member] | Risk participation-in agreement [Member]
Derivatives, Fair Value [Line Items]
Notional amount	34,100	$ 28,500
Not Designated as Hedging Instrument [Member] | Foreign exchange contract [Member]
Derivatives, Fair Value [Line Items]
Notional amount	$ 3,000

Derivative Financial Instrume95

Derivative Financial Instruments (Fair Value of Derivatives by Balance Sheet Location) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Derivative assets	$ 2,759	$ 3,582
Derivative liabilities	3,047	4,043
Other assets [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	2,759	3,582
Other liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liabilities	3,047	4,043
Interest rate swaps [Member] | Designated as Hedging Instrument [Member] | Other assets [Member]
Derivatives, Fair Value [Line Items]
Interest rate cash flow hedge asset at fair value	213	0
Interest rate swaps [Member] | Designated as Hedging Instrument [Member] | Other liabilities [Member]
Derivatives, Fair Value [Line Items]
Interest rate cash flow hedge liability at fair value	14	378
Interest rate caps [Member] | Designated as Hedging Instrument [Member] | Other assets [Member]
Derivatives, Fair Value [Line Items]
Interest rate cash flow hedge asset at fair value	25	134
Interest rate caps [Member] | Designated as Hedging Instrument [Member] | Other liabilities [Member]
Derivatives, Fair Value [Line Items]
Interest rate cash flow hedge liability at fair value	0	0
Interest rate floors [Member] | Designated as Hedging Instrument [Member] | Other assets [Member]
Derivatives, Fair Value [Line Items]
Interest rate cash flow hedge asset at fair value	110	0
Interest rate floors [Member] | Designated as Hedging Instrument [Member] | Other liabilities [Member]
Derivatives, Fair Value [Line Items]
Interest rate cash flow hedge liability at fair value	0	0
Interest rate lock commitments [Member] | Not Designated as Hedging Instrument [Member] | Other assets [Member]
Derivatives, Fair Value [Line Items]
Derivative asset not designated as hedging instruments	965	1,133
Interest rate lock commitments [Member] | Not Designated as Hedging Instrument [Member] | Other liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability not designated as hedging instruments	20	88
Commitments to sell mortgage loans [Member] | Not Designated as Hedging Instrument [Member] | Other assets [Member]
Derivatives, Fair Value [Line Items]
Derivative asset not designated as hedging instruments	26	279
Commitments to sell mortgage loans [Member] | Not Designated as Hedging Instrument [Member] | Other liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability not designated as hedging instruments	1,424	1,349
Interest rate swaps with customers [Member] | Not Designated as Hedging Instrument [Member] | Other assets [Member]
Derivatives, Fair Value [Line Items]
Derivative asset not designated as hedging instruments	268	2,036
Interest rate swaps with customers [Member] | Not Designated as Hedging Instrument [Member] | Other liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability not designated as hedging instruments	1,295	0
Mirror swaps with counterparties [Member] | Not Designated as Hedging Instrument [Member] | Other assets [Member]
Derivatives, Fair Value [Line Items]
Derivative asset not designated as hedging instruments	1,152	0
Mirror swaps with counterparties [Member] | Not Designated as Hedging Instrument [Member] | Other liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability not designated as hedging instruments	268	2,228
Risk participation-out agreement [Member] | Not Designated as Hedging Instrument [Member] | Other assets [Member]
Derivatives, Fair Value [Line Items]
Derivative asset not designated as hedging instruments	0	0
Risk participation-in agreement [Member] | Not Designated as Hedging Instrument [Member] | Other liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability not designated as hedging instruments	0	0
Foreign exchange contract [Member] | Not Designated as Hedging Instrument [Member] | Other assets [Member]
Derivatives, Fair Value [Line Items]
Derivative asset not designated as hedging instruments	0	0
Foreign exchange contract [Member] | Not Designated as Hedging Instrument [Member] | Other liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability not designated as hedging instruments	$ 26	$ 0

Derivative Financial Instrume96

Derivative Financial Instruments (Derivatives in Cash Flow Hedging Relationships, Effect in Statements of Changes in Shareholders' Equity and Income) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Other Comprehensive Income, Net of Tax (Effective Portion)	$ (52)	$ (257)	$ 244
Other Comprehensive Income (Loss) [Member] | Interest rate swaps [Member] | Cash Flow Hedge [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Other Comprehensive Income, Net of Tax (Effective Portion)	358	(224)	288
Other Comprehensive Income (Loss) [Member] | Interest rate caps [Member] | Cash Flow Hedge [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Other Comprehensive Income, Net of Tax (Effective Portion)	(64)	(33)	(44)
Other Comprehensive Income (Loss) [Member] | Interest rate floors [Member] | Cash Flow Hedge [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Other Comprehensive Income, Net of Tax (Effective Portion)	$ (346)	$ 0	$ 0

Derivative Financial Instrume97

Derivative Financial Instruments (Derivatives not Designated as Hedging Instruments, Effect in Statements of Income) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivative	$ 2,786	$ 4,010	$ 2,472
Interest rate lock commitments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivative	(100)	(175)	28
Interest rate lock commitments [Member] | Mortgage banking revenues [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivative	(100)	(175)	28
Commitments to sell mortgage loans [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivative	(328)	942	3
Commitments to sell mortgage loans [Member] | Mortgage banking revenues [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivative	(328)	942	3
Interest rate swaps with customers [Member] | Loan related derivative income [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivative	2,243	(598)	7,569
Mirror swaps with counterparties [Member] | Loan related derivative income [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivative	1,198	3,854	(4,904)
Risk participation agreements [Member] | Loan related derivative income [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivative	(233)	(13)	(224)
Foreign exchange contract [Member] | Loan related derivative income [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivative	$ 6	$ 0	$ 0

Balance Sheet Offsetting (Detai

Balance Sheet Offsetting (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Other assets [Member]
Gross derivative positions	$ 7,006	$ 7,812
Offsetting derivative positions	5,238	5,642
Net amounts presented in balance sheet	1,768	2,170
Cash collateral pledged	0	0
Net amount	1,768	2,170
Other assets [Member] | Interest rate caps [Member]
Gross derivative positions	25	134
Offsetting derivative positions	0	0
Net amounts presented in balance sheet	25	134
Cash collateral pledged	0	0
Net amount	25	134
Other assets [Member] | Interest rate floors [Member]
Gross derivative positions	110
Offsetting derivative positions	0
Net amounts presented in balance sheet	110
Cash collateral pledged	0
Net amount	110
Other assets [Member] | Interest rate swaps [Member]
Gross derivative positions	213
Offsetting derivative positions	0
Net amounts presented in balance sheet	213
Cash collateral pledged	0
Net amount	213
Other assets [Member] | Interest rate swaps with customers [Member]
Gross derivative positions	2,857	4,920
Offsetting derivative positions	2,589	2,884
Net amounts presented in balance sheet	268	2,036
Cash collateral pledged	0	0
Net amount	268	2,036
Other assets [Member] | Mirror swaps with counterparties [Member]
Gross derivative positions	3,801	2,758
Offsetting derivative positions	2,649	2,758
Net amounts presented in balance sheet	1,152	0
Cash collateral pledged	0	0
Net amount	1,152	0
Other liabilities [Member]
Gross derivative positions	6,841	8,248
Offsetting derivative positions	5,238	5,642
Net amounts presented in balance sheet	1,603	2,606
Cash collateral pledged	1,039	1,428
Net amount	564	1,178
Other liabilities [Member] | Interest rate swaps [Member]
Gross derivative positions	14
Offsetting derivative positions	0
Net amounts presented in balance sheet	14
Cash collateral pledged	14
Net amount	0
Other liabilities [Member] | Interest rate swaps with customers [Member]
Gross derivative positions	3,884	2,884
Offsetting derivative positions	2,589	2,884
Net amounts presented in balance sheet	1,295	0
Cash collateral pledged	1,025	0
Net amount	270	0
Other liabilities [Member] | Mirror swaps with counterparties [Member]
Gross derivative positions	2,917	4,986
Offsetting derivative positions	2,649	2,758
Net amounts presented in balance sheet	268	2,228
Cash collateral pledged	0	1,295
Net amount	268	$ 933
Other liabilities [Member] | Foreign exchange contract [Member]
Gross derivative positions	26
Offsetting derivative positions	0
Net amounts presented in balance sheet	26
Cash collateral pledged	0
Net amount	$ 26

