United Bankshares (UBSI) 10-Q 8 Nov 18 2018 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Oct. 31, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3
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
Smaller Reporting Company	false
Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		103,183,953

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Assets
Cash and due from banks	$ 191,809	$ 196,742
Interest-bearing deposits with other banks	1,062,078	1,468,636
Federal funds sold	799	789
Total cash and cash equivalents	1,254,686	1,666,167
Securities available for sale at estimated fair value (amortized cost-$2,230,884 at September 30, 2018 and $1,900,684 at December 31, 2017)	2,178,567	1,888,756
Securities held to maturity (estimated fair value-$19,619 at September 30, 2018 and $20,018 at December 31, 2017)	20,351	20,428
Equity securities at estimated fair value	9,845	0
Other investment securities	166,749	162,461
Loans held for sale (at fair value-$231,310 at September 30, 2018 and $263,308 at December 31, 2017)	234,196	265,955
Loans	13,286,711	13,027,337
Less: Unearned income	(9,971)	(15,916)
Loans net of unearned income	13,276,740	13,011,421
Less: Allowance for loan losses	(76,941)	(76,627)
Net loans	13,199,799	12,934,794
Bank premises and equipment	99,748	104,894
Goodwill	1,478,014	1,478,380
Accrued interest receivable	60,057	52,815
Other assets	485,631	484,309
TOTAL ASSETS	19,187,643	19,058,959
Deposits:
Noninterest-bearing	4,470,815	4,294,687
Interest-bearing	9,620,357	9,535,904
Total deposits	14,091,172	13,830,591
Borrowings:
Federal funds purchased	25,790	16,235
Securities sold under agreements to repurchase	153,718	311,352
Federal Home Loan Bank borrowings	1,284,781	1,271,531
Other long-term borrowings	234,590	242,446
Reserve for lending-related commitments	1,144	679
Accrued expenses and other liabilities	145,320	145,595
TOTAL LIABILITIES	15,936,515	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-105,226,986 and 105,069,821 at September 30, 2018 and December 31, 2017, respectively, including 1,421,150 and 29,173 shares in treasury at September 30, 2018 and December 31, 2017, respectively	263,068	262,675
Surplus	2,133,157	2,129,077
Retained earnings	984,062	891,816
Accumulated other comprehensive loss	(76,660)	(42,025)
Treasury stock, at cost	(52,499)	(1,013)
TOTAL SHAREHOLDERS' EQUITY	3,251,128	3,240,530
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY	$ 19,187,643	$ 19,058,959

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Securities available for sale, amortized cost	$ 2,230,884	$ 1,900,684
Securities held to maturity	19,619	20,018
Loans held for sale at fair value	$ 231,310	$ 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	105,226,986	105,069,821
Common stock, shares in treasury	1,421,150	29,173

Consolidated Statements of Inco

Consolidated Statements of Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Interest income
Interest and fees on loans	$ 164,229	$ 155,819	$ 472,451	$ 405,660
Interest on federal funds sold and other short-term investments	5,485	4,874	13,867	11,345
Interest and dividends on securities:
Taxable	13,994	9,406	39,679	26,226
Tax-exempt	1,322	1,484	4,218	4,057
Total interest income	185,030	171,583	530,215	447,288
Interest expense
Interest on deposits	26,368	14,227	61,101	35,281
Interest on short-term borrowings	618	430	1,503	1,149
Interest on long-term borrowings	9,269	6,650	25,671	16,717
Total interest expense	36,255	21,307	88,275	53,147
Net interest income	148,775	150,276	441,940	394,141
Provision for loan losses	4,808	7,279	16,190	21,429
Net interest income after provision for loan losses	143,967	142,997	425,750	372,712
Other income
Fees from brokerage services	2,787	2,080	6,964	5,818
Income from bank-owned life insurance	1,251	1,403	3,776	3,878
Net investment securities (losses) gains	(152)	467	(692)	5,154
Other income	419	311	1,406	1,626
Total other income	31,686	38,229	98,885	98,881
Other expense
Employee compensation	41,312	44,882	125,268	124,945
Employee benefits	8,645	9,004	27,514	25,667
Net occupancy expense	9,273	9,364	27,776	30,061
Other real estate owned (OREO) expense	921	2,713	2,423	4,651
Equipment expense	3,892	3,057	10,328	7,493
Data processing expense	6,068	5,597	17,735	14,971
Bankcard processing expense	485	449	1,431	1,356
FDIC insurance expense	3,530	1,540	8,220	5,062
Other expense	19,189	20,046	56,482	57,425
Total other expense	93,315	96,652	277,177	271,631
Income before income taxes	82,338	84,574	247,458	199,962
Income taxes	17,926	27,836	55,066	67,356
Net income	$ 64,412	$ 56,738	$ 192,392	$ 132,606
Earnings per common share:
Basic	$ 0.62	$ 0.54	$ 1.84	$ 1.39
Diluted	0.62	0.54	1.83	1.39
Dividends per common share	$ 0.34	$ 0.33	$ 1.02	$ 0.99
Average outstanding shares:
Basic	103,617,590	104,760,153	104,382,094	95,040,664
Diluted	103,933,959	105,068,122	104,679,876	95,450,626
Fees from Trust Services [Member]
Other income
Revenue from contract	$ 3,350	$ 2,972	$ 9,545	$ 8,865
Fees from Deposit Services [Member]
Other income
Revenue from contract	8,673	8,744	25,323	24,978
Bankcard Fees and Merchant Discounts [Member]
Other income
Revenue from contract	1,549	1,332	4,384	3,432
Other Service Charges, Commissions, and Fees [Member]
Other income
Revenue from contract	532	535	1,640	1,533
Mortgage Banking [Member]
Other income
Revenue from contract	$ 13,277	$ 20,385	$ 46,539	$ 43,597

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 64,412	$ 56,738	$ 192,392	$ 132,606
Change in net unrealized (loss) gain on available-for-sale (AFS) securities, net of tax	(7,579)	1,964	(30,853)	8,443
Accretion of the net unrealized loss on the transfer of AFS securities to held-to-maturity (HTM) securities, net of tax	2	2	4	4
Change in pension plan assets, net of tax	918	717	2,703	2,107
Comprehensive income, net of tax	$ 57,753	$ 59,421	$ 164,246	$ 143,160

Consolidated Statement of Chang

Consolidated Statement of Changes in Shareholders' Equity (Unaudited) - 9 months ended Sep. 30, 2018 - USD ($) $ in Thousands	Total	Common Stock [Member]	Surplus [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]	Deferred Compensation Plan [Member]	Deferred Compensation Plan [Member]Common Stock [Member]	Deferred Compensation Plan [Member]Surplus [Member]	Deferred Compensation Plan [Member]Retained Earnings [Member]	Deferred Compensation Plan [Member]Accumulated Other Comprehensive Income (Loss) [Member]	Deferred Compensation Plan [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	192,392	$ 0	0	192,392	0	0
Other comprehensive income, net of tax	(28,146)	0	0	0	(28,146)	0
Total comprehensive income, net of tax	164,246
Stock based compensation expense	3,016	0	3,016	0	0	0
Purchase of treasury stock	(51,323)	0	0	0	0	(51,323)
Distribution of treasury stock from deferred compensation plan (26 shares)							$ 1	$ 0	$ 0	$ 0	$ 0	$ 1
Cash dividends	(106,635)			(106,635)	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	164	0	0	(164)
Common stock options exercised	$ 1,293	$ 150	1,143	0	0	0
Common stock options exercised, shares	60,161	60,161
Ending Balance at Sep. 30, 2018	$ 3,251,128	$ 263,068	$ 2,133,157	984,062	(76,660)	$ (52,499)
Ending Balance, shares at Sep. 30, 2018		105,226,986
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 Cha_2

Consolidated Statement of Changes in Shareholders' Equity (Unaudited) (Parenthetical)	9 Months Ended
	Sep. 30, 2018$ / sharesshares
Cash dividends per share | $ / shares	$ 1.02
Common stock options exercised, shares	60,161
Common Stock [Member]
Purchase of treasury stock, shares	0
Grant of restricted stock, shares	97,004
Forfeiture of restricted stock, shares	4,253
Common stock options exercised, shares	60,161
Treasury Stock [Member]
Purchase of treasury stock, shares	1,387,750
Deferred Compensation Plan [Member] | Common Stock [Member]
Distribution of treasury stock from deferred compensation plan, shares	0
Deferred Compensation Plan [Member] | Treasury Stock [Member]
Distribution of treasury stock from deferred compensation plan, shares	26

Condensed Consolidated Statemen

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Statement of Cash Flows [Abstract]
NET CASH PROVIDED BY OPERATING ACTIVITIES	$ 218,771	$ 125,151
INVESTING ACTIVITIES
Proceeds from maturities and calls of securities held to maturity	2	12,929
Proceeds from sales of securities available for sale	86,061	245,065
Proceeds from maturities and calls of securities available for sale	201,107	386,496
Purchases of securities available for sale	(629,760)	(630,061)
Proceeds from sales of equity securities	1,825	0
Purchases of equity securities	(598)	0
Proceeds from sales and redemptions of other investment securities	35,987	14,393
Purchases of other investment securities	(45,075)	(51,941)
Purchases of bank premises and equipment	(4,439)	(11,115)
Proceeds from sales of bank premises and equipment	2,171	13
Proceeds from the sales of OREO properties	9,105	4,908
Acquisition of subsidiaries, net of cash paid	0	44,531
Net change in loans	(248,623)	369,233
NET CASH (USED IN) PROVIDED BY INVESTING ACTIVITIES	(592,237)	384,451
FINANCING ACTIVITIES
Cash dividends paid	(107,046)	(86,709)
Acquisition of treasury stock	(51,323)	(1)
Proceeds from exercise of stock options	1,277	3,296
Repayment of long-term Federal Home Loan Bank borrowings	(635,000)	(845,207)
Proceeds from issuance of long-term Federal Home Loan Bank borrowings	650,000	815,000
Repayment of trust preferred issuance	(9,374)	0
Distribution of treasury stock for deferred compensation plan	1	1
Changes in:
Deposits	261,529	(269,742)
Federal funds purchased, securities sold under agreements to repurchase and other short-term borrowings	(148,079)	186,270
NET CASH USED IN FINANCING ACTIVITIES	(38,015)	(197,092)
(Decrease) Increase in cash and cash equivalents	(411,481)	312,510
Cash and cash equivalents at beginning of year	1,666,167	1,434,527
Cash and cash equivalents at end of period	1,254,686	1,747,037
Noncash investing activities:
Transfers of loans to OREO	$ 1,809	$ 3,829

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 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 August 2018, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2018-14 715-20): No. 2018-14 No. 2018-14 In August 2018, the FASB issued ASU No. 2018-13 No. 2018-13 No. 2018-13 In June 2018, the FASB issued Accounting Standards Update (ASU) No. 2018-07 non-employees non-employee No. 2018-07 No. 2018-07 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 No. 2017-07, No. 2017-07 No. 2017-07 No. 2017-07 In January 2017, the FASB issued ASU No. 2017-04, No. 2017-04 No. 2017-04 In January 2017, the FASB issued ASU No. 2017-01, No. 2017-01 No. 2017-01 In August 2016, the FASB issued ASU No. 2016-15, No. 2016-15 No. 2016-15 No. 2016-15 In June 2016, the FASB issued ASU No. 2016-13, No. 2016-13 available-for-sale No. 2016-13 No. 2016-13 In March 2016, the FASB issued ASU No. 2016-09, No. 2016-09 No. 2016-09 No. 2016-09 tax-related No. 2016-09 In February 2016, the FASB issued ASU No. 2016-02, No. 2016-02 No. 2016-02 right-of-use No. 2018-11 non-lease non-lease No. 2018-10 2018-10 The Company is currently assessing the impact of the adoption of ASU No. 2016-02 In January 2016, the FASB issued ASU No. 2016-01, 2016-01 No. 2016-01 available-for-sale No. 2016-01 In May 2014, the FASB issued ASU No. 2014-09, No. 2014-09 No. 2014-09 No. 2014-09 No. 2014-09 No. 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	9 Months Ended
	Sep. 30, 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 purchase price has been allocated to the identifiable tangible and intangible assets resulting in additions to goodwill, core deposit intangibles and the George Mason trade name intangible of $612,920, $28,724 and $1,080, respectively. The core deposit intangibles are being 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 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 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 September 30, 2018, the discounts on leases and trust preferred issuances had an average estimated remaining life of 5.00 years and 15.97 years, respectively, and the premiums on the interest-bearing deposits and the FHLB advances each had an average estimated remaining life of 4.00 years and 3.81 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 September 30, 2018. The estimated fair values of the acquired assets and assumed liabilities, including identifiable intangible assets and goodwill are considered final as of April 21, 2018. 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, 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 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 24,774 Core deposit intangibles 28,724 George Mason trade name intangible 1,080 Other assets 135,383 Total identifiable assets $ 4,070,235 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 Fair value of net assets acquired including identifiable intangible assets 362,334 Resulting goodwill $ 612,920 The operating results of United for the nine months ended September 30, 2018 include operating results of acquired assets and assumed liabilities. The operations of United’s metropolitan Washington D.C. geographic area, which primarily includes the acquired operations of Cardinal, provided $519,747 in total revenues, which represents net interest income plus other income, and $270,914 in net income from the period from the Cardinal Acquisition Date to September 30, 2018. These amounts are included in United’s consolidated financial statements as of and for the nine months ended September 30, 2018. Cardinal’s results of operations prior to the Cardinal Acquisition Date are not included in United’s consolidated financial statements.

