United Bankshares (UBSI) 10-Q 9 May 18 2018 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2018	Apr. 30, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1
Trading Symbol	UBSI
Entity Registrant Name	UNITED BANKSHARES INC/WV
Entity Central Index Key	729,986
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		105,141,385

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Assets
Cash and due from banks	$ 178,071	$ 196,742
Interest-bearing deposits with other banks	960,308	1,468,636
Federal funds sold	791	789
Total cash and cash equivalents	1,139,170	1,666,167
Securities available for sale at estimated fair value (amortized cost-$2,119,071 at March 31, 2018 and $1,900,684 at December 31, 2017)	2,085,111	1,888,756
Securities held to maturity (estimated fair value-$20,006 at March 31, 2018 and $20,018 at December 31, 2017)	20,405	20,428
Equity securities at estimated fair value	11,160	0
Other investment securities	152,287	162,461
Loans held for sale (at fair value-$192,673 at March 31, 2018 and $263,308 at December 31, 2017)	193,915	265,955
Loans	12,998,435	13,027,337
Less: Unearned income	(14,018)	(15,916)
Loans net of unearned income	12,984,417	13,011,421
Less: Allowance for loan losses	(76,653)	(76,627)
Net loans	12,907,764	12,934,794
Bank premises and equipment	103,009	104,894
Goodwill	1,478,580	1,478,380
Accrued interest receivable	54,815	52,815
Other assets	473,486	484,309
TOTAL ASSETS	18,619,702	19,058,959
Deposits:
Noninterest-bearing	4,344,203	4,294,687
Interest-bearing	9,301,965	9,535,904
Total deposits	13,646,168	13,830,591
Borrowings:
Federal funds purchased	17,615	16,235
Securities sold under agreements to repurchase	250,771	311,352
Federal Home Loan Bank borrowings	1,060,948	1,271,531
Other long-term borrowings	233,961	242,446
Reserve for lending-related commitments	755	679
Accrued expenses and other liabilities	158,171	145,595
TOTAL LIABILITIES	15,368,389	15,818,429
Shareholders' Equity
Preferred stock, $1.00 par value; Authorized-50,000,000 shares, none issued	0	0
Common stock, $2.50 par value; Authorized-200,000,000 shares; issued-105,181,868 and 105,069,821 at March 31, 2018 and December 31, 2017, respectively, including 40,698 and 29,173 shares in treasury at March 31, 2018 and December 31, 2017, respectively	262,955	262,675
Surplus	2,130,092	2,129,077
Retained earnings	924,263	891,816
Accumulated other comprehensive loss	(64,553)	(42,025)
Treasury stock, at cost	(1,444)	(1,013)
TOTAL SHAREHOLDERS' EQUITY	3,251,313	3,240,530
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY	$ 18,619,702	$ 19,058,959

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Securities available for sale, amortized cost	$ 2,119,071	$ 1,900,684
Securities held to maturity	20,006	20,018
Loans held for sale at fair value	$ 192,673	$ 263,308
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	200,000,000	200,000,000
Common stock, shares issued	105,181,868	105,069,821
Common stock, shares in treasury	40,698	29,173

Consolidated Statements of Inco

Consolidated Statements of Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Interest income
Interest and fees on loans	$ 148,928	$ 108,942
Interest on federal funds sold and other short-term investments	4,917	2,686
Interest and dividends on securities:
Taxable	11,875	8,011
Tax-exempt	1,465	1,119
Total interest income	167,185	120,758
Interest expense
Interest on deposits	15,657	8,468
Interest on short-term borrowings	421	304
Interest on long-term borrowings	7,064	4,366
Total interest expense	23,142	13,138
Net interest income	144,043	107,620
Provision for loan losses	5,178	5,899
Net interest income after provision for loan losses	138,865	101,721
Other income
Fees from trust services	3,091	3,030
Fees from brokerage services	2,224	1,856
Fees from deposit services	8,230	7,706
Bankcard fees and merchant discounts	1,356	884
Other service charges, commissions, and fees	509	477
Income from bank-owned life insurance	1,254	1,217
Income from mortgage banking activities	14,570	675
Net investment securities (losses) gains	(485)	3,940
Other income	443	361
Total other income	31,192	20,146
Other expense
Employee compensation	40,836	24,033
Employee benefits	9,571	6,903
Net occupancy expense	9,427	6,784
Other real estate owned (OREO) expense	946	1,414
Equipment expense	3,157	1,965
Data processing expense	5,850	4,043
Bankcard processing expense	466	465
FDIC insurance expense	1,848	1,751
Other expense	18,351	15,484
Total other expense	90,452	62,842
Income before income taxes	79,605	59,025
Income taxes	17,899	20,216
Net income	$ 61,706	$ 38,809
Earnings per common share:
Basic	$ 0.59	$ 0.48
Diluted	0.59	0.48
Dividends per common share	$ 0.34	$ 0.33
Average outstanding shares:
Basic	104,859,427	80,902,368
Diluted	105,162,858	81,306,540

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 61,706	$ 38,809
Change in net unrealized gain on available-for-sale (AFS) securities, net of tax	(16,773)	3,378
Accretion of the net unrealized loss on the transfer of AFS securities to held-to-maturity (HTM) securities, net of tax	1	1
Change in defined benefit pension plan, net of tax	733	695
Comprehensive income, net of tax	$ 45,667	$ 42,883

Consolidated Statement of Chang

Consolidated Statement of Changes in Shareholders' Equity (Unaudited) - 3 months ended Mar. 31, 2018 - USD ($) $ in Thousands	Total	Common Stock [Member]	Surplus [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]
Beginning Balance at Dec. 31, 2017	$ 3,240,530	$ 262,675	$ 2,129,077	$ 891,816	$ (42,025)	$ (1,013)
Beginning Balance, shares at Dec. 31, 2017		105,069,821
Comprehensive income:
Net income	61,706	$ 0	0	61,706	0	0
Other comprehensive income, net of tax	(16,039)	0	0	0	(16,039)	0
Total comprehensive income, net of tax	45,667
Stock based compensation expense	968	0	968	0	0	0
Purchase of treasury stock	(404)	0	0	0	0	(404)
Cash dividends	(35,748)			(35,748)	0	0
Grant of restricted stock	0	$ 243	(243)	0	0	0
Grant of restricted stock, shares		97,004
Forfeiture of restricted stock	0	$ 0	27	0	0	(27)
Common stock options exercised	$ 300	$ 37	263	0	0	0
Common stock options exercised, shares	15,043	15,043
Ending Balance at Mar. 31, 2018	$ 3,251,313	$ 262,955	$ 2,130,092	924,263	(64,553)	$ (1,444)
Ending Balance, shares at Mar. 31, 2018		105,181,868
Cumulative effect of adopting Accounting Standard Update 2016-01	0			136	(136)
Reclass due to adopting Accounting Standard Update 2018-02	$ 0			$ 6,353	$ (6,353)

Consolidated Statement of Chan7

Consolidated Statement of Changes in Shareholders' Equity (Unaudited) (Parenthetical)	3 Months Ended
	Mar. 31, 2018$ / sharesshares
Cash dividends per share | $ / shares	$ 0.34
Common stock options exercised, shares	15,043
Common Stock [Member]
Purchase of treasury stock, shares	10,842
Grant of restricted stock, shares	97,004
Forfeiture of restricted stock, shares	683
Common stock options exercised, shares	15,043
Retained Earnings [Member]
Cash dividends per share | $ / shares	$ 0.34
Treasury Stock [Member]
Purchase of treasury stock, shares	10,842

Condensed Consolidated Statemen

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Cash Flows [Abstract]
NET CASH PROVIDED BY OPERATING ACTIVITIES	$ 158,484	$ 64,973
INVESTING ACTIVITIES
Proceeds from maturities and calls of securities held to maturity	1	2,886
Proceeds from sales of securities available for sale	36,850	7,376
Proceeds from maturities and calls of securities available for sale	66,067	91,422
Purchases of securities available for sale	(330,031)	(64,335)
Proceeds from sales of equity securities	159	0
Purchases of equity securities	(181)	0
Proceeds from sales and redemptions of other investment securities	9,046	7,465
Purchases of other investment securities	(3,672)	(6,227)
Purchases of bank premises and equipment	(756)	(1,680)
Proceeds from sales of bank premises and equipment	1	0
Proceeds from the sales of OREO properties	3,433	1,558
Net change in loans	32,091	(70,415)
NET CASH USED IN INVESTING ACTIVITIES	(186,992)	(31,950)
FINANCING ACTIVITIES
Cash dividends paid	(35,713)	(25,311)
Acquisition of treasury stock	(404)	0
Proceeds from exercise of stock options	300	324
Repayment of long-term Federal Home Loan Bank borrowings	(625,000)	(805,176)
Proceeds from issuance of long-term Federal Home Loan Bank borrowings	615,000	795,000
Repayment of trust preferred issuance	(9,374)	0
Changes in:
Deposits	(184,097)	265,509
Federal funds purchased, securities sold under agreements to repurchase and other short-term borrowings	(259,201)	(30,568)
NET CASH (USED IN) PROVIDED BY FINANCING ACTIVITIES	(498,489)	199,778
(Decrease) Increase in cash and cash equivalents	(526,997)	232,801
Cash and cash equivalents at beginning of year	1,666,167	1,434,527
Cash and cash equivalents at end of period	1,139,170	1,667,328
Noncash investing activities:
Transfers of loans to OREO	$ 527	$ 951

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	1. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation The accompanying unaudited consolidated interim financial statements of United Bankshares, Inc. and Subsidiaries (“United” or “the Company”) have been prepared in accordance with accounting principles for interim financial information generally accepted in the United States (GAAP) and with the instructions for Form 10-Q S-X. 10-K. The accompanying consolidated interim financial statements include the accounts of United and its wholly owned subsidiaries. United operates in two business segments: community banking and mortgage banking. All significant intercompany accounts and transactions have been eliminated in the consolidated financial statements. Information is presented in these notes to the unaudited consolidated interim financial statements with dollars expressed in thousands, except per share or unless otherwise noted. New Accounting Standards In February 2018, the FASB issued ASU No. 2018-03, “Technical Corrections and Improvements to Financial Instruments – Overall (Subtopic 825-10): 2018-03 No. 2018-03 No. 2018-03 In February 2018, the FASB issued ASU No. 2018-02, “Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income,” to help organizations address certain stranded income tax effects in accumulated other comprehensive income (AOCI) resulting from the Tax Cuts and Jobs Act (the “Tax Act”). This ASU provides financial statement preparers with an option to reclassify stranded tax effects within AOCI to retained earnings in each period in which the effect of the change in the U.S. federal corporate income tax rate in the Tax Act (or portion thereof) is recorded. The amendments are effective for all organizations for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Early adoption is permitted. Organizations should apply the proposed amendments either in the period of adoption or retrospectively to each period (or periods) in which the effect of the change in the U.S. federal corporate income tax rate in the Tax Act is recognized. United adopted ASU No. 2018-02 In August 2017, the FASB issued ASU No. 2017-12, No. 2017-12 No. 2017-12 In July 2017, the FASB issued ASU No. 2017-11, No. 2017-11 No. 2017-11 In May 2017, the FASB issued ASU No. 2017-09, non-substantive No. 2017-09 No. 2017-09 In March 2017, the FASB issued ASU 2017-07, 2017-07 2017-07 2017-07 In January 2017, the FASB issued ASU 2017-04, 2017-04 2017-04 In January 2017, the FASB issued ASU 2017-01, 2017-01 2017-01 In August 2016, the FASB issued ASU 2016-15, 2016-15 2016-15 2016-15 In June 2016, the FASB issued ASU 2016-13, 2016-13 available-for-sale 2016-13 2016-13 In March 2016, the FASB issued ASU 2016-09, 2016-09 2016-09 2016-09 tax-related 2016-09 In February 2016, the FASB issued ASU 2016-02, 2016-02 2016-02 right-of-use 2016-02 2016-02 In January 2016, the FASB issued ASU 2016-01, 2016-01 2016-01 available-for-sale 2016-01 In May 2014, the FASB issued ASU 2014-09, 2014-09 2014-09 2014-09 2014-09 2014-09 Descriptions of our revenue-generating activities that are within the scope of ASC topic 606, which are presented in our Consolidated Statements of Income as components of Other Income are discussed below. There are no significant judgements relating to the amount and timing of revenue recognition for those revenue streams under the scope of ASC topic 606. Fees from Trust Services Revenue from trust services primarily is comprised of fees earned from the management and administration of trusts and other customer assets. Trust services include custody of assets, investment management, escrow services, and similar fiduciary activities. The Company’s performance obligation is generally satisfied over time and the resulting fees are recognized monthly, based upon the month-end Fees from Brokerage Services Revenue from brokerage services are recorded as the income is earned at the time the related service is performed. In return for such services, the Company charges a commission for the sales of various securities products primarily consisting of investment company shares, annuity products, and corporate debt and equity securities, for its selling and administrative efforts. For account supervision, advisory, and administrative services, revenue is recognized over a period of time as earned based on customer account balances and activity. Fees from Deposit Services Service charges on deposit accounts consist of account analysis fees (i.e., net fees earned on analyzed business and public checking accounts), monthly service fees, check orders, ATM activity fees, debit card fees, and other deposit account related fees. Revenue is recognized when our performance obligation is completed which is generally monthly for account maintenance services or when a transaction has been completed (ATM or debit card activity). Bankcard Fees and Merchant Discounts Bankcard fees and merchant discounts are primarily comprised of credit card income and merchant services income. Credit card income is primarily comprised of interchange fees earned whenever the Company’s credit cards are processed through card payment networks such as Visa. Merchant services income mainly represents fees charged to merchants to process their credit card transactions. The Company’s performance obligation for bankcard fees and exchange are largely satisfied, and related revenue recognized at the time services are rendered. Payment is typically received immediately or in the following month.

Mergers and Acquisitions

Mergers and Acquisitions	3 Months Ended
	Mar. 31, 2018
Business Combinations [Abstract]
Mergers and Acquisitions	2. MERGERS AND ACQUISITIONS Cardinal Financial Corporation On April 21, 2017 (Cardinal Acquisition Date), United acquired 100% of the outstanding common stock of Cardinal Financial Corporation (Cardinal), headquartered in Tysons Corner, Virginia. The acquisition of Cardinal expands United’s existing footprint in the Washington, D.C. Metropolitan Statistical Area. At consummation, Cardinal had assets of $4,136,008, loans of $3,313,033 and deposits of $3,344,740. Cardinal also operated George Mason Mortgage, LLC (George Mason), a residential mortgage lending company based in Fairfax, Virginia with offices located in Virginia, Maryland, North Carolina, South Carolina and the District of Columbia. As a result of the merger, George Mason became an indirectly-owned subsidiary of United. The merger was accounted for under the acquisition method of accounting. The results of operations of Cardinal are included in the consolidated results of operations from the Cardinal Acquisition Date. The aggregate purchase price was approximately $975,254, including common stock valued at $972,499, stock options assumed valued at $2,741, and cash paid for fractional shares of $14. The number of shares issued in the transaction was 23,690,589, which were valued based on the closing market price of $41.05 for United’s common shares on April 21, 2017. The preliminary purchase price has been allocated to the identifiable tangible and intangible assets resulting in preliminary additions to goodwill, core deposit intangibles and the George Mason trade name intangible of $613,486, $28,724 and $1,080, respectively. The core deposit intangibles are expected to be amortized over ten years. The George Mason trade name provides a source of market recognition to attract potential clients and retain existing relationships. United believes the George Mason trade name provides a competitive advantage and is likely going to be used into perpetuity and thus will not be subject to amortization, but rather be evaluated for impairment. 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 Cardinal 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 Cardinal. As a result of the merger, United recorded preliminary fair value discounts of $144,434 on the loans acquired, $2,281 on leases and $8,738 on trust preferred issuances, respectively, and premiums of $4,408 on land acquired, $5,072 on interest-bearing deposits and $10,740 on long-term FHLB advances, respectively. The remaining discount and premium amounts are being accreted or amortized on an accelerated or straight-line basis over each asset’s or liability’s estimated remaining life at the time of acquisition except for loans and land. The discount on loans will be accreted into income based on the effective yield method. The premium on land will not be amortized. At March 31, 2018, the discounts on leases and trust preferred issuances had an average estimated remaining life of 5.5 years and 16.47 years, respectively, and the premiums on the interest-bearing deposits and the FHLB advances each had an average estimated remaining life of 4.5 years and 4.31 years, respectively. United assumed approximately $1,825 of liabilities to provide severance benefits to terminated employees of Cardinal, which has no remaining balance as of March 31, 2018. The estimated fair values of the acquired assets and assumed liabilities, including identifiable intangible assets and goodwill are preliminary as of March 31, 2018 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 measurement period 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 value 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 Cardinal’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 310-30 310-20 In conjunction with the Cardinal merger, the acquired loan portfolio was accounted for at fair value as follows: April 21, 2017 Contractually required principal and interest at acquisition $ 4,211,734 Contractual cash flows not expected to be collected (56,176 ) Expected cash flows at acquisition 4,155,558 Interest component of expected cash flows (986,959 ) Basis in acquired loans at acquisition – estimated fair value $ 3,168,599 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 $132,837, $108,275, and $86,696, respectively. The consideration paid for Cardinal’s common equity and the preliminary amounts of acquired identifiable assets and liabilities assumed as of the Cardinal Acquisition Date were as follows: Purchase price: Value of common shares issued (23,690,589 shares) $ 972,499 Fair value of stock options assumed 2,741 Cash for fractional shares 14 Total purchase price 975,254 Identifiable assets: Cash and cash equivalents 44,545 Investment securities 395,829 Loans held for sale 271,301 Loans 3,168,599 Premises and equipment 24,208 Core deposit intangibles 28,724 George Mason trade name intangible 1,080 Other assets 135,383 Total identifiable assets $ 4,069,669 Identifiable liabilities: Deposits $ 3,349,812 Short-term borrowings 96,215 Long-term borrowings 220,119 Unfavorable lease liability 2,281 Other liabilities 39,474 Total identifiable liabilities 3,707,901 Preliminary fair value of net assets acquired including identifiable intangible assets 361,768 Preliminary resulting goodwill $ 613,486 The operating results of United for the three months ended March 31, 2018 include operating results of acquired assets and assumed liabilities subsequent to the Cardinal Acquisition Date. The operations of United’s metropolitan Washington D.C. geographic area, which primarily includes the acquired operations of Cardinal, provided $340,632 in total revenues, which represents net interest income plus other income, and $157,852 in net income from the period from the Cardinal Acquisition Date to March 31, 2018. Cardinal’s results of operations prior to the Cardinal 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 three months ended March 31, 2017, as if the Cardinal merger had occurred on January 1, 2017. These results combine the historical results of Cardinal into United’s consolidated statement of income and, while certain adjustments were made for the estimated impact of certain fair valuation adjustments and other acquisition-related activity, 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 Cardinal’s provision for credit losses for the three months ended March 31, 2017 that may not have been necessary had the acquired loans been recorded at fair value as of the beginning of 2017. 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 Three Months Ended March 31, 2017 Total Revenues (1) $ 191,052 Net Income 54,710 (1) Represents net interest income plus other income

Investment Securities

Investment Securities	3 Months Ended
	Mar. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Investment Securities	3. INVESTMENT SECURITIES Securities Available for Sale Securities held for indefinite periods of time are classified as available for sale and carried at estimated fair value. The amortized cost and estimated fair values of securities available for sale are summarized as follows. March 31, 2018 Gross Gross Estimated Cumulative Amortized Unrealized Unrealized Fair OTTI in Cost Gains Losses Value AOCI (1) U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 163,718 $ 237 $ 849 $ 163,106 $ 0 State and political subdivisions 297,481 1,300 5,069 293,712 0 Residential mortgage-backed securities Agency 934,557 993 20,003 915,547 0 Non-agency 4,665 501 0 5,166 86 Commercial mortgage-backed securities Agency 485,851 281 9,353 476,779 0 Asset-backed securities 146,774 285 475 146,584 0 Trust preferred collateralized debt obligations 9,192 0 1,128 8,064 2,586 Single issue trust preferred securities 13,433 327 614 13,146 0 Other corporate securities 63,400 337 730 63,007 0 Total $ 2,119,071 $ 4,261 $ 38,221 $ 2,085,111 $ 2,672 December 31, 2017 Gross Gross Estimated Cumulative Amortized Unrealized Unrealized Fair OTTI in Cost Gains Losses Value AOCI (1) U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 114,735 $ 385 $ 362 $ 114,758 $ 0 State and political subdivisions 303,101 3,197 2,429 303,869 0 Residential mortgage-backed securities Agency 821,857 2,096 9,360 814,593 0 Non-agency 4,969 543 0 5,512 86 Commercial mortgage-backed securities Agency 457,107 1,059 3,309 454,857 0 Asset-backed securities 109,829 148 7 109,970 0 Trust preferred collateralized debt obligations 37,856 542 4,129 34,269 20,770 Single issue trust preferred securities 13,417 368 1,225 12,560 0 Other corporate securities 28,101 407 18 28,490 0 Marketable equity securities 9,712 179 13 9,878 0 Total $ 1,900,684 $ 8,924 $ 20,852 $ 1,888,756 $ 20,856 (1) Non-credit before-tax. The following is a summary of securities available-for-sale Less than 12 months 12 months or longer Fair Unrealized Fair Unrealized Value Losses Value Losses March 31, 2018 U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 65,919 $ 722 $ 22,751 $ 127 State and political subdivisions 137,221 1,584 55,674 3,485 Residential mortgage-backed securities Agency 682,082 13,128 172,052 6,875 Non-agency 0 0 0 0 Commercial mortgage-backed securities Agency 391,087 7,961 60,595 1,392 Asset-backed securities 56,833 475 0 0 Trust preferred collateralized debt obligations 0 0 5,049 1,128 Single issue trust preferred securities 0 0 5,100 614 Other corporate securities 41,634 730 0 0 Total $ 1,374,776 $ 24,600 $ 321,221 $ 13,621 Less than 12 months 12 months or longer Fair Unrealized Fair Unrealized Value Losses Value Losses December 31, 2017 U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 36,678 $ 230 $ 22,920 $ 132 State and political subdivisions 82,896 566 59,432 1,863 Residential mortgage-backed securities Agency 460,414 4,621 182,482 4,739 Non-agency 0 0 0 0 Commercial mortgage-backed securities Agency 282,858 2,386 70,763 923 Asset-backed securities 27,931 7 0 0 Trust preferred collateralized debt obligations 0 0 28,629 4,129 Single issue trust preferred securities 0 0 4,485 1,225 Other corporate securities 6,975 18 0 0 Marketable equity securities 0 0 363 13 Total $ 897,752 $ 7,828 $ 369,074 $ 13,024 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 those 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 of United and its subsidiaries. Three Months Ended March 31 2018 2017 Proceeds from sales and calls $ 99,703 $ 98,798 Gross realized gains 1,163 214 Gross realized losses 1,312 0 At March 31, 2018, gross unrealized losses on available for sale securities were $38,221 on 635 securities of a total portfolio of 870 available for sale securities. Securities in an unrealized loss position at March 31, 2018 consisted primarily of trust preferred collateralized debt obligations (Trup Cdos), single issue trust preferred securities, state and political subdivision securities, and agency commercial and residential mortgage-backed securities. The Trup Cdos and the single issue trust preferred securities relate to securities of financial institutions. The state and political subdivisions securities relate to securities issued by various municipalities. The agency commercial and residential mortgage-backed securities relate to commercial and 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 $297,481 at March 31, 2018. As of March 31, 2018, approximately 77% 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 March 31, 2018. 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 March 31, 2018. 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-backed securities was $1,420,408 at March 31, 2018. Of the $1,420,408 amount, $485,851 was related to agency commercial mortgage-backed securities and $934,557 was related to agency residential mortgage-backed securities. Each of the agency mortgage-backed 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 March 31, 2018. Non-agency United’s non-agency non-agency non-agency non-agency 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 first quarter of 2018, it was determined that none of the single issue trust preferred securities were other-than-temporarily impaired. All single issue trust preferred securities are currently receiving interest payments. The amortized cost of available for sale single issue trust preferred securities as of March 31, 2018 consisted of $7,719 in investment grade bonds and $5,714 in unrated bonds. The investment grade bonds were rated either Baa3 or BBB-. Trust preferred collateralized debt obligations (Trup Cdos) The total amortized cost balance of United’s Trup Cdo portfolio was $9,192 as of March 31, 2018. Compared to the prior quarter, the total amortized cost balance declined by $28,664 due mainly to the sale of seven securities totaling $25,315, and the redemption of one security at par in the amount of $3,300. Of the remaining $9,192, one additional security totaling $3,016 was redeemed at par on April 3, 2018. For any securities in an unrealized loss position, 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 March 31, 2018, the Company has determined that it does not intend to sell any Trup Cdo 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. 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 March 31, 2018 is other-than-temporarily impaired. Corporate securities As of March 31, 2018, United’s Corporate securities portfolio had a total amortized cost balance of $63,400. The majority of the portfolio consisted of debt issuances of corporations representing a variety of industries, including financial institutions. Of the $63,400, 67% was investment grade rated and 33% was unrated. For corporate 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 corporate securities were other-than-temporarily impaired at March 31, 2018. 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. Three Months Ended March 31 2018 2017 Balance of cumulative credit losses at beginning of period $ 18,060 $ 22,162 Additions for credit losses recognized in earnings during the period: Additional credit losses on securities for which OTTI was previously recognized 0 0 Reductions for securities sold or paid off during the period (14,861 ) 0 Balance of cumulative credit losses at end of period $ 3,199 $ 22,162 The amortized cost and estimated fair value of securities available for sale at March 31, 2018 and December 31, 2017 by contractual maturity are shown as follows. Expected maturities may differ from contractual maturities because the issuers may have the right to call or prepay obligations without penalties. March 31, 2018 December 31, 2017 Estimated Estimated Amortized Fair Amortized Fair Cost Value Cost Value Due in one year or less $ 52,863 $ 52,753 $ 50,311 $ 50,212 Due after one year through five years 476,361 471,410 386,039 384,585 Due after five years through ten years 445,861 436,757 400,129 398,208 Due after ten years 1,143,986 1,124,191 1,054,493 1,045,873 Marketable equity securities 0 0 9,712 9,878 Total $ 2,119,071 $ 2,085,111 $ 1,900,684 $ 1,888,756 Securities Held to Maturity The amortized cost and estimated fair values of securities held to maturity are summarized as follows: March 31, 2018 Gross Gross Estimated Amortized Unrealized Unrealized Fair Cost Gains Losses Value U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 5,160 $ 241 $ 0 $ 5,401 State and political subdivisions 5,797 9 0 5,806 Residential mortgage-backed securities Agency 23 3 0 26 Single issue trust preferred securities 9,405 0 652 8,753 Other corporate securities 20 0 0 20 Total $ 20,405 $ 253 $ 652 $ 20,006 December 31, 2017 Gross Gross Estimated Amortized Unrealized Unrealized Fair Cost Gains Losses Value U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 5,187 $ 308 $ 0 $ 5,495 State and political subdivisions 5,797 10 0 5,807 Residential mortgage-backed securities Agency 23 3 0 26 Single issue trust preferred securities 9,401 0 731 8,670 Other corporate securities 20 0 0 20 Total $ 20,428 $ 321 $ 731 $ 20,018 Even though the market value of the held-to-maturity held-to-maturity held-to-maturity There were no gross realized gains or losses on calls and sales of held to maturity securities included in earnings for the first quarter of 2018 and 2017. The amortized cost and estimated fair value of debt securities held to maturity at March 31, 2018 and December 31, 2017 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. March 31, 2018 December 31, 2017 Estimated Estimated Amortized Fair Amortized Fair Cost Value Cost Value Due in one year or less $ 0 $ 0 $ 0 $ 0 Due after one year through five years 9,318 9,566 9,344 9,660 Due after five years through ten years 8,091 7,618 5,663 5,343 Due after ten years 2,996 2,822 5,421 5,015 Total $ 20,405 $ 20,006 $ 20,428 $ 20,018 Equity securities at fair value 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 fair value of United’s equity securities was $11,160 at March 31, 2018. Prior to March 31, 2018 and the adoption of ASU 2016-01, equity securities were included in available for sale securities. Three Months March 31, 2018 Net gains (losses) recognized during the period $ (36 ) Net gains (losses) recognized during the period on equity securities sold 2 Unrealized gains recognized during the period on equity securities still held at period end 39 Unrealized losses recognized during the period on equity securities still held at period end 77 Other investment securities During the first quarter of 2018, United evaluated all of its cost method investments to determine if certain events or changes in circumstances during the first quarter of 2018 had a significant adverse effect on the fair value of any of its cost method securities. United determined that there was one security that experienced an adverse event during the first quarter. Total impairment of $300 was recognized on this security. With the exception of this one security, there were no other events or changes in circumstances during the first quarter which would have an adverse effect on the fair value of its cost method securities. 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 $1,612,649 and $1,403,565 at March 31, 2018 and December 31, 2017, respectively.