Fair Value Measurements (Narrat

Fair Value Measurements (Narrative) (Details) - USD ($) $ in Thousands	Aug. 01, 2015	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for sale, amortized cost		$ 26,400	$ 29,400
Mortgage loans held for sale, fair value		26,943	29,434
Mortgage loans held for sale difference between fair value and principal amount		543	40
Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for sale, fair value		26,943	29,434
Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for sale, fair value		0	0
Nonrecurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Allowance for loan loss on collateral dependent impaired loans		$ 690	$ 469
Contingent Consideration [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Earn-out period post acquisition	5 years
Contingent Consideration [Member] | Maximum [Member] | Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rate for contingent consideration liability		4.00%

Fair Value Measurements (Fair V

Fair Value Measurements (Fair Value Mortgage Loans Held For Sale, Interest Rate Lock Commitments And Commitments to Sell Changes in Fair Value Disclosures) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on mortgage loans held for sale	$ 503	$ (691)	$ (48)
Total change in fair value	75	76	(17)
Interest rate lock commitments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivative	(100)	(175)	28
Commitments to sell mortgage loans [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivative	$ (328)	$ 942	$ 3

Fair Value Measurements (Assets

Fair Value Measurements (Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	$ 780,954	$ 739,912
Mortgage loans held for sale, fair value	26,943	29,434
Derivative assets	2,759	3,582
Derivative liabilities	3,047	4,043
Contingent consideration liability	1,404	2,047	$ 2,945
Obligations of U.S. government-sponsored enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	157,604	108,440
Mortgage-backed securities issued by U.S. government-sponsored agencies and U.S. government-sponsored enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	590,882	588,085
Obligations of states and political subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	2,359	14,485
Individual name issuer trust preferred debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	16,984	26,736
Corporate bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	13,125	2,166
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0	0
Derivative liabilities	0	0
Contingent consideration liability	0	0
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	2,759	3,582
Derivative liabilities	3,047	4,043
Contingent consideration liability	0	0
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0	0
Derivative liabilities	0	0
Contingent consideration liability	1,404	2,047
Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for sale, fair value	26,943	29,434
Total assets at fair value on a recurring basis	810,656	772,928
Total liabilities at fair value on a recurring basis	4,451	6,090
Recurring [Member] | Obligations of U.S. government-sponsored enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	157,604	108,440
Recurring [Member] | Mortgage-backed securities issued by U.S. government-sponsored agencies and U.S. government-sponsored enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	590,882	588,085
Recurring [Member] | Obligations of states and political subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	2,359	14,485
Recurring [Member] | Individual name issuer trust preferred debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	16,984	26,736
Recurring [Member] | Corporate bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	13,125	2,166
Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for sale, fair value	0	0
Total assets at fair value on a recurring basis	0	0
Total liabilities at fair value on a recurring basis	0	0
Recurring [Member] | Level 1 [Member] | Obligations of U.S. government-sponsored enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	0	0
Recurring [Member] | Level 1 [Member] | Mortgage-backed securities issued by U.S. government-sponsored agencies and U.S. government-sponsored enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	0	0
Recurring [Member] | Level 1 [Member] | Obligations of states and political subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	0	0
Recurring [Member] | Level 1 [Member] | Individual name issuer trust preferred debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	0	0
Recurring [Member] | Level 1 [Member] | Corporate bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	0	0
Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for sale, fair value	26,943	29,434
Total assets at fair value on a recurring basis	810,656	772,928
Total liabilities at fair value on a recurring basis	3,047	4,043
Recurring [Member] | Level 2 [Member] | Obligations of U.S. government-sponsored enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	157,604	108,440
Recurring [Member] | Level 2 [Member] | Mortgage-backed securities issued by U.S. government-sponsored agencies and U.S. government-sponsored enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	590,882	588,085
Recurring [Member] | Level 2 [Member] | Obligations of states and political subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	2,359	14,485
Recurring [Member] | Level 2 [Member] | Individual name issuer trust preferred debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	16,984	26,736
Recurring [Member] | Level 2 [Member] | Corporate bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	13,125	2,166
Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for sale, fair value	0	0
Total assets at fair value on a recurring basis	0	0
Total liabilities at fair value on a recurring basis	1,404	2,047
Recurring [Member] | Level 3 [Member] | Obligations of U.S. government-sponsored enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	0	0
Recurring [Member] | Level 3 [Member] | Mortgage-backed securities issued by U.S. government-sponsored agencies and U.S. government-sponsored enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	0	0
Recurring [Member] | Level 3 [Member] | Obligations of states and political subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	0	0
Recurring [Member] | Level 3 [Member] | Individual name issuer trust preferred debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	0	0
Recurring [Member] | Level 3 [Member] | Corporate bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	$ 0	$ 0

Fair Value Measurements Fair Va

Fair Value Measurements Fair Value Measurements (Change in contingent consideration) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 2,047	$ 2,945
Change in fair value	(643)	(898)	$ 41
Payments	0	0
Ending Balance	$ 1,404	$ 2,047	$ 2,945

Fair Value Measurements (Ass103

Fair Value Measurements (Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis) (Details) - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent impaired loans	[1]	$ 5,993	$ 7,079
Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent impaired loans		1,425	3,828
Property acquired through foreclosure or repossession		131	605
Total assets at fair value on a nonrecurring basis		1,556	4,433
Nonrecurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent impaired loans		0	0
Property acquired through foreclosure or repossession		0	0
Total assets at fair value on a nonrecurring basis		0	0
Nonrecurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent impaired loans		0	0
Property acquired through foreclosure or repossession		0	0
Total assets at fair value on a nonrecurring basis		0	0
Nonrecurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent impaired loans		1,425	3,828
Property acquired through foreclosure or repossession		131	605
Total assets at fair value on a nonrecurring basis		$ 1,556	$ 4,433
[1]	The recorded investment in impaired loans consists of unpaid principal balance, net of charge-offs, interest payments received applied to principal and unamortized deferred loan origination fees and costs. For accruing impaired loans (troubled debt restructurings for which management has concluded that the collectability of the loan is not in doubt), the recorded investment also includes accrued interest.

