United Bankshares (UBSI) 10-K 1 Mar 17 2016 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2016	Jan. 31, 2017	Jun. 30, 2016
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	FY
Trading Symbol	UBSI
Entity Registrant Name	UNITED BANKSHARES INC/WV
Entity Central Index Key	729,986
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		81,045,880
Entity Public Float			$ 2,666,578,998

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Assets
Cash and due from banks	$ 175,468	$ 136,690
Interest-bearing deposits with other banks	1,258,334	719,923
Federal funds sold	725	722
Total cash and cash equivalents	1,434,527	857,335
Securities available for sale at estimated fair value (amortized cost-$1,277,639 at December 31, 2016 and $1,072,340 at December 31, 2015)	1,259,214	1,066,334
Securities held to maturity (estimated fair value-$31,178 at December 31, 2016 and $36,319 at December 31, 2015)	33,258	39,099
Other investment securities	111,166	98,749
Loans held for sale	8,445	10,681
Loans	10,356,719	9,398,952
Less: Unearned income	(15,582)	(14,872)
Loans net of unearned income	10,341,137	9,384,080
Less: Allowance for loan losses	(72,771)	(75,726)
Net loans	10,268,366	9,308,354
Bank premises and equipment	75,909	73,089
Goodwill	863,767	710,252
Accrued interest receivable	39,400	35,801
Other assets	414,840	378,250
TOTAL ASSETS	14,508,892	12,577,944
Deposits:
Noninterest-bearing	3,171,841	2,699,958
Interest-bearing	7,625,026	6,641,569
Total deposits	10,796,867	9,341,527
Borrowings:
Federal funds purchased	22,235	22,230
Securities sold under agreements to repurchase	237,316	341,661
Federal Home Loan Bank (FHLB) borrowings	897,707	850,880
Other long-term borrowings	224,319	223,506
Reserve for lending-related commitments	1,044	936
Accrued expenses and other liabilities	93,657	84,569
TOTAL LIABILITIES	12,273,145	10,865,309
Shareholders' Equity
Preferred stock, $1.00 par value; Authorized-50,000,000 shares; none issued	0	0
Common stock, $2.50 par value; Authorized-100,000,000 shares; issued- 81,068,252 and 69,626,932 at December 31, 2016 and 2015, respectively, including 28,278 and 23,835 shares in treasury at December 31, 2016 and 2015, respectively	202,671	174,067
Surplus	1,205,778	752,997
Retained earnings	872,990	824,603
Accumulated other comprehensive loss	(44,717)	(38,212)
Treasury stock, at cost	(975)	(820)
TOTAL SHAREHOLDERS' EQUITY	2,235,747	1,712,635
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY	$ 14,508,892	$ 12,577,944

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Securities available for sale, amortized cost	$ 1,277,639	$ 1,072,340
Securities held to maturity	$ 31,178	$ 36,319
Preferred stock, par value	$ 1	$ 1
Preferred stock, shares authorized	50,000,000	50,000,000
Preferred stock, shares issued	0	0
Common stock, par value	$ 2.50	$ 2.50
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	81,068,252	69,626,932
Common stock, shares in treasury	28,278	23,835

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Interest income
Interest and fees on loans	$ 430,738	$ 387,713	$ 383,662
Interest on federal funds sold and other short-term investments	3,495	1,645	954
Interest and dividends on securities:
Taxable	32,357	30,744	30,426
Tax-exempt	3,751	3,528	3,500
Total interest income	470,341	423,630	418,542
Interest expense
Interest on deposits	29,125	28,023	27,461
Interest on short-term borrowings	1,584	834	1,134
Interest on long-term borrowings	14,301	10,649	14,239
Total interest expense	45,010	39,506	42,834
Net interest income	425,331	384,124	375,708
Provision for loan losses	24,509	22,574	21,937
Net interest income after provision for loan losses	400,822	361,550	353,771
Other income
Fees from trust and brokerage services	19,037	19,085	18,141
Fees from deposit services	32,858	37,962	42,372
Bankcard fees and merchant discounts	5,215	4,786	4,207
Other service charges, commissions, and fees	2,059	2,141	2,049
Income from bank-owned life insurance	5,794	5,557	5,300
Income from mortgage banking	3,450	2,507	1,876
Net gain on sale of bank premises	0	0	8,976
Other income	1,339	1,433	1,153
Total other-than-temporary impairment losses	339	(113)	1,935
Portion of loss recognized in other comprehensive income	(372)	66	(8,413)
Net other-than-temporary impairment losses	(33)	(47)	(6,478)
Net gains on sales/calls of investment securities	313	202	3,366
Net investment securities gains (losses)	280	155	(3,112)
Total other income	70,032	73,626	80,962
Other expense
Employee compensation	93,281	88,123	90,823
Employee benefits	28,965	27,086	20,457
Net occupancy expense	27,529	24,301	25,796
Other real estate owned (OREO) expense	5,844	3,613	7,740
Equipment expense	8,622	9,034	9,565
Data processing expense	15,280	14,867	14,455
Bankcard processing expense	1,742	1,505	1,391
FDIC insurance expense	8,548	8,367	7,565
Prepayment penalty on FHLB advance	0	0	1,971
Other expense	58,385	54,791	60,084
Total other expense	248,196	231,687	239,847
Income before income taxes	222,658	203,489	194,886
Income taxes	75,575	65,530	64,998
Net income	$ 147,083	$ 137,959	$ 129,888
Earnings per common share:
Basic	$ 2	$ 1.99	$ 1.93
Diluted	1.99	1.98	1.92
Dividends per common share	$ 1.32	$ 1.29	$ 1.28
Average outstanding shares:
Basic	73,531,992	69,334,849	67,404,254
Diluted	73,893,127	69,625,531	67,648,673

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ 39,106	$ 41,479	$ 31,792	$ 34,706	$ 33,476	$ 35,047	$ 34,809	$ 34,627	$ 147,083	$ 137,959	$ 129,888
Change in net unrealized (loss) gain on available-for-sale (AFS) securities, net of tax									(7,782)	(4,068)	24,788
Accretion of the net unrealized loss on the transfer of AFS securities to held-to-maturity (HTM) securities, net of tax									6	5	5
Change in defined benefit pension plan, net of tax									1,271	1,615	(17,510)
Comprehensive income, net of tax									$ 140,578	$ 135,511	$ 137,171

Consolidated Statement of Chang

Consolidated Statement of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Virginia Commerce Merger [Member]	Bank of Georgetown [Member]	Deferred Compensation Plan [Member]	Common Stock [Member]	Common Stock [Member]Virginia Commerce Merger [Member]	Common Stock [Member]Bank of Georgetown [Member]	Common Stock [Member]Deferred Compensation Plan [Member]	Surplus [Member]	Surplus [Member]Virginia Commerce Merger [Member]	Surplus [Member]Bank of Georgetown [Member]	Surplus [Member]Deferred Compensation Plan [Member]	Retained Earnings [Member]	Retained Earnings [Member]Virginia Commerce Merger [Member]	Retained Earnings [Member]Bank of Georgetown [Member]	Retained Earnings [Member]Deferred Compensation Plan [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Other Comprehensive Income (Loss) [Member]Virginia Commerce Merger [Member]	Accumulated Other Comprehensive Income (Loss) [Member]Bank of Georgetown [Member]	Accumulated Other Comprehensive Income (Loss) [Member]Deferred Compensation Plan [Member]	Treasury Stock [Member]	Treasury Stock [Member]Virginia Commerce Merger [Member]	Treasury Stock [Member]Bank of Georgetown [Member]	Treasury Stock [Member]Deferred Compensation Plan [Member]
Balance at January 1, 2016 at Dec. 31, 2013	$ 1,041,732				$ 127,169				$ 237,674				$ 734,945				$ (43,047)				$ (15,009)
Beginning Balance, shares at Dec. 31, 2013					50,867,630
Net income	129,888				$ 0				0				129,888				0				0
Other comprehensive income, net of tax	7,283				0				0				0				7,283				0
Total comprehensive income, net of tax	137,171
Stock based compensation expense	2,195				0				2,195				0				0				0
Acquisition, Values		$ 552,262				$ 45,826				$ 506,436				$ 0				$ 0				$ 0
Acquisition, Shares						18,330,347
Purchase of treasury stock	(25)				0				0				0				0				(25)
Distribution of treasury stock for deferred compensation plan				$ 81				$ 0				$ 0				$ 0				$ 0				$ 81
Issuance of treasury stock (1,500 shares), shares								0																3,640
Cash dividends	(88,522)				0				0				(88,522)				0				0
Grant of restricted stock	0				0				(2,305)				0				0				2,305
Forfeiture of restricted stock	0				0				122				0				0				(122)
Common stock options exercised	$ 11,266				$ 291				(1,162)				0				0				12,137
Common stock options exercised, shares	468,933				116,430
Balance at December 31, 2016 at Dec. 31, 2014	$ 1,656,160				$ 173,286				742,960				776,311				(35,764)				(633)
Ending Balance, shares at Dec. 31, 2014					69,314,407
Net income	137,959				$ 0				0				137,959				0				0
Other comprehensive income, net of tax	(2,448)				0				0				0				(2,448)				0
Total comprehensive income, net of tax	135,511
Stock based compensation expense	2,484				0				2,484				0				0				0
Purchase of treasury stock	(1)				0				0				0				0				(1)
Distribution of treasury stock for deferred compensation plan				1				$ 0				0				0				0				$ 1
Issuance of treasury stock (1,500 shares), shares								0																24
Cash dividends	(89,667)				0				0				(89,667)				0				0
Grant of restricted stock	0				132				(132)				0				0				0
Forfeiture of restricted stock	0				0				187				0				0				(187)
Common stock options exercised	$ 8,147				$ 649				7,498				0				0				0
Common stock options exercised, shares	259,454				259,454
Balance at December 31, 2016 at Dec. 31, 2015	$ 1,712,635				$ 174,067				752,997				824,603				(38,212)				(820)
Ending Balance, shares at Dec. 31, 2015					69,626,932
Net income	147,083				$ 0				0				147,083				0				0
Other comprehensive income, net of tax	(6,505)				0				0				0				(6,505)				0
Total comprehensive income, net of tax	140,578
Stock based compensation expense	2,817				0				2,817				0				0				0
Issuance of common stock (4,330,000 shares)	199,916				$ 10,825				189,091				0				0				0
Issuance of common stock (4,330,000 shares), shares					4,330,000
Acquisition, Values			$ 264,495				$ 16,319				$ 248,176				$ 0				$ 0				$ 0
Acquisition, Shares							6,527,746
Purchase of treasury stock	(1)				$ 0				0				0				0				(1)
Distribution of treasury stock for deferred compensation plan	52			$ 1	$ 0			$ 0	0			$ 0	0			$ 0	0			$ 0	$ 52			$ 1
Issuance of treasury stock (1,500 shares), shares					0			0													1,500			28
Cash dividends	(98,696)				$ 0				0				(98,696)				0				$ 0
Grant of restricted stock	0				161				(161)				0				0				0
Forfeiture of restricted stock	0				0				207				0				0				(207)
Common stock options exercised	$ 13,950				$ 1,299				12,651				0				0				0
Common stock options exercised, shares	519,482				519,482
Balance at December 31, 2016 at Dec. 31, 2016	$ 2,235,747				$ 202,671				$ 1,205,778				$ 872,990				$ (44,717)				$ (975)
Ending Balance, shares at Dec. 31, 2016					81,068,252

Consolidated Statement of Chan7

Consolidated Statement of Changes in Shareholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash dividends per share	$ 1.32	$ 1.29	$ 1.28
Common stock options exercised, shares	519,482	259,454	468,933
Common Stock [Member]
Issuance of common stock, shares	4,330,000
Purchase of treasury stock, shares	0	0	0
Distribution of treasury stock for deferred compensation plan, shares	0
Cash dividends per share	$ 0
Grant of restricted stock, shares	64,092	53,071	66,949
Forfeiture of restricted stock, shares	5,955	5,294	3,528
Common stock options exercised, shares	519,482	259,454	116,430
Treasury Stock [Member]
Purchase of treasury stock, shares	16	17	749
Distribution of treasury stock for deferred compensation plan, shares	1,500
Virginia Commerce Merger [Member] | Common Stock [Member]
Acquisition, Shares			18,330,347
Bank of Georgetown [Member] | Common Stock [Member]
Acquisition, Shares	6,527,746
Deferred Compensation Plan [Member] | Common Stock [Member]
Distribution of treasury stock for deferred compensation plan, shares	0	0	0
Deferred Compensation Plan [Member] | Treasury Stock [Member]
Distribution of treasury stock for deferred compensation plan, shares	28	24	3,640

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
OPERATING ACTIVITIES
Net income	$ 147,083	$ 137,959	$ 129,888
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for loan losses	24,509	22,574	21,937
Depreciation, amortization and accretion	(8,720)	746	1,574
Loss (gain) on sales of bank premises, OREO and equipment	5,196	2,059	(3,195)
(Gain) loss on securities	(280)	(155)	3,112
Loans originated for sale	(154,335)	(145,836)	(96,437)
Proceeds from sales of loans	160,021	146,342	93,869
Gain on sales of loans	(3,450)	(2,507)	(1,876)
Stock-based compensation	2,817	2,484	2,195
Excess tax benefits from stock-based compensation arrangements	(4,008)	(1,023)	(73)
Deferred income tax expense	7,252	1,729	10,097
Increase in cash surrender value of bank-owned life insurance policies	(3,837)	(5,557)	(3,375)
Amortization of net periodic pension costs	5,156	4,380	432
Changes in:
Interest receivable	(755)	(3,467)	1,708
Other assets	(5,855)	15,372	(2,901)
Accrued expenses and other liabilities	(4,068)	(1,222)	(4,387)
NET CASH PROVIDED BY OPERATING ACTIVITIES	166,726	173,878	152,568
INVESTING ACTIVITIES
Proceeds from maturities and calls of held to maturity securities	5,730	1,056	1,518
Purchases of held to maturity securities	0	(1,000)	0
Proceeds from sales of securities available for sale	103,440	7,316	94,249
Proceeds from maturities and calls of securities available for sale	410,550	183,950	440,240
Purchases of securities available for sale	(504,978)	(85,249)	(445,477)
Redemption of bank-owned life insurance policies	630	1,974	8,930
Purchases of bank premises and equipment	(7,271)	(5,263)	(8,876)
Proceeds from sales of bank premises and equipment	554	866	11,430
Acquisition of subsidiaries, net of cash paid	29,330	0	97,296
Proceeds from sales and redemptions of other investment securities	64,411	19,845	52,804
Purchases of other investment securities	(72,052)	(22,181)	(61,275)
Proceeds from sales of OREO properties	17,871	10,270	13,102
Net change in loans	(17,255)	(296,882)	(416,523)
NET CASH PROVIDED BY (USED IN) INVESTING ACTIVITIES	30,960	(185,298)	(212,582)
FINANCING ACTIVITIES
Cash dividends paid	(96,351)	(88,864)	(82,496)
Excess tax benefits from stock-based compensation arrangements	4,008	1,023	73
Acquisition of treasury stock	(1)	(1)	(2)
Proceeds from exercise of stock options	13,337	7,871	9,878
Proceeds from the issuance of common stock	199,916	0	0
Distribution of treasury stock for deferred compensation plan	1	1	81
Repayment of long-term Federal Home Loan Bank borrowings	(725,673)	(794,455)	(436,734)
Proceeds of long-term Federal Home Loan Bank borrowings	795,000	705,000	790,000
Redemption of issued trust preferred securities	0	0	(28,676)
Changes in:
Time deposits	75,639	(135,674)	262,989
Other deposits	408,127	433,414	140,266
Federal funds purchased, securities sold under agreements to repurchase and other short-term borrowings	(294,497)	(12,624)	(258,918)
NET CASH PROVIDED BY (USED IN) FINANCING ACTIVITIES	379,506	115,691	396,461
INCREASE IN CASH AND CASH EQUIVALENTS	577,192	104,271	336,447
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR	857,335	753,064	416,617
CASH AND CASH EQUIVALENTS AT END OF YEAR	1,434,527	857,335	753,064
Supplemental information
Cash paid for interest	44,609	39,835	42,012
Cash paid for income taxes	61,905	52,319	60,431
Noncash investing activities:
Transfers of loans to OREO	$ 21,776	$ 5,857	$ 20,885

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	NOTE A—SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Nature of Operations: Operating Segments: Basis of Presentation: At the close of business on June 3, 2016, United acquired Bank of Georgetown, a privately held community bank headquartered in Washington, D. C. The transaction was accounted for using the acquisition method and their results of operations have been included in the United’s consolidated financial statements as of the acquisition date. United determines whether it has a controlling financial interest in an entity by first evaluating whether the entity is a voting interest entity or a variable interest entity (VIE) under U.S. generally accepted accounting principles. Voting interest entities are entities in which the total equity investment at risk is sufficient to enable the entity to finance itself independently and provides the equity holders with the obligation to absorb losses, the right to receive residual returns and the right to make decisions about the entity’s activities. United consolidates voting interest entities in which it has all, or at least a majority of, the voting interest. As defined in applicable accounting standards, VIEs are entities that lack one or more of the characteristics of a voting interest entity. A controlling financial interest in a VIE is present when an enterprise has both the power to direct the activities of the VIE that most significantly impact the VIE’s economic performance and an obligation to absorb losses or the right to receive benefits that could potentially be significant to the VIE. The enterprise with a controlling financial interest, known as the primary beneficiary, consolidates the VIE. United’s wholly owned and indirect wholly owned statutory trust subsidiaries are VIEs for which United is not the primary beneficiary. Accordingly, its accounts are not included in United’s consolidated financial statements. The accounting and reporting policies of United conform with U.S. generally accepted accounting principles. In preparing the consolidated financial statements, management is required to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from those estimates. To conform to the 2016 presentation, certain reclassifications have been made to prior period amounts, which had no impact on net income, comprehensive income or shareholders’ equity. In the opinion of management, all adjustments necessary for a fair presentation of financial position and results of operations have been made. Such adjustments are of a normal and recurring nature. The Company has evaluated events and transactions subsequent to December 31, 2016 through the date these financial statements were issued. Based on definitions and requirements of generally accepted accounting principles for “Subsequent Events,” the Company has not identified any events that would require adjustments to, or disclosure in the financial statements. Cash and Cash Equivalents: Securities: Gains or losses on sales of securities are recognized by the specific identification method and are reported in securities gains and losses within noninterest income of the Consolidated Statements of Income. United reviews available-for-sale and held-to-maturity securities on a quarterly basis for possible impairment. United determines whether a decline in fair value below the amortized cost basis of a security is other-than-temporary. This determination requires significant judgment. In making this judgment, United’s review includes an analysis of the facts and circumstances of each individual investment such as the severity of loss, the length of time the fair value has been below cost, the expectation for that security’s performance, the creditworthiness of the issuer, recent changes in external credit ratings, and the assessment of collection of the security’s contractual amounts from the issuer or issuers. If United intends to sell, or it is more likely than not that United will be required to sell an impaired debt security before recovery of its amortized cost basis less any current period credit loss, other-than-temporary impairment is recognized in earnings. The credit loss is defined as the difference between the present value of cash flows expected to be collected (discounted at the contractual rate) and the amortized cost basis. The amount recognized in earnings is equal to the entire difference between the security’s amortized cost basis and its fair value at the balance sheet date. If United does not intend to sell, and it is not more likely than not that United will be required to sell the impaired debt security prior to recovery of its amortized cost basis less any current-period credit loss, the other-than-temporary impairment is separated into the following: 1) the amount representing the credit loss, which is recognized within noninterest income of the Consolidated Statements of Income, and 2) the amount related to all other factors, which is recognized in other comprehensive income within shareholders’ equity of the Consolidated Balance Sheets. For equity securities, United evaluates the near-term prospects of the investment in relation to the severity and duration of any impairment and United’s ability and intent to hold these equity securities until a recovery of their fair value to at least the cost basis of the investment. Equity securities that are deemed to be other-than-temporarily impaired are written down to the fair value with the write-down recognized within noninterest income of the Consolidated Statements of Income. Certain security investments that do not have readily determinable fair values and for which United does not exercise significant influence are carried at cost and are classified as other investment securities on the balance sheet. These cost-method investments are reviewed for impairment at least annually or sooner if events or changes in circumstances indicate the carrying value may not be recoverable. Securities Purchased Under Resale Agreements and Securities Sold Under Agreements to Repurchase: Loans: Loans are designated as impaired when, in the opinion of management, based on current information and events, the collection of principal and interest in accordance with the loan contract is doubtful. Consistent with United’s existing method of income recognition for loans, interest on impaired loans, except those classified as nonaccrual, is recognized as income using the accrual method. United’s method of income recognition for impaired loans that are classified as nonaccrual is to recognize interest income on the cash basis or apply the cash receipt to principal when the ultimate collectibility of principal is in doubt. A loan is categorized as restructured if a concession is granted to provide for a reduction of either interest or principal due to a deterioration in the financial condition of the borrower. A loan classified as restructured will generally retain such classification until the loan is paid in full. However, a restructured one-to-four-family residential mortgage loan that yields a market rate and demonstrates the ability to pay under the terms of the restructured note through a sustained period of repayment performance, which is generally one year, is removed from the restructured classification. Interest income on restructured loans is accrued at the reduced rate and the loan is returned to performing status once the borrower demonstrates the ability to pay under the terms of the restructured note through a sustained period of repayment performance, which is generally six months. The portfolio of restructured loans is monitored monthly. Loans Acquired Through Transfer: Loans Held for Sale: Allowance for Credit Losses: The allowance for loan losses is management’s estimate of the probable credit losses inherent in the loan portfolio. Management’s evaluation of the adequacy of the allowance for loan losses and the appropriate provision for credit losses is based upon a quarterly evaluation of the portfolio. This evaluation is inherently subjective and requires significant estimates, including the amounts and timing of estimated future cash flows, estimated losses on pools of loans based on historical loss experience, and consideration of current economic trends, all of which are susceptible to constant and significant change. The amounts allocated to specific credits and loan pools grouped by similar risk characteristics are reviewed on a quarterly basis and adjusted as necessary based upon subsequent changes in circumstances. In determining the components of the allowance for credit losses, management considers the risk arising in part from, but not limited to, charge-off and delinquency trends, current economic and business conditions, lending policies and procedures, the size and risk characteristics of the loan portfolio, concentrations of credit, and other various factors. Loans deemed to be uncollectible are charged against the allowance for loan losses, while recoveries of previously charged-off amounts are credited to the allowance for loan losses. In determining the adequacy of the allowance for loan losses, management makes allocations to specific commercial loans classified by management as to risk. Management determines the loan’s risk by considering the borrowers’ ability to repay, the collateral securing the credit and other borrower-specific factors that may impact collectibility. For impaired loans, specific allocations are based on the present value of expected future cash flows using the loan’s effective interest rate, or as a practical expedient, at the loan’s observable market price or the fair value of the collateral if the loan is collateral-dependent. Other commercial loans not specifically reviewed on an individual basis are evaluated based on loan pools, which are grouped by similar risk characteristics using management’s internal risk ratings. Allocations for these commercial loan pools are determined based upon historical loss experience adjusted for current environmental conditions and risk factors and the estimate period it takes for losses to result in a charge-off. Allocations for loans, other than commercial loans, are developed by applying historical loss experience adjusted for current environmental conditions and risk factors to loan pools grouped by similar risk characteristics. The environmental factors considered for each of the loan portfolios includes estimated probable inherent but undetected losses within the portfolio due to uncertainties in economic conditions, delays in obtaining information, including unfavorable information about a borrower’s financial condition, the difficulty in identifying triggering events that correlate perfectly to subsequent loss rates, and risk factors that have not yet fully manifested themselves in loss allocation factors. While allocations are made to specific loans and pools of loans, the allowance is available for all loan losses. Beginning in 2015, United’s methodology related to the allowance for loan losses was enhanced by estimating the loss emergence period. Management believes that the allowance for credit losses is adequate to provide for probable losses on existing loans and loan-related commitments based on information currently available. Bank Premises and Equipment: Other Real Estate Owned Advertising Costs: Income Taxes: For uncertain income tax positions, United records a liability based on a recognition threshold of more-likely-than-not, and a measurement attribute for all tax positions taken on a tax return, in order for those tax positions to be recognized in the financial statements. United files a consolidated income tax return with its subsidiaries. Federal income tax expense or benefit has been allocated to subsidiaries on a separate return basis. Intangible Assets: Goodwill is not amortized, but is tested for impairment at least annually or sooner if indicators of impairment exist. Intangible assets with definite useful lives (such as core deposit intangibles) are amortized over their respective estimated useful lives to their estimated residual values, and reviewed for impairment at least annually or as indicators of impairment are identified. Based on the most recent goodwill impairment test, no impairment was noted. As of December 31, 2016, and 2015, total goodwill approximated $863,767,000 and $710,252,000, respectively. Derivative Financial Instruments: Derivative instruments designated in a hedge relationship to mitigate exposure to changes in the fair value of an asset, liability, or firm commitment attributable to a particular risk, such as interest rate risk, are considered fair value hedges. Derivative instruments designated in a hedge relationship to mitigate exposure to variability in expected future cash flows, or other types of forecasted transactions, are considered cash flow hedges. For a fair value hedge, the fair value of the interest rate swap is recognized on the balance sheet as either a freestanding asset or liability with a corresponding adjustment to the hedged financial instrument. Subsequent adjustments due to changes in the fair value of a derivative that qualifies as a fair value hedge are offset in current period earnings. For a cash flow hedge, the fair value of the interest rate swap is recognized on the balance sheet as either a freestanding asset or liability with a corresponding adjustment to other comprehensive income within shareholders’ equity, net of tax. Subsequent adjustments due to changes in the fair value of a derivative that qualifies as a cash flow hedge are offset to other comprehensive income, net of tax. The portion of a hedge that is ineffective is recognized immediately in earnings. At inception of a hedge relationship, United formally documents the hedged item, the particular risk management objective, the nature of the risk being hedged, the derivative being used, how effectiveness of the hedge will be assessed and how the ineffectiveness of the hedge will be measured. United also assesses hedge effectiveness at inception and on an ongoing basis using regression analysis. Hedge ineffectiveness is measured by using the change in fair value method. The change in fair value method compares the change in the fair value of the hedging derivative to the change in the fair value of the hedged exposure, attributable to changes in the benchmark rate. For derivatives that are not designated in a hedge relationship, changes in the fair value of the derivatives are recognized in earnings in the same period as the change in the fair value. Stock-Based Compensation Stock-based compensation expense was $2,817,000 in 2016, $2,484,000 in 2015 and $2,195,000 in 2014. Treasury Stock Trust Assets and Income: Earnings Per Common Share: 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 during the applicable period, excluding outstanding participating securities. 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 stock compensation using the treasury stock method. The reconciliation of the numerator and denominator of basic earnings per share with that of diluted earnings per share is presented as follows: Year Ended December 31 (Dollars in thousands, except per share) 2016 2015 2014 Distributed earnings allocated to common stock $ 98,510 $ 89,497 $ 88,353 Undistributed earnings allocated to common stock 48,317 48,218 41,305 Net earnings allocated to common shareholders $ 146,827 $ 137,715 $ 129,658 Average common shares outstanding 73,531,992 69,334,849 67,404,254 Dilutive effect of stock compensation 361,135 290,682 244,419 Average diluted shares outstanding 73,893,127 69,625,531 67,648,673 Earnings per basic common share $ 2.00 $ 1.99 $ 1.93 Earnings per diluted common share $ 1.99 $ 1.98 $ 1.92 Fair Value Measurements The Fair Value Measurements and Disclosures topic specifies a hierarchy of valuation techniques based on whether the inputs to those valuation techniques are observable or unobservable. Observable inputs reflect market data obtained from independent sources, while unobservable inputs reflect United’s market assumptions. The three levels of the fair value hierarchy based on these two types of inputs are as follows: Level 1 - Valuation is based on quoted prices in active markets for identical assets and liabilities. Level 2 - Valuation is based on observable inputs including quoted prices in active markets for similar assets and liabilities, quoted prices for identical or similar assets and liabilities in less active markets, and model-based valuation techniques for which significant assumptions can be derived primarily from or corroborated by observable data in the market. Level 3 - Valuation is based on model-based techniques that use one or more significant inputs or assumptions that are unobservable in the market. When determining the fair value measurements for assets and liabilities, United looks to active and observable markets to price identical assets or liabilities whenever possible and classifies such items in Level 1. When identical assets and liabilities are not traded in active markets, United looks to market observable data for similar assets and liabilities and classifies such items as Level 2. Nevertheless, certain assets and liabilities are not actively traded in observable markets and United must use alternative valuation techniques using unobservable inputs to determine a fair value and classifies such items as Level 3. For assets and liabilities that are not actively traded, the fair value measurement is based primarily upon estimates that require significant judgment. Therefore, the results may not be realized in an actual sale or immediate settlement of the asset or liability. Additionally, there are inherent weaknesses in any calculation technique, and changes in the underlying assumptions used, including discount rates and estimates of future cash flows, could significantly affect the results of current or future values. The level within the fair value hierarchy is based on the lowest level of input that is significant in the fair value measurement. Recent Accounting Pronouncements In June 2016, the FASB issued ASU 2016-13, “Financial Instruments – Credit Losses.” ASU 2016-13 changes the impairment model for most financial assets and certain other instruments that aren’t measured at fair value through net income. The standard will replace today’s “incurred loss” approach with an “expected loss” model for instruments measured at amortized cost and require entities to record allowances for available-for-sale debt securities rather than reduce the carrying amount under the current other-than-temporary impairment (OTTI) model. ASU 2016-13 also simplifies the accounting model for purchased credit-impaired debt securities and loans. Entities will apply the standard’s provisions as a cumulative-effect adjustment to retained earnings as of the beginning of the first reporting period in which the guidance is effective. ASU 2016-13 is effective for United on January 1, 2020, with early adoption permitted, and management is currently evaluating the possible impact this standard may have on the Company’s financial condition or results of operations. In March 2016, the FASB issued ASU 2016-09, “Compensation-Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting.” ASU 2016-09 will change certain aspects of accounting for share-based payments to employees. The new guidance will, amongst other things, require all income tax effects of awards to be recognized in the income statement when the awards vest or are settled. It also will allow an employer to repurchase more of an employee’s shares than it can today for tax withholding purposes without triggering liability accounting and to make a policy election to account for forfeitures as they occur. United adopted ASU 2016-09 on January 1, 2017 utilizing the modified retrospective method. The Company will continue to estimate the number of awards expected to be forfeited and adjust the estimate when it is no longer probable that the employee will fulfill the service condition, as was previously required. ASU 2016-09 also requires that all income tax-related cash flows resulting from share-based payments be reported as operating activities in the statement of cash flows. Previously, income tax benefits at settlement of an award were reported as a reduction to operating cash flows and an increase to financing cash flows to the extent that those benefits exceeded the income tax benefits reported in earnings during the award’s vesting period. The Company plans to apply that change in cash flow classification on a retrospective basis. The recognition of excess tax benefits and deficiencies in the income statement was adopted prospectively. Based on the Company’s current stock valuation and estimated exercise activity associated with stock options, it anticipates an insignificant adjustment to income tax expense. The adoption of ASU 2016-09 did not have a material impact on the Company’s financial condition or results of operations. In February 2016, the FASB issued ASU 2016-02, “Leases (Topic 842)”. ASU 2016-02 includes a lessee accounting model that recognizes two types of leases, finance leases and operating leases, while lessor accounting will remain largely unchanged from the current GAAP. ASU 2016-02 requires, amongst other things, that a lessee recognize on the balance sheet a right-of-use asset and a lease liability for leases with terms of more than twelve months. 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 is effective for United on January 1, 2019 and management is currently evaluating the possible impact this standard may have on the Company’s financial condition or results of operations. In January 2016, the FASB issued ASU 2016-01, “Financial Instruments Overall: Recognition and Measurement of Financial Assets and Financial Liabilities.” ASU 2016-01 makes changes to the classification and measurement of investments in equity securities, the presentation of certain fair value changes for financial liabilities measured at fair value under the fair value option and disclosure of fair value of instruments. In addition, ASU 2016-01 clarifies guidance related to the valuation allowance assessment when recognizing deferred tax assets resulting from unrealized losses on available-for-sale debt securities. ASU 2016-01 is effective for United on January 1, 2018 and is not expected to have a significant impact on the Company’s financial condition or results of operations. In May 2014, the FASB issued ASU 2014-09, “Revenue from Contracts with Customers (Topic 606).” ASU 2014-09 supersedes the revenue recognition requirements in ASC topic 605, “Revenue Recognition,” and most industry-specific guidance throughout the ASC. The amendments require an entity to recognize revenue upon the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods and services. The new revenue recognition standard sets forth a five step principle-based approach for determining revenue recognition. ASU 2014-09 now will be effective for United on January 1, 2018 with early adoption permitted on January 1, 2017. The Company intends to adopt the amendments of ASU 2014-09 beginning January 1, 2018 through the modified-retrospective transition method with a cumulative effect adjustment to opening retained earnings. The Company’s revenue is comprised of net interest income and noninterest income. As the standard does not apply to revenue associated with financial instruments, net interest income and gains and losses from securities are not impacted by the standard. Our implementation efforts to date include identification of revenue streams within the scope of the guidance and analyzing those revenue streams to determine the impact of the standard. We are in the process of evaluating revenue contracts for the impact the new recognition methods will have on revenue recognition. Based on this review, ASU 2014-09 may require the Company to change how it recognizes certain recurring revenue streams related to noninterest income including fees from trust and brokerage services. Although we do not expect this standard to have a material impact on the timing or amount of revenue, we are still assessing the potential impact on the Company’s consolidated financial statements.

Mergers and Acquisitions

Mergers and Acquisitions	12 Months Ended
	Dec. 31, 2016
Business Combinations [Abstract]
Mergers and Acquisitions	NOTE B—MERGERS AND ACQUISITIONS Cardinal Financial Corporation On August 17, 2016, United entered into an Agreement and Plan of Reorganization (the Agreement) with Cardinal Financial Corporation (Cardinal), a Virginia corporation headquartered in Tysons Corner, Virginia. In accordance with the Agreement, Cardinal will merge with and into a wholly-owned subsidiary of United (the Merger). At the effective time of the Merger, Cardinal will cease to exist and the wholly-owned subsidiary of United shall survive and continue to exist as a Virginia corporation. The Agreement provides that at the effective time of the Merger, each outstanding share of common stock of Cardinal will be converted into the right to receive 0.71 shares of United common stock, par value $2.50 per share, plus cash in lieu of fractional shares. Pursuant to the Agreement, at the effective time of the Merger, shares of Cardinal restricted stock that were unvested prior to the Merger will vest upon the Merger under the terms of the restricted stock agreements and convert into the right to receive 0.71 shares of United common stock, plus cash in lieu of fractional shares. Also under the terms of the merger agreement, outstanding Cardinal stock options, whether vested or not, will convert into fully vested and exercisable stock options with respect to shares of United’s common stock, with appropriate adjustments to reflect the exchange ratio. After the effective time of the Merger, Cardinal Bank, a wholly-owned subsidiary of Cardinal, will merge with and into United Bank, a wholly-owned indirect subsidiary of United (the Bank Merger). United Bank will survive the Bank Merger and continue to exist as a Virginia banking corporation. The acquisition of Cardinal will afford United the opportunity to expand its existing footprint in the Washington, D.C. Metropolitan Statistical Area. As of December 31, 2016, Cardinal had $4,210,514,000 in assets with 30 banking offices throughout the Washington D.C. Metropolitan region. Cardinal also operates George Mason Mortgage, LLC, a residential mortgage lending company based in Fairfax, Virginia with offices located in Virginia, Maryland and the District of Columbia; and Cardinal Wealth Services Inc. Bank of Georgetown After the close of business on June 3, 2016 (Acquisition Date), United acquired 100% of the outstanding common stock of Bank of Georgetown, a privately held community bank headquartered in Washington, D.C. With this transaction, United continues to expand its existing footprint in the D.C. Metro Region. The results of operations of Bank of Georgetown are included in the consolidated results of operations from the Acquisition Date. At consummation, Bank of Georgetown had assets of $1,278,837,000, loans of $999,773,000, and deposits of $971,369,000. The transaction was accounted for under the acquisition method of accounting and accordingly, assets acquired, liabilities assumed and consideration exchanged were recorded at estimated fair value on the Acquisition Date. The aggregate purchase price was approximately $264,505,000, including common stock valued at $253,799,000, stock options assumed valued at $10,696,000, and cash paid for fractional shares of $10,000. The number of shares issued in the transaction was 6,527,746, which were valued based on the closing market price of $38.88 for United’s common shares on June 3, 2016. The preliminary purchase price has been allocated to the identifiable tangible and intangible assets resulting in preliminary additions to goodwill and core deposit intangibles of $152,845,000 and $9,058,000, respectively. The core deposit intangibles are expected to be amortized over ten years. Because the consideration paid was greater than the net fair value of the acquired assets and liabilities, the Company recorded goodwill as part of the acquisition. None of the goodwill from the Bank of Georgetown acquisition is expected to be deductible for tax purposes. United used an independent third party to help determine the fair values of the assets and liabilities acquired from the Bank of Georgetown. As a result of the merger, United recorded downward fair value adjustments of $41,745,000 on the loans acquired and $1,550,000 on leasehold improvements, respectively, a premium on interest-bearing deposits acquired of $316,000 and a premium on long-term FHLB advances of $2,659,000. The remaining discount and premium amounts are being amortized or accreted on an accelerated basis over each asset’s or liability’s estimated remaining life at the time of acquisition. At December 31, 2016, the premium on the interest-bearing deposits and the FHLB advances had an estimated remaining life of 1.08 years and 8.67 years, respectively. United assumed approximately $300,000 of liabilities to provide severance benefits to terminated employees of Bank of Georgetown, which has no remaining balance as of December 31, 2016. The estimated fair values of the acquired assets and assumed liabilities, including identifiable intangible assets are preliminary as of December 31, 2016 and are subject to refinement as additional information relative to closing date fair values becomes available. Any subsequent adjustments to the fair values of acquired assets and liabilities assumed, identifiable intangible assets, or other purchase accounting adjustments will result in adjustments to goodwill within the first 12 months following the date of acquisition. In many cases, determining the estimated fair value of the acquired assets and assumed liabilities required United to estimate cash flows expected to result from those assets and liabilities and to discount those cash flows at appropriate rates of interest. The most significant of those determinations related to the fair valuation of acquired loans. The fair value of the acquired loans was based on the present value of the expected cash flows. Periodic principal and interest cash flows were adjusted for expected losses and prepayments, then discounted to determine the present value and summed to arrive at the estimated fair value. For such loans, the excess of cash flows expected at acquisition over the estimated fair value is recognized as interest income over the remaining lives of the loans. The difference between contractually required payments at acquisition and the cash flows expected to be collected at acquisition reflects the impact of estimated credit losses and other factors, such as prepayments. In accordance with GAAP, there was no carry-over of Bank of Georgetown’s previously established allowance for loan losses. The acquired loans were divided into loans with evidence of credit quality deterioration, which are accounted for under ASC topic 310-30 (acquired impaired) and loans that do not meet this criteria, which are accounted for under ASC topic 310-20 (acquired performing). Acquired impaired loans have experienced a deterioration of credit quality from origination to acquisition for which it is probable that United will be unable to collect all contractually required payments receivable, including both principal and interest. Subsequent decreases in the expected cash flows require United to evaluate the need for additions to the Company’s allowance for credit losses. Subsequent improvements in expected cash flows generally result in the recognition of additional interest income over the then remaining lives of the loans. In conjunction with the Bank of Georgetown merger, the acquired loan portfolio was accounted for at fair value as follows: (Dollars in thousands) June 3, 2016 Contractually required principal and interest at acquisition $ 1,275,398 Contractual cash flows not expected to be collected (33,713 ) Expected cash flows at acquisition 1,241,685 Interest component of expected cash flows (273,488 ) Basis in acquired loans at acquisition – estimated fair value $ 968,197 Included in the above table is information related to acquired impaired loans. Specifically, contractually required principal and interest, cash flows expected to be collected and estimated fair value of acquired impaired loans were $138,125,000, $117,564,000, and $95,570,000, respectively. The consideration paid for Bank of Georgetown’s common equity and the expected fair value of acquired identifiable assets and liabilities assumed as of the Acquisition Date were as follows: (Dollars in thousands) Purchase price: Value of common shares issued (6,527,746 shares) $ 253,799 Fair value of stock options assumed 10,696 Cash for fractional shares 10 Total purchase price 264,505 Identifiable assets: Cash and cash equivalents 29,340 Investment securities 219,783 Loans 968,197 Premises and equipment 5,574 Core deposit intangibles 9,058 Other assets 31,605 Total identifiable assets $ 1,263,557 Identifiable liabilities: Deposits $ 971,685 Short-term borrowings 101,021 Long-term borrowings 67,659 Other liabilities 11,532 Total identifiable liabilities 1,151,897 Preliminary fair value of net assets acquired including identifiable intangible assets 111,660 Preliminary resulting goodwill $ 152,845 The operating results of United for the year ended December 31, 2016 include operating results of acquired assets and assumed liabilities subsequent to the Acquisition Date. The operations of United’s metropolitan Washington D.C. geographic area, which primarily includes the acquired operations of Bank of Georgetown, provided $122,545,000 in total revenues, which represents net interest income plus other income, and $61,253,000 in net income from the period from the Acquisition Date to December 31, 2016. These amounts are included in United’s consolidated financial statements as of and for the year ended December 31, 2016. Bank of Georgetown’s results of operations prior to the Acquisition Date are not included in United’s consolidated financial statements. The following table presents certain unaudited pro forma information for the results of operations for the year ended December 31, 2016 and 2015, as if the Bank of Georgetown merger had occurred on January 1, 2016 and 2015, respectively. These results combine the historical results of Bank of Georgetown into United’s consolidated statement of income and, while certain adjustments were made for the estimated impact of certain fair value adjustments and other acquisition-related activity including merger-related expenses of $5,406,000 for the year of 2016, they are not indicative of what would have occurred had the acquisition taken place on the indicated date nor are they intended to represent or be indicative of future results of operations. In particular, no adjustments have been made to eliminate the amount of Bank of Georgetown’s provision for credit losses for 2016 and 2015 that may not have been necessary had the acquired loans been recorded at fair value as of the beginning of 2016 and 2015. Additionally, United expects to achieve operating cost savings and other business synergies as a result of the acquisition which are not reflected in the pro forma amounts. Proforma Year Ended December 31 (Dollars in thousands) 2016 2015 Total Revenues (1) $ 519,011 $ 509,312 Net Income 148,226 150,910 (1) Represents net interest income plus other income