Loans

Loans	3 Months Ended
	Mar. 31, 2018
Receivables [Abstract]
Loans	4. LOANS Major classes of loans are as follows: March 31, 2018 December 31, Commercial, financial and agricultural: Owner-occupied commercial real estate $ 1,366,980 $ 1,361,629 Nonowner-occupied commercial real estate 4,426,776 4,451,298 Other commercial loans 1,952,322 1,998,979 Total commercial, financial & agricultural 7,746,078 7,811,906 Residential real estate 3,065,990 2,996,171 Construction & land development 1,433,125 1,504,907 Consumer: Bankcard 9,372 10,314 Other consumer 743,870 704,039 Total gross loans $ 12,998,435 $ 13,027,337 The table above does not include loans held for sale of $193,915 and $265,955 at March 31, 2018 and December 31, 2017, 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 previously acquired impaired loans with a recorded investment of $189,675 or 1.46% of total gross loans at March 31, 2018 and $210,521 or 1.62% of total gross loans at December 31, 2017. The contractual principal in these acquired impaired loans was $253,827 and $285,964 at March 31, 2018 and December 31, 2017, 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 first three months of 2018 follows: Accretable yield at the beginning of the period $ 39,098 Accretion (including cash recoveries) (4,053 ) Additions 0 Net reclassifications to accretable from non-accretable 4,493 Disposals (including maturities, foreclosures, and charge-offs) (1,948 ) Accretable yield at the end of the period $ 37,590 United’s subsidiary bank has made loans to the directors and officers of United and its subsidiaries, and to their affiliates. The aggregate dollar amount of these loans was $35,777 and $36,360 at March 31, 2018 and December 31, 2017, respectively.

Credit Quality

Credit Quality	3 Months Ended
	Mar. 31, 2018
Text Block [Abstract]
Credit Quality	5. 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 March 31, 2018, United had TDRs of $48,271 as compared to $50,129 as of December 31, 2017. Of the $48,271 aggregate balance of TDRs at March 31, 2018, $33,592 was on nonaccrual and $85 were 30 to 89 days past due. Of the $50,129 aggregate balance of TDRs at December 31, 2017, $30,868 was on nonaccrual, $95 were 90 days or more past due and $1,254 were 30 to 89 days past due. All these amounts are included in the appropriate categories in the “Age Analysis of Past Due Loans” table on a subsequent page. As of March 31, 2018, there were no commitments to lend additional funds to debtors owing receivables whose terms have been modified in TDRs. At March 31, 2018, United had restructured loans in the amount of $1,760 that were modified by a reduction in the interest rate, $1,891 that were modified by a combination of a reduction in the interest rate and the principal and $44,620 that were modified by a change in terms. A loan acquired and accounted for under ASC topic 310-30 No loans were restructured during the first quarter of 2018. The following table sets forth United’s troubled debt restructurings that were restructured during the three months ended March 31, 2017, segregated by class of loans. Troubled Debt Restructurings For the Three Months Ended March 31, 2017 Number of Pre- Modification Post- Commercial real estate: Owner-occupied 0 $ 0 $ 0 Nonowner-occupied 0 0 0 Other commercial 4 2,752 2,741 Residential real estate 0 0 0 Construction & land development 1 1,456 1,450 Consumer: Bankcard 0 0 0 Other consumer 0 0 0 Total 5 $ 4,208 $ 4,191 During the first quarter of 2017, $4,191 of restructured loans were modified by a change in terms. In some instances, the post-modification balance on the restructured loans is larger than the pre-modification No loans restructured during the twelve-month periods ended March 31, 2018 and 2017 subsequently defaulted, resulting in a principal charge-off 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 March 31, 2018 30-89 Days Past Due 90 Days or more Past Due Total Past Due Current & Total Financing Receivables Recorded Investment >90 Days & Accruing Commercial real estate: Owner-occupied $ 13,303 $ 18,862 $ 32,165 $ 1,334,815 $ 1,366,980 $ 847 Nonowner-occupied 7,248 19,294 26,542 4,400,234 4,426,776 139 Other commercial 35,269 59,412 94,681 1,857,641 1,952,322 962 Residential real estate 30,344 25,641 55,985 3,010,005 3,065,990 6,027 Construction & land development 3,138 18,403 21,541 1,411,584 1,433,125 152 Consumer: Bankcard 185 121 306 9,066 9,372 121 Other consumer 6,417 1,196 7,613 736,257 743,870 917 Total $ 95,904 $ 142,929 $ 238,833 $ 12,759,602 $ 12,998,435 $ 9,165 (1) Other includes loans with a recorded investment of $189,675 acquired and accounted for under ASC topic 310-30 Age Analysis of Past Due Loans As of December 31, 2017 30-89 Past Due 90 Days or more Past Due Total Past Current & Total Financing Recorded & Accruing Commercial real estate: Owner-occupied $ 7,968 $ 13,663 $ 21,631 $ 1,339,998 $ 1,361,629 $ 458 Nonowner-occupied 10,398 20,448 30,846 4,420,452 4,451,298 634 Other commercial 11,533 68,476 80,009 1,918,970 1,998,979 940 Residential real estate 35,300 28,637 63,937 2,932,234 2,996,171 6,519 Construction & land development 1,615 17,190 18,805 1,486,102 1,504,907 385 Consumer: Bankcard 449 186 635 9,679 10,314 186 Other consumer 9,288 968 10,256 693,783 704,039 775 Total $ 76,551 $ 149,568 $ 226,119 $ 12,801,218 $ 13,027,337 $ 9,897 (1) Other includes loans with a recorded investment of $210,521 acquired and accounted for under ASC topic 310-30 The following table sets forth United’s nonaccrual loans, segregated by class of loans: Loans on Nonaccrual Status March 31, 2018 December 31, 2017 Commercial real estate: Owner-occupied $ 18,015 $ 13,205 Nonowner-occupied 19,155 19,814 Other commercial 58,450 67,536 Residential real estate 19,614 22,118 Construction & land development 18,251 16,805 Consumer: Bankcard 0 0 Other consumer 279 193 Total $ 133,764 $ 139,671 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 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 The following tables set forth United’s credit quality indicators information, by class of loans: Credit Quality Indicators Corporate Credit Exposure As of March 31, 2018 Commercial Real Estate Other Construction &Land Owner- Nonowner- Grade: Pass $ 1,291,287 $ 4,250,743 $ 1,820,513 $ 1,349,638 Special mention 14,448 72,997 51,165 3,779 Substandard 61,245 103,036 77,848 79,708 Doubtful 0 0 2,796 0 Total $ 1,366,980 $ 4,426,776 $ 1,952,322 $ 1,433,125 As of December 31, 2017 Commercial Real Estate Other Construction & Land Development Owner- Nonowner- Grade: Pass $ 1,276,088 $ 4,312,985 $ 1,848,868 $ 1,413,706 Special mention 20,165 57,618 55,564 5,196 Substandard 65,376 80,695 90,625 86,005 Doubtful 0 0 3,922 0 Total $ 1,361,629 $ 4,451,298 $ 1,998,979 $ 1,504,907 Credit Quality Indicators Consumer Credit Exposure As of March 31, 2018 Residential Bankcard Other Grade: Pass $ 3,011,824 $ 9,066 $ 736,184 Special mention 20,738 185 6,460 Substandard 33,428 121 1,226 Doubtful 0 0 0 Total $ 3,065,990 $ 9,372 $ 743,870 As of December 31, 2017 Residential Bankcard Other Grade: Pass $ 2,945,266 $ 9,679 $ 693,727 Special mention 18,025 449 9,334 Substandard 32,880 186 978 Doubtful 0 0 0 Total $ 2,996,171 $ 10,314 $ 704,039 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 days or more) 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 sets forth United’s impaired loans information, by class of loans: Impaired Loans March 31, 2018 December 31, 2017 Recorded Unpaid Related Recorded Unpaid Related With no related allowance recorded: Commercial real estate: Owner-occupied $ 75,776 $ 75,941 $ 0 $ 78,117 $ 78,419 $ 0 Nonowner-occupied 117,589 117,648 0 134,136 134,195 0 Other commercial 52,394 54,953 0 46,993 49,552 0 Residential real estate 24,125 24,787 0 26,751 28,202 0 Construction & land development 48,320 53,084 0 52,279 59,691 0 Consumer: Bankcard 0 0 0 0 0 0 Other consumer 42 42 0 15 15 0 With an allowance recorded: Commercial real estate: Owner-occupied $ 5,873 $ 5,873 $ 1,075 $ 9,132 $ 9,132 $ 2,251 Nonowner-occupied 8,543 8,543 1,471 7,797 7,797 1,592 Other commercial 48,082 55,905 16,180 60,512 70,396 16,721 Residential real estate 11,887 13,438 1,742 9,813 10,418 1,552 Construction & land development 2,015 4,664 217 1,383 1,383 229 Consumer: Bankcard 0 0 0 0 0 0 Other consumer 0 0 0 0 0 0 Total: Commercial real estate: Owner-occupied $ 81,649 $ 81,814 $ 1,075 $ 87,249 $ 87,551 $ 2,251 Nonowner-occupied 126,132 126,191 1,471 141,933 141,992 1,592 Other commercial 100,476 110,858 16,180 107,505 119,948 16,721 Residential real estate 36,012 38,225 1,742 36,564 38,620 1,552 Construction & land development 50,335 57,748 217 53,662 61,074 229 Consumer: Bankcard 0 0 0 0 0 0 Other consumer 42 42 0 15 15 0 Impaired Loans For the Three Months Ended March 31, 2018 March 31, 2017 Average Interest Average Interest With no related allowance recorded: Commercial real estate: Owner-occupied $ 76,947 $ 377 $ 55,857 $ 421 Nonowner-occupied 125,863 120 82,528 117 Other commercial 49,693 206 49,286 220 Residential real estate 25,437 83 21,814 41 Construction & land development 50,300 103 35,949 76 Consumer: Bankcard 0 0 0 0 Other consumer 28 0 36 0 With an allowance recorded: Commercial real estate: Owner-occupied $ 7,502 $ 25 $ 7,663 $ 137 Nonowner-occupied 8,170 59 16,096 83 Other commercial 54,297 19 58,824 370 Residential real estate 10,850 0 13,113 8 Construction & land development 1,699 20 4,161 21 Consumer: Bankcard 0 0 0 0 Other consumer 0 0 0 0 Total: Commercial real estate: Owner-occupied $ 84,449 $ 402 $ 63,520 $ 558 Nonowner-occupied 134,033 179 98,624 200 Other commercial 103,990 225 108,110 590 Residential real estate 36,287 83 34,927 49 Construction & land development 51,999 123 40,110 97 Consumer: Bankcard 0 0 0 0 Other consumer 28 0 36 0 At March 31, 2018 and December 31, 2017, other real estate owned (“OREO”) included in other assets in the Consolidated Balance Sheets was $22,778 and $24,348, respectively. OREO consists of real estate acquired in foreclosure or other settlement of loans. Such assets are carried at the lower of the investment in the assets or the fair value of the assets less estimated selling costs. Any adjustment to the fair value at the date of transfer is charged against the allowance for loan losses. Any subsequent valuation adjustments as well as any costs relating to operating, holding or disposing of the property are recorded in other expense in the period incurred. At March 31, 2018 and December 31, 2017, the recorded investment of consumer mortgage loans secured by residential real estate properties for which formal foreclosure proceedings are in process was $377 and $873, respectively.

Allowance for Credit Losses

Allowance for Credit Losses	3 Months Ended
	Mar. 31, 2018
Receivables [Abstract]
Allowance for Credit Losses	6. 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 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. Loans deemed to be uncollectible are charged against the allowance for loan losses, while recoveries of previously charged-off charge-off charge-off charged-off charge-off For consumer loans, closed-end open-end charged-off. one-to-four open-end closed-end high-loan-to-value charges-off charged-off charged-off 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 payments 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). For the three months ended March 31, 2018 and 2017, the re-estimation 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 $755 and $679 at March 31, 2018 and December 31, 2017, 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 loan losses, by portfolio segment, for the periods indicated is summarized as follows: Allowance for Loan Losses and Carrying Amount of Loans For the Three Months Ended March 31, 2018 Commercial Real Estate Construction Allowance for Owner- Nonowner- Other Residential & Land Consumer Estimated Total Allowance for Loan Losses: Beginning balance $ 5,401 $ 6,369 $ 45,189 $ 9,927 $ 7,187 $ 2,481 $ 73 $ 76,627 Charge-offs 1,015 0 2,868 910 460 605 0 5,858 Recoveries 55 136 106 264 2 143 0 706 Provision (722 ) 269 4,490 972 (300 ) 372 97 5,178 Ending balance $ 3,719 $ 6,774 $ 46,917 $ 10,253 $ 6,429 $ 2,391 $ 170 $ 76,653 Ending Balance: individually evaluated for impairment $ 1,075 $ 1,471 $ 16,180 $ 1,742 $ 217 $ 0 $ 0 $ 20,685 Ending Balance: collectively evaluated for impairment $ 2,644 $ 5,303 $ 30,737 $ 8,511 $ 6,212 $ 2,391 $ 170 $ 55,968 Ending Balance: loans acquired with deteriorated credit quality $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 Financing receivables: Ending balance $ 1,366,980 $ 4,426,776 $ 1,952,322 $ 3,065,990 $ 1,433,125 $ 753,242 $ 0 $ 12,998,435 Ending Balance: individually evaluated for impairment $ 33,438 $ 22,868 $ 71,478 $ 13,856 $ 16,909 $ 0 $ 0 $ 158,549 Ending Balance: collectively evaluated for impairment $ 1,301,725 $ 4,310,587 $ 1,853,603 $ 3,039,123 $ 1,391,948 $ 753,225 $ 0 $ 12,650,211 Ending Balance: loans acquired with deteriorated credit quality $ 31,817 $ 93,321 $ 27,241 $ 13,011 $ 24,268 $ 17 $ 0 $ 189,675 Allowance for Loan Losses and Carrying Amount of Loans For the Year Ended December 31, 2017 Commercial Real Estate Construction Allowance for Owner- occupied Nonowner- occupied Other Commercial Residential Real Estate & Land Development Consumer Estimated Imprecision Total Allowance for Loan Losses: Beginning balance $ 5,273 $ 6,883 $ 33,087 $ 13,770 $ 10,606 $ 2,805 $ 347 $ 72,771 Charge-offs 2,246 296 21,189 2,973 3,337 2,822 0 32,863 Recoveries 2,599 244 3,395 601 726 748 0 8,313 Provision (225 ) (462 ) 29,896 (1,471 ) (808 ) 1,750 (274 ) 28,406 Ending balance $ 5,401 $ 6,369 $ 45,189 $ 9,927 $ 7,187 $ 2,481 $ 73 $ 76,627 Ending Balance: individually evaluated for impairment $ 2,251 $ 1,592 $ 16,721 $ 1,552 $ 229 $ 0 $ 0 $ 22,345 Ending Balance: collectively evaluated for impairment $ 3,150 $ 4,777 $ 28,468 $ 8,375 $ 6,958 $ 2,481 $ 73 $ 54,282 Ending Balance: loans acquired with deteriorated credit quality $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 Financing receivables: Ending balance $ 1,361,629 $ 4,451,298 $ 1,998,979 $ 2,996,171 $ 1,504,907 $ 714,353 $ 0 $ 13,027,337 Ending Balance: individually evaluated for impairment $ 36,721 $ 21,851 $ 78,715 $ 14,316 $ 16,921 $ 0 $ 0 $ 168,524 Ending Balance: collectively evaluated for impairment $ 1,291,379 $ 4,320,997 $ 1,892,706 $ 2,967,666 $ 1,461,206 $ 714,338 $ 0 $ 12,648,292 Ending Balance: loans acquired with deteriorated credit quality $ 33,529 $ 108,450 $ 27,558 $ 14,189 $ 26,780 $ 15 $ 0 $ 210,521

Intangible Assets

Intangible Assets	3 Months Ended
	Mar. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Assets	7. INTANGIBLE ASSETS The following is a summary of intangible assets subject to amortization and those not subject to amortization: March 31, 2018 Community Banking Mortgage Banking Total Gross Carrying Amount Accumulated Amortization Gross Carrying Amount Accumulated Gross Accumulated Amortized intangible assets: Core deposit intangible assets $ 98,359 ($ 56,463 ) $ 0 ($ 0 ) $ 98,359 ($ 56,463 ) Non-amortized George Mason trade name $ 0 $ 1,080 $ 1,080 Goodwill not subject to amortization $ 1,473,265 $ 5,315 $ 1,478,580 December 31, 2017 Community Banking Mortgage Banking Total Gross Carrying Amount Accumulated Amortization Gross Carrying Amount Accumulated Amortization Gross Carrying Amount Accumulated Amortization Amortized intangible assets: Core deposit intangible assets $ 98,359 ($ 54,453 ) $ 0 $ 0 $ 98,359 ($ 54,453 ) Non-amortized George Mason trade name $ 0 $ 1,080 $ 1,080 Goodwill not subject to amortization $ 1,473,265 $ 5,115 $ 1,478,380 The following table provides a reconciliation of goodwill: Community Banking Mortgage Banking Total Goodwill at December 31, 2017 $ 1,473,265 $ 5,115 $ 1,478,380 Preliminary addition to goodwill from Cardinal acquisition 0 200 200 Goodwill at March 31, 2018 $ 1,473,265 $ 5,315 $ 1,478,580 United incurred amortization expense of $2,010 and $1,048 for the quarters ended March 31, 2018 and 2017, respectively. The following table sets forth the anticipated amortization expense for intangible assets for the years subsequent to 2017: Year Amount 2018 $ 8,039 2019 7,016 2020 6,309 2021 5,369 2022 and thereafter 17,173

Short-Term Borrowings

Short-Term Borrowings	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Short-Term Borrowings	8. SHORT-TERM BORROWINGS Federal funds purchased and securities sold under agreements to repurchase are 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 $230,000. 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. At March 31, 2018, federal funds purchased were $17,615 while total securities sold under agreements to repurchase (REPOs) were $250,771. Included in the $250,771 of total REPOs is a wholesale REPOs of $50,000, assumed in the Virginia Commerce merger. This wholesale REPO is scheduled to mature in May of 2018. The securities sold under agreements to repurchase were accounted for as collateralized financial transactions. They were recorded at the amounts at which the securities were acquired or sold plus accrued interest. United has a $20,000 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 will be renewable on a 360-day

Long-Term Borrowings

Long-Term Borrowings	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Long-Term Borrowings	9. LONG-TERM BORROWINGS United’s subsidiary bank is a member 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 March 31, 2018, United had an unused borrowing amount of approximately $4,213,640 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 March 31, 2018, $1,060,948 of FHLB advances with a weighted-average interest rate of 1.84% are scheduled to mature within the next seven years. The scheduled maturities of these FHLB borrowings are as follows: Year Amount 2018 $ 746,863 2019 187,516 2020 42,013 2021 52,693 2022 and thereafter 31,863 Total $ 1,060,948 At March 31, 2018, United had a total of fourteen 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 March 31, 2018 and December 31, 2017, the outstanding balance of the Debentures was $233,961 and $242,446, 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. For reporting periods prior to June 30, 2017, the Trust Preferred Securities qualified as Tier 1 regulatory capital under the “Basel III Capital Rules” as published by United’s primary federal regulator, the Federal Reserve, in July of 2013. The “Basel III Capital Rules” established a new comprehensive capital framework for U.S. banking organizations. Because United was less than $15 billion in total consolidated assets, the Basel III Capital Rules grandfathered 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 (the adoption date), United’s Trust Preferred Securities was subject to a limit of 25 percent of Tier 1 capital elements excluding any non-qualifying phase-out.