Fair Value Measurements (Qualit

Fair Value Measurements (Qualitative Information About Level 3 Assets Measured at Fair Value on a Nonrecurring Basis) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016
Fair Value Inputs Assets Qualitative Information [Line Items]
Collateral dependent impaired loans	[1]	$ 5,993	$ 7,079
Nonrecurring [Member]
Fair Value Inputs Assets Qualitative Information [Line Items]
Collateral dependent impaired loans		1,425	3,828
Property acquired through foreclosure or repossession		131	605
Nonrecurring [Member] | Level 3 [Member]
Fair Value Inputs Assets Qualitative Information [Line Items]
Collateral dependent impaired loans		1,425	3,828
Property acquired through foreclosure or repossession		$ 131	$ 605
Nonrecurring [Member] | Level 3 [Member] | Appraisals Of Collateral [Member] | Collateral Dependent Impaired Loans [Member] | Minimum [Member]
Fair Value Inputs Assets Qualitative Information [Line Items]
Discount for costs to sell		0.00%	10.00%
Appraisal adjustments			0.00%
Nonrecurring [Member] | Level 3 [Member] | Appraisals Of Collateral [Member] | Collateral Dependent Impaired Loans [Member] | Maximum [Member]
Fair Value Inputs Assets Qualitative Information [Line Items]
Discount for costs to sell		15.00%	20.00%
Appraisal adjustments			10.00%
Nonrecurring [Member] | Level 3 [Member] | Appraisals Of Collateral [Member] | Collateral Dependent Impaired Loans [Member] | Weighted Average [Member]
Fair Value Inputs Assets Qualitative Information [Line Items]
Discount for costs to sell		15.00%	15.00%
Appraisal adjustments			9.00%
Nonrecurring [Member] | Level 3 [Member] | Appraisals Of Collateral [Member] | Property Acquired Through Foreclosure Or Repossession [Member] | Minimum [Member]
Fair Value Inputs Assets Qualitative Information [Line Items]
Discount for costs to sell		10.00%	10.00%
Appraisal adjustments		12.00%	6.00%
Nonrecurring [Member] | Level 3 [Member] | Appraisals Of Collateral [Member] | Property Acquired Through Foreclosure Or Repossession [Member] | Maximum [Member]
Fair Value Inputs Assets Qualitative Information [Line Items]
Discount for costs to sell		10.00%	12.00%
Appraisal adjustments		17.00%	50.00%
Nonrecurring [Member] | Level 3 [Member] | Appraisals Of Collateral [Member] | Property Acquired Through Foreclosure Or Repossession [Member] | Weighted Average [Member]
Fair Value Inputs Assets Qualitative Information [Line Items]
Discount for costs to sell		10.00%	11.00%
Appraisal adjustments		15.00%	24.00%
[1]	The recorded investment in impaired loans consists of unpaid principal balance, net of charge-offs, interest payments received applied to principal and unamortized deferred loan origination fees and costs. For accruing impaired loans (troubled debt restructurings for which management has concluded that the collectability of the loan is not in doubt), the recorded investment also includes accrued interest.

Fair Value Measurements (Carryi

Fair Value Measurements (Carrying Amounts and Estimated Fair Values of Financial Instruments) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held to maturity securities	$ 12,541	$ 15,633
Loans, net of allowance of loan losses	3,347,583	3,208,367
Time deposits	1,015,095	961,613
Federal Home Loan Bank advances	791,356	848,930
Junior subordinated debentures	22,681	22,681
Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held to maturity securities	12,541	15,633
Loans, net of allowance of loan losses	3,347,583	3,208,367
Time deposits	1,015,095	961,613
Federal Home Loan Bank advances	791,356	848,930
Junior subordinated debentures	22,681	22,681
Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held to maturity securities	12,721	15,920
Loans, net of allowance of loan losses	3,369,932	3,218,651
Time deposits	1,018,396	962,374
Federal Home Loan Bank advances	792,887	852,888
Junior subordinated debentures	18,559	16,970
Estimate of Fair Value Measurement [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held to maturity securities	0	0
Loans, net of allowance of loan losses	0	0
Time deposits	0	0
Federal Home Loan Bank advances	0	0
Junior subordinated debentures	0	0
Estimate of Fair Value Measurement [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held to maturity securities	12,721	15,920
Loans, net of allowance of loan losses	0	0
Time deposits	1,018,396	962,374
Federal Home Loan Bank advances	792,887	852,888
Junior subordinated debentures	18,559	16,970
Estimate of Fair Value Measurement [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held to maturity securities	0	0
Loans, net of allowance of loan losses	3,369,932	3,218,651
Time deposits	0	0
Federal Home Loan Bank advances	0	0
Junior subordinated debentures	$ 0	$ 0

Employee Benefits (Narrative) (

Employee Benefits (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended			120 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 30, 2023
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, employer matching contribution amounts	$ 2,300	$ 2,300	$ 1,800
Other incentive-based compensation expense	16,900	16,000	$ 14,300
Deferred compensation plan, accrued liability	$ 14,200	10,800
Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, employer matching contribution	3.00%
Qualified Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Funded (unfunded) status at end of period	$ 6,641	2,836
Accumulated benefit obligation	72,900	65,800
Estimated amortization of prior service cost (credit) from accumulated other comprehensive loss into net period benefit cost, next year	(23)
Estimated amortization of (gain) loss from accumulated other comprehensive loss into net period benefit cost, next year	$ 1,500
Fair value of equity securities, maximum percentage held by a single issuer	10.00%
Estimated future employer contributions in next fiscal year	$ 3,000
Qualified Pension Plan [Member] | Equity Securities [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	50.00%
Qualified Pension Plan [Member] | Equity Securities [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	70.00%
Qualified Pension Plan [Member] | Small-Cap Equity Securities [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	20.00%
Qualified Pension Plan [Member] | Mid-Cap Equity Securities [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	20.00%
Qualified Pension Plan [Member] | International Equity Securities [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	30.00%
Qualified Pension Plan [Member] | Fixed Income Securities [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	30.00%
Qualified Pension Plan [Member] | Fixed Income Securities [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	50.00%
Qualified Pension Plan [Member] | Cash and Cash Equivalents [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	0.00%
Qualified Pension Plan [Member] | Cash and Cash Equivalents [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	10.00%
Qualified Pension Plan [Member] | High Yield Bond [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	10.00%
Non-Qualified Retirement Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Available-for-sale securities and other short-term investments, rabbi trusts	$ 13,300	11,700
Funded (unfunded) status at end of period	(15,203)	(13,154)
Accumulated benefit obligation	14,000	$ 12,000
Estimated amortization of prior service cost (credit) from accumulated other comprehensive loss into net period benefit cost, next year	(1)
Estimated amortization of (gain) loss from accumulated other comprehensive loss into net period benefit cost, next year	287
Estimated future employer contributions in next fiscal year	$ 897
Scenario, Forecast [Member]
Defined Benefit Plan Disclosure [Line Items]
Transition Period Pension Plan Amendment				10 years
Non-elective Employer Contribution [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, employer matching contribution	4.00%

Employee Benefits (Schedule of

Employee Benefits (Schedule of Net Funded (Unfunded) Status) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Qualified Pension Plan [Member]
Change in Benefit Obligation:
Benefit obligation at beginning of period	$ 72,951	$ 67,550
Service cost	2,149	2,148	$ 2,459
Interest cost	2,673	2,576	2,928
Actuarial loss	7,017	3,888
Benefits paid	(3,936)	(3,072)
Administrative expenses	(131)	(139)
Benefit obligation at end of period	80,723	72,951	67,550
Change in Plan Assets:
Fair value of plan assets at beginning of period	75,787	65,710
Actual return on plan assets	12,644	4,788
Employer contributions	3,000	8,500
Benefits paid	(3,936)	(3,072)
Administrative expenses	(131)	(139)
Fair value of plan assets at end of period	87,364	75,787	65,710
Funded (unfunded) status at end of period	6,641	2,836
Non-Qualified Retirement Plans [Member]
Change in Benefit Obligation:
Benefit obligation at beginning of period	13,154	13,015
Service cost	129	122	78
Interest cost	428	432	490
Actuarial loss	2,275	374
Benefits paid	(783)	(789)
Administrative expenses	0	0
Benefit obligation at end of period	15,203	13,154	13,015
Change in Plan Assets:
Fair value of plan assets at beginning of period	0	0
Actual return on plan assets	0	0
Employer contributions	783	789
Benefits paid	(783)	(789)
Administrative expenses	0	0
Fair value of plan assets at end of period	0	0	$ 0
Funded (unfunded) status at end of period	$ (15,203)	$ (13,154)