Investment Securities

Investment Securities	12 Months Ended
	Dec. 31, 2016
Investments, Debt and Equity Securities [Abstract]
Investment Securities	NOTE C—INVESTMENT SECURITIES The following is a summary of the amortized cost and estimated fair values of securities available for sale. December 31, 2016 (In thousands) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Cumulative OTTI in AOCI (1) U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 95,247 $ 698 $ 159 $ 95,786 $ 0 State and political subdivisions 196,350 1,364 4,902 192,812 0 Residential mortgage-backed securities Agency 585,208 3,999 5,111 584,096 0 Non-agency 6,629 426 12 7,043 86 Commercial mortgage-backed securities Agency 304,635 1,948 1,242 305,341 0 Asset-backed securities 217 0 0 217 0 Trust preferred collateralized debt obligations 48,558 729 15,735 33,552 25,952 Single issue trust preferred securities 13,363 284 2,170 11,477 0 Other corporate securities 14,996 66 0 15,062 0 Marketable equity securities 12,436 1,398 6 13,828 0 Total $ 1,277,639 $ 10,912 $ 29,337 $ 1,259,214 $ 26,038 December 31, 2015 (In thousands) Amortized Gross Gross Estimated Cumulative (1) U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 71,993 $ 1,793 $ 0 $ 73,786 $ 0 State and political subdivisions 130,685 3,144 51 133,778 0 Residential mortgage-backed securities Agency 473,109 5,580 707 477,982 0 Non-agency 9,119 457 5 9,571 458 Commercial mortgage-backed securities Agency 305,990 1,843 1,898 305,935 0 Asset-backed securities 3,404 0 5 3,399 0 Trust preferred collateralized debt obligations 49,386 635 15,335 34,686 25,952 Single issue trust preferred securities 13,811 249 2,367 11,693 0 Other corporate securities 9,999 50 0 10,049 0 Marketable equity securities 4,844 637 26 5,455 0 Total $ 1,072,340 $ 14,388 $ 20,394 $ 1,066,334 $ 26,410 (1) Other-than-temporary impairment in accumulated other comprehensive income. Amounts are before-tax. The following is a summary of securities available for sale which were in an unrealized loss position at December 31, 2016 and 2015. Less than 12 months 12 months or longer (In thousands) Fair Unrealized Fair Unrealized December 31, 2016 U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 24,101 $ 159 $ 0 $ 0 State and political subdivisions 116,300 4,902 0 0 Residential mortgage-backed securities Agency 309,376 5,111 0 0 Non-agency 0 0 218 12 Commercial mortgage-backed securities Agency 162,479 1,242 0 0 Asset-backed securities 0 0 0 0 Trust preferred collateralized debt obligations 0 0 28,579 15,735 Single issue trust preferred securities 0 0 8,185 2,170 Marketable equity securities 357 6 0 0 Total $ 612,613 $ 11,420 $ 36,982 $ 17,917 Less than 12 months 12 months or longer (In thousands) Fair Unrealized Fair Unrealized December 31, 2015 U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 0 $ 0 $ 0 $ 0 State and political subdivisions 15,550 51 0 0 Residential mortgage-backed securities Agency 90,004 707 0 0 Non-agency 348 5 0 0 Commercial mortgage-backed securities Agency 170,340 1,650 9,255 248 Asset-backed securities 3,399 5 0 0 Trust preferred collateralized debt obligations 3,304 135 28,633 15,200 Single issue trust preferred securities 4,225 404 3,720 1,963 Marketable equity securities 986 26 0 0 Total $ 288,156 $ 2,983 $ 41,608 $ 17,411 Marketable equity securities consist mainly of equity securities of financial institutions and mutual funds within a rabbi trust for the payment of benefits under a deferred compensation plan for certain key officers of United and its subsidiaries. The following table shows the proceeds from maturities, sales and calls of available for sale securities and the gross realized gains and losses on sales and calls of those securities that have been included in earnings as a result of any sales and calls. Gains or losses on sales and calls of available for sale securities were recognized by the specific identification method. The realized losses relate to sales of securities within a rabbi trust for the payment of benefits under a deferred compensation plan for certain key officers and its subsidiaries. Year Ended (In thousands) 2016 2015 2014 Proceeds from maturities, sales and calls $ 513,990 $ 191,266 $ 534,489 Gross realized gains 268 143 3,592 Gross realized losses 13 10 235 At December 31, 2016, gross unrealized losses on available for sale securities were $29,337,000 on 347 securities of a total portfolio of 640 available for sale securities. Securities in an unrealized loss position at December 31, 2016 consisted primarily of pooled trust preferred collateralized debt obligations (Trup Cdos), state and political subdivision securities, single issue trust preferred securities and agency residential mortgage-backed securities. The Trup Cdos and the single issue trust preferred securities relate mainly to securities of financial institutions. The state and political subdivisions securities relate to securities issued by various municipalities The agency residential mortgage-backed securities relate to residential properties and provide a guaranty of full and timely payments of principal and interest by the issuing agency. In determining whether or not a security is other-than-temporarily impaired (OTTI), management considered the severity and the duration of the loss in conjunction with United’s positive intent and the more likely than not ability to hold these securities to recovery of their cost basis or maturity. State and political subdivisions United’s state and political subdivisions portfolio relates to securities issued by various municipalities located throughout the United States. The total amortized cost of available for sale state and political subdivision securities was $196,350,000 at December 31, 2016. As of December 31, 2016, approximately 81% of the portfolio was supported by the general obligation of the issuing municipality, which allows for the securities to be repaid by any means available to the municipality. The majority of the portfolio was rated AA or higher, and less than one percent of the portfolio was rated below investment grade as of December 31, 2016. In addition to monitoring the credit ratings of these securities, management also evaluates the financial performance of the underlying issuers on an ongoing basis. Based upon management’s analysis and judgment, it was determined that none of the state and political subdivision securities were other-than-temporarily impaired at December 31, 2016. Agency mortgage-backed securities United’s agency mortgage-backed securities portfolio relates to securities issued by Fannie Mae, Freddie Mac, and Ginnie Mae. The total amortized cost of available for sale agency mortgage securities was $889,843,000 at December 31, 2016. Of the $889,843,000, $304,635,000 was related to agency commercial mortgage securities and $585,208,000 was related to agency residential mortgage securities. Each of the agency mortgage securities provides a guarantee of full and timely payments of principal and interest by the issuing agency. Based upon management’s analysis and judgment, it was determined that none of the agency mortgage-backed securities were other-than-temporarily impaired at December 31, 2016. Non-agency residential mortgage-backed securities United’s non-agency residential mortgage-backed securities portfolio relates to securities of various private label issuers. The total amortized cost of available for sale non-agency residential mortgage securities was $6,629,000 at December 31, 2016. Of the $6,629,000, $1,054,000 was rated above investment grade and $5,575,000 was rated below investment grade. Approximately 23% of the portfolio includes collateral that was originated during the year of 2005 or before. The remaining 77% includes collateral that was originated in the years of 2006 and 2007. The entire portfolio of the non-agency residential mortgage securities are either the senior or super-senior tranches of their respective structure. Based upon management’s analysis and judgment, there was no additional credit-related or noncredit-related other-than-temporary impairment recognized on the non-agency residential mortgage-backed securities at December 31, 2016. Single issue trust preferred securities The majority of United’s single-issue trust preferred portfolio consists of obligations from large cap banks (i.e. banks with market capitalization in excess of $10 billion). Management reviews each issuer’s current and projected earnings trends, asset quality, capitalization levels, and other key factors. Upon completing the review for the fourth quarter of 2016, it was determined that none of the single issue securities were other-than-temporarily impaired. All single-issue trust preferred securities are currently receiving interest payments. The available for sale single issue trust preferred securities’ ratings ranged from a low of Ba1 to a high of BBB-. The amortized cost of available for sale single issue trust preferred securities as of December 31, 2016 consisted of $3,008,000 in investment grade bonds, $4,658,000 in split-rated bonds and $5,697,000 in below investment grade bonds. All of the unrated bonds were in an unrealized loss position for twelve months or longer as of December 31, 2016. Trust preferred collateralized debt obligations (Trup Cdos) In order to determine how and when the Company recognizes OTTI, the Company first assesses its intentions regarding any sale of securities as well as the likelihood that it would be required to sell prior to recovery of the amortized cost. As of December 31, 2016, the Company has determined that it does not intend to sell any pooled trust preferred security and that it is not more likely than not that the Company will be required to sell such securities before recovery of their amortized cost. To determine a net realizable value and assess whether other-than-temporary impairment existed, management performed detailed cash flow analysis to determine whether, in management’s judgment, it was more likely that United would not recover the entire amortized cost basis of the security. The Company discounts the security-specific cash flow projection at the security-specific interest rate and compares the present value to the amortized cost. Management’s cash flow analysis was performed for each security and considered the current deferrals and defaults within the underlying collateral, the likelihood that current deferrals would cure or ultimately default, potential future deferrals and defaults, potential prepayments, cash reserves, excess interest spread, credit analysis of the underlying collateral and the priority of payments in the cash flow structure. The underlying collateral analysis for each issuer took into consideration multiple factors including capital adequacy, earnings trends and asset quality. After completing its analysis of estimated cash flows, management determined that none of the Trup Cdos experienced an adverse change in cash flows during the fourth quarter of 2016, as the expected discounted cash flows from these particular securities were greater than or equal to the discounted cash flows originally expected at purchase or from the previous date of other-than-temporary impairment (cash flows are discounted at the contractual coupon rate for purposes of assessing OTTI). There was no credit-related other-than-temporary impairment recognized in earnings for the fourth quarter of 2016 related to these securities. There was no credit-related other-than-temporary impairment recognized in earnings during 2016 related to these securities, compared to $34,000 in 2015. At December 31, 2016 and 2015, the balance of noncredit-related other-than-temporary impairment recognized on United’s Trup Cdo portfolio was $25,952,000. The amortized cost of available for sale Trup Cdos in an unrealized loss position for twelve months or longer as of December 31, 2016 consisted of $3,847,000 in investment grade bonds and $40,468,000 in below investment grade bonds. The following is a summary of the available for sale Trup Cdos as of December 31, 2016. Amortized Cost Class Amortized Cost Fair Value Net Loss Investment Split Below (In thousands) Senior – Bank $ 5,988 $ 5,545 $ 443 $ 3,847 $ 0 $ 2,141 Mezzanine —Bank (now in senior position) 11,309 8,175 3,134 0 0 11,309 Mezzanine – Bank 26,095 16,170 9,925 0 0 26,095 Mezzanine – Bank & Insurance (combination) 5,166 3,662 1,504 0 0 5,166 Totals $ 48,558 $ 33,552 $ 15,006 $ 3,847 $ 0 $ 44,711 While a large difference remains between the fair value and amortized cost, the Company believes the remaining unrealized losses are related to the illiquid market for Trup Cdos rather than an adverse change in expected cash flows. The expected future cash flow substantiates the return of the remaining amortized cost of the security. The Company believes the following evidence supports the position that the remaining unrealized loss is related to the illiquid market for Trup Cdos: • The market for new issuance of Trup Cdos was robust from 2000 to 2007 with an estimated $60 billion in new issuance. The new market issuances came to an abrupt halt in 2007. • The secondary market for Trup Cdos ultimately became illiquid and although the market has improved, trading activity remains limited on these securities. In making this determination, the Company holds discussions with institutional traders to identify trends in the number and type of transactions related to the Trup Cdos. • The presence of a below-investment grade rating severely limits the pool of available buyers and contributes to the illiquidity of the market. • Trup Cdos have a more complex structure than most debt instruments, making projections of tranche returns difficult for non-specialists in the product. Deferral features available to the underlying issuers within each pool are unique to these securities. Additionally, it can be difficult for market participants to predict whether deferrals will ultimately cure or ultimately default. Due to the lack of transparency, market participants will require a higher risk premium, thus resulting in higher required discount rates. • The variability of cash flows at the time the securities were originated was expected to be very limited. Due to the financial crisis, Trup Cdos have experienced more substantive variability of cash flows compared to expectations, resulting in a higher risk premium when evaluating discount rates. • The limited, yet relevant, observable inputs indicate that market yield requirements for Trup Cdos, on a credit-adjusted basis, remained very high relative to discount rates at purchase and compared to other similarly rated debt securities. Overall, the Company believes the lack of new issuances, illiquid secondary market, limited pool of buyers, below investment grade ratings, and complex structures are the key drivers of the remaining unrealized losses in the Company’s Trup Cdos and the robust expected cash flow analysis substantiates the return of the remaining amortized cost under ASC 320. Management also considered the ratings of the Company’s bonds in its portfolio and the extent of downgrades in United’s impairment analysis. However, management considered it imperative to independently perform its own credit analysis based on cash flows as described. The ratings of the investment grade Trup Cdos in the table above range from a low of AA to a high of Aaa. The below investment grade Trup Cdos range from a low of C to a high of Ba1. On the Trup Cdos that have not been deemed to be other-than-temporarily impaired, the collateralization ratios range from a low of 104.2% to a high of 344.2%, with a median of 158.6%, and a weighted average of 221.9%. The collateralization ratio is defined as the current performing collateral in a security, divided by the current balance of the specific tranche the Company owns, plus any debt which is senior or pari passu with the Company’s security’s priority level. Performing collateral excludes the balance of any issuer that has either defaulted or has deferred its interest payment. It is not uncommon for the collateralization of a security that is not other-than-temporarily impaired to be less than 100% due to the excess spread built into the securitization structure. Except for the debt securities that have already been deemed to be other-than-temporarily impaired, management does not believe any other individual security with an unrealized loss as of December 31, 2016 is other-than-temporarily impaired. For these securities, United believes the decline in value resulted from changes in market interest rates, credit spreads and liquidity, not a change in the expected contractual cash flows. Based on a review of each of the securities in the investment portfolio, management concluded that it expected to recover the amortized cost basis of the investment in such securities. Equity securities The cost of United’s equity securities was $12,436,000 at December 31, 2016. For equity securities, management has evaluated the near-term prospects of the investment in relation to the severity and duration of any impairment and based on that evaluation, management determined that no equity securities were other-than-temporarily impaired at December 31, 2016. Other investment securities (cost method) During the fourth quarter of 2016, United also evaluated all of its cost method investments to determine if certain events or changes in circumstances during the quarter had a significant adverse effect on the fair value of any of its cost method securities. United determined that there were no events or changes in circumstances during the fourth quarter of 2016 which would have an adverse effect on the fair value of any of its cost method securities. Therefore, no impairment was recorded. Below is a progression of the credit losses on securities which United has recorded other-than-temporary charges. These charges were recorded through earnings and other comprehensive income. (In thousands) Year Ended December 31 2016 2015 2014 Balance of cumulative credit losses at beginning of period $ 23,773 $ 23,739 $ 40,663 Additional credit losses on securities for which OTTI was previously recognized 33 34 6,442 Reductions for securities sold or paid off during the period (1,644) 0 (23,366) Balance of cumulative credit losses at end of period $ 22,162 $ 23,773 $ 23,739 The amortized cost and estimated fair value of securities available for sale at December 31, 2016 by contractual maturity are shown below. Expected maturities may differ from contractual maturities because the issuers may have the right to call or prepay obligations without penalties. Maturities of mortgage-backed securities with an amortized cost of $896,472,000 and an estimated fair value of $896,480,000 at December 31, 2016 are included below based upon contractual maturity. Estimated (In thousands) Amortized Fair Cost Value Due in one year or less $ 53,286 $ 53,330 Due after one year through five years 296,181 297,385 Due after five years through ten years 213,094 213,791 Due after ten years 702,642 680,880 Marketable equity securities 12,436 13,828 Total $ 1,277,639 $ 1,259,214 The following is a summary of the amortized cost and estimated fair values of securities held to maturity. December 31, 2016 (In thousands) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 5,295 $ 570 $ 0 $ 5,865 State and political subdivisions 8,598 17 0 8,615 Residential mortgage-backed securities Agency 30 5 0 35 Single issue trust preferred securities 19,315 0 2,672 16,643 Other corporate securities 20 0 0 20 Total $ 33,258 $ 592 $ 2,672 $ 31,178 December 31, 2015 (In thousands) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 10,425 $ 860 $ 0 $ 11,285 State and political subdivisions 9,321 21 253 9,089 Residential mortgage-backed securities Agency 35 6 0 41 Single issue trust preferred securities 19,298 0 3,414 15,884 Other corporate securities 20 0 0 20 Total $ 39,099 $ 887 $ 3,667 $ 36,319 Even though the market value of the held-to-maturity investment portfolio is less than its cost, the unrealized loss has no impact on the net worth or regulatory capital requirements of United. As of December 31, 2016, the Company’s two largest held-to-maturity single-issue trust preferred exposures were to Wells Fargo ($9,922,000) and SunTrust Bank ($7,418,000). The two held-to-maturity single-issue trust preferred exposures with at least one rating below investment grade included SunTrust Bank ($7,418,000) and Royal Bank of Scotland ($976,000). Other corporate securities consist mainly of bonds of corporations. The following table shows the gross realized gains and losses on calls and sales of held to maturity securities that have been included in earnings as a result of those calls and sales. Gains or losses on calls of held to maturity securities are recognized by the specific identification method. Year Ended (In thousands) 2016 2015 2014 Gross realized gains $ 0 $ 0 $ 9 Gross realized losses 0 0 0 The amortized cost and estimated fair value of debt securities held to maturity at December 31, 2016 by contractual maturity are shown below. Expected maturities may differ from contractual maturities because the issuers may have the right to call or prepay obligations with or without call or prepayment penalties. Maturities of mortgage-backed securities with an amortized cost of $30,000 and an estimated fair value of $35,000 at December 31, 2016 are included below based upon contractual maturity. Estimated (In thousands) Amortized Fair Cost Value Due in one year or less $ 1,040 $ 1,041 Due after one year through five years 8,268 8,850 Due after five years through ten years 3,585 3,589 Due after ten years 20,365 17,698 Total $ 33,258 $ 31,178 The carrying value of securities pledged to secure public deposits, securities sold under agreements to repurchase, and for other purposes as required or permitted by law, approximated $1,137,408,000 and $986,982,000 at December 31, 2016 and 2015, respectively. The fair value of mortgage-backed mortgage-backed The following table sets forth the maturities of all securities (based on amortized cost) at December 31, 2016, and the weighted-average yields of such securities (calculated on the basis of the cost and the effective yields weighted for the scheduled maturity of each security). After 1 But After 5 But (Dollars in thousands) Within 1 Year Within 5 Years Within 10 Years After 10 Years Amount Yield Amount Yield Amount Yield Amount Yield U.S. Treasury and other U.S. Government agencies and corporations $ 32,097 0.39 % $ 61,924 2.04 % $ 6,521 2.25 % $ 0 0.00 % States and political subdivisions (1) 14,451 2.89 % 41,926 3.24 % 34,096 3.81 % 114,475 3.94 % Residential mortgage-backed securities Agency 68 5.44 % 5,043 4.01 % 58,141 2.72 % 521,986 2.34 % Non-agency 0 0.00 % 1,339 5.00 % 0 0.00 % 5,290 5.83 % Commercial mortgage-backed Agency 9,051 0.95 % 188,624 1.79 % 106,960 2.63 % 0 0.00 % Asset-backed securities 217 1.38 % 0 0.00 % 0 0.00 % 0 0.00 % Trust preferred collateralized debt obligations 0 0.00 % 0 0.00 % 0 0.00 % 48,558 3.80 % Single issue trust preferred securities 0 0.00 % 0 0.00 % 0 0.00 % 32,678 2.84 % Marketable equity securities 0 0.00 % 0 0.00 % 0 0.00 % 12,436 0.64 % Other Corporate securities 0 0.00 % 4,996 1.98 % 10,000 5.50 % 20 0.00 % (1) Tax-equivalent There are no securities with a single issuer, other than the U.S. government and its agencies and corporations, the book value of which in the aggregate exceeds 10% of United’s total shareholders’ equity.

Loans

Loans	12 Months Ended
	Dec. 31, 2016
Receivables [Abstract]
Loans	NOTE D—LOANS Major classes of loans are as follows: December 31 (In thousands) 2016 2015 Commercial, financial, and agricultural Owner-occupied $ 1,049,885 $ 927,746 Nonowner-occupied 3,425,453 2,896,367 Other commercial 1,613,437 1,602,222 Total commercial, financial & agricultural 6,088,775 5,426,335 Residential real estate 2,403,437 2,268,685 Construction & land development 1,255,738 1,273,054 Consumer: Bankcard 14,187 11,653 Other Consumer 594,582 419,225 Less: Unearned interest (15,582) (14,872) Total Loans, net of unearned interest $ 10,341,137 $ 9,384,080 The table above does not include loans held for sale of $8,445,000 and $10,681,000 at December 31, 2016 and December 31, 2015, respectively. Loans held for sale consist of single-family residential real estate loans originated for sale in the secondary market. The outstanding balances in the table above include acquired impaired loans with a recorded investment of $171,596,000 or 1.66% of total gross loans at December 31, 2016 and $148,197,000 or 1.58% of total gross loans at December 31, 2015, respectively. The contractual principal in these acquired impaired loans was $231,096,000 and $208,765,000 at December 31, 2016 and 2015, respectively. The balances above do not include future accretable net interest (i.e. the difference between the undiscounted expected cash flows and the recorded investment in the loan) on the acquired impaired loans. Activity for the accretable yield for the year of 2016 follows. (In thousands) Accretable yield at the beginning of the period $ 12,156 Accretion (including cash recoveries) (11,457 ) Additions for Bank of Georgetown acquisition 19,552 Net reclassifications to accretable from non-accretable 12,439 Disposals (including maturities, foreclosures, and charge-offs) (3,525 ) Accretable yield at the ending of the period $ 29,165 At December 31, 2016 and 2015, loans-in-process of $38,591,000 and $66,501,000 and overdrafts from deposit accounts of $7,971,000 and $9,234,000, respectively, are included within the appropriate loan classifications above. United’s subsidiary banks have made loans, in the normal course of business, to the directors and officers of United and its subsidiaries, and to their associates. The aggregate dollar amount of these loans was $255,476,000 and $241,000,000 at December 31, 2016 and 2015, respectively. During 2016, $393,273,000 of new loans were made, repayments totaled $378,797,000.

Credit Quality

Credit Quality	12 Months Ended
	Dec. 31, 2016
Text Block [Abstract]
Credit Quality	NOTE E—CREDIT QUALITY Management monitors the credit quality of its loans on an ongoing basis. Measurement of delinquency and past due status are based on the contractual terms of each loan. For all loan classes, past due loans are reviewed on a monthly basis to identify loans for nonaccrual status. Generally, when collection in full of the principal and interest is jeopardized, the loan is placed on nonaccrual status. The accrual of interest income on commercial and most consumer loans generally is discontinued when a loan becomes 90 to 120 days past due as to principal or interest. However, regardless of delinquency status, if a loan is fully secured and in the process of collection and resolution of collection is expected in the near term (generally less than 90 days), then the loan will not be placed on nonaccrual status. When interest accruals are discontinued, unpaid interest recognized in income in the current year is reversed, and unpaid interest accrued in prior years is charged to the allowance for loan losses. United’s method of income recognition for loans that are classified as nonaccrual is to recognize interest income on a cash basis or apply the cash receipt to principal when the ultimate collectibility of principal is in doubt. Nonaccrual loans will not normally be returned to accrual status unless all past due principal and interest has been paid and the borrower has evidenced their ability to meet the contractual provisions of the note. A loan is categorized as a troubled debt restructuring (TDR) if a concession is granted and there is deterioration in the financial condition of the borrower. TDRs can take the form of a reduction of the stated interest rate, splitting a loan into separate loans with market terms on one loan and concessionary terms on the other loan, receipts of assets from a debtor in partial or full satisfaction of a loan, the extension of the maturity date or dates at a stated interest rate lower than the current market rate for new debt with similar risk, the reduction of the face amount or maturity amount of the debt as stated in the instrument or other agreement, the reduction of accrued interest or any other concessionary type of renegotiated debt. As of December 31, 2016, United had TDRs of $21,152,000 as compared to $23,890,000 as of December 31, 2015. Of the $21,152,000 aggregate balance of TDRs at December 31, 2016, $11,106,000 was on nonaccrual status and included in the “Loans on Nonaccrual Status” on the following pages. Of the $23,890,000 aggregate balance of TDRs at December 31, 2015, $11,949,000 was on nonaccrual status and included in the “Loans on Nonaccrual Status” on the following page. As of December 31, 2016, there were no commitments to lend additional funds to debtors owing receivables whose terms have been modified in TDRs. At December 31, 2016, United had restructured loans in the amount of $2,667,000 that were modified by a reduction in the interest rate, $6,513,000 that were modified by a combination of a reduction in the interest rate and the principal and $11,972,000 that was modified by a change in terms. A loan acquired and accounted for under ASC topic 310-30 “Loans and Debt Securities Acquired with Deteriorated Credit Quality” is reported as an accruing loan and a performing asset unless it does not perform in accordance with its restructured contractual provisions. The following table sets forth United’s troubled debt restructurings that have been restructured during the year ended December 31, 2016 and 2015, segregated by class of loans: Troubled Debt Restructurings For the Year Ended December 31, 2016 (In thousands) Number of Pre-Modification Post-Modification Commercial real estate: Owner-occupied 1 $ 1,190 $ 1,178 Nonowner-occupied 0 0 0 Other commercial 7 2,803 2,213 Residential real estate 1 1,400 1,400 Construction & land development 0 0 0 Consumer: Bankcard 0 0 0 Other consumer 0 0 0 Total 9 $ 5,393 $ 4,791 Troubled Debt Restructurings For the Year Ended December 31, 2015 (In thousands) Number of Pre-Modification Post-Modification Commercial real estate: Owner-occupied 0 $ 0 $ 0 Nonowner-occupied 1 669 647 Other commercial 3 2,942 2,918 Residential real estate 0 0 0 Construction & land development 0 0 0 Consumer: Bankcard 0 0 0 Other consumer 0 0 0 Total 4 $ 3,611 $ 3,565 During 2016, $2,887,000 of restructured loans were modified by a change in loan terms and $1,904,000 of restructured loans were modified by a combination of a reduction in the interest rate and an extension of the maturity date. During 2015, restructured loans of $3,565,000 were modified by a change in terms. In some instances, the post-modification balance on a restructured loan is larger than the pre-modification balance due to the advancement of monies for items such as delinquent taxes on real estate property. The loans were evaluated individually for allocation within United’s allowance for loan losses. The modifications had an immaterial impact on the financial condition and results of operations for United. The following table presents a troubled debt restructuring, by class of loan, that had a charge-off during the year ended December 31, 2016. This loan was restructured during the twelve months ended December 31, 2016 and subsequently defaulted, resulting in a principal charge-off during the year of 2016. No loans restructured during the twelve-month period ended December 31, 2015 subsequently defaulted, resulting in a principal charge-off during the year ended December 31, 2015. Year Ended December 31, 2016 (In thousands) Number of Recorded Troubled Debt Restructurings Commercial real estate: 0 $ 0 Owner-occupied 0 0 Nonowner-occupied 0 0 Other commercial 1 37 Residential real estate 0 0 Construction & land development 0 0 Consumer: 0 0 Bankcard 0 0 Other consumer 0 0 Total 1 $ 37 The following table sets forth United’s age analysis of its past due loans, segregated by class of loans: Age Analysis of Past Due Loans As of December 31, 2016 (In thousands) 30-89 90 Days or more Total Past Current & Total Financing Recorded Commercial real estate: Owner-occupied $ 5,850 $ 3,981 $ 9,831 $ 1,040,054 $ 1,049,885 $ 94 Nonowner-occupied 9,288 20,847 30,135 3,395,318 3,425,453 172 Other commercial 15,273 42,766 58,039 1,555,398 1,613,437 2,518 Residential real estate 29,976 25,991 55,967 2,347,470 2,403,437 4,216 Construction & land development 3,809 7,779 11,588 1,244,150 1,255,738 33 Consumer: Bankcard 422 141 563 13,624 14,187 141 Other consumer 10,015 1,712 11,727 582,855 594,582 1,412 Total $ 74,633 $ 103,217 $ 177,850 $ 10,178,869 $ 10,356,719 $ 8,586 (1) Other includes loans with a recorded investment of $171,596 acquired and accounted for under ASC topic 310-30 “Loans and Debt Securities Acquired with Deteriorated Credit Quality”. Age Analysis of Past Due Loans As of December 31, 2015 (In thousands) 30-89 90 Days or more Total Past Current & Total Financing Recorded Commercial real estate: Owner-occupied $ 8,639 $ 9,831 $ 18,470 $ 909,276 $ 927,746 $ 400 Nonowner-occupied 24,209 26,126 50,335 2,846,032 2,896,367 552 Other commercial 14,888 33,297 48,185 1,554,037 1,602,222 3,643 Residential real estate 44,312 28,332 72,644 2,196,041 2,268,685 4,294 Construction & land development 2,412 15,416 17,828 1,255,226 1,273,054 1,347 Consumer: Bankcard 223 168 391 11,262 11,653 168 Other consumer 9,082 1,596 10,678 408,547 419,225 1,224 Total $ 103,765 $ 114,766 $ 218,531 $ 9,180,421 $ 9,398,952 $ 11,628 (1) Other includes loans with a recorded investment of $148,197 acquired and accounted for under ASC topic 310-30 “Loans and Debt Securities Acquired with Deteriorated Credit Quality”. The following table sets forth United’s nonaccrual loans, segregated by class of loans: Loans on Nonaccrual Status (In thousands) December 31, 2016 December 31, 2015 Commercial real estate: Owner-occupied $ 3,887 $ 9,431 Nonowner-occupied 20,675 25,574 Other commercial 40,248 29,654 Residential real estate 21,775 24,038 Construction & land development 7,746 14,069 Consumer: Bankcard 0 0 Other consumer 300 372 Total $ 94,631 $ 103,138 United assigns credit quality indicators of pass, special mention, substandard and doubtful to its loans. For United’s loans with a corporate credit exposure, United internally assigns a grade based on the creditworthiness of the borrower. For loans with a consumer credit exposure, United internally assigns a grade based upon an individual loan’s delinquency status. United reviews and updates, as necessary, these grades on a quarterly basis. Special mention loans, with a corporate credit exposure, have potential weaknesses that deserve management’s close attention. If left uncorrected, these potential weaknesses may result in deterioration of the repayment prospects for the loans or in the Company’s credit position at some future date. Borrowers may be experiencing adverse operating trends (declining revenues or margins) or an ill proportioned balance sheet (e.g., increasing inventory without an increase in sales, high leverage, tight liquidity). Adverse economic or market conditions, such as interest rate increases or the entry of a new competitor, may also support a special mention rating. Nonfinancial reasons for rating a credit exposure special mention include management problems, pending litigation, an ineffective loan agreement or other material structural weakness, and any other significant deviation from prudent lending practices. For loans with a consumer credit exposure, loans that are past due 30-89 days are generally considered special mention. A substandard loan with a corporate credit exposure is inadequately protected by the current sound worth and paying capacity of the obligor or of the collateral pledged, if any. Loans so classified have a well-defined weakness, or weaknesses, that jeopardize the liquidation of the debt by the borrower. They are characterized by the distinct possibility that the Company will sustain some loss if the deficiencies are not corrected. They require more intensive supervision by management. Substandard loans are generally characterized by current or expected unprofitable operations, inadequate debt service coverage, inadequate liquidity, or marginal capitalization. Repayment may depend on collateral or other credit risk mitigants. For some substandard loans, the likelihood of full collection of interest and principal may be in doubt and thus, placed on nonaccrual. For loans with a consumer credit exposure, loans that are 90 days or more past due or that have been placed on nonaccrual are considered substandard. A loan with corporate credit exposure is classified as doubtful if it has all the weaknesses inherent in one classified as substandard with the added characteristic that the weaknesses make collection in full, on the basis of currently existing facts, conditions, and values, highly questionable and improbable. A doubtful loan has a high probability of total or substantial loss, but because of specific pending events that may strengthen the loan, its classification as loss is deferred. Doubtful borrowers are usually in default, lack adequate liquidity or capital, and lack the resources necessary to remain an operating entity. Pending events can include mergers, acquisitions, liquidations, capital injections, the perfection of liens on additional collateral, the valuation of collateral, and refinancing. Generally, there are not any loans with a consumer credit exposure that are classified as doubtful. Usually, they are charged-off prior to such a classification. Loans classified as doubtful are also considered impaired. The following tables set forth United’s credit quality indicators information, by class of loans: Credit Quality Indicators Corporate Credit Exposure As of December 31, 2016 Commercial Real Estate (In thousands) Owner- Nonowner- Other Construction & Grade: Pass $ 963,503 $ 3,284,497 $ 1,463,797 $ 1,126,742 Special mention 20,490 36,462 26,537 52,327 Substandard 65,892 104,494 122,893 76,669 Doubtful 0 0 210 0 Total $ 1,049,885 $ 3,425,453 $ 1,613,437 $ 1,255,738 Credit Quality Indicators Corporate Credit Exposure As of December 31, 2015 Commercial Real Estate (In thousands) Owner- Nonowner- Other Construction & Grade: Pass $ 835,082 $ 2,710,504 $ 1,436,670 $ 1,095,238 Special mention 20,391 32,249 26,148 59,100 Substandard 72,273 153,614 136,585 118,716 Doubtful 0 0 2,819 0 Total $ 927,746 $ 2,896,367 $ 1,602,222 $ 1,273,054 Credit Quality Indicators Consumer Credit Exposure As of December 31, 2016 (In thousands) Residential Bankcard Other Grade: Pass $ 2,348,017 $ 13,624 $ 582,704 Special mention 18,240 422 10,132 Substandard 36,995 141 1,746 Doubtful 185 0 0 Total $ 2,403,437 $ 14,187 $ 594,582 As of December 31, 2015 (In thousands) Residential Bankcard Other Grade: Pass $ 2,195,420 $ 11,262 $ 408,271 Special mention 13,494 223 9,188 Substandard 57,981 168 1,766 Doubtful 1,790 0 0 Total $ 2,268,685 $ 11,653 $ 419,225 Loans are designated as impaired when, in the opinion of management, based on current information and events, the collection of principal and interest in accordance with the loan contract is doubtful. Typically, United does not consider loans for impairment unless a sustained period of delinquency (i.e. 90-plus days) is noted or there are subsequent events that impact repayment probability (i.e. negative financial trends, bankruptcy filings, eminent foreclosure proceedings, etc.). Impairment is evaluated in total for smaller-balance loans of a similar nature and on an individual loan basis for other loans. Consistent with United’s existing method of income recognition for loans, interest on impaired loans, except those classified as nonaccrual, is recognized as income using the accrual method. Impaired loans, or portions thereof, are charged off when deemed uncollectible. The following table set forth United’s impaired loans information, by class of loans: Impaired Loans December 31, 2016 December 31, 2015 (In thousands) Recorded Unpaid Related Recorded Unpaid Related With no related allowance recorded: Commercial real estate: Owner-occupied $ 46,575 $ 47,108 $ 0 $ 36,615 $ 36,828 $ 0 Nonowner-occupied 92,654 93,104 0 69,053 69,517 0 Other commercial 46,064 48,308 0 30,433 32,158 0 Residential real estate 22,747 24,404 0 21,431 22,329 0 Construction & land development 19,863 21,746 0 28,245 29,953 0 Consumer: Bankcard 0 0 0 0 0 0 Other consumer 36 36 0 32 32 0 With an allowance recorded: Commercial real estate: Owner-occupied $ 1,787 $ 2,082 $ 815 $ 4,555 $ 4,555 $ 1,253 Nonowner-occupied 17,938 17,938 2,524 7,890 7,890 1,362 Other commercial 43,774 46,188 13,441 29,486 33,127 18,269 Residential real estate 12,066 12,801 3,431 13,305 14,625 2,118 Construction & land development 4,940 7,899 3,206 14,132 20,135 4,789 Consumer: Bankcard 0 0 0 0 0 0 Other consumer 0 0 0 0 0 0 Total: Commercial real estate: Owner-occupied $ 48,362 $ 49,190 $ 815 $ 41,170 $ 41,383 $ 1,253 Nonowner-occupied 110,592 111,042 2,524 76,943 77,407 1,362 Other commercial 89,838 94,496 13,441 59,919 65,285 18,269 Residential real estate 34,813 37,205 3,431 34,736 36,954 2,118 Construction & land development 24,803 29,645 3,206 42,377 50,088 4,789 Consumer: Bankcard 0 0 0 0 0 0 Other consumer 36 36 0 32 32 0 Impaired Loans For the Year Ended December 31, 2016 December 31, 2015 (In thousands) Average Interest Average Interest With no related allowance recorded: Commercial real estate: Owner-occupied $ 36,800 $ 1,038 $ 41,336 $ 264 Nonowner-occupied 75,848 1,108 68,727 1,139 Other commercial 39,776 1,540 33,510 463 Residential real estate 25,964 538 27,224 234 Construction & land development 24,902 133 33,167 199 Consumer: Bankcard 0 0 0 0 Other consumer 33 0 35 0 With an allowance recorded: Commercial real estate: Owner-occupied $ 3,138 $ 97 $ 4,629 $ 122 Nonowner-occupied 11,920 564 6,954 357 Other commercial 36,511 1,615 20,885 580 Residential real estate 9,585 342 9,314 41 Construction & land development 8,994 83 12,196 252 Consumer: Bankcard 0 0 0 0 Other consumer 0 0 0 0 Total: Commercial real estate: Owner-occupied $ 39,938 $ 1,135 $ 45,965 $ 386 Nonowner-occupied 87,768 1,672 75,681 1,496 Other commercial 76,287 3,155 54,395 1,043 Residential real estate 35,549 880 36,538 275 Construction & land development 33,896 216 45,363 451 Consumer: Bankcard 0 0 0 0 Other consumer 33 0 35 0

Allowance for Credit Losses

Allowance for Credit Losses	12 Months Ended
	Dec. 31, 2016
Receivables [Abstract]
Allowance for Credit Losses	NOTE F—ALLOWANCE FOR CREDIT LOSSES The allowance for loan losses is management’s estimate of the probable credit losses inherent in the loan portfolio. For purposes of determining the general allowance, the loan portfolio is segregated by product type to recognize differing risk profiles among categories. It is further segregated by credit grade for non-homogenous loan pools and delinquency for homogeneous loan pools. The outstanding principal balance within each pool is multiplied by historical loss data, the loss emergence period (which is the period of time between the event that triggers a loss and the confirmation and/or charge off of that loss) and certain qualitative factors to derive the general loss allocation per pool. Specific loss allocations are calculated for commercial loans in excess of $500,000 in accordance with ASC topic 310. Risk characteristics of owner-occupied commercial real estate loans and other commercial loans are similar in that they are normally dependent upon the borrower’s internal cash flow from operations to service debt. Nonowner-occupied commercial real estate loans differ in that cash flow to service debt is normally dependent on external income from third parties for use of the real estate such as rents, leases and room rates. Residential real estate loans are dependent upon individual borrowers who are affected by changes in general economic conditions, demand for housing and resulting residential real estate valuation. Construction and land development loans are impacted mainly by demand whether for new residential housing or for retail, industrial, office and other types of commercial construction within a given area. Consumer loan pool risk characteristics are influenced by general, regional and local economic conditions. Beginning in 2015, United’s methodology related to the allowance for loan losses was enhanced by estimating the loss emergence period. The impact of this enhancement was not significant. Loans deemed to be uncollectible are charged against the allowance for loan losses, while recoveries of previously charged-off amounts are credited to the allowance for loan losses. For commercial loans, when a loan or a portion of a loan is identified to contain a loss, a charge-off recommendation is directed to management to charge-off all or a portion of that loan. Generally, any unsecured commercial loan more than six months delinquent in payment of interest must be charged-off in full. If secured, the charge-off is generally made to reduce the loan balance to a level equal to the liquidation value of the collateral when payment of principal and interest is six months delinquent. Any commercial loan, secured or unsecured, on which a principal or interest payment has not been made within 90 days, is reviewed monthly for appropriate action. For consumer loans, closed-end retail loans that are past due 120 cumulative days delinquent from the contractual due date and open-end loans 180 cumulative days delinquent from the contractual due date are charged-off. Any consumer loan on which a principal or interest payment has not been made within 90 days is reviewed monthly for appropriate action. For a one-to-four family open-end or closed-end residential real estate loan, home equity loan, or high-loan-to-value loan that has reached 180 or more days past due, management evaluates the collateral position and charges-off any amount that exceeds the value of the collateral. On retail credits for which the borrower is in bankruptcy, all amounts deemed unrecoverable are charged off within 60 days of the receipt of the notification. On retail credits effected by fraud, a loan is charged-off within 90 days of the discovery of the fraud. In the event of the borrower’s death and if repayment within the required timeframe is uncertain, the loan is generally charged-off as soon as the amount of the loss is determined. For loans acquired through the completion of a transfer, including loans acquired in a business combination, that have evidence of deterioration of credit quality since origination and for which it is probable, at acquisition, that United will be unable to collect all contractually required payment receivable are initially recorded at fair value (as determined by the present value of expected future cash flows) with no valuation allowance. The difference between the undiscounted cash flows expected at acquisition and the investment in the loan, or the “accretable yield,” is recognized as interest income on a level-yield method over the life of the loan. Contractually required payments for interest and principal that exceed the undiscounted cash flows expected at acquisition, or the “nonaccretable difference,” are not recognized as a yield adjustment or as a loss accrual or a valuation allowance. Increases in expected cash flows subsequent to the initial investment are recognized prospectively through adjustment of the yield on the loan over its remaining life. Decreases in expected cash flows are recognized as impairment. Valuation allowances on these impaired loans reflect only losses incurred after the acquisition (meaning the present value of all cash flows expected at acquisition that ultimately are not to be received). The amount of provision for loan losses related to loans acquired that have evidence of deterioration of credit quality was $1,676,000, $5,321,000 and $1,915,000 for the years of 2016, 2015, and 2014, respectively. A progression of the allowance for loan losses, by portfolio segment, for the year ended December 31, 2016 and 2015 is summarized as follows: Allowance for Loan Losses and Carrying Amount of Loans For the Year Ended December 31, 2016 (In thousands) Commercial Real Other Residential Construction Consumer Allowance Total Owner- Nonowner- Allowance for Loan Losses: Beginning balance $ 3,637 $ 5,309 $ 31,328 $ 15,148 $ 18,205 $ 1,995 $ 104 $ 75,726 Charge-offs 5,281 419 20,430 4,597 2,659 2,794 0 36,180 Recoveries 3,071 675 3,452 639 433 446 0 8,716 Provision 3,846 1,318 18,737 2,580 (5,373) 3,158 243 24,509 Ending balance $ 5,273 $ 6,883 $ 33,087 $ 13,770 $ 10,606 $ 2,805 $ 347 $ 72,771 Ending Balance: individually evaluated for impairment $ 815 $ 2,524 $ 13,441 $ 3,431 $ 3,206 $ 0 $ 0 $ 23,417 Ending Balance: collectively evaluated for impairment $ 4,458 $ 4,359 $ 19,646 $ 10,339 $ 7,400 $ 2,805 $ 347 $ 49,354 Ending Balance: $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 Financing receivables: Ending balance $ 1,049,885 $ 3,425,453 $ 1,613,437 $ 2,403,437 $ 1,255,738 $ 608,769 $ 0 $ 10,356,719 Ending Balance: individually evaluated for impairment $ 18,976 $ 26,835 $ 56,091 $ 14,766 $ 8,152 $ 0 $ 0 $ 124,820 Ending Balance: collectively evaluated for impairment $ 1,005,999 $ 3,323,117 $ 1,527,479 $ 2,373,969 $ 1,221,006 $ 608,733 $ 0 $ 10,060,303 Ending Balance: $ 24,910 $ 75,501 $ 29,867 $ 14,702 $ 26,580 $ 36 $ 0 $ 171,596 Allowance for Loan Losses and Carrying Amount of Loans For the Year Ended December 31, 2015 (In thousands) Commercial Real Other Residential Construction Consumer Allowance Total Owner- Nonowner- Allowance for Loan Losses: Beginning balance $ 4,041 $ 8,167 $ 26,931 $ 13,835 $ 19,402 $ 3,083 $ 70 $ 75,529 Charge-offs 4,755 1,120 10,042 6,411 862 2,309 0 25,499 Recoveries 829 74 714 495 511 499 0 3,122 Provision 3,522 (1,812) 13,725 7,229 (846) 722 34 22,574 Ending balance $ 3,637 $ 5,309 $ 31,328 $ 15,148 $ 18,205 $ 1,995 $ 104 $ 75,726 Ending Balance: individually evaluated for impairment $ 1,253 $ 1,362 $ 18,269 $ 2,119 $ 4,789 $ 0 $ 0 $ 27,792 Ending Balance: collectively evaluated for impairment $ 2,384 $ 3,947 $ 13,059 $ 13,029 $ 13,416 $ 1,995 $ 104 $ 47,934 Ending Balance: loans acquired with deteriorated credit quality $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 Financing receivables: Ending balance $ 927,746 $ 2,896,367 $ 1,602,222 $ 2,268,685 $ 1,273,054 $ 430,878 $ 0 $ 9,398,952 Ending Balance: individually evaluated for impairment $ 12,670 $ 26,152 $ 35,342 $ 17,782 $ 15,779 $ 0 $ 0 $ 107,725 Ending Balance: collectively evaluated for impairment $ 888,802 $ 2,817,748 $ 1,546,018 $ 2,237,865 $ 1,221,760 $ 430,837 $ 0 $ 9,143,030 Ending Balance: loans acquired with deteriorated credit quality $ 26,274 $ 52,467 $ 20,862 $ 13,038 $ 35,515 $ 41 $ 0 $ 148,197 United maintains an allowance for loan losses and a reserve for lending-related commitments such as unfunded loan commitments and letters of credit. The reserve for lending-related commitments of $1,044,000 and $936,000 at December 31, 2016 and December 31, 2015, respectively, is separately classified on the balance sheet and is included in other liabilities. The combined allowance for loan losses and reserve for lending-related commitments are referred to as the allowance for credit losses. A progression of the allowance for credit losses, which includes the allowance for loan losses and the reserve for lending-related commitments, for the periods presented is summarized as follows: Year Ended December 31 (In thousands) 2016 2015 2014 Balance of allowance for loan losses at beginning of period $ 75,726 $ 75,529 $ 74,198 Provision for loan losses 24,509 22,574 21,937 100,235 98,103 96,135 Loans charged off 36,180 25,499 25,241 Less recoveries (8,716) (3,122) (4,635) Net charge-offs 27,464 22,377 20,606 Balance of allowance for loan losses at end of period $ 72,771 $ 75,726 $ 75,529 Reserve for lending-related commitments 1,044 936 1,518 Balance of allowance for credit losses at end of period $ 73,815 $ 76,662 $ 77,047

Bank Premises and Equipment and

Bank Premises and Equipment and Leases	12 Months Ended
	Dec. 31, 2016
Property, Plant and Equipment [Abstract]
Bank Premises and Equipment and Leases	NOTE G—BANK PREMISES AND EQUIPMENT AND LEASES Bank premises and equipment are summarized as follows: December 31 (In thousands) 2016 2015 Land $ 24,238 $ 24,497 Buildings and improvements 89,302 87,717 Leasehold improvements 33,194 26,875 Furniture, fixtures and equipment 65,598 60,233 212,332 199,322 Less allowance for depreciation and amortization 136,423 126,233 Net bank premises and equipment $ 75,909 $ 73,089 Depreciation expense was $7,889,000, $8,385,000 and $9,351,000 for years ending December 31, 2016, 2015 and 2014, respectively, while amortization expense was $136,000 for the years ended December 31, 2016, 2015 and 2014, respectively. United and certain banking subsidiaries have entered into various noncancelable-operating leases. These noncancelable operating leases are subject to renewal options under various terms and some leases provide for periodic rate adjustments based on cost-of-living index changes. Rent expense for noncancelable operating leases approximated $14,661,000, $12,528,000 and $12,610,000 for the years ended December 31, 2016, 2015 and 2014, respectively. Future minimum lease payments, by year and in the aggregate, under noncancelable operating leases with initial or remaining terms of one year or more, for years subsequent to December 31, 2016, consisted of the following: Year Amount (In thousands) 2017 $ 12,661 2018 11,653 2019 9,756 2020 7,427 2021 6,059 Thereafter 15,380 Total minimum lease payments $ 62,936

Goodwill and Other Intangibles

Goodwill and Other Intangibles	12 Months Ended
	Dec. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangibles	NOTE H—GOODWILL AND OTHER INTANGIBLES The following is a summary of intangible assets subject to amortization and those not subject to amortization: As of December 31, 2016 (In thousands) Gross Carrying Accumulated Net Carrying Amortized intangible assets: Core deposit intangible assets $ 69,635 $ (46,681) $ 22,954 Goodwill not subject to amortization $ 863,767 As of December 31, 2015 Gross Carrying Accumulated Net Carrying Amortized intangible assets: Core deposit intangible assets $ 60,577 $ (42,737) $ 17,840 Goodwill not subject to amortization $ 710,252 The following table provides a reconciliation of goodwill: Goodwill at December 31, 2015 $ 710,252 Reclassification to goodwill 670 Preliminary addition to goodwill from Bank of Georgetown acquisition 152,845 Goodwill at December 31, 2016 $ 863,767 The following table sets forth the anticipated amortization expense for intangible assets for the years subsequent to 2016: Year Amount (In thousands) 2017 $ 4,190 2018 3,707 2019 3,450 2020 3,252 2021 and thereafter 8,355

Deposits

Deposits	12 Months Ended
	Dec. 31, 2016
Banking and Thrift [Abstract]
Deposits	NOTE I—DEPOSITS The book value of deposits consisted of the following: (Dollars in thousands) December 31 2016 2015 Demand deposits $ 3,171,841 $ 2,699,958 Interest-bearing checking 1,778,156 1,683,316 Regular savings 721,224 692,079 Money market accounts 3,151,896 2,368,063 Time deposits under $100,000 693,005 794,428 Time deposits over $100,000 1,280,745 1,103,683 Total deposits $ 10,796,867 $ 9,341,527 Included in time deposits over $100,000 at December 31, 2016 and 2015 were time deposits of $250,000 or more of $357,468,000 and $386,484,000, respectively. Interest paid on deposits approximated $29,048,000, $28,447,000 and $26,925,000 in 2016, 2015 and 2014, respectively. United’s subsidiary banks have received deposits, in the normal course of business, from the directors and officers of United and its subsidiaries, and their associates. Such related party deposits were accepted on substantially the same terms, including interest rates and maturities, as those prevailing at the time for comparable transactions with unrelated persons. The aggregate dollar amount of these deposits was $92,310,000 and $174,790,000 at December 31, 2016 and 2015, respectively.

Short-Term Borrowings

Short-Term Borrowings	12 Months Ended
	Dec. 31, 2016
Debt Disclosure [Abstract]
Short-Term Borrowings	NOTE J—SHORT-TERM BORROWINGS At December 31, 2016 and 2015, short-term borrowings and the related weighted-average interest rates were as follows: 2016 2015 Weighted- Weighted- (Dollars in thousands) Average Average Amount Rate Amount Rate Federal funds purchased $ 22,235 0.65 % $ 22,230 0.25 % Securities sold under agreements to repurchase 187,316 (1) 0.25 % (1) 290,798 (1) 0.15 % (1) Total $ 209,551 $ 313,028 (1) Excludes a wholesale security sold under an agreement to repurchase assumed in the Virginia Commerce merger of $50,000 and $50,863, including an acquisition accounting adjustment to fair value, with an interest rate of 4.37% at December 31, 2016 and 2015, respectively, and scheduled to mature in May of 2018. Federal funds purchased and securities sold under agreements to repurchase have been a significant source of funds for the company. United has various unused lines of credit available from certain of its correspondent banks in the aggregate amount of $264,000,000. These lines of credit, which bear interest at prevailing market rates, permit United to borrow funds in the overnight market, and are renewable annually subject to certain conditions. The following table shows the distribution of United’s federal funds purchased and securities sold under agreements to repurchase and the weighted-average interest rates thereon at the end of each of the last three years. Also provided are the maximum amount of borrowings and the average amounts of borrowings as well as weighted-average interest rates for the last three years. The table does not include the long-term wholesale security sold under an agreement to repurchase mentioned above assumed in the Virginia Commerce merger. (Dollars in thousands) Federal Funds Purchased Securities Sold Under To Repurchase At December 31: 2016 $ 22,235 $ 187,316 2015 22,230 290,798 2014 53,840 381,812 Weighted-average interest rate at year-end: 2016 0.65 % 0.25 % 2015 0.25 % 0.15 % 2014 0.20 % 0.15 % Maximum amount outstanding at any month’s end: 2016 $ 32,200 $ 353,833 2015 52,000 379,818 2014 53,840 527,904 Average amount outstanding during the year: 2016 $ 22,717 $ 298,494 2015 38,526 283,011 2014 24,037 357,083 Weighted-average interest rate during the year: 2016 0.32 % 0.17 % 2015 0.21 % 0.10 % 2014 0.20 % 0.12 % At December 31, 2016, all the repurchase agreements were in overnight accounts. The rates offered on these funds vary according to movements in the federal funds and short-term United has a $20,000,000 line of credit with an unrelated financial institution to provide for general liquidity needs. The line is an unsecured, revolving line of credit. The line is renewable on a 360 day basis and carries an indexed, floating-rate of interest. The line requires compliance with various financial and nonfinancial covenants. At December 31, 2016, United had no outstanding balance under this credit. Interest paid on short-term borrowings approximated $1,587,000, $835,000 and $1,133,000 in 2016, 2015 and 2014, respectively.