Investment Securities

Investment Securities	9 Months Ended
	Sep. 30, 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. September 30, 2018 Amortized Gross Gross Estimated Cumulative U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 103,237 $ 0 $ 1,672 $ 101,565 $ 0 State and political subdivisions 258,656 440 6,850 252,246 0 Residential mortgage-backed securities Agency 973,307 541 30,201 943,647 0 Non-agency 4,086 486 0 4,572 86 Commercial mortgage-backed securities Agency 557,211 71 13,630 543,652 0 Asset-backed securities 223,350 638 386 223,602 0 Trust preferred collateralized debt obligations 6,176 253 275 6,154 2,586 Single issue trust preferred securities 8,748 127 771 8,104 0 Other corporate securities 96,113 51 1,139 95,025 0 Total $ 2,230,884 $ 2,607 $ 54,924 $ 2,178,567 $ 2,672 December 31, 2017 Amortized Gross Gross Estimated Cumulative 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 September 30, 2018 Fair Value Unrealized Fair Value Unrealized U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 89,255 $ 1,233 $ 12,311 $ 439 State and political subdivisions 127,202 2,166 80,886 4,684 Residential mortgage-backed securities Agency 612,343 15,591 300,669 14,610 Non-agency 0 0 0 0 Commercial mortgage-backed securities Agency 318,487 7,693 209,241 5,937 Asset-backed securities 92,432 386 0 0 Trust preferred collateralized debt obligations 0 0 2,225 275 Single issue trust preferred securities 0 0 4,950 771 Other corporate securities 78,095 1,139 0 0 Total $ 1,317,814 $ 28,208 $ 610,282 $ 26,716 Less than 12 months 12 months or longer December 31, 2017 Fair Value Unrealized Fair Value Unrealized 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 September 30 Nine Months Ended September 30 2018 2017 2018 2017 Proceeds from sales and calls $ 109,093 $ 64,257 $ 283,953 $ 631,561 Gross realized gains 93 1,781 1,314 2,840 Gross realized losses 207 1,314 1,604 1,396 At September 30, 2018, gross unrealized losses on available for sale securities were $54,924 on 733 securities of a total portfolio of 865 available for sale securities. Securities in an unrealized loss position at September 30, 2018 consisted primarily of state and political subdivision securities, and agency commercial and residential mortgage-backed securities. 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 $258,656 million at September 30, 2018. As of September 30, 2018, approximately 76% 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 September 30, 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 September 30, 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 $1,530,518 at September 30, 2018. Of the $1,530,518 amount, $557,211 was related to agency commercial mortgage-backed securities and $973,307 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 September 30, 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 third 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 September 30, 2018 consisted of $3,028 in investment grade bonds and $5,720 in unrated bonds. The investment grade bonds were rated BBB-. Trust preferred collateralized debt obligations (Trup Cdos) The total amortized cost balance of United’s Trup Cdo portfolio was $6,176 as of September 30, 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 September 30, 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 September 30, 2018 is other-than-temporarily impaired. Corporate securities As of September 30, 2018, United’s Corporate securities portfolio had a total amortized cost balance of $96,113. The majority of the portfolio consisted of debt issuances of corporations representing a variety of industries, including financial institutions. Of the $96,113, 78% was investment grade rated and 22% 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 September 30, 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 September 30 Nine Months Ended September 30 2018 2017 2018 2017 Balance of cumulative credit losses at beginning of period $ 3,199 $ 22,162 $ 18,060 $ 22,162 Reductions for securities sold or paid off during the period 0 (4,102 ) (14,861 ) (4,102 ) Balance of cumulative credit losses at end of period $ 3,199 $ 18,060 $ 3,199 $ 18,060 The amortized cost and estimated fair value of securities available for sale at September 30, 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. September 30, 2018 December 31, 2017 Amortized Estimated Amortized Estimated Due in one year or less $ 76,698 $ 76,346 $ 50,311 $ 50,212 Due after one year through five years 500,052 490,797 386,039 384,585 Due after five years through ten years 466,155 451,981 400,129 398,208 Due after ten years 1,187,979 1,159,443 1,054,493 1,045,873 Marketable equity securities 0 0 9,712 9,878 Total $ 2,230,884 $ 2,178,567 $ 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: September 30, 2018 Amortized Gross Gross Estimated U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 5,103 $ 132 $ 0 $ 5,235 State and political subdivisions 5,798 8 1 5,805 Residential mortgage-backed securities Agency 21 2 0 23 Single issue trust preferred securities 9,409 0 873 8,536 Other corporate securities 20 0 0 20 Total $ 20,351 $ 142 $ 874 $ 19,619 December 31, 2017 Amortized Gross Gross Estimated 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 third quarter and first nine months of 2018 and 2017. The amortized cost and estimated fair value of debt securities held to maturity at September 30, 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. September 30, 2018 December 31, 2017 Amortized Estimated Amortized Estimated Due in one year or less $ 7,103 $ 7,235 $ 0 $ 0 Due after one year through five years 2,158 2,163 9,344 9,660 Due after five years through ten years 8,093 7,610 5,663 5,343 Due after ten years 2,997 2,611 5,421 5,015 Total $ 20,351 $ 19,619 $ 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 $9,845 at September 30, 2018. Prior to the adoption of ASU No. 2016-01 Three Months September 30, Nine Months September 30, Net losses recognized during the period $ (38 ) $ (102 ) Net losses recognized during the period on equity securities sold (2 ) (4 ) Unrealized gains recognized during the period on equity securities still held at period end 0 50 Unrealized losses recognized during the period on equity securities still held at period end 36 148 Other investment securities During the third quarter of 2018, United evaluated all of its cost method investments to determine if certain events or changes in circumstances during the third quarter of 2018 had a significant adverse effect on the fair value of any of its cost method securities. United determined that there was no individual security that experienced an adverse event during the third quarter. There were no other events or changes in circumstances during the third 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 $1,999,152 and $1,403,565 at September 30, 2018 and December 31, 2017, respectively.

Loans

Loans	9 Months Ended
	Sep. 30, 2018
Receivables [Abstract]
Loans	4. LOANS Major classes of loans are as follows: September 30, 2018 December 31, Commercial, financial and agricultural: Owner-occupied commercial real estate $ 1,336,434 $ 1,361,629 Nonowner-occupied commercial real estate 4,341,501 4,451,298 Other commercial loans 1,932,919 1,998,979 Total commercial, financial & agricultural 7,610,854 7,811,906 Residential real estate 3,387,268 2,996,171 Construction & land development 1,379,985 1,504,907 Consumer: Bankcard 9,530 10,314 Other consumer 899,074 704,039 Total gross loans $ 13,286,711 $ 13,027,337 The table above does not include loans held for sale of $234,196 and $265,955 at September 30, 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 $155,526 or 1.17% of total gross loans at September 30, 2018 and $210,521 or 1.62% of total gross loans at December 31, 2017. The contractual principal in these acquired impaired loans was $205,034 and $285,964 at September 30, 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 nine months of 2018 follows: Accretable yield at the beginning of the period $ 39,098 Accretion (including cash recoveries) (8,371 ) Additions 691 Net reclassifications to accretable from non-accretable 9,112 Disposals (including maturities, foreclosures, and charge-offs) (3,323 ) Accretable yield at the end of the period $ 37,207 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 $25,826 and $36,360 at September 30, 2018 and December 31, 2017, respectively.

Credit Quality

Credit Quality	9 Months Ended
	Sep. 30, 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 September 30, 2018, United had TDRs of $63,626 as compared to $50,129 as of December 31, 2017. Of the $63,626 aggregate balance of TDRs at September 30, 2018, $50,974 was on nonaccrual, $85 were 90 days or more past due and $1,778 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 September 30, 2018, there were no commitments to lend additional funds to debtors owing receivables whose terms have been modified in TDRs. At September 30, 2018, United had restructured loans in the amount of $1,646 that were modified by a reduction in the interest rate, $1,849 that were modified by a combination of a reduction in the interest rate and the principal and $60,131 that were modified by a change in terms. A loan acquired and accounted for under ASC Topic 310-30 The following table sets forth United’s troubled debt restructurings that have been restructured during the three months ended September 30, 2018, segregated by class of loans. No loans were restructured during the three months ended September 30, 2017. Troubled Debt Restructurings For the Three Months Ended September 30, 2018 Number Pre-Modification Post- Commercial real estate: Owner-occupied 0 $ 0 $ 0 Nonowner-occupied 0 0 0 Other commercial 5 7,420 7,364 Residential real estate 1 272 272 Construction & land development 0 0 0 Consumer: Bankcard 0 0 0 Other consumer 0 0 0 Total 6 $ 7,692 $ 7,636 The following table sets forth United’s troubled debt restructurings that have been restructured during the nine months ended September 30, 2018 and 2017, segregated by class of loans: Troubled Debt Restructurings For the Nine Months Ended September 30, 2018 September 30, 2017 Number Pre-Modification Post- Number Pre-Modification Post- Commercial real estate: Owner-occupied 0 $ 0 $ 0 1 $ 5,333 $ 5,333 Nonowner-occupied 0 0 0 0 0 0 Other commercial 9 16,992 16,890 8 24,102 22,291 Residential real estate 3 7,225 7,225 0 0 0 Construction & land development 0 0 0 1 1,456 1,400 Consumer: Bankcard 0 0 0 0 0 0 Other consumer 0 0 0 0 0 0 Total 12 $ 24,217 $ 24,115 10 $ 30,891 $ 29,024 During the third quarter and first nine months of 2018, $7,636 and $24,115 of restructured loans were modified by a change in loan terms. During the first nine months of 2017, $29,024 of restructured loans were modified by a change in loan terms. In some instances, the post-modification balance on the restructured loans is larger than the pre-modification The following table presents troubled debt restructurings, by class of loan, that had charge-offs during the three months and nine months ended September 30, 2018. Three Months Ended September 30, 2018 Nine Months Ended September 30, 2018 (In thousands) Number Recorded Number Recorded Troubled Debt Restructurings Commercial real estate: Owner-occupied 0 $ 0 0 $ 0 Nonowner-occupied 0 0 0 0 Other commercial 1 622 1 622 Residential real estate 0 0 0 0 Construction & land development 0 0 0 0 Consumer: Bankcard 0 0 0 0 Other consumer 0 0 0 0 Total 1 $ 622 1 $ 622 No loans restructured during the twelve-month period ended September 30, 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 September 30, 2018 30-89 90 Days or Total Past Current & Total Financing Recorded Commercial real estate: Owner-occupied $ 11,089 $ 18,009 $ 29,098 $ 1,307,336 $ 1,336,434 $ 1,431 Nonowner-occupied 17,182 17,557 34,739 4,306,762 4,341,501 2,015 Other commercial 7,413 49,467 56,880 1,876,039 1,932,919 1,326 Residential real estate 35,646 30,519 66,165 3,321,103 3,387,268 9,941 Construction & land development 3,406 17,069 20,475 1,359,510 1,379,985 642 Consumer: Bankcard 649 177 826 8,704 9,530 177 Other consumer 7,874 763 8,637 890,437 899,074 502 Total $ 83,259 $ 133,561 $ 216,820 $ 13,069,891 $ 13,286,711 $ 16,034 (1) Other includes loans with a recorded investment of $155,526 acquired and accounted for under ASC Topic 310-30 Age Analysis of Past Due Loans As of December 31, 2017 (In thousands) 30-89 90 Days or Total Past Current & Total Financing Recorded 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 September 30, 2018 December 31, 2017 Commercial real estate: Owner-occupied $ 16,578 $ 13,205 Nonowner-occupied 15,542 19,814 Other commercial 48,141 67,536 Residential real estate 20,578 22,118 Construction & land development 16,427 16,805 Consumer: Bankcard 0 0 Other consumer 261 193 Total $ 117,527 $ 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 September 30, 2018 Commercial Real Estate Owner- Nonowner- Other Construction & Grade: Pass $ 1,266,769 $ 4,197,966 $ 1,827,465 $ 1,302,968 Special mention 15,221 60,293 13,528 4,715 Substandard 54,444 83,242 90,023 72,302 Doubtful 0 0 1,903 0 Total $ 1,336,434 $ 4,341,501 $ 1,932,919 $ 1,379,985 As of December 31, 2017 Commercial Real Estate Owner- Nonowner- Other Construction & 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 September 30, 2018 Residential Bankcard Other Grade: Pass $ 3,322,863 $ 8,704 $ 890,411 Special mention 17,309 649 7,879 Substandard 47,096 177 784 Doubtful 0 0 0 Total $ 3,387,268 $ 9,530 $ 899,074 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 September 30, 2018 December 31, 2017 Recorded Unpaid Related Recorded Unpaid Related With no related allowance recorded: Commercial real estate: Owner-occupied $ 58,367 $ 58,532 $ 0 $ 78,117 $ 78,419 $ 0 Nonowner-occupied 98,912 98,971 0 134,136 134,195 0 Other commercial 60,602 63,069 0 46,993 49,552 0 Residential real estate 33,190 34,041 0 26,751 28,202 0 Construction & land development 36,576 40,673 0 52,279 59,691 0 Consumer: Bankcard 0 0 0 0 0 0 Other consumer 23 23 0 15 15 0 With an allowance recorded: Commercial real estate: Owner-occupied $ 9,990 $ 9,990 $ 2,560 $ 9,132 $ 9,132 $ 2,251 Nonowner-occupied 14,468 14,468 2,683 7,797 7,797 1,592 Other commercial 50,454 59,052 16,500 60,512 70,396 16,721 Residential real estate 17,853 19,295 3,115 9,813 10,418 1,552 Construction & land development 16,816 19,470 2,494 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 $ 68,357 $ 68,522 $ 2,560 $ 87,249 $ 87,551 $ 2,251 Nonowner-occupied 113,380 113,439 2,683 141,933 141,992 1,592 Other commercial 111,056 122,121 16,500 107,505 119,948 16,721 Residential real estate 51,043 53,336 3,115 36,564 38,620 1,552 Construction & land development 53,392 60,143 2,494 53,662 61,074 229 Consumer: Bankcard 0 0 0 0 0 0 Other consumer 23 23 0 15 15 0 Impaired Loans For the Three Months Ended September 30, 2018 September 30, 2017 Average Interest Average Interest With no related allowance recorded: Commercial real estate: Owner-occupied $ 65,625 $ 365 $ 74,111 $ 374 Nonowner-occupied 99,005 311 148,753 178 Other commercial 56,489 313 57,302 148 Residential real estate 28,753 144 21,772 58 Construction & land development 41,036 278 42,240 348 Consumer: Bankcard 0 0 0 0 Other consumer 23 0 25 0 With an allowance recorded: Commercial real estate: Owner-occupied $ 7,378 $ 6 $ 11,442 $ 78 Nonowner-occupied 12,465 189 13,111 10 Other commercial 47,563 305 71,886 42 Residential real estate 14,975 57 15,276 16 Construction & land development 9,408 20 1,602 21 Consumer: Bankcard 0 0 0 0 Other consumer 0 0 0 0 Total: Commercial real estate: Owner-occupied $ 73,003 $ 371 $ 85,553 $ 452 Nonowner-occupied 111,470 500 161,864 188 Other commercial 104,052 618 129,188 190 Residential real estate 43,728 201 37,048 74 Construction & land development 50,444 298 43,842 369 Consumer: Bankcard 0 0 0 0 Other consumer 23 0 25 0 Impaired Loans For the Nine Months Ended September 30, 2018 September 30, 2017 Average Interest Average Interest With no related allowance recorded: Commercial real estate: Owner-occupied $ 69,009 $ 1,101 $ 70,477 $ 1,227 Nonowner-occupied 105,199 928 121,811 551 Other commercial 55,124 1,020 57,047 632 Residential real estate 27,210 501 21,397 219 Construction & land development 43,464 707 40,344 1,046 Consumer: Bankcard 0 0 0 0 Other consumer 29 0 29 0 With an allowance recorded: Commercial real estate: Owner-occupied $ 6,876 $ 18 $ 12,141 $ 393 Nonowner-occupied 11,158 251 13,492 108 Other commercial 47,736 380 71,736 685 Residential real estate 13,946 247 14,904 58 Construction & land development 6,944 60 2,195 63 Consumer: Bankcard 0 0 0 0 Other consumer 0 0 0 0 Total: Commercial real estate: Owner-occupied $ 75,885 $ 1,119 $ 82,618 $ 1,620 Nonowner-occupied 116,357 1,179 135,303 659 Other commercial 102,860 1,400 128,783 1,317 Residential real estate 41,156 748 36,301 277 Construction & land development 50,408 767 42,539 1,109 Consumer: Bankcard 0 0 0 0 Other consumer 29 0 29 0 At September 30, 2018 and December 31, 2017, other real estate owned (“OREO”) included in other assets in the Consolidated Balance Sheets was $18,786 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 September 30, 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 $569 and $873, respectively.