Employee Benefits (Components o

Employee Benefits (Components of Accumulated Other Comprehensive Income(Loss)) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Qualified Pension Plan [Member]
Components of Accumulated Other Comprehensive Income (Loss), before Tax [Abstract]
Net actuarial loss	$ 13,795	$ 15,593
Prior service credit	(39)	(62)
Total pre-tax amounts recognized in accumulated other comprehensive income	13,756	15,531
Non-Qualified Retirement Plans [Member]
Components of Accumulated Other Comprehensive Income (Loss), before Tax [Abstract]
Net actuarial loss	6,448	4,519
Prior service credit	(1)	(1)
Total pre-tax amounts recognized in accumulated other comprehensive income	$ 6,447	$ 4,518

Employee Benefits (Component109

Employee Benefits (Components of Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Loss) (on a pre-tax basis):
Net (gain) loss		$ 1,591	$ 4,106	$ (1,478)
Prior service cost	[1]	(15)	(15)	(17)
Recognized in other comprehensive (loss) income		(154)	(3,055)	2,948
Qualified Pension Plan [Member]
Net Periodic Benefit Cost:
Service cost		2,149	2,148	2,459
Interest cost		2,673	2,576	2,928
Expected return on plan assets		(4,942)	(4,633)	(4,515)
Amortization of prior service credit		(23)	(23)	(23)
Recognized net actuarial loss		1,114	828	1,249
Net periodic benefit cost		971	896	2,098
Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Loss) (on a pre-tax basis):
Net (gain) loss		(1,798)	2,904	(2,816)
Prior service cost		23	23	23
Recognized in other comprehensive (loss) income		(1,775)	2,927	(2,793)
Total recognized in net periodic benefit cost and other comprehensive income (loss)		(804)	3,823	(695)
Non-Qualified Retirement Plans [Member]
Net Periodic Benefit Cost:
Service cost		129	122	78
Interest cost		428	432	490
Expected return on plan assets		0	0	0
Amortization of prior service credit		(1)	(1)	(1)
Recognized net actuarial loss		347	247	245
Net periodic benefit cost		903	800	812
Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Loss) (on a pre-tax basis):
Net (gain) loss		1,928	127	(156)
Prior service cost		1	1	1
Recognized in other comprehensive (loss) income		1,929	128	(155)
Total recognized in net periodic benefit cost and other comprehensive income (loss)		$ 2,832	$ 928	$ 657
[1]	The pre-tax amount is included in salaries and employee benefits expense in the Consolidated Statements of Income.

Employee Benefits (Weighted-Ave

Employee Benefits (Weighted-Average Assumptions Used) (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Qualified Pension Plan [Member]
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Discount rate	3.69%	4.18%
Rate of compensation increase	3.75%	3.75%
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate			4.125%
Equivalent single discount rate for benefit obligations	4.18%	4.48%
Equivalent single discount rate for service cost	4.29%	4.63%
Equivalent single discount rate for interest cost	3.73%	3.88%
Expected long-term return on plan assets	6.75%	6.75%	7.25%
Rate of compensation increase	3.75%	3.75%	3.75%
Non-Qualified Retirement Plans [Member]
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Discount rate	3.60%	4.00%
Rate of compensation increase	3.75%	3.75%
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate			3.90%
Equivalent single discount rate for benefit obligations	4.00%	4.20%
Equivalent single discount rate for service cost	4.25%	4.59%
Equivalent single discount rate for interest cost	3.40%	3.44%
Rate of compensation increase	3.75%	3.75%	3.75%

Employee Benefits (Schedule 111

Employee Benefits (Schedule of Fair Value of Qualified Pension Plan Assets) (Details) - Qualified Pension Plan [Member] - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Actual Plan Asset Allocations	100.00%	100.00%
Fair value of plan assets	$ 87,364	$ 75,787	$ 65,710
Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	65,355	54,361
Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	22,009	21,426
Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0	$ 0
Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Actual Plan Asset Allocations	65.70%	63.80%
Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Actual Plan Asset Allocations	30.00%	32.40%
Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Actual Plan Asset Allocations	4.30%	3.80%
Fair value of plan assets	$ 3,760	$ 2,880
Cash and Cash Equivalents [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,760	2,880
Cash and Cash Equivalents [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Cash and Cash Equivalents [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Obligations of U.S Government Agencies and U.S. Government-Sponsored Enterprises [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5,926	4,233
Obligations of U.S Government Agencies and U.S. Government-Sponsored Enterprises [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Obligations of U.S Government Agencies and U.S. Government-Sponsored Enterprises [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5,926	4,233
Obligations of U.S Government Agencies and U.S. Government-Sponsored Enterprises [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Obligations of states and political subdivisions [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,971	3,418
Obligations of states and political subdivisions [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Obligations of states and political subdivisions [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,971	3,418
Obligations of states and political subdivisions [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Corporate bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	13,112	13,775
Corporate bonds [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Corporate bonds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	13,112	13,775
Corporate bonds [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Common Stocks [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	38,508	33,893
Common Stocks [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	38,508	33,893
Common Stocks [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Common Stocks [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	23,087	17,588
Mutual Funds [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	23,087	17,588
Mutual Funds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Mutual Funds [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0	$ 0

Employee Benefits (Estimated Fu

Employee Benefits (Estimated Future Benefit Payments) (Details) $ in Thousands	Dec. 31, 2017USD ($)
Qualified Pension Plan [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
Expected Future Payments, Next Twelve Months	$ 3,964
Expected Future Payments, Year Two	2,931
Expected Future Payments, Year Three	3,387
Expected Future Payments, Year Four	3,784
Expected Future Payments, Year Five	4,378
Expected Future Payments, Thereafter	28,050
Non-Qualified Retirement Plans [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
Expected Future Payments, Next Twelve Months	897
Expected Future Payments, Year Two	891
Expected Future Payments, Year Three	879
Expected Future Payments, Year Four	868
Expected Future Payments, Year Five	891
Expected Future Payments, Thereafter	$ 4,221

Share-Based Compensation Arr113

Share-Based Compensation Arrangements (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Apr. 23, 2013	Apr. 28, 2009
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost	$ 4
Weighted average recognition period (in years)	1 year 11 months 28 days
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share options exercised total intrinsic value	$ 1	$ 3.2	$ 1.2
Cliff vesting period (years)	3 years	3 years
Time Based Nonvested Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested share units	15,900	22,175	16,275
Performance Based Nonvested Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance share awards minimum shares earned to target percentage	0.00%
Performance share awards maximum shares earned to target percentage	200.00%
Nonvested share units	36,470
Cliff vesting period (years)	3 years	3 years	3 years
Performance share awards, shares vesting	117,465
Minimum [Member] | Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cliff vesting period (years)			3 years
Minimum [Member] | Time Based Nonvested Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cliff vesting period (years)	3 years	3 years	3 years
Maximum [Member] | Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cliff vesting period (years)			5 years
Maximum [Member] | Time Based Nonvested Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cliff vesting period (years)	5 years	3 years
2013 Stock Option and Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized				1,748,250
Amended and Restated 2003 Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized					1,200,000
Amended and Restated 2003 Stock Incentive Plan [Member] | Stock Options and Stock Appreciation Rights [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized					400,000

Share-Based Compensation Arr114

Share-Based Compensation Arrangements (Compensation Cost for Share-based Compensation Arrangements) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-based compensation expense	$ 2,577	$ 2,190	$ 2,074
Related income tax benefit	$ 606	$ 810	$ 767