Commitments and Contingent Liab

Commitments and Contingent Liabilities	3 Months Ended
	Mar. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingent Liabilities	10. COMMITMENTS AND CONTINGENT LIABILITIES United is a party to financial instruments with off-balance-sheet 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 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 $4,001,212 and $4,224,719 of loan commitments outstanding as of March 31, 2018 and December 31, 2017, respectively, the majority of which contractually expire within one year. Included in the March 31, 2018 amount are commitments to extend credit of $400,836 related to George Mason’s mortgage loan funding commitments and are of a short-term nature. 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 March 31, 2018 and December 31, 2017, United had no 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 $142,532 and $147,017 as of March 31, 2018 and December 31, 2017, respectively. In accordance with the Contingencies Topic of the FASB Accounting Standards Codification, 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. George Mason provides for its estimated exposure to repurchase loans previously sold to investors for which borrowers failed to provide full and accurate information on their loan application or for which appraisals have not been acceptable or where the loan was not underwritten in accordance with the loan program specified by the loan investor, and for other exposure to its investors related to loan sales activities. United evaluates the merits of each claim and estimates its reserve based on actual and expected claims received and considers the historical amounts paid to settle such claims. George Mason has a reserve of $516 as of March 31, 2018. United has derivative counter-party risk that may arise from the possible inability of George Mason’s third party investors to meet the terms of their forward sales contracts. George Mason works with third-party investors that are generally well-capitalized, are investment grade and exhibit strong financial performance to mitigate this risk. United does not expect any third-party investor to fail to meet its obligation. United and its subsidiaries are currently involved in various legal proceedings 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	3 Months Ended
	Mar. 31, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Financial Instruments	11. 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. United accounts for its derivative financial instruments in accordance with the Derivatives and Hedging topic of the FASB Accounting Standards Codification (ASC topic 815). The Derivatives and Hedging topic require all derivative instruments to be carried at fair value on the balance sheet. United has designated certain derivative instruments used to manage interest rate risk as hedge relationships with certain assets, liabilities or cash flows being hedged. Certain derivatives used for interest rate risk management are not designated in a hedge relationship. 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. The portion of a hedge that is ineffective is recognized immediately in earnings. United through George Mason enters into interest rate lock commitments to finance residential mortgage loans with its customers. These commitments, which contain fixed expiration dates, offer the borrower an interest rate guarantee provided the loan meets underwriting guidelines and closes within the timeframe established by United. Interest rate risk arises on these commitments and subsequently closed loans if interest rates change between the time of the interest rate lock and the delivery of the loan to the investor. Market risk on interest rate lock commitments and mortgage loans held for sale is managed using corresponding forward mortgage loan sales contracts. United is a party to these forward mortgage loan sales contracts to sell loans servicing released and short sales of mortgage-backed securities. When the interest rate is locked with the borrower, the rate lock commitment, forward sale agreement, and mortgage-backed security position are undesignated derivatives and marked to fair value through earnings. The fair value of the rate lock derivative includes the servicing premium and the interest spread for the difference between retail and wholesale mortgage rates. Income from mortgage banking activities includes the gain recognized for the period presented and associated elements of fair value. United sells mortgage loans on either a best efforts or mandatory delivery basis. For loans sold on a mandatory delivery basis, United enters into forward mortgage-backed securities (the “residual hedge”) to mitigate the effect of interest rate risk. Both the rate lock commitment under mandatory delivery and the residual hedge are recorded at fair value through earnings and are not designated as accounting hedges. At the closing of the loan, the loan commitment derivative expires and United records a loan held for sale at fair value and continues to mark these assets to market under the election of fair value option. United closes out of the trading mortgage-backed securities assigned within the residual hedge and replaces the securities with a forward sales contract once a price has been accepted by an investor and recorded at fair value. For those loans selected to be sold under best efforts delivery, at the closing of the loan, the rate lock commitment derivative expires and the Company records a loan held for sale at fair value under the election of fair value option and continues to be obligated under the same forward loan sales contract entered into at inception of the rate lock commitment. The derivative portfolio also includes 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. 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 fair value. Gains and losses on other derivative financial instruments are included in noninterest income and noninterest expense, respectively. The following tables disclose the derivative instruments’ location on the Company’s Consolidated Balance Sheets and the notional amount and fair value of those instruments at March 31, 2018 and December 31, 2017. Asset Derivatives March 31, 2018 December 31, 2017 Balance Sheet Location Notional Amount Fair Value Balance Sheet Location Notional Amount Fair Value Derivatives designated as hedging instruments Fair Value Hedges: Interest rate swap contracts (hedging commercial loans) Other assets $ 88,679 $ 2,514 Other assets $ 71,831 $ 538 Total derivatives designated as hedging instruments $ 88,679 $ 2,514 $ 71,831 $ 538 Derivatives not designated as hedging instruments Forward loan sales commitments Other assets $ 15,712 $ 73 Other assets $ 31,024 $ 2 Interest rate lock commitments Other assets 195,330 5,610 Other assets 148,866 4,559 Total derivatives not designated as hedging instruments $ 211,042 $ 5,683 $ 179,890 $ 4,561 Total asset derivatives $ 299,721 $ 8,197 $ 251,721 $ 5,099 Liability Derivatives March 31, 2018 December 31, 2017 Balance Sheet Location Notional Amount Fair Value Balance Sheet Location Notional Amount Fair Value Derivatives designated as hedging instruments Fair Value Hedges: Interest rate swap contracts (hedging commercial loans) Other liabilities $ 0 $ 0 Other liabilities $ 18,795 $ 165 Total derivatives designated as hedging instruments $ 0 $ 0 $ 18,795 $ 165 Derivatives not designated as hedging instruments TBA mortgage-backed securities Other liabilities $ 258,000 $ 762 Other liabilities $ 236,500 $ 312 Interest rate lock commitments Other liabilities 0 0 Other liabilities 0 0 Total derivatives not designated as hedging instruments $ 258,000 $ 762 $ 236,500 $ 312 Total liability derivatives $ 258,000 $ 762 $ 255,295 $ 477 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 unaudited Consolidated Statements of Income for the three months ended March 31, 2018 and 2017 are presented as follows: Three Months Ended Income Statement Location March 31, March 31, Derivatives in hedging relationships Fair Value Hedges: Interest rate swap contracts Interest income/(expense) $ (42 ) $ (158 ) Total derivatives in hedging relationships $ (42 ) $ (158 ) Derivatives not designated as hedging instruments Forward loan sales commitments Income from Mortgage $ 73 $ 0 TBA mortgage-backed securities Income from Mortgage (450 ) 0 Interest rate lock commitments Income from Mortgage (1,269 ) 0 Total derivatives not designated as hedging instruments $ (1,646 ) $ 0 Total derivatives $ (1,688 ) $ (158 )

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	12. FAIR VALUE MEASUREMENTS United determines the fair values of its financial instruments based on the fair value hierarchy established by ASC topic 820, which also clarifies that fair value of certain assets and liabilities is an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. 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 prices, inputs and 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. 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 and equity securities bid-ask available-for-sale Loans held 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. The Company records its interest rate lock commitments and forward loan sales commitments at fair value determined as the amount that would be required to settle each of these derivative financial instruments at the balance sheet date. In the normal course of business, George Mason enters into contractual interest rate lock commitments to extend credit to borrowers with fixed expiration dates. The commitments become effective when the borrowers “lock-in” For interest rate swap 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 tables present the balances of financial assets and liabilities measured at fair value on a recurring basis as of March 31, 2018 and December 31, 2017, segregated by the level of the valuation inputs within the fair value hierarchy. Fair Value at March 31, 2018 Using Description Balance as of March 31, 2018 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 securities: U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 163,106 $ 0 $ 163,106 $ 0 State and political subdivisions 293,712 0 293,712 0 Residential mortgage-backed securities Fair Value at March 31, 2018 Using Description Balance as of March 31, 2018 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Agency 915,547 0 915,547 0 Non-agency 5,166 0 5,166 0 Commercial mortgage-backed securities Agency 476,779 0 476,779 0 Asset-backed securities 146,584 0 146,584 0 Trust preferred collateralized debt obligations 8,064 0 0 8,064 Single issue trust preferred securities 13,146 0 13,146 0 Other corporate securities 63,007 7,036 55,971 0 Total available for sale securities 2,085,111 7,036 2,070,011 8,064 Equity securities: Financial services industry 485 485 0 0 Equity mutual funds (1) 6,007 6,007 0 0 Other equity securities 4,668 4,668 0 0 Total equity securities 11,160 11,160 0 0 Loans held for sale 192,673 0 0 192,673 Derivative financial assets: Interest rate swap contracts 2,514 0 2,514 0 Forward sales commitments 73 0 73 0 Interest rate lock commitments 5,610 0 0 5,610 Total derivative financial assets 8,197 0 2,587 5,610 Liabilities Derivative financial liabilities: TBA mortgage-backed securities 762 0 762 0 Total derivative financial liabilities 762 0 762 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, 2017 Using Description Balance as of December 31, 2017 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 $ 114,758 $ 0 $ 114,758 $ 0 State and political subdivisions 303,869 0 303,869 0 Residential mortgage-backed securities Agency 814,593 0 814,593 0 Non-agency 5,512 0 5,512 0 Commercial mortgage-backed securities Agency 454,857 0 454,857 0 Asset-backed securities 109,970 0 109,970 0 Trust preferred collateralized debt obligations 34,269 0 0 34,269 Fair Value at December 31, 2017 Using Description Balance as of December 31, 2017 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Single issue trust preferred securities 12,560 0 12,560 0 Other corporate securities 28,490 0 28,490 0 Total available for sale debt securities 1,878,878 0 1,844,609 34,269 Available for sale equity securities: Financial services industry 3,545 331 3,214 0 Equity mutual funds (1) 6,332 6,332 0 0 Other equity securities 1 1 0 0 Total available for sale equity securities 9,878 6,664 3,214 0 Total available for sale securities 1,888,756 6,664 1,847,823 34,269 Loans held for sale 263,308 0 0 263,308 Derivative financial assets: Interest rate swap contracts 538 0 538 0 Interest rate lock commitments 4,561 0 2 4,559 Total derivative financial assets 5,099 0 540 4,559 Liabilities Derivative financial liabilities: Interest rate swap contracts 165 0 165 0 TBA mortgage-backed securities 312 0 312 0 Total derivative financial liabilities 477 0 477 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 three months ended March 31, 2018 and the year ended December 31, 2017. The following table presents additional information about financial assets and liabilities measured at fair value at March 31, 2018 and December 31, 2017 on a recurring basis and for which United has utilized Level 3 inputs to determine fair value: Available-for-sale Securities Trust preferred collateralized debt obligations March 31, 2018 December 31, Balance, beginning of period $ 34,269 $ 33,552 Total gains or losses (realized/unrealized): Included in earnings (or changes in net assets) 28 9 Included in other comprehensive income 217 8,757 Purchases, issuances, and settlements 0 0 Sales (26,450 ) (8,049 ) Transfers in and/or out of Level 3 0 0 Balance, end of period $ 8,064 $ 34,269 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 Loans held for sale March 31, 2018 December 31, Balance, beginning of period $ 263,308 $ 0 Acquired in Cardinal merger 0 271,301 Originations 573,732 2,333,927 Sales (631,834 ) (2,408,945 ) Total gains or losses during the period recognized in earnings 14,883 58,132 Transfers in and/or out of Level 3 (27,416 ) 8,893 Balance, end of period $ 192,673 $ 263,308 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 Derivative Financial Assets Interest Rate Lock Commitments March 31, 2018 December 31, Balance, beginning of period $ 4,559 $ 0 Acquired in Cardinal merger 0 10,393 Transfers other 1,051 (5,834 ) Balance, end of period $ 5,610 $ 4,559 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. Fair Value Option United elected the fair value option for the loans held for sale in its mortgage banking segment to mitigate a divergence between accounting losses and economic exposure. The following table reflects the change in fair value included in earnings of financial instruments for which the fair value option has been elected: Description Three Months Ended March 31, 2018 Three Months Ended March 31, 2017 Assets Loans held for sale Income from mortgage banking activities $ (1,719 ) $ 0 The following table reflects the difference between the aggregate fair value and the remaining contractual principal outstanding for financial instruments for which the fair value option has been elected: March 31, 2018 December 31, 2017 Description Unpaid Fair Value Fair Value Unpaid Fair Value Fair Value Assets Loans held for sale $ 188,998 $ 192,673 $ 3,675 $ 257,674 $ 263,308 $ 5,634 Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis 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 bi-annual Intangible Assets: The following table summarizes United’s financial assets that were measured at fair value on a nonrecurring basis during the period: Carrying value at March 31, 2018 Description Balance as of March 31, 2018 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) YTD Losses Assets Loans held for sale $ 1,242 $ 0 $ 1,242 $ 0 $ 0 Impaired Loans 76,400 0 56,632 19,768 1,376 OREO 22,778 0 22,702 76 585 Carrying value at December 31, 2017 Description Balance as of December 31, 2017 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) YTD Losses Assets Loans held for sale $ 2,647 $ 0 $ 2,647 $ 0 $ 14 Impaired Loans 88,637 0 70,950 17,687 12,291 OREO 24,348 0 24,151 197 4,200 Fair Value of Other Financial Instruments 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: one-to-four Deposits: Short-term Borrowings: Long-term Borrowings: Summary of Fair Values for All Financial Instruments The estimated fair values of United’s financial instruments, including those measured at amortized cost on the balance sheet, are summarized below: Fair Value Measurements Carrying Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) March 31, 2018 Cash and cash equivalents $ 1,139,170 $ 1,139,170 $ 0 $ 1,139,170 $ 0 Securities available for sale 2,085,111 2,085,111 7,036 2,070,011 8,064 Securities held to maturity 20,405 20,006 0 16,986 3,020 Equity securities 11,160 11,160 11,160 0 0 Other securities 152,287 144,673 0 0 144,673 Loans held for sale 193,915 193,915 0 1,242 192,673 Loans 12,907,764 12,207,257 0 0 12,207,257 Derivative financial assets 8,197 8,197 0 2,587 5,610 Deposits 13,646,168 13,611,626 0 13,611,626 0 Short-term borrowings 218,386 218,386 0 218,386 0 Long-term borrowings 1,344,909 1,317,352 0 1,317,352 0 Derivative financial liabilities 762 762 0 762 0 December 31, 2017 Cash and cash equivalents $ 1,666,167 $ 1,666,167 $ 0 $ 1,666,167 $ 0 Securities available for sale 1,888,756 1,888,756 6,664 1,847,823 34,269 Securities held to maturity 20,428 20,018 0 16,998 3,020 Other securities 162,461 154,338 0 0 154,338 Loans held for sale 265,955 265,955 0 2,647 263,308 Loans 12,934,794 12,437,797 0 0 12,437,797 Derivative financial assets 5,099 5,099 0 540 4,559 Deposits 13,830,591 14,024,720 0 14,024,720 0 Short-term borrowings 477,587 477,587 0 477,587 0 Long-term borrowings 1,363,977 1,338,754 0 1,338,754 0 Derivative financial liabilities 477 477 0 477 0

Stock Based Compensation

Stock Based Compensation	3 Months Ended
	Mar. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Based Compensation	13. 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 non-employee non-employee S-8 non-qualified Compensation expense of $968 and $682 related to the nonvested awards under United’s Long-Term Incentive Plans was incurred for the first quarter of 2018 and 2017, respectively. Compensation expense was included in employee compensation in the unaudited Consolidated Statements of Income. Stock Options United currently has options outstanding from various option plans other than the 2016 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. A summary of activity under United’s stock option plans as of March 31, 2018, and the changes during the first three months of 2018 are presented below: Three Months Ended March 31, 2018 Weighted Average Shares Aggregate Remaining Exercise Outstanding at January 1, 2018 1,558,438 $ 31.09 Granted 276,192 37.60 Exercised (15,043 ) 19.97 Forfeited or expired (2,438 ) 39.16 Outstanding at March 31, 2018 1,817,149 $ 9,046,231 6.3 $ 32.16 Exercisable at March 31, 2018 1,222,889 $ 9,027,432 4.9 $ 28.57 The following table summarizes the status of United’s nonvested stock option awards during the first three months of 2018: Shares Weighted-Average Nonvested at January 1, 2018 507,871 $ 7.89 Granted 276,192 7.56 Vested (187,365 ) 7.52 Forfeited or expired (2,438 ) 7.75 Nonvested at March 31, 2018 594,260 $ 7.85 During the three months ended March 31, 2018 and 2017, 15,043 and 22,523 shares, respectively, were issued in connection with stock option exercises. All shares issued in connection with stock option exercises for the three months ended March 31, 2018 and 2017 were issued from authorized and unissued stock. The total intrinsic value of options exercised under the Plans during the three months ended March 31, 2018 and 2017 was $246 and $452 respectively. Restricted Stock Under the 2011 LTI Plan, United may award restricted common shares to key employees and non-employee The following summarizes the changes to United’s restricted common shares for the period ended March 31, 2018: Number of Weighted-Average Outstanding at January 1, 2018 170,496 $ 40.05 Granted 97,004 37.60 Vested (62,285 ) 37.59 Forfeited (683 ) 39.15 Outstanding at March 31, 2018 204,532 $ 39.64

Employee Benefit Plans

Employee Benefit Plans	3 Months Ended
	Mar. 31, 2018
Retirement Benefits [Abstract]
Employee Benefit Plans	14. 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 are intended to provide not only for benefits attributed to service to date, but also for those expected to be earned in the future. During the first quarter of 2018, United made a discretionary contribution of $7,000 to the Plan. 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 had taken similar steps. The amendment provides that employees hired on or after October 1, 2007, will not be eligible to participate in the Plan. However, new employees will 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. Included in accumulated other comprehensive income at December 31, 2017 are unrecognized actuarial losses of $56,222 ($35,420 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, 2018 is $4,653 ($2,932 net of tax). Net periodic pension cost for the three months ended March 31, 2018 and 2017 included the following components: Three Months Ended March 31 2018 2017 Service cost $ 658 $ 562 Interest cost 1,295 1,265 Expected return on plan assets (2,522 ) (2,027 ) Amortization of transition asset 0 0 Recognized net actuarial loss 1,149 1,087 Amortization of prior service cost 0 0 Net periodic pension (benefit) cost $ 580 $ 887 Weighted-Average Assumptions: Discount rate 3.83 % 4.49 % Expected return on assets 7.00 % 7.00 % Rate of compensation increase (prior to age 45) 3.50 % 3.50 % Rate of compensation increase 3.00 % 3.00 %

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	15. INCOME TAXES United records a liability for uncertain income tax positions based on a recognition threshold of more-likely-than-not, As of March 31, 2018 and 2017, the total amount of accrued interest related to uncertain tax positions was $695 and $589, respectively. United accounts for interest and penalties related to uncertain tax positions as part of its provision for federal and state income taxes. United is currently open to audit under the statute of limitations by the Internal Revenue Service for the years ended December 31, 2014, 2015 and 2016 and certain State Taxing authorities for the years ended December 31, 2014 through 2016. On December 22, 2017, the Tax Cuts and Jobs Act (the “Tax Act”) was signed into law. The Tax Act lowered the Federal corporate tax rate from 35% to 21% effective January 1, 2018 and made numerous other tax law changes. U.S. generally accepted accounting principles (GAAP) requires companies to recognize the effect of tax law changes in the period of enactment. As a result of the Tax Act, United was required to remeasure deferred tax assets and liabilities at the new tax rate and as a result, recorded deferred tax expense of $37,732 in the fourth quarter of 2017. Reasonable estimates were made based on the Company’s analysis of the Tax Act. This provisional amount may be adjusted in future periods during 2018 when additional information is obtained as provided for under Staff Accounting Bulletin (“SAB 118”). Additional information that may affect our provisional amount would include further clarification and guidance on how the IRS will implement tax reform, further clarification and guidance on how state taxing authorities will implement tax reform and the related effect on the Company’s state income tax returns, completion of United’s 2017 tax return filings, and the potential for additional guidance from the SEC or the FASB related to the Tax Act. Management continues to evaluate other potential impacts of the Tax Act. The Company did not identify items for which the income tax effects of the Tax Act have not been completed and a reasonable estimate could not be determined as of March 31, 2018. United’s effective tax rate was 22.48% for the first quarter of 2018 and 34.25% for the first quarter of 2017. The lower effective tax rate for the first quarter of 2018 was due mainly to the Tax Act.

Comprehensive Income

Comprehensive Income	3 Months Ended
	Mar. 31, 2018
Equity [Abstract]
Comprehensive Income	16. COMPREHENSIVE INCOME The components of total comprehensive income for the three months ended March 31, 2018 and 2017 are as follows: Three Months Ended 2018 2017 Net Income $ 61,706 $ 38,809 Available for sale (“AFS”) securities: AFS securities with OTTI charges during the period 0 (44 ) Related income tax effect 0 16 Less : OTTI charges recognized in net income 0 44 Related income tax benefit 0 (16 ) Reclassification of previous noncredit OTTI to credit OTTI 0 0 Related income tax benefit 0 0 Net unrealized gain (loss) on AFS securities with OTTI 0 0 AFS securities – all other: Change in net unrealized gain on AFS securities arising during the period (22,017 ) 5,576 Related income tax effect 5,130 (2,063 ) Net reclassification adjustment for losses (gains) included in net income 149 (214 ) Related income tax (benefit) expense (35 ) 79 (16,773 ) 3,378 Net effect of AFS securities on other comprehensive income (16,773 ) 3,378 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 2 2 Related income tax expense (1 ) (1 ) Net effect of HTM securities on other comprehensive income 1 1 Pension plan: Recognized net actuarial loss 1,149 1,087 Related income tax benefit (416 ) (392 ) Net effect of change in pension plan asset on other comprehensive income 733 695 Total change in other comprehensive income (16,039 ) 4,074 Total Comprehensive Income $ 45,667 $ 42,883 The components of accumulated other comprehensive income for the three months ended March 31, 2018 are as follows: Changes in Accumulated Other Comprehensive Income (AOCI) by Component (a) For the Three Months Ended March 31, 2018 Unrealized Accretion on the unrealized Defined Items Total Balance at January 1, 2018 ($ 6,204 ) ($ 46 ) ($ 35,775 ) ($ 42,025 ) Cumulative effect of adopting Accounting Standard Update 2016-01 (136 ) (136 ) Reclass due to adopting Accounting Standard Update 2018-02 (1,632 ) (4,721 ) (6,353 ) Other comprehensive income before reclassification (16,887 ) 1 0 (16,886 ) Amounts reclassified from accumulated other comprehensive income 114 0 733 847 Net current-period other comprehensive income, net of tax (16,773 ) 1 733 (16,039 ) Balance at March 31, 2018 ($ 24,745 ) ($ 45 ) ($ 39,763 ) ($ 64,553 ) (a) All amounts are net-of-tax. Reclassifications out of Accumulated Other Comprehensive Income (AOCI) For the Three Months Ended March 31, 2018 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 $ 0 Net investment securities (losses) gains Net reclassification adjustment for losses 149 Net investment securities (losses) gains 149 Total before tax Related income tax effect (35 ) Tax expense 114 Net of tax Pension plan: Recognized net actuarial loss 1,149 (a) 1,149 Total before tax Related income tax effect (416 ) Tax expense 733 Net of tax Total reclassifications for the period $ 847 (a) This AOCI component is included in the computation of net periodic pension cost (see Note 14, Employee Benefit Plans)

Earnings Per Share

Earnings Per Share	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Earnings Per Share	17. 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: Three Months Ended March 31 2018 2017 Distributed earnings allocated to common stock $ 35,679 $ 26,722 Undistributed earnings allocated to common stock 25,919 12,014 Net earnings allocated to common shareholders $ 61,598 $ 38,736 Three Months Ended March 31 2018 2017 Average common shares outstanding 104,859,427 80,902,368 Common stock equivalents 303,431 404,172 Average diluted shares outstanding 105,162,858 81,306,540 Earnings per basic common share $ 0.59 $ 0.48 Earnings per diluted common share $ 0.59 $ 0.48

Variable Interest Entities

Variable Interest Entities	3 Months Ended
	Mar. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Variable Interest Entities	18. 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 fourteen statutory business trusts that were created for the purpose of raising funds that originally qualified for Tier I regulatory capital. As previously discussed, with the acquisition of Cardinal, these trusts now are considered Tier II 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. United does not consolidate these trusts as it is not the primary beneficiary of these entities because United’s wholly owned and indirect wholly owned statutory trust subsidiaries do not have a controlling financial interest in the VIEs. A controlling financial interest 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. Information related to United’s statutory trusts is presented in the table below: Description Issuance Date Amount of Interest Rate Maturity Date United Statutory Trust III December 17, 2003 $ 20,000 3-month December 17, 2033 United Statutory Trust IV December 19, 2003 $ 25,000 3-month January 23, 2034 United Statutory Trust V July 12, 2007 $ 50,000 3-month October 1, 2037 United Statutory Trust VI September 20, 2007 $ 30,000 3-month December 15, 2037 Premier Statutory Trust II September 25, 2003 $ 6,000 3-month October 8, 2033 Premier Statutory Trust III May 16, 2005 $ 8,000 3-month June 15, 2035 Premier Statutory Trust IV June 20, 2006 $ 14,000 3-month September 23, 2036 Premier Statutory Trust V December 14, 2006 $ 10,000 3-month March 1, 2037 Centra Statutory Trust I September 20, 2004 $ 10,000 3-month September 20, 2034 Centra Statutory Trust II June 15, 2006 $ 10,000 3-month July 7, 2036 Virginia Commerce Trust II December 19, 2002 $ 15,000 6-month December 19, 2032 Virginia Commerce Trust III December 20, 2005 $ 25,000 3-month February 23, 2036 Cardinal Statutory Trust I July 27, 2004 $ 20,000 3-month September 15, 2034 UFBC Capital Trust I December 30, 2004 $ 5,000 3-month March 15, 2035 United, through its banking subsidiary, 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 March 31, 2018 As of December 31, 2017 Aggregate Assets Aggregate Liabilities Risk Of Loss (1) Aggregate Assets Aggregate Liabilities Risk Of Loss (1) Trust preferred securities $ 257,527 $ 248,700 $ 8,827 $ 266,669 $ 257,674 $ 8,995 (1) Represents investment in VIEs.