Long-Term Borrowings

Long-Term Borrowings	12 Months Ended
	Dec. 31, 2016
Debt Disclosure [Abstract]
Long-Term Borrowings	NOTE K—LONG-TERM BORROWINGS United’s subsidiary banks are members of the Federal Home Loan Bank (FHLB). Membership in the FHLB makes available short-term and long-term borrowings from collateralized advances. All FHLB borrowings are collateralized by a mix of single-family residential mortgage loans, commercial loans and investment securities. At December 31, 2016, the total carrying value of loans pledged as collateral for FHLB advances approximated $4,447,061,000. United had an unused borrowing amount as of December 31, 2016 of approximately $2,803,186,000 available subject to delivery of collateral after certain trigger points. Advances may be called by the FHLB or redeemed by United based on predefined factors and penalties. At December 31, 2016 and 2015, FHLB advances and the related weighted-average interest rates were as follows: 2016 2015 (Dollars in thousands) Amount Weighted- Weighted- Amount Weighted- Weighted- FHLB advances $ 897,707 0.72 % 0.72 % $ 850,880 0.46 % 0.46 % No overnight funds were included in the $897,707,000 above at December 31, 2016. Overnight funds of $110,000,000 were included in the $850,880,000 above at December 31, 2015. The weighted-average effective rate considers the effect of any interest rate swaps designated as fair value hedges outstanding at year-end 2016 and 2015 to manage interest rate risk on its long-term debt. Additional information is provided in Note Q, Notes to Consolidated Financial Statements. A long-term wholesale security sold under an agreement to repurchase was assumed in the Virginia Commerce merger. At December 31, 2016 and 2015, the balance of the wholesale security sold under an agreement to repurchase was $50,000,000 and $50,863,000, respectively. The repurchase agreement had an interest rate of 4.37% at December 31, 2016 and 2015 and is scheduled to mature in May of 2018. At December 31, 2016, United had a total of thirteen statutory business trusts that were formed for the purpose of issuing or participating in pools of trust preferred capital securities (Capital Securities) with the proceeds invested in junior subordinated debt securities (Debentures) of United. The Debentures, which are subordinate and junior in right of payment to all present and future senior indebtedness and certain other financial obligations of United, are the sole assets of the trusts and United’s payment under the Debentures is the sole source of revenue for the trusts. At December 31, 2016 and 2015, the outstanding balance of the Debentures was $224,319,000 and $223,506,000, respectively, and was included in the category of long-term debt on the Consolidated Balance Sheets entitled “Other long-term borrowings.” The Capital Securities are not included as a component of shareholders’ equity in the Consolidated Balance Sheets. United fully and unconditionally guarantees each individual trust’s obligations under the Capital Securities. Under the provisions of the subordinated debt, United has the right to defer payment of interest on the subordinated debt at any time, or from time to time, for periods not exceeding five years. If interest payments on the subordinated debt are deferred, the dividends on the Capital Securities are also deferred. Interest on the subordinated debt is cumulative. The Trust Preferred Securities currently qualify as Tier 1 regulatory capital of United for regulatory purposes. In July of 2013, United’s primary federal regulator, the Federal Reserve, published final rules (the “Basel III Capital Rules”) establishing a new comprehensive capital framework for U.S. banking organizations. The Basel III Capital Rules grandfathers United’s Trust Preferred Securities as Tier 1 capital under the limitations for restricted capital elements in the general risk-based capital rules. As a result, beginning in 2015, United’s Trust Preferred Securities was subject to a limit of 25 percent of Tier 1 capital elements excluding any non-qualifying capital instruments and after all regulatory capital deductions and adjustments applied to Tier 1 capital, which is substantially similar to the limit in the general risk-based capital rules. Trust preferred securities no longer included in United’s Tier 1 capital may be included as a component of Tier 2 capital on a permanent basis without phase-out. Information related to United’s statutory trusts is presented in the table below: (Dollars in thousands) Description Issuance Date Amount of Interest Rate Maturity Date Century Trust March 23, 2000 $ 8,800 10.875% Fixed March 8, 2030 United Statutory Trust III December 17, 2003 $ 20,000 3-month LIBOR + 2.85% December 17, 2033 United Statutory Trust IV December 19, 2003 $ 25,000 3-month LIBOR + 2.85% January 23, 2034 United Statutory Trust V July 12, 2007 $ 50,000 3-month LIBOR + 1.55% October 1, 2037 United Statutory Trust VI September 20, 2007 $ 30,000 3-month LIBOR + 1.30% December 15, 2037 Premier Statutory Trust II September 25, 2003 $ 6,000 3-month LIBOR + 3.10% October 8, 2033 Premier Statutory Trust III May 16, 2005 $ 8,000 3-month LIBOR + 1.74% June 15, 2035 Premier Statutory Trust IV June 20, 2006 $14,000 3-month LIBOR + 1.55% September 23, 2036 Premier Statutory Trust V December 14, 2006 $10,000 3-month LIBOR + 1.61% March 1, 2037 Centra Statutory Trust I September 20, 2004 $10,000 3-month LIBOR + 2.29% September 20, 2034 Centra Statutory Trust II June 15, 2006 $10,000 3-month LIBOR + 1.65% July 7, 2036 Virginia Commerce Trust II December 19, 2002 $15,000 6-month LIBOR + 3.30% December 19, 2032 Virginia Commerce Trust III December 20, 2005 $25,000 3-month LIBOR + 1.42% February 23, 2036 At December 31, 2016 and 2015, the Debentures and their related weighted-average interest rates were as follows: 2016 2015 (Dollars in thousands) Amount Weighted- Amount Weighted- Century Trust $ 8,800 10.88 % $ 8,800 10.88 % United Statutory Trust III 20,619 3.84 % 20,619 3.38 % United Statutory Trust IV 25,774 3.74 % 25,774 3.17 % United Statutory Trust V 51,547 2.40 % 51,547 1.88 % United Statutory Trust VI 30,928 2.26 % 30,928 1.81 % Premier Statutory Trust II 6,186 3.98 % 6,186 3.42 % Premier Statutory Trust III 8,248 2.70 % 8,248 2.25 % Premier Statutory Trust IV 14,433 2.55 % 14,433 2.14 % Premier Statutory Trust V 10,310 2.54 % 10,310 2.02 % Centra Statutory Trust I 10,000 3.29 % 9,972 2.86 % Centra Statutory Trust II 10,000 2.53 % 9,972 1.97 % Virginia Commerce Trust II 11,784 4.62 % 11,554 4.13 % Virginia Commerce Trust III 15,690 2.34 % 15,163 1.80 % Total $ 224,319 $ 223,506 At December 31, 2016, the scheduled maturities of long-term borrowings were as follows: Year Amount (In thousands) 2017 $ 825,606 2018 59,628 2019 34,243 2020 0 2021 and thereafter 252,549 Total $ 1,172,026 Interest paid on long-term borrowings approximated $13,974,000, $10,553,000 and $13,954,000 in 2016, 2015 and 2014, respectively.

Other Expense

Other Expense	12 Months Ended
	Dec. 31, 2016
Other Income and Expenses [Abstract]
Other Expense	NOTE L—OTHER EXPENSE The following details certain items of other expense for the periods indicated: Year Ended December 31 (In thousands) 2016 2015 2014 Legal, consulting & other professional services $ 9,763 $ 9,310 $ 9,620 Franchise & other taxes not on income 7,778 7,055 7,513 Automated Teller Machine (ATM) expenses 7,365 7,107 6,626

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Income Taxes	NOTE M—INCOME TAXES The income tax provisions included in the consolidated statements of income are summarized as follows: (In thousands) Year Ended December 31 2016 2015 2014 Current (benefit) expense: Federal $ 63,169 $ 58,373 $ 51,001 State 5,154 5,428 3,900 Deferred expense: Federal and State 7,252 1,729 10,097 Total income taxes $ 75,575 $ 65,530 $ 64,998 The following is a reconciliation of income tax expense to the amount computed by applying the statutory federal income tax rate to income before income taxes. Year Ended December 31 (Dollars in thousands) 2016 2015 2014 Amount % Amount % Amount % Tax on income before taxes at statutory federal rate $ 77,930 35.0% $ 71,222 35.0% $ 68,210 35.0% Plus: State income taxes net of federal tax benefits 4,084 1.8 3,516 1.7 2,523 1.3 82,014 36.8 74,738 36.7 70,733 36.3 Increase (decrease) resulting from: Tax-exempt interest income (3,919 ) (1.8 ) (4,158 ) (2.0 ) (4,048 ) (2.1 ) Historic tax credit 0 0.0 (1,262 ) (0.6 ) 0 0.0 Other items-net (2,520 ) (1.1 ) (3,788 ) (1.9 ) (1,687 ) (0.8 ) Income taxes $ 75,575 33.9% $ 65,530 32.2% $ 64,998 33.4% For years ended 2016, 2015 and 2014, United incurred federal income tax expense applicable to the sales and calls of securities of $114,000, $73,000 and $1,178,000, respectively. Income taxes paid approximated $61,905,000, $52,319,000, and $60,431,000 in 2016, 2015 and 2014, respectively. Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. At December 31, 2016, United had no federal or state net operating loss carryforwards. Taxes not on income, which consists mainly of business franchise taxes, were $7,778,000, $7,055,000 and 7,513,000 for the years ended December 31, 2016, 2015 and 2014, respectively. These amounts are recorded in other expense in the Consolidated Statements of Income. Significant components of United’s deferred tax assets and liabilities (included in other assets in the Consolidated Balance Sheets) at December 31, 2016 and 2015 are as follows: (In thousands) 2016 2015 Deferred tax assets: Allowance for credit losses $ 26,941 $ 27,874 Other accrued liabilities 3,478 929 Unrecognized components of net periodic pension costs 20,166 20,901 Unrealized loss on securities available for sale 1,436 2,210 Premises and equipment 93 0 Other real estate owned 6,724 7,500 Deferred mortgage points 0 3,575 Purchase accounting intangibles 41,392 15,248 Total deferred tax assets 100,230 78,237 Deferred tax liabilities: Deferred mortgage points 3,608 0 Accrued benefits payable 4,061 5,438 Premises and equipment 0 301 Other 13,687 1,856 Total deferred tax liabilities 21,356 7,595 Net deferred tax assets $ 78,874 $ 70,642 At December 31, 2016 and 2015, United believes that all of the deferred tax amounts shown above are more likely than not to be realized based on an assessment of all available positive and negative evidence and therefore no valuation allowance has been recorded. In accordance with ASC topic 740, “Income Taxes,” United records a liability for uncertain income tax positions based on a recognition threshold of more-likely-than-not, and a measurement attribute for all tax positions taken on a tax return, in order for those tax positions to be recognized in the financial statements. Below is a reconciliation of the total amounts of unrecognized tax benefits: December 31 (In thousands) 2016 2015 Unrecognized tax benefits at beginning of year $ 2,102 $ 3,453 Increase in unrecognized tax benefits as a result of tax positions taken during the current period 673 207 Decreases in the unrecognized tax benefits as a result of a lapse of the applicable statute of limitations (333) (1,558) Unrecognized tax benefits at end of year $ 2,442 $ 2,102 The entire amount of unrecognized tax benefits, if recognized, would impact United’s effective tax rate. Over the next 12 months, the statute of limitations will close on certain income tax returns. However, at this time, United cannot reasonably estimate the amount of tax benefits, if any, it may recognize over the next 12 months. United is currently open to audit under the statute of limitations by the Internal Revenue Service for the years ended December 31, 2013, 2014 and 2015 and certain State Taxing authorities for the years ended December 31, 2013 through 2015. As of December 31, 2016 and 2015, the total amount of accrued interest related to uncertain tax positions was $569,000 for both time periods. United accounts for interest and penalties related to uncertain tax positions as part of its provision for federal and state income taxes. No interest or penalties were recognized in the results of operations for the years of 2016, 2015 and 2014.

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2016
Compensation and Retirement Disclosure [Abstract]
Employee Benefit Plans	NOTE N—EMPLOYEE BENEFIT PLANS United has a defined benefit retirement plan covering a majority of all employees. Pension benefits are based on years of service and the average of the employee’s highest five consecutive plan years of basic compensation paid during the ten plan years preceding the date of determination. Contributions by United are intended to provide not only for benefits attributed to service to date, but also for those expected to be earned in the future. In September of 2007, after a recommendation by United’s Pension Committee and approval by United’s Board of Directors, the United Bankshares, Inc. Pension Plan (the Plan) was amended to change the participation rules. The decision to change the participation rules for the Plan followed current industry trends, as many large and medium size companies have taken similar steps. The amendment provided that employees hired on or after October 1, 2007, will not be eligible to participate in the Plan. However, new employees will continue to be eligible to participate in United’s Savings and Stock Investment 401(k) plan. This change had no impact on current employees hired prior to October 1, 2007 as they will continue to participate in the Plan, with no change in benefit provisions, and will continue to be eligible to participate in United’s Savings and Stock Investment 401(k) Plan. As of December 31, 2016, United changed the method used to estimate the interest cost component of net periodic benefit cost for the Plan. Under the previous method, appropriate spot rates were used to discount the projected benefit obligation (PBO) cash flows based on date of measurement. Then, a single aggregated discount rate was calculated such that the present value of the PBO remained the same. This rate is technically a weighted-average of the spot rates. This single discount rate was applied to the interest and service costs as well. Under the full yield curve approach, separate discount rates are used to calculate the present value for each projected cash flow. That is, individual spot rates are applied to the cash flows in each time period. This does not have any impact on the present value of the PBO as the PBO was originally discounted with spot rates. The adoption of this method concerns the manner in which it affects interest and service costs. Interest costs typically decrease when using this method because of the different weightings applied to the cash flows; that is, interest costs closer to the current period will be discounted with a smaller rate than those further in the future based on a typical yield curve, and greater future Interest Costs values are discounted with greater longer-term spot rates. Similarly, service costs typically have longer durations and will thus be subject to longer-term spot rates, decreasing the present value of these costs. As a result, the full yield curve method is preferable as it provides a more granular, and thus a more accurate, determination of costs. This new method constitutes a change in an accounting estimate under the provisions of ASC topic 250, “Accounting Changes and Error Corrections,” that is inseparable from a change in accounting principle and was accounted for prospectively, with the resulting change impacting the recognition of net periodic pension cost beginning January 1, 2017. There was no impact to net periodic pension cost for 2016. Net consolidated periodic pension cost included the following components: (Dollars in thousands) Year Ended December 31, 2016 2015 2014 Service cost $ 2,374 $ 2,787 $ 2,160 Interest cost 5,950 5,902 5,379 Expected return on plan assets (8,089) (9,290) (9,102) Recognized net actuarial loss 4,921 4,980 1,994 Amortization of prior service cost 0 1 1 Net periodic pension cost $ 5,156 $ 4,380 $ 432 Weighted-Average Assumptions: Discount rate 4.75% 4.35% 5.20% Expected return on assets 7.25% 7.50% 7.50% Rate of Compensation Increase (prior to age 45) 3.50% 3.50% 3.50% Rate of Compensation Increase (otherwise) 3.00% 3.00% 3.00% Amounts related to the Plan recognized as a component of other comprehensive income were as follows: (Dollars in thousands) Year Ended December 31, 2016 2015 2014 Net actuarial loss $ 2,914 $ 2,402 $ 29,419 Amortization of: Prior service cost 0 (1) (1) Actuarial loss (4,921) (4,980) (1,994) Total recognized in other comprehensive income $ (2,007) $ (2,579) $ 27,424 Included in accumulated other comprehensive income at December 31, 2016 are unrecognized actuarial losses of $53,991,000 ($34,014,000 net of tax) that have not yet been recognized in net periodic pension cost. The amortization of this item expected to be recognized in net periodic pension cost during the fiscal year ended December 31, 2017 is $4,411,000 ($2,779,000 net of tax). The reconciliation of the beginning and ending balances of the projected benefit obligation and the fair value of plan assets for the years ended December 31, 2016 and 2015 and the accumulated benefit obligation at December 31, 2016 and 2015 are as follows: (Dollars in thousands) December 31, 2016 2015 Change in Projected Benefit Obligation Projected Benefit Obligation at the Beginning of the Year $ 125,403 $ 135,739 Service Cost 2,374 2,787 Interest Cost 5,950 5,902 Actuarial Loss (Gain) 5,114 (9,760 ) Benefits Paid (4,326 ) (9,265 ) Projected Benefit at the End of the Year $ 134,515 $ 125,403 Accumulated Benefit Obligation at the End of the Year $ 121,548 $ 113,679 Change in Plan Assets Fair Value of Plan Assets at the Beginning of the Year $ 113,748 $ 125,885 Actual Return on Plan Assets 10,289 (2,872 ) Benefits Paid (4,326 ) (9,265 ) Employer Contributions 0 0 Fair value of plan assets at end of year $ 119,711 $ 113,748 Net Amount Recognized Funded Status $ (14,804 ) $ (11,655 ) Unrecognized Transition Asset 0 0 Unrecognized Prior Service Cost 0 0 Unrecognized Net Loss 53,991 55,998 Net Amount Recognized $ 39,187 $ 44,343 Weighted-Average Assumptions at the End of the Year Discount Rate 4.49 % 4.75 % Rate of Compensation Increase (prior to age 45) 3.50 % 3.50 % Rate of Compensation Increase (otherwise) 3.00 % 3.00 % Asset allocation for the defined benefit pension plan as of the measurement date, by asset category, is as follows: Plan Assets Target Allocation 2017 Allowable Allocation Range Percentage of Plan Assets at December 31, December 31, Equity Securities 66 % 50-70 % 71 % 67% Debt Securities 26 % 20-50 % 26 % 22% Other 8 % 3-15 % 3 % 11% Total 100 % 100% Equity securities include United common stock in the amounts of $4,894,000 (4%) at December 31, 2016 and $3,915,000 (3%) at December 31, 2015 . The policy, as established by the Pension Committee, primarily consisting of United’s Executive Management, is to invest assets based upon the target allocations stated above. The assets are reallocated periodically to meet the above target allocations. The investment policy is reviewed at least annually, subject to the approval of the Pension Committee, to determine if the policy should be changed. Prohibited investments include, but are not limited to, futures contracts, private placements, uncovered options, real estate, the use of margin, short sales, derivatives for speculative purposes, and other investments that are speculative in nature. In order to achieve a prudent level of portfolio diversification, the securities of any one company are not to exceed 10% of the total plan assets, and no more than the 15% of total plan assets is to be invested in any one industry (other than securities of U.S. Government or Agencies). Additionally, no more than 15% of the plan assets is to be invested in foreign securities, both equity and fixed. The expected long-term rate of return for the plan’s total assets is based on the expected return of each of the above categories, weighted based on the median of the target allocation for each class. United uses the corridor approach based on 10% of the greater of the projected benefit obligation and the market-related value of plan assets to amortize actuarial gains and losses. At December 31, 2016, the benefits expected to be paid in each of the next five fiscal years, and in the aggregate for the five years thereafter are as follows: Year Amount (In thousands) 2017 $ 4,626 2018 4,908 2019 5,217 2020 5,568 2021 5,947 2022 through 2026 35,277 United did not contribute to the plan in 2016 and 2015 as no contributions were required by funding regulations or law. For 2017, no contributions to the plan are required by funding regulations or law. However, United may make a discretionary contribution in 2017, the amount of which cannot be reasonably estimated at this time. In accordance with ASC topic 715 and using the guidance contained in ASC topic 820, the following is a description of the valuation methodologies used to measure the plan assets at fair value. Cash and Cash Equivalents: Debt Securities Common and Preferred Stock: Mutual Funds: The following tables present the balances of the plan assets, by fair value hierarchy level, as of December 31, 2016 and 2015: Fair Value Measurements at December 31, 2016 Using (In thousands) Description Balance as of December 31, 2016 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash and Cash equivalents $ 1,778 $ 1,778 $ 0 $ 0 Fixed Income Securities: Mortgage backed securities 47 0 47 0 Collateralized mortgage obligations 48 0 48 0 Municipal obligations 670 0 670 0 Corporate bonds 1,169 0 1,169 0 Foreign bonds, notes and debentures 96 0 96 0 Fixed Income Mutual Funds: Taxable 26,816 26,816 0 0 Alternative 3,898 3,898 0 0 Equity Securities: Common stock 20,629 20,629 0 0 Equity Mutual Funds: Domestic equity large cap 23,063 23,063 0 0 Domestic equity mid cap 6,457 6,457 0 0 Domestic equity small cap 13,087 13,087 0 0 Domestic equity other 910 910 0 0 International emerging equity 3,120 3,120 0 0 International equity developed 12,619 12,619 0 0 Alternative equity 3,456 3,456 0 0 Domestic Balanced Mutual Funds 1,848 1,848 0 0 Total $ 119,711 $ 117,681 $ 2,030 $ 0 Fair Value Measurements at December 31, 2015 Using (In thousands) Description Balance as of December 31, Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash and Cash equivalents $ 1,467 $ 1,467 $ 0 $ 0 Fixed Income Securities: Mortgage backed securities 63 0 63 0 Collateralized mortgage obligations 54 0 54 0 Municipal obligations 836 0 836 0 Corporate bonds 1,539 0 1,539 0 Foreign bonds, notes and debentures 93 0 93 0 Fixed Income Mutual Funds: Taxable 22,843 22,843 0 0 Alternative 5,067 5,067 0 0 Equity Securities: Common stock 20,464 20,464 0 0 Equity Mutual Funds: Domestic equity large cap 20,470 20,470 0 0 Domestic equity mid cap 5,804 5,804 0 0 Domestic equity small cap 14,080 14,080 0 0 International emerging equity 6,044 6,044 0 0 International equity developed 8,772 8,772 0 0 Alternative equity 6,152 6,152 0 0 Total $ 113,748 $ 111,163 $ 2,585 $ 0 Common stock investments are diversified amongst various industries with no industry representing more than 5% of the total plan assets. The United Bankshares, Inc. Savings and Stock Investment Plan (the Plan) is a defined contribution plan under Section 401(k) of the Internal Revenue Code. Each employee of United, who completes ninety (90) days of qualified service, is eligible to participate in the Plan. Each participant may contribute from 1% to 100% of compensation to his/her account, subject to Internal Revenue Service maximum deferral limits. Prior to December 31, 2008, after one year of eligible service, United matched 100% of the first 2% of salary deferred and 25% of the second 2% of salary deferred with United stock. Beginning January 1, 2009, United matched 100% of the first 3% of salary deferred and 25% of the next 1% of salary deferred with United stock. Vesting is 100% for employee deferrals and the company match at the time the employee makes his/her deferral. United’s expense relating to the Plan approximated $2,069,000, $1,894,000, and $1,761,000 in 2016, 2015 and 2014, respectively. The assets of United’s defined benefit plan and 401(k) Plan each include investments in United common stock. At December 31, 2016 and 2015, the combined plan assets included 893,440 and 876,989 shares, respectively, of United common stock with an approximate fair value of $41,322,000 and $32,440,000, respectively. Dividends paid on United common stock held by the plans approximated $1,173,000, $1,139,000 and $1,133,000 for the years ended December 31, 2016, 2015, and 2014, respectively. United has certain other supplemental deferred compensation plans covering various key employees. Periodic charges are made to operations so that the liability due each employee is fully recorded as of the date of their retirement. Amounts charged to expense have not been significant in any year.

Stock Based Compensation

Stock Based Compensation	12 Months Ended
	Dec. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Based Compensation	NOTE O—STOCK BASED COMPENSATION On May 18, 2016, United’s shareholders approved the 2016 Long-Term Incentive Plan (2016 LTI Plan). The 2016 LTI Plan became effective as of May 18, 2016. An award granted under the 2016 LTI Plan may consist of any non-qualified stock options or incentive stock options, stock appreciation rights (SARs), restricted stock, restricted stock units, performance units or other-stock-based award. These awards all relate to the common stock of United. The maximum number of shares of United common stock which may be issued under the 2016 LTI Plan is 1,700,000. The 2016 LTI Plan will be administered by a board committee appointed by United’s Board of Directors (the Board). Unless otherwise determined by the Board, the Compensation Committee of the Board (the Committee) shall administer the 2016 LTI Plan. Any and all shares may be issued in respect of any of the types of Awards, provided that (1) the aggregate number of shares that may be issued in respect of restricted stock awards, and restricted stock unit awards which are settled in shares is 500,000, and (2) the aggregate number of shares that may be issued pursuant to stock options is 1,200,000. The shares to be offered under the 2016 LTI Plan may be authorized and unissued shares or treasury shares. The maximum number of options and SARs, in the aggregate, which may be awarded to any individual key employee during any calendar year is 100,000. The maximum number of stock options and SARs, in the aggregate, which may be awarded to any non-employee director during any calendar year is 10,000. The maximum number of shares of restricted stock or shares subject to a restricted stock units award that may be granted during any calendar year is 50,000 shares to any individual key employee and 5,000 shares to any individual non-employee director. Subject to certain change in control provisions, the 2016 LTI Plan provides that awards of restricted stock and restricted stock units will vest as the Committee determines in the award agreement, provided that no awards will vest sooner than 1/3 per year over the first three anniversaries of the award. Awards granted to executive officers of United typically will have performance based vesting conditions. A Form S-8 was filed on July 29, 2016 with the Securities and Exchange Commission to register all the shares which were available for the 2016 LTI Plan. The 2016 LTI Plan replaces the 2011 Long-Term Incentive Plan (2011 LTI Plan) which expired during the second quarter of 2016. A total of 967,285 stock options and 289,637 restricted shares of common stock were granted under the 2011 LTI Plan. Compensation expense of $2,817,000, $2,484,000, and $2,195,000 related to the nonvested awards under the 2011 LTI Plan and the 2006 Stock Option Plan was incurred for the years 2016, 2015 and 2014, respectively. Compensation expense was included in employee compensation in the Consolidated Statements of Income. Stock Options United currently has options outstanding from various option plans other than the 2011 LTI Plan (the Prior Plans); however, no common shares of United stock are available for grants under the Prior Plans as these plans have expired. Awards outstanding under the Prior Plans will remain in effect in accordance with their respective terms. The maximum term for options granted under the plans is ten (10) years. The fair value of the options for 2016 was estimated at the date of grant using a binomial lattice option pricing model with the following weighted-average assumptions: risk-free interest rates of 1.47%; dividend yield of 3.00%; volatility factors of the expected market price of United’s common stock of 0.281; and a weighted-average expected option life of 6.90 years, respectively. The estimated fair value of the options at the date of grant was $6.97 for the options granted during 2016. ASC topic 718, “Compensation – Stock Compensation” defines a lattice model as a model that produces an estimated fair value based on the assumed changes in prices of a financial instrument over successive periods of time. A binomial lattice model assumes at least two price movements are possible in each period of time. A summary of activity under the United’s stock option plans as of December 31, 2016, and the changes during the year of 2016 are presented below: Year ended December 31, 2016 Weighted Average (Dollars in thousands, except per share data) Aggregate Remaining Intrinsic Contractual Exercise Shares Value Term (Yrs.) Price Outstanding at January 1, 2016 1,207,110 $ 28.15 Assumed in acquisition of subsidiary 561,570 17.90 Granted 189,780 35.04 Exercised 519,482 19.76 Forfeited or expired 27,243 30.80 Outstanding at December 31, 2016 1,411,735 $ 25,695 5.8 $ 28.05 Exercisable at December 31, 2016 981,457 $ 20,294 4.7 $ 25.57 The following table summarizes the status of United’s nonvested awards for the year ended December 31, 2016: Shares Weighted-Average Nonvested at January 1, 2016 426,395 $ 6.68 Granted 189,780 6.97 Vested 167,683 6.58 Forfeited or expired 18,214 6.84 Nonvested at December 31, 2016 430,278 $ 6.84 As of December 31, 2016, the total unrecognized compensation cost related to nonvested option awards was $1,951,000 with a weighted-average expense recognition period of 1.2 years. The total fair value of awards vested during the year ended December 31, 2016, was $1,104,000. Cash received from options exercised under the Plans for the years ended December 31, 2016, 2015 and 2014 was $13,337,000, $7,871,000, and $9,878,000, respectively. During 2016 and 2015, 519,482 and 259,454 shares, respectively, were issued in connection with stock option exercises. All shares issued in connection with stock option exercises for 2016 and 2015 were issued from authorized and unissued stock. The weighted-average grant-date fair value of options granted in the year of 2016, 2015, and 2014 was $6.97, $7.23, and $6.42, respectively. The total intrinsic value of options exercised under the Plans during the years ended December 31, 2016, 2015, and 2014 was $11,001,000, $2,380,000, and $4,832,000, respectively. ASC topic 230, “Statement of Cash Flows,” requires the benefits of tax deductions in excess of recognized compensation cost to be reported as a financing cash flow, rather than as an operating cash flow as required under previous standards. This requirement reduces net operating cash flows and increase net financing cash flows. While the company cannot estimate what those amounts will be in the future (because they depend on, among other things, the date employees exercise stock options), United recognized cash flows from financing activities of $4,008,000, $1,023,000 and $73,000 from excess tax benefits related to share-based compensation arrangements for the year of 2016, 2015 and 2014, respectively. Restricted Stock Under the 2011 LTI Plan, United may award restricted common shares to key employees and non-employee directors. Restricted shares granted to participants have a four-year time-based vesting period. Recipients of restricted shares do not pay any consideration to United for the shares, have the right to vote all shares subject to such grant and receive all dividends with respect to such shares, whether or not the shares have vested. Presently, these nonvested participating securities have an immaterial impact on diluted earnings per share. As of December 31, 2016, the total unrecognized compensation cost related to nonvested stock awards was $2,986,000 with a weighted-average expense recognition period of 1.2 years. The following summarizes the changes to United’s restricted common shares for the year ended December 31, 2016: Number of Weighted-Average Outstanding at January 1, 2016 129,772 $ 31.69 Granted 64,092 35.04 Vested 50,641 30.56 Forfeited 5,955 32.97 Outstanding at December 31, 2016 137,268 $ 33.61

Commitments and Contingent Liab

Commitments and Contingent Liabilities	12 Months Ended
	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingent Liabilities	NOTE P—COMMITMENTS AND CONTINGENT LIABILITIES United 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 alter its own exposure to fluctuations in interest rates. These financial instruments include loan commitments, standby letters of credit, and interest rate swap agreements. The instruments involve, to varying degrees, elements of credit and interest rate risk in excess of the amount recognized in the financial statements. United’s maximum exposure to credit loss in the event of nonperformance by the counterparty to the financial instrument for the loan commitments and standby letters of credit is the contractual or notional amount of those instruments. United uses the same policies in making commitments and conditional obligations as it does for on-balance sheet instruments. Collateral may be obtained, if deemed necessary, based on management’s credit evaluation of the counterparty. Commitments to extend credit are agreements to lend to a customer as long as there is no violation of any condition established in the commitment contract. Commitments generally have fixed expiration dates or other termination clauses and may require the payment of a fee. Since many of the commitments are expected to expire without being drawn upon, the total commitment amounts do not necessarily, and historically do not, represent future cash requirements. The amount of collateral obtained, if deemed necessary upon the extension of credit, is based on management’s credit evaluation of the counterparty. United had approximately $2,823,396,000 and $2,587,957,000 of loan commitments outstanding as of December 31, 2016 and 2015, respectively, the majority of which contractually expire within one year. Commercial and standby letters of credit are agreements used by United’s customers as a means of improving their credit standing in their dealings with others. Under these agreements, United guarantees certain financial commitments of its customers. A commercial letter of credit is issued specifically to facilitate trade or commerce. Typically, under the terms of a commercial letter of credit, a commitment is drawn upon when the underlying transaction is consummated as intended between the customer and a third party. As of December 31, 2016 and 2015, United had $9,000 and $226,000, respectively, of outstanding commercial letters of credit. A standby letter of credit is generally contingent upon the failure of a customer to perform according to the terms of an underlying contract with a third party. United has issued standby letters of credit of $121,584,000 and $135,146,000 as of December 31, 2016 and 2015, respectively. In accordance with ASC topic 450, “Contingencies,” United has determined that substantially all of its letters of credit are renewed on an annual basis and the fees associated with these letters of credit are immaterial. United and its subsidiaries are currently involved in various legal proceedings and regulatory inquiries and examinations in the normal course of business. Management is vigorously pursuing all its legal and factual defenses and, after consultation with legal counsel, believes that all such litigation will be resolved with no material effect on United’s financial position.

Derivative Financial Instrument

Derivative Financial Instruments	12 Months Ended
	Dec. 31, 2016
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Financial Instruments	NOTE Q—DERIVATIVE FINANCIAL INSTRUMENTS United uses derivative instruments to help aid against adverse price changes or interest rate movements on the value of certain assets or liabilities and on future cash flows. These derivatives may consist of interest rate swaps, caps, floors, collars, futures, forward contracts, written and purchased options. United also executes derivative instruments with its commercial banking customers to facilitate its risk management strategies. Derivative instruments designated in a hedge relationship to mitigate exposure to changes in the fair value of an asset, liability, or firm commitment attributable to a particular risk, such as interest rate risk, are considered fair value hedges. Derivative instruments designated in a hedge relationship to mitigate exposure to variability in expected future cash flows, or other types of forecasted transactions, are considered cash flow hedges. As of December 31, 2016, United has only fair value hedges. For the years ended December 31, 2016 and 2015, the derivative portfolio also included derivative financial instruments not included in hedge relationships. These derivatives consist of interest rate swaps used for interest rate management purposes and derivatives executed with commercial banking customers to facilitate their interest rate management strategies. Gains and losses on other derivative financial instruments are netted in noninterest income. The following table sets forth certain information regarding interest rate derivatives portfolio used for interest-rate risk management purposes and designated as accounting hedges at December 31, 2016 and 2015. Derivative Hedging Instruments December 31, 2016 December 31, 2015 (Dollars in thousands) Notional Amount Average Pay Rate Notional Amount Average Pay Rate Fair Value Hedges: Pay Fixed Swap (Hedging Commercial Loans) $ 94,582 3.64 % $ 97,157 3.64 % Total Derivatives Used in Fair Value Hedges $ 94,582 $ 97,157 Total Derivatives Used for Interest Rate Risk Management and Designated as Hedges $ 94,582 $ 97,157 The following tables summarize the fair value of United’s derivative financial instruments: Asset Derivatives December 31, 2016 December 31, 2015 (In thousands) Balance Sheet Location Fair Value Balance Sheet Location Fair Value Derivatives designated as hedging instruments Interest rate contracts Other assets $ 24 Other assets $ 0 Total derivatives designated as hedging instruments $ 24 $ 0 Derivatives not designated as hedging instruments Interest rate contracts Other assets $ 2,267 Other assets $ 2,942 Total derivatives not designated as hedging instruments $ 2,267 $ 2,942 Total asset derivatives $ 2,291 $ 2,942 Liability Derivatives December 31, 2016 December 31, 2015 (In thousands) Balance Sheet Location Fair Value Balance Sheet Location Fair Value Derivatives designated as hedging instruments Interest rate contracts Other liabilities $ 338 Other liabilities $ 1,179 Total derivatives designated as hedging instruments $ 338 $ 1,179 Derivatives not designated as hedging instruments Interest rate contracts Other liabilities $ 2,267 Other liabilities $ 2,942 Total derivatives not designated as hedging instruments $ 2,267 $ 2,942 Total liability derivatives $ 2,605 $ 4,121 Derivative contracts involve the risk of dealing with both bank customers and institutional derivative counterparties and their ability to meet contractual terms. Credit risk arises from the possible inability of counterparties to meet the terms of their contracts. United’s exposure is limited to the replacement value of the contracts rather than the notional amount of the contract. The Company’s agreements generally contain provisions that limit the unsecured exposure up to an agreed upon threshold. Additionally, the Company attempts to minimize credit risk through certain approval processes established by management. The effect of United’s derivative financial instruments on its Consolidated Statements of Income for the years ended December 31, 2016, 2015 and 2014 is presented as follows: Year Ended (In thousands) Income Statement Location December 31, December 31, December 31, Derivatives in fair value hedging relationships Interest rate contracts Interest income/(expense) $ (30 ) $ (813 ) $ (1,047 ) Total derivatives in fair value hedging relationships $ (30 ) $ (813 ) $ (1,047 ) Derivatives not designated as hedging instruments Interest rate contracts (1) Other income $ 0 $ 0 $ 0 Total derivatives not designated as hedging instruments $ 0 $ 0 $ 0 Total derivatives $ (30) $ (813) $ (1,047) (1) Represents net gains and net losses from derivative assets not designated as hedging instruments. For the years ended December 31, 2016, 2015 and 2014, changes in the fair value of any interest rate swaps attributed to hedge ineffectiveness were recorded, but not significant to United’s Consolidated Statements of Income.

Comprehensive Income

Comprehensive Income	12 Months Ended
	Dec. 31, 2016
Equity [Abstract]
Comprehensive Income	NOTE R—COMPREHENSIVE INCOME The changes in accumulated other comprehensive income are as follows: For the Years Ended December 31 (In thousands) 2016 2015 2014 Net Income $ 147,083 $ 137,959 $ 129,888 Available for sale (“AFS”) securities: AFS securities with OTTI charges during the period (77) (113) (6,478) Related income tax effect 28 41 2,267 Income tax rate change 208 316 0 Less : OTTI charges recognized in net income 33 47 6,478 Related income tax benefit (12) (17) (2,267) Reclassification of previous noncredit OTTI to credit OTTI 415 0 8,413 Related income tax benefit (150) 0 (2,944) Net unrealized gains on AFS securities with OTTI 445 274 5,469 AFS securities – all other: Change in net unrealized (losses) gains on AFS securities arising during the period (12,931) (6,672) 33,078 Related income tax effect 4,867 2,415 (11,577) Net reclassification adjustment for gains included in net income (255) (133) (3,357) Related income tax expense 92 48 1,175 (8,227 ) (4,342 ) 19,319 Net effect of AFS securities on other comprehensive income (7,782) (4,068) 24,788 Held to maturity (“HTM”) securities: Accretion on the unrealized loss for securities transferred from AFS to the HTM investment portfolio prior to call or maturity 9 8 8 Related income tax expense (3) (3) (3) Net effect of HTM securities on other comprehensive income 6 5 5 Defined benefit pension plan: Net actuarial loss during the period (2,914) (2,402) (29,419) Related income tax expense (benefit) 1,077 944 10,649 Amortization of prior service cost recognized in net income 0 1 1 Related income tax benefit 0 0 0 Amortization of net actuarial loss recognized in net income 4,921 4,980 1,994 Related income tax benefit (1,813) (1,908) (735) Net effect of change in defined benefit pension plan on other comprehensive income 1,271 1,615 (17,510) Total change in other comprehensive income, net of tax (6,505 ) (2,448 ) 7,283 Total Comprehensive Income $ 140,578 $ 135,511 $ 137,171 The components of accumulated other comprehensive income for the year ended December 31, 2016 are as follows: Changes in Accumulated Other Comprehensive Income (AOCI) by Component (a) For the Year Ended December 31, 2016 (Dollars in thousands) Unrealized Accretion Defined Items Total Balance at January 1, 2016 ($ 2,515 ) ($ 57 ) ($ 35,640 ) ($ 38,212 ) Other comprehensive income before reclassification (7,884 ) 6 0 (7,878 ) Amounts reclassified from accumulated other comprehensive income 102 0 1,271 1,373 Net current-period other comprehensive income, net of tax (7,782 ) 6 1,271 (6,505 ) Balance at December 31, 2016 ($ 10,297 ) ($ 51 ) ($ 34,369 ) ($ 44,717 ) (a) All amounts are net-of-tax. Reclassifications out of Accumulated Other Comprehensive Income (AOCI) For the Year Ended December 31, 2016 (Dollars in thousands) Details about AOCI Components Amount Affected Line Item in the Statement Where Net Income is Presented Available for sale (“AFS”) securities: Reclassification of previous noncredit OTTI to credit OTTI $ 415 Total other-than-temporary impairment losses Net reclassification adjustment for losses (gains) included in net income (255 ) Net gains on sales/calls of investment 160 Total before tax Related income tax effect (58 ) Tax expense 102 Net of tax Pension plan: Net actuarial loss (2,914 )(a) Amortization of net actuarial loss 4,921 (b) 2,007 Total before tax Related income tax effect (736 ) Tax expense 1,271 Net of tax Total reclassifications for the period $ 1,373 (a) This AOCI component is included in the computation of changes in plan assets (see Note N, Employee Benefit Plans) (b) This AOCI component is included in the computation of net periodic pension cost (see Note N, Employee Benefit Plans)

United Bankshares, Inc. (Parent

United Bankshares, Inc. (Parent Company Only) Financial Information	12 Months Ended
	Dec. 31, 2016
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
United Bankshares, Inc. (Parent Company Only) Financial Information	NOTE S—UNITED BANKSHARES, INC. (PARENT COMPANY ONLY) FINANCIAL INFORMATION Condensed Balance Sheets December 31 (In thousands) 2016 2015 Assets Cash and due from banks $ 129,486 $ 39,680 Securities available for sale 4,108 3,168 Securities held to maturity 20 20 Other investment securities 100 100 Investment in subsidiaries: Bank subsidiaries 2,267,561 1,835,440 Nonbank subsidiaries 6,572 6,484 Other assets 15,404 13,904 Total Assets $ 2,423,251 $ 1,898,796 Liabilities and Shareholders’ Equity Junior subordinated debentures of subsidiary trusts $ 128,868 $ 128,868 Accrued expenses and other liabilities 58,636 57,293 Shareholders’ equity (including other accumulated comprehensive loss of $44,717 and $38,212 at December 31, 2016 and 2015, respectively) 2,235,747 1,712,635 Total Liabilities and Shareholders’ Equity $ 2,423,251 $ 1,898,796 Condensed Statements of Income Year Ended December 31 (In thousands) 2016 2015 2014 Income Dividends from banking subsidiaries $ 75,000 $ 70,500 $ 97,000 Net interest income 66 59 59 Management fees: Bank subsidiaries 35,792 28,955 19,400 Nonbank subsidiaries 27 27 27 Other income 8 58 96 Total Income 110,893 99,599 116,582 Expenses Operating expenses 40,180 30,016 24,043 Income Before Income Taxes and Equity in Undistributed Net Income of Subsidiaries 70,713 69,583 92,539 Applicable income tax benefit (1,626 ) (316 ) (1,332 ) Income Before Equity in Undistributed Net Income of Subsidiaries 72,339 69,899 93,871 Equity in undistributed net income of subsidiaries: Bank subsidiaries 74,656 68,012 35,978 Nonbank subsidiaries 88 48 39 Net Income $ 147,083 $ 137,959 $ 129,888 Condensed Statements of Cash Flows Year Ended December 31 (In thousands) 2016 2015 2014 Operating Activities Net income $ 147,083 $ 137,959 $ 129,888 Adjustments to reconcile net income to net cash provided by operating activities: Equity in undistributed net income of subsidiaries (74,744) (68,060) (36,018) Amortization of net periodic pension costs 393 384 34 Stock-based compensation 2,817 2,484 2,195 Net gain on securities transactions (8) (54) (96) Net change in other assets and liabilities (6,401) 8,998 5,172 Net Cash Provided by Operating Activities 69,140 81,711 101,175 Investing Activities Net purchases of securities (234) (1,047) (90) Net cash paid in acquisition of subsidiary (10) 0 (33,271) Increase in investment in subsidiaries (100,000) 0 0 Change in other investment securities 0 2 23 Net Cash Used in Investing Activities (100,244 ) (1,045 ) (33,338 ) Financing Activities Proceeds from issuance of common stock 199,916 0 0 Cash dividends paid (96,351) (88,864) (82,496) Acquisition of treasury stock (1) (1) (2) Proceeds from sale of treasury stock from deferred compensation plan 1 1 81 Excess tax benefits from stock-based compensation arrangements 4,008 1,023 73 Proceeds from exercise of stock options 13,337 7,871 9,878 Net Cash Provided by (Used in) Financing Activities 120,910 (79,970) (72,466) Increase (Decrease) in Cash and Cash Equivalents 89,806 696 (4,629) Cash and Cash Equivalents at Beginning of Year 39,680 38,984 43,613 Cash and Cash Equivalents at End of Year $ 129,486 $ 39,680 $ 38,984