Allowance for Credit Losses

Allowance for Credit Losses	9 Months Ended
	Sep. 30, 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 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 and nine months ended September 30, 2018, 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 $1,144 and $679 at September 30, 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 For the Three Months Ended September 30, 2018 Commercial Real Other Residential Construction & Consumer Allowance for Total Owner- Nonowner- Allowance for Loan Losses: Beginning balance $ 3,213 $ 6,183 $ 48,191 $ 10,380 $ 6,592 $ 2,419 $ 157 $ 77,135 Charge-offs 1,478 0 4,432 365 110 659 0 7,044 Recoveries 415 395 394 558 134 146 0 2,042 Provision 2,391 22 291 1,067 480 575 (18 ) 4,808 Ending balance $ 4,541 $ 6,600 $ 44,444 $ 11,640 $ 7,096 $ 2,481 $ 139 $ 76,941 Allowance for Loan Losses and Carrying Amount of Loans For the Nine Months Ended September 30, 2018 Commercial Real Estate Other Residential Construction & Consumer Allowance for Total Owner- Nonowner- Allowance for Loan Losses: Beginning balance $ 5,401 $ 6,369 $ 45,189 $ 9,927 $ 7,187 $ 2,481 $ 73 $ 76,627 Charge-offs 3,221 314 13,095 1,357 642 1,985 0 20,614 Recoveries 1,160 548 1,484 916 145 485 0 4,738 Provision 1,201 (3 ) 10,866 2,154 406 1,500 66 16,190 Ending balance $ 4,541 $ 6,600 $ 44,444 $ 11,640 $ 7,096 $ 2,481 $ 139 $ 76,941 Ending Balance: individually evaluated for impairment $ 2,560 $ 2,683 $ 16,500 $ 3,116 $ 2,494 $ 0 $ 0 $ 27,353 Ending Balance: collectively evaluated for impairment $ 1,981 $ 3,917 $ 27,944 $ 8,524 $ 4,602 $ 2,481 $ 139 $ 49,588 Ending Balance: loans acquired with deteriorated credit quality $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 Financing receivables: Ending balance $ 1,336,434 $ 4,341,501 $ 1,932,919 $ 3,387,268 $ 1,379,985 $ 908,604 $ 0 $ 13,286,711 Ending Balance: individually evaluated for impairment $ 29,391 $ 22,768 $ 73,544 $ 19,994 $ 16,875 $ 0 $ 0 $ 162,572 Ending Balance: collectively evaluated for impairment $ 1,284,114 $ 4,250,305 $ 1,830,646 $ 3,351,837 $ 1,343,130 $ 908,581 $ 0 $ 12,968,613 Ending Balance: loans acquired with deteriorated credit quality $ 22,929 $ 68,428 $ 28,729 $ 15,437 $ 19,980 $ 23 $ 0 $ 155,526 Allowance for Loan Losses and Carrying Amount of Loans For the Year Ended December 31, 2017 Commercial Real Estate Other Residential Construction & Consumer Allowance for Total Owner- Nonowner- 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	9 Months Ended
	Sep. 30, 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: September 30, 2018 Community Banking Mortgage Banking Total Gross Accumulated Gross Accumulated Gross Accumulated Amortized intangible assets: Core deposit intangible assets $ 98,359 ($ 60,482 ) $ 0 ($ 0 ) $ 98,359 ($ 60,482 ) Non-amortized George Mason trade name $ 0 $ 1,080 $ 1,080 Goodwill not subject to amortization $ 1,472,699 $ 5,315 $ 1,478,014 December 31, 2017 Community Banking Mortgage Banking Total Gross Accumulated Gross Accumulated Gross Accumulated 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 Mortgage Total Goodwill at December 31, 2017 $ 1,473,265 $ 5,115 $ 1,478,380 Addition to goodwill from Cardinal acquisition (566 ) 200 (366 ) Goodwill at September 30, 2018 $ 1,472,699 $ 5,315 $ 1,478,014 United incurred amortization expense on intangible assets of $2,009 and $6,029 for the quarter and nine months ended September 30, 2018, respectively, and $2,240 and $5,381 for the quarter and nine months ended September 30, 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	9 Months Ended
	Sep. 30, 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 September 30, 2018, federal funds purchased were $25,790 while total securities sold under agreements to repurchase (REPOs) were $153,718. 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	9 Months Ended
	Sep. 30, 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 September 30, 2018, United had an unused borrowing amount of approximately $3,986,778 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 September 30, 2018, $1,284,781 of FHLB advances with a weighted-average interest rate of 2.13% are scheduled to mature within the next seven years. The scheduled maturities of these FHLB borrowings are as follows: Year Amount 2018 $ 970,890 2019 187,224 2020 41,779 2021 52,667 2022 and thereafter 32,221 Total $ 1,284,781 At September 30, 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 September 30, 2018 and December 31, 2017, the outstanding balance of the Debentures was $234,590 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	9 Months Ended
	Sep. 30, 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 $3,861,482 and $4,224,719 of loan commitments outstanding as of September 30, 2018 and December 31, 2017, respectively, the majority of which contractually expire within one year. Included in the September 30, 2018 amount are commitments to extend credit of $433,931 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 September 30, 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 $132,735 and $147,017 as of September 30, 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 September 30, 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	9 Months Ended
	Sep. 30, 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 September 30, 2018 and December 31, 2017. Asset Derivatives September 30, 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 $ 86,655 $ 4,042 Other assets $ 71,831 $ 538 Total derivatives designated as hedging instruments $ 86,655 $ 4,042 $ 71,831 $ 538 Derivatives not designated as hedging instruments Forward loan sales commitments Other assets $ 0 $ 0 Other assets $ 31,024 $ 2 TBA mortgage-backed securities Other assets 223,500 1,161 0 0 Interest rate lock commitments Other assets 135,069 3,991 Other assets 148,866 4,559 Total derivatives not designated as hedging instruments $ 358,569 $ 5,152 $ 179,890 $ 4,561 Total asset derivatives $ 445,224 $ 9,194 $ 251,721 $ 5,099 Liability Derivatives September 30, 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 Forward loan sales commitments Other liabilities $ 22,521 $ 197 Other liabilities $ 0 $ 0 TBA mortgage-backed securities Other liabilities $ 0 $ 0 Other liabilities 236,500 312 Interest rate lock commitments Other liabilities 0 0 Other liabilities 0 0 Total derivatives not designated as hedging instruments $ 22,521 $ 197 $ 236,500 $ 312 Total liability derivatives $ 22,521 $ 197 $ 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 and nine months ended September 30, 2018 and 2017 are presented as follows: Three Months Ended Income Statement Location September 30, September 30, Derivatives in hedging relationships Fair Value Hedges: Interest rate swap contracts Interest income/(expense) $ (24 ) $ (208 ) Total derivatives in hedging relationships $ (24 ) $ (208 ) Derivatives not designated as hedging instruments Forward loan sales commitments Income from Mortgage (197 ) (257 ) TBA mortgage-backed securities Income from Mortgage 2,583 123 Interest rate lock commitments Income from Mortgage (3,262 ) (4,484 ) Total derivatives not designated as hedging instruments $ (876 ) $ (4,618 ) Total derivatives $ (900 ) $ (4,826 ) Nine Months Ended Income Statement Location September 30, September 30, Derivatives in fair value hedging relationships Fair Value Hedges: Interest rate swap contracts Interest income/(expense) $ (42 ) $ (648 ) Cash Flow Hedges: Forward loan sales commitments Other income 0 0 Total derivatives in hedging relationships $ (42 ) $ (648 ) Derivatives not designated as hedging instruments Forward loan sales commitments Income from Mortgage (12 ) (427 ) TBA mortgage-backed securities Income from Mortgage 1,473 2,907 Interest rate lock commitments Income from Mortgage (1,643 ) (3,465 ) Total derivatives not designated as hedging instruments $ (182 ) $ (985 ) Total derivatives $ (224 ) $ (1,633 )

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 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 September 30, 2018 and December 31, 2017, segregated by the level of the valuation inputs within the fair value hierarchy. Fair Value at September 30, 2018 Using Description Balance as of September 30, 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 $ 101,565 $ 0 $ 101,565 $ 0 State and political subdivisions 252,246 0 252,246 0 Residential mortgage-backed securities Agency 943,647 0 943,647 0 Non-agency 4,572 0 4,572 0 Commercial mortgage-backed securities Agency 543,652 0 543,652 0 Asset-backed securities 223,602 0 223,602 0 Trust preferred collateralized debt obligations 6,154 0 0 6,154 Single issue trust preferred securities 8,104 0 8,104 0 Other corporate securities 95,025 6,879 88,146 0 Total available for sale securities 2,178,567 6,879 2,165,534 6,154 Equity securities: Financial services industry 173 173 0 0 Equity mutual funds (1) 5,073 5,073 0 0 Other equity securities 4,599 4,599 0 0 Total equity securities 9,845 9,845 0 0 Loans held for sale 231,310 0 0 231,310 Derivative financial assets: Interest rate swap contracts 4,042 0 4,042 0 Forward sales commitments 0 0 0 0 Interest rate lock commitments 3,991 0 0 3,991 TBA mortgage-backed securities 1,161 0 1,161 0 Total derivative financial assets 9,194 0 5,203 3,991 Liabilities Derivative financial liabilities: Forward sales commitments 197 0 197 0 Total derivative financial liabilities 197 0 197 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 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 nine months ended September 30, 2018 and the year ended December 31, 2017. The following table presents additional information about financial assets and liabilities measured at fair value at September 30, 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 September 30, 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 1,157 8,757 Purchases, issuances, and settlements 0 0 Sales (29,300 ) (8,049 ) Transfers in and/or out of Level 3 0 0 Balance, end of period $ 6,154 $ 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 September 30, 2018 December 31, Balance, beginning of period $ 263,308 $ 0 Acquired in Cardinal merger 0 271,301 Originations 2,089,366 2,333,927 Sales (2,148,777 ) (2,408,945 ) Total gains or losses during the period recognized in earnings 54,829 58,132 Transfers in and/or out of Level 3 (27,416 ) 8,893 Balance, end of period $ 231,310 $ 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 September 30, 2018 December 31, Balance, beginning of period $ 4,559 $ 0 Acquired in Cardinal merger 0 10,393 Transfers other (568 ) (5,834 ) Balance, end of period $ 3,991 $ 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 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 September 30, Three Months September 30, Assets Loans held for sale Income from mortgage banking activities $ (5,929 ) $ (5,090 ) Description Nine Months September 30, Nine Months September 30, Assets Loans held for sale Income from mortgage banking activities $ (2,838 ) $ (7,529 ) 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: September 30, 2018 December 31, 2017 Description Unpaid Fair Fair Value Unpaid Fair Fair Value Assets Loans held for sale $ 227,943 $ 231,310 $ 3,367 $ 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: Description Balance as of September 30, Carrying value at September 30, 2018 YTD Losses Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets Loans held for sale $ 2,886 $ 0 $ 2,886 $ 0 $ 0 Impaired Loans 109,582 0 98,171 11,411 4,177 OREO 18,786 0 18,786 0 796 Description Balance as of December 31, Carrying value at December 31, 2017 YTD Losses Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) 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) September 30, 2018 Cash and cash equivalents $ 1,254,686 $ 1,254,686 $ 0 $ 1,254,686 $ 0 Securities available for sale 2,178,567 2,178,567 6,879 2,165,534 6,154 Securities held to maturity 20,351 19,619 0 16,599 3,020 Equity securities 9,845 9,845 9,845 0 0 Other securities 166,749 166,749 0 0 166,749 Loans held for sale 234,196 234,196 0 2,886 231,310 Loans 13,199,799 12,488,175 0 0 12,488,175 Derivative financial assets 9,194 9,194 0 5,203 3,991 Deposits 14,091,172 14,052,668 0 14,052,668 0 Short-term borrowings 379,508 379,508 0 379,508 0 Long-term borrowings 1,319,371 1,293,611 0 1,293,611 0 Derivative financial liabilities 197 197 0 197 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	9 Months Ended
	Sep. 30, 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 $1,024 and $3,016 related to the nonvested awards under United’s Long-Term Incentive Plans was incurred for the third quarter and first nine months of 2018, respectively, as compared to the compensation expense of $909 and $2,589 related to the nonvested awards under United’s Long-Term Incentive Plans incurred for the third quarter and first nine months of 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 September 30, 2018, and the changes during the first nine months of 2018 are presented below: Nine Months Ended September 30, 2018 Shares Aggregate Intrinsic Value Weighted Average Remaining Contractual Term (Yrs.) Exercise Price Outstanding at January 1, 2018 1,558,438 $ 31.09 Granted 276,192 37.60 Exercised (60,161 ) 23.03 Forfeited or expired (24,007 ) 32.66 Outstanding at September 30, 2018 1,750,462 $ 9,624,912 5.8 $ 32.36 Exercisable at September 30, 2018 1,169,402 $ 9,508,502 4.4 $ 28.78 The following table summarizes the status of United’s nonvested stock option awards during the first nine months of 2018: Shares Weighted-Average Nonvested at January 1, 2018 507,871 $ 7.89 Granted 276,192 7.56 Vested (187,815 ) 7.53 Forfeited or expired (15,188 ) 7.67 Nonvested at September 30, 2018 581,060 $ 7.86 During the nine months ended September 30, 2018 and 2017, 60,161 and 163,562 shares, respectively, were issued in connection with stock option exercises. All shares issued in connection with stock option exercises for the nine months ended September 30, 2018 and 2017 were issued from authorized and unissued stock. The total intrinsic value of options exercised under the Plans during the nine months ended September 30, 2018 and 2017 was $851 and $3,078 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 September 30, 2018: Number Weighted-Average Outstanding at January 1, 2018 170,496 $ 40.05 Granted 97,004 37.60 Vested (62,411 ) 37.59 Forfeited (4,253 ) 38.42 Outstanding at September 30, 2018 200,836 $ 39.67

Employee Benefit Plans

Employee Benefit Plans	9 Months Ended
	Sep. 30, 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 and nine months ended September 30, 2018 and 2017 included the following components: Three Months Ended September 30 Nine Months Ended September 30 2018 2017 2018 2017 Service cost $ 673 $ 574 $ 1,997 $ 1,705 Interest cost 1,324 1,293 3,927 3,837 Expected return on plan assets (2,578 ) (2,072 ) (7,651 ) (6,148 ) Recognized net actuarial loss 1,174 1,111 3,485 3,298 Net periodic pension (benefit) cost $ 593 $ 906 $ 1,758 $ 2,692 Weighted-Average Assumptions: Discount rate 3.83 % 4.49 % 3.83 % 4.49 % Expected return on assets 7.00 % 7.00 % 7.00 % 7.00 % Rate of compensation increase (prior to age 45) 3.50 % 3.50 % 3.50 % 3.50 % Rate of compensation increase 3.00 % 3.00 % 3.00 % 3.00 %

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 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 September 30, 2018 and 2017, the total amount of accrued interest related to uncertain tax positions was $649 and $548, 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, 2015, 2016 and 2017 and certain State Taxing authorities for the years ended December 31, 2015 through 2017. 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 118 (“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 September 30, 2018. United’s effective tax rate was 21.77% and 22.25% for the third quarter and first nine months of 2018 and 32.91% and 33.68% for the third quarter and first nine months of 2017. The lower effective tax rate for the third quarter and first nine months of 2018 was due mainly to the Tax Act.