Segment Information

Segment Information	3 Months Ended
	Mar. 31, 2018
Segment Reporting [Abstract]
Segment Information	19. SEGMENT INFORMATION As a result of the Cardinal acquisition in April 2017, United now operates in two business segments: community banking and mortgage banking. Prior to the Cardinal acquisition, United’s business activities were confined to just one reportable segment of community banking. Through its community banking segment, United offers a full range of products and services through various delivery channels. In particular, the community banking segment includes both commercial and consumer lending and provides customers with such products as commercial loans, real estate loans, business financing and consumer loans. In addition, this segment provides customers with several choices of deposit products including demand deposit accounts, savings accounts and certificates of deposit as well as investment and financial advisory services to businesses and individuals, including financial planning, retirement/estate planning, and investment management. The mortgage banking segment engages primarily in the origination and acquisition of residential mortgages for sale into the secondary market though George Mason. The community banking segment provides the mortgage banking segment (George Mason) with short-term funds to originate mortgage loans through a warehouse line of credit and charges the mortgage banking segment interest based on the prime rate. These transactions are eliminated in the consolidation process. The Company does not have any operating segments other than those reported. The “Other” category consists of financial information not directly attributable to a specific segment, including interest income from investments and net securities gains or losses of parent companies and their non-banking non-segment Information about the reportable segments and reconciliation of this information to the consolidated financial statements at and for the three months ended March 31, 2018 and 2017 is as follows: At and For the Three Months Ended March 31, 2018 Community Mortgage Other Consolidated Net interest income $ 146,261 $ 376 $ (2,594 ) $ 144,043 Provision for loans losses 5,178 0 0 5,178 Other income 17,131 14,883 (822 ) 31,192 Other expense 72,491 18,384 (423 ) 90,452 Income taxes 19,276 (703 ) (674 ) 17,899 Net income (loss) $ 66,447 $ (2,422 ) $ (2,319 ) $ 61,706 Total assets (liabilities) $ 18,319,946 $ 289,925 $ 9,831 $ 18,619,702 Average assets (liabilities) 18,318,613 210,172 15,012 18,543,797 At and For the Three Months Ended March 31, 2017 Community Other Consolidated Net interest income $ 109,660 $ (2,040 ) $ 107,620 Provision for loans losses 5,899 0 5,899 Other income 16,813 3,333 20,146 Other expense 62,752 90 62,842 Income taxes 19,804 412 20,216 Net income (loss) $ 38,018 $ 791 $ 38,809 Total assets (liabilities) $ 14,779,983 $ (17,668 ) $ 14,762,315 Average assets (liabilities) 14,433,409 (27,676 ) 14,405,733

Summary of Significant Accoun28

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited consolidated interim financial statements of United Bankshares, Inc. and Subsidiaries (“United” or “the Company”) have been prepared in accordance with accounting principles for interim financial information generally accepted in the United States (GAAP) and with the instructions for Form 10-Q S-X. 10-K. The accompanying consolidated interim financial statements include the accounts of United and its wholly owned subsidiaries. United operates in two business segments: community banking and mortgage banking. All significant intercompany accounts and transactions have been eliminated in the consolidated financial statements. Information is presented in these notes to the unaudited consolidated interim financial statements with dollars expressed in thousands, except per share or unless otherwise noted.
New Accounting Standards	New Accounting Standards In February 2018, the FASB issued ASU No. 2018-03, “Technical Corrections and Improvements to Financial Instruments – Overall (Subtopic 825-10): 2018-03 No. 2018-03 No. 2018-03 In February 2018, the FASB issued ASU No. 2018-02, “Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income,” to help organizations address certain stranded income tax effects in accumulated other comprehensive income (AOCI) resulting from the Tax Cuts and Jobs Act (the “Tax Act”). This ASU provides financial statement preparers with an option to reclassify stranded tax effects within AOCI to retained earnings in each period in which the effect of the change in the U.S. federal corporate income tax rate in the Tax Act (or portion thereof) is recorded. The amendments are effective for all organizations for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Early adoption is permitted. Organizations should apply the proposed amendments either in the period of adoption or retrospectively to each period (or periods) in which the effect of the change in the U.S. federal corporate income tax rate in the Tax Act is recognized. United adopted ASU No. 2018-02 In August 2017, the FASB issued ASU No. 2017-12, No. 2017-12 No. 2017-12 In July 2017, the FASB issued ASU No. 2017-11, No. 2017-11 No. 2017-11 In May 2017, the FASB issued ASU No. 2017-09, non-substantive No. 2017-09 No. 2017-09 In March 2017, the FASB issued ASU 2017-07, 2017-07 2017-07 2017-07 In January 2017, the FASB issued ASU 2017-04, 2017-04 2017-04 In January 2017, the FASB issued ASU 2017-01, 2017-01 2017-01 In August 2016, the FASB issued ASU 2016-15, 2016-15 2016-15 2016-15 In June 2016, the FASB issued ASU 2016-13, 2016-13 available-for-sale 2016-13 2016-13 In March 2016, the FASB issued ASU 2016-09, 2016-09 2016-09 2016-09 tax-related 2016-09 In February 2016, the FASB issued ASU 2016-02, 2016-02 2016-02 right-of-use 2016-02 2016-02 In January 2016, the FASB issued ASU 2016-01, 2016-01 2016-01 available-for-sale 2016-01 In May 2014, the FASB issued ASU 2014-09, 2014-09 2014-09 2014-09 2014-09 2014-09 Descriptions of our revenue-generating activities that are within the scope of ASC topic 606, which are presented in our Consolidated Statements of Income as components of Other Income are discussed below. There are no significant judgements relating to the amount and timing of revenue recognition for those revenue streams under the scope of ASC topic 606. Fees from Trust Services Revenue from trust services primarily is comprised of fees earned from the management and administration of trusts and other customer assets. Trust services include custody of assets, investment management, escrow services, and similar fiduciary activities. The Company’s performance obligation is generally satisfied over time and the resulting fees are recognized monthly, based upon the month-end Fees from Brokerage Services Revenue from brokerage services are recorded as the income is earned at the time the related service is performed. In return for such services, the Company charges a commission for the sales of various securities products primarily consisting of investment company shares, annuity products, and corporate debt and equity securities, for its selling and administrative efforts. For account supervision, advisory, and administrative services, revenue is recognized over a period of time as earned based on customer account balances and activity. Fees from Deposit Services Service charges on deposit accounts consist of account analysis fees (i.e., net fees earned on analyzed business and public checking accounts), monthly service fees, check orders, ATM activity fees, debit card fees, and other deposit account related fees. Revenue is recognized when our performance obligation is completed which is generally monthly for account maintenance services or when a transaction has been completed (ATM or debit card activity). Bankcard Fees and Merchant Discounts Bankcard fees and merchant discounts are primarily comprised of credit card income and merchant services income. Credit card income is primarily comprised of interchange fees earned whenever the Company’s credit cards are processed through card payment networks such as Visa. Merchant services income mainly represents fees charged to merchants to process their credit card transactions. The Company’s performance obligation for bankcard fees and exchange are largely satisfied, and related revenue recognized at the time services are rendered. Payment is typically received immediately or in the following month.
Fair Value Measurement	United determines the fair values of its financial instruments based on the fair value hierarchy established by ASC topic 820, which also clarifies that fair value of certain assets and liabilities is an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. 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 prices, inputs and 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.

Mergers and Acquisitions (Table

Mergers and Acquisitions (Tables)	3 Months Ended
	Mar. 31, 2018
Schedule of Acquired Loans Accounted for at Fair Value	In conjunction with the Cardinal merger, the acquired loan portfolio was accounted for at fair value as follows: April 21, 2017 Contractually required principal and interest at acquisition $ 4,211,734 Contractual cash flows not expected to be collected (56,176 ) Expected cash flows at acquisition 4,155,558 Interest component of expected cash flows (986,959 ) Basis in acquired loans at acquisition – estimated fair value $ 3,168,599
Cardinal Financial Corporation [Member]
Schedule of Fair Value of Acquired Identifiable Assets and Liabilities Assumed	The consideration paid for Cardinal’s common equity and the preliminary amounts of acquired identifiable assets and liabilities assumed as of the Cardinal Acquisition Date were as follows: Purchase price: Value of common shares issued (23,690,589 shares) $ 972,499 Fair value of stock options assumed 2,741 Cash for fractional shares 14 Total purchase price 975,254 Identifiable assets: Cash and cash equivalents 44,545 Investment securities 395,829 Loans held for sale 271,301 Loans 3,168,599 Premises and equipment 24,208 Core deposit intangibles 28,724 George Mason trade name intangible 1,080 Other assets 135,383 Total identifiable assets $ 4,069,669 Identifiable liabilities: Deposits $ 3,349,812 Short-term borrowings 96,215 Long-term borrowings 220,119 Unfavorable lease liability 2,281 Other liabilities 39,474 Total identifiable liabilities 3,707,901 Preliminary fair value of net assets acquired including identifiable intangible assets 361,768 Preliminary resulting goodwill $ 613,486
Schedule of Business Acquisition Pro Forma Information	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 Three Months Ended March 31, 2017 Total Revenues (1) $ 191,052 Net Income 54,710 (1) Represents net interest income plus other income

Investment Securities (Tables)

Investment Securities (Tables)	3 Months Ended
	Mar. 31, 2018
Summary of Amortized Cost and Estimated Fair Values of Available for Sale Securities	The amortized cost and estimated fair values of securities available for sale are summarized as follows. March 31, 2018 Gross Gross Estimated Cumulative Amortized Unrealized Unrealized Fair OTTI in Cost Gains Losses Value AOCI (1) U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 163,718 $ 237 $ 849 $ 163,106 $ 0 State and political subdivisions 297,481 1,300 5,069 293,712 0 Residential mortgage-backed securities Agency 934,557 993 20,003 915,547 0 Non-agency 4,665 501 0 5,166 86 Commercial mortgage-backed securities Agency 485,851 281 9,353 476,779 0 Asset-backed securities 146,774 285 475 146,584 0 Trust preferred collateralized debt obligations 9,192 0 1,128 8,064 2,586 Single issue trust preferred securities 13,433 327 614 13,146 0 Other corporate securities 63,400 337 730 63,007 0 Total $ 2,119,071 $ 4,261 $ 38,221 $ 2,085,111 $ 2,672 December 31, 2017 Gross Gross Estimated Cumulative Amortized Unrealized Unrealized Fair OTTI in Cost Gains Losses Value AOCI (1) U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 114,735 $ 385 $ 362 $ 114,758 $ 0 State and political subdivisions 303,101 3,197 2,429 303,869 0 Residential mortgage-backed securities Agency 821,857 2,096 9,360 814,593 0 Non-agency 4,969 543 0 5,512 86 Commercial mortgage-backed securities Agency 457,107 1,059 3,309 454,857 0 Asset-backed securities 109,829 148 7 109,970 0 Trust preferred collateralized debt obligations 37,856 542 4,129 34,269 20,770 Single issue trust preferred securities 13,417 368 1,225 12,560 0 Other corporate securities 28,101 407 18 28,490 0 Marketable equity securities 9,712 179 13 9,878 0 Total $ 1,900,684 $ 8,924 $ 20,852 $ 1,888,756 $ 20,856 (1) Non-credit before-tax.
Summary of Securities Available for Sale in an Unrealized Loss Position	The following is a summary of securities available-for-sale Less than 12 months 12 months or longer Fair Unrealized Fair Unrealized Value Losses Value Losses March 31, 2018 U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 65,919 $ 722 $ 22,751 $ 127 State and political subdivisions 137,221 1,584 55,674 3,485 Residential mortgage-backed securities Agency 682,082 13,128 172,052 6,875 Non-agency 0 0 0 0 Commercial mortgage-backed securities Agency 391,087 7,961 60,595 1,392 Asset-backed securities 56,833 475 0 0 Trust preferred collateralized debt obligations 0 0 5,049 1,128 Single issue trust preferred securities 0 0 5,100 614 Other corporate securities 41,634 730 0 0 Total $ 1,374,776 $ 24,600 $ 321,221 $ 13,621 Less than 12 months 12 months or longer Fair Unrealized Fair Unrealized Value Losses Value Losses December 31, 2017 U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 36,678 $ 230 $ 22,920 $ 132 State and political subdivisions 82,896 566 59,432 1,863 Residential mortgage-backed securities Agency 460,414 4,621 182,482 4,739 Non-agency 0 0 0 0 Commercial mortgage-backed securities Agency 282,858 2,386 70,763 923 Asset-backed securities 27,931 7 0 0 Trust preferred collateralized debt obligations 0 0 28,629 4,129 Single issue trust preferred securities 0 0 4,485 1,225 Other corporate securities 6,975 18 0 0 Marketable equity securities 0 0 363 13 Total $ 897,752 $ 7,828 $ 369,074 $ 13,024
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 of United and its subsidiaries. Three Months Ended March 31 2018 2017 Proceeds from sales and calls $ 99,703 $ 98,798 Gross realized gains 1,163 214 Gross realized losses 1,312 0
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. Three Months Ended March 31 2018 2017 Balance of cumulative credit losses at beginning of period $ 18,060 $ 22,162 Additions for credit losses recognized in earnings during the period: Additional credit losses on securities for which OTTI was previously recognized 0 0 Reductions for securities sold or paid off during the period (14,861 ) 0 Balance of cumulative credit losses at end of period $ 3,199 $ 22,162
Summary of Amortized Cost and Estimated Fair Values of Securities Held to Maturity	The amortized cost and estimated fair values of securities held to maturity are summarized as follows: March 31, 2018 Gross Gross Estimated Amortized Unrealized Unrealized Fair Cost Gains Losses Value U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 5,160 $ 241 $ 0 $ 5,401 State and political subdivisions 5,797 9 0 5,806 Residential mortgage-backed securities Agency 23 3 0 26 Single issue trust preferred securities 9,405 0 652 8,753 Other corporate securities 20 0 0 20 Total $ 20,405 $ 253 $ 652 $ 20,006 December 31, 2017 Gross Gross Estimated Amortized Unrealized Unrealized Fair Cost Gains Losses Value U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 5,187 $ 308 $ 0 $ 5,495 State and political subdivisions 5,797 10 0 5,807 Residential mortgage-backed securities Agency 23 3 0 26 Single issue trust preferred securities 9,401 0 731 8,670 Other corporate securities 20 0 0 20 Total $ 20,428 $ 321 $ 731 $ 20,018
Summary of Equity Securities	Prior to March 31, 2018 and the adoption of ASU 2016-01, equity securities were included in available for sale securities. Three Months March 31, 2018 Net gains (losses) recognized during the period $ (36 ) Net gains (losses) recognized during the period on equity securities sold 2 Unrealized gains recognized during the period on equity securities still held at period end 39 Unrealized losses recognized during the period on equity securities still held at period end 77
Available-for-sale Securities [Member]
Summary of Maturities of Debt Securities Held to Maturity by Amortized Cost and Estimated Fair Value	Expected maturities may differ from contractual maturities because the issuers may have the right to call or prepay obligations without penalties. March 31, 2018 December 31, 2017 Estimated Estimated Amortized Fair Amortized Fair Cost Value Cost Value Due in one year or less $ 52,863 $ 52,753 $ 50,311 $ 50,212 Due after one year through five years 476,361 471,410 386,039 384,585 Due after five years through ten years 445,861 436,757 400,129 398,208 Due after ten years 1,143,986 1,124,191 1,054,493 1,045,873 Marketable equity securities 0 0 9,712 9,878 Total $ 2,119,071 $ 2,085,111 $ 1,900,684 $ 1,888,756
Held-to-maturity Securities [Member]
Summary of Maturities of Debt Securities Held to Maturity by Amortized Cost and Estimated Fair Value	Expected maturities may differ from contractual maturities because the issuers may have the right to call or prepay obligations without penalties. March 31, 2018 December 31, 2017 Estimated Estimated Amortized Fair Amortized Fair Cost Value Cost Value Due in one year or less $ 0 $ 0 $ 0 $ 0 Due after one year through five years 9,318 9,566 9,344 9,660 Due after five years through ten years 8,091 7,618 5,663 5,343 Due after ten years 2,996 2,822 5,421 5,015 Total $ 20,405 $ 20,006 $ 20,428 $ 20,018

Loans (Tables)

Loans (Tables)	3 Months Ended
	Mar. 31, 2018
Receivables [Abstract]
Major Classes of Loans	Major classes of loans are as follows: March 31, 2018 December 31, Commercial, financial and agricultural: Owner-occupied commercial real estate $ 1,366,980 $ 1,361,629 Nonowner-occupied commercial real estate 4,426,776 4,451,298 Other commercial loans 1,952,322 1,998,979 Total commercial, financial & agricultural 7,746,078 7,811,906 Residential real estate 3,065,990 2,996,171 Construction & land development 1,433,125 1,504,907 Consumer: Bankcard 9,372 10,314 Other consumer 743,870 704,039 Total gross loans $ 12,998,435 $ 13,027,337
Activity for Accretable Yield	Activity for the accretable yield for the first three months of 2018 follows: Accretable yield at the beginning of the period $ 39,098 Accretion (including cash recoveries) (4,053 ) Additions 0 Net reclassifications to accretable from non-accretable 4,493 Disposals (including maturities, foreclosures, and charge-offs) (1,948 ) Accretable yield at the end of the period $ 37,590

Credit Quality (Tables)

Credit Quality (Tables)	3 Months Ended
	Mar. 31, 2018
Text Block [Abstract]
Schedule of Troubled Debt Restructurings, Segregated by Class of Loans	The following table sets forth United’s troubled debt restructurings that were restructured during the three months ended March 31, 2017, segregated by class of loans. Troubled Debt Restructurings For the Three Months Ended March 31, 2017 Number of Pre- Modification Post- Commercial real estate: Owner-occupied 0 $ 0 $ 0 Nonowner-occupied 0 0 0 Other commercial 4 2,752 2,741 Residential real estate 0 0 0 Construction & land development 1 1,456 1,450 Consumer: Bankcard 0 0 0 Other consumer 0 0 0 Total 5 $ 4,208 $ 4,191
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 March 31, 2018 30-89 Days Past Due 90 Days or more Past Due Total Past Due Current & Total Financing Receivables Recorded Investment >90 Days & Accruing Commercial real estate: Owner-occupied $ 13,303 $ 18,862 $ 32,165 $ 1,334,815 $ 1,366,980 $ 847 Nonowner-occupied 7,248 19,294 26,542 4,400,234 4,426,776 139 Other commercial 35,269 59,412 94,681 1,857,641 1,952,322 962 Residential real estate 30,344 25,641 55,985 3,010,005 3,065,990 6,027 Construction & land development 3,138 18,403 21,541 1,411,584 1,433,125 152 Consumer: Bankcard 185 121 306 9,066 9,372 121 Other consumer 6,417 1,196 7,613 736,257 743,870 917 Total $ 95,904 $ 142,929 $ 238,833 $ 12,759,602 $ 12,998,435 $ 9,165 (1) Other includes loans with a recorded investment of $189,675 acquired and accounted for under ASC topic 310-30 Age Analysis of Past Due Loans As of December 31, 2017 30-89 Past Due 90 Days or more Past Due Total Past Current & Total Financing Recorded & Accruing Commercial real estate: Owner-occupied $ 7,968 $ 13,663 $ 21,631 $ 1,339,998 $ 1,361,629 $ 458 Nonowner-occupied 10,398 20,448 30,846 4,420,452 4,451,298 634 Other commercial 11,533 68,476 80,009 1,918,970 1,998,979 940 Residential real estate 35,300 28,637 63,937 2,932,234 2,996,171 6,519 Construction & land development 1,615 17,190 18,805 1,486,102 1,504,907 385 Consumer: Bankcard 449 186 635 9,679 10,314 186 Other consumer 9,288 968 10,256 693,783 704,039 775 Total $ 76,551 $ 149,568 $ 226,119 $ 12,801,218 $ 13,027,337 $ 9,897 (1) Other includes loans with a recorded investment of $210,521 acquired and accounted for under ASC topic 310-30
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 March 31, 2018 December 31, 2017 Commercial real estate: Owner-occupied $ 18,015 $ 13,205 Nonowner-occupied 19,155 19,814 Other commercial 58,450 67,536 Residential real estate 19,614 22,118 Construction & land development 18,251 16,805 Consumer: Bankcard 0 0 Other consumer 279 193 Total $ 133,764 $ 139,671
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 March 31, 2018 Commercial Real Estate Other Construction & Land Owner- Nonowner- Grade: Pass $ 1,291,287 $ 4,250,743 $ 1,820,513 $ 1,349,638 Special mention 14,448 72,997 51,165 3,779 Substandard 61,245 103,036 77,848 79,708 Doubtful 0 0 2,796 0 Total $ 1,366,980 $ 4,426,776 $ 1,952,322 $ 1,433,125 As of December 31, 2017 Commercial Real Estate Other Construction & Land Development Owner- Nonowner- Grade: Pass $ 1,276,088 $ 4,312,985 $ 1,848,868 $ 1,413,706 Special mention 20,165 57,618 55,564 5,196 Substandard 65,376 80,695 90,625 86,005 Doubtful 0 0 3,922 0 Total $ 1,361,629 $ 4,451,298 $ 1,998,979 $ 1,504,907 Credit Quality Indicators Consumer Credit Exposure As of March 31, 2018 Residential Bankcard Other Grade: Pass $ 3,011,824 $ 9,066 $ 736,184 Special mention 20,738 185 6,460 Substandard 33,428 121 1,226 Doubtful 0 0 0 Total $ 3,065,990 $ 9,372 $ 743,870 As of December 31, 2017 Residential Bankcard Other Grade: Pass $ 2,945,266 $ 9,679 $ 693,727 Special mention 18,025 449 9,334 Substandard 32,880 186 978 Doubtful 0 0 0 Total $ 2,996,171 $ 10,314 $ 704,039
Schedule of Impaired Loans Information by Class of Loans	The following table sets forth United’s impaired loans information, by class of loans: Impaired Loans March 31, 2018 December 31, 2017 Recorded Unpaid Related Recorded Unpaid Related With no related allowance recorded: Commercial real estate: Owner-occupied $ 75,776 $ 75,941 $ 0 $ 78,117 $ 78,419 $ 0 Nonowner-occupied 117,589 117,648 0 134,136 134,195 0 Other commercial 52,394 54,953 0 46,993 49,552 0 Residential real estate 24,125 24,787 0 26,751 28,202 0 Construction & land development 48,320 53,084 0 52,279 59,691 0 Consumer: Bankcard 0 0 0 0 0 0 Other consumer 42 42 0 15 15 0 With an allowance recorded: Commercial real estate: Owner-occupied $ 5,873 $ 5,873 $ 1,075 $ 9,132 $ 9,132 $ 2,251 Nonowner-occupied 8,543 8,543 1,471 7,797 7,797 1,592 Other commercial 48,082 55,905 16,180 60,512 70,396 16,721 Residential real estate 11,887 13,438 1,742 9,813 10,418 1,552 Construction & land development 2,015 4,664 217 1,383 1,383 229 Consumer: Bankcard 0 0 0 0 0 0 Other consumer 0 0 0 0 0 0 Total: Commercial real estate: Owner-occupied $ 81,649 $ 81,814 $ 1,075 $ 87,249 $ 87,551 $ 2,251 Nonowner-occupied 126,132 126,191 1,471 141,933 141,992 1,592 Other commercial 100,476 110,858 16,180 107,505 119,948 16,721 Residential real estate 36,012 38,225 1,742 36,564 38,620 1,552 Construction & land development 50,335 57,748 217 53,662 61,074 229 Consumer: Bankcard 0 0 0 0 0 0 Other consumer 42 42 0 15 15 0 Impaired Loans For the Three Months Ended March 31, 2018 March 31, 2017 Average Interest Average Interest With no related allowance recorded: Commercial real estate: Owner-occupied $ 76,947 $ 377 $ 55,857 $ 421 Nonowner-occupied 125,863 120 82,528 117 Other commercial 49,693 206 49,286 220 Residential real estate 25,437 83 21,814 41 Construction & land development 50,300 103 35,949 76 Consumer: Bankcard 0 0 0 0 Other consumer 28 0 36 0 With an allowance recorded: Commercial real estate: Owner-occupied $ 7,502 $ 25 $ 7,663 $ 137 Nonowner-occupied 8,170 59 16,096 83 Other commercial 54,297 19 58,824 370 Residential real estate 10,850 0 13,113 8 Construction & land development 1,699 20 4,161 21 Consumer: Bankcard 0 0 0 0 Other consumer 0 0 0 0 Total: Commercial real estate: Owner-occupied $ 84,449 $ 402 $ 63,520 $ 558 Nonowner-occupied 134,033 179 98,624 200 Other commercial 103,990 225 108,110 590 Residential real estate 36,287 83 34,927 49 Construction & land development 51,999 123 40,110 97 Consumer: Bankcard 0 0 0 0 Other consumer 28 0 36 0