Regulatory Matters

Regulatory Matters	12 Months Ended
	Dec. 31, 2016
Banking and Thrift [Abstract]
Regulatory Matters	NOTE T—REGULATORY MATTERS The subsidiary banks are required to maintain average reserve balances with their respective Federal Reserve Bank. The average amount of those consolidated reserve balances maintained and required for the year ended December 31, 2016, were approximately $606,898,000 and $361,521,000, respectively. The average amount of those consolidated reserve balances maintained and required for the year ended December 31, 2015, was approximately $567,698,000 and $330,953,000, respectively. The primary source of funds for the dividends paid by United Bankshares, Inc. to its shareholders is dividends received from its subsidiary banks. Dividends paid by United’s subsidiary banks are subject to certain regulatory limitations. Generally, the most restrictive provision requires regulatory approval if dividends declared in any year exceed that year’s net income, as defined, plus the retained net profits of the two preceding years. During 2017, the retained net profits available for distribution to United Bankshares, Inc. by its banking subsidiaries as dividends without regulatory approval, are approximately $148,219,000, plus net income for the interim period through the date of declaration. Under Federal Reserve regulation, the banking subsidiaries are also limited as to the amount they may loan to affiliates, including the parent company. Loans from the banking subsidiaries to the parent company are limited to 10% of the banking subsidiaries’ capital and surplus, as defined, or $181,926,000 at December 31, 2016, and must be secured by qualifying collateral. United’s subsidiary banks are subject to various regulatory capital requirements administered by federal banking agencies. Pursuant to capital adequacy guidelines, United’s subsidiary banks must meet specific capital guidelines that involve various quantitative measures of the banks’ assets, liabilities, and certain off-balance-sheet items as calculated under regulatory accounting practices. United’s subsidiary banks’ capital amounts and classifications are also subject to qualitative judgments by the regulators about components, risk weightings, and other factors. As previously mentioned, the new Basel III Capital Rules became effective for United and its banking subsidiaries on January 1, 2015 (subject to a phase-in period). These new quantitative measures established by regulation to ensure capital adequacy require United and its banking subsidiaries to maintain minimum amounts and ratios of total, Tier I capital, and common Tier I capital as defined in the regulations, to risk-weighted assets, as defined, and of Tier I capital, as defined, to average assets, as defined. Failure to meet minimum capital requirements can initiate certain mandatory and possibly additional discretionary actions by regulators that, if undertaken, could have a direct material effect on United’s financial statements. As of December 31, 2016, United exceeds all capital adequacy requirements to which it is subject. At December 31, 2016, the most recent notification from its regulators, United and its subsidiary banks were categorized as well-capitalized. To be categorized as well-capitalized, United must maintain minimum total risk-based, Tier I risk-based, Common Tier I risk-based, and Tier I leverage ratios as set forth in the following table. There are no conditions or events since that notification that management believes would impact United’s well-capitalized status. United’s and its subsidiary banks’, United Bank (WV) and United Bank (VA), capital amounts (in thousands of dollars) and ratios are presented in the following table. (Dollars in thousands) Actual For Capital Adequacy Purposes To Be Well- Capitalized Amount Ratio Amount Ratio Amount Ratio As of December 31, 2016: Total Capital (to Risk-Weighted Assets): United Bankshares $ 1,699,984 14.9 % $ 915,479 ³ $ 1,144,348 ³ United Bank (WV) 638,756 12.2 % 418,700 ³ 523,375 ³ United Bank (VA) 953,891 15.1 % 504,445 ³ 630,557 ³ Tier I Capital (to Risk-Weighted Assets): United Bankshares $ 1,625,543 14.2 % $ 686,609 ³ $ 915,479 ³ United Bank (WV) 590,530 11.3 % 314,025 ³ 418,700 ³ United Bank (VA) 928,301 14.7 % 378,334 ³ 504,445 ³ Common Tier I Capital (to Risk Weighted Assets): United Bankshares $ 1,393,743 12.2 % $ 514,957 ³ $ 743,826 ³ United Bank (WV) 590,530 11.3 % 235,519 ³ 340,194 ³ United Bank (VA) 928,301 14.7 % 283,751 ³ 409,862 ³ Tier I Capital (to Average Assets): United Bankshares $ 1,625,543 12.2 % $ 535,227 ³ $ 669,033 ³ United Bank (WV) 590,530 9.8 % 239,986 ³ 299,983 ³ United Bank (VA) 928,301 11.6 % 318,925 ³ 398,656 ³ As of December 31, 2015: Total Capital (to Risk- Weighted Assets): United Bankshares $ 1,331,492 12.6 % $ 845,876 ³ $ 1,057,345 ³ United Bank (WV) 591,825 12.6 % 377,225 ³ 471,532 ³ United Bank (VA) 720,676 12.2 % 471,303 ³ 589,129 ³ Tier I Capital (to Risk- Weighted Assets): United Bankshares $ 1,254,555 11.9 % $ 634,407 ³ $ 845,876 ³ United Bank (WV) 547,903 11.6 % 282,919 ³ 377,225 ³ United Bank (VA) 687,937 11.7 % 353,477 ³ 471,303 ³ Common Tier I Capital (to Risk Weighted Assets): United Bankshares $ 1,022,755 9.7 % $ 475,805 ³ $ 687,274 ³ United Bank (WV) 547,903 11.6 % 212,189 ³ 306,496 ³ United Bank (VA) 687,937 11.7 % 265,108 ³ 382,934 ³ Tier I Capital (to Average Assets): United Bankshares $ 1,254,555 10.7 % $ 468,776 ³ $ 585,970 ³ United Bank (WV) 547,903 10.2 % 214,519 ³ 268,149 ³ United Bank (VA) 687,937 10.5 % 263,306 ³ 329,132 ³

Fair Values of Financial Instru

Fair Values of Financial Instruments	12 Months Ended
	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Fair Values of Financial Instruments	NOTE U—FAIR VALUES OF FINANCIAL INSTRUMENTS In accordance with ASC topic 820, the following describes the valuation techniques used by United to measure certain financial assets and liabilities recorded at fair value on a recurring basis in the financial statements. Securities available for sale Derivatives For a fair value hedge, the fair value of the interest rate swap is recognized on the balance sheet as either a freestanding asset or liability with a corresponding adjustment to the hedged financial instrument. Subsequent adjustments due to changes in the fair value of a derivative that qualifies as a fair value hedge are offset in current period earnings either in interest income or interest expense depending on the nature of the hedged financial instrument. For a cash flow hedge, the fair value of the interest rate swap is recognized on the balance sheet as either a freestanding asset or liability with a corresponding adjustment to other comprehensive income within shareholders’ equity, net of tax. Subsequent adjustments due to changes in the fair value of a derivative that qualifies as a cash flow hedge are offset to other comprehensive income, net of tax. The portion of a hedge that is ineffective is recognized immediately in earnings. For derivatives that are not designated in a hedge relationship, changes in the fair value of the derivatives are recognized in earnings in the same period as the change in the fair value. Unrealized gains and losses due to changes in the fair value of other derivative financial instruments not in hedge relationship are included in noninterest income and noninterest expense, respectively. The following table presents the balances of financial assets and liabilities measured at fair value on a recurring basis as of December 31, 2016 and 2015, segregated by the level of the valuation inputs within the fair value hierarchy: Fair Value at December 31, 2016 Using (In thousands) Description Balance as of December 31, 2016 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets Available for sale debt securities: U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 95,786 $ 0 $ 95,786 $ 0 State and political subdivisions 192,812 0 192,812 0 Residential mortgage-backed securities Agency 584,096 0 584,096 0 Non-agency 7,043 0 7,043 0 Asset-backed securities 217 0 217 0 Commercial mortgage-backed securities Agency 305,341 0 305,341 0 Trust preferred collateralized debt obligations 33,552 0 0 33,552 Single issue trust preferred securities 11,477 0 11,477 0 Other corporate securities 15,062 0 15,062 0 Total available for sale debt securities 1,245,386 0 1,211,834 33,552 Available for sale equity securities: Financial services industry 10,735 1,372 9,363 0 Equity mutual funds (1) 1,820 1,820 0 0 Other equity securities 1,273 1,273 0 0 Total available for sale equity securities 13,828 4,465 9,363 0 Total available for sale securities 1,259,214 4,465 1,221,197 33,552 Derivative financial assets: Interest rate contracts 2,291 0 2,291 0 Liabilities Derivative financial liabilities: Interest rate contracts 2,605 0 2,605 0 (1) The equity mutual funds are within a rabbi trust for the payment of benefits under a deferred compensation plan for certain key officers of United and its subsidiaries. Fair Value at December 31, 2015 Using (In thousands) Description Balance as of December 31, 2015 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets Available for sale debt securities: U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 73,786 $ 0 $ 73,786 $ 0 State and political subdivisions 133,778 0 133,778 0 Residential mortgage-backed securities Agency 477,982 0 477,982 0 Non-agency 9,571 0 9,571 0 Asset-backed securities 3,399 0 3,399 0 Commercial mortgage-backed securities Agency 305,935 0 305,935 0 Trust preferred collateralized debt obligations 34,686 0 0 34,686 Single issue trust preferred securities 11,693 0 11,693 0 Other corporate securities 10,049 0 10,049 0 Total available for sale debt securities 1,060,879 0 1,026,193 34,686 Available for sale equity securities: Financial services industry 2,723 800 1,923 0 Equity mutual funds (1) 1,596 1,596 0 0 Other equity securities 1,136 1,136 0 0 Total available for sale equity securities 5,455 3,532 1,923 0 Total available for sale securities 1,066,334 3,532 1,028,116 34,686 Derivative financial assets: Interest rate contracts 2,942 0 2,942 0 Liabilities Derivative financial liabilities: Interest rate contracts 4,121 0 4,121 0 (1) The equity mutual funds are within a rabbi trust for the payment of benefits under a deferred compensation plan for certain key officers of United and its subsidiaries. There were no transfers between Level 1 and Level 2 for financial assets and liabilities measured at fair value on a recurring basis during the year ended December 31, 2016 and 2015. The following table presents additional information about financial assets and liabilities measured at fair value at December 31, 2016 and 2015 on a recurring basis and for which United has utilized Level 3 inputs to determine fair value: Available-for-sale (In thousands) Trust preferred collateralized debt obligations 2016 2015 Balance, beginning of year $ 34,686 $ 39,558 Total gains or losses (realized/unrealized): Included in earnings (or changes in net assets) 0 (34 ) Included in other comprehensive income (1,134 ) (4,838 ) Purchases, issuances, and settlements 0 0 Transfers in and/or out of Level 3 0 0 Balance, ending of year $ 33,552 $ 34,686 The amount of total gains or losses for the period included in earnings (or changes in net assets) attributable to the change in unrealized gains or losses relating to assets still held at reporting date 0 0 Certain financial assets are measured at fair value on a nonrecurring basis in accordance with GAAP. Adjustments to the fair value of these assets usually result from the application of lower-of-cost-or-market accounting or write-downs of individual assets. The following describes the valuation techniques used by United to measure certain financial assets recorded at fair value on a nonrecurring basis in the financial statements. Loans held for sale Impaired Loans OREO Intangible Assets: The following table summarizes United’s financial assets that were measured at fair value on a nonrecurring basis as of December 31, 2016 and 2015: (In thousands) Description Balance as of December 31, 2016 Fair Value at December 31, 2016 Using YTD Losses Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets Impaired Loans $ 80,505 $ 0 $ 27,609 $ 52,896 $ 5,119 OREO 31,510 0 31,510 0 2,086 (In thousands) Description Balance as of December 31, 2015 Fair Value at December 31, 2015 Using YTD Losses Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets Impaired Loans $ 69,368 $ 0 $ 29,186 $ 40,182 $ 8,485 OREO 32,228 0 32,228 0 1,141 The following methods and assumptions were used by United in estimating its fair value disclosures for other financial instruments: Cash and Cash Equivalents: Securities held to maturity and other securities Loans: Deposits: Short-term Borrowings: Long-term Borrowings: The estimated fair values of United’s financial instruments are summarized below: Fair Value Measurements (In thousands) Carrying Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) December 31, 2016 Cash and cash equivalents $ 1,434,527 $ 1,434,527 $ 0 $ 1,434,527 $ 0 Securities available for sale 1,259,214 1,259,214 4,465 1,221,197 33,552 Securities held to maturity 33,258 31,178 0 28,158 3,020 Other securities 111,166 105,608 0 0 105,608 Loans held for sale 8,445 8,445 0 8,445 0 Loans 10,268,366 10,122,486 0 0 10,122,486 Derivative financial assets 2,291 2,291 0 2,291 0 Deposits 10,796,867 10,785,294 0 10,785,294 0 Short-term borrowings 209,551 209,551 0 209,551 0 Long-term borrowings 1,172,026 1,142,782 0 1,142,782 0 Derivative financial liabilities 2,605 2,605 0 2,605 0 December 31, 2015 Cash and cash equivalents $ 857,335 $ 857,335 $ 0 $ 857,335 $ 0 Securities available for sale 1,066,334 1,066,334 3,532 1,028,116 34,686 Securities held to maturity 39,099 36,319 0 33,299 3,020 Other securities 98,749 93,811 0 0 93,811 Loans held for sale 10,681 10,681 0 10,681 0 Loans 9,308,354 9,289,463 0 0 9,289,463 Derivative financial assets 2,942 2,942 0 2,942 0 Deposits 9,341,527 9,332,451 0 9,332,451 0 Short-term borrowings 423,028 423,028 0 423,028 0 Long-term borrowings 1,015,249 988,270 0 988,270 0 Derivative financial liabilities 4,121 4,121 0 4,121 0

Variable Interest Entities

Variable Interest Entities	12 Months Ended
	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Variable Interest Entities	NOTE V— VARIABLE INTEREST ENTITIES Variable interest entities (VIEs) are entities that either have a total equity investment that is insufficient to permit the entity to finance its activities without additional subordinated financial support or whose equity investors lack the characteristics of a controlling financial interest (i.e., ability to make significant decisions, through voting rights, right to receive the expected residual returns of the entity, and obligation to absorb the expected losses of the entity). VIEs can be structured as corporations, trusts, partnerships, or other legal entities. United’s business practices include relationships with certain VIEs. For United, the business purpose of these relationships primarily consists of funding activities in the form of issuing trust preferred securities. United currently sponsors thirteen statutory business trusts that were created for the purpose of raising funds that qualify for Tier I regulatory capital. These trusts, of which several were acquired through bank acquisitions, issued or participated in pools of trust preferred capital securities to third-party investors with the proceeds invested in junior subordinated debt securities of United. The Company, through a small capital contribution, owns 100% of the voting equity shares of each trust. The assets, liabilities, operations, and cash flows of each trust are solely related to the issuance, administration, and repayment of the preferred equity securities held by third-party investors. United fully and unconditionally guarantees the obligations of each trust and is obligated to redeem the junior subordinated debentures upon maturity. The trusts utilized in these transactions are variable interest entities (VIEs) as the third-party equity holders lack a controlling financial interest in the trusts through their inability to make decisions that have a significant effect on the operations and success of the entities. United does not consolidate these trusts as it is not the primary beneficiary of these entities because United does not hold a controlling financial interest as evidenced by the power to direct the activities of the VIEs that most significantly impact their economic performance and the obligation to absorb losses of, or the right to receive benefits from, the VIEs that could potentially be significant to the VIEs. Information related to United’s statutory trusts is presented in Note K, Notes to Consolidated Financial Statements. United, through its banking subsidiaries, also makes limited partner equity investments in various low income housing and community development partnerships sponsored by independent third-parties. United invests in these partnerships to either realize tax credits on its consolidated federal income tax return or for purposes of earning a return on its investment. These partnerships are considered VIEs as the limited partners lack a controlling financial interest in the entities through their inability to make decisions that have a significant effect on the operations and success of the partnerships. United’s limited partner interests in these entities is immaterial, however; these partnerships are not consolidated as United is not deemed to be the primary beneficiary. The following table summarizes quantitative information about United’s significant involvement in unconsolidated VIEs: As of December 31, 2016 As of December 31, 2015 (In thousands) Aggregate Assets Aggregate Liabilities Risk Of Loss (1) Aggregate Assets Aggregate Liabilities Risk Of Loss (1) Trust preferred securities $ 240,668 $ 232,583 $ 8,085 $ 240,468 $ 232,492 $ 7,976 (1) Represents investment in VIEs.

Quarterly Financial Data

Quarterly Financial Data	12 Months Ended
	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Data	NOTE W—QUARTERLY FINANCIAL DATA (UNAUDITED) Quarterly financial data for 2016 and 2015 is summarized below (dollars in thousands, except for per share data): (Dollars in thousands) 1st Quarter 2nd Quarter 3rd Quarter 4th Quarter 2016 Interest income $ 108,496 $ 113,087 $ 123,137 $ 125,621 Interest expense 10,212 10,362 12,068 12,368 Net interest income 98,284 102,725 111,069 113,253 Provision for credit losses 4,035 7,667 6,988 5,819 Mortgage banking income 728 789 982 951 Securities gains (losses), net 4 213 1 62 Other noninterest income 15,660 16,965 18,038 15,639 Noninterest expense 58,056 64,855 62,777 62,508 Income taxes 17,879 16,378 18,846 22,472 Net income (1) 34,706 31,792 41,479 39,106 Per share data: Average shares outstanding (000s): Basic 69,497 71,484 76,219 76,864 Diluted 69,714 71,809 76,648 77,303 Net income per share: Basic $ 0.50 $ 0.44 $ 0.54 $ 0.51 Diluted $ 0.50 $ 0.44 $ 0.54 $ 0.51 Dividends per share $ 0.33 $ 0.33 $ 0.33 $ 0.33 2015 Interest income $ 104,549 $ 105,532 $ 106,309 $ 107,240 Interest expense 9,800 9,630 9,991 10,085 Net interest income 94,749 95,902 96,318 97,155 Provision for credit losses 5,354 5,716 5,182 6,322 Mortgage banking income 545 663 665 634 Securities losses, net 12 3 111 29 Other noninterest income 17,634 18,832 17,036 17,462 Noninterest expense 57,655 57,730 57,684 58,618 Income taxes 15,304 17,145 16,217 16,864 Net income (1) 34,627 34,809 35,047 33,476 Per share data: Average shares outstanding (000s): Basic 69,208 69,306 69,391 69,432 Diluted 69,477 69,587 69,690 69,737 Net income per share: Basic $ 0.50 $ 0.50 $ 0.50 $ 0.48 Diluted $ 0.50 $ 0.50 $ 0.50 $ 0.48 Dividends per share $ 0.32 $ 0.32 $ 0.32 $ 0.33 (1) For further information, see the related discussion “Quarterly Results” included in Management’s Discussion and Analysis.

Summary of Significant Accoun32

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Nature of Operations	Nature of Operations:
Operating Segments	Operating Segments:
Basis of Presentation	Basis of Presentation: At the close of business on June 3, 2016, United acquired Bank of Georgetown, a privately held community bank headquartered in Washington, D. C. The transaction was accounted for using the acquisition method and their results of operations have been included in the United’s consolidated financial statements as of the acquisition date. United determines whether it has a controlling financial interest in an entity by first evaluating whether the entity is a voting interest entity or a variable interest entity (VIE) under U.S. generally accepted accounting principles. Voting interest entities are entities in which the total equity investment at risk is sufficient to enable the entity to finance itself independently and provides the equity holders with the obligation to absorb losses, the right to receive residual returns and the right to make decisions about the entity’s activities. United consolidates voting interest entities in which it has all, or at least a majority of, the voting interest. As defined in applicable accounting standards, VIEs are entities that lack one or more of the characteristics of a voting interest entity. A controlling financial interest in a VIE is present when an enterprise has both the power to direct the activities of the VIE that most significantly impact the VIE’s economic performance and an obligation to absorb losses or the right to receive benefits that could potentially be significant to the VIE. The enterprise with a controlling financial interest, known as the primary beneficiary, consolidates the VIE. United’s wholly owned and indirect wholly owned statutory trust subsidiaries are VIEs for which United is not the primary beneficiary. Accordingly, its accounts are not included in United’s consolidated financial statements. The accounting and reporting policies of United conform with U.S. generally accepted accounting principles. In preparing the consolidated financial statements, management is required to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from those estimates. To conform to the 2016 presentation, certain reclassifications have been made to prior period amounts, which had no impact on net income, comprehensive income or shareholders’ equity. In the opinion of management, all adjustments necessary for a fair presentation of financial position and results of operations have been made. Such adjustments are of a normal and recurring nature. The Company has evaluated events and transactions subsequent to December 31, 2016 through the date these financial statements were issued. Based on definitions and requirements of generally accepted accounting principles for “Subsequent Events,” the Company has not identified any events that would require adjustments to, or disclosure in the financial statements.
Cash and Cash Equivalents	Cash and Cash Equivalents:
Securities	Securities: Gains or losses on sales of securities are recognized by the specific identification method and are reported in securities gains and losses within noninterest income of the Consolidated Statements of Income. United reviews available-for-sale and held-to-maturity securities on a quarterly basis for possible impairment. United determines whether a decline in fair value below the amortized cost basis of a security is other-than-temporary. This determination requires significant judgment. In making this judgment, United’s review includes an analysis of the facts and circumstances of each individual investment such as the severity of loss, the length of time the fair value has been below cost, the expectation for that security’s performance, the creditworthiness of the issuer, recent changes in external credit ratings, and the assessment of collection of the security’s contractual amounts from the issuer or issuers. If United intends to sell, or it is more likely than not that United will be required to sell an impaired debt security before recovery of its amortized cost basis less any current period credit loss, other-than-temporary impairment is recognized in earnings. The credit loss is defined as the difference between the present value of cash flows expected to be collected (discounted at the contractual rate) and the amortized cost basis. The amount recognized in earnings is equal to the entire difference between the security’s amortized cost basis and its fair value at the balance sheet date. If United does not intend to sell, and it is not more likely than not that United will be required to sell the impaired debt security prior to recovery of its amortized cost basis less any current-period credit loss, the other-than-temporary impairment is separated into the following: 1) the amount representing the credit loss, which is recognized within noninterest income of the Consolidated Statements of Income, and 2) the amount related to all other factors, which is recognized in other comprehensive income within shareholders’ equity of the Consolidated Balance Sheets. For equity securities, United evaluates the near-term prospects of the investment in relation to the severity and duration of any impairment and United’s ability and intent to hold these equity securities until a recovery of their fair value to at least the cost basis of the investment. Equity securities that are deemed to be other-than-temporarily impaired are written down to the fair value with the write-down recognized within noninterest income of the Consolidated Statements of Income. Certain security investments that do not have readily determinable fair values and for which United does not exercise significant influence are carried at cost and are classified as other investment securities on the balance sheet. These cost-method investments are reviewed for impairment at least annually or sooner if events or changes in circumstances indicate the carrying value may not be recoverable.
Securities Purchased Under Resale Agreements and Securities Sold Under Agreements to Repurchase	Securities Purchased Under Resale Agreements and Securities Sold Under Agreements to Repurchase:
Loans	Loans: Loans are designated as impaired when, in the opinion of management, based on current information and events, the collection of principal and interest in accordance with the loan contract is doubtful. Consistent with United’s existing method of income recognition for loans, interest on impaired loans, except those classified as nonaccrual, is recognized as income using the accrual method. United’s method of income recognition for impaired loans that are classified as nonaccrual is to recognize interest income on the cash basis or apply the cash receipt to principal when the ultimate collectibility of principal is in doubt. A loan is categorized as restructured if a concession is granted to provide for a reduction of either interest or principal due to a deterioration in the financial condition of the borrower. A loan classified as restructured will generally retain such classification until the loan is paid in full. However, a restructured one-to-four-family residential mortgage loan that yields a market rate and demonstrates the ability to pay under the terms of the restructured note through a sustained period of repayment performance, which is generally one year, is removed from the restructured classification. Interest income on restructured loans is accrued at the reduced rate and the loan is returned to performing status once the borrower demonstrates the ability to pay under the terms of the restructured note through a sustained period of repayment performance, which is generally six months. The portfolio of restructured loans is monitored monthly.
Loans Acquired Through Transfer	Loans Acquired Through Transfer:
Loans Held for Sale	Loans Held for Sale:
Allowance for Credit Losses	Allowance for Credit Losses: The allowance for loan losses is management’s estimate of the probable credit losses inherent in the loan portfolio. Management’s evaluation of the adequacy of the allowance for loan losses and the appropriate provision for credit losses is based upon a quarterly evaluation of the portfolio. This evaluation is inherently subjective and requires significant estimates, including the amounts and timing of estimated future cash flows, estimated losses on pools of loans based on historical loss experience, and consideration of current economic trends, all of which are susceptible to constant and significant change. The amounts allocated to specific credits and loan pools grouped by similar risk characteristics are reviewed on a quarterly basis and adjusted as necessary based upon subsequent changes in circumstances. In determining the components of the allowance for credit losses, management considers the risk arising in part from, but not limited to, charge-off and delinquency trends, current economic and business conditions, lending policies and procedures, the size and risk characteristics of the loan portfolio, concentrations of credit, and other various factors. Loans deemed to be uncollectible are charged against the allowance for loan losses, while recoveries of previously charged-off amounts are credited to the allowance for loan losses. In determining the adequacy of the allowance for loan losses, management makes allocations to specific commercial loans classified by management as to risk. Management determines the loan’s risk by considering the borrowers’ ability to repay, the collateral securing the credit and other borrower-specific factors that may impact collectibility. For impaired loans, specific allocations are based on the present value of expected future cash flows using the loan’s effective interest rate, or as a practical expedient, at the loan’s observable market price or the fair value of the collateral if the loan is collateral-dependent. Other commercial loans not specifically reviewed on an individual basis are evaluated based on loan pools, which are grouped by similar risk characteristics using management’s internal risk ratings. Allocations for these commercial loan pools are determined based upon historical loss experience adjusted for current environmental conditions and risk factors and the estimate period it takes for losses to result in a charge-off. Allocations for loans, other than commercial loans, are developed by applying historical loss experience adjusted for current environmental conditions and risk factors to loan pools grouped by similar risk characteristics. The environmental factors considered for each of the loan portfolios includes estimated probable inherent but undetected losses within the portfolio due to uncertainties in economic conditions, delays in obtaining information, including unfavorable information about a borrower’s financial condition, the difficulty in identifying triggering events that correlate perfectly to subsequent loss rates, and risk factors that have not yet fully manifested themselves in loss allocation factors. While allocations are made to specific loans and pools of loans, the allowance is available for all loan losses. Beginning in 2015, United’s methodology related to the allowance for loan losses was enhanced by estimating the loss emergence period. Management believes that the allowance for credit losses is adequate to provide for probable losses on existing loans and loan-related commitments based on information currently available.
Bank Premises and Equipment	Bank Premises and Equipment:
Other Real Estate Owned	Other Real Estate Owned
Advertising Costs	Advertising Costs:
Income Taxes	Income Taxes: For uncertain income tax positions, United records a liability based on a recognition threshold of more-likely-than-not, and a measurement attribute for all tax positions taken on a tax return, in order for those tax positions to be recognized in the financial statements. United files a consolidated income tax return with its subsidiaries. Federal income tax expense or benefit has been allocated to subsidiaries on a separate return basis.
Intangible Assets	Intangible Assets: Goodwill is not amortized, but is tested for impairment at least annually or sooner if indicators of impairment exist. Intangible assets with definite useful lives (such as core deposit intangibles) are amortized over their respective estimated useful lives to their estimated residual values, and reviewed for impairment at least annually or as indicators of impairment are identified. Based on the most recent goodwill impairment test, no impairment was noted. As of December 31, 2016, and 2015, total goodwill approximated $863,767,000 and $710,252,000, respectively.
Derivative Financial Instruments	Derivative Financial Instruments: Derivative instruments designated in a hedge relationship to mitigate exposure to changes in the fair value of an asset, liability, or firm commitment attributable to a particular risk, such as interest rate risk, are considered fair value hedges. Derivative instruments designated in a hedge relationship to mitigate exposure to variability in expected future cash flows, or other types of forecasted transactions, are considered cash flow hedges. For a fair value hedge, the fair value of the interest rate swap is recognized on the balance sheet as either a freestanding asset or liability with a corresponding adjustment to the hedged financial instrument. Subsequent adjustments due to changes in the fair value of a derivative that qualifies as a fair value hedge are offset in current period earnings. For a cash flow hedge, the fair value of the interest rate swap is recognized on the balance sheet as either a freestanding asset or liability with a corresponding adjustment to other comprehensive income within shareholders’ equity, net of tax. Subsequent adjustments due to changes in the fair value of a derivative that qualifies as a cash flow hedge are offset to other comprehensive income, net of tax. The portion of a hedge that is ineffective is recognized immediately in earnings. At inception of a hedge relationship, United formally documents the hedged item, the particular risk management objective, the nature of the risk being hedged, the derivative being used, how effectiveness of the hedge will be assessed and how the ineffectiveness of the hedge will be measured. United also assesses hedge effectiveness at inception and on an ongoing basis using regression analysis. Hedge ineffectiveness is measured by using the change in fair value method. The change in fair value method compares the change in the fair value of the hedging derivative to the change in the fair value of the hedged exposure, attributable to changes in the benchmark rate. For derivatives that are not designated in a hedge relationship, changes in the fair value of the derivatives are recognized in earnings in the same period as the change in the fair value.
Stock-Based Compensation	Stock-Based Compensation Stock-based compensation expense was $2,817,000 in 2016, $2,484,000 in 2015 and $2,195,000 in 2014.
Treasury Stock	Treasury Stock
Trust Assets and Income	Trust Assets and Income:
Earnings Per Common Share	Earnings Per Common Share: 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 during the applicable period, excluding outstanding participating securities. 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 stock compensation using the treasury stock method. The reconciliation of the numerator and denominator of basic earnings per share with that of diluted earnings per share is presented as follows: Year Ended December 31 (Dollars in thousands, except per share) 2016 2015 2014 Distributed earnings allocated to common stock $ 98,510 $ 89,497 $ 88,353 Undistributed earnings allocated to common stock 48,317 48,218 41,305 Net earnings allocated to common shareholders $ 146,827 $ 137,715 $ 129,658 Average common shares outstanding 73,531,992 69,334,849 67,404,254 Dilutive effect of stock compensation 361,135 290,682 244,419 Average diluted shares outstanding 73,893,127 69,625,531 67,648,673 Earnings per basic common share $ 2.00 $ 1.99 $ 1.93 Earnings per diluted common share $ 1.99 $ 1.98 $ 1.92
Fair Value Measurements	Fair Value Measurements The Fair Value Measurements and Disclosures topic specifies a hierarchy of valuation techniques based on whether the inputs to those valuation techniques are observable or unobservable. Observable inputs reflect market data obtained from independent sources, while unobservable inputs reflect United’s market assumptions. The three levels of the fair value hierarchy based on these two types of inputs are as follows: Level 1 - Valuation is based on quoted prices in active markets for identical assets and liabilities. Level 2 - Valuation is based on observable inputs including quoted prices in active markets for similar assets and liabilities, quoted prices for identical or similar assets and liabilities in less active markets, and model-based valuation techniques for which significant assumptions can be derived primarily from or corroborated by observable data in the market. Level 3 - Valuation is based on model-based techniques that use one or more significant inputs or assumptions that are unobservable in the market. When determining the fair value measurements for assets and liabilities, United looks to active and observable markets to price identical assets or liabilities whenever possible and classifies such items in Level 1. When identical assets and liabilities are not traded in active markets, United looks to market observable data for similar assets and liabilities and classifies such items as Level 2. Nevertheless, certain assets and liabilities are not actively traded in observable markets and United must use alternative valuation techniques using unobservable inputs to determine a fair value and classifies such items as Level 3. For assets and liabilities that are not actively traded, the fair value measurement is based primarily upon estimates that require significant judgment. Therefore, the results may not be realized in an actual sale or immediate settlement of the asset or liability. Additionally, there are inherent weaknesses in any calculation technique, and changes in the underlying assumptions used, including discount rates and estimates of future cash flows, could significantly affect the results of current or future values. The level within the fair value hierarchy is based on the lowest level of input that is significant in the fair value measurement.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In June 2016, the FASB issued ASU 2016-13, “Financial Instruments – Credit Losses.” ASU 2016-13 changes the impairment model for most financial assets and certain other instruments that aren’t measured at fair value through net income. The standard will replace today’s “incurred loss” approach with an “expected loss” model for instruments measured at amortized cost and require entities to record allowances for available-for-sale debt securities rather than reduce the carrying amount under the current other-than-temporary impairment (OTTI) model. ASU 2016-13 also simplifies the accounting model for purchased credit-impaired debt securities and loans. Entities will apply the standard’s provisions as a cumulative-effect adjustment to retained earnings as of the beginning of the first reporting period in which the guidance is effective. ASU 2016-13 is effective for United on January 1, 2020, with early adoption permitted, and management is currently evaluating the possible impact this standard may have on the Company’s financial condition or results of operations. In March 2016, the FASB issued ASU 2016-09, “Compensation-Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting.” ASU 2016-09 will change certain aspects of accounting for share-based payments to employees. The new guidance will, amongst other things, require all income tax effects of awards to be recognized in the income statement when the awards vest or are settled. It also will allow an employer to repurchase more of an employee’s shares than it can today for tax withholding purposes without triggering liability accounting and to make a policy election to account for forfeitures as they occur. United adopted ASU 2016-09 on January 1, 2017 utilizing the modified retrospective method. The Company will continue to estimate the number of awards expected to be forfeited and adjust the estimate when it is no longer probable that the employee will fulfill the service condition, as was previously required. ASU 2016-09 also requires that all income tax-related cash flows resulting from share-based payments be reported as operating activities in the statement of cash flows. Previously, income tax benefits at settlement of an award were reported as a reduction to operating cash flows and an increase to financing cash flows to the extent that those benefits exceeded the income tax benefits reported in earnings during the award’s vesting period. The Company plans to apply that change in cash flow classification on a retrospective basis. The recognition of excess tax benefits and deficiencies in the income statement was adopted prospectively. Based on the Company’s current stock valuation and estimated exercise activity associated with stock options, it anticipates an insignificant adjustment to income tax expense. The adoption of ASU 2016-09 did not have a material impact on the Company’s financial condition or results of operations. In February 2016, the FASB issued ASU 2016-02, “Leases (Topic 842)”. ASU 2016-02 includes a lessee accounting model that recognizes two types of leases, finance leases and operating leases, while lessor accounting will remain largely unchanged from the current GAAP. ASU 2016-02 requires, amongst other things, that a lessee recognize on the balance sheet a right-of-use asset and a lease liability for leases with terms of more than twelve months. 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 is effective for United on January 1, 2019 and management is currently evaluating the possible impact this standard may have on the Company’s financial condition or results of operations. In January 2016, the FASB issued ASU 2016-01, “Financial Instruments Overall: Recognition and Measurement of Financial Assets and Financial Liabilities.” ASU 2016-01 makes changes to the classification and measurement of investments in equity securities, the presentation of certain fair value changes for financial liabilities measured at fair value under the fair value option and disclosure of fair value of instruments. In addition, ASU 2016-01 clarifies guidance related to the valuation allowance assessment when recognizing deferred tax assets resulting from unrealized losses on available-for-sale debt securities. ASU 2016-01 is effective for United on January 1, 2018 and is not expected to have a significant impact on the Company’s financial condition or results of operations. In May 2014, the FASB issued ASU 2014-09, “Revenue from Contracts with Customers (Topic 606).” ASU 2014-09 supersedes the revenue recognition requirements in ASC topic 605, “Revenue Recognition,” and most industry-specific guidance throughout the ASC. The amendments require an entity to recognize revenue upon the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods and services. The new revenue recognition standard sets forth a five step principle-based approach for determining revenue recognition. ASU 2014-09 now will be effective for United on January 1, 2018 with early adoption permitted on January 1, 2017. The Company intends to adopt the amendments of ASU 2014-09 beginning January 1, 2018 through the modified-retrospective transition method with a cumulative effect adjustment to opening retained earnings. The Company’s revenue is comprised of net interest income and noninterest income. As the standard does not apply to revenue associated with financial instruments, net interest income and gains and losses from securities are not impacted by the standard. Our implementation efforts to date include identification of revenue streams within the scope of the guidance and analyzing those revenue streams to determine the impact of the standard. We are in the process of evaluating revenue contracts for the impact the new recognition methods will have on revenue recognition. Based on this review, ASU 2014-09 may require the Company to change how it recognizes certain recurring revenue streams related to noninterest income including fees from trust and brokerage services. Although we do not expect this standard to have a material impact on the timing or amount of revenue, we are still assessing the potential impact on the Company’s consolidated financial statements.

Summary of Significant Accoun33

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Reconciliation of Numerator and Denominator of Basic Earnings Per Share with that of Diluted Earnings Per Share	The reconciliation of the numerator and denominator of basic earnings per share with that of diluted earnings per share is presented as follows: Year Ended December 31 (Dollars in thousands, except per share) 2016 2015 2014 Distributed earnings allocated to common stock $ 98,510 $ 89,497 $ 88,353 Undistributed earnings allocated to common stock 48,317 48,218 41,305 Net earnings allocated to common shareholders $ 146,827 $ 137,715 $ 129,658 Average common shares outstanding 73,531,992 69,334,849 67,404,254 Dilutive effect of stock compensation 361,135 290,682 244,419 Average diluted shares outstanding 73,893,127 69,625,531 67,648,673 Earnings per basic common share $ 2.00 $ 1.99 $ 1.93 Earnings per diluted common share $ 1.99 $ 1.98 $ 1.92

Mergers and Acquisitions (Table

Mergers and Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2016
Business Combinations [Abstract]
Schedule of Acquired Loans Accounted for at Fair Value	In conjunction with the Bank of Georgetown merger, the acquired loan portfolio was accounted for at fair value as follows: (Dollars in thousands) June 3, 2016 Contractually required principal and interest at acquisition $ 1,275,398 Contractual cash flows not expected to be collected (33,713 ) Expected cash flows at acquisition 1,241,685 Interest component of expected cash flows (273,488 ) Basis in acquired loans at acquisition – estimated fair value $ 968,197
Schedule of Expected Fair Value of Acquired Identifiable Assets and Liabilities Assumed	The consideration paid for Bank of Georgetown’s common equity and the expected fair value of acquired identifiable assets and liabilities assumed as of the Acquisition Date were as follows: (Dollars in thousands) Purchase price: Value of common shares issued (6,527,746 shares) $ 253,799 Fair value of stock options assumed 10,696 Cash for fractional shares 10 Total purchase price 264,505 Identifiable assets: Cash and cash equivalents 29,340 Investment securities 219,783 Loans 968,197 Premises and equipment 5,574 Core deposit intangibles 9,058 Other assets 31,605 Total identifiable assets $ 1,263,557 Identifiable liabilities: Deposits $ 971,685 Short-term borrowings 101,021 Long-term borrowings 67,659 Other liabilities 11,532 Total identifiable liabilities 1,151,897 Preliminary fair value of net assets acquired including identifiable intangible assets 111,660 Preliminary resulting goodwill $ 152,845
Schedule of Business Acquisition Pro Forma Information	The following table presents certain unaudited pro forma information for the results of operations for the year ended December 31, 2016 and 2015, as if the Bank of Georgetown merger had occurred on January 1, 2016 and 2015, respectively. Proforma Year Ended December 31 (Dollars in thousands) 2016 2015 Total Revenues (1) $ 519,011 $ 509,312 Net Income 148,226 150,910 (1) Represents net interest income plus other income

Investment Securities (Tables)

Investment Securities (Tables)	12 Months Ended
	Dec. 31, 2016
Summary of Amortized Cost and Estimated Fair Values of Available for Sale Securities	The following is a summary of the amortized cost and estimated fair values of securities available for sale. December 31, 2016 (In thousands) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Cumulative OTTI in AOCI (1) U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 95,247 $ 698 $ 159 $ 95,786 $ 0 State and political subdivisions 196,350 1,364 4,902 192,812 0 Residential mortgage-backed securities Agency 585,208 3,999 5,111 584,096 0 Non-agency 6,629 426 12 7,043 86 Commercial mortgage-backed securities Agency 304,635 1,948 1,242 305,341 0 Asset-backed securities 217 0 0 217 0 Trust preferred collateralized debt obligations 48,558 729 15,735 33,552 25,952 Single issue trust preferred securities 13,363 284 2,170 11,477 0 Other corporate securities 14,996 66 0 15,062 0 Marketable equity securities 12,436 1,398 6 13,828 0 Total $ 1,277,639 $ 10,912 $ 29,337 $ 1,259,214 $ 26,038 December 31, 2015 (In thousands) Amortized Gross Gross Estimated Cumulative (1) U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 71,993 $ 1,793 $ 0 $ 73,786 $ 0 State and political subdivisions 130,685 3,144 51 133,778 0 Residential mortgage-backed securities Agency 473,109 5,580 707 477,982 0 Non-agency 9,119 457 5 9,571 458 Commercial mortgage-backed securities Agency 305,990 1,843 1,898 305,935 0 Asset-backed securities 3,404 0 5 3,399 0 Trust preferred collateralized debt obligations 49,386 635 15,335 34,686 25,952 Single issue trust preferred securities 13,811 249 2,367 11,693 0 Other corporate securities 9,999 50 0 10,049 0 Marketable equity securities 4,844 637 26 5,455 0 Total $ 1,072,340 $ 14,388 $ 20,394 $ 1,066,334 $ 26,410 (1) Other-than-temporary impairment in accumulated other comprehensive income. Amounts are before-tax.
Summary of Securities Available for Sale in an Unrealized Loss Position	The following is a summary of securities available for sale which were in an unrealized loss position at December 31, 2016 and 2015. Less than 12 months 12 months or longer (In thousands) Fair Unrealized Fair Unrealized December 31, 2016 U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 24,101 $ 159 $ 0 $ 0 State and political subdivisions 116,300 4,902 0 0 Residential mortgage-backed securities Agency 309,376 5,111 0 0 Non-agency 0 0 218 12 Commercial mortgage-backed securities Agency 162,479 1,242 0 0 Asset-backed securities 0 0 0 0 Trust preferred collateralized debt obligations 0 0 28,579 15,735 Single issue trust preferred securities 0 0 8,185 2,170 Marketable equity securities 357 6 0 0 Total $ 612,613 $ 11,420 $ 36,982 $ 17,917 Less than 12 months 12 months or longer (In thousands) Fair Unrealized Fair Unrealized December 31, 2015 U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 0 $ 0 $ 0 $ 0 State and political subdivisions 15,550 51 0 0 Residential mortgage-backed securities Agency 90,004 707 0 0 Non-agency 348 5 0 0 Commercial mortgage-backed securities Agency 170,340 1,650 9,255 248 Asset-backed securities 3,399 5 0 0 Trust preferred collateralized debt obligations 3,304 135 28,633 15,200 Single issue trust preferred securities 4,225 404 3,720 1,963 Marketable equity securities 986 26 0 0 Total $ 288,156 $ 2,983 $ 41,608 $ 17,411
Summary of Gains or Losses on Proceeds from Maturities, Sales and Calls of Available for Sale Securities by Specific Identification Method	The realized losses relate to sales of securities within a rabbi trust for the payment of benefits under a deferred compensation plan for certain key officers and its subsidiaries. Year Ended (In thousands) 2016 2015 2014 Proceeds from maturities, sales and calls $ 513,990 $ 191,266 $ 534,489 Gross realized gains 268 143 3,592 Gross realized losses 13 10 235
Summary of Unrealized Loss Positions of Available for Sale TRUP CDOs and Single Issue Trust Preferred Securities	The following is a summary of the available for sale Trup Cdos as of December 31, 2016. Amortized Cost Class Amortized Cost Fair Value Net Loss Investment Split Below (In thousands) Senior – Bank $ 5,988 $ 5,545 $ 443 $ 3,847 $ 0 $ 2,141 Mezzanine —Bank (now in senior position) 11,309 8,175 3,134 0 0 11,309 Mezzanine – Bank 26,095 16,170 9,925 0 0 26,095 Mezzanine – Bank & Insurance (combination) 5,166 3,662 1,504 0 0 5,166 Totals $ 48,558 $ 33,552 $ 15,006 $ 3,847 $ 0 $ 44,711
Roll Forward of Credit Losses on Securities	Below is a progression of the credit losses on securities which United has recorded other-than-temporary charges. These charges were recorded through earnings and other comprehensive income. (In thousands) Year Ended December 31 2016 2015 2014 Balance of cumulative credit losses at beginning of period $ 23,773 $ 23,739 $ 40,663 Additional credit losses on securities for which OTTI was previously recognized 33 34 6,442 Reductions for securities sold or paid off during the period (1,644) 0 (23,366) Balance of cumulative credit losses at end of period $ 22,162 $ 23,773 $ 23,739
Summary of Amortized Cost and Estimated Fair Values of Securities Held to Maturity	The following is a summary of the amortized cost and estimated fair values of securities held to maturity. December 31, 2016 (In thousands) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 5,295 $ 570 $ 0 $ 5,865 State and political subdivisions 8,598 17 0 8,615 Residential mortgage-backed securities Agency 30 5 0 35 Single issue trust preferred securities 19,315 0 2,672 16,643 Other corporate securities 20 0 0 20 Total $ 33,258 $ 592 $ 2,672 $ 31,178 December 31, 2015 (In thousands) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 10,425 $ 860 $ 0 $ 11,285 State and political subdivisions 9,321 21 253 9,089 Residential mortgage-backed securities Agency 35 6 0 41 Single issue trust preferred securities 19,298 0 3,414 15,884 Other corporate securities 20 0 0 20 Total $ 39,099 $ 887 $ 3,667 $ 36,319
Summary of Gross Realized Gains and Losses on Calls and Sales of Held to Maturity Securities Included in Earnings	The following table shows the gross realized gains and losses on calls and sales of held to maturity securities that have been included in earnings as a result of those calls and sales. Gains or losses on calls of held to maturity securities are recognized by the specific identification method. Year Ended (In thousands) 2016 2015 2014 Gross realized gains $ 0 $ 0 $ 9 Gross realized losses 0 0 0
Maturities and Weighted-Average Yields of Securities	The following table sets forth the maturities of all securities (based on amortized cost) at December 31, 2016, and the weighted-average yields of such securities (calculated on the basis of the cost and the effective yields weighted for the scheduled maturity of each security). After 1 But After 5 But (Dollars in thousands) Within 1 Year Within 5 Years Within 10 Years After 10 Years Amount Yield Amount Yield Amount Yield Amount Yield U.S. Treasury and other U.S. Government agencies and corporations $ 32,097 0.39 % $ 61,924 2.04 % $ 6,521 2.25 % $ 0 0.00 % States and political subdivisions (1) 14,451 2.89 % 41,926 3.24 % 34,096 3.81 % 114,475 3.94 % Residential mortgage-backed securities Agency 68 5.44 % 5,043 4.01 % 58,141 2.72 % 521,986 2.34 % Non-agency 0 0.00 % 1,339 5.00 % 0 0.00 % 5,290 5.83 % Commercial mortgage-backed Agency 9,051 0.95 % 188,624 1.79 % 106,960 2.63 % 0 0.00 % Asset-backed securities 217 1.38 % 0 0.00 % 0 0.00 % 0 0.00 % Trust preferred collateralized debt obligations 0 0.00 % 0 0.00 % 0 0.00 % 48,558 3.80 % Single issue trust preferred securities 0 0.00 % 0 0.00 % 0 0.00 % 32,678 2.84 % Marketable equity securities 0 0.00 % 0 0.00 % 0 0.00 % 12,436 0.64 % Other Corporate securities 0 0.00 % 4,996 1.98 % 10,000 5.50 % 20 0.00 % (1) Tax-equivalent
Held-to-maturity Securities [Member]
Summary of Maturities of Debt Securities Held to Maturity by Amortized Cost and Estimated Fair Value	The amortized cost and estimated fair value of securities available for sale at December 31, 2016 by contractual maturity are shown below. Expected maturities may differ from contractual maturities because the issuers may have the right to call or prepay obligations without penalties. Estimated (In thousands) Amortized Fair Cost Value Due in one year or less $ 53,286 $ 53,330 Due after one year through five years 296,181 297,385 Due after five years through ten years 213,094 213,791 Due after ten years 702,642 680,880 Marketable equity securities 12,436 13,828 Total $ 1,277,639 $ 1,259,214
Available-for-sale Securities [Member]
Summary of Maturities of Debt Securities Held to Maturity by Amortized Cost and Estimated Fair Value	The amortized cost and estimated fair value of debt securities held to maturity at December 31, 2016 by contractual maturity are shown below. Expected maturities may differ from contractual maturities because the issuers may have the right to call or prepay obligations with or without call or prepayment penalties. Estimated (In thousands) Amortized Fair Cost Value Due in one year or less $ 1,040 $ 1,041 Due after one year through five years 8,268 8,850 Due after five years through ten years 3,585 3,589 Due after ten years 20,365 17,698 Total $ 33,258 $ 31,178

Loans (Tables)

Loans (Tables)	12 Months Ended
	Dec. 31, 2016
Receivables [Abstract]
Major Classes of Loans	Major classes of loans are as follows: December 31 (In thousands) 2016 2015 Commercial, financial, and agricultural Owner-occupied $ 1,049,885 $ 927,746 Nonowner-occupied 3,425,453 2,896,367 Other commercial 1,613,437 1,602,222 Total commercial, financial & agricultural 6,088,775 5,426,335 Residential real estate 2,403,437 2,268,685 Construction & land development 1,255,738 1,273,054 Consumer: Bankcard 14,187 11,653 Other Consumer 594,582 419,225 Less: Unearned interest (15,582) (14,872) Total Loans, net of unearned interest $ 10,341,137 $ 9,384,080
Activity for Accretable Yield	Activity for the accretable yield for the year of 2016 follows. (In thousands) Accretable yield at the beginning of the period $ 12,156 Accretion (including cash recoveries) (11,457 ) Additions for Bank of Georgetown acquisition 19,552 Net reclassifications to accretable from non-accretable 12,439 Disposals (including maturities, foreclosures, and charge-offs) (3,525 ) Accretable yield at the ending of the period $ 29,165