Comprehensive Income

Comprehensive Income	9 Months Ended
	Sep. 30, 2018
Equity [Abstract]
Comprehensive Income	16. COMPREHENSIVE INCOME The components of total comprehensive income for the three and nine months ended September 30, 2018 and 2017 are as follows: Three Months Ended Nine Months Ended September 30 September 30 2018 2017 2018 2017 Net Income $ 64,412 $ 56,738 $ 192,392 $ 132,606 Available for sale (“AFS”) securities: AFS securities with OTTI charges during the period 0 0 0 (60 ) Related income tax effect 0 0 0 22 Less: OTTI charges recognized in net income 0 0 0 60 Related income tax benefit 0 0 0 (22 ) Reclassification of previous noncredit OTTI to credit OTTI 0 0 0 0 Related income tax benefit 0 0 0 0 Net unrealized (losses) gains on AFS securities with OTTI 0 0 0 0 AFS securities – all other: Change in net unrealized gain on AFS securities arising during the period (9,995 ) 3,584 (42,696 ) 14,846 Related income tax effect 2,329 (1,326 ) 11,621 (5,493 ) Net reclassification adjustment for (gains) losses included in net income 114 (467 ) 290 (1,444 ) Related income tax expense (benefit) (27 ) 173 (68 ) 534 (7,579 ) 1,964 (30,853 ) 8,443 Net effect of AFS securities on other comprehensive income (7,579 ) 1,964 (30,853 ) 8,443 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 6 6 Related income tax expense (0 ) (0 ) (2 ) (2 ) Net effect of HTM securities on other comprehensive income 2 2 4 4 Pension plan: Recognized net actuarial loss 1,174 1,111 3,485 3,298 Related income tax benefit (256 ) (394 ) (782 ) (1,191 ) Net effect of change in pension plan asset on other comprehensive income 918 717 2,703 2,107 Total change in other comprehensive income (6,659 ) 2,683 (28,146 ) 10,554 Total Comprehensive Income $ 57,753 $ 59,421 $ 164,246 $ 143,160 The components of accumulated other comprehensive income for the nine months ended September 30, 2018 are as follows: Changes in Accumulated Other Comprehensive Income (AOCI) by Component (a) For the Nine Months Ended September 30, 2018 Unrealized Accretion 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 ) 0 0 (136 ) Reclass due to adopting Accounting Standard Update 2018-02 (1,632 ) 0 (4,721 ) (6,353 ) Other comprehensive income before reclassification (31,075 ) 4 0 (31,071 ) Amounts reclassified from accumulated other comprehensive income 222 0 2,703 2,925 Net current-period other comprehensive income, net of tax (30,853 ) 4 2,703 (28,146 ) Balance at September 30, 2018 ($ 38,825 ) ($ 42 ) ($ 37,793 ) ($ 76,660 ) (a) All amounts are net-of-tax. Reclassifications out of Accumulated Other Comprehensive Income (AOCI) For the Nine Months Ended September 30, 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 to credit OTTI $ 0 Net investment securities (losses) gains Net reclassification adjustment for losses (gains) included in net income 290 Net investment securities (losses) gains 290 Total before tax Related income tax effect (68 ) Tax expense 222 Net of tax Pension plan: Recognized net actuarial loss 3,485 (a) 3,485 Total before tax Related income tax effect (782 ) Tax expense 2,703 Net of tax Total reclassifications for the period $ 2,925 (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	9 Months Ended
	Sep. 30, 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 Nine Months Ended September 30 September 30 2018 2017 2018 2017 Distributed earnings allocated to common stock $ 35,234 $ 34,587 $ 106,429 $ 95,871 Undistributed earnings allocated to common stock 29,060 22,065 85,617 36,518 Net earnings allocated to common shareholders $ 64,294 $ 56,652 $ 192,046 $ 132,389 Average common shares outstanding 103,617,590 104,760,153 104,382,094 95,040,664 Equivalents from stock options 316,369 307,969 297,782 409,962 Average diluted shares outstanding 103,933,959 105,068,122 104,679,876 95,450,626 Earnings per basic common share $ 0.62 $ 0.54 $ 1.84 $ 1.39 Earnings per diluted common share $ 0.62 $ 0.54 $ 1.83 $ 1.39

Variable Interest Entities

Variable Interest Entities	9 Months Ended
	Sep. 30, 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 LIBOR + 2.85% 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 September 30, 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 $ 257,873 $ 248,921 $ 8,952 $ 266,669 $ 257,674 $ 8,995

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 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 a LIBOR rate. In addition, the mortgage banking segment (George Mason) originates mortgage loans which are sold to the community banking segment for its loan portfolio. These intersegment 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 and nine months ended September 30, 2018 and 2017 is as follows: At and For the Three Months Ended September 30, 2018 Community Mortgage Other Intersegment Eliminations Consolidated Net interest income $ 149,770 $ 388 $ (3,168 ) $ 1,785 $ 148,775 Provision for loans losses 4,808 0 0 0 4,808 Other income 18,717 16,478 58 (3,567 ) 31,686 Other expense 75,255 17,957 1,885 (1,782 ) 93,315 Income taxes 19,296 (246 ) (1,124 ) 0 17,926 Net income (loss) $ 69,128 $ (845 ) $ (3,871 ) $ 0 $ 64,412 Total assets (liabilities) $ 19,080,734 $ 288,638 $ 12,545 $ (194,274 ) $ 19,187,643 Average assets (liabilities) 18,982,530 303,556 5,468 (243,867 ) 19,047,689 At and For the Three Months Ended September 30, 2017 Community Mortgage Other Intersegment Eliminations Consolidated Net interest income $ 152,886 $ (36 ) $ (2,574 ) $ 0 $ 150,276 Provision for loans losses 7,279 0 0 0 7,279 Other income 18,373 19,936 (80 ) 0 38,229 Other expense 74,553 24,036 (1,937 ) 0 96,652 Income taxes 29,490 (1,332 ) (322 ) 0 27,836 Net income (loss) $ 59,937 $ (2,804 ) $ (395 ) $ 0 $ 56,738 Total assets (liabilities) $ 19,083,318 $ 350,483 $ (900 ) $ (302,923 ) $ 19,129,978 Average assets (liabilities) 18,889,710 321,744 (13,994 ) (269,675 ) 18,927,785 At and For the Nine Months Ended September 30, 2018 Community Mortgage Other Intersegment Eliminations Consolidated Net interest income $ 444,840 $ 1,028 $ (8,794 ) $ 4,866 $ 441,940 Provision for loans losses 16,190 0 0 0 16,190 Other income 53,952 54,829 (696 ) (9,200 ) 98,885 Other expense 224,240 57,566 (295 ) (4,334 ) 277,177 Income taxes 57,519 (385 ) (2,068 ) 0 55,066 Net income (loss) $ 200,843 $ (1,324 ) $ (7,127 ) $ 0 $ 192,392 Total assets (liabilities) $ 19,080,734 $ 288,638 $ 12,545 $ (194,274 ) $ 19,187,643 Average assets (liabilities) 18,718,295 284,100 8,043 (240,505 ) 18,769,934 At and For the Nine Months Ended September 30, 2017 Community Mortgage Other Intersegment Eliminations Consolidated Net interest income $ 401,044 $ 54 $ (6,957 ) $ 0 $ 394,141 Provision for loans losses 21,429 0 0 0 21,429 Other income 53,409 42,329 3,143 0 98,881 Other expense 215,935 42,744 12,952 0 271,631 Income taxes 73,214 (39 ) (5,819 ) 0 67,356 Net income (loss) $ 143,875 $ (322 ) $ (10,947 ) $ 0 $ 132,606 Total assets (liabilities) $ 19,083,318 $ 350,483 $ (900 ) $ (302,923 ) $ 19,129,978 Average assets (liabilities) 17,180,219 187,118 (20,402 ) (159,291 ) 17,187,644

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 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 August 2018, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2018-14 715-20): No. 2018-14 No. 2018-14 In August 2018, the FASB issued ASU No. 2018-13 No. 2018-13 No. 2018-13 In June 2018, the FASB issued Accounting Standards Update (ASU) No. 2018-07 non-employees non-employee No. 2018-07 No. 2018-07 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 No. 2017-07, No. 2017-07 No. 2017-07 No. 2017-07 In January 2017, the FASB issued ASU No. 2017-04, No. 2017-04 No. 2017-04 In January 2017, the FASB issued ASU No. 2017-01, No. 2017-01 No. 2017-01 In August 2016, the FASB issued ASU No. 2016-15, No. 2016-15 No. 2016-15 No. 2016-15 In June 2016, the FASB issued ASU No. 2016-13, No. 2016-13 available-for-sale No. 2016-13 No. 2016-13 In March 2016, the FASB issued ASU No. 2016-09, No. 2016-09 No. 2016-09 No. 2016-09 tax-related No. 2016-09 In February 2016, the FASB issued ASU No. 2016-02, No. 2016-02 No. 2016-02 right-of-use No. 2018-11 non-lease non-lease No. 2018-10 2018-10 The Company is currently assessing the impact of the adoption of ASU No. 2016-02 In January 2016, the FASB issued ASU No. 2016-01, 2016-01 No. 2016-01 available-for-sale No. 2016-01 In May 2014, the FASB issued ASU No. 2014-09, No. 2014-09 No. 2014-09 No. 2014-09 No. 2014-09 No. 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)	9 Months Ended
	Sep. 30, 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, 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 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 24,774 Core deposit intangibles 28,724 George Mason trade name intangible 1,080 Other assets 135,383 Total identifiable assets $ 4,070,235 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 Fair value of net assets acquired including identifiable intangible assets 362,334 Resulting goodwill $ 612,920

Investment Securities (Tables)

Investment Securities (Tables)	9 Months Ended
	Sep. 30, 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. September 30, 2018 Amortized Gross Gross Estimated Cumulative U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 103,237 $ 0 $ 1,672 $ 101,565 $ 0 State and political subdivisions 258,656 440 6,850 252,246 0 Residential mortgage-backed securities Agency 973,307 541 30,201 943,647 0 Non-agency 4,086 486 0 4,572 86 Commercial mortgage-backed securities Agency 557,211 71 13,630 543,652 0 Asset-backed securities 223,350 638 386 223,602 0 Trust preferred collateralized debt obligations 6,176 253 275 6,154 2,586 Single issue trust preferred securities 8,748 127 771 8,104 0 Other corporate securities 96,113 51 1,139 95,025 0 Total $ 2,230,884 $ 2,607 $ 54,924 $ 2,178,567 $ 2,672 December 31, 2017 Amortized Gross Gross Estimated Cumulative 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 September 30, 2018 Fair Value Unrealized Fair Value Unrealized U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 89,255 $ 1,233 $ 12,311 $ 439 State and political subdivisions 127,202 2,166 80,886 4,684 Residential mortgage-backed securities Agency 612,343 15,591 300,669 14,610 Non-agency 0 0 0 0 Commercial mortgage-backed securities Agency 318,487 7,693 209,241 5,937 Asset-backed securities 92,432 386 0 0 Trust preferred collateralized debt obligations 0 0 2,225 275 Single issue trust preferred securities 0 0 4,950 771 Other corporate securities 78,095 1,139 0 0 Total $ 1,317,814 $ 28,208 $ 610,282 $ 26,716 Less than 12 months 12 months or longer December 31, 2017 Fair Value Unrealized Fair Value Unrealized 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 September 30 Nine Months Ended September 30 2018 2017 2018 2017 Proceeds from sales and calls $ 109,093 $ 64,257 $ 283,953 $ 631,561 Gross realized gains 93 1,781 1,314 2,840 Gross realized losses 207 1,314 1,604 1,396
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 September 30 Nine Months Ended September 30 2018 2017 2018 2017 Balance of cumulative credit losses at beginning of period $ 3,199 $ 22,162 $ 18,060 $ 22,162 Reductions for securities sold or paid off during the period 0 (4,102 ) (14,861 ) (4,102 ) Balance of cumulative credit losses at end of period $ 3,199 $ 18,060 $ 3,199 $ 18,060
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: September 30, 2018 Amortized Gross Gross Estimated U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 5,103 $ 132 $ 0 $ 5,235 State and political subdivisions 5,798 8 1 5,805 Residential mortgage-backed securities Agency 21 2 0 23 Single issue trust preferred securities 9,409 0 873 8,536 Other corporate securities 20 0 0 20 Total $ 20,351 $ 142 $ 874 $ 19,619 December 31, 2017 Amortized Gross Gross Estimated 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 the adoption of ASU No. 2016-01 Three Months September 30, Nine Months September 30, Net losses recognized during the period $ (38 ) $ (102 ) Net losses recognized during the period on equity securities sold (2 ) (4 ) Unrealized gains recognized during the period on equity securities still held at period end 0 50 Unrealized losses recognized during the period on equity securities still held at period end 36 148
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. September 30, 2018 December 31, 2017 Amortized Estimated Amortized Estimated Due in one year or less $ 76,698 $ 76,346 $ 50,311 $ 50,212 Due after one year through five years 500,052 490,797 386,039 384,585 Due after five years through ten years 466,155 451,981 400,129 398,208 Due after ten years 1,187,979 1,159,443 1,054,493 1,045,873 Marketable equity securities 0 0 9,712 9,878 Total $ 2,230,884 $ 2,178,567 $ 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. September 30, 2018 December 31, 2017 Amortized Estimated Amortized Estimated Due in one year or less $ 7,103 $ 7,235 $ 0 $ 0 Due after one year through five years 2,158 2,163 9,344 9,660 Due after five years through ten years 8,093 7,610 5,663 5,343 Due after ten years 2,997 2,611 5,421 5,015 Total $ 20,351 $ 19,619 $ 20,428 $ 20,018