Allowance for Credit Losses (Ta

Allowance for Credit Losses (Tables)	3 Months Ended
	Mar. 31, 2018
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 periods indicated is summarized as follows: Allowance for Loan Losses and Carrying Amount of Loans For the Three Months Ended March 31, 2018 Commercial Real Estate Construction Allowance for Owner- Nonowner- Other Residential & Land Consumer Estimated Total Allowance for Loan Losses: Beginning balance $ 5,401 $ 6,369 $ 45,189 $ 9,927 $ 7,187 $ 2,481 $ 73 $ 76,627 Charge-offs 1,015 0 2,868 910 460 605 0 5,858 Recoveries 55 136 106 264 2 143 0 706 Provision (722 ) 269 4,490 972 (300 ) 372 97 5,178 Ending balance $ 3,719 $ 6,774 $ 46,917 $ 10,253 $ 6,429 $ 2,391 $ 170 $ 76,653 Ending Balance: individually evaluated for impairment $ 1,075 $ 1,471 $ 16,180 $ 1,742 $ 217 $ 0 $ 0 $ 20,685 Ending Balance: collectively evaluated for impairment $ 2,644 $ 5,303 $ 30,737 $ 8,511 $ 6,212 $ 2,391 $ 170 $ 55,968 Ending Balance: loans acquired with deteriorated credit quality $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 Financing receivables: Ending balance $ 1,366,980 $ 4,426,776 $ 1,952,322 $ 3,065,990 $ 1,433,125 $ 753,242 $ 0 $ 12,998,435 Ending Balance: individually evaluated for impairment $ 33,438 $ 22,868 $ 71,478 $ 13,856 $ 16,909 $ 0 $ 0 $ 158,549 Ending Balance: collectively evaluated for impairment $ 1,301,725 $ 4,310,587 $ 1,853,603 $ 3,039,123 $ 1,391,948 $ 753,225 $ 0 $ 12,650,211 Ending Balance: loans acquired with deteriorated credit quality $ 31,817 $ 93,321 $ 27,241 $ 13,011 $ 24,268 $ 17 $ 0 $ 189,675 Allowance for Loan Losses and Carrying Amount of Loans For the Year Ended December 31, 2017 Commercial Real Estate Construction Allowance for Owner- occupied Nonowner- occupied Other Commercial Residential Real Estate & Land Development Consumer Estimated Imprecision Total Allowance for Loan Losses: Beginning balance $ 5,273 $ 6,883 $ 33,087 $ 13,770 $ 10,606 $ 2,805 $ 347 $ 72,771 Charge-offs 2,246 296 21,189 2,973 3,337 2,822 0 32,863 Recoveries 2,599 244 3,395 601 726 748 0 8,313 Provision (225 ) (462 ) 29,896 (1,471 ) (808 ) 1,750 (274 ) 28,406 Ending balance $ 5,401 $ 6,369 $ 45,189 $ 9,927 $ 7,187 $ 2,481 $ 73 $ 76,627 Ending Balance: individually evaluated for impairment $ 2,251 $ 1,592 $ 16,721 $ 1,552 $ 229 $ 0 $ 0 $ 22,345 Ending Balance: collectively evaluated for impairment $ 3,150 $ 4,777 $ 28,468 $ 8,375 $ 6,958 $ 2,481 $ 73 $ 54,282 Ending Balance: loans acquired with deteriorated credit quality $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 Financing receivables: Ending balance $ 1,361,629 $ 4,451,298 $ 1,998,979 $ 2,996,171 $ 1,504,907 $ 714,353 $ 0 $ 13,027,337 Ending Balance: individually evaluated for impairment $ 36,721 $ 21,851 $ 78,715 $ 14,316 $ 16,921 $ 0 $ 0 $ 168,524 Ending Balance: collectively evaluated for impairment $ 1,291,379 $ 4,320,997 $ 1,892,706 $ 2,967,666 $ 1,461,206 $ 714,338 $ 0 $ 12,648,292 Ending Balance: loans acquired with deteriorated credit quality $ 33,529 $ 108,450 $ 27,558 $ 14,189 $ 26,780 $ 15 $ 0 $ 210,521

Intangible Assets (Tables)

Intangible Assets (Tables)	3 Months Ended
	Mar. 31, 2018
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: March 31, 2018 Community Banking Mortgage Banking Total Gross Carrying Amount Accumulated Amortization Gross Carrying Amount Accumulated Gross Accumulated Amortized intangible assets: Core deposit intangible assets $ 98,359 ($ 56,463 ) $ 0 ($ 0 ) $ 98,359 ($ 56,463 ) Non-amortized George Mason trade name $ 0 $ 1,080 $ 1,080 Goodwill not subject to amortization $ 1,473,265 $ 5,315 $ 1,478,580 December 31, 2017 Community Banking Mortgage Banking Total Gross Carrying Amount Accumulated Amortization Gross Carrying Amount Accumulated Amortization Gross Carrying Amount Accumulated Amortization Amortized intangible assets: Core deposit intangible assets $ 98,359 ($ 54,453 ) $ 0 $ 0 $ 98,359 ($ 54,453 ) Non-amortized George Mason trade name $ 0 $ 1,080 $ 1,080 Goodwill not subject to amortization $ 1,473,265 $ 5,115 $ 1,478,380
Reconciliation of Goodwill	The following table provides a reconciliation of goodwill: Community Banking Mortgage Banking Total Goodwill at December 31, 2017 $ 1,473,265 $ 5,115 $ 1,478,380 Preliminary addition to goodwill from Cardinal acquisition 0 200 200 Goodwill at March 31, 2018 $ 1,473,265 $ 5,315 $ 1,478,580
Schedule of Anticipated Amortization Expense	The following table sets forth the anticipated amortization expense for intangible assets for the years subsequent to 2017: Year Amount 2018 $ 8,039 2019 7,016 2020 6,309 2021 5,369 2022 and thereafter 17,173

Long-Term Borrowings (Tables)

Long-Term Borrowings (Tables)	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Schedule of Maturities of Long-term Borrowings	The scheduled maturities of these FHLB borrowings are as follows: Year Amount 2018 $ 746,863 2019 187,516 2020 42,013 2021 52,693 2022 and thereafter 31,863 Total $ 1,060,948

Derivative Financial Instrume36

Derivative Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Notional Amount and Fair Value of Derivative Financial Instruments	The following tables disclose the derivative instruments’ location on the Company’s Consolidated Balance Sheets and the notional amount and fair value of those instruments at March 31, 2018 and December 31, 2017. Asset Derivatives March 31, 2018 December 31, 2017 Balance Sheet Location Notional Amount Fair Value Balance Sheet Location Notional Amount Fair Value Derivatives designated as hedging instruments Fair Value Hedges: Interest rate swap contracts (hedging commercial loans) Other assets $ 88,679 $ 2,514 Other assets $ 71,831 $ 538 Total derivatives designated as hedging instruments $ 88,679 $ 2,514 $ 71,831 $ 538 Derivatives not designated as hedging instruments Forward loan sales commitments Other assets $ 15,712 $ 73 Other assets $ 31,024 $ 2 Interest rate lock commitments Other assets 195,330 5,610 Other assets 148,866 4,559 Total derivatives not designated as hedging instruments $ 211,042 $ 5,683 $ 179,890 $ 4,561 Total asset derivatives $ 299,721 $ 8,197 $ 251,721 $ 5,099 Liability Derivatives March 31, 2018 December 31, 2017 Balance Sheet Location Notional Amount Fair Value Balance Sheet Location Notional Amount Fair Value Derivatives designated as hedging instruments Fair Value Hedges: Interest rate swap contracts (hedging commercial loans) Other liabilities $ 0 $ 0 Other liabilities $ 18,795 $ 165 Total derivatives designated as hedging instruments $ 0 $ 0 $ 18,795 $ 165 Derivatives not designated as hedging instruments TBA mortgage-backed securities Other liabilities $ 258,000 $ 762 Other liabilities $ 236,500 $ 312 Interest rate lock commitments Other liabilities 0 0 Other liabilities 0 0 Total derivatives not designated as hedging instruments $ 258,000 $ 762 $ 236,500 $ 312 Total liability derivatives $ 258,000 $ 762 $ 255,295 $ 477
Schedule of Derivative Financial Instruments on Statement of Income	The effect of United’s derivative financial instruments on its unaudited Consolidated Statements of Income for the three months ended March 31, 2018 and 2017 are presented as follows: Three Months Ended Income Statement Location March 31, March 31, Derivatives in hedging relationships Fair Value Hedges: Interest rate swap contracts Interest income/(expense) $ (42 ) $ (158 ) Total derivatives in hedging relationships $ (42 ) $ (158 ) Derivatives not designated as hedging instruments Forward loan sales commitments Income from Mortgage $ 73 $ 0 TBA mortgage-backed securities Income from Mortgage (450 ) 0 Interest rate lock commitments Income from Mortgage (1,269 ) 0 Total derivatives not designated as hedging instruments $ (1,646 ) $ 0 Total derivatives $ (1,688 ) $ (158 )

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Schedule of Financial Assets and Liabilities Measured at Fair Value	The following tables present the balances of financial assets and liabilities measured at fair value on a recurring basis as of March 31, 2018 and December 31, 2017, segregated by the level of the valuation inputs within the fair value hierarchy. Fair Value at March 31, 2018 Using Description Balance as of March 31, 2018 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 securities: U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 163,106 $ 0 $ 163,106 $ 0 State and political subdivisions 293,712 0 293,712 0 Residential mortgage-backed securities Fair Value at March 31, 2018 Using Description Balance as of March 31, 2018 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Agency 915,547 0 915,547 0 Non-agency 5,166 0 5,166 0 Commercial mortgage-backed securities Agency 476,779 0 476,779 0 Asset-backed securities 146,584 0 146,584 0 Trust preferred collateralized debt obligations 8,064 0 0 8,064 Single issue trust preferred securities 13,146 0 13,146 0 Other corporate securities 63,007 7,036 55,971 0 Total available for sale securities 2,085,111 7,036 2,070,011 8,064 Equity securities: Financial services industry 485 485 0 0 Equity mutual funds (1) 6,007 6,007 0 0 Other equity securities 4,668 4,668 0 0 Total equity securities 11,160 11,160 0 0 Loans held for sale 192,673 0 0 192,673 Derivative financial assets: Interest rate swap contracts 2,514 0 2,514 0 Forward sales commitments 73 0 73 0 Interest rate lock commitments 5,610 0 0 5,610 Total derivative financial assets 8,197 0 2,587 5,610 Liabilities Derivative financial liabilities: TBA mortgage-backed securities 762 0 762 0 Total derivative financial liabilities 762 0 762 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, 2017 Using Description Balance as of December 31, 2017 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 $ 114,758 $ 0 $ 114,758 $ 0 State and political subdivisions 303,869 0 303,869 0 Residential mortgage-backed securities Agency 814,593 0 814,593 0 Non-agency 5,512 0 5,512 0 Commercial mortgage-backed securities Agency 454,857 0 454,857 0 Asset-backed securities 109,970 0 109,970 0 Trust preferred collateralized debt obligations 34,269 0 0 34,269 Fair Value at December 31, 2017 Using Description Balance as of December 31, 2017 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Single issue trust preferred securities 12,560 0 12,560 0 Other corporate securities 28,490 0 28,490 0 Total available for sale debt securities 1,878,878 0 1,844,609 34,269 Available for sale equity securities: Financial services industry 3,545 331 3,214 0 Equity mutual funds (1) 6,332 6,332 0 0 Other equity securities 1 1 0 0 Total available for sale equity securities 9,878 6,664 3,214 0 Total available for sale securities 1,888,756 6,664 1,847,823 34,269 Loans held for sale 263,308 0 0 263,308 Derivative financial assets: Interest rate swap contracts 538 0 538 0 Interest rate lock commitments 4,561 0 2 4,559 Total derivative financial assets 5,099 0 540 4,559 Liabilities Derivative financial liabilities: Interest rate swap contracts 165 0 165 0 TBA mortgage-backed securities 312 0 312 0 Total derivative financial liabilities 477 0 477 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 March 31, 2018 and December 31, 2017 on a recurring basis and for which United has utilized Level 3 inputs to determine fair value: Available-for-sale Securities Trust preferred collateralized debt obligations March 31, 2018 December 31, Balance, beginning of period $ 34,269 $ 33,552 Total gains or losses (realized/unrealized): Included in earnings (or changes in net assets) 28 9 Included in other comprehensive income 217 8,757 Purchases, issuances, and settlements 0 0 Sales (26,450 ) (8,049 ) Transfers in and/or out of Level 3 0 0 Balance, end of period $ 8,064 $ 34,269 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 Loans held for sale March 31, 2018 December 31, Balance, beginning of period $ 263,308 $ 0 Acquired in Cardinal merger 0 271,301 Originations 573,732 2,333,927 Sales (631,834 ) (2,408,945 ) Total gains or losses during the period recognized in earnings 14,883 58,132 Transfers in and/or out of Level 3 (27,416 ) 8,893 Balance, end of period $ 192,673 $ 263,308 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 Derivative Financial Assets Interest Rate Lock Commitments March 31, 2018 December 31, Balance, beginning of period $ 4,559 $ 0 Acquired in Cardinal merger 0 10,393 Transfers other 1,051 (5,834 ) Balance, end of period $ 5,610 $ 4,559 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
Schedule of Changes in Fair Value Included in Earnings of Financial Instruments for which Fair Value Option has been Elected	The following table reflects the change in fair value included in earnings of financial instruments for which the fair value option has been elected: Description Three Months Ended March 31, 2018 Three Months Ended March 31, 2017 Assets Loans held for sale Income from mortgage banking activities $ (1,719 ) $ 0
Summary of Difference Between Aggregate Fair Value and Remaining Contractual Principal Outstanding for Financial Instruments for which Fair Value Option has been Elected	The following table reflects the difference between the aggregate fair value and the remaining contractual principal outstanding for financial instruments for which the fair value option has been elected: March 31, 2018 December 31, 2017 Description Unpaid Fair Value Fair Value Unpaid Fair Value Fair Value Assets Loans held for sale $ 188,998 $ 192,673 $ 3,675 $ 257,674 $ 263,308 $ 5,634
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 during the period: Carrying value at March 31, 2018 Description Balance as of March 31, 2018 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) YTD Losses Assets Loans held for sale $ 1,242 $ 0 $ 1,242 $ 0 $ 0 Impaired Loans 76,400 0 56,632 19,768 1,376 OREO 22,778 0 22,702 76 585 Carrying value at December 31, 2017 Description Balance as of December 31, 2017 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) YTD Losses Assets Loans held for sale $ 2,647 $ 0 $ 2,647 $ 0 $ 14 Impaired Loans 88,637 0 70,950 17,687 12,291 OREO 24,348 0 24,151 197 4,200
Summary of Estimated Fair Values of Financial Instruments	The estimated fair values of United’s financial instruments, including those measured at amortized cost on the balance sheet, are summarized below: Fair Value Measurements Carrying Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) March 31, 2018 Cash and cash equivalents $ 1,139,170 $ 1,139,170 $ 0 $ 1,139,170 $ 0 Securities available for sale 2,085,111 2,085,111 7,036 2,070,011 8,064 Securities held to maturity 20,405 20,006 0 16,986 3,020 Equity securities 11,160 11,160 11,160 0 0 Other securities 152,287 144,673 0 0 144,673 Loans held for sale 193,915 193,915 0 1,242 192,673 Loans 12,907,764 12,207,257 0 0 12,207,257 Derivative financial assets 8,197 8,197 0 2,587 5,610 Deposits 13,646,168 13,611,626 0 13,611,626 0 Short-term borrowings 218,386 218,386 0 218,386 0 Long-term borrowings 1,344,909 1,317,352 0 1,317,352 0 Derivative financial liabilities 762 762 0 762 0 December 31, 2017 Cash and cash equivalents $ 1,666,167 $ 1,666,167 $ 0 $ 1,666,167 $ 0 Securities available for sale 1,888,756 1,888,756 6,664 1,847,823 34,269 Securities held to maturity 20,428 20,018 0 16,998 3,020 Other securities 162,461 154,338 0 0 154,338 Loans held for sale 265,955 265,955 0 2,647 263,308 Loans 12,934,794 12,437,797 0 0 12,437,797 Derivative financial assets 5,099 5,099 0 540 4,559 Deposits 13,830,591 14,024,720 0 14,024,720 0 Short-term borrowings 477,587 477,587 0 477,587 0 Long-term borrowings 1,363,977 1,338,754 0 1,338,754 0 Derivative financial liabilities 477 477 0 477 0

Stock Based Compensation (Table

Stock Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of Stock Option Plans	A summary of activity under United’s stock option plans as of March 31, 2018, and the changes during the first three months of 2018 are presented below: Three Months Ended March 31, 2018 Weighted Average Shares Aggregate Remaining Exercise Outstanding at January 1, 2018 1,558,438 $ 31.09 Granted 276,192 37.60 Exercised (15,043 ) 19.97 Forfeited or expired (2,438 ) 39.16 Outstanding at March 31, 2018 1,817,149 $ 9,046,231 6.3 $ 32.16 Exercisable at March 31, 2018 1,222,889 $ 9,027,432 4.9 $ 28.57
Status of United's Nonvested Stock Option Awards	The following table summarizes the status of United’s nonvested stock option awards during the first three months of 2018: Shares Weighted-Average Nonvested at January 1, 2018 507,871 $ 7.89 Granted 276,192 7.56 Vested (187,365 ) 7.52 Forfeited or expired (2,438 ) 7.75 Nonvested at March 31, 2018 594,260 $ 7.85
Changes to United's Restricted Common Shares	The following summarizes the changes to United’s restricted common shares for the period ended March 31, 2018: Number of Weighted-Average Outstanding at January 1, 2018 170,496 $ 40.05 Granted 97,004 37.60 Vested (62,285 ) 37.59 Forfeited (683 ) 39.15 Outstanding at March 31, 2018 204,532 $ 39.64

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	3 Months Ended
	Mar. 31, 2018
Retirement Benefits [Abstract]
Net Periodic Pension Cost	Net periodic pension cost for the three months ended March 31, 2018 and 2017 included the following components: Three Months Ended March 31 2018 2017 Service cost $ 658 $ 562 Interest cost 1,295 1,265 Expected return on plan assets (2,522 ) (2,027 ) Amortization of transition asset 0 0 Recognized net actuarial loss 1,149 1,087 Amortization of prior service cost 0 0 Net periodic pension (benefit) cost $ 580 $ 887 Weighted-Average Assumptions: Discount rate 3.83 % 4.49 % Expected return on assets 7.00 % 7.00 % Rate of compensation increase (prior to age 45) 3.50 % 3.50 % Rate of compensation increase 3.00 % 3.00 %

Comprehensive Income (Tables)

Comprehensive Income (Tables)	3 Months Ended
	Mar. 31, 2018
Equity [Abstract]
Components of Total Comprehensive Income	The components of total comprehensive income for the three months ended March 31, 2018 and 2017 are as follows: Three Months Ended 2018 2017 Net Income $ 61,706 $ 38,809 Available for sale (“AFS”) securities: AFS securities with OTTI charges during the period 0 (44 ) Related income tax effect 0 16 Less : OTTI charges recognized in net income 0 44 Related income tax benefit 0 (16 ) Reclassification of previous noncredit OTTI to credit OTTI 0 0 Related income tax benefit 0 0 Net unrealized gain (loss) on AFS securities with OTTI 0 0 AFS securities – all other: Change in net unrealized gain on AFS securities arising during the period (22,017 ) 5,576 Related income tax effect 5,130 (2,063 ) Net reclassification adjustment for losses (gains) included in net income 149 (214 ) Related income tax (benefit) expense (35 ) 79 (16,773 ) 3,378 Net effect of AFS securities on other comprehensive income (16,773 ) 3,378 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 2 2 Related income tax expense (1 ) (1 ) Net effect of HTM securities on other comprehensive income 1 1 Pension plan: Recognized net actuarial loss 1,149 1,087 Related income tax benefit (416 ) (392 ) Net effect of change in pension plan asset on other comprehensive income 733 695 Total change in other comprehensive income (16,039 ) 4,074 Total Comprehensive Income $ 45,667 $ 42,883
Components of Accumulated Other Comprehensive Income	The components of accumulated other comprehensive income for the three months ended March 31, 2018 are as follows: Changes in Accumulated Other Comprehensive Income (AOCI) by Component (a) For the Three Months Ended March 31, 2018 Unrealized Accretion on the unrealized Defined Items Total Balance at January 1, 2018 ($ 6,204 ) ($ 46 ) ($ 35,775 ) ($ 42,025 ) Cumulative effect of adopting Accounting Standard Update 2016-01 (136 ) (136 ) Reclass due to adopting Accounting Standard Update 2018-02 (1,632 ) (4,721 ) (6,353 ) Other comprehensive income before reclassification (16,887 ) 1 0 (16,886 ) Amounts reclassified from accumulated other comprehensive income 114 0 733 847 Net current-period other comprehensive income, net of tax (16,773 ) 1 733 (16,039 ) Balance at March 31, 2018 ($ 24,745 ) ($ 45 ) ($ 39,763 ) ($ 64,553 ) (a) All amounts are net-of-tax.
Reclassifications Out of Accumulated Other Comprehensive Income	Reclassifications out of Accumulated Other Comprehensive Income (AOCI) For the Three Months Ended March 31, 2018 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 $ 0 Net investment securities (losses) gains Net reclassification adjustment for losses 149 Net investment securities (losses) gains 149 Total before tax Related income tax effect (35 ) Tax expense 114 Net of tax Pension plan: Recognized net actuarial loss 1,149 (a) 1,149 Total before tax Related income tax effect (416 ) Tax expense 733 Net of tax Total reclassifications for the period $ 847 (a) This AOCI component is included in the computation of net periodic pension cost (see Note 14, Employee Benefit Plans)

Earnings Per Share (Tables)

Earnings Per Share (Tables)	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [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: Three Months Ended March 31 2018 2017 Distributed earnings allocated to common stock $ 35,679 $ 26,722 Undistributed earnings allocated to common stock 25,919 12,014 Net earnings allocated to common shareholders $ 61,598 $ 38,736 Three Months Ended March 31 2018 2017 Average common shares outstanding 104,859,427 80,902,368 Common stock equivalents 303,431 404,172 Average diluted shares outstanding 105,162,858 81,306,540 Earnings per basic common share $ 0.59 $ 0.48 Earnings per diluted common share $ 0.59 $ 0.48

Variable Interest Entities (Tab

Variable Interest Entities (Tables)	3 Months Ended
	Mar. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Information Related to Statutory Trusts	Information related to United’s statutory trusts is presented in the table below: Description Issuance Date Amount of Interest Rate Maturity Date United Statutory Trust III December 17, 2003 $ 20,000 3-month December 17, 2033 United Statutory Trust IV December 19, 2003 $ 25,000 3-month January 23, 2034 United Statutory Trust V July 12, 2007 $ 50,000 3-month October 1, 2037 United Statutory Trust VI September 20, 2007 $ 30,000 3-month December 15, 2037 Premier Statutory Trust II September 25, 2003 $ 6,000 3-month October 8, 2033 Premier Statutory Trust III May 16, 2005 $ 8,000 3-month June 15, 2035 Premier Statutory Trust IV June 20, 2006 $ 14,000 3-month September 23, 2036 Premier Statutory Trust V December 14, 2006 $ 10,000 3-month March 1, 2037 Centra Statutory Trust I September 20, 2004 $ 10,000 3-month September 20, 2034 Centra Statutory Trust II June 15, 2006 $ 10,000 3-month July 7, 2036 Virginia Commerce Trust II December 19, 2002 $ 15,000 6-month December 19, 2032 Virginia Commerce Trust III December 20, 2005 $ 25,000 3-month February 23, 2036 Cardinal Statutory Trust I July 27, 2004 $ 20,000 3-month September 15, 2034 UFBC Capital Trust I December 30, 2004 $ 5,000 3-month March 15, 2035
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 March 31, 2018 As of December 31, 2017 Aggregate Assets Aggregate Liabilities Risk Of Loss (1) Aggregate Assets Aggregate Liabilities Risk Of Loss (1) Trust preferred securities $ 257,527 $ 248,700 $ 8,827 $ 266,669 $ 257,674 $ 8,995 (1) Represents investment in VIEs.