Credit Quality (Tables)

Credit Quality (Tables)	12 Months Ended
	Dec. 31, 2016
Text Block [Abstract]
Schedule of Troubled Debt Restructurings, Segregated by Class of Loans	The following table sets forth United’s troubled debt restructurings that have been restructured during the year ended December 31, 2016 and 2015, segregated by class of loans: Troubled Debt Restructurings For the Year Ended December 31, 2016 (In thousands) Number of Pre-Modification Post-Modification Commercial real estate: Owner-occupied 1 $ 1,190 $ 1,178 Nonowner-occupied 0 0 0 Other commercial 7 2,803 2,213 Residential real estate 1 1,400 1,400 Construction & land development 0 0 0 Consumer: Bankcard 0 0 0 Other consumer 0 0 0 Total 9 $ 5,393 $ 4,791 Troubled Debt Restructurings For the Year Ended December 31, 2015 (In thousands) Number of Pre-Modification Post-Modification Commercial real estate: Owner-occupied 0 $ 0 $ 0 Nonowner-occupied 1 669 647 Other commercial 3 2,942 2,918 Residential real estate 0 0 0 Construction & land development 0 0 0 Consumer: Bankcard 0 0 0 Other consumer 0 0 0 Total 4 $ 3,611 $ 3,565
Schedule of Charged-off Troubled Debt Restructurings on Financing Receivables	Year Ended December 31, 2016 (In thousands) Number of Recorded Troubled Debt Restructurings Commercial real estate: 0 $ 0 Owner-occupied 0 0 Nonowner-occupied 0 0 Other commercial 1 37 Residential real estate 0 0 Construction & land development 0 0 Consumer: 0 0 Bankcard 0 0 Other consumer 0 0 Total 1 $ 37
Schedule of Age Analysis of Past Due Loans, Segregated by Class of Loans	The following table sets forth United’s age analysis of its past due loans, segregated by class of loans: Age Analysis of Past Due Loans As of December 31, 2016 (In thousands) 30-89 90 Days or more Total Past Current & Total Financing Recorded Commercial real estate: Owner-occupied $ 5,850 $ 3,981 $ 9,831 $ 1,040,054 $ 1,049,885 $ 94 Nonowner-occupied 9,288 20,847 30,135 3,395,318 3,425,453 172 Other commercial 15,273 42,766 58,039 1,555,398 1,613,437 2,518 Residential real estate 29,976 25,991 55,967 2,347,470 2,403,437 4,216 Construction & land development 3,809 7,779 11,588 1,244,150 1,255,738 33 Consumer: Bankcard 422 141 563 13,624 14,187 141 Other consumer 10,015 1,712 11,727 582,855 594,582 1,412 Total $ 74,633 $ 103,217 $ 177,850 $ 10,178,869 $ 10,356,719 $ 8,586 (1) Other includes loans with a recorded investment of $171,596 acquired and accounted for under ASC topic 310-30 “Loans and Debt Securities Acquired with Deteriorated Credit Quality”. Age Analysis of Past Due Loans As of December 31, 2015 (In thousands) 30-89 90 Days or more Total Past Current & Total Financing Recorded Commercial real estate: Owner-occupied $ 8,639 $ 9,831 $ 18,470 $ 909,276 $ 927,746 $ 400 Nonowner-occupied 24,209 26,126 50,335 2,846,032 2,896,367 552 Other commercial 14,888 33,297 48,185 1,554,037 1,602,222 3,643 Residential real estate 44,312 28,332 72,644 2,196,041 2,268,685 4,294 Construction & land development 2,412 15,416 17,828 1,255,226 1,273,054 1,347 Consumer: Bankcard 223 168 391 11,262 11,653 168 Other consumer 9,082 1,596 10,678 408,547 419,225 1,224 Total $ 103,765 $ 114,766 $ 218,531 $ 9,180,421 $ 9,398,952 $ 11,628 (1) Other includes loans with a recorded investment of $148,197 acquired and accounted for under ASC topic 310-30 “Loans and Debt Securities Acquired with Deteriorated Credit Quality”.
Schedule of Nonaccrual Loans, Segregated by Class of Loans	The following table sets forth United’s nonaccrual loans, segregated by class of loans: Loans on Nonaccrual Status (In thousands) December 31, 2016 December 31, 2015 Commercial real estate: Owner-occupied $ 3,887 $ 9,431 Nonowner-occupied 20,675 25,574 Other commercial 40,248 29,654 Residential real estate 21,775 24,038 Construction & land development 7,746 14,069 Consumer: Bankcard 0 0 Other consumer 300 372 Total $ 94,631 $ 103,138
Schedule of Credit Quality Indicators Information, by Class of Loans	The following tables set forth United’s credit quality indicators information, by class of loans: Credit Quality Indicators Corporate Credit Exposure As of December 31, 2016 Commercial Real Estate (In thousands) Owner- Nonowner- Other Construction & Grade: Pass $ 963,503 $ 3,284,497 $ 1,463,797 $ 1,126,742 Special mention 20,490 36,462 26,537 52,327 Substandard 65,892 104,494 122,893 76,669 Doubtful 0 0 210 0 Total $ 1,049,885 $ 3,425,453 $ 1,613,437 $ 1,255,738 Credit Quality Indicators Corporate Credit Exposure As of December 31, 2015 Commercial Real Estate (In thousands) Owner- Nonowner- Other Construction & Grade: Pass $ 835,082 $ 2,710,504 $ 1,436,670 $ 1,095,238 Special mention 20,391 32,249 26,148 59,100 Substandard 72,273 153,614 136,585 118,716 Doubtful 0 0 2,819 0 Total $ 927,746 $ 2,896,367 $ 1,602,222 $ 1,273,054 Credit Quality Indicators Consumer Credit Exposure As of December 31, 2016 (In thousands) Residential Bankcard Other Grade: Pass $ 2,348,017 $ 13,624 $ 582,704 Special mention 18,240 422 10,132 Substandard 36,995 141 1,746 Doubtful 185 0 0 Total $ 2,403,437 $ 14,187 $ 594,582 As of December 31, 2015 (In thousands) Residential Bankcard Other Grade: Pass $ 2,195,420 $ 11,262 $ 408,271 Special mention 13,494 223 9,188 Substandard 57,981 168 1,766 Doubtful 1,790 0 0 Total $ 2,268,685 $ 11,653 $ 419,225
Schedule of Impaired Loans Information by Class of Loans	The following table set forth United’s impaired loans information, by class of loans: Impaired Loans December 31, 2016 December 31, 2015 (In thousands) Recorded Unpaid Related Recorded Unpaid Related With no related allowance recorded: Commercial real estate: Owner-occupied $ 46,575 $ 47,108 $ 0 $ 36,615 $ 36,828 $ 0 Nonowner-occupied 92,654 93,104 0 69,053 69,517 0 Other commercial 46,064 48,308 0 30,433 32,158 0 Residential real estate 22,747 24,404 0 21,431 22,329 0 Construction & land development 19,863 21,746 0 28,245 29,953 0 Consumer: Bankcard 0 0 0 0 0 0 Other consumer 36 36 0 32 32 0 With an allowance recorded: Commercial real estate: Owner-occupied $ 1,787 $ 2,082 $ 815 $ 4,555 $ 4,555 $ 1,253 Nonowner-occupied 17,938 17,938 2,524 7,890 7,890 1,362 Other commercial 43,774 46,188 13,441 29,486 33,127 18,269 Residential real estate 12,066 12,801 3,431 13,305 14,625 2,118 Construction & land development 4,940 7,899 3,206 14,132 20,135 4,789 Consumer: Bankcard 0 0 0 0 0 0 Other consumer 0 0 0 0 0 0 Total: Commercial real estate: Owner-occupied $ 48,362 $ 49,190 $ 815 $ 41,170 $ 41,383 $ 1,253 Nonowner-occupied 110,592 111,042 2,524 76,943 77,407 1,362 Other commercial 89,838 94,496 13,441 59,919 65,285 18,269 Residential real estate 34,813 37,205 3,431 34,736 36,954 2,118 Construction & land development 24,803 29,645 3,206 42,377 50,088 4,789 Consumer: Bankcard 0 0 0 0 0 0 Other consumer 36 36 0 32 32 0 Impaired Loans For the Year Ended December 31, 2016 December 31, 2015 (In thousands) Average Interest Average Interest With no related allowance recorded: Commercial real estate: Owner-occupied $ 36,800 $ 1,038 $ 41,336 $ 264 Nonowner-occupied 75,848 1,108 68,727 1,139 Other commercial 39,776 1,540 33,510 463 Residential real estate 25,964 538 27,224 234 Construction & land development 24,902 133 33,167 199 Consumer: Bankcard 0 0 0 0 Other consumer 33 0 35 0 With an allowance recorded: Commercial real estate: Owner-occupied $ 3,138 $ 97 $ 4,629 $ 122 Nonowner-occupied 11,920 564 6,954 357 Other commercial 36,511 1,615 20,885 580 Residential real estate 9,585 342 9,314 41 Construction & land development 8,994 83 12,196 252 Consumer: Bankcard 0 0 0 0 Other consumer 0 0 0 0 Total: Commercial real estate: Owner-occupied $ 39,938 $ 1,135 $ 45,965 $ 386 Nonowner-occupied 87,768 1,672 75,681 1,496 Other commercial 76,287 3,155 54,395 1,043 Residential real estate 35,549 880 36,538 275 Construction & land development 33,896 216 45,363 451 Consumer: Bankcard 0 0 0 0 Other consumer 33 0 35 0

Allowance for Credit Losses (Ta

Allowance for Credit Losses (Tables)	12 Months Ended
	Dec. 31, 2016
Receivables [Abstract]
Schedule of Allowance for Loan Losses and Carrying Amount of Loans	A progression of the allowance for loan losses, by portfolio segment, for the year ended December 31, 2016 and 2015 is summarized as follows: Allowance for Loan Losses and Carrying Amount of Loans For the Year Ended December 31, 2016 (In thousands) Commercial Real Other Residential Construction Consumer Allowance Total Owner- Nonowner- Allowance for Loan Losses: Beginning balance $ 3,637 $ 5,309 $ 31,328 $ 15,148 $ 18,205 $ 1,995 $ 104 $ 75,726 Charge-offs 5,281 419 20,430 4,597 2,659 2,794 0 36,180 Recoveries 3,071 675 3,452 639 433 446 0 8,716 Provision 3,846 1,318 18,737 2,580 (5,373) 3,158 243 24,509 Ending balance $ 5,273 $ 6,883 $ 33,087 $ 13,770 $ 10,606 $ 2,805 $ 347 $ 72,771 Ending Balance: individually evaluated for impairment $ 815 $ 2,524 $ 13,441 $ 3,431 $ 3,206 $ 0 $ 0 $ 23,417 Ending Balance: collectively evaluated for impairment $ 4,458 $ 4,359 $ 19,646 $ 10,339 $ 7,400 $ 2,805 $ 347 $ 49,354 Ending Balance: $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 Financing receivables: Ending balance $ 1,049,885 $ 3,425,453 $ 1,613,437 $ 2,403,437 $ 1,255,738 $ 608,769 $ 0 $ 10,356,719 Ending Balance: individually evaluated for impairment $ 18,976 $ 26,835 $ 56,091 $ 14,766 $ 8,152 $ 0 $ 0 $ 124,820 Ending Balance: collectively evaluated for impairment $ 1,005,999 $ 3,323,117 $ 1,527,479 $ 2,373,969 $ 1,221,006 $ 608,733 $ 0 $ 10,060,303 Ending Balance: $ 24,910 $ 75,501 $ 29,867 $ 14,702 $ 26,580 $ 36 $ 0 $ 171,596 Allowance for Loan Losses and Carrying Amount of Loans For the Year Ended December 31, 2015 (In thousands) Commercial Real Other Residential Construction Consumer Allowance Total Owner- Nonowner- Allowance for Loan Losses: Beginning balance $ 4,041 $ 8,167 $ 26,931 $ 13,835 $ 19,402 $ 3,083 $ 70 $ 75,529 Charge-offs 4,755 1,120 10,042 6,411 862 2,309 0 25,499 Recoveries 829 74 714 495 511 499 0 3,122 Provision 3,522 (1,812) 13,725 7,229 (846) 722 34 22,574 Ending balance $ 3,637 $ 5,309 $ 31,328 $ 15,148 $ 18,205 $ 1,995 $ 104 $ 75,726 Ending Balance: individually evaluated for impairment $ 1,253 $ 1,362 $ 18,269 $ 2,119 $ 4,789 $ 0 $ 0 $ 27,792 Ending Balance: collectively evaluated for impairment $ 2,384 $ 3,947 $ 13,059 $ 13,029 $ 13,416 $ 1,995 $ 104 $ 47,934 Ending Balance: loans acquired with deteriorated credit quality $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 Financing receivables: Ending balance $ 927,746 $ 2,896,367 $ 1,602,222 $ 2,268,685 $ 1,273,054 $ 430,878 $ 0 $ 9,398,952 Ending Balance: individually evaluated for impairment $ 12,670 $ 26,152 $ 35,342 $ 17,782 $ 15,779 $ 0 $ 0 $ 107,725 Ending Balance: collectively evaluated for impairment $ 888,802 $ 2,817,748 $ 1,546,018 $ 2,237,865 $ 1,221,760 $ 430,837 $ 0 $ 9,143,030 Ending Balance: loans acquired with deteriorated credit quality $ 26,274 $ 52,467 $ 20,862 $ 13,038 $ 35,515 $ 41 $ 0 $ 148,197
Progression of Allowance for Credit Losses Including Allowance for Loan Losses and Reserve for Lending-Related Commitments	A progression of the allowance for credit losses, which includes the allowance for loan losses and the reserve for lending-related commitments, for the periods presented is summarized as follows: Year Ended December 31 (In thousands) 2016 2015 2014 Balance of allowance for loan losses at beginning of period $ 75,726 $ 75,529 $ 74,198 Provision for loan losses 24,509 22,574 21,937 100,235 98,103 96,135 Loans charged off 36,180 25,499 25,241 Less recoveries (8,716) (3,122) (4,635) Net charge-offs 27,464 22,377 20,606 Balance of allowance for loan losses at end of period $ 72,771 $ 75,726 $ 75,529 Reserve for lending-related commitments 1,044 936 1,518 Balance of allowance for credit losses at end of period $ 73,815 $ 76,662 $ 77,047

Bank Premises and Equipment a39

Bank Premises and Equipment and Leases (Tables)	12 Months Ended
	Dec. 31, 2016
Property, Plant and Equipment [Abstract]
Bank Premises and Equipment	Bank premises and equipment are summarized as follows: December 31 (In thousands) 2016 2015 Land $ 24,238 $ 24,497 Buildings and improvements 89,302 87,717 Leasehold improvements 33,194 26,875 Furniture, fixtures and equipment 65,598 60,233 212,332 199,322 Less allowance for depreciation and amortization 136,423 126,233 Net bank premises and equipment $ 75,909 $ 73,089
Future Minimum Lease Payments	Future minimum lease payments, by year and in the aggregate, under noncancelable operating leases with initial or remaining terms of one year or more, for years subsequent to December 31, 2016, consisted of the following: Year Amount (In thousands) 2017 $ 12,661 2018 11,653 2019 9,756 2020 7,427 2021 6,059 Thereafter 15,380 Total minimum lease payments $ 62,936

Goodwill and Other Intangibles

Goodwill and Other Intangibles (Tables)	12 Months Ended
	Dec. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Summary of Intangible Assets	The following is a summary of intangible assets subject to amortization and those not subject to amortization: As of December 31, 2016 (In thousands) Gross Carrying Accumulated Net Carrying Amortized intangible assets: Core deposit intangible assets $ 69,635 $ (46,681) $ 22,954 Goodwill not subject to amortization $ 863,767 As of December 31, 2015 Gross Carrying Accumulated Net Carrying Amortized intangible assets: Core deposit intangible assets $ 60,577 $ (42,737) $ 17,840 Goodwill not subject to amortization $ 710,252
Reconciliation of Goodwill	The following table provides a reconciliation of goodwill: Goodwill at December 31, 2015 $ 710,252 Reclassification to goodwill 670 Preliminary addition to goodwill from Bank of Georgetown acquisition 152,845 Goodwill at December 31, 2016 $ 863,767
Schedule of Anticipated Amortization Expense	The following table sets forth the anticipated amortization expense for intangible assets for the years subsequent to 2016: Year Amount (In thousands) 2017 $ 4,190 2018 3,707 2019 3,450 2020 3,252 2021 and thereafter 8,355

Deposits (Tables)

Deposits (Tables)	12 Months Ended
	Dec. 31, 2016
Banking and Thrift [Abstract]
Book Value of Deposits	The book value of deposits consisted of the following: (Dollars in thousands) December 31 2016 2015 Demand deposits $ 3,171,841 $ 2,699,958 Interest-bearing checking 1,778,156 1,683,316 Regular savings 721,224 692,079 Money market accounts 3,151,896 2,368,063 Time deposits under $100,000 693,005 794,428 Time deposits over $100,000 1,280,745 1,103,683 Total deposits $ 10,796,867 $ 9,341,527

Short-Term Borrowings (Tables)

Short-Term Borrowings (Tables)	12 Months Ended
	Dec. 31, 2016
Funds Purchased and Securities Sold Under Agreements to Repurchase and Weighted-Average Interest Rates	At December 31, 2016 and 2015, short-term borrowings and the related weighted-average interest rates were as follows: 2016 2015 Weighted- Weighted- (Dollars in thousands) Average Average Amount Rate Amount Rate Federal funds purchased $ 22,235 0.65 % $ 22,230 0.25 % Securities sold under agreements to repurchase 187,316 (1) 0.25 % (1) 290,798 (1) 0.15 % (1) Total $ 209,551 $ 313,028 (1) Excludes a wholesale security sold under an agreement to repurchase assumed in the Virginia Commerce merger of $50,000 and $50,863, including an acquisition accounting adjustment to fair value, with an interest rate of 4.37% at December 31, 2016 and 2015, respectively, and scheduled to mature in May of 2018.
Federal Funds Purchased and Securities Sold under Agreements to Repurchase [Member]
Funds Purchased and Securities Sold Under Agreements to Repurchase and Weighted-Average Interest Rates	The following table shows the distribution of United’s federal funds purchased and securities sold under agreements to repurchase and the weighted-average interest rates thereon at the end of each of the last three years. Also provided are the maximum amount of borrowings and the average amounts of borrowings as well as weighted-average interest rates for the last three years. The table does not include the long-term wholesale security sold under an agreement to repurchase mentioned above assumed in the Virginia Commerce merger. (Dollars in thousands) Federal Funds Purchased Securities Sold Under To Repurchase At December 31: 2016 $ 22,235 $ 187,316 2015 22,230 290,798 2014 53,840 381,812 Weighted-average interest rate at year-end: 2016 0.65 % 0.25 % 2015 0.25 % 0.15 % 2014 0.20 % 0.15 % Maximum amount outstanding at any month’s end: 2016 $ 32,200 $ 353,833 2015 52,000 379,818 2014 53,840 527,904 Average amount outstanding during the year: 2016 $ 22,717 $ 298,494 2015 38,526 283,011 2014 24,037 357,083 Weighted-average interest rate during the year: 2016 0.32 % 0.17 % 2015 0.21 % 0.10 % 2014 0.20 % 0.12 %

Long-Term Borrowings (Tables)

Long-Term Borrowings (Tables)	12 Months Ended
	Dec. 31, 2016
Debt Disclosure [Abstract]
FHLB Advances and Related Weighted Average Interest Rates	At December 31, 2016 and 2015, FHLB advances and the related weighted-average interest rates were as follows: 2016 2015 (Dollars in thousands) Amount Weighted- Weighted- Amount Weighted- Weighted- FHLB advances $ 897,707 0.72 % 0.72 % $ 850,880 0.46 % 0.46 %
Information Related to Statutory Trusts	Information related to United’s statutory trusts is presented in the table below: (Dollars in thousands) Description Issuance Date Amount of Interest Rate Maturity Date Century Trust March 23, 2000 $ 8,800 10.875% Fixed March 8, 2030 United Statutory Trust III December 17, 2003 $ 20,000 3-month LIBOR + 2.85% December 17, 2033 United Statutory Trust IV December 19, 2003 $ 25,000 3-month LIBOR + 2.85% January 23, 2034 United Statutory Trust V July 12, 2007 $ 50,000 3-month LIBOR + 1.55% October 1, 2037 United Statutory Trust VI September 20, 2007 $ 30,000 3-month LIBOR + 1.30% December 15, 2037 Premier Statutory Trust II September 25, 2003 $ 6,000 3-month LIBOR + 3.10% October 8, 2033 Premier Statutory Trust III May 16, 2005 $ 8,000 3-month LIBOR + 1.74% June 15, 2035 Premier Statutory Trust IV June 20, 2006 $14,000 3-month LIBOR + 1.55% September 23, 2036 Premier Statutory Trust V December 14, 2006 $10,000 3-month LIBOR + 1.61% March 1, 2037 Centra Statutory Trust I September 20, 2004 $10,000 3-month LIBOR + 2.29% September 20, 2034 Centra Statutory Trust II June 15, 2006 $10,000 3-month LIBOR + 1.65% July 7, 2036 Virginia Commerce Trust II December 19, 2002 $15,000 6-month LIBOR + 3.30% December 19, 2032 Virginia Commerce Trust III December 20, 2005 $25,000 3-month LIBOR + 1.42% February 23, 2036
Debentures and Related Weighted Average Interest Rates	At December 31, 2016 and 2015, the Debentures and their related weighted-average interest rates were as follows: 2016 2015 (Dollars in thousands) Amount Weighted- Amount Weighted- Century Trust $ 8,800 10.88 % $ 8,800 10.88 % United Statutory Trust III 20,619 3.84 % 20,619 3.38 % United Statutory Trust IV 25,774 3.74 % 25,774 3.17 % United Statutory Trust V 51,547 2.40 % 51,547 1.88 % United Statutory Trust VI 30,928 2.26 % 30,928 1.81 % Premier Statutory Trust II 6,186 3.98 % 6,186 3.42 % Premier Statutory Trust III 8,248 2.70 % 8,248 2.25 % Premier Statutory Trust IV 14,433 2.55 % 14,433 2.14 % Premier Statutory Trust V 10,310 2.54 % 10,310 2.02 % Centra Statutory Trust I 10,000 3.29 % 9,972 2.86 % Centra Statutory Trust II 10,000 2.53 % 9,972 1.97 % Virginia Commerce Trust II 11,784 4.62 % 11,554 4.13 % Virginia Commerce Trust III 15,690 2.34 % 15,163 1.80 % Total $ 224,319 $ 223,506
Schedule of Maturities of Long-term Borrowings	At December 31, 2016, the scheduled maturities of long-term borrowings were as follows: Year Amount (In thousands) 2017 $ 825,606 2018 59,628 2019 34,243 2020 0 2021 and thereafter 252,549 Total $ 1,172,026

Other Expense (Tables)

Other Expense (Tables)	12 Months Ended
	Dec. 31, 2016
Other Income and Expenses [Abstract]
Other Expense	The following details certain items of other expense for the periods indicated: Year Ended December 31 (In thousands) 2016 2015 2014 Legal, consulting & other professional services $ 9,763 $ 9,310 $ 9,620 Franchise & other taxes not on income 7,778 7,055 7,513 Automated Teller Machine (ATM) expenses 7,365 7,107 6,626

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Income Tax Provisions Included in the Consolidated Statements of Income	The income tax provisions included in the consolidated statements of income are summarized as follows: (In thousands) Year Ended December 31 2016 2015 2014 Current (benefit) expense: Federal $ 63,169 $ 58,373 $ 51,001 State 5,154 5,428 3,900 Deferred expense: Federal and State 7,252 1,729 10,097 Total income taxes $ 75,575 $ 65,530 $ 64,998
Reconciliation of Income Tax Expense to the Amount Computed by Applying the Statutory Federal Income Tax Rate	The following is a reconciliation of income tax expense to the amount computed by applying the statutory federal income tax rate to income before income taxes. Year Ended December 31 (Dollars in thousands) 2016 2015 2014 Amount % Amount % Amount % Tax on income before taxes at statutory federal rate $ 77,930 35.0% $ 71,222 35.0% $ 68,210 35.0% Plus: State income taxes net of federal tax benefits 4,084 1.8 3,516 1.7 2,523 1.3 82,014 36.8 74,738 36.7 70,733 36.3 Increase (decrease) resulting from: Tax-exempt interest income (3,919 ) (1.8 ) (4,158 ) (2.0 ) (4,048 ) (2.1 ) Historic tax credit 0 0.0 (1,262 ) (0.6 ) 0 0.0 Other items-net (2,520 ) (1.1 ) (3,788 ) (1.9 ) (1,687 ) (0.8 ) Income taxes $ 75,575 33.9% $ 65,530 32.2% $ 64,998 33.4%
Components of United's Deferred Tax Assets and Liabilities	Significant components of United’s deferred tax assets and liabilities (included in other assets in the Consolidated Balance Sheets) at December 31, 2016 and 2015 are as follows: (In thousands) 2016 2015 Deferred tax assets: Allowance for credit losses $ 26,941 $ 27,874 Other accrued liabilities 3,478 929 Unrecognized components of net periodic pension costs 20,166 20,901 Unrealized loss on securities available for sale 1,436 2,210 Premises and equipment 93 0 Other real estate owned 6,724 7,500 Deferred mortgage points 0 3,575 Purchase accounting intangibles 41,392 15,248 Total deferred tax assets 100,230 78,237 Deferred tax liabilities: Deferred mortgage points 3,608 0 Accrued benefits payable 4,061 5,438 Premises and equipment 0 301 Other 13,687 1,856 Total deferred tax liabilities 21,356 7,595 Net deferred tax assets $ 78,874 $ 70,642
Reconciliation of the Total Amounts of Unrecognized Tax Benefits	Below is a reconciliation of the total amounts of unrecognized tax benefits: December 31 (In thousands) 2016 2015 Unrecognized tax benefits at beginning of year $ 2,102 $ 3,453 Increase in unrecognized tax benefits as a result of tax positions taken during the current period 673 207 Decreases in the unrecognized tax benefits as a result of a lapse of the applicable statute of limitations (333) (1,558) Unrecognized tax benefits at end of year $ 2,442 $ 2,102

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2016
Compensation and Retirement Disclosure [Abstract]
Net Periodic Pension Cost	Net consolidated periodic pension cost included the following components: (Dollars in thousands) Year Ended December 31, 2016 2015 2014 Service cost $ 2,374 $ 2,787 $ 2,160 Interest cost 5,950 5,902 5,379 Expected return on plan assets (8,089) (9,290) (9,102) Recognized net actuarial loss 4,921 4,980 1,994 Amortization of prior service cost 0 1 1 Net periodic pension cost $ 5,156 $ 4,380 $ 432 Weighted-Average Assumptions: Discount rate 4.75% 4.35% 5.20% Expected return on assets 7.25% 7.50% 7.50% Rate of Compensation Increase (prior to age 45) 3.50% 3.50% 3.50% Rate of Compensation Increase (otherwise) 3.00% 3.00% 3.00%
Schedule of Amounts Related to Plan recognized as Component of Other Comprehensive Income	Amounts related to the Plan recognized as a component of other comprehensive income were as follows: (Dollars in thousands) Year Ended December 31, 2016 2015 2014 Net actuarial loss $ 2,914 $ 2,402 $ 29,419 Amortization of: Prior service cost 0 (1) (1) Actuarial loss (4,921) (4,980) (1,994) Total recognized in other comprehensive income $ (2,007) $ (2,579) $ 27,424
Reconciliation of the Beginning and Ending Balances of the Projected Benefit Obligation and the Fair Value of Plan Assets and the Accumulated Benefit Obligation	The reconciliation of the beginning and ending balances of the projected benefit obligation and the fair value of plan assets for the years ended December 31, 2016 and 2015 and the accumulated benefit obligation at December 31, 2016 and 2015 are as follows: (Dollars in thousands) December 31, 2016 2015 Change in Projected Benefit Obligation Projected Benefit Obligation at the Beginning of the Year $ 125,403 $ 135,739 Service Cost 2,374 2,787 Interest Cost 5,950 5,902 Actuarial Loss (Gain) 5,114 (9,760 ) Benefits Paid (4,326 ) (9,265 ) Projected Benefit at the End of the Year $ 134,515 $ 125,403 Accumulated Benefit Obligation at the End of the Year $ 121,548 $ 113,679 Change in Plan Assets Fair Value of Plan Assets at the Beginning of the Year $ 113,748 $ 125,885 Actual Return on Plan Assets 10,289 (2,872 ) Benefits Paid (4,326 ) (9,265 ) Employer Contributions 0 0 Fair value of plan assets at end of year $ 119,711 $ 113,748 Net Amount Recognized Funded Status $ (14,804 ) $ (11,655 ) Unrecognized Transition Asset 0 0 Unrecognized Prior Service Cost 0 0 Unrecognized Net Loss 53,991 55,998 Net Amount Recognized $ 39,187 $ 44,343 Weighted-Average Assumptions at the End of the Year Discount Rate 4.49 % 4.75 % Rate of Compensation Increase (prior to age 45) 3.50 % 3.50 % Rate of Compensation Increase (otherwise) 3.00 % 3.00 %
Asset Allocation for the Defined Benefit Pension Plan as of the Measurement Date, by Asset Category	Asset allocation for the defined benefit pension plan as of the measurement date, by asset category, is as follows: Plan Assets Target Allocation 2017 Allowable Allocation Range Percentage of Plan Assets at December 31, December 31, Equity Securities 66 % 50-70 % 71 % 67% Debt Securities 26 % 20-50 % 26 % 22% Other 8 % 3-15 % 3 % 11% Total 100 % 100%
Expected Benefit Payments	At December 31, 2016, the benefits expected to be paid in each of the next five fiscal years, and in the aggregate for the five years thereafter are as follows: Year Amount (In thousands) 2017 $ 4,626 2018 4,908 2019 5,217 2020 5,568 2021 5,947 2022 through 2026 35,277
Balances of the Plan Assets, by Fair Value Hierarchy Level	The following tables present the balances of the plan assets, by fair value hierarchy level, as of December 31, 2016 and 2015: Fair Value Measurements at December 31, 2016 Using (In thousands) Description Balance as of December 31, 2016 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash and Cash equivalents $ 1,778 $ 1,778 $ 0 $ 0 Fixed Income Securities: Mortgage backed securities 47 0 47 0 Collateralized mortgage obligations 48 0 48 0 Municipal obligations 670 0 670 0 Corporate bonds 1,169 0 1,169 0 Foreign bonds, notes and debentures 96 0 96 0 Fixed Income Mutual Funds: Taxable 26,816 26,816 0 0 Alternative 3,898 3,898 0 0 Equity Securities: Common stock 20,629 20,629 0 0 Equity Mutual Funds: Domestic equity large cap 23,063 23,063 0 0 Domestic equity mid cap 6,457 6,457 0 0 Domestic equity small cap 13,087 13,087 0 0 Domestic equity other 910 910 0 0 International emerging equity 3,120 3,120 0 0 International equity developed 12,619 12,619 0 0 Alternative equity 3,456 3,456 0 0 Domestic Balanced Mutual Funds 1,848 1,848 0 0 Total $ 119,711 $ 117,681 $ 2,030 $ 0 Fair Value Measurements at December 31, 2015 Using (In thousands) Description Balance as of December 31, Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash and Cash equivalents $ 1,467 $ 1,467 $ 0 $ 0 Fixed Income Securities: Mortgage backed securities 63 0 63 0 Collateralized mortgage obligations 54 0 54 0 Municipal obligations 836 0 836 0 Corporate bonds 1,539 0 1,539 0 Foreign bonds, notes and debentures 93 0 93 0 Fixed Income Mutual Funds: Taxable 22,843 22,843 0 0 Alternative 5,067 5,067 0 0 Equity Securities: Common stock 20,464 20,464 0 0 Equity Mutual Funds: Domestic equity large cap 20,470 20,470 0 0 Domestic equity mid cap 5,804 5,804 0 0 Domestic equity small cap 14,080 14,080 0 0 International emerging equity 6,044 6,044 0 0 International equity developed 8,772 8,772 0 0 Alternative equity 6,152 6,152 0 0 Total $ 113,748 $ 111,163 $ 2,585 $ 0

Stock Based Compensation (Table

Stock Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of Stock Option Plans	A summary of activity under the United’s stock option plans as of December 31, 2016, and the changes during the year of 2016 are presented below: Year ended December 31, 2016 Weighted Average (Dollars in thousands, except per share data) Aggregate Remaining Intrinsic Contractual Exercise Shares Value Term (Yrs.) Price Outstanding at January 1, 2016 1,207,110 $ 28.15 Assumed in acquisition of subsidiary 561,570 17.90 Granted 189,780 35.04 Exercised 519,482 19.76 Forfeited or expired 27,243 30.80 Outstanding at December 31, 2016 1,411,735 $ 25,695 5.8 $ 28.05 Exercisable at December 31, 2016 981,457 $ 20,294 4.7 $ 25.57
Changes to United's Restricted Common Shares	The following table summarizes the status of United’s nonvested awards for the year ended December 31, 2016: Shares Weighted-Average Nonvested at January 1, 2016 426,395 $ 6.68 Granted 189,780 6.97 Vested 167,683 6.58 Forfeited or expired 18,214 6.84 Nonvested at December 31, 2016 430,278 $ 6.84
Status of United's Nonvested Stock Option Awards	The following summarizes the changes to United’s restricted common shares for the year ended December 31, 2016: Number of Weighted-Average Outstanding at January 1, 2016 129,772 $ 31.69 Granted 64,092 35.04 Vested 50,641 30.56 Forfeited 5,955 32.97 Outstanding at December 31, 2016 137,268 $ 33.61

Derivative Financial Instrume48

Derivative Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2016
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Derivative Instruments	The following table sets forth certain information regarding interest rate derivatives portfolio used for interest-rate risk management purposes and designated as accounting hedges at December 31, 2016 and 2015. Derivative Hedging Instruments December 31, 2016 December 31, 2015 (Dollars in thousands) Notional Amount Average Pay Rate Notional Amount Average Pay Rate Fair Value Hedges: Pay Fixed Swap (Hedging Commercial Loans) $ 94,582 3.64 % $ 97,157 3.64 % Total Derivatives Used in Fair Value Hedges $ 94,582 $ 97,157 Total Derivatives Used for Interest Rate Risk Management and Designated as Hedges $ 94,582 $ 97,157
Schedule of Fair Value Derivative Financial Instruments	The following tables summarize the fair value of United’s derivative financial instruments: Asset Derivatives December 31, 2016 December 31, 2015 (In thousands) Balance Sheet Location Fair Value Balance Sheet Location Fair Value Derivatives designated as hedging instruments Interest rate contracts Other assets $ 24 Other assets $ 0 Total derivatives designated as hedging instruments $ 24 $ 0 Derivatives not designated as hedging instruments Interest rate contracts Other assets $ 2,267 Other assets $ 2,942 Total derivatives not designated as hedging instruments $ 2,267 $ 2,942 Total asset derivatives $ 2,291 $ 2,942 Liability Derivatives December 31, 2016 December 31, 2015 (In thousands) Balance Sheet Location Fair Value Balance Sheet Location Fair Value Derivatives designated as hedging instruments Interest rate contracts Other liabilities $ 338 Other liabilities $ 1,179 Total derivatives designated as hedging instruments $ 338 $ 1,179 Derivatives not designated as hedging instruments Interest rate contracts Other liabilities $ 2,267 Other liabilities $ 2,942 Total derivatives not designated as hedging instruments $ 2,267 $ 2,942 Total liability derivatives $ 2,605 $ 4,121
Schedule of Derivative Financial Instruments on Statements of Income	The effect of United’s derivative financial instruments on its Consolidated Statements of Income for the years ended December 31, 2016, 2015 and 2014 is presented as follows: Year Ended (In thousands) Income Statement Location December 31, December 31, December 31, Derivatives in fair value hedging relationships Interest rate contracts Interest income/(expense) $ (30 ) $ (813 ) $ (1,047 ) Total derivatives in fair value hedging relationships $ (30 ) $ (813 ) $ (1,047 ) Derivatives not designated as hedging instruments Interest rate contracts (1) Other income $ 0 $ 0 $ 0 Total derivatives not designated as hedging instruments $ 0 $ 0 $ 0 Total derivatives $ (30) $ (813) $ (1,047) (1) Represents net gains and net losses from derivative assets not designated as hedging instruments.

Comprehensive Income (Tables)

Comprehensive Income (Tables)	12 Months Ended
	Dec. 31, 2016
Equity [Abstract]
Components of Total Comprehensive Income	The changes in accumulated other comprehensive income are as follows: For the Years Ended December 31 (In thousands) 2016 2015 2014 Net Income $ 147,083 $ 137,959 $ 129,888 Available for sale (“AFS”) securities: AFS securities with OTTI charges during the period (77) (113) (6,478) Related income tax effect 28 41 2,267 Income tax rate change 208 316 0 Less : OTTI charges recognized in net income 33 47 6,478 Related income tax benefit (12) (17) (2,267) Reclassification of previous noncredit OTTI to credit OTTI 415 0 8,413 Related income tax benefit (150) 0 (2,944) Net unrealized gains on AFS securities with OTTI 445 274 5,469 AFS securities – all other: Change in net unrealized (losses) gains on AFS securities arising during the period (12,931) (6,672) 33,078 Related income tax effect 4,867 2,415 (11,577) Net reclassification adjustment for gains included in net income (255) (133) (3,357) Related income tax expense 92 48 1,175 (8,227 ) (4,342 ) 19,319 Net effect of AFS securities on other comprehensive income (7,782) (4,068) 24,788 Held to maturity (“HTM”) securities: Accretion on the unrealized loss for securities transferred from AFS to the HTM investment portfolio prior to call or maturity 9 8 8 Related income tax expense (3) (3) (3) Net effect of HTM securities on other comprehensive income 6 5 5 Defined benefit pension plan: Net actuarial loss during the period (2,914) (2,402) (29,419) Related income tax expense (benefit) 1,077 944 10,649 Amortization of prior service cost recognized in net income 0 1 1 Related income tax benefit 0 0 0 Amortization of net actuarial loss recognized in net income 4,921 4,980 1,994 Related income tax benefit (1,813) (1,908) (735) Net effect of change in defined benefit pension plan on other comprehensive income 1,271 1,615 (17,510) Total change in other comprehensive income, net of tax (6,505 ) (2,448 ) 7,283 Total Comprehensive Income $ 140,578 $ 135,511 $ 137,171
Components of Accumulated Other Comprehensive Income	The components of accumulated other comprehensive income for the year ended December 31, 2016 are as follows: Changes in Accumulated Other Comprehensive Income (AOCI) by Component (a) For the Year Ended December 31, 2016 (Dollars in thousands) Unrealized Accretion Defined Items Total Balance at January 1, 2016 ($ 2,515 ) ($ 57 ) ($ 35,640 ) ($ 38,212 ) Other comprehensive income before reclassification (7,884 ) 6 0 (7,878 ) Amounts reclassified from accumulated other comprehensive income 102 0 1,271 1,373 Net current-period other comprehensive income, net of tax (7,782 ) 6 1,271 (6,505 ) Balance at December 31, 2016 ($ 10,297 ) ($ 51 ) ($ 34,369 ) ($ 44,717 ) (a) All amounts are net-of-tax.
Reclassifications Out of Accumulated Other Comprehensive Income	Reclassifications out of Accumulated Other Comprehensive Income (AOCI) For the Year Ended December 31, 2016 (Dollars in thousands) Details about AOCI Components Amount Affected Line Item in the Statement Where Net Income is Presented Available for sale (“AFS”) securities: Reclassification of previous noncredit OTTI to credit OTTI $ 415 Total other-than-temporary impairment losses Net reclassification adjustment for losses (gains) included in net income (255 ) Net gains on sales/calls of investment 160 Total before tax Related income tax effect (58 ) Tax expense 102 Net of tax Pension plan: Net actuarial loss (2,914 )(a) Amortization of net actuarial loss 4,921 (b) 2,007 Total before tax Related income tax effect (736 ) Tax expense 1,271 Net of tax Total reclassifications for the period $ 1,373 (a) This AOCI component is included in the computation of changes in plan assets (see Note N, Employee Benefit Plans) (b) This AOCI component is included in the computation of net periodic pension cost (see Note N, Employee Benefit Plans)

United Bankshares, Inc. (Pare50

United Bankshares, Inc. (Parent Company Only) Financial Information (Tables)	12 Months Ended
	Dec. 31, 2016
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Condensed Balance Sheets	Condensed Balance Sheets December 31 (In thousands) 2016 2015 Assets Cash and due from banks $ 129,486 $ 39,680 Securities available for sale 4,108 3,168 Securities held to maturity 20 20 Other investment securities 100 100 Investment in subsidiaries: Bank subsidiaries 2,267,561 1,835,440 Nonbank subsidiaries 6,572 6,484 Other assets 15,404 13,904 Total Assets $ 2,423,251 $ 1,898,796 Liabilities and Shareholders’ Equity Junior subordinated debentures of subsidiary trusts $ 128,868 $ 128,868 Accrued expenses and other liabilities 58,636 57,293 Shareholders’ equity (including other accumulated comprehensive loss of $44,717 and $38,212 at December 31, 2016 and 2015, respectively) 2,235,747 1,712,635 Total Liabilities and Shareholders’ Equity $ 2,423,251 $ 1,898,796
Condensed Statements of Income	Condensed Statements of Income Year Ended December 31 (In thousands) 2016 2015 2014 Income Dividends from banking subsidiaries $ 75,000 $ 70,500 $ 97,000 Net interest income 66 59 59 Management fees: Bank subsidiaries 35,792 28,955 19,400 Nonbank subsidiaries 27 27 27 Other income 8 58 96 Total Income 110,893 99,599 116,582 Expenses Operating expenses 40,180 30,016 24,043 Income Before Income Taxes and Equity in Undistributed Net Income of Subsidiaries 70,713 69,583 92,539 Applicable income tax benefit (1,626 ) (316 ) (1,332 ) Income Before Equity in Undistributed Net Income of Subsidiaries 72,339 69,899 93,871 Equity in undistributed net income of subsidiaries: Bank subsidiaries 74,656 68,012 35,978 Nonbank subsidiaries 88 48 39 Net Income $ 147,083 $ 137,959 $ 129,888
Condensed Statements of Cash Flows	Condensed Statements of Cash Flows Year Ended December 31 (In thousands) 2016 2015 2014 Operating Activities Net income $ 147,083 $ 137,959 $ 129,888 Adjustments to reconcile net income to net cash provided by operating activities: Equity in undistributed net income of subsidiaries (74,744) (68,060) (36,018) Amortization of net periodic pension costs 393 384 34 Stock-based compensation 2,817 2,484 2,195 Net gain on securities transactions (8) (54) (96) Net change in other assets and liabilities (6,401) 8,998 5,172 Net Cash Provided by Operating Activities 69,140 81,711 101,175 Investing Activities Net purchases of securities (234) (1,047) (90) Net cash paid in acquisition of subsidiary (10) 0 (33,271) Increase in investment in subsidiaries (100,000) 0 0 Change in other investment securities 0 2 23 Net Cash Used in Investing Activities (100,244 ) (1,045 ) (33,338 ) Financing Activities Proceeds from issuance of common stock 199,916 0 0 Cash dividends paid (96,351) (88,864) (82,496) Acquisition of treasury stock (1) (1) (2) Proceeds from sale of treasury stock from deferred compensation plan 1 1 81 Excess tax benefits from stock-based compensation arrangements 4,008 1,023 73 Proceeds from exercise of stock options 13,337 7,871 9,878 Net Cash Provided by (Used in) Financing Activities 120,910 (79,970) (72,466) Increase (Decrease) in Cash and Cash Equivalents 89,806 696 (4,629) Cash and Cash Equivalents at Beginning of Year 39,680 38,984 43,613 Cash and Cash Equivalents at End of Year $ 129,486 $ 39,680 $ 38,984

Regulatory Matters (Tables)

Regulatory Matters (Tables)	12 Months Ended
	Dec. 31, 2016
Banking and Thrift [Abstract]
Capital Amounts and Ratios	United’s and its subsidiary banks’, United Bank (WV) and United Bank (VA), capital amounts (in thousands of dollars) and ratios are presented in the following table. (Dollars in thousands) Actual For Capital Adequacy Purposes To Be Well- Capitalized Amount Ratio Amount Ratio Amount Ratio As of December 31, 2016: Total Capital (to Risk-Weighted Assets): United Bankshares $ 1,699,984 14.9 % $ 915,479 ³ $ 1,144,348 ³ United Bank (WV) 638,756 12.2 % 418,700 ³ 523,375 ³ United Bank (VA) 953,891 15.1 % 504,445 ³ 630,557 ³ Tier I Capital (to Risk-Weighted Assets): United Bankshares $ 1,625,543 14.2 % $ 686,609 ³ $ 915,479 ³ United Bank (WV) 590,530 11.3 % 314,025 ³ 418,700 ³ United Bank (VA) 928,301 14.7 % 378,334 ³ 504,445 ³ Common Tier I Capital (to Risk Weighted Assets): United Bankshares $ 1,393,743 12.2 % $ 514,957 ³ $ 743,826 ³ United Bank (WV) 590,530 11.3 % 235,519 ³ 340,194 ³ United Bank (VA) 928,301 14.7 % 283,751 ³ 409,862 ³ Tier I Capital (to Average Assets): United Bankshares $ 1,625,543 12.2 % $ 535,227 ³ $ 669,033 ³ United Bank (WV) 590,530 9.8 % 239,986 ³ 299,983 ³ United Bank (VA) 928,301 11.6 % 318,925 ³ 398,656 ³ As of December 31, 2015: Total Capital (to Risk- Weighted Assets): United Bankshares $ 1,331,492 12.6 % $ 845,876 ³ $ 1,057,345 ³ United Bank (WV) 591,825 12.6 % 377,225 ³ 471,532 ³ United Bank (VA) 720,676 12.2 % 471,303 ³ 589,129 ³ Tier I Capital (to Risk- Weighted Assets): United Bankshares $ 1,254,555 11.9 % $ 634,407 ³ $ 845,876 ³ United Bank (WV) 547,903 11.6 % 282,919 ³ 377,225 ³ United Bank (VA) 687,937 11.7 % 353,477 ³ 471,303 ³ Common Tier I Capital (to Risk Weighted Assets): United Bankshares $ 1,022,755 9.7 % $ 475,805 ³ $ 687,274 ³ United Bank (WV) 547,903 11.6 % 212,189 ³ 306,496 ³ United Bank (VA) 687,937 11.7 % 265,108 ³ 382,934 ³ Tier I Capital (to Average Assets): United Bankshares $ 1,254,555 10.7 % $ 468,776 ³ $ 585,970 ³ United Bank (WV) 547,903 10.2 % 214,519 ³ 268,149 ³ United Bank (VA) 687,937 10.5 % 263,306 ³ 329,132 ³

Fair Values of Financial Inst52

Fair Values of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Schedule of Financial Assets and Liabilities Measured at Fair Value	The following table presents the balances of financial assets and liabilities measured at fair value on a recurring basis as of December 31, 2016 and 2015, segregated by the level of the valuation inputs within the fair value hierarchy: Fair Value at December 31, 2016 Using (In thousands) Description Balance as of December 31, 2016 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets Available for sale debt securities: U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 95,786 $ 0 $ 95,786 $ 0 State and political subdivisions 192,812 0 192,812 0 Residential mortgage-backed securities Agency 584,096 0 584,096 0 Non-agency 7,043 0 7,043 0 Asset-backed securities 217 0 217 0 Commercial mortgage-backed securities Agency 305,341 0 305,341 0 Trust preferred collateralized debt obligations 33,552 0 0 33,552 Single issue trust preferred securities 11,477 0 11,477 0 Other corporate securities 15,062 0 15,062 0 Total available for sale debt securities 1,245,386 0 1,211,834 33,552 Available for sale equity securities: Financial services industry 10,735 1,372 9,363 0 Equity mutual funds (1) 1,820 1,820 0 0 Other equity securities 1,273 1,273 0 0 Total available for sale equity securities 13,828 4,465 9,363 0 Total available for sale securities 1,259,214 4,465 1,221,197 33,552 Derivative financial assets: Interest rate contracts 2,291 0 2,291 0 Liabilities Derivative financial liabilities: Interest rate contracts 2,605 0 2,605 0 (1) The equity mutual funds are within a rabbi trust for the payment of benefits under a deferred compensation plan for certain key officers of United and its subsidiaries. Fair Value at December 31, 2015 Using (In thousands) Description Balance as of December 31, 2015 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets Available for sale debt securities: U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 73,786 $ 0 $ 73,786 $ 0 State and political subdivisions 133,778 0 133,778 0 Residential mortgage-backed securities Agency 477,982 0 477,982 0 Non-agency 9,571 0 9,571 0 Asset-backed securities 3,399 0 3,399 0 Commercial mortgage-backed securities Agency 305,935 0 305,935 0 Trust preferred collateralized debt obligations 34,686 0 0 34,686 Single issue trust preferred securities 11,693 0 11,693 0 Other corporate securities 10,049 0 10,049 0 Total available for sale debt securities 1,060,879 0 1,026,193 34,686 Available for sale equity securities: Financial services industry 2,723 800 1,923 0 Equity mutual funds (1) 1,596 1,596 0 0 Other equity securities 1,136 1,136 0 0 Total available for sale equity securities 5,455 3,532 1,923 0 Total available for sale securities 1,066,334 3,532 1,028,116 34,686 Derivative financial assets: Interest rate contracts 2,942 0 2,942 0 Liabilities Derivative financial liabilities: Interest rate contracts 4,121 0 4,121 0 (1) The equity mutual funds are within a rabbi trust for the payment of benefits under a deferred compensation plan for certain key officers of United and its subsidiaries.
Schedule of Additional Information about Financial Assets and Liabilities Measured at Fair Value Utilized Level 3	The following table presents additional information about financial assets and liabilities measured at fair value at December 31, 2016 and 2015 on a recurring basis and for which United has utilized Level 3 inputs to determine fair value: Available-for-sale (In thousands) Trust preferred collateralized debt obligations 2016 2015 Balance, beginning of year $ 34,686 $ 39,558 Total gains or losses (realized/unrealized): Included in earnings (or changes in net assets) 0 (34 ) Included in other comprehensive income (1,134 ) (4,838 ) Purchases, issuances, and settlements 0 0 Transfers in and/or out of Level 3 0 0 Balance, ending of year $ 33,552 $ 34,686 The amount of total gains or losses for the period included in earnings (or changes in net assets) attributable to the change in unrealized gains or losses relating to assets still held at reporting date 0 0
Summary of Financial Assets Measured at Fair Value on Nonrecurring Basis	The following table summarizes United’s financial assets that were measured at fair value on a nonrecurring basis as of December 31, 2016 and 2015: (In thousands) Description Balance as of December 31, 2016 Fair Value at December 31, 2016 Using YTD Losses Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets Impaired Loans $ 80,505 $ 0 $ 27,609 $ 52,896 $ 5,119 OREO 31,510 0 31,510 0 2,086 (In thousands) Description Balance as of December 31, 2015 Fair Value at December 31, 2015 Using YTD Losses Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets Impaired Loans $ 69,368 $ 0 $ 29,186 $ 40,182 $ 8,485 OREO 32,228 0 32,228 0 1,141
Summary of Estimated Fair Values of Financial Instruments	The estimated fair values of United’s financial instruments are summarized below: Fair Value Measurements (In thousands) Carrying Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) December 31, 2016 Cash and cash equivalents $ 1,434,527 $ 1,434,527 $ 0 $ 1,434,527 $ 0 Securities available for sale 1,259,214 1,259,214 4,465 1,221,197 33,552 Securities held to maturity 33,258 31,178 0 28,158 3,020 Other securities 111,166 105,608 0 0 105,608 Loans held for sale 8,445 8,445 0 8,445 0 Loans 10,268,366 10,122,486 0 0 10,122,486 Derivative financial assets 2,291 2,291 0 2,291 0 Deposits 10,796,867 10,785,294 0 10,785,294 0 Short-term borrowings 209,551 209,551 0 209,551 0 Long-term borrowings 1,172,026 1,142,782 0 1,142,782 0 Derivative financial liabilities 2,605 2,605 0 2,605 0 December 31, 2015 Cash and cash equivalents $ 857,335 $ 857,335 $ 0 $ 857,335 $ 0 Securities available for sale 1,066,334 1,066,334 3,532 1,028,116 34,686 Securities held to maturity 39,099 36,319 0 33,299 3,020 Other securities 98,749 93,811 0 0 93,811 Loans held for sale 10,681 10,681 0 10,681 0 Loans 9,308,354 9,289,463 0 0 9,289,463 Derivative financial assets 2,942 2,942 0 2,942 0 Deposits 9,341,527 9,332,451 0 9,332,451 0 Short-term borrowings 423,028 423,028 0 423,028 0 Long-term borrowings 1,015,249 988,270 0 988,270 0 Derivative financial liabilities 4,121 4,121 0 4,121 0

Variable Interest Entities (Tab

Variable Interest Entities (Tables)	12 Months Ended
	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Summary of Quantitative Information Related to Significant Involvement in Unconsolidated Variable Interest Entities	The following table summarizes quantitative information about United’s significant involvement in unconsolidated VIEs: As of December 31, 2016 As of December 31, 2015 (In thousands) Aggregate Assets Aggregate Liabilities Risk Of Loss (1) Aggregate Assets Aggregate Liabilities Risk Of Loss (1) Trust preferred securities $ 240,668 $ 232,583 $ 8,085 $ 240,468 $ 232,492 $ 7,976 (1) Represents investment in VIEs.