Share-Based Compensation Arr115

Share-Based Compensation Arrangements (Share Options Fair Value Assumptions) (Details) - Stock Options [Member] - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted	47,725	53,400	48,600
Cliff vesting period (years)	3 years	3 years
Expected term (years)	7 years	7 years 6 months	7 years 6 months
Expected dividend yield	3.57%	3.89%	3.94%
Weighted average expected volatility	27.10%	29.99%	40.76%
Weighted average risk-free interest rate	1.70%	1.66%	1.95%
Weighted average grant-date fair value	$ 10.60	$ 7.92	$ 11.15
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cliff vesting period (years)			3 years
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cliff vesting period (years)			5 years

Share-Based Compensation Arr116

Share-Based Compensation Arrangements (Share Options Activity) (Details) - Stock Options [Member] - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Number of Share Options:
Beginning of period	219,279
Granted	47,725	53,400	48,600
Exercised	(39,076)
Forfeited or expired	(4,075)
End of period	223,853	219,279
Options exercisable	80,003
Options expected to vest in future periods	143,850
Weighted Average Exercise Price (in dollars per share):
Beginning of period	$ 32.70
Granted	58.05
Exercised	28.30
Forfeited or expired	43.06
End of period	38.68	$ 32.70
Options exercisable	25.89
Options expected to vest in future periods	$ 45.80
Outstanding Weighted Average Remaining Contractual Term	7 years 2 months 20 days
Exercisable Weighted Average Remaining Contractual Term	4 years 4 months 18 days
Expected to Vest Weighted Average Remaining Contractual Term	8 years 9 months 18 days
Outstanding Aggregate Intrinsic Value	$ 3,487
Exercisable Aggregate Intrinsic Value	2,189
Expected to Vest Aggregate Intrinsic Value	$ 1,298

Share-Based Compensation Arr117

Share-Based Compensation Arrangements (Stock Options Outstanding and Options Exercisable) (Details)	12 Months Ended
	Dec. 31, 2017$ / sharesshares
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Number of Share Options | shares	223,853
Options Outstanding, Weighted Average Remaining Life (Years)	7 years 2 months 20 days
Options Outstanding, Weighted Average Exercise Price	$ 38.68
Options Exercisable, Number of Share Options | shares	80,003
Options Exercisable, Weighted Average Exercise Price	$ 25.89
$15.01 to $20.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Ranges, Lower Range Limit	15.01
Exercise Price Ranges, Upper Range Limit	$ 20
Options Outstanding, Number of Share Options | shares	11,700
Options Outstanding, Weighted Average Remaining Life (Years)	1 year 10 months 15 days
Options Outstanding, Weighted Average Exercise Price	$ 17.52
Options Exercisable, Number of Share Options | shares	11,700
Options Exercisable, Weighted Average Exercise Price	$ 17.52
$20.01 to $25.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Ranges, Lower Range Limit	20.01
Exercise Price Ranges, Upper Range Limit	$ 25
Options Outstanding, Number of Share Options | shares	38,593
Options Outstanding, Weighted Average Remaining Life (Years)	3 years 10 months 18 days
Options Outstanding, Weighted Average Exercise Price	$ 23.14
Options Exercisable, Number of Share Options | shares	38,593
Options Exercisable, Weighted Average Exercise Price	$ 23.14
$25.01 to $30.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Ranges, Lower Range Limit	25.01
Exercise Price Ranges, Upper Range Limit	$ 30
Options Outstanding, Number of Share Options | shares	0
Options Outstanding, Weighted Average Remaining Life (Years)	0 years
Options Outstanding, Weighted Average Exercise Price	$ 0
Options Exercisable, Number of Share Options | shares	0
Options Exercisable, Weighted Average Exercise Price	$ 0
$30.01 to $35.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Ranges, Lower Range Limit	30.01
Exercise Price Ranges, Upper Range Limit	$ 35
Options Outstanding, Number of Share Options | shares	29,710
Options Outstanding, Weighted Average Remaining Life (Years)	6 years
Options Outstanding, Weighted Average Exercise Price	$ 32.76
Options Exercisable, Number of Share Options | shares	29,710
Options Exercisable, Weighted Average Exercise Price	$ 32.76
$35.01 to $40.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Ranges, Lower Range Limit	35.01
Exercise Price Ranges, Upper Range Limit	$ 40
Options Outstanding, Number of Share Options | shares	46,000
Options Outstanding, Weighted Average Remaining Life (Years)	7 years 9 months 2 days
Options Outstanding, Weighted Average Exercise Price	$ 39.39
Options Exercisable, Number of Share Options | shares	0
Options Exercisable, Weighted Average Exercise Price	$ 0
$40.01 to $45.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Ranges, Lower Range Limit	40.01
Exercise Price Ranges, Upper Range Limit	$ 45
Options Outstanding, Number of Share Options | shares	50,800
Options Outstanding, Weighted Average Remaining Life (Years)	8 years 9 months 18 days
Options Outstanding, Weighted Average Exercise Price	$ 40.25
Options Exercisable, Number of Share Options | shares	0
Options Exercisable, Weighted Average Exercise Price	$ 0
$45.01 to $50.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Ranges, Lower Range Limit	45.01
Exercise Price Ranges, Upper Range Limit	$ 50
Options Outstanding, Number of Share Options | shares	0
Options Outstanding, Weighted Average Remaining Life (Years)	0 years
Options Outstanding, Weighted Average Exercise Price	$ 0
Options Exercisable, Number of Share Options | shares	0
Options Exercisable, Weighted Average Exercise Price	$ 0
$50.01 to $55.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Ranges, Lower Range Limit	50.01
Exercise Price Ranges, Upper Range Limit	$ 55
Options Outstanding, Number of Share Options | shares	0
Options Outstanding, Weighted Average Remaining Life (Years)	0 years
Options Outstanding, Weighted Average Exercise Price	$ 0
Options Exercisable, Number of Share Options | shares	0
Options Exercisable, Weighted Average Exercise Price	$ 0
$55.01 to $60.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Ranges, Lower Range Limit	55.01
Exercise Price Ranges, Upper Range Limit	$ 60
Options Outstanding, Number of Share Options | shares	47,050
Options Outstanding, Weighted Average Remaining Life (Years)	9 years 9 months 18 days
Options Outstanding, Weighted Average Exercise Price	$ 58.05
Options Exercisable, Number of Share Options | shares	0
Options Exercisable, Weighted Average Exercise Price	$ 0

Share-Based Compensation Arr118

Share-Based Compensation Arrangements (Nonvested Share Units Activity) (Details) - Time Based Nonvested Shares [Member] - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Number of Shares:
Beginning of period	49,675
Granted	15,900	22,175	16,275
Vested	(11,325)
Forfeited	(475)
End of period	53,775	49,675
Weighted Average Grant Date Fair Value (in dollars per share):
Beginning of period	$ 37.12
Granted	54.46
Vested	32.79
Forfeited	40.25
End of period	$ 43.13	$ 37.12

Share-Based Compensation Arr119

Share-Based Compensation Arrangements (Nonvested Performance Shares Outstanding) (Details) - Performance Based Nonvested Shares [Member]	12 Months Ended
	Dec. 31, 2017$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance share awards, shares vesting	117,465
2017 Grant [Domain]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance share awards granted, grant date fair value | $ / shares	$ 51.85
Performance share awards, shares vesting percentages	140.00%
Performance share awards, shares vesting	36,470
2016 Grant [Domain]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance share awards granted, grant date fair value | $ / shares	$ 36.11
Performance share awards, shares vesting percentages	133.00%
Performance share awards, shares vesting	45,220
2015 Grant [Domain]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance share awards granted, grant date fair value | $ / shares	$ 38.02
Performance share awards, shares vesting percentages	135.00%
Performance share awards, shares vesting	35,775