Loans (Tables)

Loans (Tables)	9 Months Ended
	Sep. 30, 2018
Receivables [Abstract]
Major Classes of Loans	Major classes of loans are as follows: September 30, 2018 December 31, Commercial, financial and agricultural: Owner-occupied commercial real estate $ 1,336,434 $ 1,361,629 Nonowner-occupied commercial real estate 4,341,501 4,451,298 Other commercial loans 1,932,919 1,998,979 Total commercial, financial & agricultural 7,610,854 7,811,906 Residential real estate 3,387,268 2,996,171 Construction & land development 1,379,985 1,504,907 Consumer: Bankcard 9,530 10,314 Other consumer 899,074 704,039 Total gross loans $ 13,286,711 $ 13,027,337
Activity for Accretable Yield	Activity for the accretable yield for the first nine months of 2018 follows: Accretable yield at the beginning of the period $ 39,098 Accretion (including cash recoveries) (8,371 ) Additions 691 Net reclassifications to accretable from non-accretable 9,112 Disposals (including maturities, foreclosures, and charge-offs) (3,323 ) Accretable yield at the end of the period $ 37,207

Credit Quality (Tables)

Credit Quality (Tables)	9 Months Ended
	Sep. 30, 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 have been restructured during the three months ended September 30, 2018, segregated by class of loans. No loans were restructured during the three months ended September 30, 2017. Troubled Debt Restructurings For the Three Months Ended September 30, 2018 Number Pre-Modification Post- Commercial real estate: Owner-occupied 0 $ 0 $ 0 Nonowner-occupied 0 0 0 Other commercial 5 7,420 7,364 Residential real estate 1 272 272 Construction & land development 0 0 0 Consumer: Bankcard 0 0 0 Other consumer 0 0 0 Total 6 $ 7,692 $ 7,636 The following table sets forth United’s troubled debt restructurings that have been restructured during the nine months ended September 30, 2018 and 2017, segregated by class of loans: Troubled Debt Restructurings For the Nine Months Ended September 30, 2018 September 30, 2017 Number Pre-Modification Post- Number Pre-Modification Post- Commercial real estate: Owner-occupied 0 $ 0 $ 0 1 $ 5,333 $ 5,333 Nonowner-occupied 0 0 0 0 0 0 Other commercial 9 16,992 16,890 8 24,102 22,291 Residential real estate 3 7,225 7,225 0 0 0 Construction & land development 0 0 0 1 1,456 1,400 Consumer: Bankcard 0 0 0 0 0 0 Other consumer 0 0 0 0 0 0 Total 12 $ 24,217 $ 24,115 10 $ 30,891 $ 29,024
Schedule of Charged-off Troubled Debt Restructurings on Financing Receivables	The following table presents troubled debt restructurings, by class of loan, that had charge-offs during the three months and nine months ended September 30, 2018. Three Months Ended September 30, 2018 Nine Months Ended September 30, 2018 (In thousands) Number Recorded Number Recorded Troubled Debt Restructurings Commercial real estate: Owner-occupied 0 $ 0 0 $ 0 Nonowner-occupied 0 0 0 0 Other commercial 1 622 1 622 Residential real estate 0 0 0 0 Construction & land development 0 0 0 0 Consumer: Bankcard 0 0 0 0 Other consumer 0 0 0 0 Total 1 $ 622 1 $ 622
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 September 30, 2018 30-89 90 Days or Total Past Current & Total Financing Recorded Commercial real estate: Owner-occupied $ 11,089 $ 18,009 $ 29,098 $ 1,307,336 $ 1,336,434 $ 1,431 Nonowner-occupied 17,182 17,557 34,739 4,306,762 4,341,501 2,015 Other commercial 7,413 49,467 56,880 1,876,039 1,932,919 1,326 Residential real estate 35,646 30,519 66,165 3,321,103 3,387,268 9,941 Construction & land development 3,406 17,069 20,475 1,359,510 1,379,985 642 Consumer: Bankcard 649 177 826 8,704 9,530 177 Other consumer 7,874 763 8,637 890,437 899,074 502 Total $ 83,259 $ 133,561 $ 216,820 $ 13,069,891 $ 13,286,711 $ 16,034 (1) Other includes loans with a recorded investment of $155,526 acquired and accounted for under ASC Topic 310-30 Age Analysis of Past Due Loans As of December 31, 2017 (In thousands) 30-89 90 Days or Total Past Current & Total Financing Recorded 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 September 30, 2018 December 31, 2017 Commercial real estate: Owner-occupied $ 16,578 $ 13,205 Nonowner-occupied 15,542 19,814 Other commercial 48,141 67,536 Residential real estate 20,578 22,118 Construction & land development 16,427 16,805 Consumer: Bankcard 0 0 Other consumer 261 193 Total $ 117,527 $ 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 September 30, 2018 Commercial Real Estate Owner- Nonowner- Other Construction & Grade: Pass $ 1,266,769 $ 4,197,966 $ 1,827,465 $ 1,302,968 Special mention 15,221 60,293 13,528 4,715 Substandard 54,444 83,242 90,023 72,302 Doubtful 0 0 1,903 0 Total $ 1,336,434 $ 4,341,501 $ 1,932,919 $ 1,379,985 As of December 31, 2017 Commercial Real Estate Owner- Nonowner- Other Construction & 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 September 30, 2018 Residential Bankcard Other Grade: Pass $ 3,322,863 $ 8,704 $ 890,411 Special mention 17,309 649 7,879 Substandard 47,096 177 784 Doubtful 0 0 0 Total $ 3,387,268 $ 9,530 $ 899,074 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 September 30, 2018 December 31, 2017 Recorded Unpaid Related Recorded Unpaid Related With no related allowance recorded: Commercial real estate: Owner-occupied $ 58,367 $ 58,532 $ 0 $ 78,117 $ 78,419 $ 0 Nonowner-occupied 98,912 98,971 0 134,136 134,195 0 Other commercial 60,602 63,069 0 46,993 49,552 0 Residential real estate 33,190 34,041 0 26,751 28,202 0 Construction & land development 36,576 40,673 0 52,279 59,691 0 Consumer: Bankcard 0 0 0 0 0 0 Other consumer 23 23 0 15 15 0 With an allowance recorded: Commercial real estate: Owner-occupied $ 9,990 $ 9,990 $ 2,560 $ 9,132 $ 9,132 $ 2,251 Nonowner-occupied 14,468 14,468 2,683 7,797 7,797 1,592 Other commercial 50,454 59,052 16,500 60,512 70,396 16,721 Residential real estate 17,853 19,295 3,115 9,813 10,418 1,552 Construction & land development 16,816 19,470 2,494 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 $ 68,357 $ 68,522 $ 2,560 $ 87,249 $ 87,551 $ 2,251 Nonowner-occupied 113,380 113,439 2,683 141,933 141,992 1,592 Other commercial 111,056 122,121 16,500 107,505 119,948 16,721 Residential real estate 51,043 53,336 3,115 36,564 38,620 1,552 Construction & land development 53,392 60,143 2,494 53,662 61,074 229 Consumer: Bankcard 0 0 0 0 0 0 Other consumer 23 23 0 15 15 0 Impaired Loans For the Three Months Ended September 30, 2018 September 30, 2017 Average Interest Average Interest With no related allowance recorded: Commercial real estate: Owner-occupied $ 65,625 $ 365 $ 74,111 $ 374 Nonowner-occupied 99,005 311 148,753 178 Other commercial 56,489 313 57,302 148 Residential real estate 28,753 144 21,772 58 Construction & land development 41,036 278 42,240 348 Consumer: Bankcard 0 0 0 0 Other consumer 23 0 25 0 With an allowance recorded: Commercial real estate: Owner-occupied $ 7,378 $ 6 $ 11,442 $ 78 Nonowner-occupied 12,465 189 13,111 10 Other commercial 47,563 305 71,886 42 Residential real estate 14,975 57 15,276 16 Construction & land development 9,408 20 1,602 21 Consumer: Bankcard 0 0 0 0 Other consumer 0 0 0 0 Total: Commercial real estate: Owner-occupied $ 73,003 $ 371 $ 85,553 $ 452 Nonowner-occupied 111,470 500 161,864 188 Other commercial 104,052 618 129,188 190 Residential real estate 43,728 201 37,048 74 Construction & land development 50,444 298 43,842 369 Consumer: Bankcard 0 0 0 0 Other consumer 23 0 25 0 Impaired Loans For the Nine Months Ended September 30, 2018 September 30, 2017 Average Interest Average Interest With no related allowance recorded: Commercial real estate: Owner-occupied $ 69,009 $ 1,101 $ 70,477 $ 1,227 Nonowner-occupied 105,199 928 121,811 551 Other commercial 55,124 1,020 57,047 632 Residential real estate 27,210 501 21,397 219 Construction & land development 43,464 707 40,344 1,046 Consumer: Bankcard 0 0 0 0 Other consumer 29 0 29 0 With an allowance recorded: Commercial real estate: Owner-occupied $ 6,876 $ 18 $ 12,141 $ 393 Nonowner-occupied 11,158 251 13,492 108 Other commercial 47,736 380 71,736 685 Residential real estate 13,946 247 14,904 58 Construction & land development 6,944 60 2,195 63 Consumer: Bankcard 0 0 0 0 Other consumer 0 0 0 0 Total: Commercial real estate: Owner-occupied $ 75,885 $ 1,119 $ 82,618 $ 1,620 Nonowner-occupied 116,357 1,179 135,303 659 Other commercial 102,860 1,400 128,783 1,317 Residential real estate 41,156 748 36,301 277 Construction & land development 50,408 767 42,539 1,109 Consumer: Bankcard 0 0 0 0 Other consumer 29 0 29 0

Allowance for Credit Losses (Ta

Allowance for Credit Losses (Tables)	9 Months Ended
	Sep. 30, 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 For the Three Months Ended September 30, 2018 Commercial Real Other Residential Construction & Consumer Allowance for Total Owner- Nonowner- Allowance for Loan Losses: Beginning balance $ 3,213 $ 6,183 $ 48,191 $ 10,380 $ 6,592 $ 2,419 $ 157 $ 77,135 Charge-offs 1,478 0 4,432 365 110 659 0 7,044 Recoveries 415 395 394 558 134 146 0 2,042 Provision 2,391 22 291 1,067 480 575 (18 ) 4,808 Ending balance $ 4,541 $ 6,600 $ 44,444 $ 11,640 $ 7,096 $ 2,481 $ 139 $ 76,941 Allowance for Loan Losses and Carrying Amount of Loans For the Nine Months Ended September 30, 2018 Commercial Real Estate Other Residential Construction & Consumer Allowance for Total Owner- Nonowner- Allowance for Loan Losses: Beginning balance $ 5,401 $ 6,369 $ 45,189 $ 9,927 $ 7,187 $ 2,481 $ 73 $ 76,627 Charge-offs 3,221 314 13,095 1,357 642 1,985 0 20,614 Recoveries 1,160 548 1,484 916 145 485 0 4,738 Provision 1,201 (3 ) 10,866 2,154 406 1,500 66 16,190 Ending balance $ 4,541 $ 6,600 $ 44,444 $ 11,640 $ 7,096 $ 2,481 $ 139 $ 76,941 Ending Balance: individually evaluated for impairment $ 2,560 $ 2,683 $ 16,500 $ 3,116 $ 2,494 $ 0 $ 0 $ 27,353 Ending Balance: collectively evaluated for impairment $ 1,981 $ 3,917 $ 27,944 $ 8,524 $ 4,602 $ 2,481 $ 139 $ 49,588 Ending Balance: loans acquired with deteriorated credit quality $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 Financing receivables: Ending balance $ 1,336,434 $ 4,341,501 $ 1,932,919 $ 3,387,268 $ 1,379,985 $ 908,604 $ 0 $ 13,286,711 Ending Balance: individually evaluated for impairment $ 29,391 $ 22,768 $ 73,544 $ 19,994 $ 16,875 $ 0 $ 0 $ 162,572 Ending Balance: collectively evaluated for impairment $ 1,284,114 $ 4,250,305 $ 1,830,646 $ 3,351,837 $ 1,343,130 $ 908,581 $ 0 $ 12,968,613 Ending Balance: loans acquired with deteriorated credit quality $ 22,929 $ 68,428 $ 28,729 $ 15,437 $ 19,980 $ 23 $ 0 $ 155,526 Allowance for Loan Losses and Carrying Amount of Loans For the Year Ended December 31, 2017 Commercial Real Estate Other Residential Construction & Consumer Allowance for Total Owner- Nonowner- 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)	9 Months Ended
	Sep. 30, 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: September 30, 2018 Community Banking Mortgage Banking Total Gross Accumulated Gross Accumulated Gross Accumulated Amortized intangible assets: Core deposit intangible assets $ 98,359 ($ 60,482 ) $ 0 ($ 0 ) $ 98,359 ($ 60,482 ) Non-amortized George Mason trade name $ 0 $ 1,080 $ 1,080 Goodwill not subject to amortization $ 1,472,699 $ 5,315 $ 1,478,014 December 31, 2017 Community Banking Mortgage Banking Total Gross Accumulated Gross Accumulated Gross Accumulated 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 Mortgage Total Goodwill at December 31, 2017 $ 1,473,265 $ 5,115 $ 1,478,380 Addition to goodwill from Cardinal acquisition (566 ) 200 (366 ) Goodwill at September 30, 2018 $ 1,472,699 $ 5,315 $ 1,478,014
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)	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Schedule of Maturities of Long-term Borrowings	The scheduled maturities of these FHLB borrowings are as follows: Year Amount 2018 $ 970,890 2019 187,224 2020 41,779 2021 52,667 2022 and thereafter 32,221 Total $ 1,284,781