Quarterly Financial Data (Table

Quarterly Financial Data (Tables)	12 Months Ended
	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Data	Quarterly financial data for 2016 and 2015 is summarized below (dollars in thousands, except for per share data): (Dollars in thousands) 1st Quarter 2nd Quarter 3rd Quarter 4th Quarter 2016 Interest income $ 108,496 $ 113,087 $ 123,137 $ 125,621 Interest expense 10,212 10,362 12,068 12,368 Net interest income 98,284 102,725 111,069 113,253 Provision for credit losses 4,035 7,667 6,988 5,819 Mortgage banking income 728 789 982 951 Securities gains (losses), net 4 213 1 62 Other noninterest income 15,660 16,965 18,038 15,639 Noninterest expense 58,056 64,855 62,777 62,508 Income taxes 17,879 16,378 18,846 22,472 Net income (1) 34,706 31,792 41,479 39,106 Per share data: Average shares outstanding (000s): Basic 69,497 71,484 76,219 76,864 Diluted 69,714 71,809 76,648 77,303 Net income per share: Basic $ 0.50 $ 0.44 $ 0.54 $ 0.51 Diluted $ 0.50 $ 0.44 $ 0.54 $ 0.51 Dividends per share $ 0.33 $ 0.33 $ 0.33 $ 0.33 2015 Interest income $ 104,549 $ 105,532 $ 106,309 $ 107,240 Interest expense 9,800 9,630 9,991 10,085 Net interest income 94,749 95,902 96,318 97,155 Provision for credit losses 5,354 5,716 5,182 6,322 Mortgage banking income 545 663 665 634 Securities losses, net 12 3 111 29 Other noninterest income 17,634 18,832 17,036 17,462 Noninterest expense 57,655 57,730 57,684 58,618 Income taxes 15,304 17,145 16,217 16,864 Net income (1) 34,627 34,809 35,047 33,476 Per share data: Average shares outstanding (000s): Basic 69,208 69,306 69,391 69,432 Diluted 69,477 69,587 69,690 69,737 Net income per share: Basic $ 0.50 $ 0.50 $ 0.50 $ 0.48 Diluted $ 0.50 $ 0.50 $ 0.50 $ 0.48 Dividends per share $ 0.32 $ 0.32 $ 0.32 $ 0.33 (1) For further information, see the related discussion “Quarterly Results” included in Management’s Discussion and Analysis.

Summary of Significant Accoun55

Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2016USD ($)Region	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)
Summary Of Significant Accounting Policies [Line Items]
Number of Metropolitan Statistical Areas | Region	5
Loan fees net of costs amortized and included in interest income	$ 18,471,000	$ 15,798,000	$ 16,697,000
Minimum days, related to accrual of interest on discontinued commercial and consumer loans	90 days
Maximum days, related to accrual of interest on discontinued commercial and consumer loans	120 days
Sustained period of repayment performance in restructured loans	6 months
Real estate acquired in foreclosure or other settlement of loans	$ 31,510,000	32,228,000
Recorded investment of consumer mortgage loans	660,000	234,000
Advertising expense	3,410,000	4,111,000	4,759,000
Amortization expense on intangible assets	3,944,000	3,420,000	4,021,000
Total goodwill	863,767,000	710,252,000
Stock based compensation expense	$ 2,817,000	$ 2,484,000	$ 2,195,000
Minimum [Member] | Core Deposit Intangible Assets [Member]
Summary Of Significant Accounting Policies [Line Items]
Intangible assets amortization period	1 year
Maximum [Member] | Core Deposit Intangible Assets [Member]
Summary Of Significant Accounting Policies [Line Items]
Intangible assets amortization period	7 years
Furniture, Fixtures and Equipment [Member] | Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Bank premises and equipment, useful life	3 years
Furniture, Fixtures and Equipment [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Bank premises and equipment, useful life	15 years
Buildings and Improvements [Member] | Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Bank premises and equipment, useful life	5 years
Buildings and Improvements [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Bank premises and equipment, useful life	40 years

Summary of Significant Accoun56

Summary of Significant Accounting Policies - Reconciliation of Numerator and Denominator of Basic Earnings Per Share with that of Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share [Abstract]
Distributed earnings allocated to common stock									$ 98,510	$ 89,497	$ 88,353
Undistributed earnings allocated to common stock									48,317	48,218	41,305
Net earnings allocated to common shareholders									$ 146,827	$ 137,715	$ 129,658
Average common shares outstanding	76,864,000	76,219,000	71,484,000	69,497,000	69,432,000	69,391,000	69,306,000	69,208,000	73,531,992	69,334,849	67,404,254
Dilutive effect of stock compensation									361,135	290,682	244,419
Average diluted shares outstanding	77,303,000	76,648,000	71,809,000	69,714,000	69,737,000	69,690,000	69,587,000	69,477,000	73,893,127	69,625,531	67,648,673
Earnings per basic common share	$ 0.51	$ 0.54	$ 0.44	$ 0.50	$ 0.48	$ 0.50	$ 0.50	$ 0.50	$ 2	$ 1.99	$ 1.93
Earnings per diluted common share	$ 0.51	$ 0.54	$ 0.44	$ 0.50	$ 0.48	$ 0.50	$ 0.50	$ 0.50	$ 1.99	$ 1.98	$ 1.92

Mergers and Acquisitions - Addi

Mergers and Acquisitions - Additional Information (Detail)	Jun. 03, 2016USD ($)$ / sharesshares	Dec. 31, 2016USD ($)Banking_Office$ / shares	Dec. 31, 2015USD ($)
Business Acquisition [Line Items]
Total assets at consummation		$ 14,508,892,000	$ 12,577,944,000
Loans at consummation		10,356,719,000	9,398,952,000
Deposits at consummation		10,796,867,000	9,341,527,000
Resulting goodwill		863,767,000	$ 710,252,000
Liabilities to provide severance benefits		0
Contractually required principal and interest at acquisition	$ 138,125
Expected cash flows at acquisition	117,564
Estimated fair value of acquired impaired loans at acquisition	95,570
Merger-related expenses		$ 5,406,000
Cardinal Financial Corporation [Member]
Business Acquisition [Line Items]
Business acquisition date		Aug. 17, 2016
Exchange ratio		0.71
Business acquisition, share price | $ / shares		$ 2.50
Total assets at consummation		$ 4,210,514,000
Number of banking offices acquired | Banking_Office		30
Bank of Georgetown [Member]
Business Acquisition [Line Items]
Total assets at consummation		$ 1,278,837,000
Outstanding common stock acquired		100.00%
Loans at consummation		$ 999,773,000
Deposits at consummation		971,369,000
Common stock paid in cash	264,505,000
Common stock value	253,799,000
Stock options exchanged value	$ 10,696,000
Common stock, shares issued | shares	6,527,746
Resulting goodwill	$ 152,845,000
Fractional shares cash paid per share	10,000
Goodwill from acquisition expected to be tax deductible	0
Downward fair value adjustment on loans acquired	41,745,000
Premium on interest-bearing deposits acquired	$ 316,000
Assumed liabilities to provide severance benefits		300,000
Downward fair value adjustment on leasehold improvements		1,550,000
Premium on long-term FHLB advances acquired		2,659,000
Estimated remaining life of premium on interest-bearing deposits acquired	1 year 29 days
Estimated remaining life of the FHLB advances acquired	8 years 8 months 1 day
Contractually required principal and interest at acquisition	$ 1,275,398,000
Expected cash flows at acquisition	1,241,685,000
Estimated fair value of acquired impaired loans at acquisition	968,197,000
Revenue since acquisition included in consolidated results		122,545,000
Revenue since acquisition included in consolidated results		$ 61,253,000
Bank of Georgetown [Member] | Common Stock [Member]
Business Acquisition [Line Items]
Common stock value	$ 253,799,000
Common stock, shares issued | shares	6,527,746
Closing market price per common share | $ / shares	$ 38.88
Bank of Georgetown [Member] | Core Deposit Intangible Assets [Member]
Business Acquisition [Line Items]
Purchase price allocation of Identifiable Intangible assets	$ 9,058,000
Estimated period of amortization of core deposit intangibles	10 years
Fractional shares cash paid per share	$ 10,000

Mergers and Acquisitions - Sche

Mergers and Acquisitions - Schedule of Acquired Loans Accounted for at Fair Value (Detail)	Jun. 03, 2016USD ($)
Business Acquisition [Line Items]
Contractually required principal and interest at acquisition	$ 138,125
Expected cash flows at acquisition	117,564
Basis in acquired loans at acquisition - estimated fair value	95,570
Bank of Georgetown [Member]
Business Acquisition [Line Items]
Contractually required principal and interest at acquisition	1,275,398,000
Contractual cash flows not expected to be collected	(33,713,000)
Expected cash flows at acquisition	1,241,685,000
Interest component of expected cash flows	(273,488,000)
Basis in acquired loans at acquisition - estimated fair value	$ 968,197,000

Mergers and Acquisitions - Sc59

Mergers and Acquisitions - Schedule of Expected Fair Value of Acquired Identifiable Assets and Liabilities Assumed (Detail) - USD ($) $ in Thousands	Jun. 03, 2016	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Preliminary resulting goodwill		$ 863,767	$ 710,252
Bank of Georgetown [Member]
Business Acquisition [Line Items]
Value of common shares issued (6,527,746 shares)	$ 253,799
Fair value of stock options assumed	10,696
Cash for fractional shares	10
Total purchase price	264,505
Cash and cash equivalents	29,340
Investment securities	219,783
Loans	968,197
Premises and equipment	5,574
Other assets	31,605
Total identifiable assets	1,263,557
Deposits	971,685
Short-term borrowings	101,021
Long-term borrowings	67,659
Other liabilities	11,532
Total identifiable liabilities	1,151,897
Preliminary fair value of net assets acquired including identifiable intangible assets	111,660
Preliminary resulting goodwill	152,845
Bank of Georgetown [Member] | Core Deposit Intangible Assets [Member]
Business Acquisition [Line Items]
Cash for fractional shares	10
Core deposit intangibles	$ 9,058

Mergers and Acquisitions - Sc60

Mergers and Acquisitions - Schedule of Expected Fair Value of Acquired Identifiable Assets and Liabilities Assumed (Parenthetical) (Detail)	Jun. 03, 2016shares
Bank of Georgetown [Member]
Business Acquisition [Line Items]
Common stock, shares issued	6,527,746

Mergers and Acquisitions - Sc61

Mergers and Acquisitions - Schedule of Business Acquisition Pro Forma Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Business Combinations [Abstract]
Total Revenues	$ 519,011	$ 509,312
Net Income	$ 148,226	$ 150,910

Investment Securities - Summary

Investment Securities - Summary of Amortized Cost and Estimated Fair Values of Available for Sale Securities (Detail) - USD ($)	Dec. 31, 2016	Dec. 31, 2015
Schedule of Investments [Line Items]
Amortized Cost	$ 1,277,639,000	$ 1,072,340,000
Gross Unrealized Gains	10,912,000	14,388,000
Gross Unrealized Losses	29,337,000	20,394,000
Estimated Fair Value	1,259,214,000	1,066,334,000
Cumulative OTTI in AOCI	26,038,000	26,410,000
U.S. Treasury Securities and Obligations of U.S. Government Corporations and Agencies [Member]
Schedule of Investments [Line Items]
Amortized Cost	95,247,000	71,993,000
Gross Unrealized Gains	698,000	1,793,000
Gross Unrealized Losses	159,000	0
Estimated Fair Value	95,786,000	73,786,000
Cumulative OTTI in AOCI	0	0
State and Political Subdivisions [Member]
Schedule of Investments [Line Items]
Amortized Cost	196,350,000	130,685,000
Gross Unrealized Gains	1,364,000	3,144,000
Gross Unrealized Losses	4,902,000	51,000
Estimated Fair Value	192,812,000	133,778,000
Cumulative OTTI in AOCI	0	0
Residential Mortgage-Backed Securities, Agency [Member]
Schedule of Investments [Line Items]
Amortized Cost	585,208,000	473,109,000
Gross Unrealized Gains	3,999,000	5,580,000
Gross Unrealized Losses	5,111,000	707,000
Estimated Fair Value	584,096,000	477,982,000
Cumulative OTTI in AOCI	0	0
Residential Mortgage-Backed Securities, Non-agency [Member]
Schedule of Investments [Line Items]
Amortized Cost	6,629,000	9,119,000
Gross Unrealized Gains	426,000	457,000
Gross Unrealized Losses	12,000	5,000
Estimated Fair Value	7,043,000	9,571,000
Cumulative OTTI in AOCI	86,000	458,000
Commercial Mortgage-Backed Securities, Agency [Member]
Schedule of Investments [Line Items]
Amortized Cost	304,635,000	305,990,000
Gross Unrealized Gains	1,948,000	1,843,000
Gross Unrealized Losses	1,242,000	1,898,000
Estimated Fair Value	305,341,000	305,935,000
Cumulative OTTI in AOCI	0	0
Asset-Backed Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	217,000	3,404,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	5,000
Estimated Fair Value	217,000	3,399,000
Cumulative OTTI in AOCI	0	0
Trust Preferred Collateralized Debt Obligations [Member]
Schedule of Investments [Line Items]
Amortized Cost	48,558,000	49,386,000
Gross Unrealized Gains	729,000	635,000
Gross Unrealized Losses	15,735,000	15,335,000
Estimated Fair Value	33,552,000	34,686,000
Cumulative OTTI in AOCI	25,952,000	25,952,000
Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	13,363,000	13,811,000
Gross Unrealized Gains	284,000	249,000
Gross Unrealized Losses	2,170,000	2,367,000
Estimated Fair Value	11,477,000	11,693,000
Cumulative OTTI in AOCI	0	0
Corporate Bonds [Member]
Schedule of Investments [Line Items]
Amortized Cost	14,996,000	9,999,000
Gross Unrealized Gains	66,000	50,000
Gross Unrealized Losses	0	0
Estimated Fair Value	15,062,000	10,049,000
Cumulative OTTI in AOCI	0	0
Marketable Equity Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	12,436,000	4,844,000
Gross Unrealized Gains	1,398,000	637,000
Gross Unrealized Losses	6,000	26,000
Estimated Fair Value	13,828,000	5,455,000
Cumulative OTTI in AOCI	$ 0	$ 0

Investment Securities - Summa63

Investment Securities - Summary of Securities Available for Sale in an Unrealized Loss Position (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	$ 612,613	$ 288,156
Less than 12 months, Unrealized Losses	11,420	2,983
12 months or longer, Fair Value	36,982	41,608
12 months or longer, Unrealized Losses	17,917	17,411
U.S. Treasury Securities and Obligations of U.S. Government Corporations and Agencies [Member]
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	24,101	0
Less than 12 months, Unrealized Losses	159	0
12 months or longer, Fair Value	0	0
12 months or longer, Unrealized Losses	0	0
State and Political Subdivisions [Member]
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	116,300	15,550
Less than 12 months, Unrealized Losses	4,902	51
12 months or longer, Fair Value	0	0
12 months or longer, Unrealized Losses	0	0
Residential Mortgage-Backed Securities, Agency [Member]
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	309,376	90,004
Less than 12 months, Unrealized Losses	5,111	707
12 months or longer, Fair Value	0	0
12 months or longer, Unrealized Losses	0	0
Residential Mortgage-Backed Securities, Non-agency [Member]
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	0	348
Less than 12 months, Unrealized Losses	0	5
12 months or longer, Fair Value	218	0
12 months or longer, Unrealized Losses	12	0
Commercial Mortgage-Backed Securities, Agency [Member]
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	162,479	170,340
Less than 12 months, Unrealized Losses	1,242	1,650
12 months or longer, Fair Value	0	9,255
12 months or longer, Unrealized Losses	0	248
Asset-Backed Securities [Member]
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	0	3,399
Less than 12 months, Unrealized Losses	0	5
12 months or longer, Fair Value	0	0
12 months or longer, Unrealized Losses	0	0
Trust Preferred Collateralized Debt Obligations [Member]
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	0	3,304
Less than 12 months, Unrealized Losses	0	135
12 months or longer, Fair Value	28,579	28,633
12 months or longer, Unrealized Losses	15,735	15,200
Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	0	4,225
Less than 12 months, Unrealized Losses	0	404
12 months or longer, Fair Value	8,185	3,720
12 months or longer, Unrealized Losses	2,170	1,963
Marketable Equity Securities [Member]
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	357	986
Less than 12 months, Unrealized Losses	6	26
12 months or longer, Fair Value	0	0
12 months or longer, Unrealized Losses	$ 0	$ 0

Investment Securities - Summa64

Investment Securities - Summary of Gains or Losses on Proceeds from Maturities, Sales and Calls of Available for Sale Securities by Specific Identification Method (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Investments, Debt and Equity Securities [Abstract]
Proceeds from maturities, sales and calls	$ 513,990	$ 191,266	$ 534,489
Gross realized gains	268	143	3,592
Gross realized losses	$ 13	$ 10	$ 235

Investment Securities - Additio

Investment Securities - Additional Information (Detail)	3 Months Ended	12 Months Ended		96 Months Ended
	Dec. 31, 2016USD ($)Securities	Dec. 31, 2016USD ($)Securities	Dec. 31, 2015USD ($)	Dec. 31, 2007USD ($)
Schedule of Investments [Line Items]
Gross unrealized losses on available for sale securities	$ 29,337,000	$ 29,337,000	$ 20,394,000
Available for sale securities in unrealized loss position | Securities	347	347
Available for sale securities in portfolio, number | Securities	640	640
Amortized cost of available for sale securities	$ 1,277,639,000	$ 1,277,639,000	1,072,340,000
Capitalization of banks, equal to or greater than, in the single-issue trust preferred portfolio	10,000,000,000	10,000,000,000
Noncredit-related other-than-temporary impairment recognized	26,038,000	$ 26,038,000	26,410,000
New issuance of Preferred Stock estimated				$ 60,000,000,000
Security other-than-temporarily impaired		100.00%
Cost of equity securities	12,436,000	$ 12,436,000
Available-for-sale securities estimated fair value	1,259,214,000	1,259,214,000	1,066,334,000
Held-to-maturity securities amortized cost	33,258,000	33,258,000	39,099,000
Held-to-maturity securities estimated fair value	31,178,000	31,178,000	36,319,000
Carrying value of securities pledged	1,137,408,000	1,137,408,000	986,982,000
Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale securities amortized cost	896,472,000	896,472,000
Available-for-sale securities estimated fair value	896,480,000	896,480,000
Held-to-maturity securities amortized cost	30,000	30,000
Held-to-maturity securities estimated fair value	35,000	35,000
Net unrealized gains		13,000	5,276,000
TRUP CDOs [Member]
Schedule of Investments [Line Items]
Credit-related other-than-temporary impairment recognized in earnings	0	0	34,000
Noncredit-related other-than-temporary impairment recognized	25,952,000	25,952,000	25,952,000
Wells Fargo [Member]
Schedule of Investments [Line Items]
Amortized cost of trust preferred securities	9,922,000	9,922,000
SunTrust Bank [Member]
Schedule of Investments [Line Items]
Amortized cost of trust preferred securities	7,418,000	7,418,000
Royal Bank of Scotland [Member]
Schedule of Investments [Line Items]
Amortized cost of trust preferred securities	976,000	$ 976,000
Minimum [Member]
Schedule of Investments [Line Items]
Other-than-temporarily impaired, the collateralization ratios		104.20%
Maximum [Member]
Schedule of Investments [Line Items]
Other-than-temporarily impaired, the collateralization ratios		344.20%
Median [Member]
Schedule of Investments [Line Items]
Other-than-temporarily impaired, the collateralization ratios		158.60%
Weighted Average [Member]
Schedule of Investments [Line Items]
Other-than-temporarily impaired, the collateralization ratios		221.90%
Investment Grade [Member]
Schedule of Investments [Line Items]
Amortized cost of available for sale single issue trust preferred securities	3,008,000	$ 3,008,000
Investment Grade [Member] | TRUP CDOs [Member]
Schedule of Investments [Line Items]
Amortized cost of available for sale securities	3,847,000	3,847,000
Below Investment Grade [Member]
Schedule of Investments [Line Items]
Amortized cost of available for sale single issue trust preferred securities	5,697,000	5,697,000
Below Investment Grade [Member] | TRUP CDOs [Member]
Schedule of Investments [Line Items]
Amortized cost of available for sale securities	40,468,000	40,468,000
Split Rated [Member]
Schedule of Investments [Line Items]
Amortized cost of available for sale single issue trust preferred securities	4,658,000	4,658,000
U.S. Treasury Securities and Obligations of U.S. Government Corporations and Agencies [Member]
Schedule of Investments [Line Items]
Gross unrealized losses on available for sale securities	159,000	159,000	0
Amortized cost of available for sale securities	95,247,000	95,247,000	71,993,000
Noncredit-related other-than-temporary impairment recognized	0	0	0
Available-for-sale securities estimated fair value	95,786,000	95,786,000	73,786,000
Held-to-maturity securities amortized cost	5,295,000	5,295,000	10,425,000
Held-to-maturity securities estimated fair value	5,865,000	$ 5,865,000	11,285,000
Aggregate book value percentage of securities to shareholders' equity		10.00%
Residential Mortgage-Backed Securities, Non-agency [Member]
Schedule of Investments [Line Items]
Gross unrealized losses on available for sale securities	12,000	$ 12,000	5,000
Amortized cost of available for sale securities	6,629,000	6,629,000	9,119,000
Noncredit-related other-than-temporary impairment recognized	86,000	86,000	458,000
Available-for-sale securities estimated fair value	7,043,000	$ 7,043,000	9,571,000
Residential Mortgage-Backed Securities, Non-agency [Member] | Originated Prior to 2005 [Member]
Schedule of Investments [Line Items]
Percentage of portfolio of non-agency mortgage backed securities with collateral		23.00%
Residential Mortgage-Backed Securities, Non-agency [Member] | Originated in 2006 and 2007 [Member]
Schedule of Investments [Line Items]
Percentage of portfolio of non-agency mortgage backed securities with collateral		77.00%
Residential Mortgage-Backed Securities, Non-agency [Member] | Investment Grade [Member]
Schedule of Investments [Line Items]
Amortized cost of available for sale securities	1,054,000	$ 1,054,000
Residential Mortgage-Backed Securities, Non-agency [Member] | Below Investment Grade [Member]
Schedule of Investments [Line Items]
Amortized cost of available for sale securities	5,575,000	5,575,000
Agency Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Amortized cost of available for sale securities	889,843,000	889,843,000
Commercial Mortgage-Backed Securities, Agency [Member]
Schedule of Investments [Line Items]
Gross unrealized losses on available for sale securities	1,242,000	1,242,000	1,898,000
Amortized cost of available for sale securities	304,635,000	304,635,000	305,990,000
Noncredit-related other-than-temporary impairment recognized	0	0	0
Available-for-sale securities estimated fair value	305,341,000	305,341,000	305,935,000
Residential Mortgage-Backed Securities, Agency [Member]
Schedule of Investments [Line Items]
Gross unrealized losses on available for sale securities	5,111,000	5,111,000	707,000
Amortized cost of available for sale securities	585,208,000	585,208,000	473,109,000
Noncredit-related other-than-temporary impairment recognized	0	0	0
Available-for-sale securities estimated fair value	584,096,000	584,096,000	477,982,000
Held-to-maturity securities amortized cost	30,000	30,000	35,000
Held-to-maturity securities estimated fair value	35,000	35,000	41,000
Marketable Equity Securities [Member]
Schedule of Investments [Line Items]
Gross unrealized losses on available for sale securities	6,000	6,000	26,000
Amortized cost of available for sale securities	$ 12,436,000	$ 12,436,000	4,844,000
Number of equity securities other-than-temporarily impaired | Securities	0	0
Noncredit-related other-than-temporary impairment recognized	$ 0	$ 0	0
Available-for-sale securities estimated fair value	13,828,000	13,828,000	5,455,000
State and Political Subdivisions [Member]
Schedule of Investments [Line Items]
Gross unrealized losses on available for sale securities	4,902,000	4,902,000	51,000
Amortized cost of available for sale securities	$ 196,350,000	$ 196,350,000	130,685,000
Percent of portfolio with credit support	81.00%	81.00%
Investment grade credit rate percentage		1.00%
Number of equity securities other-than-temporarily impaired | Securities	0	0
Noncredit-related other-than-temporary impairment recognized	$ 0	$ 0	0
Available-for-sale securities estimated fair value	192,812,000	192,812,000	133,778,000
Held-to-maturity securities amortized cost	8,598,000	8,598,000	9,321,000
Held-to-maturity securities estimated fair value	$ 8,615,000	$ 8,615,000	$ 9,089,000

Investment Securities - Summa66

Investment Securities - Summary of Unrealized Loss Positions of Available for Sale TRUP CDOs and Single Issue Trust Preferred Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Schedule of Investments [Line Items]
Amortized Cost	$ 1,277,639	$ 1,072,340
Fair Value	1,259,214	$ 1,066,334
Trup CDOs and Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	48,558
Fair Value	33,552
Net Unrealized Loss	15,006
Senior - Bank [Member] | Trup CDOs and Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	5,988
Fair Value	5,545
Net Unrealized Loss	443
Mezzanine - Bank (now in senior position) [Member] | Trup CDOs and Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	11,309
Fair Value	8,175
Net Unrealized Loss	3,134
Mezzanine - Bank [Member] | Trup CDOs and Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	26,095
Fair Value	16,170
Net Unrealized Loss	9,925
Mezzanine - Bank & Insurance (combination) [Member] | Trup CDOs and Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	5,166
Fair Value	3,662
Net Unrealized Loss	1,504
Investment Grade [Member] | Trup CDOs and Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	3,847
Investment Grade [Member] | Senior - Bank [Member] | Trup CDOs and Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	3,847
Investment Grade [Member] | Mezzanine - Bank (now in senior position) [Member] | Trup CDOs and Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	0
Investment Grade [Member] | Mezzanine - Bank [Member] | Trup CDOs and Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	0
Investment Grade [Member] | Mezzanine - Bank & Insurance (combination) [Member] | Trup CDOs and Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	0
Split Rated [Member] | Trup CDOs and Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	0
Split Rated [Member] | Senior - Bank [Member] | Trup CDOs and Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	0
Split Rated [Member] | Mezzanine - Bank (now in senior position) [Member] | Trup CDOs and Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	0
Split Rated [Member] | Mezzanine - Bank [Member] | Trup CDOs and Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	0
Split Rated [Member] | Mezzanine - Bank & Insurance (combination) [Member] | Trup CDOs and Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	0
Below Investment Grade [Member] | Trup CDOs and Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	44,711
Below Investment Grade [Member] | Senior - Bank [Member] | Trup CDOs and Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	2,141
Below Investment Grade [Member] | Mezzanine - Bank (now in senior position) [Member] | Trup CDOs and Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	11,309
Below Investment Grade [Member] | Mezzanine - Bank [Member] | Trup CDOs and Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	26,095
Below Investment Grade [Member] | Mezzanine - Bank & Insurance (combination) [Member] | Trup CDOs and Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	$ 5,166

Investment Securities - Roll Fo

Investment Securities - Roll Forward of Credit Losses on Securities (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Investments, Debt and Equity Securities [Abstract]
Cumulative credit losses, Beginning Balance	$ 23,773	$ 23,739	$ 40,663
Additional credit losses on securities for which OTTI was previously recognized	33	34	6,442
Reductions for securities sold or paid off during the period	(1,644)	0	(23,366)
Cumulative credit losses, Ending Balance	$ 22,162	$ 23,773	$ 23,739

Investment Securities - Summa68

Investment Securities - Summary of Maturities of Securities Available for Sale by Amortized Cost and Estimated Fair Value (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Due in one year or less, Amortized Cost	$ 53,286
Due after one year through five years, Amortized Cost	296,181
Due after five years through ten years, Amortized Cost	213,094
Due after ten years, Amortized Cost	702,642
Marketable equity securities, Amortized Cost	12,436
Amortized Cost	1,277,639	$ 1,072,340
Due in one year or less, Estimated Fair Value	53,330
Due after one year through five years, Estimated Fair Value	297,385
Due after five years through ten years, Estimated Fair Value	213,791
Due after ten years, Estimated Fair Value	680,880
Marketable equity securities, Estimated Fair Value	13,828
Total available for sale securities	$ 1,259,214	$ 1,066,334

Investment Securities - Summa69

Investment Securities - Summary of Amortized Cost and Estimated Fair Values of Securities Held to Maturity (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Schedule of Investments [Line Items]
Amortized Cost	$ 33,258	$ 39,099
Gross Unrealized Gains	592	887
Gross Unrealized Losses	2,672	3,667
Estimated Fair Value	31,178	36,319
U.S. Treasury Securities and Obligations of U.S. Government Corporations and Agencies [Member]
Schedule of Investments [Line Items]
Amortized Cost	5,295	10,425
Gross Unrealized Gains	570	860
Gross Unrealized Losses	0	0
Estimated Fair Value	5,865	11,285
State and Political Subdivisions [Member]
Schedule of Investments [Line Items]
Amortized Cost	8,598	9,321
Gross Unrealized Gains	17	21
Gross Unrealized Losses	0	253
Estimated Fair Value	8,615	9,089
Residential Mortgage-Backed Securities, Agency [Member]
Schedule of Investments [Line Items]
Amortized Cost	30	35
Gross Unrealized Gains	5	6
Gross Unrealized Losses	0	0
Estimated Fair Value	35	41
Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	19,315	19,298
Gross Unrealized Gains	0	0
Gross Unrealized Losses	2,672	3,414
Estimated Fair Value	16,643	15,884
Corporate Bonds [Member]
Schedule of Investments [Line Items]
Amortized Cost	20	20
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	$ 20	$ 20

Investment Securities - Summa70

Investment Securities - Summary of Gross Realized Gains and Losses on Calls and Sales of Held to Maturity Securities Included in Earnings (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Investments, Debt and Equity Securities [Abstract]
Gross realized gains	$ 0	$ 0	$ 9
Gross realized losses	$ 0	$ 0	$ 0

Investment Securities - Summa71

Investment Securities - Summary of Maturities of Debt Securities Held to Maturity by Amortized Cost and Estimated Fair Value (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Due in one year or less, Amortized Cost	$ 1,040
Due after one year through five years, Amortized Cost	8,268
Due after five years through ten years, Amortized Cost	3,585
Due after ten years, Amortized Cost	20,365
Amortized Cost	33,258	$ 39,099
Due in one year or less, Estimated Fair Value	1,041
Due after one year through five years, Estimated Fair Value	8,850
Due after five years through ten year, Estimated Fair Value	3,589
Due after ten years, Estimated Fair Value	17,698
Estimated Fair Value, Total	$ 31,178	$ 36,319

Investment Securities - Maturit

Investment Securities - Maturities and Weighted-Average Yields of Securities (Detail) $ in Thousands	Dec. 31, 2016USD ($)
Schedule of Held-to-maturity Securities [Line Items]
Securities matured Within 1 Year, Amount	$ 1,040
Securities matured After 1 But Within 5 Years, Amount	8,268
Securities matured After 5 But Within 10 Years, Amount	3,585
Securities matured After 10 Years, Amount	20,365
U.S. Treasury Securities and Obligations of U.S. Government Corporations and Agencies [Member]
Schedule of Held-to-maturity Securities [Line Items]
Securities matured Within 1 Year, Amount	$ 32,097
Weighted-average Within 1 Year, Yield	0.39%
Securities matured After 1 But Within 5 Years, Amount	$ 61,924
Weighted-average After 1 But Within 5 Years, Yield	2.04%
Securities matured After 5 But Within 10 Years, Amount	$ 6,521
Weighted-average After 5 But Within 10 Years, Yield	2.25%
Securities matured After 10 Years, Amount	$ 0
Weighted-average After 10 Years, Yield	0.00%
State and Political Subdivisions [Member]
Schedule of Held-to-maturity Securities [Line Items]
Securities matured Within 1 Year, Amount	$ 14,451
Weighted-average Within 1 Year, Yield	2.89%
Securities matured After 1 But Within 5 Years, Amount	$ 41,926
Weighted-average After 1 But Within 5 Years, Yield	3.24%
Securities matured After 5 But Within 10 Years, Amount	$ 34,096
Weighted-average After 5 But Within 10 Years, Yield	3.81%
Securities matured After 10 Years, Amount	$ 114,475
Weighted-average After 10 Years, Yield	3.94%
Residential Mortgage-Backed Securities, Agency [Member]
Schedule of Held-to-maturity Securities [Line Items]
Securities matured Within 1 Year, Amount	$ 68
Weighted-average Within 1 Year, Yield	5.44%
Securities matured After 1 But Within 5 Years, Amount	$ 5,043
Weighted-average After 1 But Within 5 Years, Yield	4.01%
Securities matured After 5 But Within 10 Years, Amount	$ 58,141
Weighted-average After 5 But Within 10 Years, Yield	2.72%
Securities matured After 10 Years, Amount	$ 521,986
Weighted-average After 10 Years, Yield	2.34%
Residential Mortgage-Backed Securities, Non-agency [Member]
Schedule of Held-to-maturity Securities [Line Items]
Securities matured Within 1 Year, Amount	$ 0
Weighted-average Within 1 Year, Yield	0.00%
Securities matured After 1 But Within 5 Years, Amount	$ 1,339
Weighted-average After 1 But Within 5 Years, Yield	5.00%
Securities matured After 5 But Within 10 Years, Amount	$ 0
Weighted-average After 5 But Within 10 Years, Yield	0.00%
Securities matured After 10 Years, Amount	$ 5,290
Weighted-average After 10 Years, Yield	5.83%
Commercial Mortgage-backed Agency [Member]
Schedule of Held-to-maturity Securities [Line Items]
Securities matured Within 1 Year, Amount	$ 9,051
Weighted-average Within 1 Year, Yield	0.95%
Securities matured After 1 But Within 5 Years, Amount	$ 188,624
Weighted-average After 1 But Within 5 Years, Yield	1.79%
Securities matured After 5 But Within 10 Years, Amount	$ 106,960
Weighted-average After 5 But Within 10 Years, Yield	2.63%
Securities matured After 10 Years, Amount	$ 0
Weighted-average After 10 Years, Yield	0.00%
Asset-Backed Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Securities matured Within 1 Year, Amount	$ 217
Weighted-average Within 1 Year, Yield	1.38%
Securities matured After 1 But Within 5 Years, Amount	$ 0
Weighted-average After 1 But Within 5 Years, Yield	0.00%
Securities matured After 5 But Within 10 Years, Amount	$ 0
Weighted-average After 5 But Within 10 Years, Yield	0.00%
Securities matured After 10 Years, Amount	$ 0
Weighted-average After 10 Years, Yield	0.00%
Trust Preferred Collateralized Debt Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Securities matured Within 1 Year, Amount	$ 0
Weighted-average Within 1 Year, Yield	0.00%
Securities matured After 1 But Within 5 Years, Amount	$ 0
Weighted-average After 1 But Within 5 Years, Yield	0.00%
Securities matured After 5 But Within 10 Years, Amount	$ 0
Weighted-average After 5 But Within 10 Years, Yield	0.00%
Securities matured After 10 Years, Amount	$ 48,558
Weighted-average After 10 Years, Yield	3.80%
Single Issue Trust Preferred Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Securities matured Within 1 Year, Amount	$ 0
Weighted-average Within 1 Year, Yield	0.00%
Securities matured After 1 But Within 5 Years, Amount	$ 0
Weighted-average After 1 But Within 5 Years, Yield	0.00%
Securities matured After 5 But Within 10 Years, Amount	$ 0
Weighted-average After 5 But Within 10 Years, Yield	0.00%
Securities matured After 10 Years, Amount	$ 32,678
Weighted-average After 10 Years, Yield	2.84%
Marketable Equity Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Securities matured Within 1 Year, Amount	$ 0
Weighted-average Within 1 Year, Yield	0.00%
Securities matured After 1 But Within 5 Years, Amount	$ 0
Weighted-average After 1 But Within 5 Years, Yield	0.00%
Securities matured After 5 But Within 10 Years, Amount	$ 0
Weighted-average After 5 But Within 10 Years, Yield	0.00%
Securities matured After 10 Years, Amount	$ 12,436
Weighted-average After 10 Years, Yield	0.64%
Corporate Bonds [Member]
Schedule of Held-to-maturity Securities [Line Items]
Securities matured Within 1 Year, Amount	$ 0
Weighted-average Within 1 Year, Yield	0.00%
Securities matured After 1 But Within 5 Years, Amount	$ 4,996
Weighted-average After 1 But Within 5 Years, Yield	1.98%
Securities matured After 5 But Within 10 Years, Amount	$ 10,000
Weighted-average After 5 But Within 10 Years, Yield	5.50%
Securities matured After 10 Years, Amount	$ 20
Weighted-average After 10 Years, Yield	0.00%

Investment Securities - Matur73

Investment Securities - Maturities and Weighted-Average Yields of Securities (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Amortized Cost and Fair Value Debt Securities [Abstract]
Tax on income before taxes at statutory federal rate, rate	35.00%	35.00%	35.00%

Loans - Major Classes of Loans

Loans - Major Classes of Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Commercial, financial, and agricultural
Total commercial, financial & agricultural	$ 6,088,775	$ 5,426,335
Residential real estate	2,403,437	2,268,685
Construction & land development	1,255,738	1,273,054
Consumer:
Bankcard	14,187	11,653
Other Consumer	594,582	419,225
Less: Unearned interest	(15,582)	(14,872)
Loans net of unearned income	10,341,137	9,384,080
Owner-Occupied [Member]
Commercial, financial, and agricultural
Total commercial, financial & agricultural	1,049,885	927,746
Nonowner-Occupied [Member]
Commercial, financial, and agricultural
Total commercial, financial & agricultural	3,425,453	2,896,367
Other Commercial [Member]
Commercial, financial, and agricultural
Total commercial, financial & agricultural	$ 1,613,437	$ 1,602,222

Loans - Additional Information

Loans - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Loans held for sale	$ 8,445,000	$ 10,681,000
Acquired impaired loans from merger	$ 10,356,719,000	9,398,952,000
Percentage of acquired impaired loans from merger on total gross loans	1.66%
Recorded investment in acquired impaired loans	$ 231,096,000	208,765,000
Loans-in-process	38,591,000	66,501,000
Overdrafts from deposit accounts	7,971,000	9,234,000
Additional amount of loan	393,273,000
Repayment of Loan	378,797,000
Directors and Officers [Member]
Related party loans	255,476,000	$ 241,000,000
Maximum [Member]
Percentage of acquired impaired loans from merger on total gross loans		1.58%
Loans Acquired with Deteriorated Credit Quality [Member]
Acquired impaired loans from merger	$ 171,596,000	$ 148,197,000

Loans - Activity for Accretable

Loans - Activity for Accretable Yield (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2016USD ($)
Loans [Abstract]
Accretable yield at the beginning of the period	$ 12,156
Accretion (including cash recoveries)	(11,457)
Additions for Bank of Georgetown acquisition	19,552
Net reclassifications to accretable from non-accretable	12,439
Disposals (including maturities, foreclosures, and charge-offs)	(3,525)
Accretable yield at the ending of the period	$ 29,165

Credit Quality - Additional Inf

Credit Quality - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)SecurityLoan
Receivables [Abstract]
Minimum days for discontinue of accrual interest on commercial and consumer loan	90 days
Maximum days for discontinue of accrual interest on commercial and consumer loan	120 days
Troubled debt restructuring	$ 21,152,000	$ 23,890,000
Restructured loans on nonaccrual status	11,106,000	11,949,000
Restructured loans modified by reduction in interest	2,667,000
Restructured loan and interest	6,513,000
Restructured loans modified by change in terms	11,972,000
Restructured loans modified by reduction in interest rate and change in terms	2,887,000	$ 3,565,000
Restructured loans modified by change in loan terms amount	$ 1,904,000
Number of loans restructured | SecurityLoan		0
Minimum number of days required for special mention	30 days
Maximum number of days required for special mention	89 days
Number of days required for substandard	90 days

Credit Quality - Schedule of Tr

Credit Quality - Schedule of Troubled Debt Restructurings, Segregated by Class of Loans (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2016USD ($)Contract	Dec. 31, 2015USD ($)Contract
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	9	4
Pre-Modification Outstanding Recorded Investment	$ 5,393	$ 3,611
Post-Modification Outstanding Recorded Investment	$ 4,791	$ 3,565
Construction & Land Development [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	0	0
Pre-Modification Outstanding Recorded Investment	$ 0	$ 0
Post-Modification Outstanding Recorded Investment	$ 0	$ 0
Commercial Real Estate [Member] | Owner-Occupied [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	1	0
Pre-Modification Outstanding Recorded Investment	$ 1,190	$ 0
Post-Modification Outstanding Recorded Investment	$ 1,178	$ 0
Commercial Real Estate [Member] | Nonowner-Occupied [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	0	1
Pre-Modification Outstanding Recorded Investment	$ 0	$ 669
Post-Modification Outstanding Recorded Investment	$ 0	$ 647
Other Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	7	3
Pre-Modification Outstanding Recorded Investment	$ 2,803	$ 2,942
Post-Modification Outstanding Recorded Investment	$ 2,213	$ 2,918
Residential Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	1	0
Pre-Modification Outstanding Recorded Investment	$ 1,400	$ 0
Post-Modification Outstanding Recorded Investment	$ 1,400	$ 0
Consumer [Member] | Bankcard [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	0	0
Pre-Modification Outstanding Recorded Investment	$ 0	$ 0
Post-Modification Outstanding Recorded Investment	$ 0	$ 0
Consumer [Member] | Other Consumer [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	0	0
Pre-Modification Outstanding Recorded Investment	$ 0	$ 0
Post-Modification Outstanding Recorded Investment	$ 0	$ 0