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2018
Segment Reporting [Abstract]
Summary of Segment Reporting Information	Information about the reportable segments and reconciliation of this information to the consolidated financial statements at and for the three months ended March 31, 2018 and 2017 is as follows: At and For the Three Months Ended March 31, 2018 Community Mortgage Other Consolidated Net interest income $ 146,261 $ 376 $ (2,594 ) $ 144,043 Provision for loans losses 5,178 0 0 5,178 Other income 17,131 14,883 (822 ) 31,192 Other expense 72,491 18,384 (423 ) 90,452 Income taxes 19,276 (703 ) (674 ) 17,899 Net income (loss) $ 66,447 $ (2,422 ) $ (2,319 ) $ 61,706 Total assets (liabilities) $ 18,319,946 $ 289,925 $ 9,831 $ 18,619,702 Average assets (liabilities) 18,318,613 210,172 15,012 18,543,797 At and For the Three Months Ended March 31, 2017 Community Other Consolidated Net interest income $ 109,660 $ (2,040 ) $ 107,620 Provision for loans losses 5,899 0 5,899 Other income 16,813 3,333 20,146 Other expense 62,752 90 62,842 Income taxes 19,804 412 20,216 Net income (loss) $ 38,018 $ 791 $ 38,809 Total assets (liabilities) $ 14,779,983 $ (17,668 ) $ 14,762,315 Average assets (liabilities) 14,433,409 (27,676 ) 14,405,733

Summary of Significant Accoun44

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Mar. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclass due to adopting Accounting Standard Update		$ 0
ASU 2016-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Decrease in income tax expense	$ 1,048
Accounting Standards Update 2018-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclass due to adopting Accounting Standard Update		$ 6,353

Mergers and Acquisitions - Addi

Mergers and Acquisitions - Additional Information (Detail) - USD ($)	Mar. 31, 2018	Apr. 21, 2017	Mar. 31, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Total assets at consummation	$ 18,619,702,000		$ 18,619,702,000	$ 19,058,959,000
Loans at consummation	12,998,435,000		12,998,435,000	13,027,337,000
Deposits at consummation	13,646,168,000		13,646,168,000	13,830,591,000
Resulting goodwill	1,478,580,000		1,478,580,000	$ 1,478,380,000
Liabilities to provide severance benefits	$ 0		$ 0
Contractually required principal and interest at acquisition		$ 132,837,000
Expected cash flows at acquisition		108,275,000
Estimated fair value of acquired impaired loans at acquisition		$ 86,696,000
Cardinal Financial Corporation [Member]
Business Acquisition [Line Items]
Acquisition completion date			Apr. 21, 2017
Outstanding common stock acquired		100.00%
Total assets at consummation		$ 4,136,008,000
Loans at consummation		3,313,033,000
Deposits at consummation		3,344,740,000
Common stock paid in cash		975,254,000
Common stock value		972,499,000
Stock options exchanged value		$ 2,741,000
Common stock, shares issued		23,690,589
Resulting goodwill		$ 613,486,000
Fractional shares cash paid per share		14,000
Goodwill from acquisition expected to be tax deductible		0
Fair value discounts on loans acquired		144,434,000
Fair value discounts on leases		2,281,000
Fair value adjustment on trust preferred issuances		8,738,000
Premiums on land acquired		4,408,000
Premiums on interest-bearing deposits acquired		5,072,000
Premiums on long-term FHLB advances acquired		10,740,000
Estimated remaining life of discount on leases acquired	5 years 6 months
Estimated remaining life of discount on trust preferred issuances acquired	16 years 5 months 20 days
Estimated remaining life of premium on interest-bearing deposits acquired	4 years 6 months
Estimated remaining life of the FHLB advances acquired	4 years 3 months 22 days
Assumed liabilities to provide severance benefits		1,825,000
Contractually required principal and interest at acquisition		4,211,734,000
Expected cash flows at acquisition		4,155,558,000
Estimated fair value of acquired impaired loans at acquisition		3,168,599,000
Revenue since acquisition included in consolidated results			$ 340,632,000
Revenue since acquisition included in consolidated results			$ 157,852,000
Cardinal Financial Corporation [Member] | Common Stock [Member]
Business Acquisition [Line Items]
Common stock value		$ 972,499,000
Common stock, shares issued		23,690,589
Closing market price per common share		$ 41.05
Cardinal Financial Corporation [Member] | Core Deposit Intangible Assets [Member]
Business Acquisition [Line Items]
Purchase price allocation of Identifiable Intangible assets		$ 28,724,000
Estimated period of amortization of core deposit intangibles		10 years
Fractional shares cash paid per share		$ 14,000
Cardinal Financial Corporation [Member] | George Mason Trade Name Intangible [Member]
Business Acquisition [Line Items]
Purchase price allocation of Identifiable Intangible assets		$ 1,080,000

Mergers and Acquisitions - Sche

Mergers and Acquisitions - Schedule of Acquired Loans Accounted for at Fair Value (Detail) $ in Thousands	Apr. 21, 2017USD ($)
Business Acquisition [Line Items]
Contractually required principal and interest at acquisition	$ 132,837
Expected cash flows at acquisition	108,275
Basis in acquired loans at acquisition - estimated fair value	86,696
Cardinal Financial Corporation [Member]
Business Acquisition [Line Items]
Contractually required principal and interest at acquisition	4,211,734
Contractual cash flows not expected to be collected	(56,176)
Expected cash flows at acquisition	4,155,558
Interest component of expected cash flows	(986,959)
Basis in acquired loans at acquisition - estimated fair value	$ 3,168,599

Mergers and Acquisitions - Sc47

Mergers and Acquisitions - Schedule of Fair Value of Acquired Identifiable Assets and Liabilities Assumed (Detail) - USD ($) $ in Thousands	Apr. 21, 2017	Mar. 31, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Resulting goodwill		$ 1,478,580	$ 1,478,380
Cardinal Financial Corporation [Member]
Business Acquisition [Line Items]
Value of common shares issued	$ 972,499
Fair value of stock options assumed	2,741
Cash for fractional shares	14
Total purchase price	975,254
Cash and cash equivalents	44,545
Investment securities	395,829
Loans held for sale	271,301
Loans	3,168,599
Premises and equipment	24,208
Other assets	135,383
Total identifiable assets	4,069,669
Deposits	3,349,812
Short-term borrowings	96,215
Long-term borrowings	220,119
Unfavorable lease liability	2,281
Other liabilities	39,474
Total identifiable liabilities	3,707,901
Preliminary fair value of net assets acquired including identifiable intangible assets	361,768
Resulting goodwill	613,486
Cardinal Financial Corporation [Member] | Core Deposit Intangible Assets [Member]
Business Acquisition [Line Items]
Cash for fractional shares	14
Intangible assets	28,724
Cardinal Financial Corporation [Member] | George Mason Trade Name Intangible [Member]
Business Acquisition [Line Items]
Intangible assets	$ 1,080

Mergers and Acquisitions - Sc48

Mergers and Acquisitions - Schedule of Fair Value of Acquired Identifiable Assets and Liabilities Assumed (Parenthetical) (Detail)	Apr. 21, 2017shares
Cardinal Financial Corporation [Member]
Business Acquisition [Line Items]
Common stock, shares issued	23,690,589

Mergers and Acquisitions - Sc49

Mergers and Acquisitions - Schedule of Business Acquisition Pro Forma Information (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2017USD ($)
Business Combinations [Abstract]
Total Revenues	$ 191,052
Net Income	$ 54,710

Investment Securities - Summary

Investment Securities - Summary of Amortized Cost and Estimated Fair Values of Available for Sale Securities (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Schedule of Investments [Line Items]
Amortized Cost	$ 2,119,071	$ 1,900,684
Gross Unrealized Gains	4,261	8,924
Gross Unrealized Losses	38,221	20,852
Estimated Fair Value	2,085,111	1,888,756
Cumulative OTTI in AOCI	2,672	20,856
U.S. Treasury Securities and Obligations of U.S. Government Corporations and Agencies [Member]
Schedule of Investments [Line Items]
Amortized Cost	163,718	114,735
Gross Unrealized Gains	237	385
Gross Unrealized Losses	849	362
Estimated Fair Value	163,106	114,758
Cumulative OTTI in AOCI	0	0
State and Political Subdivisions [Member]
Schedule of Investments [Line Items]
Amortized Cost	297,481	303,101
Gross Unrealized Gains	1,300	3,197
Gross Unrealized Losses	5,069	2,429
Estimated Fair Value	293,712	303,869
Cumulative OTTI in AOCI	0	0
Residential Mortgage-Backed Securities, Agency [Member]
Schedule of Investments [Line Items]
Amortized Cost	934,557	821,857
Gross Unrealized Gains	993	2,096
Gross Unrealized Losses	20,003	9,360
Estimated Fair Value	915,547	814,593
Cumulative OTTI in AOCI	0	0
Residential Mortgage-Backed Securities, Non-agency [Member]
Schedule of Investments [Line Items]
Amortized Cost	4,665	4,969
Gross Unrealized Gains	501	543
Gross Unrealized Losses	0	0
Estimated Fair Value	5,166	5,512
Cumulative OTTI in AOCI	86	86
Commercial Mortgage-Backed Securities, Agency [Member]
Schedule of Investments [Line Items]
Amortized Cost	485,851	457,107
Gross Unrealized Gains	281	1,059
Gross Unrealized Losses	9,353	3,309
Estimated Fair Value	476,779	454,857
Cumulative OTTI in AOCI	0	0
Asset-Backed Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	146,774	109,829
Gross Unrealized Gains	285	148
Gross Unrealized Losses	475	7
Estimated Fair Value	146,584	109,970
Cumulative OTTI in AOCI	0	0
Trust Preferred Collateralized Debt Obligations [Member]
Schedule of Investments [Line Items]
Amortized Cost	9,192	37,856
Gross Unrealized Gains	0	542
Gross Unrealized Losses	1,128	4,129
Estimated Fair Value	8,064	34,269
Cumulative OTTI in AOCI	2,586	20,770
Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	13,433	13,417
Gross Unrealized Gains	327	368
Gross Unrealized Losses	614	1,225
Estimated Fair Value	13,146	12,560
Cumulative OTTI in AOCI	0	0
Corporate Bonds [Member]
Schedule of Investments [Line Items]
Amortized Cost	63,400	28,101
Gross Unrealized Gains	337	407
Gross Unrealized Losses	730	18
Estimated Fair Value	63,007	28,490
Cumulative OTTI in AOCI	$ 0	0
Marketable Equity Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost		9,712
Gross Unrealized Gains		179
Gross Unrealized Losses		13
Estimated Fair Value		9,878
Cumulative OTTI in AOCI		$ 0

Investment Securities - Summa51

Investment Securities - Summary of Securities Available for Sale in an Unrealized Loss Position (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	$ 1,374,776	$ 897,752
Less than 12 months, Unrealized Losses	24,600	7,828
12 months or longer, Fair Value	321,221	369,074
12 months or longer, Unrealized Losses	13,621	13,024
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	65,919	36,678
Less than 12 months, Unrealized Losses	722	230
12 months or longer, Fair Value	22,751	22,920
12 months or longer, Unrealized Losses	127	132
State and Political Subdivisions [Member]
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	137,221	82,896
Less than 12 months, Unrealized Losses	1,584	566
12 months or longer, Fair Value	55,674	59,432
12 months or longer, Unrealized Losses	3,485	1,863
Residential Mortgage-Backed Securities, Agency [Member]
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	682,082	460,414
Less than 12 months, Unrealized Losses	13,128	4,621
12 months or longer, Fair Value	172,052	182,482
12 months or longer, Unrealized Losses	6,875	4,739
Residential Mortgage-Backed Securities, Non-agency [Member]
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	0	0
Less than 12 months, Unrealized Losses	0	0
12 months or longer, Fair Value	0	0
12 months or longer, Unrealized Losses	0	0
Commercial Mortgage-Backed Securities, Agency [Member]
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	391,087	282,858
Less than 12 months, Unrealized Losses	7,961	2,386
12 months or longer, Fair Value	60,595	70,763
12 months or longer, Unrealized Losses	1,392	923
Asset-Backed Securities [Member]
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	56,833	27,931
Less than 12 months, Unrealized Losses	475	7
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	0
Less than 12 months, Unrealized Losses	0	0
12 months or longer, Fair Value	5,049	28,629
12 months or longer, Unrealized Losses	1,128	4,129
Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	0	0
Less than 12 months, Unrealized Losses	0	0
12 months or longer, Fair Value	5,100	4,485
12 months or longer, Unrealized Losses	614	1,225
Corporate Bonds [Member]
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	41,634	6,975
Less than 12 months, Unrealized Losses	730	18
12 months or longer, Fair Value	0	0
12 months or longer, Unrealized Losses	$ 0	0
Marketable Equity Securities [Member]
Schedule of Investments [Line Items]
Less than 12 months, Fair Value		0
Less than 12 months, Unrealized Losses		0
12 months or longer, Fair Value		363
12 months or longer, Unrealized Losses		$ 13

Investment Securities - Summa52

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	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Proceeds from sales and calls	$ 99,703	$ 98,798
Gross realized gains	1,163	214
Gross realized losses	$ 1,312	$ 0

Investment Securities - Additio

Investment Securities - Additional Information (Detail)	Apr. 03, 2018USD ($)Security	Mar. 31, 2018USD ($)SecuritySecurities	Mar. 31, 2017USD ($)	Dec. 31, 2017USD ($)
Schedule of Investments [Line Items]
Gross unrealized losses on available for sale securities		$ 38,221,000		$ 20,852,000
Available for sale securities in unrealized loss position | Securities		635
Available for sale securities in portfolio, number | Securities		870
Amortized cost of available for sale securities		$ 2,119,071,000		1,900,684,000
Capitalization of banks, equal to or greater than, in the single-issue trust preferred portfolio		10,000,000,000
Securities sold, total		2,085,111,000		1,888,756,000
Gross realized gains		0	$ 0
Gross realized losses		0	$ 0
Cost of equity securities		11,160,000		0
Carrying value of securities pledged		1,612,649,000		1,403,565,000
SunTrust Bank [Member]
Schedule of Investments [Line Items]
Amortized cost of trust preferred securities		7,428,000
Royal Bank of Scotland [Member]
Schedule of Investments [Line Items]
Amortized cost of trust preferred securities		976,000
Investment Grade [Member]
Schedule of Investments [Line Items]
Amortized cost of available for sale single issue trust preferred securities		7,719,000
Below Investment Grade [Member]
Schedule of Investments [Line Items]
Amortized cost of available for sale single issue trust preferred securities		5,714,000
State and Political Subdivisions [Member]
Schedule of Investments [Line Items]
Gross unrealized losses on available for sale securities		5,069,000		2,429,000
Amortized cost of available for sale securities		$ 297,481,000		303,101,000
Percent of portfolio with credit support		77.00%
Investment grade credit rate percentage		1.00%
Number of equity securities other-than-temporarily impaired | Securities		0
Securities sold, total		$ 293,712,000		303,869,000
Agency Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Amortized cost of available for sale securities		1,420,408,000
Commercial Mortgage-Backed Securities, Agency [Member]
Schedule of Investments [Line Items]
Gross unrealized losses on available for sale securities		9,353,000		3,309,000
Amortized cost of available for sale securities		485,851,000		457,107,000
Securities sold, total		476,779,000		454,857,000
Residential Mortgage-Backed Securities, Agency [Member]
Schedule of Investments [Line Items]
Gross unrealized losses on available for sale securities		20,003,000		9,360,000
Amortized cost of available for sale securities		934,557,000		821,857,000
Securities sold, total		915,547,000		814,593,000
Residential Mortgage-Backed Securities, Non-agency [Member]
Schedule of Investments [Line Items]
Gross unrealized losses on available for sale securities		0		0
Amortized cost of available for sale securities		4,665,000		4,969,000
Securities sold, total		5,166,000		5,512,000
Residential Mortgage-Backed Securities, Non-agency [Member] | Investment Grade [Member]
Schedule of Investments [Line Items]
Amortized cost of available for sale securities		473,000
Residential Mortgage-Backed Securities, Non-agency [Member] | Below Investment Grade [Member]
Schedule of Investments [Line Items]
Amortized cost of available for sale securities		4,192,000
Marketable Equity Securities [Member]
Schedule of Investments [Line Items]
Gross unrealized losses on available for sale securities				13,000
Amortized cost of available for sale securities				9,712,000
Securities sold, total				9,878,000
Total other-than-temporarily impairment		300,000
Trust Preferred Collateralized Debt Obligations [Member]
Schedule of Investments [Line Items]
Gross unrealized losses on available for sale securities		1,128,000		4,129,000
Amortized cost of available for sale securities		9,192,000		37,856,000
Securities sold, total		8,064,000		34,269,000
Trust Preferred Collateralized Debt Obligations [Member] | TRUP CDOs [Member]
Schedule of Investments [Line Items]
Amortized cost of available for sale securities		9,192,000
Reduction in amortized cost		$ 28,664,000
Number of securities sold | Security		7
Securities sold, total		$ 25,315,000
Number of securities redeemed | Security		1
Securities redeemed value		$ 3,300,000
Trust Preferred Collateralized Debt Obligations [Member] | TRUP CDOs [Member] | Subsequent Event [Member]
Schedule of Investments [Line Items]
Number of securities redeemed | Security	1
Securities redeemed value	$ 3,016,000
Corporate Bonds [Member]
Schedule of Investments [Line Items]
Gross unrealized losses on available for sale securities		730,000		18,000
Amortized cost of available for sale securities		$ 63,400,000		28,101,000
Number of equity securities other-than-temporarily impaired		0
Securities sold, total		$ 63,007,000		$ 28,490,000
Corporate Bonds [Member] | Debt Issuances of Corporations [Member]
Schedule of Investments [Line Items]
Amortized cost of available for sale securities		$ 63,400,000
Corporate Bonds [Member] | Investment Grade [Member]
Schedule of Investments [Line Items]
Percent of corporate securities portfolio		67.00%
Corporate Bonds [Member] | Below Investment Grade [Member]
Schedule of Investments [Line Items]
Percent of corporate securities portfolio		33.00%

Investment Securities - Roll Fo

Investment Securities - Roll Forward of Credit Losses on Securities (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Cumulative credit losses, Beginning Balance	$ 18,060	$ 22,162
Additional credit losses on securities for which OTTI was previously recognized	0	0
Reductions for securities sold or paid off during the period	(14,861)	0
Cumulative credit losses, Ending Balance	$ 3,199	$ 22,162

Investment Securities - Summa55

Investment Securities - Summary of Maturities of Securities Available for Sale by Amortized Cost and Estimated Fair Value (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Due in one year or less, Amortized Cost	$ 52,863	$ 50,311
Due after one year through five years, Amortized Cost	476,361	386,039
Due after five years through ten years, Amortized Cost	445,861	400,129
Due after ten years, Amortized Cost	1,143,986	1,054,493
Marketable equity securities, Amortized Cost	0	9,712
Amortized Cost	2,119,071	1,900,684
Due in one year or less, Estimated Fair Value	52,753	50,212
Due after one year through five years, Estimated Fair Value	471,410	384,585
Due after five years through ten years, Estimated Fair Value	436,757	398,208
Due after ten years, Estimated Fair Value	1,124,191	1,045,873
Marketable equity securities, Estimated Fair Value	0	9,878
Total available for sale securities	$ 2,085,111	$ 1,888,756

Investment Securities - Summa56

Investment Securities - Summary of Amortized Cost and Estimated Fair Values of Securities Held to Maturity (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Schedule of Investments [Line Items]
Amortized Cost	$ 20,405	$ 20,428
Gross Unrealized Gains	253	321
Gross Unrealized Losses	652	731
Estimated Fair Value	20,006	20,018
U.S. Treasury Securities and Obligations of U.S. Government Corporations and Agencies [Member]
Schedule of Investments [Line Items]
Amortized Cost	5,160	5,187
Gross Unrealized Gains	241	308
Gross Unrealized Losses	0	0
Estimated Fair Value	5,401	5,495
State and Political Subdivisions [Member]
Schedule of Investments [Line Items]
Amortized Cost	5,797	5,797
Gross Unrealized Gains	9	10
Gross Unrealized Losses	0	0
Estimated Fair Value	5,806	5,807
Residential Mortgage-Backed Securities, Agency [Member]
Schedule of Investments [Line Items]
Amortized Cost	23	23
Gross Unrealized Gains	3	3
Gross Unrealized Losses	0	0
Estimated Fair Value	26	26
Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	9,405	9,401
Gross Unrealized Gains	0	0
Gross Unrealized Losses	652	731
Estimated Fair Value	8,753	8,670
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 - Summa57

Investment Securities - Summary of Maturities of Debt Securities Held to Maturity by Amortized Cost and Estimated Fair Value (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Due in one year or less, Amortized Cost	$ 0	$ 0
Due after one year through five years, Amortized Cost	9,318	9,344
Due after five years through ten years, Amortized Cost	8,091	5,663
Due after ten years, Amortized Cost	2,996	5,421
Amortized Cost	20,405	20,428
Due in one year or less, Estimated Fair Value	0	0
Due after one year through five years, Estimated Fair Value	9,566	9,660
Due after five years through ten year, Estimated Fair Value	7,618	5,343
Due after ten years, Estimated Fair Value	2,822	5,015
Estimated Fair Value, Total	$ 20,006	$ 20,018

Investment Securities - Summa58

Investment Securities - Summary of Equity Securities (Detail) - Marketable Equity Securities [Member] $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)
Schedule of Available-for-sale Securities [Line Items]
Net gains (losses) recognized during the period	$ (36)
Net gains (losses) recognized during the period on equity securities sold	2
Unrealized gains recognized during the period on equity securities still held at period end	39
Unrealized losses recognized during the period on equity securities still held at period end	$ 77

Loans - Major Classes of Loans

Loans - Major Classes of Loans (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Commercial, financial, and agricultural
Total commercial, financial & agricultural	$ 7,746,078	$ 7,811,906
Residential real estate	3,065,990	2,996,171
Construction & land development	1,433,125	1,504,907
Consumer:
Bankcard	9,372	10,314
Other consumer	743,870	704,039
Total Financing Receivables	12,998,435	13,027,337
Owner-Occupied [Member]
Commercial, financial, and agricultural
Total commercial, financial & agricultural	1,366,980	1,361,629
Nonowner-Occupied [Member]
Commercial, financial, and agricultural
Total commercial, financial & agricultural	4,426,776	4,451,298
Other Commercial [Member]
Commercial, financial, and agricultural
Total commercial, financial & agricultural	$ 1,952,322	$ 1,998,979

Loans - Additional Information

Loans - Additional Information (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Loans held for sale	$ 193,915	$ 265,955
Acquired impaired loans from merger	$ 12,998,435	$ 13,027,337
Percentage of acquired impaired loans from merger on total gross loans	1.46%	1.62%
Recorded investment in acquired impaired loans	$ 253,827	$ 285,964
Directors and Officers [Member]
Related party loans	35,777	36,360
Loans Acquired with Deteriorated Credit Quality [Member]
Acquired impaired loans from merger	$ 189,675	$ 210,521

Loans - Activity for Accretable

Loans - Activity for Accretable Yield (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Accretable yield at the beginning of the period	$ 39,098
Accretion (including cash recoveries)	(4,053)
Additions	0
Net reclassifications to accretable from non-accretable	4,493
Disposals (including maturities, foreclosures, and charge-offs)	(1,948)
Accretable yield at the end of the period	$ 37,590

Credit Quality - Additional Inf

Credit Quality - Additional Information (Detail) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018USD ($)SecurityLoan	Mar. 31, 2017USD ($)	Dec. 31, 2017USD ($)
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	$ 48,271		$ 50,129
Restructured loans on nonaccrual status	33,592		30,868
Restructured loans modified by reduction in interest	1,760
Restructured loan and interest	1,891
Restructured loans modified by change in terms	$ 44,620
Number of loans restructured | SecurityLoan	0
Restructured loans modified by reduction in interest rate and change in terms		$ 4,191
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
Real estate acquired in foreclosure or other settlement of loans	$ 22,778		24,348
Recorded investment of consumer mortgage loans	377		873
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Restructured loans on nonaccrual status			95
Financing Receivables 30 To 89 Days Past Due [Member]
Restructured loans on nonaccrual status	$ 85		$ 1,254