Derivative Financial Instrume_2

Derivative Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 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 September 30, 2018 and December 31, 2017. Asset Derivatives September 30, 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 $ 86,655 $ 4,042 Other assets $ 71,831 $ 538 Total derivatives designated as hedging instruments $ 86,655 $ 4,042 $ 71,831 $ 538 Derivatives not designated as hedging instruments Forward loan sales commitments Other assets $ 0 $ 0 Other assets $ 31,024 $ 2 TBA mortgage-backed securities Other assets 223,500 1,161 0 0 Interest rate lock commitments Other assets 135,069 3,991 Other assets 148,866 4,559 Total derivatives not designated as hedging instruments $ 358,569 $ 5,152 $ 179,890 $ 4,561 Total asset derivatives $ 445,224 $ 9,194 $ 251,721 $ 5,099 Liability Derivatives September 30, 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 Forward loan sales commitments Other liabilities $ 22,521 $ 197 Other liabilities $ 0 $ 0 TBA mortgage-backed securities Other liabilities $ 0 $ 0 Other liabilities 236,500 312 Interest rate lock commitments Other liabilities 0 0 Other liabilities 0 0 Total derivatives not designated as hedging instruments $ 22,521 $ 197 $ 236,500 $ 312 Total liability derivatives $ 22,521 $ 197 $ 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 and nine months ended September 30, 2018 and 2017 are presented as follows: Three Months Ended Income Statement Location September 30, September 30, Derivatives in hedging relationships Fair Value Hedges: Interest rate swap contracts Interest income/(expense) $ (24 ) $ (208 ) Total derivatives in hedging relationships $ (24 ) $ (208 ) Derivatives not designated as hedging instruments Forward loan sales commitments Income from Mortgage (197 ) (257 ) TBA mortgage-backed securities Income from Mortgage 2,583 123 Interest rate lock commitments Income from Mortgage (3,262 ) (4,484 ) Total derivatives not designated as hedging instruments $ (876 ) $ (4,618 ) Total derivatives $ (900 ) $ (4,826 ) Nine Months Ended Income Statement Location September 30, September 30, Derivatives in fair value hedging relationships Fair Value Hedges: Interest rate swap contracts Interest income/(expense) $ (42 ) $ (648 ) Cash Flow Hedges: Forward loan sales commitments Other income 0 0 Total derivatives in hedging relationships $ (42 ) $ (648 ) Derivatives not designated as hedging instruments Forward loan sales commitments Income from Mortgage (12 ) (427 ) TBA mortgage-backed securities Income from Mortgage 1,473 2,907 Interest rate lock commitments Income from Mortgage (1,643 ) (3,465 ) Total derivatives not designated as hedging instruments $ (182 ) $ (985 ) Total derivatives $ (224 ) $ (1,633 )

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 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 September 30, 2018 and December 31, 2017, segregated by the level of the valuation inputs within the fair value hierarchy. Fair Value at September 30, 2018 Using Description Balance as of September 30, 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 $ 101,565 $ 0 $ 101,565 $ 0 State and political subdivisions 252,246 0 252,246 0 Residential mortgage-backed securities Agency 943,647 0 943,647 0 Non-agency 4,572 0 4,572 0 Commercial mortgage-backed securities Agency 543,652 0 543,652 0 Asset-backed securities 223,602 0 223,602 0 Trust preferred collateralized debt obligations 6,154 0 0 6,154 Single issue trust preferred securities 8,104 0 8,104 0 Other corporate securities 95,025 6,879 88,146 0 Total available for sale securities 2,178,567 6,879 2,165,534 6,154 Equity securities: Financial services industry 173 173 0 0 Equity mutual funds (1) 5,073 5,073 0 0 Other equity securities 4,599 4,599 0 0 Total equity securities 9,845 9,845 0 0 Loans held for sale 231,310 0 0 231,310 Derivative financial assets: Interest rate swap contracts 4,042 0 4,042 0 Forward sales commitments 0 0 0 0 Interest rate lock commitments 3,991 0 0 3,991 TBA mortgage-backed securities 1,161 0 1,161 0 Total derivative financial assets 9,194 0 5,203 3,991 Liabilities Derivative financial liabilities: Forward sales commitments 197 0 197 0 Total derivative financial liabilities 197 0 197 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 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 September 30, 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 September 30, 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 1,157 8,757 Purchases, issuances, and settlements 0 0 Sales (29,300 ) (8,049 ) Transfers in and/or out of Level 3 0 0 Balance, end of period $ 6,154 $ 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 September 30, 2018 December 31, Balance, beginning of period $ 263,308 $ 0 Acquired in Cardinal merger 0 271,301 Originations 2,089,366 2,333,927 Sales (2,148,777 ) (2,408,945 ) Total gains or losses during the period recognized in earnings 54,829 58,132 Transfers in and/or out of Level 3 (27,416 ) 8,893 Balance, end of period $ 231,310 $ 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 September 30, 2018 December 31, Balance, beginning of period $ 4,559 $ 0 Acquired in Cardinal merger 0 10,393 Transfers other (568 ) (5,834 ) Balance, end of period $ 3,991 $ 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 September 30, Three Months September 30, Assets Loans held for sale Income from mortgage banking activities $ (5,929 ) $ (5,090 ) Description Nine Months September 30, Nine Months September 30, Assets Loans held for sale Income from mortgage banking activities $ (2,838 ) $ (7,529 )
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: September 30, 2018 December 31, 2017 Description Unpaid Fair Fair Value Unpaid Fair Fair Value Assets Loans held for sale $ 227,943 $ 231,310 $ 3,367 $ 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: Description Balance as of September 30, Carrying value at September 30, 2018 YTD Losses Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets Loans held for sale $ 2,886 $ 0 $ 2,886 $ 0 $ 0 Impaired Loans 109,582 0 98,171 11,411 4,177 OREO 18,786 0 18,786 0 796 Description Balance as of December 31, Carrying value at December 31, 2017 YTD Losses Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) 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) September 30, 2018 Cash and cash equivalents $ 1,254,686 $ 1,254,686 $ 0 $ 1,254,686 $ 0 Securities available for sale 2,178,567 2,178,567 6,879 2,165,534 6,154 Securities held to maturity 20,351 19,619 0 16,599 3,020 Equity securities 9,845 9,845 9,845 0 0 Other securities 166,749 166,749 0 0 166,749 Loans held for sale 234,196 234,196 0 2,886 231,310 Loans 13,199,799 12,488,175 0 0 12,488,175 Derivative financial assets 9,194 9,194 0 5,203 3,991 Deposits 14,091,172 14,052,668 0 14,052,668 0 Short-term borrowings 379,508 379,508 0 379,508 0 Long-term borrowings 1,319,371 1,293,611 0 1,293,611 0 Derivative financial liabilities 197 197 0 197 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)	9 Months Ended
	Sep. 30, 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 September 30, 2018, and the changes during the first nine months of 2018 are presented below: Nine Months Ended September 30, 2018 Shares Aggregate Intrinsic Value Weighted Average Remaining Contractual Term (Yrs.) Exercise Price Outstanding at January 1, 2018 1,558,438 $ 31.09 Granted 276,192 37.60 Exercised (60,161 ) 23.03 Forfeited or expired (24,007 ) 32.66 Outstanding at September 30, 2018 1,750,462 $ 9,624,912 5.8 $ 32.36 Exercisable at September 30, 2018 1,169,402 $ 9,508,502 4.4 $ 28.78
Changes to United's Restricted Common Shares	The following table summarizes the status of United’s nonvested stock option awards during the first nine months of 2018: Shares Weighted-Average Nonvested at January 1, 2018 507,871 $ 7.89 Granted 276,192 7.56 Vested (187,815 ) 7.53 Forfeited or expired (15,188 ) 7.67 Nonvested at September 30, 2018 581,060 $ 7.86
Status of United's Nonvested Stock Option Awards	The following summarizes the changes to United’s restricted common shares for the period ended September 30, 2018: Number Weighted-Average Outstanding at January 1, 2018 170,496 $ 40.05 Granted 97,004 37.60 Vested (62,411 ) 37.59 Forfeited (4,253 ) 38.42 Outstanding at September 30, 2018 200,836 $ 39.67

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	9 Months Ended
	Sep. 30, 2018
Retirement Benefits [Abstract]
Net Periodic Pension Cost	Net periodic pension cost for the three and nine months ended September 30, 2018 and 2017 included the following components: Three Months Ended September 30 Nine Months Ended September 30 2018 2017 2018 2017 Service cost $ 673 $ 574 $ 1,997 $ 1,705 Interest cost 1,324 1,293 3,927 3,837 Expected return on plan assets (2,578 ) (2,072 ) (7,651 ) (6,148 ) Recognized net actuarial loss 1,174 1,111 3,485 3,298 Net periodic pension (benefit) cost $ 593 $ 906 $ 1,758 $ 2,692 Weighted-Average Assumptions: Discount rate 3.83 % 4.49 % 3.83 % 4.49 % Expected return on assets 7.00 % 7.00 % 7.00 % 7.00 % Rate of compensation increase (prior to age 45) 3.50 % 3.50 % 3.50 % 3.50 % Rate of compensation increase 3.00 % 3.00 % 3.00 % 3.00 %

Comprehensive Income (Tables)

Comprehensive Income (Tables)	9 Months Ended
	Sep. 30, 2018
Equity [Abstract]
Components of Total Comprehensive Income	The components of total comprehensive income for the three and nine months ended September 30, 2018 and 2017 are as follows: Three Months Ended Nine Months Ended September 30 September 30 2018 2017 2018 2017 Net Income $ 64,412 $ 56,738 $ 192,392 $ 132,606 Available for sale (“AFS”) securities: AFS securities with OTTI charges during the period 0 0 0 (60 ) Related income tax effect 0 0 0 22 Less: OTTI charges recognized in net income 0 0 0 60 Related income tax benefit 0 0 0 (22 ) Reclassification of previous noncredit OTTI to credit OTTI 0 0 0 0 Related income tax benefit 0 0 0 0 Net unrealized (losses) gains on AFS securities with OTTI 0 0 0 0 AFS securities – all other: Change in net unrealized gain on AFS securities arising during the period (9,995 ) 3,584 (42,696 ) 14,846 Related income tax effect 2,329 (1,326 ) 11,621 (5,493 ) Net reclassification adjustment for (gains) losses included in net income 114 (467 ) 290 (1,444 ) Related income tax expense (benefit) (27 ) 173 (68 ) 534 (7,579 ) 1,964 (30,853 ) 8,443 Net effect of AFS securities on other comprehensive income (7,579 ) 1,964 (30,853 ) 8,443 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 6 6 Related income tax expense (0 ) (0 ) (2 ) (2 ) Net effect of HTM securities on other comprehensive income 2 2 4 4 Pension plan: Recognized net actuarial loss 1,174 1,111 3,485 3,298 Related income tax benefit (256 ) (394 ) (782 ) (1,191 ) Net effect of change in pension plan asset on other comprehensive income 918 717 2,703 2,107 Total change in other comprehensive income (6,659 ) 2,683 (28,146 ) 10,554 Total Comprehensive Income $ 57,753 $ 59,421 $ 164,246 $ 143,160
Components of Accumulated Other Comprehensive Income	The components of accumulated other comprehensive income for the nine months ended September 30, 2018 are as follows: Changes in Accumulated Other Comprehensive Income (AOCI) by Component (a) For the Nine Months Ended September 30, 2018 Unrealized Accretion 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 ) 0 0 (136 ) Reclass due to adopting Accounting Standard Update 2018-02 (1,632 ) 0 (4,721 ) (6,353 ) Other comprehensive income before reclassification (31,075 ) 4 0 (31,071 ) Amounts reclassified from accumulated other comprehensive income 222 0 2,703 2,925 Net current-period other comprehensive income, net of tax (30,853 ) 4 2,703 (28,146 ) Balance at September 30, 2018 ($ 38,825 ) ($ 42 ) ($ 37,793 ) ($ 76,660 ) (a) All amounts are net-of-tax.
Reclassifications Out of Accumulated Other Comprehensive Income	Reclassifications out of Accumulated Other Comprehensive Income (AOCI) For the Nine Months Ended September 30, 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 to credit OTTI $ 0 Net investment securities (losses) gains Net reclassification adjustment for losses (gains) included in net income 290 Net investment securities (losses) gains 290 Total before tax Related income tax effect (68 ) Tax expense 222 Net of tax Pension plan: Recognized net actuarial loss 3,485 (a) 3,485 Total before tax Related income tax effect (782 ) Tax expense 2,703 Net of tax Total reclassifications for the period $ 2,925 (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)	9 Months Ended
	Sep. 30, 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 Nine Months Ended September 30 September 30 2018 2017 2018 2017 Distributed earnings allocated to common stock $ 35,234 $ 34,587 $ 106,429 $ 95,871 Undistributed earnings allocated to common stock 29,060 22,065 85,617 36,518 Net earnings allocated to common shareholders $ 64,294 $ 56,652 $ 192,046 $ 132,389 Average common shares outstanding 103,617,590 104,760,153 104,382,094 95,040,664 Equivalents from stock options 316,369 307,969 297,782 409,962 Average diluted shares outstanding 103,933,959 105,068,122 104,679,876 95,450,626 Earnings per basic common share $ 0.62 $ 0.54 $ 1.84 $ 1.39 Earnings per diluted common share $ 0.62 $ 0.54 $ 1.83 $ 1.39

Variable Interest Entities (Tab

Variable Interest Entities (Tables)	9 Months Ended
	Sep. 30, 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 LIBOR + 2.85% 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 September 30, 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 $ 257,873 $ 248,921 $ 8,952 $ 266,669 $ 257,674 $ 8,995