Share-Based Compensation Arr120

Share-Based Compensation Arrangements (Nonvested Performance Shares Activity) (Details) - Performance Based Nonvested Shares [Member]	12 Months Ended
	Dec. 31, 2017$ / sharesshares
Number of Shares:
Beginning of period | shares	101,998
Granted | shares	36,470
Vested | shares	(16,707)
Forfeited | shares	(4,296)
End of period | shares	117,465
Weighted Average Grant Date Fair Value (in dollars per share):
Beginning of period | $ / shares	$ 36.58
Granted | $ / shares	51.85
Vested | $ / shares	34.66
Forfeited | $ / shares	36.93
End of period | $ / shares	$ 41.58

Business Segments (Statement of

Business Segments (Statement of Operations and Total Assets by Reportable Segment) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Net interest income (expense)	$ 30,889	$ 30,059	$ 29,904	$ 28,679	$ 28,588	$ 27,379	$ 26,776	$ 27,735	$ 119,531	$ 110,478	$ 103,982
Provision for loan losses	200	1,300	700	400	2,900	1,800	450	500	2,600	5,650	1,050
Net interest income after provision for loan losses	30,689	28,759	29,204	28,279	25,688	25,579	26,326	27,235	116,931	104,828	102,932
Noninterest income	16,210	17,283	16,806	14,510	17,320	17,261	15,914	14,634	64,809	65,129	58,340
Depreciation and amortization expense									4,489	4,935	4,285
Other noninterest expenses									99,611	96,168	92,644
Total noninterest expense	25,754	26,754	26,306	25,286	24,973	24,650	26,030	25,450	104,100	101,103	96,929
Income before income taxes	21,145	19,288	19,704	17,503	18,035	18,190	16,210	16,419	77,640	68,854	64,343
Income tax expense	13,163	6,326	6,505	5,721	5,873	5,863	5,153	5,484	31,715	22,373	20,878
Net income	7,982	$ 12,962	$ 13,199	$ 11,782	12,162	$ 12,327	$ 11,057	$ 10,935	45,925	46,481	43,465
Total assets at period end	4,529,850				4,381,115				4,529,850	4,381,115	3,771,604
Expenditures for long-lived assets									2,779	3,112	5,479
Commercial Banking [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)									98,736	91,221	84,757
Provision for loan losses									2,600	5,650	1,050
Net interest income after provision for loan losses									96,136	85,571	83,707
Noninterest income									23,244	24,783	20,618
Depreciation and amortization expense									2,604	2,771	2,584
Other noninterest expenses									60,828	58,452	55,203
Total noninterest expense									63,432	61,223	57,787
Income before income taxes									55,948	49,131	46,538
Income tax expense									23,876	16,790	15,330
Net income									32,072	32,341	31,208
Total assets at period end	3,491,845				3,354,633				3,491,845	3,354,633	3,152,231
Expenditures for long-lived assets									2,224	2,267	4,714
Wealth Management Services [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)									(167)	(66)	(47)
Provision for loan losses									0	0	0
Net interest income after provision for loan losses									(167)	(66)	(47)
Noninterest income									39,346	37,569	35,416
Depreciation and amortization expense									1,689	1,940	1,488
Other noninterest expenses									26,718	25,239	25,632
Total noninterest expense									28,407	27,179	27,120
Income before income taxes									10,772	10,324	8,249
Income tax expense									3,795	3,692	3,475
Net income									6,977	6,632	4,774
Total assets at period end	66,083				64,625				66,083	64,625	63,801
Expenditures for long-lived assets									360	464	411
Corporate [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)									20,962	19,323	19,272
Provision for loan losses									0	0	0
Net interest income after provision for loan losses									20,962	19,323	19,272
Noninterest income									2,219	2,777	2,306
Depreciation and amortization expense									196	224	213
Other noninterest expenses									12,065	12,477	11,809
Total noninterest expense									12,261	12,701	12,022
Income before income taxes									10,920	9,399	9,556
Income tax expense									4,044	1,891	2,073
Net income									6,876	7,508	7,483
Total assets at period end	$ 971,922				$ 961,857				971,922	961,857	555,572
Expenditures for long-lived assets									$ 195	$ 381	$ 354

Other Comprehensive Income (122

Other Comprehensive Income (Loss) (Activity in Other Comprehensive Income) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract]
Change in fair value of securities available for sale, before tax		$ 986		$ (12,502)		$ (4,926)
Change in fair value of securities available for sale, tax		365		(4,626)		(1,755)
Change is fair value of securities available for sale		621		(7,876)		(3,171)
Net (gains) losses on securities classified into earnings, before tax		0		0		0
Net (gains) losses on securities classified into earnings, tax		0		0		0
Net (gains) losses on securities classified into earnings		0		0		0
Net change in fair value of securities available for sale, before tax		986		(12,502)		(4,926)
Net change in fair value of securities available for sale, tax		365		(4,626)		(1,755)
Net change in fair value of securities available for sale		621		(7,876)		(3,171)
Net change in fair value of cash flow hedges, before tax		(774)		(403)		(102)
Net change in fair value of cash flow hedges, tax		(223)		(146)		(49)
Change in fair value of cash flow hedges		(551)		(257)		(53)
Net cash flow hedge losses reclassified into earnings, before tax		792	[1]	0	[1]	469	[2]
Net cash flow hedge losses reclassified into earnings, tax		293	[1]	0	[1]	172	[2]
Net cash flow hedge losses reclassified into earnings		499	[1]	0	[1]	297	[2]
Change in fair value of cash flow hedges, before tax		18		(403)		367
Change in fair value of cash flow hedges, tax		70		(146)		123
Net change in fair value of cash flow hedges		(52)		(257)		244
Defined benefit plan obligation adjustment, before tax		(1,591)		(4,106)		1,478
Defined benefit plan obligation adjustment, tax		(594)		(1,518)		376
Defined benefit plan obligation adjustment		(997)		(2,588)		1,102
Amortization of net actuarial losses, before tax	[3]	1,461		1,075		1,494
Amortization of net actuarial losses, tax	[3]	546		397		542
Amortization of net actuarial losses	[3]	915		678		952
Amortization of net prior service credits, before tax	[3]	(24)		(24)		(24)
Amortization of net prior service credits, tax	[3]	(9)		(9)		(7)
Amortization of net prior service credits	[3]	(15)		(15)		(17)
Net change in defined benefit plan obligations, before tax		(154)		(3,055)		2,948
Net change in defined benefit plan obligations, tax		(57)		(1,130)		911
Net change in defined benefit plan obligations		(97)		(1,925)		2,037
Total other comprehensive income (loss), before tax		850		(15,960)		(1,611)
Total other comprehensive income (loss), tax		378		(5,902)		(721)
Total other comprehensive income (loss), net of tax		472		(10,058)		(890)
Net Unrealized Gains on AFS Securities [Member]
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract]
Total other comprehensive income (loss), net of tax		$ 621		$ (7,876)		$ (3,171)
[1]	The pre-tax amounts are included in interest expense on Federal Home Loan Bank advances, interest expense on junior subordinated debentures and interest income and fees on loans in the Consolidated Statements of Income.
[2]	The pre-tax amount is included in interest expense on junior subordinated debentures in the Consolidated Statements of Income.
[3]	The pre-tax amount is included in salaries and employee benefits expense in the Consolidated Statements of Income.