Credit Quality - Schedule of Tr

Credit Quality - Schedule of Troubled Debt Restructurings, Segregated by Class of Loans (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2017USD ($)Contract
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	5
Pre-Modification Outstanding Recorded Investment	$ 4,208
Post-Modification Outstanding Recorded Investment	$ 4,191
Construction & Land Development [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	1
Pre-Modification Outstanding Recorded Investment	$ 1,456
Post-Modification Outstanding Recorded Investment	$ 1,450
Commercial Real Estate [Member] | Owner-Occupied [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	0
Pre-Modification Outstanding Recorded Investment	$ 0
Post-Modification Outstanding Recorded Investment	$ 0
Commercial Real Estate [Member] | Nonowner-Occupied [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	0
Pre-Modification Outstanding Recorded Investment	$ 0
Post-Modification Outstanding Recorded Investment	$ 0
Other Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	4
Pre-Modification Outstanding Recorded Investment	$ 2,752
Post-Modification Outstanding Recorded Investment	$ 2,741
Residential Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	0
Pre-Modification Outstanding Recorded Investment	$ 0
Post-Modification Outstanding Recorded Investment	$ 0
Consumer [Member] | Bankcard [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	0
Pre-Modification Outstanding Recorded Investment	$ 0
Post-Modification Outstanding Recorded Investment	$ 0
Consumer [Member] | Other Consumer [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	0
Pre-Modification Outstanding Recorded Investment	$ 0
Post-Modification Outstanding 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	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, 30-89 Days Past Due	$ 95,904	$ 76,551
Loans, Total Past Due	238,833	226,119
Loans, Current & Other	12,759,602	12,801,218
Total Financing Receivables	12,998,435	13,027,337
Loans, Recorded Investment >90 Days & Accruing	9,165	9,897
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Total Past Due	142,929	149,568
Construction & Land Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, 30-89 Days Past Due	3,138	1,615
Loans, Total Past Due	21,541	18,805
Loans, Current & Other	1,411,584	1,486,102
Total Financing Receivables	1,433,125	1,504,907
Loans, Recorded Investment >90 Days & Accruing	152	385
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	18,403	17,190
Commercial Real Estate [Member] | Owner-Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, 30-89 Days Past Due	13,303	7,968
Loans, Total Past Due	32,165	21,631
Loans, Current & Other	1,334,815	1,339,998
Total Financing Receivables	1,366,980	1,361,629
Loans, Recorded Investment >90 Days & Accruing	847	458
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	18,862	13,663
Commercial Real Estate [Member] | Nonowner-Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, 30-89 Days Past Due	7,248	10,398
Loans, Total Past Due	26,542	30,846
Loans, Current & Other	4,400,234	4,420,452
Total Financing Receivables	4,426,776	4,451,298
Loans, Recorded Investment >90 Days & Accruing	139	634
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	19,294	20,448
Other Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, 30-89 Days Past Due	35,269	11,533
Loans, Total Past Due	94,681	80,009
Loans, Current & Other	1,857,641	1,918,970
Total Financing Receivables	1,952,322	1,998,979
Loans, Recorded Investment >90 Days & Accruing	962	940
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	59,412	68,476
Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, 30-89 Days Past Due	30,344	35,300
Loans, Total Past Due	55,985	63,937
Loans, Current & Other	3,010,005	2,932,234
Total Financing Receivables	3,065,990	2,996,171
Loans, Recorded Investment >90 Days & Accruing	6,027	6,519
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	25,641	28,637
Consumer [Member] | Bankcard [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, 30-89 Days Past Due	185	449
Loans, Total Past Due	306	635
Loans, Current & Other	9,066	9,679
Total Financing Receivables	9,372	10,314
Loans, Recorded Investment >90 Days & Accruing	121	186
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	121	186
Consumer [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, 30-89 Days Past Due	6,417	9,288
Loans, Total Past Due	7,613	10,256
Loans, Current & Other	736,257	693,783
Total Financing Receivables	743,870	704,039
Loans, Recorded Investment >90 Days & Accruing	917	775
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	$ 1,196	$ 968

Credit Quality - Schedule of 65

Credit Quality - Schedule of Age Analysis of its Past Due Loans, Segregated by Class of Loans (Parenthetical) (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Acquired impaired loans from merger	$ 12,998,435	$ 13,027,337
Loans Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Acquired impaired loans from merger	$ 189,675	$ 210,521

Credit Quality - Schedule of No

Credit Quality - Schedule of Nonaccrual Loans, Segregated by Class of Loans (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans on Nonaccrual Status	$ 133,764	$ 139,671
Construction & Land Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans on Nonaccrual Status	18,251	16,805
Commercial Real Estate [Member] | Owner-Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans on Nonaccrual Status	18,015	13,205
Commercial Real Estate [Member] | Nonowner-Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans on Nonaccrual Status	19,155	19,814
Other Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans on Nonaccrual Status	58,450	67,536
Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans on Nonaccrual Status	19,614	22,118
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	$ 279	$ 193

Credit Quality - Schedule of Cr

Credit Quality - Schedule of Credit Quality Indicators Information, by Class of Loans (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	$ 12,998,435	$ 13,027,337
Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	3,065,990	2,996,171
Other Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	1,952,322	1,998,979
Bankcard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	9,372	10,314
Other Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	743,870	704,039
Owner-Occupied [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	1,366,980	1,361,629
Nonowner-Occupied [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	4,426,776	4,451,298
Construction & Land Development [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	1,433,125	1,504,907
Pass [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	3,011,824	2,945,266
Pass [Member] | Other Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	1,820,513	1,848,868
Pass [Member] | Bankcard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	9,066	9,679
Pass [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	736,184	693,727
Pass [Member] | Owner-Occupied [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	1,291,287	1,276,088
Pass [Member] | Nonowner-Occupied [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	4,250,743	4,312,985
Pass [Member] | Construction & Land Development [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	1,349,638	1,413,706
Special Mention [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	20,738	18,025
Special Mention [Member] | Other Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	51,165	55,564
Special Mention [Member] | Bankcard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	185	449
Special Mention [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	6,460	9,334
Special Mention [Member] | Owner-Occupied [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	14,448	20,165
Special Mention [Member] | Nonowner-Occupied [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	72,997	57,618
Special Mention [Member] | Construction & Land Development [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	3,779	5,196
Substandard [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	33,428	32,880
Substandard [Member] | Other Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	77,848	90,625
Substandard [Member] | Bankcard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	121	186
Substandard [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	1,226	978
Substandard [Member] | Owner-Occupied [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	61,245	65,376
Substandard [Member] | Nonowner-Occupied [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	103,036	80,695
Substandard [Member] | Construction & Land Development [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	79,708	86,005
Doubtful [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	0	0
Doubtful [Member] | Other Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	2,796	3,922
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	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Construction & Land Development [Member]
Financing Receivable, Impaired [Line Items]
Impaired Loans, Recorded Investment, With no related allowance recorded	$ 48,320		$ 52,279
Impaired Loans, Unpaid Principal Balance, With no related allowance recorded	53,084		59,691
Impaired Loans, Recorded Investment, With an allowance recorded	2,015		1,383
Impaired Loans, Unpaid Principal Balance, With an allowance recorded	4,664		1,383
Impaired Loans, Related Allowance	217		229
Impaired Loans, Recorded Investment	50,335		53,662
Impaired Loans, Unpaid Principal Balance	57,748		61,074
Impaired Loans, Related Allowance	217		229
Impaired Loans, Average Recorded Investment, With no related allowance recorded	50,300	$ 35,949
Impaired Loans, Interest Income Recognized, With no related allowance recorded	103	76
Impaired Loans, Average Recorded Investment, With an allowance recorded	1,699	4,161
Impaired Loans, Interest Income Recognized, With an allowance recorded	20	21
Impaired Loans, Average Recorded Investment	51,999	40,110
Impaired Loans, Interest Income Recognized	123	97
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	28	36
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	75,776		78,117
Impaired Loans, Unpaid Principal Balance, With no related allowance recorded	75,941		78,419
Impaired Loans, Recorded Investment, With an allowance recorded	5,873		9,132
Impaired Loans, Unpaid Principal Balance, With an allowance recorded	5,873		9,132
Impaired Loans, Related Allowance	1,075		2,251
Impaired Loans, Recorded Investment	81,649		87,249
Impaired Loans, Unpaid Principal Balance	81,814		87,551
Impaired Loans, Related Allowance	1,075		2,251
Impaired Loans, Average Recorded Investment, With no related allowance recorded	76,947	55,857
Impaired Loans, Interest Income Recognized, With no related allowance recorded	377	421
Impaired Loans, Average Recorded Investment, With an allowance recorded	7,502	7,663
Impaired Loans, Interest Income Recognized, With an allowance recorded	25	137
Impaired Loans, Average Recorded Investment	84,449	63,520
Impaired Loans, Interest Income Recognized	402	558
Commercial Real Estate [Member] | Nonowner-Occupied [Member]
Financing Receivable, Impaired [Line Items]
Impaired Loans, Recorded Investment, With no related allowance recorded	117,589		134,136
Impaired Loans, Unpaid Principal Balance, With no related allowance recorded	117,648		134,195
Impaired Loans, Recorded Investment, With an allowance recorded	8,543		7,797
Impaired Loans, Unpaid Principal Balance, With an allowance recorded	8,543		7,797
Impaired Loans, Related Allowance	1,471		1,592
Impaired Loans, Recorded Investment	126,132		141,933
Impaired Loans, Unpaid Principal Balance	126,191		141,992
Impaired Loans, Related Allowance	1,471		1,592
Impaired Loans, Average Recorded Investment, With no related allowance recorded	125,863	82,528
Impaired Loans, Interest Income Recognized, With no related allowance recorded	120	117
Impaired Loans, Average Recorded Investment, With an allowance recorded	8,170	16,096
Impaired Loans, Interest Income Recognized, With an allowance recorded	59	83
Impaired Loans, Average Recorded Investment	134,033	98,624
Impaired Loans, Interest Income Recognized	179	200
Other Commercial [Member]
Financing Receivable, Impaired [Line Items]
Impaired Loans, Recorded Investment, With no related allowance recorded	52,394		46,993
Impaired Loans, Unpaid Principal Balance, With no related allowance recorded	54,953		49,552
Impaired Loans, Recorded Investment, With an allowance recorded	48,082		60,512
Impaired Loans, Unpaid Principal Balance, With an allowance recorded	55,905		70,396
Impaired Loans, Related Allowance	16,180		16,721
Impaired Loans, Recorded Investment	100,476		107,505
Impaired Loans, Unpaid Principal Balance	110,858		119,948
Impaired Loans, Related Allowance	16,180		16,721
Impaired Loans, Average Recorded Investment, With no related allowance recorded	49,693	49,286
Impaired Loans, Interest Income Recognized, With no related allowance recorded	206	220
Impaired Loans, Average Recorded Investment, With an allowance recorded	54,297	58,824
Impaired Loans, Interest Income Recognized, With an allowance recorded	19	370
Impaired Loans, Average Recorded Investment	103,990	108,110
Impaired Loans, Interest Income Recognized	225	590
Residential Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired Loans, Recorded Investment, With no related allowance recorded	24,125		26,751
Impaired Loans, Unpaid Principal Balance, With no related allowance recorded	24,787		28,202
Impaired Loans, Recorded Investment, With an allowance recorded	11,887		9,813
Impaired Loans, Unpaid Principal Balance, With an allowance recorded	13,438		10,418
Impaired Loans, Related Allowance	1,742		1,552
Impaired Loans, Recorded Investment	36,012		36,564
Impaired Loans, Unpaid Principal Balance	38,225		38,620
Impaired Loans, Related Allowance	1,742		1,552
Impaired Loans, Average Recorded Investment, With no related allowance recorded	25,437	21,814
Impaired Loans, Interest Income Recognized, With no related allowance recorded	83	41
Impaired Loans, Average Recorded Investment, With an allowance recorded	10,850	13,113
Impaired Loans, Interest Income Recognized, With an allowance recorded	0	8
Impaired Loans, Average Recorded Investment	36,287	34,927
Impaired Loans, Interest Income Recognized	83	49
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	42		15
Impaired Loans, Unpaid Principal Balance, With no related allowance recorded	42		15
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	42		15
Impaired Loans, Unpaid Principal Balance	42		15
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	28	36
Impaired Loans, Interest Income Recognized	$ 0	$ 0

Allowance for Credit Losses - A

Allowance for Credit Losses - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2017
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			30 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
Reversal of provision for loan losses related to loans acquired	$ 1,279	$ 367
Reserve for lending-related commitments	$ 755	$ 679	$ 679
Closed-End Retail Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Number of days delinquent from contractual due date			12 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
	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses Beginning balance	$ 76,627	$ 72,771
Charge-offs	5,858	32,863
Recoveries	706	8,313
Provision	5,178	28,406
Allowance for Loan Losses Ending balance	76,653	76,627
Allowance for Loan Losses, individually evaluated for impairment	20,685	22,345
Allowance for Loan Losses, collectively evaluated for impairment	55,968	54,282
Financing receivables	12,998,435	13,027,337
Financing receivables, individually evaluated for impairment	158,549	168,524
Financing receivables, collectively evaluated for impairment	12,650,211	12,648,292
Loans Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses	0	0
Financing receivables	189,675	210,521
Construction & Land Development [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses Beginning balance	7,187	10,606
Charge-offs	460	3,337
Recoveries	2	726
Provision	(300)	(808)
Allowance for Loan Losses Ending balance	6,429	7,187
Allowance for Loan Losses, individually evaluated for impairment	217	229
Allowance for Loan Losses, collectively evaluated for impairment	6,212	6,958
Financing receivables	1,433,125	1,504,907
Financing receivables, individually evaluated for impairment	16,909	16,921
Financing receivables, collectively evaluated for impairment	1,391,948	1,461,206
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
Financing receivables	24,268	26,780
Allowance for Estimated Imprecision [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses Beginning balance	73	347
Charge-offs	0	0
Recoveries	0	0
Provision	97	(274)
Allowance for Loan Losses Ending balance	170	73
Allowance for Loan Losses, individually evaluated for impairment	0	0
Allowance for Loan Losses, collectively evaluated for impairment	170	73
Financing receivables	0	0
Financing receivables, individually evaluated for impairment	0	0
Financing receivables, collectively evaluated for impairment	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
Financing receivables	0	0
Commercial Real Estate [Member] | Owner-Occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses Beginning balance	5,401	5,273
Charge-offs	1,015	2,246
Recoveries	55	2,599
Provision	(722)	(225)
Allowance for Loan Losses Ending balance	3,719	5,401
Allowance for Loan Losses, individually evaluated for impairment	1,075	2,251
Allowance for Loan Losses, collectively evaluated for impairment	2,644	3,150
Financing receivables	1,366,980	1,361,629
Financing receivables, individually evaluated for impairment	33,438	36,721
Financing receivables, collectively evaluated for impairment	1,301,725	1,291,379
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
Financing receivables	31,817	33,529
Commercial Real Estate [Member] | Nonowner-Occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses Beginning balance	6,369	6,883
Charge-offs	0	296
Recoveries	136	244
Provision	269	(462)
Allowance for Loan Losses Ending balance	6,774	6,369
Allowance for Loan Losses, individually evaluated for impairment	1,471	1,592
Allowance for Loan Losses, collectively evaluated for impairment	5,303	4,777
Financing receivables	4,426,776	4,451,298
Financing receivables, individually evaluated for impairment	22,868	21,851
Financing receivables, collectively evaluated for impairment	4,310,587	4,320,997
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
Financing receivables	93,321	108,450
Other Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses Beginning balance	45,189	33,087
Charge-offs	2,868	21,189
Recoveries	106	3,395
Provision	4,490	29,896
Allowance for Loan Losses Ending balance	46,917	45,189
Allowance for Loan Losses, individually evaluated for impairment	16,180	16,721
Allowance for Loan Losses, collectively evaluated for impairment	30,737	28,468
Financing receivables	1,952,322	1,998,979
Financing receivables, individually evaluated for impairment	71,478	78,715
Financing receivables, collectively evaluated for impairment	1,853,603	1,892,706
Other Commercial [Member] | Loans Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses	0	0
Financing receivables	27,241	27,558
Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses Beginning balance	9,927	13,770
Charge-offs	910	2,973
Recoveries	264	601
Provision	972	(1,471)
Allowance for Loan Losses Ending balance	10,253	9,927
Allowance for Loan Losses, individually evaluated for impairment	1,742	1,552
Allowance for Loan Losses, collectively evaluated for impairment	8,511	8,375
Financing receivables	3,065,990	2,996,171
Financing receivables, individually evaluated for impairment	13,856	14,316
Financing receivables, collectively evaluated for impairment	3,039,123	2,967,666
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
Financing receivables	13,011	14,189
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses Beginning balance	2,481	2,805
Charge-offs	605	2,822
Recoveries	143	748
Provision	372	1,750
Allowance for Loan Losses Ending balance	2,391	2,481
Allowance for Loan Losses, individually evaluated for impairment	0	0
Allowance for Loan Losses, collectively evaluated for impairment	2,391	2,481
Financing receivables	753,242	714,353
Financing receivables, individually evaluated for impairment	0	0
Financing receivables, collectively evaluated for impairment	753,225	714,338
Consumer [Member] | Loans Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses	0	0
Financing receivables	$ 17	$ 15

Intangible Assets- Summary of I

Intangible Assets- Summary of Intangible Assets (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Goodwill not subject to amortization	$ 1,478,580	$ 1,478,380
Core Deposit Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	98,359	98,359
Accumulated Amortization	(56,463)	(54,453)
George Mason Trade Name Intangible [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,080	1,080
Community Banking [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill not subject to amortization	1,473,265	1,473,265
Community Banking [Member] | Core Deposit Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	98,359	98,359
Accumulated Amortization	(56,463)	(54,453)
Community Banking [Member] | George Mason Trade Name Intangible [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	0	0
Mortgage Banking [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill not subject to amortization	5,315	5,115
Mortgage Banking [Member] | Core Deposit Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	0	0
Accumulated Amortization	0	0
Mortgage Banking [Member] | George Mason Trade Name Intangible [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 1,080	$ 1,080

Intangible Assets - Reconciliat

Intangible Assets - Reconciliation of Goodwill (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)
Goodwill [Line Items]
Goodwill, Beginning Balance	$ 1,478,380
Goodwill, Ending Balance	1,478,580
Cardinal Financial Corporation [Member]
Goodwill [Line Items]
Addition to goodwill	200
Community Banking [Member]
Goodwill [Line Items]
Goodwill, Beginning Balance	1,473,265
Goodwill, Ending Balance	1,473,265
Community Banking [Member] | Cardinal Financial Corporation [Member]
Goodwill [Line Items]
Addition to goodwill	0
Mortgage Banking [Member]
Goodwill [Line Items]
Goodwill, Beginning Balance	5,115
Goodwill, Ending Balance	5,315
Mortgage Banking [Member] | Cardinal Financial Corporation [Member]
Goodwill [Line Items]
Addition to goodwill	$ 200

Intangible Assets - Schedule of

Intangible Assets - Schedule of Anticipated Amortization Expense (Detail) $ in Thousands	Mar. 31, 2018USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
2,018	$ 8,039
2,019	7,016
2,020	6,309
2,021	5,369
2022 and thereafter	$ 17,173

Short-Term Borrowings - Additio

Short-Term Borrowings - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Short-term Debt [Line Items]
Unused lines of credit	$ 230,000,000
Federal funds purchased	17,615,000	$ 16,235,000
Repurchase agreements	250,771,000
Wholesale REPO	$ 50,000,000
Maturity date of wholesale REPO	2018-05
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

Long-Term Borrowings - Addition

Long-Term Borrowings - Additional Information (Detail)	3 Months Ended	12 Months Ended
	Mar. 31, 2018USD ($)Trust	Dec. 31, 2017USD ($)
Debt Instrument [Line Items]
Unused borrowing amount	$ 4,213,640,000
FHLB advances	$ 1,060,948,000	$ 1,271,531,000
FHLB advances, weighted-average interest rate	1.84%
FHLB advances, maximum maturity period	7 years
Number of statutory business trusts | Trust	14
Outstanding balances of debentures	$ 233,961,000	$ 242,446,000
Maximum time to defer payment of interest on subordinate debt		5 years
Maximum [Member]
Debt Instrument [Line Items]
Risk based assets	$ 15,000,000,000
Capital Securities [Member]
Debt Instrument [Line Items]
Number of statutory business trusts | Trust	14

Long -Term Borrowings - Schedul

Long -Term Borrowings - Schedule of Maturities of Long-term Borrowings (Detail) $ in Thousands	Mar. 31, 2018USD ($)
Debt Disclosure [Abstract]
2,018	$ 746,863
2,019	187,516
2,020	42,013
2,021	52,693
2022 and thereafter	31,863
Total	$ 1,060,948

Commitments and Contingent Li77

Commitments and Contingent Liabilities - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Loss Contingencies [Line Items]
Loan commitments outstanding	$ 4,001,212,000	$ 4,224,719,000
Loan commitments expiry period	1 year
George Mason [Member]
Loss Contingencies [Line Items]
Reserve for possible losses due to the repurchase of loans previously sold to investors	$ 516,000
Commitments to Extend Credit [Member] | George Mason [Member] | Short-term Contract with Customer [Member]
Loss Contingencies [Line Items]
Additional commitments to extend credit	400,836,000
Commercial Letters of Credit [Member]
Loss Contingencies [Line Items]
Letters of credit issued	0	0
Standby Letters of Credit [Member]
Loss Contingencies [Line Items]
Letters of credit issued	$ 142,532,000	$ 147,017,000

Derivative Financial Instrume78

Derivative Financial Instruments - Schedule of Notional Amount and Fair Value Derivative Financial Instruments (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Derivative [Line Items]
Asset derivatives, notional amount	$ 299,721	$ 251,721
Asset derivatives designated as hedging instruments	2,514	538
Liability derivatives, notional amount	258,000	255,295
Asset derivatives not designated as hedging instruments	5,683	4,561
Total asset derivatives	8,197	5,099
Liability derivatives designated as hedging instruments	0	165
Liability derivatives not designated as hedging instruments	762	312
Total liability derivatives	762	477
Designated as Hedging Instrument [Member]
Derivative [Line Items]
Asset derivatives, notional amount	88,679	71,831
Liability derivatives, notional amount	0	18,795
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Asset derivatives, notional amount	211,042	179,890
Liability derivatives, notional amount	258,000	236,500
Other Assets [Member] | Interest Rate Lock Commitments [Member]
Derivative [Line Items]
Asset derivatives not designated as hedging instruments	5,610	4,559
Other Assets [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Lock Commitments [Member]
Derivative [Line Items]
Asset derivatives, notional amount	195,330	148,866
Other Liabilities [Member] | TBA Mortgage Backed Securities [Member]
Derivative [Line Items]
Liability derivatives not designated as hedging instruments	762	312
Other Liabilities [Member] | Interest Rate Lock Commitments [Member]
Derivative [Line Items]
Liability derivatives not designated as hedging instruments	0	0
Other Liabilities [Member] | Not Designated as Hedging Instrument [Member] | TBA Mortgage Backed Securities [Member]
Derivative [Line Items]
Liability derivatives, notional amount	258,000	236,500
Other Liabilities [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Lock Commitments [Member]
Derivative [Line Items]
Liability derivatives, notional amount	0	0
Interest Rate Swap Contracts [Member] | Other Assets [Member] | Fair Value Hedging [Member] | Hedged Commercial Loans [Member]
Derivative [Line Items]
Asset derivatives designated as hedging instruments	2,514	538
Interest Rate Swap Contracts [Member] | Other Assets [Member] | Fair Value Hedging [Member] | Designated as Hedging Instrument [Member] | Hedged Commercial Loans [Member]
Derivative [Line Items]
Asset derivatives, notional amount	88,679	71,831
Interest Rate Swap Contracts [Member] | Other Liabilities [Member] | Fair Value Hedging [Member] | Hedged Commercial Loans [Member]
Derivative [Line Items]
Liability derivatives designated as hedging instruments	0	165
Interest Rate Swap Contracts [Member] | Other Liabilities [Member] | Fair Value Hedging [Member] | Designated as Hedging Instrument [Member] | Hedged Commercial Loans [Member]
Derivative [Line Items]
Liability derivatives, notional amount	0	18,795
Forward Loan Sale Commitments [Member] | Other Assets [Member]
Derivative [Line Items]
Asset derivatives not designated as hedging instruments	73	2
Forward Loan Sale Commitments [Member] | Other Assets [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Asset derivatives, notional amount	$ 15,712	$ 31,024

Derivative Financial Instrume79

Derivative Financial Instruments - Schedule of Derivative Financial Instruments on Statements of Income (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Derivative [Line Items]
Derivatives in hedging relationships	$ (1,688)	$ (158)
Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivatives in hedging relationships	(42)	(158)
Designated as Hedging Instrument [Member] | Interest Income/ (Expense) [Member] | Interest Rate Swap Contracts [Member] | Fair Value Hedging [Member]
Derivative [Line Items]
Derivatives in hedging relationships	(42)	(158)
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivatives not designated as hedging instruments	(1,646)	0
Not Designated as Hedging Instrument [Member] | Income from Mortgage Banking Activities [Member] | TBA Mortgage Backed Securities [Member]
Derivative [Line Items]
Derivatives not designated as hedging instruments	450	0
Not Designated as Hedging Instrument [Member] | Income from Mortgage Banking Activities [Member] | Interest Rate Lock Commitments [Member]
Derivative [Line Items]
Derivatives not designated as hedging instruments	1,269	0
Not Designated as Hedging Instrument [Member] | Income from Mortgage Banking Activities [Member] | Forward Loan Sale Commitments [Member]
Derivative [Line Items]
Derivatives not designated as hedging instruments	$ 73	$ 0