Credit Quality - Schedule of Ch

Credit Quality - Schedule of Charged-off Troubled Debt Restructurings on Financing Receivables (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2016USD ($)Contract
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	1
Recorded Investment | $	$ 37
Construction & Land Development [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	0
Recorded Investment | $	$ 0
Commercial Real Estate [Member] | Owner-Occupied [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	0
Recorded Investment | $	$ 0
Commercial Real Estate [Member] | Nonowner-Occupied [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	0
Recorded Investment | $	$ 0
Other Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	1
Recorded Investment | $	$ 37
Residential Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	0
Recorded Investment | $	$ 0
Consumer [Member] | Bankcard [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	0
Recorded Investment | $	$ 0
Consumer [Member] | Other Consumer [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	0
Recorded Investment | $	$ 0

Credit Quality - Schedule of Ag

Credit Quality - Schedule of Age Analysis of its Past Due Loans, Segregated by Class of Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, 30-89 Days Past Due	$ 74,633	$ 103,765
Loans, Total Past Due	177,850	218,531
Loans, Current & Other	10,178,869	9,180,421
Total Financing Receivables	10,356,719	9,398,952
Loans, Recorded Investment >90 Days & Accruing	8,586	11,628
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Total Past Due	103,217	114,766
Construction & Land Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, 30-89 Days Past Due	3,809	2,412
Loans, Total Past Due	11,588	17,828
Loans, Current & Other	1,244,150	1,255,226
Total Financing Receivables	1,255,738	1,273,054
Loans, Recorded Investment >90 Days & Accruing	33	1,347
Construction & Land Development [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Total Past Due	7,779	15,416
Commercial Real Estate [Member] | Owner-Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, 30-89 Days Past Due	5,850	8,639
Loans, Total Past Due	9,831	18,470
Loans, Current & Other	1,040,054	909,276
Total Financing Receivables	1,049,885	927,746
Loans, Recorded Investment >90 Days & Accruing	94	400
Commercial Real Estate [Member] | Owner-Occupied [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Total Past Due	3,981	9,831
Commercial Real Estate [Member] | Nonowner-Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, 30-89 Days Past Due	9,288	24,209
Loans, Total Past Due	30,135	50,335
Loans, Current & Other	3,395,318	2,846,032
Total Financing Receivables	3,425,453	2,896,367
Loans, Recorded Investment >90 Days & Accruing	172	552
Commercial Real Estate [Member] | Nonowner-Occupied [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Total Past Due	20,847	26,126
Other Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, 30-89 Days Past Due	15,273	14,888
Loans, Total Past Due	58,039	48,185
Loans, Current & Other	1,555,398	1,554,037
Total Financing Receivables	1,613,437	1,602,222
Loans, Recorded Investment >90 Days & Accruing	2,518	3,643
Other Commercial [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Total Past Due	42,766	33,297
Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, 30-89 Days Past Due	29,976	44,312
Loans, Total Past Due	55,967	72,644
Loans, Current & Other	2,347,470	2,196,041
Total Financing Receivables	2,403,437	2,268,685
Loans, Recorded Investment >90 Days & Accruing	4,216	4,294
Residential Real Estate [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Total Past Due	25,991	28,332
Consumer [Member] | Bankcard [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, 30-89 Days Past Due	422	223
Loans, Total Past Due	563	391
Loans, Current & Other	13,624	11,262
Total Financing Receivables	14,187	11,653
Loans, Recorded Investment >90 Days & Accruing	141	168
Consumer [Member] | Bankcard [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Total Past Due	141	168
Consumer [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, 30-89 Days Past Due	10,015	9,082
Loans, Total Past Due	11,727	10,678
Loans, Current & Other	582,855	408,547
Total Financing Receivables	594,582	419,225
Loans, Recorded Investment >90 Days & Accruing	1,412	1,224
Consumer [Member] | Other Consumer [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Total Past Due	$ 1,712	$ 1,596

Credit Quality - Schedule of 81

Credit Quality - Schedule of Age Analysis of its Past Due Loans, Segregated by Class of Loans (Parenthetical) (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment, Past Due [Line Items]
Acquired impaired loans from merger	$ 10,356,719	$ 9,398,952
Loans Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Acquired impaired loans from merger	171,596	148,197
Loans and Debt Securities Acquired with Deteriorated Credit Quality [Member] | Loans Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Acquired impaired loans from merger	$ 171,596	$ 148,197

Credit Quality - Schedule of No

Credit Quality - Schedule of Nonaccrual Loans, Segregated by Class of Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans on Nonaccrual Status	$ 94,631	$ 103,138
Construction & Land Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans on Nonaccrual Status	7,746	14,069
Commercial Real Estate [Member] | Owner-Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans on Nonaccrual Status	3,887	9,431
Commercial Real Estate [Member] | Nonowner-Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans on Nonaccrual Status	20,675	25,574
Other Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans on Nonaccrual Status	40,248	29,654
Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans on Nonaccrual Status	21,775	24,038
Consumer [Member] | Bankcard [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans on Nonaccrual Status	0	0
Consumer [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans on Nonaccrual Status	$ 300	$ 372

Credit Quality - Schedule of Cr

Credit Quality - Schedule of Credit Quality Indicators Information, by Class of Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	$ 10,356,719	$ 9,398,952
Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	2,403,437	2,268,685
Other Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	1,613,437	1,602,222
Bankcard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	14,187	11,653
Other Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	594,582	419,225
Owner-Occupied [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	1,049,885	927,746
Nonowner-Occupied [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	3,425,453	2,896,367
Construction & Land Development [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	1,255,738	1,273,054
Pass [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	2,348,017	2,195,420
Pass [Member] | Other Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	1,463,797	1,436,670
Pass [Member] | Bankcard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	13,624	11,262
Pass [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	582,704	408,271
Pass [Member] | Owner-Occupied [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	963,503	835,082
Pass [Member] | Nonowner-Occupied [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	3,284,497	2,710,504
Pass [Member] | Construction & Land Development [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	1,126,742	1,095,238
Special Mention [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	18,240	13,494
Special Mention [Member] | Other Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	26,537	26,148
Special Mention [Member] | Bankcard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	422	223
Special Mention [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	10,132	9,188
Special Mention [Member] | Owner-Occupied [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	20,490	20,391
Special Mention [Member] | Nonowner-Occupied [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	36,462	32,249
Special Mention [Member] | Construction & Land Development [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	52,327	59,100
Substandard [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	36,995	57,981
Substandard [Member] | Other Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	122,893	136,585
Substandard [Member] | Bankcard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	141	168
Substandard [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	1,746	1,766
Substandard [Member] | Owner-Occupied [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	65,892	72,273
Substandard [Member] | Nonowner-Occupied [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	104,494	153,614
Substandard [Member] | Construction & Land Development [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	76,669	118,716
Doubtful [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	185	1,790
Doubtful [Member] | Other Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	210	2,819
Doubtful [Member] | Bankcard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	0	0
Doubtful [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	0	0
Doubtful [Member] | Owner-Occupied [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	0	0
Doubtful [Member] | Nonowner-Occupied [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	0	0
Doubtful [Member] | Construction & Land Development [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	$ 0	$ 0

Credit Quality - Schedule of Im

Credit Quality - Schedule of Impaired Loans Information by Class of Loans (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Construction & Land Development [Member]
Financing Receivable, Impaired [Line Items]
Impaired Loans, Recorded Investment, With no related allowance recorded	$ 19,863	$ 28,245
Impaired Loans, Unpaid Principal Balance, With no related allowance recorded	21,746	29,953
Impaired Loans, Recorded Investment, With an allowance recorded	4,940	14,132
Impaired Loans, Unpaid Principal Balance, With an allowance recorded	7,899	20,135
Impaired Loans, Related Allowance	3,206	4,789
Impaired Loans, Recorded Investment	24,803	42,377
Impaired Loans, Unpaid Principal Balance	29,645	50,088
Impaired Loans, Related Allowance	3,206	4,789
Impaired Loans, Average Recorded Investment, With no related allowance recorded	24,902	33,167
Impaired Loans, Interest Income Recognized, With no related allowance recorded	133	199
Impaired Loans, Average Recorded Investment, With an allowance recorded	8,994	12,196
Impaired Loans, Interest Income Recognized, With an allowance recorded	83	252
Impaired Loans, Average Recorded Investment	33,896	45,363
Impaired Loans, Interest Income Recognized	216	451
Bankcard [Member]
Financing Receivable, Impaired [Line Items]
Impaired Loans, Average Recorded Investment, With no related allowance recorded	0	0
Impaired Loans, Interest Income Recognized, With no related allowance recorded	0	0
Other Consumer [Member]
Financing Receivable, Impaired [Line Items]
Impaired Loans, Average Recorded Investment, With no related allowance recorded	33	35
Impaired Loans, Interest Income Recognized, With no related allowance recorded	0	0
Commercial Real Estate [Member] | Owner-Occupied [Member]
Financing Receivable, Impaired [Line Items]
Impaired Loans, Recorded Investment, With no related allowance recorded	46,575	36,615
Impaired Loans, Unpaid Principal Balance, With no related allowance recorded	47,108	36,828
Impaired Loans, Recorded Investment, With an allowance recorded	1,787	4,555
Impaired Loans, Unpaid Principal Balance, With an allowance recorded	2,082	4,555
Impaired Loans, Related Allowance	815	1,253
Impaired Loans, Recorded Investment	48,362	41,170
Impaired Loans, Unpaid Principal Balance	49,190	41,383
Impaired Loans, Related Allowance	815	1,253
Impaired Loans, Average Recorded Investment, With no related allowance recorded	36,800	41,336
Impaired Loans, Interest Income Recognized, With no related allowance recorded	1,038	264
Impaired Loans, Average Recorded Investment, With an allowance recorded	3,138	4,629
Impaired Loans, Interest Income Recognized, With an allowance recorded	97	122
Impaired Loans, Average Recorded Investment	39,938	45,965
Impaired Loans, Interest Income Recognized	1,135	386
Commercial Real Estate [Member] | Nonowner-Occupied [Member]
Financing Receivable, Impaired [Line Items]
Impaired Loans, Recorded Investment, With no related allowance recorded	92,654	69,053
Impaired Loans, Unpaid Principal Balance, With no related allowance recorded	93,104	69,517
Impaired Loans, Recorded Investment, With an allowance recorded	17,938	7,890
Impaired Loans, Unpaid Principal Balance, With an allowance recorded	17,938	7,890
Impaired Loans, Related Allowance	2,524	1,362
Impaired Loans, Recorded Investment	110,592	76,943
Impaired Loans, Unpaid Principal Balance	111,042	77,407
Impaired Loans, Related Allowance	2,524	1,362
Impaired Loans, Average Recorded Investment, With no related allowance recorded	75,848	68,727
Impaired Loans, Interest Income Recognized, With no related allowance recorded	1,108	1,139
Impaired Loans, Average Recorded Investment, With an allowance recorded	11,920	6,954
Impaired Loans, Interest Income Recognized, With an allowance recorded	564	357
Impaired Loans, Average Recorded Investment	87,768	75,681
Impaired Loans, Interest Income Recognized	1,672	1,496
Other Commercial [Member]
Financing Receivable, Impaired [Line Items]
Impaired Loans, Recorded Investment, With no related allowance recorded	46,064	30,433
Impaired Loans, Unpaid Principal Balance, With no related allowance recorded	48,308	32,158
Impaired Loans, Recorded Investment, With an allowance recorded	43,774	29,486
Impaired Loans, Unpaid Principal Balance, With an allowance recorded	46,188	33,127
Impaired Loans, Related Allowance	13,441	18,269
Impaired Loans, Recorded Investment	89,838	59,919
Impaired Loans, Unpaid Principal Balance	94,496	65,285
Impaired Loans, Related Allowance	13,441	18,269
Impaired Loans, Average Recorded Investment, With no related allowance recorded	39,776	33,510
Impaired Loans, Interest Income Recognized, With no related allowance recorded	1,540	463
Impaired Loans, Average Recorded Investment, With an allowance recorded	36,511	20,885
Impaired Loans, Interest Income Recognized, With an allowance recorded	1,615	580
Impaired Loans, Average Recorded Investment	76,287	54,395
Impaired Loans, Interest Income Recognized	3,155	1,043
Residential Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired Loans, Recorded Investment, With no related allowance recorded	22,747	21,431
Impaired Loans, Unpaid Principal Balance, With no related allowance recorded	24,404	22,329
Impaired Loans, Recorded Investment, With an allowance recorded	12,066	13,305
Impaired Loans, Unpaid Principal Balance, With an allowance recorded	12,801	14,625
Impaired Loans, Related Allowance	3,431	2,118
Impaired Loans, Recorded Investment	34,813	34,736
Impaired Loans, Unpaid Principal Balance	37,205	36,954
Impaired Loans, Related Allowance	3,431	2,118
Impaired Loans, Average Recorded Investment, With no related allowance recorded	25,964	27,224
Impaired Loans, Interest Income Recognized, With no related allowance recorded	538	234
Impaired Loans, Average Recorded Investment, With an allowance recorded	9,585	9,314
Impaired Loans, Interest Income Recognized, With an allowance recorded	342	41
Impaired Loans, Average Recorded Investment	35,549	36,538
Impaired Loans, Interest Income Recognized	880	275
Consumer [Member] | Bankcard [Member]
Financing Receivable, Impaired [Line Items]
Impaired Loans, Recorded Investment, With no related allowance recorded	0	0
Impaired Loans, Unpaid Principal Balance, With no related allowance recorded	0	0
Impaired Loans, Recorded Investment, With an allowance recorded	0	0
Impaired Loans, Unpaid Principal Balance, With an allowance recorded	0	0
Impaired Loans, Related Allowance	0	0
Impaired Loans, Recorded Investment	0	0
Impaired Loans, Unpaid Principal Balance	0	0
Impaired Loans, Related Allowance	0	0
Impaired Loans, Average Recorded Investment, With an allowance recorded	0	0
Impaired Loans, Interest Income Recognized, With an allowance recorded	0	0
Impaired Loans, Average Recorded Investment	0	0
Impaired Loans, Interest Income Recognized	0	0
Consumer [Member] | Other Consumer [Member]
Financing Receivable, Impaired [Line Items]
Impaired Loans, Recorded Investment, With no related allowance recorded	36	32
Impaired Loans, Unpaid Principal Balance, With no related allowance recorded	36	32
Impaired Loans, Recorded Investment, With an allowance recorded	0	0
Impaired Loans, Unpaid Principal Balance, With an allowance recorded	0	0
Impaired Loans, Related Allowance	0	0
Impaired Loans, Recorded Investment	36	32
Impaired Loans, Unpaid Principal Balance	36	32
Impaired Loans, Related Allowance	0	0
Impaired Loans, Average Recorded Investment, With an allowance recorded	0	0
Impaired Loans, Interest Income Recognized, With an allowance recorded	0	0
Impaired Loans, Average Recorded Investment	33	35
Impaired Loans, Interest Income Recognized	$ 0	$ 0

Allowance for Credit Losses - A

Allowance for Credit Losses - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Allowance for Credit Losses [Line Items]
Specific loss allocations are calculated for commercial loans in excess	$ 500,000
Number of days for collecting principal or interest on consumer loans	90 days
Minimum collection period for home equity loan or high loan to value loan	180 days
Retail credits amount deemed unrecoverable charged-off period	60 days
Retail credits charged off period after discovery of the fraud	90 days
Provision for loan losses related to loans acquired	$ 1,676,000	$ 5,321,000	$ 1,915,000
Reserve for lending-related commitments	$ 1,044,000	$ 936,000	$ 1,518,000
Closed-End Retail Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Number of days delinquent from contractual due date	120 days
Open-End Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Number of days delinquent from contractual due date	180 days

Allowance for Credit Losses - S

Allowance for Credit Losses - Schedule of Allowance for Loan Losses and Carrying Amount of Loans (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses Beginning balance				$ 75,726				$ 75,529	$ 75,726	$ 75,529
Charge-offs									36,180	25,499
Recoveries									8,716	3,122
Provision	$ 5,819	$ 6,988	$ 7,667	4,035	$ 6,322	$ 5,182	$ 5,716	5,354	24,509	22,574	$ 21,937
Allowance for Loan Losses Ending balance	72,771				75,726				72,771	75,726	75,529
Allowance for Loan Losses, individually evaluated for impairment	23,417				27,792				23,417	27,792
Allowance for Loan Losses, collectively evaluated for impairment	49,354				47,934				49,354	47,934
Allowance for Loan Losses	72,771				75,726				72,771	75,726	75,529	$ 74,198
Financing receivables	10,356,719				9,398,952				10,356,719	9,398,952
Financing receivables, individually evaluated for impairment	124,820				107,725				124,820	107,725
Financing receivables, collectively evaluated for impairment	10,060,303				9,143,030				10,060,303	9,143,030
Loans Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses	0				0				0	0
Financing receivables	171,596				148,197				171,596	148,197
Construction & Land Development [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses Beginning balance				18,205				19,402	18,205	19,402
Charge-offs									2,659	862
Recoveries									433	511
Provision									(5,373)	(846)
Allowance for Loan Losses Ending balance	10,606				18,205				10,606	18,205	19,402
Allowance for Loan Losses, individually evaluated for impairment	3,206				4,789				3,206	4,789
Allowance for Loan Losses, collectively evaluated for impairment	7,400				13,416				7,400	13,416
Financing receivables	1,255,738				1,273,054				1,255,738	1,273,054
Financing receivables, individually evaluated for impairment	8,152				15,779				8,152	15,779
Financing receivables, collectively evaluated for impairment	1,221,006				1,221,760				1,221,006	1,221,760
Construction & Land Development [Member] | Loans Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses	0				0				0	0
Financing receivables	26,580				35,515				26,580	35,515
Allowance for Estimated Imprecision [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses Beginning balance				104				70	104	70
Charge-offs									0	0
Recoveries									0	0
Provision									243	34
Allowance for Loan Losses Ending balance	347				104				347	104	70
Allowance for Loan Losses, individually evaluated for impairment	0				0				0	0
Allowance for Loan Losses, collectively evaluated for impairment	347				104				347	104
Financing receivables	0				0				0	0
Financing receivables, individually evaluated for impairment	0				0				0	0
Financing receivables, collectively evaluated for impairment	0				0				0	0
Allowance for Estimated Imprecision [Member] | Loans Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses	0				0				0	0
Financing receivables	0				0				0	0
Commercial Real Estate [Member] | Owner-Occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses Beginning balance				3,637				4,041	3,637	4,041
Charge-offs									5,281	4,755
Recoveries									3,071	829
Provision									3,846	3,522
Allowance for Loan Losses Ending balance	5,273				3,637				5,273	3,637	4,041
Allowance for Loan Losses, individually evaluated for impairment	815				1,253				815	1,253
Allowance for Loan Losses, collectively evaluated for impairment	4,458				2,384				4,458	2,384
Financing receivables	1,049,885				927,746				1,049,885	927,746
Financing receivables, individually evaluated for impairment	18,976				12,670				18,976	12,670
Financing receivables, collectively evaluated for impairment	1,005,999				888,802				1,005,999	888,802
Commercial Real Estate [Member] | Owner-Occupied [Member] | Loans Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses	0				0				0	0
Financing receivables	24,910				26,274				24,910	26,274
Commercial Real Estate [Member] | Nonowner-Occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses Beginning balance				5,309				8,167	5,309	8,167
Charge-offs									419	1,120
Recoveries									675	74
Provision									1,318	(1,812)
Allowance for Loan Losses Ending balance	6,883				5,309				6,883	5,309	8,167
Allowance for Loan Losses, individually evaluated for impairment	2,524				1,362				2,524	1,362
Allowance for Loan Losses, collectively evaluated for impairment	4,359				3,947				4,359	3,947
Financing receivables	3,425,453				2,896,367				3,425,453	2,896,367
Financing receivables, individually evaluated for impairment	26,835				26,152				26,835	26,152
Financing receivables, collectively evaluated for impairment	3,323,117				2,817,748				3,323,117	2,817,748
Commercial Real Estate [Member] | Nonowner-Occupied [Member] | Loans Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses	0				0				0	0
Financing receivables	75,501				52,467				75,501	52,467
Other Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses Beginning balance				31,328				26,931	31,328	26,931
Charge-offs									20,430	10,042
Recoveries									3,452	714
Provision									18,737	13,725
Allowance for Loan Losses Ending balance	33,087				31,328				33,087	31,328	26,931
Allowance for Loan Losses, individually evaluated for impairment	13,441				18,269				13,441	18,269
Allowance for Loan Losses, collectively evaluated for impairment	19,646				13,059				19,646	13,059
Financing receivables	1,613,437				1,602,222				1,613,437	1,602,222
Financing receivables, individually evaluated for impairment	56,091				35,342				56,091	35,342
Financing receivables, collectively evaluated for impairment	1,527,479				1,546,018				1,527,479	1,546,018
Other Commercial [Member] | Loans Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses	0				0				0	0
Financing receivables	29,867				20,862				29,867	20,862
Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses Beginning balance				15,148				13,835	15,148	13,835
Charge-offs									4,597	6,411
Recoveries									639	495
Provision									2,580	7,229
Allowance for Loan Losses Ending balance	13,770				15,148				13,770	15,148	13,835
Allowance for Loan Losses, individually evaluated for impairment	3,431				2,119				3,431	2,119
Allowance for Loan Losses, collectively evaluated for impairment	10,339				13,029				10,339	13,029
Financing receivables	2,403,437				2,268,685				2,403,437	2,268,685
Financing receivables, individually evaluated for impairment	14,766				17,782				14,766	17,782
Financing receivables, collectively evaluated for impairment	2,373,969				2,237,865				2,373,969	2,237,865
Residential Real Estate [Member] | Loans Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses	0				0				0	0
Financing receivables	14,702				13,038				14,702	13,038
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses Beginning balance				$ 1,995				$ 3,083	1,995	3,083
Charge-offs									2,794	2,309
Recoveries									446	499
Provision									3,158	722
Allowance for Loan Losses Ending balance	2,805				1,995				2,805	1,995	$ 3,083
Allowance for Loan Losses, individually evaluated for impairment	0				0				0	0
Allowance for Loan Losses, collectively evaluated for impairment	2,805				1,995				2,805	1,995
Financing receivables	608,769				430,878				608,769	430,878
Financing receivables, individually evaluated for impairment	0				0				0	0
Financing receivables, collectively evaluated for impairment	608,733				430,837				608,733	430,837
Consumer [Member] | Loans Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses	0				0				0	0
Financing receivables	$ 36				$ 41				$ 36	$ 41

Allowance for Credit Losses - P

Allowance for Credit Losses - Progression of Allowance for Credit Losses Including Allowance for Loan Losses and Reserve for Lending-Related Commitments (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Receivables [Abstract]
Balance of allowance for loan losses at beginning of period				$ 75,726				$ 75,529	$ 75,726	$ 75,529	$ 74,198
Provision for loan losses	$ 5,819	$ 6,988	$ 7,667	$ 4,035	$ 6,322	$ 5,182	$ 5,716	$ 5,354	24,509	22,574	21,937
Financing receivable allowance and provisions for credit losses									100,235	98,103	96,135
Loans charged off									36,180	25,499	25,241
Less recoveries									(8,716)	(3,122)	(4,635)
Net charge-offs									27,464	22,377	20,606
Balance of allowance for loan losses at end of period	72,771				75,726				72,771	75,726	75,529
Reserve for lending-related commitments	1,044				936				1,044	936	1,518
Balance of allowance for credit losses at end of period	$ 73,815				$ 76,662				$ 73,815	$ 76,662	$ 77,047

Bank Premises and Equipment a88

Bank Premises and Equipment and Leases - Bank Premises and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Bank premises and equipment, Gross	$ 212,332	$ 199,322
Less allowance for depreciation and amortization	136,423	126,233
Bank premises and equipment, Net	75,909	73,089
Land [Member]
Property, Plant and Equipment [Line Items]
Bank premises and equipment, Gross	24,238	24,497
Buildings and Improvements [Member]
Property, Plant and Equipment [Line Items]
Bank premises and equipment, Gross	89,302	87,717
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Bank premises and equipment, Gross	33,194	26,875
Furniture, Fixtures and Equipment [Member]
Property, Plant and Equipment [Line Items]
Bank premises and equipment, Gross	$ 65,598	$ 60,233

Bank Premises and Equipment a89

Bank Premises and Equipment and Leases - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 7,889,000	$ 8,385,000	$ 9,351,000
Amortization expense	136,000	136,000	136,000
Rent expense related to properties owned by related parties	$ 14,661,000	$ 12,528,000	$ 12,610,000

Bank Premises and Equipment a90

Bank Premises and Equipment and Leases - Future Minimum Lease Payments (Detail) $ in Thousands	Dec. 31, 2016USD ($)
Property Plant and Equipment Useful Life and Values [Abstract]
2,017	$ 12,661
2,018	11,653
2,019	9,756
2,020	7,427
2,021	6,059
Thereafter	15,380
Total minimum lease payments	$ 62,936

Goodwill and Other Intangible91

Goodwill and Other Intangibles - Summary of Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Goodwill not subject to amortization	$ 863,767	$ 710,252
Core Deposit Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	69,635	60,577
Accumulated Amortization	(46,681)	(42,737)
Net Carrying Amount	$ 22,954	$ 17,840

Goodwill and Other Intangible92

Goodwill and Other Intangibles - Reconciliation of Goodwill (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2016USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill, Beginning Balance	$ 710,252
Reclassification to goodwill	670
Preliminary addition to goodwill from Bank of Georgetown acquisition	152,845
Goodwill, Ending Balance	$ 863,767

Goodwill and Other Intangible93

Goodwill and Other Intangibles - Schedule of Anticipated Amortization Expense (Detail) $ in Thousands	Dec. 31, 2015USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
2,017	$ 4,190
2,018	3,707
2,019	3,450
2,020	3,252
2021 and thereafter	$ 8,355

Deposits - Book Value of Deposi

Deposits - Book Value of Deposits (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deposits [Abstract]
Demand deposits	$ 3,171,841	$ 2,699,958
Interest-bearing checking	1,778,156	1,683,316
Regular savings	721,224	692,079
Money market accounts	3,151,896	2,368,063
Time deposits under $100,000	693,005	794,428
Time deposits over $100,000	1,280,745	1,103,683
Total deposits	$ 10,796,867	$ 9,341,527

Deposits - Additional Informati

Deposits - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Deposits [Line Items]
Time deposits over $250,000	$ 357,468,000	$ 386,484,000
Interest paid	44,609,000	39,835,000	$ 42,012,000
Deposits	10,796,867,000	9,341,527,000
Subsidiaries [Member]
Deposits [Line Items]
Deposits	92,310,000	174,790,000
Deposits [Member]
Deposits [Line Items]
Interest paid	$ 29,048,000	$ 28,447,000	$ 26,925,000

Short-Term Borrowings -Short-Te

Short-Term Borrowings -Short-Term Borrowings and the Related Weighted-Average Interest Rates (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Short-term Debt [Line Items]
Short-term borrowings	$ 209,551	$ 313,028
Federal Funds Purchased [Member]
Short-term Debt [Line Items]
Weighted-Average Rate	0.65%	0.25%	0.20%
Short-term borrowings	$ 22,235	$ 22,230	$ 53,840
Securities Sold Under Agreements to Repurchase [Member]
Short-term Debt [Line Items]
Weighted-Average Rate	0.25%	0.15%	0.15%
Short-term borrowings	$ 187,316	$ 290,798	$ 381,812

Short-Term Borrowings -Short-97

Short-Term Borrowings -Short-Term Borrowings and the Related Weighted-Average Interest Rates (Parenthetical) (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Short-term Debt [Line Items]
Long-term borrowings	$ 0
Virginia Commerce Merger [Member]
Short-term Debt [Line Items]
Long-term borrowings	$ 50,000,000	$ 50,863,000
Acquisition accounting adjustment to fair value, interest rate	4.37%	4.37%
Acquisition accounting adjustment to fair value, maturity period	2018-05	2018-05

Short-Term Borrowings - Additio

Short-Term Borrowings - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Short-term Debt [Line Items]
Unused lines of credit	$ 264,000,000
Interest paid	44,609,000	$ 39,835,000	$ 42,012,000
Short-Term Borrowings [Member]
Short-term Debt [Line Items]
Interest paid	1,587,000	$ 835,000	$ 1,133,000
Unrelated Financial Institution [Member]
Short-term Debt [Line Items]
Unused lines of credit	$ 20,000,000
Renewal period of line of credit	360 days
Amount of outstanding balance under line of credit	$ 0

Short-Term Borrowings - Funds P

Short-Term Borrowings - Funds Purchased and Securities Sold Under Agreements to Repurchase and Weighted-Average Interest Rates (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Short-term Debt [Line Items]
Short-term borrowings	$ 209,551	$ 313,028
Federal Funds Purchased [Member]
Short-term Debt [Line Items]
Short-term borrowings	$ 22,235	$ 22,230	$ 53,840
Weighted-average interest rate at year-end	0.65%	0.25%	0.20%
Maximum amount outstanding at any month's end	$ 32,200	$ 52,000	$ 53,840
Average amount outstanding during the year	$ 22,717	$ 38,526	$ 24,037
Weighted-average interest rate during the year	0.32%	0.21%	0.20%
Securities Sold Under Agreements to Repurchase [Member]
Short-term Debt [Line Items]
Short-term borrowings	$ 187,316	$ 290,798	$ 381,812
Weighted-average interest rate at year-end	0.25%	0.15%	0.15%
Maximum amount outstanding at any month's end	$ 353,833	$ 379,818	$ 527,904
Average amount outstanding during the year	$ 298,494	$ 283,011	$ 357,083
Weighted-average interest rate during the year	0.17%	0.10%	0.12%

Long-Term Borrowings - Addition

Long-Term Borrowings - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2016USD ($)Trust	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)
Debt Instrument [Line Items]
Unused borrowing amount	$ 2,803,186,000
FHLB advances	897,707,000	$ 850,880,000
Overnight funds	0	110,000,000
Long-term borrowings	$ 0
Number of statutory business trusts | Trust	13
Outstanding balances of debentures	$ 224,319,000	223,506,000
Maximum time to defer payment of interest on subordinate debt	5 years
Trust Preferred Securities limit percentage	25.00%
Interest paid	$ 44,609,000	39,835,000	$ 42,012,000
Virginia Commerce Merger [Member]
Debt Instrument [Line Items]
Long-term borrowings	$ 50,000,000	$ 50,863,000
Acquisition accounting adjustment to fair value, interest rate	4.37%	4.37%
Acquisition accounting adjustment to fair value, maturity period	2018-05	2018-05
Capital Securities [Member]
Debt Instrument [Line Items]
Number of statutory business trusts | Trust	13
Federal Home Loan Bank Borrowings [Member]
Debt Instrument [Line Items]
Carrying value of loans pledged as collateral for FHLB advances	$ 4,447,061,000
Long-Term Borrowings [Member]
Debt Instrument [Line Items]
Interest paid	$ 13,974,000	$ 10,553,000	$ 13,954,000

Long-Term Borrowings - FHLB Adv

Long-Term Borrowings - FHLB Advances and Related Weighted Average Interest Rates (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Debt Disclosure [Abstract]
FHLB advances, Amount	$ 897,707	$ 850,880
FHLB advances, Weighted-Average Contractual Rate	0.72%	0.46%
FHLB advances, Weighted-Average Effective Rate	0.72%	0.46%

Long -Term Borrowings - Informa

Long -Term Borrowings - Information Related to Statutory Trusts (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2016USD ($)
Century Trust [Member]
Variable Interest Entity [Line Items]
Issuance Date	Mar. 23, 2000
Amount of Capital Securities Issued	$ 8,800
Interest Rate	10.875% Fixed
Maturity Date	Mar. 8, 2030
United Statutory Trust III [Member]
Variable Interest Entity [Line Items]
Issuance Date	Dec. 17, 2003
Amount of Capital Securities Issued	$ 20,000
Interest Rate	3-month LIBOR + 2.85%
Maturity Date	Dec. 17, 2033
United Statutory Trust IV [Member]
Variable Interest Entity [Line Items]
Issuance Date	Dec. 19, 2003
Amount of Capital Securities Issued	$ 25,000
Interest Rate	3-month LIBOR + 2.85%
Maturity Date	Jan. 23, 2034
United Statutory Trust V [Member]
Variable Interest Entity [Line Items]
Issuance Date	Jul. 12, 2007
Amount of Capital Securities Issued	$ 50,000
Interest Rate	3-month LIBOR + 1.55%
Maturity Date	Oct. 1, 2037
United Statutory Trust VI [Member]
Variable Interest Entity [Line Items]
Issuance Date	Sep. 20, 2007
Amount of Capital Securities Issued	$ 30,000
Interest Rate	3-month LIBOR + 1.30%
Maturity Date	Dec. 15, 2037
Premier Statutory Trust II [Member]
Variable Interest Entity [Line Items]
Issuance Date	Sep. 25, 2003
Amount of Capital Securities Issued	$ 6,000
Interest Rate	3-month LIBOR + 3.10%
Maturity Date	Oct. 8, 2033
Premier Statutory Trust III [Member]
Variable Interest Entity [Line Items]
Issuance Date	May 16, 2005
Amount of Capital Securities Issued	$ 8,000
Interest Rate	3-month LIBOR + 1.74%
Maturity Date	Jun. 15, 2035
Premier Statutory Trust IV [Member]
Variable Interest Entity [Line Items]
Issuance Date	Jun. 20, 2006
Amount of Capital Securities Issued	$ 14,000
Interest Rate	3-month LIBOR + 1.55%
Maturity Date	Sep. 23, 2036
Premier Statutory Trust V [Member]
Variable Interest Entity [Line Items]
Issuance Date	Dec. 14, 2006
Amount of Capital Securities Issued	$ 10,000
Interest Rate	3-month LIBOR + 1.61%
Maturity Date	Mar. 1, 2037
Centra Statutory Trust I [Member]
Variable Interest Entity [Line Items]
Issuance Date	Sep. 20, 2004
Amount of Capital Securities Issued	$ 10,000
Interest Rate	3-month LIBOR + 2.29%
Maturity Date	Sep. 20, 2034
Centra Statutory Trust II [Member]
Variable Interest Entity [Line Items]
Issuance Date	Jun. 15, 2006
Amount of Capital Securities Issued	$ 10,000
Interest Rate	3-month LIBOR + 1.65%
Maturity Date	Jul. 7, 2036
Virginia Commerce Trust II [Member]
Variable Interest Entity [Line Items]
Issuance Date	Dec. 19, 2002
Amount of Capital Securities Issued	$ 15,000
Interest Rate	6-month LIBOR + 3.30%
Maturity Date	Dec. 19, 2032
Virginia Commerce Trust III [Member]
Variable Interest Entity [Line Items]
Issuance Date	Dec. 20, 2005
Amount of Capital Securities Issued	$ 25,000
Interest Rate	3-month LIBOR + 1.42%
Maturity Date	Feb. 23, 2036

Long -Term Borrowings - Debentu

Long -Term Borrowings - Debentures and Related Weighted Average Interest Rates (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Amount	$ 224,319	$ 223,506
Century Trust [Member]
Debt Instrument [Line Items]
Amount	$ 8,800	$ 8,800
Weighted-Average Rate	10.88%	10.88%
United Statutory Trust III [Member]
Debt Instrument [Line Items]
Amount	$ 20,619	$ 20,619
Weighted-Average Rate	3.84%	3.38%
United Statutory Trust IV [Member]
Debt Instrument [Line Items]
Amount	$ 25,774	$ 25,774
Weighted-Average Rate	3.74%	3.17%
United Statutory Trust V [Member]
Debt Instrument [Line Items]
Amount	$ 51,547	$ 51,547
Weighted-Average Rate	2.40%	1.88%
United Statutory Trust VI [Member]
Debt Instrument [Line Items]
Amount	$ 30,928	$ 30,928
Weighted-Average Rate	2.26%	1.81%
Premier Statutory Trust II [Member]
Debt Instrument [Line Items]
Amount	$ 6,186	$ 6,186
Weighted-Average Rate	3.98%	3.42%
Premier Statutory Trust III [Member]
Debt Instrument [Line Items]
Amount	$ 8,248	$ 8,248
Weighted-Average Rate	2.70%	2.25%
Premier Statutory Trust IV [Member]
Debt Instrument [Line Items]
Amount	$ 14,433	$ 14,433
Weighted-Average Rate	2.55%	2.14%
Premier Statutory Trust V [Member]
Debt Instrument [Line Items]
Amount	$ 10,310	$ 10,310
Weighted-Average Rate	2.54%	2.02%
Centra Statutory Trust I [Member]
Debt Instrument [Line Items]
Amount	$ 10,000	$ 9,972
Weighted-Average Rate	3.29%	2.86%
Centra Statutory Trust II [Member]
Debt Instrument [Line Items]
Amount	$ 10,000	$ 9,972
Weighted-Average Rate	2.53%	1.97%
Virginia Commerce Trust II [Member]
Debt Instrument [Line Items]
Amount	$ 11,784	$ 11,554
Weighted-Average Rate	4.62%	4.13%
Virginia Commerce Trust III [Member]
Debt Instrument [Line Items]
Amount	$ 15,690	$ 15,163
Weighted-Average Rate	2.34%	1.80%

Long -Term Borrowings - Schedul

Long -Term Borrowings - Schedule of Maturities of Long-term Borrowings (Detail) $ in Thousands	Dec. 31, 2016USD ($)
Debt Disclosure [Abstract]
2,017	$ 825,606
2,018	59,628
2,019	34,243
2,020	0
2021 and thereafter	252,549
Total	$ 1,172,026

Other Expense - Other Expense (

Other Expense - Other Expense (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Other Income and Expenses [Abstract]
Legal, consulting & other professional services	$ 9,763,000	$ 9,310,000	$ 9,620,000
Franchise & other taxes not on income	7,778,000	7,055,000	7,513,000
Automated Teller Machine (ATM) expenses	$ 7,365,000	$ 7,107,000	$ 6,626,000

Income Taxes - Income Tax Provi

Income Taxes - Income Tax Provisions Included in the Consolidated Statements of Income (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current (benefit) expense:
Federal									$ 63,169	$ 58,373	$ 51,001
State									5,154	5,428	3,900
Deferred expense:
Federal and State									7,252	1,729	10,097
Total income taxes	$ 22,472	$ 18,846	$ 16,378	$ 17,879	$ 16,864	$ 16,217	$ 17,145	$ 15,304	$ 75,575	$ 65,530	$ 64,998

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Income Tax Expense to the Amount Computed by Applying the Statutory Federal Income Tax Rate (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Tax on income before taxes at statutory federal rate									$ 77,930	$ 71,222	$ 68,210
Plus: State income taxes net of federal tax benefits									4,084	3,516	2,523
Income tax before adjustments									82,014	74,738	70,733
Tax-exempt interest income									(3,919)	(4,158)	(4,048)
Historic tax credit									0	(1,262)	0
Other items-net									(2,520)	(3,788)	(1,687)
Total income taxes	$ 22,472	$ 18,846	$ 16,378	$ 17,879	$ 16,864	$ 16,217	$ 17,145	$ 15,304	$ 75,575	$ 65,530	$ 64,998
Tax on income before taxes at statutory federal rate, rate									35.00%	35.00%	35.00%
Plus: State income taxes net of federal tax benefits, rate									1.80%	1.70%	1.30%
Income tax before adjustments, rate									36.80%	36.70%	36.30%
Increase (decrease) resulting from:
Tax-exempt interest income, rate									(1.80%)	(2.00%)	(2.10%)
Historic tax credit, rate									(0.00%)	(0.60%)	(0.00%)
Other items-net, rate									(1.10%)	(1.90%)	(0.80%)
Income taxes, rate									33.90%	32.20%	33.40%

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Taxes [Line Items]
Federal income tax expense applicable to sales and calls of securities	$ 114,000	$ 73,000	$ 1,178,000
Income taxes paid	61,905,000	52,319,000	60,431,000
Franchise & other taxes not on income	7,778,000	7,055,000	7,513,000
Valuation allowance recorded	$ 0	0
Estimate of unrecognized tax benefits, reasonable possible	United cannot reasonably estimate the amount of tax benefits, if any, it may recognize over the next 12 months.
Accrued interest related to uncertain tax positions	$ 569,000	569,000
Interest or penalties were recognized	0	$ 0	$ 0
Federal [Member]
Income Taxes [Line Items]
State net operating loss carryforwards	0
State [Member]
Income Taxes [Line Items]
State net operating loss carryforwards	$ 0

Income Taxes - Components of Un

Income Taxes - Components of United's Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets:
Allowance for credit losses	$ 26,941	$ 27,874
Other accrued liabilities	3,478	929
Unrecognized components of net periodic pension costs	20,166	20,901
Unrealized loss on securities available for sale	1,436	2,210
Premises and equipment	93	0
Other real estate owned	6,724	7,500
Deferred mortgage points	0	3,575
Purchase accounting intangibles	41,392	15,248
Total deferred tax assets	100,230	78,237
Deferred tax liabilities:
Deferred mortgage points	3,608	0
Accrued benefits payable	4,061	5,438
Premises and equipment	0	301
Other	13,687	1,856
Total deferred tax liabilities	21,356	7,595
Net deferred tax assets	$ 78,874	$ 70,642

Income Taxes - Reconciliatio110

Income Taxes - Reconciliation of the Total Amounts of Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Unrecognized tax benefits at beginning of year	$ 2,102	$ 3,453
Increase in unrecognized tax benefits as a result of tax positions taken during the current period	673	207
Decreases in the unrecognized tax benefits as a result of a lapse of the applicable statute of limitations	(333)	(1,558)
Unrecognized tax benefits at end of year	$ 2,442	$ 2,102

Employee Benefit Plans - Net Pe

Employee Benefit Plans - Net Periodic Pension Cost (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2,374	$ 2,787	$ 2,160
Interest cost	5,950	5,902	5,379
Expected return on plan assets	(8,089)	(9,290)	(9,102)
Recognized net actuarial loss	4,921	4,980	1,994
Amortization of prior service cost	0	1	1
Net periodic pension cost	$ 5,156	$ 4,380	$ 432
Weighted-Average Assumptions:
Discount rate	4.75%	4.35%	5.20%
Expected return on assets	7.25%	7.50%	7.50%
Rate of Compensation Increase	3.00%	3.00%	3.00%
Prior to Age 45 [Member]
Weighted-Average Assumptions:
Rate of Compensation Increase	3.50%	3.50%	3.50%

Employee Benefit Plans - Schedu

Employee Benefit Plans - Schedule of Amounts Related to Plan recognized as Component of Other Comprehensive Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Pension Plans and Defined Benefit Postretirement Plans Disclosure [Abstract]
Net actuarial loss	$ 2,914	$ 2,402	$ 29,419
Prior service cost	0	(1)	(1)
Actuarial loss	(4,921)	(4,980)	(1,994)
Total recognized in other comprehensive income	$ (2,007)	$ (2,579)	$ 27,424

Employee Benefit Plans - Additi

Employee Benefit Plans - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2008	Dec. 31, 2007
Defined Benefit Plan Disclosure [Line Items]
Unrecognized actuarial gains (losses), before tax	$ 53,991,000
Unrecognized actuarial gains (losses), net of tax	34,014,000
Amortization expected to be recognized	4,411,000
Amortization expected to be recognized, net of tax	2,779,000
Amount of United common stock held in the pension plan	$ 119,711,000	$ 113,748,000	$ 125,885,000
Percentage of equity securities include united common stock	100.00%	100.00%
Percentage of projected benefit obligation	10.00%
Minimum number of days required to be eligible for the participation in the plan	90 days
Percentage of salary deferred under condition one of contribution by company				100.00%	100.00%
First percentage of salary deferred under condition one of contribution by company				3.00%	2.00%
Percentage of salary deferred under condition two of contribution by company				25.00%	25.00%
Second percentage of salary deferred under condition two of contribution by company				1.00%	2.00%
Vesting percentage of employee deferrals				100.00%
Cost related to savings and stock investment plan	$ 2,069,000	$ 1,894,000	1,761,000
Employer contribution in shares of common stock	893,440	876,989
Dividends paid on United common stock	$ 1,173,000	$ 1,139,000	$ 1,133,000
Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Maximum percentage allowed as of contribution to respective accounts by participants	1.00%
Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Maximum percentage allowed as of contribution to respective accounts by participants	100.00%
Common Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Amount of United common stock held in the pension plan	$ 20,629,000	$ 20,464,000
Percentage of equity securities include united common stock	4.00%	3.00%
Maximum percentage limit of common stock to invest in portfolio for any industry	5.00%
Marketable Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Amount of United common stock held in the pension plan	$ 4,894,000	$ 3,915,000
Percentage of equity securities include united common stock	71.00%	67.00%
Maximum percentage limit of common stock to invest in portfolio for any industry	70.00%
Approximate fair value of plan assets	$ 41,322,000	$ 32,440,000
Individual Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Maximum percentage limit of common stock to invest in portfolio for any industry	10.00%
Industry [Member]
Defined Benefit Plan Disclosure [Line Items]
Maximum percentage limit of common stock to invest in portfolio for any industry	15.00%
Securities of U.S. Government or Agencies [Member]
Defined Benefit Plan Disclosure [Line Items]
Maximum percentage limit of common stock to invest in portfolio for any industry	15.00%

Employee Benefit Plans - Reconc

Employee Benefit Plans - Reconciliation of the Beginning and Ending Balances of the Projected Benefit Obligation and the Fair Value of Plan Assets and the Accumulated Benefit Obligation (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Change in Projected Benefit Obligation
Projected Benefit Obligation at the Beginning of the Year	$ 125,403	$ 135,739
Service cost	2,374	2,787	$ 2,160
Interest cost	5,950	5,902	5,379
Actuarial Loss (Gain)	5,114	(9,760)
Benefits Paid	(4,326)	(9,265)
Projected Benefit at the End of the Year	134,515	125,403	135,739
Accumulated Benefit Obligation at the End of the Year	121,548	113,679
Change in Plan Assets
Fair Value of Plan Assets at the Beginning of the Year	113,748	125,885
Actual Return on Plan Assets	10,289	(2,872)
Benefits Paid	(4,326)	(9,265)
Employer Contributions	0	0
Fair value of plan assets at end of year	119,711	113,748	$ 125,885
Net Amount Recognized
Funded Status	(14,804)	(11,655)
Unrecognized Transition Asset	0	0
Unrecognized Prior Service Cost	0	0
Unrecognized Net Loss	53,991	55,998
Net Amount Recognized	$ 39,187	$ 44,343
Weighted-Average Assumptions at the End of the Year
Discount Rate	4.49%	4.75%
Rate of Compensation Increase	3.00%	3.00%
Prior to Age 45 [Member]
Weighted-Average Assumptions at the End of the Year
Rate of Compensation Increase	3.50%	3.50%