Other Comprehensive Income (123

Other Comprehensive Income (Loss) (Components of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated other comprehensive income (loss), beginning balance	$ (19,757)
Net other comprehensive income (loss)	472	$ (10,058)	$ (890)
Reclassification of income tax effects due to the adoption of ASU 2018-02	0
Accumulated other comprehensive income (loss), ending balance	(23,510)	(19,757)
Net Unrealized Gains on AFS Securities [Member]
Accumulated other comprehensive income (loss), beginning balance	(6,825)	1,051	4,222
Other comprehensive income (loss) before reclassifications, net of tax	621	(7,876)	(3,171)
Amounts reclassified from accumulated other comprehensive income, net of tax	0	0	0
Net other comprehensive income (loss)	621	(7,876)	(3,171)
Reclassification of income tax effects due to the adoption of ASU 2018-02	(1,330)
Accumulated other comprehensive income (loss), ending balance	(7,534)	(6,825)	1,051
Net Unrealized Losses on Cash Flow Hedges [Member]
Accumulated other comprehensive income (loss), beginning balance	(300)	(43)	(287)
Other comprehensive income (loss) before reclassifications, net of tax	(551)	(257)	(53)
Amounts reclassified from accumulated other comprehensive income, net of tax	499	0	297
Net other comprehensive income (loss)	(52)	(257)	244
Reclassification of income tax effects due to the adoption of ASU 2018-02	(76)
Accumulated other comprehensive income (loss), ending balance	(428)	(300)	(43)
Pension Benefit Adjustment [Member]
Accumulated other comprehensive income (loss), beginning balance	(12,632)	(10,707)	(12,744)
Other comprehensive income (loss) before reclassifications, net of tax	(741)	(2,588)	1,102
Amounts reclassified from accumulated other comprehensive income, net of tax	644	663	935
Net other comprehensive income (loss)	(97)	(1,925)	2,037
Reclassification of income tax effects due to the adoption of ASU 2018-02	(2,819)
Accumulated other comprehensive income (loss), ending balance	(15,548)	(12,632)	(10,707)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated other comprehensive income (loss), beginning balance	(19,757)	(9,699)	(8,809)
Other comprehensive income (loss) before reclassifications, net of tax	(671)	(10,721)	(2,122)
Amounts reclassified from accumulated other comprehensive income, net of tax	1,143	663	1,232
Net other comprehensive income (loss)	472	(10,058)	(890)
Reclassification of income tax effects due to the adoption of ASU 2018-02	(4,225)
Accumulated other comprehensive income (loss), ending balance	$ (23,510)	$ (19,757)	$ (9,699)

Earnings Per Common Share (Deta

Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Net income	$ 7,982	$ 12,962	$ 13,199	$ 11,782	$ 12,162	$ 12,327	$ 11,057	$ 10,935	$ 45,925	$ 46,481	$ 43,465
Less dividends and undistributed earnings allocated to participating securities									(108)	(97)	(126)
Net income applicable to common shareholders									$ 45,817	$ 46,384	$ 43,339
Weighted average common shares outstanding - basic	17,223,000	17,212,000	17,206,000	17,186,000	17,142,000	17,090,000	17,067,000	17,023,000	17,207,000	17,081,000	16,879,000
Basic earnings per common share (in dollars per share)	$ 0.46	$ 0.75	$ 0.77	$ 0.68	$ 0.71	$ 0.72	$ 0.65	$ 0.64	$ 2.66	$ 2.72	$ 2.57
Less dividends and undistributed earnings allocated to participating securities									$ (108)	$ (97)	$ (126)
Net income applicable to common shareholders									$ 45,817	$ 46,384	$ 43,339
Dilutive effect of common stock equivalents (in shares)									131,000	127,000	188,000
Weighted average common shares outstanding - diluted (in shares)	17,349,000	17,318,000	17,316,000	17,293,000	17,245,000	17,203,000	17,194,000	17,157,000	17,338,000	17,208,000	17,067,000
Diluted earnings per common share (in dollars per share)	$ 0.46	$ 0.75	$ 0.76	$ 0.68	$ 0.70	$ 0.72	$ 0.64	$ 0.64	$ 2.64	$ 2.70	$ 2.54
Antidilutive common stock equivalents									11,572	59,158	34,850

Commitments and Contingencie125

Commitments and Contingencies (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Commitments and Contingencies Disclosure [Line Items]
Standby letters of credit extension period	1 year
Operating leases rental expense	$ 4,300	$ 4,000	$ 3,500
Unpaid principal balance of loans repurchased	1,307	524
Reserve for loans repurchases	$ 180	180
Minimum [Member]
Commitments and Contingencies Disclosure [Line Items]
Lease expiration period	7 months
Lease expiration period, renewal option	9 months
Maximum [Member]
Commitments and Contingencies Disclosure [Line Items]
Lease expiration period	23 years
Lease expiration period, renewal option	5 years
Commitments to extend credit on standby letters of credit [Member] | Commitments to Extend Credit [Member]
Commitments and Contingencies Disclosure [Line Items]
Contract Amount	$ 6,666	$ 6,250

Commitments and Contingencie126

Commitments and Contingencies (Financial Instruments with Off Balance Sheet Risk) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Interest rate lock commitments [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Notional amount	$ 45,139	$ 49,502
Commitments to sell mortgage loans [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Notional amount	71,539	78,896
Interest rate swaps with customers [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Notional amount	545,049	428,723
Mirror swaps with counterparties [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Notional amount	545,049	428,723
Risk participation-in agreement [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Notional amount	34,052	28,460
Foreign exchange contract [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Notional amount	3,005	0
Interest rate swaps [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Notional amount	60,000	60,000
Commitments to Extend Credit [Member] | Commitments to extend credit on commerical loans [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Contract Amount	537,310	430,710
Commitments to Extend Credit [Member] | Commitments to extend credit on home equity lines [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Contract Amount	254,855	232,375
Commitments to Extend Credit [Member] | Commitments to extend credit on other loans [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Contract Amount	48,819	49,708
Commitments to Extend Credit [Member] | Commitments to extend credit on standby letters of credit [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Contract Amount	$ 6,666	$ 6,250

Commitments and Contingencie127

Commitments and Contingencies (Schedule of Future Minimum Operating Lease Payments) (Details) $ in Thousands	Dec. 31, 2017USD ($)
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Future Minimum Payments, Next Twelve Months	$ 3,518
Future Minimum Payments, Year Two	3,542
Future Minimum Payments, Year Three	2,863
Future Minimum Payments, Year Four	2,530
Future Minimum Payments, Year Five	2,158
Future Minimum Payments, Thereafter	24,652
Total minimum lease payments	$ 39,263

Parent Company Financial Sta128

Parent Company Financial Statements (Balance Sheet) (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Assets:
Other assets	$ 63,740	$ 62,484
Total assets	4,529,850	4,381,115	$ 3,771,604
Liabilities:
Junior subordinated debentures	22,681	22,681
Contingent consideration liability	1,404	2,047	2,945
Other liabilities	59,822	54,948
Total liabilities	4,116,566	3,990,311
Shareholders’ Equity:
Common stock of $.0625 par value; authorized 60,000,000 shares; issued and outstanding 17,226,508 shares in 2017 and 17,170,820 shares in 2016	1,077	1,073
Paid-in capital	117,961	115,123
Retained earnings	317,756	294,365
Accumulated other comprehensive loss	(23,510)	(19,757)
Total shareholders’ equity	413,284	390,804	$ 375,388	$ 346,279
Total liabilities and shareholders’ equity	$ 4,529,850	$ 4,381,115
Common stock, par value (in dollars per share)	$ 0.0625	$ 0.0625
Common stock, shares authorized (in shares)	60,000,000	60,000,000
Common stock, shares issued (in shares)	17,226,508	17,170,820
Common stock, shares outstanding (in shares)	17,226,508	17,170,820
Parent Company [Member]
Assets:
Cash on deposit with bank subsidiary	$ 1,664	$ 1,743
Investment in subsidiaries at equity value	434,831	413,613
Dividends receivable from subsidiaries	7,770	6,518
Other assets	259	332
Total assets	444,524	422,206
Liabilities:
Junior subordinated debentures	22,681	22,681
Dividends payable	7,087	6,628
Contingent consideration liability	1,404	2,047
Other liabilities	68	46
Total liabilities	31,240	31,402
Shareholders’ Equity:
Common stock of $.0625 par value; authorized 60,000,000 shares; issued and outstanding 17,226,508 shares in 2017 and 17,170,820 shares in 2016	1,077	1,073
Paid-in capital	117,961	115,123
Retained earnings	317,756	294,365
Accumulated other comprehensive loss	(23,510)	(19,757)
Total shareholders’ equity	413,284	390,804
Total liabilities and shareholders’ equity	$ 444,524	$ 422,206