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Mar. 31, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
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
Loans Held For Sale [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Sales price of loans held for sale increase percentage	0.19%
Loans Held For Sale [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Sales price of loans held for sale increase percentage	0.68%
Loans Held For Sale [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Sales price of loans held for sale increase percentage	0.36%
Derivatives [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Sales price of loans held for sale increase percentage		0.19%
Derivatives [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Sales price of loans held for sale increase percentage		0.68%
Derivatives [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Sales price of loans held for sale increase percentage		0.36%

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Financial Assets and Liabilities Measured at Fair Value (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale equity securities	$ 0	$ 9,878
Total available for sale securities	2,085,111	1,888,756
Loans held for sale	193,915	265,955
Derivative financial assets	8,197	5,099
Derivative financial liabilities	762	477
Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale equity securities		9,878
Total available for sale securities	2,085,111	1,888,756
Loans held for sale	192,673	263,308
Derivative financial assets	8,197	5,099
Derivative financial liabilities	762	477
Available for sale debt securities		1,878,878
Fair Value, Measurements, Recurring [Member] | Interest Rate Lock Commitments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative financial assets	5,610	4,561
Fair Value, Measurements, Recurring [Member] | TBA Mortgage Backed Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative financial liabilities	762	312
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	163,106	114,758
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]
Total available for sale securities	163,106
Available for sale debt securities		114,758
State and Political Subdivisions [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	293,712	303,869
State and Political Subdivisions [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	293,712
Available for sale debt securities		303,869
Residential Mortgage-Backed Securities, Agency [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	915,547	814,593
Residential Mortgage-Backed Securities, Agency [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	915,547
Available for sale debt securities		814,593
Residential Mortgage-Backed Securities, Non-agency [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	5,166	5,512
Residential Mortgage-Backed Securities, Non-agency [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	5,166
Available for sale debt securities		5,512
Asset-Backed Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	146,584	109,970
Asset-Backed Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	146,584
Available for sale debt securities		109,970
Commercial Mortgage-Backed Securities, Agency [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	476,779	454,857
Commercial Mortgage-Backed Securities, Agency [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	476,779
Available for sale debt securities		454,857
Trust Preferred Collateralized Debt Obligations [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	8,064	34,269
Trust Preferred Collateralized Debt Obligations [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	8,064
Available for sale debt securities		34,269
Single Issue Trust Preferred Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	13,146	12,560
Single Issue Trust Preferred Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	13,146
Available for sale debt securities		12,560
Corporate Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	63,007	28,490
Corporate Bonds [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	63,007
Available for sale debt securities		28,490
Financial Services Industry [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale equity securities		3,545
Equity securities	485
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
Equity securities	4,668
Marketable Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities		9,878
Marketable Equity Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities	11,160
Interest Rate Swap Contracts [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative financial assets	2,514	538
Derivative financial liabilities		165
Forward Loan Sale Commitments [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative financial assets	73
Equity Mutual Funds [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale equity securities		6,332
Equity securities	6,007
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	7,036	6,664
Loans held for sale	0	0
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 equity securities		6,664
Total available for sale securities	7,036	6,664
Loans held for sale	0	0
Derivative financial assets	0	0
Derivative financial liabilities	0	0
Available for sale debt securities		0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate Lock Commitments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative financial assets	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fair Value, Measurements, Recurring [Member] | TBA Mortgage Backed Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative financial liabilities	0	0
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]
Total available for sale securities	0
Available for sale debt securities		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]
Total available for sale securities	0
Available for sale debt securities		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]
Total available for sale securities	0
Available for sale debt securities		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]
Total available for sale securities	0
Available for sale debt securities		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]
Total available for sale securities	0
Available for sale debt securities		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]
Total available for sale securities	0
Available for sale debt securities		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]
Total available for sale securities	0
Available for sale debt securities		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]
Total available for sale securities	0
Available for sale debt securities		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]
Total available for sale securities	7,036
Available for sale debt securities		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		331
Equity securities	485
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
Equity securities	4,668
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Marketable Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities	11,160
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Marketable Equity Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities	11,160
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Interest Rate Swap 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
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Forward Loan Sale Commitments [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative financial assets	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		6,332
Equity securities	6,007
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	2,070,011	1,847,823
Loans held for sale	1,242	2,647
Derivative financial assets	2,587	540
Derivative financial liabilities	762	477
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 equity securities		3,214
Total available for sale securities	2,070,011	1,847,823
Loans held for sale	0	0
Derivative financial assets	2,587	540
Derivative financial liabilities	762	477
Available for sale debt securities		1,844,609
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate Lock Commitments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative financial assets	0	2
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member] | TBA Mortgage Backed Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative financial liabilities	762	312
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]
Total available for sale securities	163,106
Available for sale debt securities		114,758
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]
Total available for sale securities	293,712
Available for sale debt securities		303,869
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]
Total available for sale securities	915,547
Available for sale debt securities		814,593
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]
Total available for sale securities	5,166
Available for sale debt securities		5,512
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]
Total available for sale securities	146,584
Available for sale debt securities		109,970
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]
Total available for sale securities	476,779
Available for sale debt securities		454,857
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]
Total available for sale securities	0
Available for sale debt securities		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]
Total available for sale securities	13,146
Available for sale debt securities		12,560
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]
Total available for sale securities	55,971
Available for sale debt securities		28,490
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		3,214
Equity securities	0
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
Equity securities	0
Significant Other Observable Inputs (Level 2) [Member] | Marketable Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities	0
Significant Other Observable Inputs (Level 2) [Member] | Marketable Equity Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities	0
Significant Other Observable Inputs (Level 2) [Member] | Interest Rate Swap Contracts [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative financial assets	2,514	538
Derivative financial liabilities		165
Significant Other Observable Inputs (Level 2) [Member] | Forward Loan Sale Commitments [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative financial assets	73
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
Equity securities	0
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	8,064	34,269
Loans held for sale	192,673	263,308
Derivative financial assets	5,610	4,559
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 equity securities		0
Total available for sale securities	8,064	34,269
Loans held for sale	192,673	263,308
Derivative financial assets	5,610	4,559
Derivative financial liabilities	0	0
Available for sale debt securities		34,269
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate Lock Commitments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative financial assets	5,610	4,559
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member] | TBA Mortgage Backed Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative financial liabilities	0	0
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]
Total available for sale securities	0
Available for sale debt securities		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]
Total available for sale securities	0
Available for sale debt securities		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]
Total available for sale securities	0
Available for sale debt securities		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]
Total available for sale securities	0
Available for sale debt securities		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]
Total available for sale securities	0
Available for sale debt securities		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]
Total available for sale securities	0
Available for sale debt securities		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]
Total available for sale securities	8,064
Available for sale debt securities		34,269
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]
Total available for sale securities	0
Available for sale debt securities		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]
Total available for sale securities	0
Available for sale debt securities		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
Equity securities	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
Equity securities	0
Significant Unobservable Inputs (Level 3) [Member] | Marketable Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities	0
Significant Unobservable Inputs (Level 3) [Member] | Marketable Equity Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities	0
Significant Unobservable Inputs (Level 3) [Member] | Interest Rate Swap 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
Significant Unobservable Inputs (Level 3) [Member] | Forward Loan Sale Commitments [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative financial assets	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
Equity securities	$ 0

Fair Value Measurements - Sch82

Fair Value Measurements - Schedule of Additional Information about Financial Assets and Liabilities Measured at Fair Value Utilized Level 3 (Detail) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Trust Preferred Collateralized Debt Obligations [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Balance, beginning of period	$ 34,269	$ 33,552
Included in earnings (or changes in net assets)	28	9
Included in other comprehensive income	217	8,757
Purchases, issuances, and settlements	0	0
Sales	(26,450)	(8,049)
Transfers in and/or out of Level 3	0	0
Balance, end of period	8,064	34,269
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
Loans Held For Sale [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Balance, beginning of period	263,308	0
Included in earnings (or changes in net assets)	(14,883)	(58,132)
Acquired in Cardinal merger	0	271,301
Originations	573,732	2,333,927
Sales	(631,834)	(2,408,945)
Transfers in and/or out of Level 3	(27,416)	8,893
Balance, end of period	192,673	263,308
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
Interest Rate Lock Commitments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Balance, beginning of period	4,559	0
Acquired in Cardinal merger	0	10,393
Transfers in and/or out of Level 3	1,051	(5,834)
Balance, end of period	5,610	4,559
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 Value Measurements - Sch83

Fair Value Measurements - Schedule of Changes in Fair Value Included in Earnings of Financial Instruments for which Fair Value Option has been Elected (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Mortgage Banking [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Income from mortgage banking activities	$ (1,719)	$ 0

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Difference Between Aggregate Fair Value and Remaining Contractual Principal Outstanding for Financial Instruments for which Fair Value Option has been Elected (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Loans held for sale, unpaid principal balance	$ 188,998	$ 257,674
Loans held for sale, fair value	192,673	263,308
Loans held for sale, fair value over/(under) unpaid principal balance	$ 3,675	$ 5,634

Fair Value Measurements - Sum85

Fair Value Measurements - Summary of Financial Assets Measured at Fair Value on Nonrecurring Basis (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held for sale	$ 0	$ 14
YTD Losses, Impaired Loans	1,376	12,291
YTD Losses, OREO	585	4,200
Loans held for sale	192,673	263,308
OREO	22,778	24,348
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held for sale	1,242	2,647
Impaired Loans	76,400	88,637
OREO	22,778	24,348
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held for sale	0	0
Impaired Loans	0	0
OREO	0	0
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held for sale	1,242	2,647
Impaired Loans	56,632	70,950
OREO	22,702	24,151
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held for sale	0	0
Impaired Loans	19,768	17,687
OREO	$ 76	$ 197

Fair Value Measurements - Sum86

Fair Value Measurements - Summary of Estimated Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 1,139,170	$ 1,666,167	$ 1,667,328	$ 1,434,527
Securities available for sale	2,085,111	1,888,756
Securities held to maturity	20,405	20,428
Other securities	152,287	162,461
Loans held for sale	193,915	265,955
Loans	12,984,417	13,011,421
Derivative financial assets	8,197	5,099
Deposits	13,646,168	13,830,591
Derivative financial liabilities	762	477
Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	1,139,170	1,666,167
Securities available for sale	2,085,111	1,888,756
Securities held to maturity	20,405	20,428
Other securities	152,287	162,461
Loans held for sale	193,915	265,955
Loans	12,907,764	12,934,794
Derivative financial assets	8,197	5,099
Deposits	13,646,168	13,830,591
Short-term borrowings	218,386	477,587
Long-term borrowings	1,344,909	1,363,977
Derivative financial liabilities	762	477
Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	1,139,170	1,666,167
Securities available for sale	2,085,111	1,888,756
Securities held to maturity	20,006	20,018
Other securities	144,673	154,338
Loans held for sale	193,915	265,955
Loans	12,207,257	12,437,797
Derivative financial assets	8,197	5,099
Deposits	13,611,626	14,024,720
Short-term borrowings	218,386	477,587
Long-term borrowings	1,317,352	1,338,754
Derivative financial liabilities	762	477
Marketable Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities available for sale		9,878
Marketable Equity Securities [Member] | Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities	11,160
Marketable Equity Securities [Member] | Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities	11,160
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	7,036	6,664
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
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Marketable Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities	11,160
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	1,139,170	1,666,167
Securities available for sale	2,070,011	1,847,823
Securities held to maturity	16,986	16,998
Other securities	0	0
Loans held for sale	1,242	2,647
Loans	0	0
Derivative financial assets	2,587	540
Deposits	13,611,626	14,024,720
Short-term borrowings	218,386	477,587
Long-term borrowings	1,317,352	1,338,754
Derivative financial liabilities	762	477
Significant Other Observable Inputs (Level 2) [Member] | Marketable Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities	0
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	8,064	34,269
Securities held to maturity	3,020	3,020
Other securities	144,673	154,338
Loans held for sale	192,673	263,308
Loans	12,207,257	12,437,797
Derivative financial assets	5,610	4,559
Deposits	0	0
Short-term borrowings	0	0
Long-term borrowings	0	0
Derivative financial liabilities	0	$ 0
Significant Unobservable Inputs (Level 3) [Member] | Marketable Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities	$ 0

Stock Based Compensation - Addi

Stock Based Compensation - Additional Information (Detail) - USD ($) $ in Thousands	May 18, 2016	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Authorized shares of stock, option plan, maximum	1,700,000,000
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
Number of Options granted		276,192
Recognition of compensation expense		$ 968	$ 682
Number of share available for grant for prior plans		0
Maximum term for awards granted (years)		10 years
Shares issued related stock option exercises		15,043	22,523
Total intrinsic value of options exercised		$ 246	$ 452
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares granted		97,004
Vesting period		4 years

Stock Based Compensation - Summ

Stock Based Compensation - Summary of Stock Option Plans (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Disclosure Stock Based Compensation Stock Option Plan [Abstract]
Shares, Outstanding, Beginning balance	1,558,438
Shares, Granted	276,192
Shares, Exercised	(15,043)	(22,523)
Shares, Forfeited or expired	(2,438)
Shares, Outstanding, Ending balance	1,817,149
Shares, Exercisable at March 31, 2018	1,222,889
Aggregate Intrinsic Value, Outstanding at March 31, 2018	$ 9,046,231
Aggregate Intrinsic Value, Exercisable at March 31, 2018	$ 9,027,432
Weighted Average Remaining Contractual Term, Outstanding at March 31, 2018	6 years 3 months 19 days
Weighted Average Remaining Contractual Term, Exercisable at March 31, 2018	4 years 10 months 25 days
Weighted Average Exercise Price, Outstanding, Beginning balance	$ 31.09
Weighted Average Exercise Price, Granted	37.60
Weighted Average Exercise Price, Exercised	19.97
Weighted Average Exercise Price, Forfeited or expired	39.16
Weighted Average Exercise Price, Outstanding, Ending balance	32.16
Weighted Average Exercise Price, Exercisable	$ 28.57

Stock Based Compensation - Stat

Stock Based Compensation - Status of United's Nonvested Stock Option Awards (Detail)	3 Months Ended
	Mar. 31, 2018$ / sharesshares
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Shares, Nonvested, Beginning balance | shares	507,871
Shares, Granted | shares	276,192
Shares, Vested | shares	(187,365)
Shares, Forfeited or expired | shares	(2,438)
Shares, Nonvested, Ending balance | shares	594,260
Weighted-Average Grant Date Fair Value Per Share, Nonvested Beginning balance | $ / shares	$ 7.89
Weighted-Average Grant Date Fair Value Per Share, Granted | $ / shares	7.56
Weighted-Average Grant Date Fair Value Per Share, Vested | $ / shares	7.52
Weighted-Average Grant Date Fair Value Per Share, Forfeited or expired | $ / shares	7.75
Weighted-Average Grant Date Fair Value Per Share, Nonvested Ending balance | $ / shares	$ 7.85

Stock Based Compensation - Chan

Stock Based Compensation - Changes to United's Restricted Common Shares (Detail) - Restricted Stock [Member]	3 Months Ended
	Mar. 31, 2018$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Outstanding, Beginning balance | shares	170,496
Shares, Granted | shares	97,004
Shares, Vested | shares	(62,285)
Shares, Forfeited | shares	(683)
Number of Shares, Outstanding, Ending balance | shares	204,532
Weighted-Average Grant Date Fair Value Per Share, Outstanding, Beginning balance | $ / shares	$ 40.05
Weighted-Average Grant Date Fair Value Per Share, Granted | $ / shares	37.60
Weighted-Average Grant Date Fair Value Per Share, Vested | $ / shares	37.59
Weighted-Average Grant Date Fair Value Per Share, Forfeited | $ / shares	39.15
Weighted-Average Grant Date Fair Value Per Share, Outstanding, Ending balance | $ / shares	$ 39.64

Employee Benefit Plans - Additi

Employee Benefit Plans - Additional Information (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)
Retirement Benefits [Abstract]
Employer discretionary contribution amount	$ 7,000
Unrecognized actuarial gains (losses), before tax	56,222
Unrecognized actuarial gains (losses), net of tax	35,420
Amortization expected to be recognized	4,653
Amortization expected to be recognized, net of tax	$ 2,932

Employee Benefit Plans - Net Pe

Employee Benefit Plans - Net Periodic Pension Cost (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 658	$ 562
Interest cost	1,295	1,265
Expected return on plan assets	(2,522)	(2,027)
Amortization of transition asset	0	0
Recognized net actuarial loss	1,149	1,087
Amortization of prior service cost	0	0
Net periodic pension (benefit) cost	$ 580	$ 887
Weighted-Average Assumptions:
Discount rate	3.83%	4.49%
Expected return on assets	7.00%	7.00%
Rate of compensation increase	3.00%	3.00%
Prior to Age 45 [Member]
Weighted-Average Assumptions:
Rate of compensation increase	3.50%	3.50%

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Accrued interest related to uncertain tax positions	$ 695	$ 589
Federal corporate tax rate	21.00%		35.00%
Deferred tax expense due to the Tax Act	$ 37,732
Effective tax rate	22.48%	34.25%

Comprehensive Income - Componen

Comprehensive Income - Components of Total Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Net income	$ 61,706	$ 38,809
AFS securities with OTTI charges during the period	0	(44)
Related income tax effect	0	16
Less: OTTI charges recognized in net income	0	44
Related income tax benefit	0	(16)
Reclassification of previous noncredit OTTI to credit OTTI	0	0
Related income tax benefit	0	0
Net unrealized gain (loss) on AFS securities with OTTI	0	0
Change in net unrealized gain on AFS securities arising during the period	(22,017)	5,576
Related income tax effect	5,130	(2,063)
Net reclassification adjustment for losses (gains) included in net income	149	(214)
Related income tax (benefit) expense	(35)	79
Total AFS securities - all other	(16,773)	3,378
Net effect of AFS securities on other comprehensive income	(16,773)	3,378
Accretion on the unrealized loss for securities transferred from AFS to the HTM investment portfolio prior to call or maturity	2	2
Related income tax expense	(1)	(1)
Net effect of HTM securities on other comprehensive income	1	1
Pension plan:
Recognized net actuarial loss	1,149	1,087
Related income tax benefit	(416)	(392)
Net effect of change in pension plan asset on other comprehensive income	733	695
Net current-period other comprehensive income, net of tax	(16,039)	4,074
Comprehensive income, net of tax	$ 45,667	$ 42,883

Comprehensive Income - Compon95

Comprehensive Income - Components of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 3,240,530
Cumulative effect of adopting Accounting Standard Update 2016-01	0
Reclass due to adopting Accounting Standard Update 2018-02	0
Net current-period other comprehensive income, net of tax	(16,039)	$ 4,074
Ending Balance	3,251,313
Pension Plan [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(35,775)
Reclass due to adopting Accounting Standard Update 2018-02	(4,721)
Other comprehensive income before reclassification	0
Amounts reclassified from accumulated other comprehensive income	733
Net current-period other comprehensive income, net of tax	733
Ending Balance	(39,763)
Unrealized Gains/Losses on AFS Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(6,204)
Cumulative effect of adopting Accounting Standard Update 2016-01	(136)
Reclass due to adopting Accounting Standard Update 2018-02	(1,632)
Other comprehensive income before reclassification	(16,887)
Amounts reclassified from accumulated other comprehensive income	114
Net current-period other comprehensive income, net of tax	(16,773)
Ending Balance	(24,745)
Accumulated Unrealized Loss On Securities Available For Sale Transferred To Held To Maturity [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(46)
Other comprehensive income before reclassification	1
Amounts reclassified from accumulated other comprehensive income	0
Net current-period other comprehensive income, net of tax	1
Ending Balance	(45)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(42,025)
Cumulative effect of adopting Accounting Standard Update 2016-01	(136)
Reclass due to adopting Accounting Standard Update 2018-02	(6,353)
Other comprehensive income before reclassification	(16,886)
Amounts reclassified from accumulated other comprehensive income	847
Net current-period other comprehensive income, net of tax	(16,039)
Ending Balance	$ (64,553)

Comprehensive Income - Reclassi

Comprehensive Income - Reclassifications Out of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Available for sale ("AFS") securities:
Income before income taxes	$ 79,605	$ 59,025
Related income tax effect	(17,899)	(20,216)
Net income	61,706	38,809
Pension plan:
Income before income taxes	79,605	59,025
Related income tax effect	(17,899)	(20,216)
Net income	61,706	$ 38,809
Reclassification out of Accumulated Other Comprehensive Income [Member]
Available for sale ("AFS") securities:
Net income	847
Pension plan:
Net income	847
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	0
Net reclassification adjustment for losses (gains) included in net income	149
Income before income taxes	149
Related income tax effect	(35)
Net income	114
Pension plan:
Income before income taxes	149
Related income tax effect	(35)
Net income	114
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
Available for sale ("AFS") securities:
Income before income taxes	1,149
Related income tax effect	(416)
Net income	733
Pension plan:
Recognized net actuarial loss	1,149
Income before income taxes	1,149
Related income tax effect	(416)
Net income	$ 733

Earnings Per Share - Reconcilia

Earnings Per Share - 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
	Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share [Abstract]
Distributed earnings allocated to common stock	$ 35,679	$ 26,722
Undistributed earnings allocated to common stock	25,919	12,014
Net earnings allocated to common shareholders	$ 61,598	$ 38,736
Average common shares outstanding	104,859,427	80,902,368
Common stock equivalents	303,431	404,172
Average diluted shares outstanding	105,162,858	81,306,540
Earnings per basic common share	$ 0.59	$ 0.48
Earnings per diluted common share	$ 0.59	$ 0.48

Variable Interest Entities - Ad

Variable Interest Entities - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2018Trust
Variable Interest Entity, Not Primary Beneficiary, Disclosures [Abstract]
Number of statutory business trusts	14
Percentage of equity shares of each trust owned by the company	100.00%

Variable Interest Entities - In

Variable Interest Entities - Information Related to Statutory Trusts (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)
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
Cardinal Statutory Trust I [Member]
Variable Interest Entity [Line Items]
Issuance Date	Jul. 27, 2004
Amount of Capital Securities Issued	$ 20,000
Interest Rate	3-month LIBOR + 2.40%
Maturity Date	Sep. 15, 2034
UFBC Capital Trust I [Member]
Variable Interest Entity [Line Items]
Issuance Date	Dec. 30, 2004
Amount of Capital Securities Issued	$ 5,000
Interest Rate	3-month LIBOR + 2.10%
Maturity Date	Mar. 15, 2035

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	Mar. 31, 2018	Dec. 31, 2017
Variable Interest Entity [Line Items]
Aggregate Assets	$ 257,527	$ 266,669
Aggregate Liabilities	248,700	257,674
Risk Of Loss	$ 8,827	$ 8,995

Segment Information - Additiona

Segment Information - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2018Segment
Segment Reporting [Abstract]
Number of reportable segments	1
Number of business segment	2

Segment Information - Summary o

Segment Information - Summary of Segment Reporting Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Net interest income	$ 144,043	$ 107,620
Provision for loans losses	5,178	5,899
Other income	31,192	20,146
Other expense	90,452	62,842
Income taxes	17,899	20,216
Net income	61,706	38,809
Total assets (liabilities)	18,619,702	14,762,315
Average assets (liabilities)	18,543,797	14,405,733
Operating Segments [Member] | Community Banking [Member]
Segment Reporting Information [Line Items]
Net interest income	146,261	109,660
Provision for loans losses	5,178	5,899
Other income	17,131	16,813
Other expense	72,491	62,752
Income taxes	19,276	19,804
Net income	66,447	38,018
Total assets (liabilities)	18,319,946	14,779,983
Average assets (liabilities)	18,318,613	14,433,409
Operating Segments [Member] | Mortgage Banking [Member]
Segment Reporting Information [Line Items]
Net interest income	376
Provision for loans losses	0
Other income	14,883
Other expense	18,384
Income taxes	(703)
Net income	(2,422)
Total assets (liabilities)	289,925
Average assets (liabilities)	210,172
Other [Member]
Segment Reporting Information [Line Items]
Net interest income	(2,594)	(2,040)
Provision for loans losses	0	0
Other income	(822)	3,333
Other expense	(423)	90
Income taxes	(674)	412
Net income	(2,319)	791
Total assets (liabilities)	9,831	(17,668)
Average assets (liabilities)	$ 15,012	$ (27,676)