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 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 and nine months ended September 30, 2018 and 2017 is as follows: At and For the Three Months Ended September 30, 2018 Community Mortgage Other Intersegment Eliminations Consolidated Net interest income $ 149,770 $ 388 $ (3,168 ) $ 1,785 $ 148,775 Provision for loans losses 4,808 0 0 0 4,808 Other income 18,717 16,478 58 (3,567 ) 31,686 Other expense 75,255 17,957 1,885 (1,782 ) 93,315 Income taxes 19,296 (246 ) (1,124 ) 0 17,926 Net income (loss) $ 69,128 $ (845 ) $ (3,871 ) $ 0 $ 64,412 Total assets (liabilities) $ 19,080,734 $ 288,638 $ 12,545 $ (194,274 ) $ 19,187,643 Average assets (liabilities) 18,982,530 303,556 5,468 (243,867 ) 19,047,689 At and For the Three Months Ended September 30, 2017 Community Mortgage Other Intersegment Eliminations Consolidated Net interest income $ 152,886 $ (36 ) $ (2,574 ) $ 0 $ 150,276 Provision for loans losses 7,279 0 0 0 7,279 Other income 18,373 19,936 (80 ) 0 38,229 Other expense 74,553 24,036 (1,937 ) 0 96,652 Income taxes 29,490 (1,332 ) (322 ) 0 27,836 Net income (loss) $ 59,937 $ (2,804 ) $ (395 ) $ 0 $ 56,738 Total assets (liabilities) $ 19,083,318 $ 350,483 $ (900 ) $ (302,923 ) $ 19,129,978 Average assets (liabilities) 18,889,710 321,744 (13,994 ) (269,675 ) 18,927,785 At and For the Nine Months Ended September 30, 2018 Community Mortgage Other Intersegment Eliminations Consolidated Net interest income $ 444,840 $ 1,028 $ (8,794 ) $ 4,866 $ 441,940 Provision for loans losses 16,190 0 0 0 16,190 Other income 53,952 54,829 (696 ) (9,200 ) 98,885 Other expense 224,240 57,566 (295 ) (4,334 ) 277,177 Income taxes 57,519 (385 ) (2,068 ) 0 55,066 Net income (loss) $ 200,843 $ (1,324 ) $ (7,127 ) $ 0 $ 192,392 Total assets (liabilities) $ 19,080,734 $ 288,638 $ 12,545 $ (194,274 ) $ 19,187,643 Average assets (liabilities) 18,718,295 284,100 8,043 (240,505 ) 18,769,934 At and For the Nine Months Ended September 30, 2017 Community Mortgage Other Intersegment Eliminations Consolidated Net interest income $ 401,044 $ 54 $ (6,957 ) $ 0 $ 394,141 Provision for loans losses 21,429 0 0 0 21,429 Other income 53,409 42,329 3,143 0 98,881 Other expense 215,935 42,744 12,952 0 271,631 Income taxes 73,214 (39 ) (5,819 ) 0 67,356 Net income (loss) $ 143,875 $ (322 ) $ (10,947 ) $ 0 $ 132,606 Total assets (liabilities) $ 19,083,318 $ 350,483 $ (900 ) $ (302,923 ) $ 19,129,978 Average assets (liabilities) 17,180,219 187,118 (20,402 ) (159,291 ) 17,187,644

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Sep. 30, 2018	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
Accounting Standards Update 2016-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total future minimum lease payments for operating leases	$ 69,844

Mergers and Acquisitions - Addi

Mergers and Acquisitions - Additional Information (Detail) - USD ($)	Sep. 30, 2018	Apr. 21, 2017	Sep. 30, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Total assets at consummation	$ 19,187,643,000		$ 19,187,643,000	$ 19,058,959,000
Loans at consummation	13,286,711,000		13,286,711,000	13,027,337,000
Deposits at consummation	14,091,172,000		14,091,172,000	13,830,591,000
Resulting goodwill	1,478,014,000		1,478,014,000	$ 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		$ 612,920,000
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
Estimated remaining life of discount on trust preferred issuances acquired	15 years 11 months 19 days
Estimated remaining life of premium on interest-bearing deposits acquired	4 years
Estimated remaining life of the FHLB advances acquired	3 years 9 months 21 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			$ 519,747,000
Revenue since acquisition included in consolidated results			$ 270,914,000
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 - Sc_2

Mergers and Acquisitions - Schedule of Fair Value of Acquired Identifiable Assets and Liabilities Assumed (Detail) - USD ($) $ in Thousands	Apr. 21, 2017	Sep. 30, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Resulting goodwill		$ 1,478,014	$ 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	24,774
Other assets	135,383
Total identifiable assets	4,070,235
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
Fair value of net assets acquired including identifiable intangible assets	362,334
Resulting goodwill	612,920
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 - Sc_3

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

Investment Securities - Summary

Investment Securities - Summary of Amortized Cost and Estimated Fair Values of Available for Sale Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Schedule of Investments [Line Items]
Amortized Cost	$ 2,230,884	$ 1,900,684
Gross Unrealized Gains	2,607	8,924
Gross Unrealized Losses	54,924	20,852
Estimated Fair Value	2,178,567	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	103,237	114,735
Gross Unrealized Gains	0	385
Gross Unrealized Losses	1,672	362
Estimated Fair Value	101,565	114,758
Cumulative OTTI in AOCI	0	0
State and Political Subdivisions [Member]
Schedule of Investments [Line Items]
Amortized Cost	258,656	303,101
Gross Unrealized Gains	440	3,197
Gross Unrealized Losses	6,850	2,429
Estimated Fair Value	252,246	303,869
Cumulative OTTI in AOCI	0	0
Residential Mortgage-Backed Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	973,307	821,857
Gross Unrealized Gains	541	2,096
Gross Unrealized Losses	30,201	9,360
Estimated Fair Value	943,647	814,593
Cumulative OTTI in AOCI	0	0
Residential Mortgage-Backed Securities, Non-agency [Member]
Schedule of Investments [Line Items]
Amortized Cost	4,086	4,969
Gross Unrealized Gains	486	543
Gross Unrealized Losses	0	0
Estimated Fair Value	4,572	5,512
Cumulative OTTI in AOCI	86	86
Commercial Mortgage-Backed Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	557,211	457,107
Gross Unrealized Gains	71	1,059
Gross Unrealized Losses	13,630	3,309
Estimated Fair Value	543,652	454,857
Cumulative OTTI in AOCI	0	0
Asset-Backed Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	223,350	109,829
Gross Unrealized Gains	638	148
Gross Unrealized Losses	386	7
Estimated Fair Value	223,602	109,970
Cumulative OTTI in AOCI	0	0
Trust Preferred Collateralized Debt Obligations [Member]
Schedule of Investments [Line Items]
Amortized Cost	6,176	37,856
Gross Unrealized Gains	253	542
Gross Unrealized Losses	275	4,129
Estimated Fair Value	6,154	34,269
Cumulative OTTI in AOCI	2,586	20,770
Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	8,748	13,417
Gross Unrealized Gains	127	368
Gross Unrealized Losses	771	1,225
Estimated Fair Value	8,104	12,560
Cumulative OTTI in AOCI	0	0
Corporate Bonds [Member]
Schedule of Investments [Line Items]
Amortized Cost	96,113	28,101
Gross Unrealized Gains	51	407
Gross Unrealized Losses	1,139	18
Estimated Fair Value	95,025	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 - Summa_2

Investment Securities - Summary of Securities Available for Sale in an Unrealized Loss Position (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	$ 1,317,814	$ 897,752
Less than 12 months, Unrealized Losses	28,208	7,828
12 months or longer, Fair Value	610,282	369,074
12 months or longer, Unrealized Losses	26,716	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	89,255	36,678
Less than 12 months, Unrealized Losses	1,233	230
12 months or longer, Fair Value	12,311	22,920
12 months or longer, Unrealized Losses	439	132
State and Political Subdivisions [Member]
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	127,202	82,896
Less than 12 months, Unrealized Losses	2,166	566
12 months or longer, Fair Value	80,886	59,432
12 months or longer, Unrealized Losses	4,684	1,863
Residential Mortgage-Backed Securities [Member]
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	612,343	460,414
Less than 12 months, Unrealized Losses	15,591	4,621
12 months or longer, Fair Value	300,669	182,482
12 months or longer, Unrealized Losses	14,610	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 [Member]
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	318,487	282,858
Less than 12 months, Unrealized Losses	7,693	2,386
12 months or longer, Fair Value	209,241	70,763
12 months or longer, Unrealized Losses	5,937	923
Asset-Backed Securities [Member]
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	92,432	27,931
Less than 12 months, Unrealized Losses	386	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	2,225	28,629
12 months or longer, Unrealized Losses	275	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	4,950	4,485
12 months or longer, Unrealized Losses	771	1,225
Corporate Bonds [Member]
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	78,095	6,975
Less than 12 months, Unrealized Losses	1,139	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 - Summa_3

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		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Investments, Debt and Equity Securities [Abstract]
Proceeds from sales and calls	$ 109,093	$ 64,257	$ 283,953	$ 631,561
Gross realized gains	93	1,781	1,314	2,840
Gross realized losses	$ 207	$ 1,314	$ 1,604	$ 1,396

Investment Securities - Additio

Investment Securities - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2018USD ($)Securities	Dec. 31, 2017USD ($)	Sep. 30, 2017USD ($)
Schedule of Investments [Line Items]
Gross unrealized losses on available for sale securities	$ 54,924,000	$ 20,852,000
Available for sale securities in unrealized loss position | Securities	733
Available for sale securities in portfolio, number | Securities	865
Amortized cost of available for sale securities	$ 2,230,884,000	1,900,684,000
Capitalization of banks, equal to or greater than, in the single-issue trust preferred portfolio	10,000,000,000
Gross realized gains	0		$ 0
Gross realized losses	0		$ 0
Equity securities at estimated fair value	9,845,000	0
Carrying value of securities pledged	1,999,152,000	1,403,565,000
SunTrust Bank [Member]
Schedule of Investments [Line Items]
Amortized cost of trust preferred securities	7,432,000
Royal Bank of Scotland [Member]
Schedule of Investments [Line Items]
Amortized cost of trust preferred securities	977,000
Investment Grade [Member]
Schedule of Investments [Line Items]
Amortized cost of available for sale single issue trust preferred securities	3,028,000
Below Investment Grade [Member]
Schedule of Investments [Line Items]
Amortized cost of available for sale single issue trust preferred securities	5,720,000
State and Political Subdivisions [Member]
Schedule of Investments [Line Items]
Gross unrealized losses on available for sale securities	6,850,000	2,429,000
Amortized cost of available for sale securities	$ 258,656,000	303,101,000
Percent of portfolio with credit support	76.00%
Investment grade credit rate percentage	1.00%
Number of equity securities other-than-temporarily impaired | Securities	0
Trust Preferred Collateralized Debt Obligations [Member]
Schedule of Investments [Line Items]
Gross unrealized losses on available for sale securities	$ 275,000	4,129,000
Amortized cost of available for sale securities	6,176,000	37,856,000
Trust Preferred Collateralized Debt Obligations [Member] | TRUP CDOs [Member]
Schedule of Investments [Line Items]
Amortized cost of available for sale securities	6,176,000
Agency Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Amortized cost of available for sale securities	1,530,518,000
Commercial Mortgage-Backed Securities [Member]
Schedule of Investments [Line Items]
Gross unrealized losses on available for sale securities	13,630,000	3,309,000
Amortized cost of available for sale securities	557,211,000	457,107,000
Residential Mortgage-Backed Securities [Member]
Schedule of Investments [Line Items]
Gross unrealized losses on available for sale securities	30,201,000	9,360,000
Amortized cost of available for sale securities	973,307,000	821,857,000
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	4,086,000	4,969,000
Residential Mortgage-Backed Securities, Non-agency [Member] | Investment Grade [Member]
Schedule of Investments [Line Items]
Amortized cost of available for sale securities	170,000
Residential Mortgage-Backed Securities, Non-agency [Member] | Below Investment Grade [Member]
Schedule of Investments [Line Items]
Amortized cost of available for sale securities	3,916,000
Corporate Bonds [Member]
Schedule of Investments [Line Items]
Gross unrealized losses on available for sale securities	1,139,000	18,000
Amortized cost of available for sale securities	$ 96,113,000	$ 28,101,000
Number of equity securities other-than-temporarily impaired	0
Corporate Bonds [Member] | Debt Issuances of Corporations [Member]
Schedule of Investments [Line Items]
Amortized cost of available for sale securities	$ 96,113,000
Corporate Bonds [Member] | Investment Grade [Member]
Schedule of Investments [Line Items]
Percent of corporate securities portfolio	78.00%
Corporate Bonds [Member] | Below Investment Grade [Member]
Schedule of Investments [Line Items]
Percent of corporate securities portfolio	22.00%

Investment Securities - Roll Fo

Investment Securities - Roll Forward of Credit Losses on Securities (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Investments, Debt and Equity Securities [Abstract]
Cumulative credit losses, Beginning Balance	$ 3,199	$ 22,162	$ 18,060	$ 22,162
Reductions for securities sold or paid off during the period	0	(4,102)	(14,861)	(4,102)
Cumulative credit losses, Ending Balance	$ 3,199	$ 18,060	$ 3,199	$ 18,060

Investment Securities - Summa_4

Investment Securities - Summary of Maturities of Securities Available for Sale by Amortized Cost and Estimated Fair Value (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Due in one year or less, Amortized Cost	$ 76,698	$ 50,311
Due after one year through five years, Amortized Cost	500,052	386,039
Due after five years through ten years, Amortized Cost	466,155	400,129
Due after ten years, Amortized Cost	1,187,979	1,054,493
Marketable equity securities, Amortized Cost	0	9,712
Amortized Cost	2,230,884	1,900,684
Due in one year or less, Estimated Fair Value	76,346	50,212
Due after one year through five years, Estimated Fair Value	490,797	384,585
Due after five years through ten years, Estimated Fair Value	451,981	398,208
Due after ten years, Estimated Fair Value	1,159,443	1,045,873
Marketable equity securities, Estimated Fair Value	0	9,878
Total available for sale securities	$ 2,178,567	$ 1,888,756

Investment Securities - Summa_5

Investment Securities - Summary of Amortized Cost and Estimated Fair Values of Securities Held to Maturity (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Schedule of Investments [Line Items]
Amortized Cost	$ 20,351	$ 20,428
Gross Unrealized Gains	142	321
Gross Unrealized Losses	874	731
Estimated Fair Value	19,619	20,018
U.S. Treasury Securities and Obligations of U.S. Government Corporations and Agencies [Member]
Schedule of Investments [Line Items]
Amortized Cost	5,103	5,187
Gross Unrealized Gains	132	308
Gross Unrealized Losses	0	0
Estimated Fair Value	5,235	5,495
State and Political Subdivisions [Member]
Schedule of Investments [Line Items]
Amortized Cost	5,798	5,797
Gross Unrealized Gains	8	10
Gross Unrealized Losses	1	0
Estimated Fair Value	5,805	5,807
Residential Mortgage-Backed Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	21	23
Gross Unrealized Gains	2	3
Gross Unrealized Losses	0	0
Estimated Fair Value	23	26
Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	9,409	9,401
Gross Unrealized Gains	0	0
Gross Unrealized Losses	873	731
Estimated Fair Value	8,536	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 - Summa_6

Investment Securities - Summary of Maturities of Debt Securities Held to Maturity by Amortized Cost and Estimated Fair Value (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Due in one year or less, Amortized Cost	$ 7,103	$ 0
Due after one year through five years, Amortized Cost	2,158	9,344
Due after five years through ten years, Amortized Cost	8,093	5,663
Due after ten years, Amortized Cost	2,997	5,421
Amortized Cost	20,351	20,428
Due in one year or less, Estimated Fair Value	7,235	0
Due after one year through five years, Estimated Fair Value	2,163	9,660
Due after five years through ten year, Estimated Fair Value	7,610	5,343
Due after ten years, Estimated Fair Value	2,611	5,015
Estimated Fair Value, Total	$ 19,619	$ 20,018

Investment Securities - Summa_7

Investment Securities - Summary of Equity Securities (Detail) - Marketable Equity Securities [Member] - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2018
Debt Securities, Available-for-sale [Line Items]
Net losses recognized during the period	$ (38)	$ (102)
Net losses recognized during the period on equity securities sold	(2)	(4)
Unrealized gains recognized during the period on equity securities still held at period end	0	50
Unrealized losses recognized during the period on equity securities still held at period end	$ 36	$ 148