Parent Company Financial Sta129

Parent Company Financial Statements (Statement of Income) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Expenses:
Interest on junior subordinated debentures									$ 613	$ 491	$ 871
Legal and professional fees									2,294	2,579	2,741
Acquisition related expenses									0	0	989
Change in fair value of contingent consideration									(643)	(898)	41
Income before income taxes	$ 21,145	$ 19,288	$ 19,704	$ 17,503	$ 18,035	$ 18,190	$ 16,210	$ 16,419	77,640	68,854	64,343
Income tax benefit (expense)	(13,163)	(6,326)	(6,505)	(5,721)	(5,873)	(5,863)	(5,153)	(5,484)	(31,715)	(22,373)	(20,878)
Net income	$ 7,982	$ 12,962	$ 13,199	$ 11,782	$ 12,162	$ 12,327	$ 11,057	$ 10,935	45,925	46,481	43,465
Parent Company [Member]
Income:
Dividends from subsidiaries									27,900	24,542	23,399
Other income									18	15	13
Total income									27,918	24,557	23,412
Expenses:
Interest on junior subordinated debentures									613	491	871
Legal and professional fees									169	98	134
Acquisition related expenses									0	0	308
Change in fair value of contingent consideration									(643)	(898)	41
Other									298	282	254
Total expenses									437	(27)	1,608
Income before income taxes									27,481	24,584	21,804
Income tax benefit (expense)									340	(15)	557
Income before equity in undistributed earnings of subsidiaries									27,821	24,569	22,361
Equity in undistributed earnings of subsidiaries									18,104	21,912	21,104
Net income									$ 45,925	$ 46,481	$ 43,465

Parent Company Financial Sta130

Parent Company Financial Statements (Statements of Cash Flows) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net income	$ 7,982	$ 12,962	$ 13,199	$ 11,782	$ 12,162	$ 12,327	$ 11,057	$ 10,935	$ 45,925	$ 46,481	$ 43,465
Adjustments to reconcile net income to net cash provided by operating activities:
(Increase) decrease in other assets									8,794	(984)	4,165
Change in fair value of contingent consideration									(643)	(898)	41
Tax benefit from stock option exercises and other equity instruments									508	1,016	694
Net cash provided by operating activities									59,385	59,749	52,260
Cash flows from investing activities:
Cash used in business combination, net of cash acquired									0	0	(1,671)
Net cash used in investing activities									(179,706)	(625,377)	(165,885)
Cash flows from financing activities:
Proceeds from stock option exercises and issuance of other equity instruments									366	977	1,563
Cash dividends paid									(26,300)	(24,637)	(22,770)
Net cash provided by financing activities									95,447	575,794	130,906
Net (decrease) increase in cash and cash equivalents									(24,874)	10,166	17,281
Cash and cash equivalents at beginning of year				107,797				97,631	107,797	97,631	80,350
Cash and cash equivalents at end of year	82,923				107,797				82,923	107,797	97,631
Parent Company [Member]
Cash flows from operating activities:
Net income									45,925	46,481	43,465
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed earnings of subsidiary									(18,104)	(21,912)	(21,104)
(Increase) decrease in dividend receivable									(1,252)	(1,436)	19
(Increase) decrease in other assets									72	45	(67)
Increase (decrease) in accrued expenses and other liabilities									22	(12)	2,425
Change in fair value of contingent consideration									(643)	(898)	41
Tax benefit from stock option exercises and other equity instruments									508	1,016	694
Other, net									(673)	(1,051)	(3,363)
Net cash provided by operating activities									25,855	22,233	22,110
Cash flows from investing activities:
Cash used in business combination, net of cash acquired									0	0	(1,671)
Net cash used in investing activities									0	0	(1,671)
Cash flows from financing activities:
Proceeds from stock option exercises and issuance of other equity instruments									366	978	1,563
Cash dividends paid									(26,300)	(24,637)	(22,770)
Net cash provided by financing activities									(25,934)	(23,659)	(21,207)
Net (decrease) increase in cash and cash equivalents									(79)	(1,426)	(768)
Cash and cash equivalents at beginning of year				$ 1,743				$ 3,169	1,743	3,169	3,937
Cash and cash equivalents at end of year	$ 1,664				$ 1,743				$ 1,664	$ 1,743	$ 3,169

Selected Quarterly Consolida131

Selected Quarterly Consolidated Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Interest and dividend income	$ 38,900	$ 37,869	$ 37,153	$ 35,664	$ 35,055	$ 33,256	$ 32,190	$ 32,969	$ 149,586	$ 133,470	$ 125,750
Interest expense	8,011	7,810	7,249	6,985	6,467	5,877	5,414	5,234	30,055	22,992	21,768
Net interest income	30,889	30,059	29,904	28,679	28,588	27,379	26,776	27,735	119,531	110,478	103,982
Provision for loan losses	200	1,300	700	400	2,900	1,800	450	500	2,600	5,650	1,050
Net interest income after provision for loan losses	30,689	28,759	29,204	28,279	25,688	25,579	26,326	27,235	116,931	104,828	102,932
Noninterest income	16,210	17,283	16,806	14,510	17,320	17,261	15,914	14,634	64,809	65,129	58,340
Noninterest expense	25,754	26,754	26,306	25,286	24,973	24,650	26,030	25,450	104,100	101,103	96,929
Income before income taxes	21,145	19,288	19,704	17,503	18,035	18,190	16,210	16,419	77,640	68,854	64,343
Income tax expense	13,163	6,326	6,505	5,721	5,873	5,863	5,153	5,484	31,715	22,373	20,878
Net income	$ 7,982	$ 12,962	$ 13,199	$ 11,782	$ 12,162	$ 12,327	$ 11,057	$ 10,935	$ 45,925	$ 46,481	$ 43,465
Weighted average common shares outstanding - basic	17,223	17,212	17,206	17,186	17,142	17,090	17,067	17,023	17,207	17,081	16,879
Weighted average common shares outstanding - diluted	17,349	17,318	17,316	17,293	17,245	17,203	17,194	17,157	17,338	17,208	17,067
Basic earnings per common share (in dollars per share)	$ 0.46	$ 0.75	$ 0.77	$ 0.68	$ 0.71	$ 0.72	$ 0.65	$ 0.64	$ 2.66	$ 2.72	$ 2.57
Diluted earnings per common share (in dollars per share)	0.46	0.75	0.76	0.68	0.70	0.72	0.64	0.64	2.64	2.70	2.54
Cash dividends declared per share (in dollars per share)	$ 0.39	$ 0.39	$ 0.38	$ 0.38	$ 0.37	$ 0.37	$ 0.36	$ 0.36	$ 1.54	$ 1.46	$ 1.36