Employee Benefit Plans - Asset

Employee Benefit Plans - Asset Allocation for the Defined Benefit Pension Plan as of the Measurement Date, by Asset Category (Detail)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Percentage of Plan Assets	100.00%	100.00%
Marketable Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target Allocation 2016	66.00%
Allowable Allocation Range, Minimum	50.00%
Allowable Allocation Range, Maximum	70.00%
Percentage of Plan Assets	71.00%	67.00%
Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target Allocation 2016	26.00%
Allowable Allocation Range, Minimum	20.00%
Allowable Allocation Range, Maximum	50.00%
Percentage of Plan Assets	26.00%	22.00%
Other [Member]
Defined Benefit Plan Disclosure [Line Items]
Target Allocation 2016	8.00%
Allowable Allocation Range, Minimum	3.00%
Allowable Allocation Range, Maximum	15.00%
Percentage of Plan Assets	3.00%	11.00%

Employee Benefit Plans - Expect

Employee Benefit Plans - Expected Benefit Payments (Detail) $ in Thousands	Dec. 31, 2016USD ($)
Compensation and Retirement Disclosure [Abstract]
2,017	$ 4,626
2,018	4,908
2,019	5,217
2,020	5,568
2,021	5,947
2022 through 2026	$ 35,277

Employee Benefit Plans - Balanc

Employee Benefit Plans - Balances of the Plan Assets, by Fair Value Hierarchy Level (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	$ 119,711	$ 113,748	$ 125,885
Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	1,778	1,467
Mortgage Backed Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	47	63
Collateralized Mortgage Obligations [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	48	54
Municipal Obligations [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	670	836
Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	1,169	1,539
Foreign Bonds Notes and Debentures [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	96	93
Taxable Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	26,816	22,843
Fixed Income Funds Alternative [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	3,898	5,067
Common Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	20,629	20,464
Equity Mutual Funds Domestic Equity Large Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	23,063	20,470
Equity Mutual Funds Domestic Equity Mid Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	6,457	5,804
Equity Mutual Funds Domestic Equity Small Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	13,087	14,080
Equity Mutual Funds Domestic Equity Other [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	910
Equity Mutual Funds International Emerging Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	3,120	6,044
Equity Mutual Funds International Equity Developed [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	12,619	8,772
Equity Mutual Funds Alternative Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	3,456	6,152
Equity Mutual Funds Domestic Balanced Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	1,848
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	117,681	111,163
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	1,778	1,467
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Mortgage Backed Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Collateralized Mortgage Obligations [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Municipal Obligations [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Foreign Bonds Notes and Debentures [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Taxable Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	26,816	22,843
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fixed Income Funds Alternative [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	3,898	5,067
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Common Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	20,629	20,464
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Equity Mutual Funds Domestic Equity Large Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	23,063	20,470
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Equity Mutual Funds Domestic Equity Mid Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	6,457	5,804
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Equity Mutual Funds Domestic Equity Small Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	13,087	14,080
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Equity Mutual Funds Domestic Equity Other [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	910
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Equity Mutual Funds International Emerging Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	3,120	6,044
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Equity Mutual Funds International Equity Developed [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	12,619	8,772
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Equity Mutual Funds Alternative Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	3,456	6,152
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Equity Mutual Funds Domestic Balanced Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	1,848
Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	2,030	2,585
Significant Other Observable Inputs (Level 2) [Member] | Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	0	0
Significant Other Observable Inputs (Level 2) [Member] | Mortgage Backed Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	47	63
Significant Other Observable Inputs (Level 2) [Member] | Collateralized Mortgage Obligations [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	48	54
Significant Other Observable Inputs (Level 2) [Member] | Municipal Obligations [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	670	836
Significant Other Observable Inputs (Level 2) [Member] | Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	1,169	1,539
Significant Other Observable Inputs (Level 2) [Member] | Foreign Bonds Notes and Debentures [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	96	93
Significant Other Observable Inputs (Level 2) [Member] | Taxable Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	0	0
Significant Other Observable Inputs (Level 2) [Member] | Fixed Income Funds Alternative [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	0	0
Significant Other Observable Inputs (Level 2) [Member] | Common Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	0	0
Significant Other Observable Inputs (Level 2) [Member] | Equity Mutual Funds Domestic Equity Large Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	0	0
Significant Other Observable Inputs (Level 2) [Member] | Equity Mutual Funds Domestic Equity Mid Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	0	0
Significant Other Observable Inputs (Level 2) [Member] | Equity Mutual Funds Domestic Equity Small Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	0	0
Significant Other Observable Inputs (Level 2) [Member] | Equity Mutual Funds Domestic Equity Other [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	0
Significant Other Observable Inputs (Level 2) [Member] | Equity Mutual Funds International Emerging Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	0	0
Significant Other Observable Inputs (Level 2) [Member] | Equity Mutual Funds International Equity Developed [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	0	0
Significant Other Observable Inputs (Level 2) [Member] | Equity Mutual Funds Alternative Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	0	0
Significant Other Observable Inputs (Level 2) [Member] | Equity Mutual Funds Domestic Balanced Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	0
Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	0	0
Significant Unobservable Inputs (Level 3) [Member] | Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	0	0
Significant Unobservable Inputs (Level 3) [Member] | Mortgage Backed Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	0	0
Significant Unobservable Inputs (Level 3) [Member] | Collateralized Mortgage Obligations [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	0	0
Significant Unobservable Inputs (Level 3) [Member] | Municipal Obligations [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	0	0
Significant Unobservable Inputs (Level 3) [Member] | Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	0	0
Significant Unobservable Inputs (Level 3) [Member] | Foreign Bonds Notes and Debentures [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	0	0
Significant Unobservable Inputs (Level 3) [Member] | Taxable Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	0	0
Significant Unobservable Inputs (Level 3) [Member] | Fixed Income Funds Alternative [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	0	0
Significant Unobservable Inputs (Level 3) [Member] | Common Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	0	0
Significant Unobservable Inputs (Level 3) [Member] | Equity Mutual Funds Domestic Equity Large Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	0	0
Significant Unobservable Inputs (Level 3) [Member] | Equity Mutual Funds Domestic Equity Mid Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	0	0
Significant Unobservable Inputs (Level 3) [Member] | Equity Mutual Funds Domestic Equity Small Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	0	0
Significant Unobservable Inputs (Level 3) [Member] | Equity Mutual Funds Domestic Equity Other [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	0
Significant Unobservable Inputs (Level 3) [Member] | Equity Mutual Funds International Emerging Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	0	0
Significant Unobservable Inputs (Level 3) [Member] | Equity Mutual Funds International Equity Developed [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	0	0
Significant Unobservable Inputs (Level 3) [Member] | Equity Mutual Funds Alternative Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	0	$ 0
Significant Unobservable Inputs (Level 3) [Member] | Equity Mutual Funds Domestic Balanced Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset at fair value	$ 0

Stock Based Compensation - Addi

Stock Based Compensation - Additional Information (Detail) - USD ($)	May 18, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Authorized shares of stock, option plan, maximum	1,700,000
Aggregate number of shares issued in respect of restricted stock awards	500,000
Options available for award each plan year	1,200,000
Maximum number of shares of restricted stock or shares subject to a restricted stock units award granted		50,000
Maximum number of options and SARs		100,000
Maximum number of stock options and SARs awarded		10,000
Maximum number of Shares of restricted stock or shares subject to a restricted stock units award granted to individual non-employee director		5,000
Vesting period of awards		1/3 per year
Recognition of compensation expense		$ 2,817,000	$ 2,484,000	$ 2,195,000
Number of share available for grant for prior plans		0
Maximum term for awards granted (years)		10 years
Weighted average risk free interest rate		1.47%
Weighted average dividend yield		3.00%
Weighted average volatility factors of the expected market price of United's common stock		0.281%
Weighted-average expected option life		6 years 10 months 24 days
Estimated fair value of the options at the date of grant		$ 6.97
Total unrecognized compensation cost related to nonvested option awards		$ 1,951,000
Weighted-average expense recognition period		1 year 2 months 12 days
Total fair value of awards vested		$ 1,104,000
Cash received from options exercised under the plans		$ 13,337,000	$ 7,871,000	$ 9,878,000
Shares issued related stock option exercises		519,482	259,454	468,933
Weighted-average grant-date fair value of options granted		$ 6.97	$ 7.23	$ 6.42
Total intrinsic value of options exercised		$ 11,001,000	$ 2,380,000	$ 4,832,000
Excess tax benefits from stock-based compensation arrangements		4,008,000	$ 1,023,000	$ 73,000
Nonvested Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost related to nonvested option awards		$ 2,986,000
Weighted-average expense recognition period		1 year 2 months 12 days
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Options granted		967,285
Number of shares granted		289,637
Weighted-average grant-date fair value of options granted		$ 35.04
Vesting period		4 years

Stock Based Compensation - Summ

Stock Based Compensation - Summary of Stock Option Plans (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule Of Stock Options [Line Items]
Shares, Outstanding, Beginning balance	1,207,110
Shares, Granted	189,780
Shares, Exercised	519,482	259,454	468,933
Shares, Forfeited or expired	27,243
Shares, Outstanding, Ending balance	1,411,735	1,207,110
Shares, Exercisable at December 31, 2015	981,457
Aggregate Intrinsic Value, Outstanding at December 31, 2015	$ 25,695
Aggregate Intrinsic Value, Exercisable at December 31, 2015	$ 20,294
Weighted Average Remaining Contractual Term, Outstanding at December 31, 2015	5 years 9 months 18 days
Weighted Average Remaining Contractual Term, Exercisable at December 31, 2015	4 years 8 months 12 days
Weighted Average Exercise Price, Outstanding, Beginning balance	$ 28.15
Weighted Average Exercise Price, Granted	35.04
Weighted Average Exercise Price, Exercised	19.76
Weighted Average Exercise Price, Forfeited or expired	30.80
Weighted Average Exercise Price, Outstanding, Ending balance	28.05	$ 28.15
Weighted Average Exercise Price, Exercisable	$ 25.57
Bank of Georgetown [Member]
Schedule Of Stock Options [Line Items]
Assumed in acquisition of subsidiary	561,570
Weighted Average Exercise Price, Exercisable	$ 17.90

Stock Based Compensation - Stat

Stock Based Compensation - Status of United's Nonvested Stock Option Awards (Detail)	12 Months Ended
	Dec. 31, 2016$ / sharesshares
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Shares, Nonvested, Beginning balance | shares	426,395
Shares, Granted | shares	189,780
Shares, Vested | shares	167,683
Shares, Forfeited or expired | shares	18,214
Shares, Nonvested, Ending balance | shares	430,278
Weighted-Average Grant Date Fair Value Per Share, Nonvested Beginning balance | $ / shares	$ 6.68
Weighted-Average Grant Date Fair Value Per Share, Granted | $ / shares	6.97
Weighted-Average Grant Date Fair Value Per Share, Vested | $ / shares	6.58
Weighted-Average Grant Date Fair Value Per Share, Forfeited or expired | $ / shares	6.84
Weighted-Average Grant Date Fair Value Per Share, Nonvested Ending balance | $ / shares	$ 6.84

Stock Based Compensation - Chan

Stock Based Compensation - Changes to United's Restricted Common Shares (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-Average Grant Date Fair Value Per Share, Granted	$ 6.97	$ 7.23	$ 6.42
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Outstanding, Beginning balance	129,772
Shares, Granted	64,092
Shares, Vested	50,641
Shares, Forfeited	5,955
Number of Shares, Outstanding, Ending balance	137,268	129,772
Weighted-Average Grant Date Fair Value Per Share, Outstanding, Beginning balance	$ 31.69
Weighted-Average Grant Date Fair Value Per Share, Granted	35.04
Weighted-Average Grant Date Fair Value Per Share, Vested	30.56
Weighted-Average Grant Date Fair Value Per Share, Forfeited	32.97
Weighted-Average Grant Date Fair Value Per Share, Outstanding, Ending balance	$ 33.61	$ 31.69

Commitments and Contingent L122

Commitments and Contingent Liabilities - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Loss Contingencies [Line Items]
Loan commitments outstanding	$ 2,823,396,000	$ 2,587,957,000
Loan commitments expiry period	1 year
Commercial Letters of Credit [Member]
Loss Contingencies [Line Items]
Letters of credit issued	$ 9,000	226,000
Standby Letters of Credit [Member]
Loss Contingencies [Line Items]
Letters of credit issued	$ 121,584,000	$ 135,146,000

Derivative Financial Instrum123

Derivative Financial Instruments - Schedule of Derivative Instruments (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Total Derivatives Used for Interest Rate Risk Management and Designated as Hedges	$ 94,582,000	$ 97,157,000
Average Pay Rate	3.64%	3.64%
Fair Value Hedging [Member] | Interest Rate Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount, Pay Fixed Swap (Hedging Commercial Loans)	$ 94,582,000	$ 97,157,000
Cash Flow Hedging [Member] | Interest Rate Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount, Pay Fixed Swap (Hedging Commercial Loans)	$ 94,582,000	$ 97,157,000

Derivative Financial Instrum124

Derivative Financial Instruments - Schedule of Fair Value Derivative Financial Instruments (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Derivative [Line Items]
Asset derivatives designated as hedging instruments	$ 24	$ 0
Asset derivatives not designated as hedging instruments	2,267	2,942
Total asset derivatives	2,291	2,942
Liability derivatives designated as hedging instruments	338	1,179
Liability derivatives not designated as hedging instruments	2,267	2,942
Total liability derivatives	2,605	4,121
Interest Rate Contracts [Member] | Other Assets [Member]
Derivative [Line Items]
Asset derivatives designated as hedging instruments	24	0
Asset derivatives not designated as hedging instruments	2,267	2,942
Interest Rate Contracts [Member] | Other Liabilities [Member]
Derivative [Line Items]
Liability derivatives designated as hedging instruments	338	1,179
Liability derivatives not designated as hedging instruments	$ 2,267	$ 2,942

Derivative Financial Instrum125

Derivative Financial Instruments - Schedule of Derivative Financial Instruments on Statements of Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Interest Rate Contracts [Member]
Derivative [Line Items]
Derivatives in fair value hedging relationships	$ (30)	$ (813)	$ (1,047)
Interest Income/ (Expense) [Member]
Derivative [Line Items]
Derivatives in fair value hedging relationships	(30)	(813)	(1,047)
Interest Income/ (Expense) [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Derivatives in fair value hedging relationships	(30)	(813)	(1,047)
Other Income [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative instruments not designated as hedging instruments, loss	0	0	0
Derivative instruments not designated as hedging instruments, net	$ 0	$ 0	$ 0

Comprehensive Income - Componen

Comprehensive Income - Components of Total Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Net income	$ 39,106	$ 41,479	$ 31,792	$ 34,706	$ 33,476	$ 35,047	$ 34,809	$ 34,627	$ 147,083	$ 137,959	$ 129,888
AFS securities with OTTI charges during the period									(77)	(113)	(6,478)
Related income tax effect									28	41	2,267
Income tax rate change									208	316	0
Less : OTTI charges recognized in net income									33	47	6,478
Related income tax benefit									(12)	(17)	(2,267)
Reclassification of previous noncredit OTTI to credit OTTI									415	0	8,413
Related income tax benefit									(150)	0	(2,944)
Net unrealized gains on AFS securities with OTTI									445	274	5,469
Change in net unrealized (losses) gains on AFS securities arising during the period									(12,931)	(6,672)	33,078
Related income tax effect									4,867	2,415	(11,577)
Net reclassification adjustment for gains included in net income									(255)	(133)	(3,357)
Related income tax expense									92	48	1,175
Total AFS securities - all other									(8,227)	(4,342)	19,319
Net effect of AFS securities on other comprehensive income									(7,782)	(4,068)	24,788
Accretion on the unrealized loss for securities transferred from AFS to the HTM investment portfolio prior to call or maturity									9	8	8
Related income tax expense									(3)	(3)	(3)
Net effect of HTM securities on other comprehensive income									6	5	5
Defined benefit pension plan:
Net actuarial loss during the period									(2,914)	(2,402)	(29,419)
Related income tax expense (benefit)									1,077	944	10,649
Amortization of prior service cost recognized in net income									0	1	1
Related income tax benefit									0	0	0
Amortization of net actuarial loss recognized in net income									4,921	4,980	1,994
Related income tax benefit									(1,813)	(1,908)	(735)
Net effect of change in defined benefit pension plan on other comprehensive income									1,271	1,615	(17,510)
Net current-period other comprehensive income, net of tax									(6,505)	(2,448)	7,283
Comprehensive income, net of tax									$ 140,578	$ 135,511	$ 137,171

Comprehensive Income - Compo127

Comprehensive Income - Components of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at January 1, 2016	$ 1,712,635	$ 1,656,160	$ 1,041,732
Net current-period other comprehensive income, net of tax	(6,505)	(2,448)	7,283
Balance at December 31, 2016	2,235,747	1,712,635	1,656,160
Pension Plan [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at January 1, 2016	(35,640)
Other comprehensive income before reclassification	0
Amounts reclassified from accumulated other comprehensive income	1,271
Net current-period other comprehensive income, net of tax	1,271
Balance at December 31, 2016	(34,369)	(35,640)
Unrealized Gains/Losses on AFS Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at January 1, 2016	(2,515)
Other comprehensive income before reclassification	(7,884)
Amounts reclassified from accumulated other comprehensive income	102
Net current-period other comprehensive income, net of tax	(7,782)
Balance at December 31, 2016	(10,297)	(2,515)
Accumulated Unrealized Loss On Securities Available For Sale Transferred To Held To Maturity [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at January 1, 2016	(57)
Other comprehensive income before reclassification	6
Amounts reclassified from accumulated other comprehensive income	0
Net current-period other comprehensive income, net of tax	6
Balance at December 31, 2016	(51)	(57)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at January 1, 2016	(38,212)	(35,764)	(43,047)
Other comprehensive income before reclassification	(7,878)
Amounts reclassified from accumulated other comprehensive income	1,373
Net current-period other comprehensive income, net of tax	(6,505)	(2,448)	7,283
Balance at December 31, 2016	$ (44,717)	$ (38,212)	$ (35,764)

Comprehensive Income - Reclassi

Comprehensive Income - Reclassifications Out of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Available for sale ("AFS") securities:
Net reclassification adjustment for losses (gains) included in net income									$ 313	$ 202	$ 3,366
Income before income taxes									222,658	203,489	194,886
Related income tax effect	$ (22,472)	$ (18,846)	$ (16,378)	$ (17,879)	$ (16,864)	$ (16,217)	$ (17,145)	$ (15,304)	(75,575)	(65,530)	(64,998)
Net earnings allocated to common shareholders	39,106	41,479	31,792	34,706	33,476	35,047	34,809	34,627	147,083	137,959	129,888
Pension plan:
Net actuarial loss									(2,914)	(2,402)	(29,419)
Amortization of net actuarial loss									4,921	4,980	1,994
Income before income taxes									222,658	203,489	194,886
Related income tax effect	(22,472)	(18,846)	(16,378)	(17,879)	(16,864)	(16,217)	(17,145)	(15,304)	(75,575)	(65,530)	(64,998)
Net earnings allocated to common shareholders	$ 39,106	$ 41,479	$ 31,792	$ 34,706	$ 33,476	$ 35,047	$ 34,809	$ 34,627	147,083	$ 137,959	$ 129,888
Reclassification out of Accumulated Other Comprehensive Income [Member]
Available for sale ("AFS") securities:
Net earnings allocated to common shareholders									1,373
Pension plan:
Net earnings allocated to common shareholders									1,373
Reclassification out of Accumulated Other Comprehensive Income [Member] | Unrealized Gains/Losses on AFS Securities [Member]
Available for sale ("AFS") securities:
Reclassification of previous noncredit OTTI to credit OTTI									415
Net reclassification adjustment for losses (gains) included in net income									(255)
Income before income taxes									160
Related income tax effect									(58)
Net earnings allocated to common shareholders									102
Pension plan:
Income before income taxes									160
Related income tax effect									(58)
Net earnings allocated to common shareholders									102
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
Available for sale ("AFS") securities:
Income before income taxes									2,007
Related income tax effect									(736)
Net earnings allocated to common shareholders									1,271
Pension plan:
Net actuarial loss									(2,914)
Amortization of net actuarial loss									4,921
Income before income taxes									2,007
Related income tax effect									(736)
Net earnings allocated to common shareholders									$ 1,271

United Bankshares, Inc. (Par129

United Bankshares, Inc. (Parent Company Only) Financial Information - Condensed Balance Sheets (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and due from banks	$ 175,468	$ 136,690
Securities available for sale	1,259,214	1,066,334
Securities held to maturity	31,178	36,319
Other investment securities	111,166	98,749
Other assets	414,840	378,250
TOTAL ASSETS	14,508,892	12,577,944
Accrued expenses and other liabilities	93,657	84,569
Shareholders' equity (including other accumulated comprehensive loss of $44,717 and $38,212 at December 31, 2016 and 2015, respectively)	2,235,747	1,712,635	$ 1,656,160	$ 1,041,732
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY	14,508,892	12,577,944
United Bankshares [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and due from banks	129,486	39,680
Securities available for sale	4,108	3,168
Securities held to maturity	20	20
Other investment securities	100	100
Bank subsidiaries	2,267,561	1,835,440
Nonbank subsidiaries	6,572	6,484
Other assets	15,404	13,904
TOTAL ASSETS	2,423,251	1,898,796
Junior subordinated debentures of subsidiary trusts	128,868	128,868
Accrued expenses and other liabilities	58,636	57,293
Shareholders' equity (including other accumulated comprehensive loss of $44,717 and $38,212 at December 31, 2016 and 2015, respectively)	2,235,747	1,712,635
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY	$ 2,423,251	$ 1,898,796

United Bankshares, Inc. (Par130

United Bankshares, Inc. (Parent Company Only) Financial Information - Condensed Balance Sheets (Parenthetical) (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Condensed Balance Sheet Statements, Captions [Line Items]
Accumulated other comprehensive loss	$ 44,717	$ 38,212
United Bankshares [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Accumulated other comprehensive loss	$ 44,717	$ 38,212

United Bankshares, Inc. (Par131

United Bankshares, Inc. (Parent Company Only) Financial Information - Condensed Statements of Income (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Condensed Income Statements, Captions [Line Items]
Net interest income	$ 113,253	$ 111,069	$ 102,725	$ 98,284	$ 97,155	$ 96,318	$ 95,902	$ 94,749	$ 425,331	$ 384,124	$ 375,708
Income before income taxes									222,658	203,489	194,886
Applicable income tax benefit	22,472	18,846	16,378	17,879	16,864	16,217	17,145	15,304	75,575	65,530	64,998
Net income	$ 39,106	$ 41,479	$ 31,792	$ 34,706	$ 33,476	$ 35,047	$ 34,809	$ 34,627	147,083	137,959	129,888
United Bankshares [Member]
Condensed Income Statements, Captions [Line Items]
Dividends from banking subsidiaries									75,000	70,500	97,000
Net interest income									66	59	59
Bank subsidiaries									35,792	28,955	19,400
Nonbank subsidiaries									27	27	27
Other income									8	58	96
Total Income									110,893	99,599	116,582
Operating expenses									40,180	30,016	24,043
Income before income taxes									70,713	69,583	92,539
Applicable income tax benefit									(1,626)	(316)	(1,332)
Income Before Equity in Undistributed Net Income of Subsidiaries									72,339	69,899	93,871
Bank subsidiaries									74,656	68,012	35,978
Nonbank subsidiaries									88	48	39
Net income									$ 147,083	$ 137,959	$ 129,888

United Bankshares, Inc. (Par132

United Bankshares, Inc. (Parent Company Only) Financial Information - Condensed Statements of Cash Flows (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Condensed Cash Flow Statements, Captions [Line Items]
Net income	$ 39,106	$ 41,479	$ 31,792	$ 34,706	$ 33,476	$ 35,047	$ 34,809	$ 34,627	$ 147,083	$ 137,959	$ 129,888
Amortization of net periodic pension costs									5,156	4,380	432
Stock-based compensation									2,817	2,484	2,195
Net gain on securities transactions	(62)	$ (1)	$ (213)	(4)	(29)	$ (111)	$ (3)	(12)	(280)	(155)	3,112
NET CASH PROVIDED BY OPERATING ACTIVITIES									166,726	173,878	152,568
Net cash paid in acquisition of subsidiary									29,330	0	97,296
NET CASH PROVIDED BY (USED IN) INVESTING ACTIVITIES									30,960	(185,298)	(212,582)
Proceeds from issuance of common stock									199,916	0	0
Cash dividends paid									(96,351)	(88,864)	(82,496)
Acquisition of treasury stock									(1)	(1)	(2)
Proceeds from sale of treasury stock from deferred compensation plan									1	1	81
Excess tax benefits from stock-based compensation arrangements									4,008	1,023	73
Proceeds from exercise of stock options									13,337	7,871	9,878
NET CASH PROVIDED BY (USED IN) FINANCING ACTIVITIES									379,506	115,691	396,461
Increase (Decrease) in Cash and Cash Equivalents									577,192	104,271	336,447
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR				857,335				753,064	857,335	753,064	416,617
CASH AND CASH EQUIVALENTS AT END OF YEAR	1,434,527				857,335				1,434,527	857,335	753,064
United Bankshares [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net income									147,083	137,959	129,888
Equity in undistributed net income of subsidiaries									(74,744)	(68,060)	(36,018)
Amortization of net periodic pension costs									393	384	34
Stock-based compensation									2,817	2,484	2,195
Net gain on securities transactions									(8)	(54)	(96)
Net change in other assets and liabilities									(6,401)	8,998	5,172
NET CASH PROVIDED BY OPERATING ACTIVITIES									69,140	81,711	101,175
Net purchases of securities									(234)	(1,047)	(90)
Net cash paid in acquisition of subsidiary									(10)	0	(33,271)
Increase in investment in subsidiaries									(100,000)	0	0
Change in other investment securities									0	2	23
NET CASH PROVIDED BY (USED IN) INVESTING ACTIVITIES									(100,244)	(1,045)	(33,338)
Proceeds from issuance of common stock									199,916	0	0
Cash dividends paid									(96,351)	(88,864)	(82,496)
Acquisition of treasury stock									(1)	(1)	(2)
Proceeds from sale of treasury stock from deferred compensation plan									1	1	81
Excess tax benefits from stock-based compensation arrangements									4,008	1,023	73
Proceeds from exercise of stock options									13,337	7,871	9,878
NET CASH PROVIDED BY (USED IN) FINANCING ACTIVITIES									120,910	(79,970)	(72,466)
Increase (Decrease) in Cash and Cash Equivalents									89,806	696	(4,629)
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR				$ 39,680				$ 38,984	39,680	38,984	43,613
CASH AND CASH EQUIVALENTS AT END OF YEAR	$ 129,486				$ 39,680				$ 129,486	$ 39,680	$ 38,984

Regulatory Matters - Additional

Regulatory Matters - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Regulated Operations [Abstract]
Average reserve balances to be maintained by subsidiary banks	$ 606,898,000	$ 567,698,000
Average reserve balances required by subsidiary banks	361,521,000	$ 330,953,000
Retained net profits available for distribution to United Bankshares, Inc. by its banking subsidiaries as dividends	$ 148,219,000
Maximum loan to parent company by subsidiaries as percentage it's of capital and surplus	10.00%
Maximum amount of loan to parent company by subsidiaries	$ 181,926,000

Regulatory Matters - Capital Am

Regulatory Matters - Capital Amounts and Ratios (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
United Bankshares [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital to Risk-Weighted Assets, Actual Amount	$ 1,699,984	$ 1,331,492
Tier 1 Capital to Risk-Weighted Assets, Actual Amount	1,625,543	1,254,555
Common Tier I Capital to Risk Weighted Assets, Actual Amount	1,393,743	1,022,755
Tier 1 Capital to Average Assets, Amount	$ 1,625,543	$ 1,254,555
Total Capital to Risk-Weighted Assets, Actual Ratio	14.90%	12.60%
Tier 1 Capital to Risk-Weighted Assets, Actual Ratio	14.20%	11.90%
Common Tier I Capital to Risk Weighted Assets,	12.20%	9.70%
Tier 1 Capital to Average Assets, Actual Ratio	12.20%	10.70%
Total Capital to Risk-Weighted Assets, For Capital Adequacy Purposes, Amount	$ 915,479	$ 845,876
Tier 1 Capital to Risk-Weighted Assets, For Capital Adequacy Purposes, Amount	686,609	634,407
Common Tier I Capital to Risk Weighted Assets,	514,957	475,805
Tier 1 Capital to Average Assets, For Capital Adequacy Purposes, Amount	$ 535,227	$ 468,776
Total Capital to Risk-Weighted Assets, For Capital Adequacy, Ratio	8.00%	8.00%
Tier 1 Capital to Risk-Weighted Assets, For Capital Adequacy Purposes, Ratio	6.00%	6.00%
Common Tier I Capital to Risk Weighted Assets,	4.50%	4.50%
Tier 1 Capital to Average Assets, For Capital Adequacy Purposes, Ratio	4.00%	4.00%
Total Capital to Risk-Weighted Assets, To Be Well Capitalized, Amount	$ 1,144,348	$ 1,057,345
Tier 1 Capital to Risk-Weighted Assets, To Be Well Capitalized, Amount	915,479	845,876
Common Tier I Capital to Risk Weighted Assets,	743,826	687,274
Tier 1 Capital to Average Assets, To Be Well Capitalized, Amount	$ 669,033	$ 585,970
Total Capital to Risk-Weighted Assets, To Be Well Capitalized, Ratio	10.00%	10.00%
Tier 1 Capital to Risk-Weighted Assets, To Be Well Capitalized, Ratio	8.00%	8.00%
Common Tier I Capital to Risk Weighted Assets,	6.50%	6.50%
Tier 1 Capital to Average Assets To Be Well Capitalized, Ratio	5.00%	5.00%
United Bank (WV) [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital to Risk-Weighted Assets, Actual Amount	$ 638,756	$ 591,825
Tier 1 Capital to Risk-Weighted Assets, Actual Amount	590,530	547,903
Common Tier I Capital to Risk Weighted Assets, Actual Amount	590,530	547,903
Tier 1 Capital to Average Assets, Amount	$ 590,530	$ 547,903
Total Capital to Risk-Weighted Assets, Actual Ratio	12.20%	12.60%
Tier 1 Capital to Risk-Weighted Assets, Actual Ratio	11.30%	11.60%
Common Tier I Capital to Risk Weighted Assets,	11.30%	11.60%
Tier 1 Capital to Average Assets, Actual Ratio	9.80%	10.20%
Total Capital to Risk-Weighted Assets, For Capital Adequacy Purposes, Amount	$ 418,700	$ 377,225
Tier 1 Capital to Risk-Weighted Assets, For Capital Adequacy Purposes, Amount	314,025	282,919
Common Tier I Capital to Risk Weighted Assets,	235,519	212,189
Tier 1 Capital to Average Assets, For Capital Adequacy Purposes, Amount	$ 239,986	$ 214,519
Total Capital to Risk-Weighted Assets, For Capital Adequacy, Ratio	8.00%	8.00%
Tier 1 Capital to Risk-Weighted Assets, For Capital Adequacy Purposes, Ratio	6.00%	6.00%
Common Tier I Capital to Risk Weighted Assets,	4.50%	4.50%
Tier 1 Capital to Average Assets, For Capital Adequacy Purposes, Ratio	4.00%	4.00%
Total Capital to Risk-Weighted Assets, To Be Well Capitalized, Amount	$ 523,375	$ 471,532
Tier 1 Capital to Risk-Weighted Assets, To Be Well Capitalized, Amount	418,700	377,225
Common Tier I Capital to Risk Weighted Assets,	340,194	306,496
Tier 1 Capital to Average Assets, To Be Well Capitalized, Amount	$ 299,983	$ 268,149
Total Capital to Risk-Weighted Assets, To Be Well Capitalized, Ratio	10.00%	10.00%
Tier 1 Capital to Risk-Weighted Assets, To Be Well Capitalized, Ratio	8.00%	8.00%
Common Tier I Capital to Risk Weighted Assets,	6.50%	6.50%
Tier 1 Capital to Average Assets To Be Well Capitalized, Ratio	5.00%	5.00%
United Bank (VA) [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital to Risk-Weighted Assets, Actual Amount	$ 953,891	$ 720,676
Tier 1 Capital to Risk-Weighted Assets, Actual Amount	928,301	687,937
Common Tier I Capital to Risk Weighted Assets, Actual Amount	928,301	687,937
Tier 1 Capital to Average Assets, Amount	$ 928,301	$ 687,937
Total Capital to Risk-Weighted Assets, Actual Ratio	15.10%	12.20%
Tier 1 Capital to Risk-Weighted Assets, Actual Ratio	14.70%	11.70%
Common Tier I Capital to Risk Weighted Assets,	14.70%	11.70%
Tier 1 Capital to Average Assets, Actual Ratio	11.60%	10.50%
Total Capital to Risk-Weighted Assets, For Capital Adequacy Purposes, Amount	$ 504,445	$ 471,303
Tier 1 Capital to Risk-Weighted Assets, For Capital Adequacy Purposes, Amount	378,334	353,477
Common Tier I Capital to Risk Weighted Assets,	283,751	265,108
Tier 1 Capital to Average Assets, For Capital Adequacy Purposes, Amount	$ 318,925	$ 263,306
Total Capital to Risk-Weighted Assets, For Capital Adequacy, Ratio	8.00%	8.00%
Tier 1 Capital to Risk-Weighted Assets, For Capital Adequacy Purposes, Ratio	6.00%	6.00%
Common Tier I Capital to Risk Weighted Assets,	4.50%	4.50%
Tier 1 Capital to Average Assets, For Capital Adequacy Purposes, Ratio	4.00%	4.00%
Total Capital to Risk-Weighted Assets, To Be Well Capitalized, Amount	$ 630,557	$ 589,129
Tier 1 Capital to Risk-Weighted Assets, To Be Well Capitalized, Amount	504,445	471,303
Common Tier I Capital to Risk Weighted Assets,	409,862	382,934
Tier 1 Capital to Average Assets, To Be Well Capitalized, Amount	$ 398,656	$ 329,132
Total Capital to Risk-Weighted Assets, To Be Well Capitalized, Ratio	10.00%	10.00%
Tier 1 Capital to Risk-Weighted Assets, To Be Well Capitalized, Ratio	8.00%	8.00%
Common Tier I Capital to Risk Weighted Assets,	6.50%	6.50%
Tier 1 Capital to Average Assets To Be Well Capitalized, Ratio	5.00%	5.00%

Fair Values of Financial Ins135

Fair Values of Financial Instruments - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Discount rates utilized, minimum	4.50%
Discount rates utilized, maximum	11.75%
Amount of decrease in fair value of securities	$ 5,600,000
Transfers from Level 1 to Level 2 for financial assets	0	$ 0
Transfers from Level 2 to Level 1 for financial assets	0	0
Transfers from Level 1 to Level 2 for financial liabilities	0	0
Transfers from Level 2 to Level 1 for financial liabilities	0	0
Nonrecurring fair value adjustments on loans held for sale	0
Fair value measurement of intangible assets	$ 0	$ 0
Trust Preferred Collateralized Debt Obligations [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Decrease in fair value of securities	17.00%
Increase in discount rates, basis point	2.00%

Fair Values of Financial Ins136

Fair Values of Financial Instruments - Schedule of Financial Assets and Liabilities Measured at Fair Value (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale equity securities	$ 13,828
Total available for sale securities	1,259,214	$ 1,066,334
Derivative financial assets	2,291	2,942
Derivative financial liabilities	2,605	4,121
Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	1,245,386	1,060,879
Available for sale equity securities	13,828	5,455
Total available for sale securities	1,259,214	1,066,334
U.S. Treasury Securities and Obligations of U.S. Government Corporations and Agencies [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	95,786	73,786
U.S. Treasury Securities and Obligations of U.S. Government Corporations and Agencies [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	95,786	73,786
State and Political Subdivisions [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	192,812	133,778
State and Political Subdivisions [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	192,812	133,778
Residential Mortgage-Backed Securities, Agency [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	584,096	477,982
Residential Mortgage-Backed Securities, Agency [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	584,096	477,982
Residential Mortgage-Backed Securities, Non-agency [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	7,043	9,571
Residential Mortgage-Backed Securities, Non-agency [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	7,043	9,571
Asset-Backed Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	217	3,399
Asset-Backed Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	217	3,399
Commercial Mortgage-Backed Securities, Agency [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	305,341	305,935
Commercial Mortgage-Backed Securities, Agency [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	305,341	305,935
Trust Preferred Collateralized Debt Obligations [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	33,552	34,686
Trust Preferred Collateralized Debt Obligations [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	33,552	34,686
Single Issue Trust Preferred Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	11,477	11,693
Single Issue Trust Preferred Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	11,477	11,693
Corporate Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	15,062	10,049
Corporate Bonds [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	15,062	10,049
Financial Services Industry [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale equity securities	10,735	2,723
Other Equity Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale equity securities	1,273	1,136
Interest Rate Contracts [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative financial assets	2,291	2,942
Derivative financial liabilities	2,605	4,121
Equity Mutual Funds [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale equity securities	1,820	1,596
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	4,465	3,532
Derivative financial assets	0	0
Derivative financial liabilities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	0	0
Available for sale equity securities	4,465	3,532
Total available for sale securities	4,465	3,532
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | U.S. Treasury Securities and Obligations of U.S. Government Corporations and Agencies [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | State and Political Subdivisions [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Residential Mortgage-Backed Securities, Agency [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Residential Mortgage-Backed Securities, Non-agency [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Asset-Backed Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Commercial Mortgage-Backed Securities, Agency [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Trust Preferred Collateralized Debt Obligations [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Single Issue Trust Preferred Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Corporate Bonds [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Financial Services Industry [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale equity securities	1,372	800
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Equity Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale equity securities	1,273	1,136
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Interest Rate Contracts [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative financial assets	0	0
Derivative financial liabilities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Equity Mutual Funds [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale equity securities	1,820	1,596
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	1,221,197	1,028,116
Derivative financial assets	2,291	2,942
Derivative financial liabilities	2,605	4,121
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	1,211,834	1,026,193
Available for sale equity securities	9,363	1,923
Total available for sale securities	1,221,197	1,028,116
Significant Other Observable Inputs (Level 2) [Member] | U.S. Treasury Securities and Obligations of U.S. Government Corporations and Agencies [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	95,786	73,786
Significant Other Observable Inputs (Level 2) [Member] | State and Political Subdivisions [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	192,812	133,778
Significant Other Observable Inputs (Level 2) [Member] | Residential Mortgage-Backed Securities, Agency [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	584,096	477,982
Significant Other Observable Inputs (Level 2) [Member] | Residential Mortgage-Backed Securities, Non-agency [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	7,043	9,571
Significant Other Observable Inputs (Level 2) [Member] | Asset-Backed Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	217	3,399
Significant Other Observable Inputs (Level 2) [Member] | Commercial Mortgage-Backed Securities, Agency [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	305,341	305,935
Significant Other Observable Inputs (Level 2) [Member] | Trust Preferred Collateralized Debt Obligations [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	0	0
Significant Other Observable Inputs (Level 2) [Member] | Single Issue Trust Preferred Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	11,477	11,693
Significant Other Observable Inputs (Level 2) [Member] | Corporate Bonds [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	15,062	10,049
Significant Other Observable Inputs (Level 2) [Member] | Financial Services Industry [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale equity securities	9,363	1,923
Significant Other Observable Inputs (Level 2) [Member] | Other Equity Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale equity securities	0	0
Significant Other Observable Inputs (Level 2) [Member] | Interest Rate Contracts [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative financial assets	2,291	2,942
Derivative financial liabilities	2,605	4,121
Significant Other Observable Inputs (Level 2) [Member] | Equity Mutual Funds [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale equity securities	0	0
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	33,552	34,686
Derivative financial assets	0	0
Derivative financial liabilities	0	0
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	33,552	34,686
Available for sale equity securities	0	0
Total available for sale securities	33,552	34,686
Significant Unobservable Inputs (Level 3) [Member] | U.S. Treasury Securities and Obligations of U.S. Government Corporations and Agencies [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	0	0
Significant Unobservable Inputs (Level 3) [Member] | State and Political Subdivisions [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	0	0
Significant Unobservable Inputs (Level 3) [Member] | Residential Mortgage-Backed Securities, Agency [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	0	0
Significant Unobservable Inputs (Level 3) [Member] | Residential Mortgage-Backed Securities, Non-agency [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	0	0
Significant Unobservable Inputs (Level 3) [Member] | Asset-Backed Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	0	0
Significant Unobservable Inputs (Level 3) [Member] | Commercial Mortgage-Backed Securities, Agency [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	0	0
Significant Unobservable Inputs (Level 3) [Member] | Trust Preferred Collateralized Debt Obligations [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	33,552	34,686
Significant Unobservable Inputs (Level 3) [Member] | Single Issue Trust Preferred Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	0	0
Significant Unobservable Inputs (Level 3) [Member] | Corporate Bonds [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	0	0
Significant Unobservable Inputs (Level 3) [Member] | Financial Services Industry [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale equity securities	0	0
Significant Unobservable Inputs (Level 3) [Member] | Other Equity Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale equity securities	0	0
Significant Unobservable Inputs (Level 3) [Member] | Interest Rate Contracts [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative financial assets	0	0
Derivative financial liabilities	0	0
Significant Unobservable Inputs (Level 3) [Member] | Equity Mutual Funds [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale equity securities	$ 0	$ 0

Fair Values of Financial Ins137

Fair Values of Financial Instruments - Schedule of Additional Information about Financial Assets and Liabilities Measured at Fair Value Utilized Level 3 (Detail) - Trust Preferred Collateralized Debt Obligations [Member] - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Balance, beginning of year	$ 34,686	$ 39,558
Included in earnings (or changes in net assets)	0	(34)
Included in other comprehensive income	(1,134)	(4,838)
Purchases, issuances, and settlements	0	0
Transfers in and/or out of Level 3	0	0
Balance, ending of year	33,552	34,686
The amount of total gains or losses for the period included in earnings (or changes in net assets) attributable to the change in unrealized gains or losses relating to assets still held at reporting date	$ 0	$ 0

Fair Values of Financial Ins138

Fair Values of Financial Instruments - Summary of Financial Assets Measured at Fair Value on Nonrecurring Basis (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
YTD Losses, Impaired Loans	$ 5,119	$ 8,485
YTD Losses, OREO	2,086	1,141
Impaired Loans	80,505	69,368
OREO	31,510	32,228
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Impaired Loans	0	0
OREO	0	0
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Impaired Loans	27,609	29,186
OREO	31,510	32,228
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Impaired Loans	52,896	40,182
OREO	$ 0	$ 0

Fair Values of Financial Ins139

Fair Values of Financial Instruments - Summary of Estimated Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 1,434,527	$ 857,335
Securities available for sale	1,259,214	1,066,334
Securities held to maturity	33,258	39,099
Other securities	111,166	98,749
Loans held for sale	8,445	10,681
Loans	10,341,137	9,384,080
Derivative financial assets	2,291	2,942
Deposits	10,796,867	9,341,527
Derivative financial liabilities	2,605	4,121
Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	1,434,527	857,335
Securities available for sale	1,259,214	1,066,334
Securities held to maturity	33,258	39,099
Other securities	111,166	98,749
Loans held for sale	8,445	10,681
Loans	10,268,366	9,308,354
Derivative financial assets	2,291	2,942
Deposits	10,796,867	9,341,527
Short-term borrowings	209,551	423,028
Long-term borrowings	1,172,026	1,015,249
Derivative financial liabilities	2,605	4,121
Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	1,434,527	857,335
Securities available for sale	1,259,214	1,066,334
Securities held to maturity	31,178	36,319
Other securities	105,608	93,811
Loans held for sale	8,445	10,681
Loans	10,122,486	9,289,463
Derivative financial assets	2,291	2,942
Deposits	10,785,294	9,332,451
Short-term borrowings	209,551	423,028
Long-term borrowings	1,142,782	988,270
Derivative financial liabilities	2,605	4,121
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	0	0
Securities available for sale	4,465	3,532
Securities held to maturity	0	0
Other securities	0	0
Loans held for sale	0	0
Loans	0	0
Derivative financial assets	0	0
Deposits	0	0
Short-term borrowings	0	0
Long-term borrowings	0	0
Derivative financial liabilities	0	0
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	1,434,527	857,335
Securities available for sale	1,221,197	1,028,116
Securities held to maturity	28,158	33,299
Other securities	0	0
Loans held for sale	8,445	10,681
Loans	0	0
Derivative financial assets	2,291	2,942
Deposits	10,785,294	9,332,451
Short-term borrowings	209,551	423,028
Long-term borrowings	1,142,782	988,270
Derivative financial liabilities	2,605	4,121
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	0	0
Securities available for sale	33,552	34,686
Securities held to maturity	3,020	3,020
Other securities	105,608	93,811
Loans held for sale	0	0
Loans	10,122,486	9,289,463
Derivative financial assets	0	0
Deposits	0	0
Short-term borrowings	0	0
Long-term borrowings	0	0
Derivative financial liabilities	$ 0	$ 0

Variable Interest Entities - Ad

Variable Interest Entities - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2016Trust
Variable Interest Entity, Not Primary Beneficiary, Disclosures [Abstract]
Number of statutory business trusts	13
Percentage of equity shares of each trust owned by the company	100.00%

Variable Interest Entities - Su

Variable Interest Entities - Summary of Quantitative Information Related to Significant Involvement in Unconsolidated Variable Interest Entities (Detail) - Trust Preferred Securities [Member] - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Variable Interest Entity [Line Items]
Aggregate Assets	$ 240,668	$ 240,468
Aggregate Liabilities	232,583	232,492
Risk Of Loss	$ 8,085	$ 7,976

Quarterly Financial Data - Quar

Quarterly Financial Data - Quarterly Financial Data (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Interest income	$ 125,621	$ 123,137	$ 113,087	$ 108,496	$ 107,240	$ 106,309	$ 105,532	$ 104,549	$ 470,341	$ 423,630	$ 418,542
Interest expense	12,368	12,068	10,362	10,212	10,085	9,991	9,630	9,800	45,010	39,506	42,834
Net interest income	113,253	111,069	102,725	98,284	97,155	96,318	95,902	94,749	425,331	384,124	375,708
Provision for credit losses	5,819	6,988	7,667	4,035	6,322	5,182	5,716	5,354	24,509	22,574	21,937
Mortgage banking income	951	982	789	728	634	665	663	545
Securities gains (losses), net	62	1	213	4	29	111	3	12	280	155	(3,112)
Other noninterest income	15,639	18,038	16,965	15,660	17,462	17,036	18,832	17,634	70,032	73,626	80,962
Noninterest expense	62,508	62,777	64,855	58,056	58,618	57,684	57,730	57,655	248,196	231,687	239,847
Income taxes	22,472	18,846	16,378	17,879	16,864	16,217	17,145	15,304	75,575	65,530	64,998
Net income	$ 39,106	$ 41,479	$ 31,792	$ 34,706	$ 33,476	$ 35,047	$ 34,809	$ 34,627	$ 147,083	$ 137,959	$ 129,888
Average shares outstanding (000s):
Basic	76,864,000	76,219,000	71,484,000	69,497,000	69,432,000	69,391,000	69,306,000	69,208,000	73,531,992	69,334,849	67,404,254
Diluted	77,303,000	76,648,000	71,809,000	69,714,000	69,737,000	69,690,000	69,587,000	69,477,000	73,893,127	69,625,531	67,648,673
Net income per share:
Basic	$ 0.51	$ 0.54	$ 0.44	$ 0.50	$ 0.48	$ 0.50	$ 0.50	$ 0.50	$ 2	$ 1.99	$ 1.93
Diluted	0.51	0.54	0.44	0.50	0.48	0.50	0.50	0.50	1.99	1.98	1.92
Dividends per share	$ 0.33	$ 0.33	$ 0.33	$ 0.33	$ 0.33	$ 0.32	$ 0.32	$ 0.32	$ 1.32	$ 1.29	$ 1.28