Loans - Major Classes of Loans

Loans - Major Classes of Loans (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Commercial, financial, and agricultural
Total commercial, financial & agricultural	$ 7,610,854	$ 7,811,906
Residential real estate	3,387,268	2,996,171
Construction & land development	1,379,985	1,504,907
Consumer:
Bankcard	9,530	10,314
Other consumer	899,074	704,039
Total Financing Receivables	13,286,711	13,027,337
Owner-Occupied [Member]
Commercial, financial, and agricultural
Total commercial, financial & agricultural	1,336,434	1,361,629
Nonowner-Occupied [Member]
Commercial, financial, and agricultural
Total commercial, financial & agricultural	4,341,501	4,451,298
Other Commercial [Member]
Commercial, financial, and agricultural
Total commercial, financial & agricultural	$ 1,932,919	$ 1,998,979

Loans - Additional Information

Loans - Additional Information (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Loans held for sale	$ 234,196	$ 265,955
Acquired impaired loans from merger	$ 13,286,711	$ 13,027,337
Percentage of acquired impaired loans from merger on total gross loans	1.17%	1.62%
Recorded investment in acquired impaired loans	$ 205,034	$ 285,964
Directors and Officers [Member]
Related party loans	25,826	36,360
Loans Acquired with Deteriorated Credit Quality [Member]
Acquired impaired loans from merger	$ 155,526	$ 210,521

Loans - Activity for Accretable

Loans - Activity for Accretable Yield (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 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)	(8,371)
Additions	691
Net reclassifications to accretable from non-accretable	9,112
Disposals (including maturities, foreclosures, and charge-offs)	(3,323)
Accretable yield at the end of the period	$ 37,207

Credit Quality - Additional Inf

Credit Quality - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
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		$ 63,626		$ 50,129
Restructured loans on nonaccrual status	$ 50,974	50,974		30,868
Restructured loans modified by reduction in interest	1,646	1,646
Restructured loan and interest	1,849	1,849
Restructured loans modified by change in terms	60,131	60,131
Restructured loans modified by reduction in interest rate and change in terms	7,636	$ 24,115	$ 29,024
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	18,786	$ 18,786		24,348
Recorded investment of consumer mortgage loans	569	569		873
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Restructured loans on nonaccrual status	85	85		95
Financing Receivables 30 To 89 Days Past Due [Member]
Restructured loans on nonaccrual status	$ 1,778	$ 1,778		$ 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	9 Months Ended
	Sep. 30, 2018USD ($)Contract	Sep. 30, 2018USD ($)Contract	Sep. 30, 2017USD ($)Contract
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	6	12	10
Pre-Modification Outstanding Recorded Investment	$ 7,692	$ 24,217	$ 30,891
Post-Modification Outstanding Recorded Investment	$ 7,636	$ 24,115	$ 29,024
Construction & Land Development [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	0	0	1
Pre-Modification Outstanding Recorded Investment	$ 0	$ 0	$ 1,456
Post-Modification Outstanding Recorded Investment	$ 0	$ 0	$ 1,400
Commercial Real Estate [Member] | Owner-Occupied [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	0	0	1
Pre-Modification Outstanding Recorded Investment	$ 0	$ 0	$ 5,333
Post-Modification Outstanding Recorded Investment	$ 0	$ 0	$ 5,333
Commercial Real Estate [Member] | Nonowner-Occupied [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	0	0	0
Pre-Modification Outstanding Recorded Investment	$ 0	$ 0	$ 0
Post-Modification Outstanding Recorded Investment	$ 0	$ 0	$ 0
Other Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	5	9	8
Pre-Modification Outstanding Recorded Investment	$ 7,420	$ 16,992	$ 24,102
Post-Modification Outstanding Recorded Investment	$ 7,364	$ 16,890	$ 22,291
Residential Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	1	3	0
Pre-Modification Outstanding Recorded Investment	$ 272	$ 7,225	$ 0
Post-Modification Outstanding Recorded Investment	$ 272	$ 7,225	$ 0
Consumer [Member] | Bankcard [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	0	0	0
Pre-Modification Outstanding Recorded Investment	$ 0	$ 0	$ 0
Post-Modification Outstanding Recorded Investment	$ 0	$ 0	$ 0
Consumer [Member] | Other Consumer [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	0	0	0
Pre-Modification Outstanding Recorded Investment	$ 0	$ 0	$ 0
Post-Modification Outstanding Recorded Investment	$ 0	$ 0	$ 0

Credit Quality - Schedule of Ch

Credit Quality - Schedule of Charged-off Troubled Debt Restructurings on Financing Receivables (Detail) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2018USD ($)Contract	Sep. 30, 2018USD ($)Contract
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	1	1
Recorded Investment | $	$ 622	$ 622
Construction & Land Development [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	0	0
Recorded Investment | $	$ 0	$ 0
Commercial Real Estate [Member] | Owner-Occupied [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	0	0
Recorded Investment | $	$ 0	$ 0
Commercial Real Estate [Member] | Nonowner-Occupied [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	0	0
Recorded Investment | $	$ 0	$ 0
Other Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	1	1
Recorded Investment | $	$ 622	$ 622
Residential Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	0	0
Recorded Investment | $	$ 0	$ 0
Consumer [Member] | Bankcard [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	0	0
Recorded Investment | $	$ 0	$ 0
Consumer [Member] | Other Consumer [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	0	0
Recorded Investment | $	$ 0	$ 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	Sep. 30, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, 30-89 Days Past Due	$ 83,259	$ 76,551
Loans, Total Past Due	216,820	226,119
Loans, Current & Other	13,069,891	12,801,218
Total Financing Receivables	13,286,711	13,027,337
Loans, Recorded Investment >90 Days & Accruing	16,034	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	133,561	149,568
Construction & Land Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, 30-89 Days Past Due	3,406	1,615
Loans, Total Past Due	20,475	18,805
Loans, Current & Other	1,359,510	1,486,102
Total Financing Receivables	1,379,985	1,504,907
Loans, Recorded Investment >90 Days & Accruing	642	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	17,069	17,190
Commercial Real Estate [Member] | Owner-Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, 30-89 Days Past Due	11,089	7,968
Loans, Total Past Due	29,098	21,631
Loans, Current & Other	1,307,336	1,339,998
Total Financing Receivables	1,336,434	1,361,629
Loans, Recorded Investment >90 Days & Accruing	1,431	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	18,009	13,663
Commercial Real Estate [Member] | Nonowner-Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, 30-89 Days Past Due	17,182	10,398
Loans, Total Past Due	34,739	30,846
Loans, Current & Other	4,306,762	4,420,452
Total Financing Receivables	4,341,501	4,451,298
Loans, Recorded Investment >90 Days & Accruing	2,015	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	17,557	20,448
Other Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, 30-89 Days Past Due	7,413	11,533
Loans, Total Past Due	56,880	80,009
Loans, Current & Other	1,876,039	1,918,970
Total Financing Receivables	1,932,919	1,998,979
Loans, Recorded Investment >90 Days & Accruing	1,326	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	49,467	68,476
Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, 30-89 Days Past Due	35,646	35,300
Loans, Total Past Due	66,165	63,937
Loans, Current & Other	3,321,103	2,932,234
Total Financing Receivables	3,387,268	2,996,171
Loans, Recorded Investment >90 Days & Accruing	9,941	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	30,519	28,637
Consumer [Member] | Bankcard [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, 30-89 Days Past Due	649	449
Loans, Total Past Due	826	635
Loans, Current & Other	8,704	9,679
Total Financing Receivables	9,530	10,314
Loans, Recorded Investment >90 Days & Accruing	177	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	177	186
Consumer [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, 30-89 Days Past Due	7,874	9,288
Loans, Total Past Due	8,637	10,256
Loans, Current & Other	890,437	693,783
Total Financing Receivables	899,074	704,039
Loans, Recorded Investment >90 Days & Accruing	502	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	$ 763	$ 968

Credit Quality - Schedule of _2

Credit Quality - Schedule of Age Analysis of its Past Due Loans, Segregated by Class of Loans (Parenthetical) (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Acquired impaired loans from merger	$ 13,286,711	$ 13,027,337
Loans Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Acquired impaired loans from merger	$ 155,526	$ 210,521

Credit Quality - Schedule of No

Credit Quality - Schedule of Nonaccrual Loans, Segregated by Class of Loans (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans on Nonaccrual Status	$ 117,527	$ 139,671
Construction & Land Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans on Nonaccrual Status	16,427	16,805
Commercial Real Estate [Member] | Owner-Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans on Nonaccrual Status	16,578	13,205
Commercial Real Estate [Member] | Nonowner-Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans on Nonaccrual Status	15,542	19,814
Other Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans on Nonaccrual Status	48,141	67,536
Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans on Nonaccrual Status	20,578	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	$ 261	$ 193

Credit Quality - Schedule of Cr

Credit Quality - Schedule of Credit Quality Indicators Information, by Class of Loans (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	$ 13,286,711	$ 13,027,337
Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	3,387,268	2,996,171
Other Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	1,932,919	1,998,979
Bankcard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	9,530	10,314
Other Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	899,074	704,039
Owner-Occupied [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	1,336,434	1,361,629
Nonowner-Occupied [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	4,341,501	4,451,298
Construction & Land Development [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	1,379,985	1,504,907
Pass [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	3,322,863	2,945,266
Pass [Member] | Other Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	1,827,465	1,848,868
Pass [Member] | Bankcard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	8,704	9,679
Pass [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	890,411	693,727
Pass [Member] | Owner-Occupied [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	1,266,769	1,276,088
Pass [Member] | Nonowner-Occupied [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	4,197,966	4,312,985
Pass [Member] | Construction & Land Development [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	1,302,968	1,413,706
Special Mention [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	17,309	18,025
Special Mention [Member] | Other Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	13,528	55,564
Special Mention [Member] | Bankcard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	649	449
Special Mention [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	7,879	9,334
Special Mention [Member] | Owner-Occupied [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	15,221	20,165
Special Mention [Member] | Nonowner-Occupied [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	60,293	57,618
Special Mention [Member] | Construction & Land Development [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	4,715	5,196
Substandard [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	47,096	32,880
Substandard [Member] | Other Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	90,023	90,625
Substandard [Member] | Bankcard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	177	186
Substandard [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	784	978
Substandard [Member] | Owner-Occupied [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	54,444	65,376
Substandard [Member] | Nonowner-Occupied [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	83,242	80,695
Substandard [Member] | Construction & Land Development [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	72,302	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	1,903	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		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Construction & Land Development [Member]
Financing Receivable, Impaired [Line Items]
Impaired Loans, Recorded Investment, With no related allowance recorded	$ 36,576		$ 36,576		$ 52,279
Impaired Loans, Unpaid Principal Balance, With no related allowance recorded	40,673		40,673		59,691
Impaired Loans, Recorded Investment, With an allowance recorded	16,816		16,816		1,383
Impaired Loans, Unpaid Principal Balance, With an allowance recorded	19,470		19,470		1,383
Impaired Loans, Related Allowance	2,494		2,494		229
Impaired Loans, Recorded Investment	53,392		53,392		53,662
Impaired Loans, Unpaid Principal Balance	60,143		60,143		61,074
Impaired Loans, Related Allowance	2,494		2,494		229
Impaired Loans, Average Recorded Investment, With no related allowance recorded	41,036	$ 42,240	43,464	$ 40,344
Impaired Loans, Interest Income Recognized, With no related allowance recorded	278	348	707	1,046
Impaired Loans, Average Recorded Investment, With an allowance recorded	9,408	1,602	6,944	2,195
Impaired Loans, Interest Income Recognized, With an allowance recorded	20	21	60	63
Impaired Loans, Average Recorded Investment	50,444	43,842	50,408	42,539
Impaired Loans, Interest Income Recognized	298	369	767	1,109
Bankcard [Member]
Financing Receivable, Impaired [Line Items]
Impaired Loans, Average Recorded Investment, With no related allowance recorded	0	0	0	0
Impaired Loans, Interest Income Recognized, With no related allowance recorded	0	0	0	0
Other Consumer [Member]
Financing Receivable, Impaired [Line Items]
Impaired Loans, Average Recorded Investment, With no related allowance recorded	23	25	29	29
Impaired Loans, Interest Income Recognized, With no related allowance recorded	0	0	0	0
Commercial Real Estate [Member] | Owner-Occupied [Member]
Financing Receivable, Impaired [Line Items]
Impaired Loans, Recorded Investment, With no related allowance recorded	58,367		58,367		78,117
Impaired Loans, Unpaid Principal Balance, With no related allowance recorded	58,532		58,532		78,419
Impaired Loans, Recorded Investment, With an allowance recorded	9,990		9,990		9,132
Impaired Loans, Unpaid Principal Balance, With an allowance recorded	9,990		9,990		9,132
Impaired Loans, Related Allowance	2,560		2,560		2,251
Impaired Loans, Recorded Investment	68,357		68,357		87,249
Impaired Loans, Unpaid Principal Balance	68,522		68,522		87,551
Impaired Loans, Related Allowance	2,560		2,560		2,251
Impaired Loans, Average Recorded Investment, With no related allowance recorded	65,625	74,111	69,009	70,477
Impaired Loans, Interest Income Recognized, With no related allowance recorded	365	374	1,101	1,227
Impaired Loans, Average Recorded Investment, With an allowance recorded	7,378	11,442	6,876	12,141
Impaired Loans, Interest Income Recognized, With an allowance recorded	6	78	18	393
Impaired Loans, Average Recorded Investment	73,003	85,553	75,885	82,618
Impaired Loans, Interest Income Recognized	371	452	1,119	1,620
Commercial Real Estate [Member] | Nonowner-Occupied [Member]
Financing Receivable, Impaired [Line Items]
Impaired Loans, Recorded Investment, With no related allowance recorded	98,912		98,912		134,136
Impaired Loans, Unpaid Principal Balance, With no related allowance recorded	98,971		98,971		134,195
Impaired Loans, Recorded Investment, With an allowance recorded	14,468		14,468		7,797
Impaired Loans, Unpaid Principal Balance, With an allowance recorded	14,468		14,468		7,797
Impaired Loans, Related Allowance	2,683		2,683		1,592
Impaired Loans, Recorded Investment	113,380		113,380		141,933
Impaired Loans, Unpaid Principal Balance	113,439		113,439		141,992
Impaired Loans, Related Allowance	2,683		2,683		1,592
Impaired Loans, Average Recorded Investment, With no related allowance recorded	99,005	148,753	105,199	121,811
Impaired Loans, Interest Income Recognized, With no related allowance recorded	311	178	928	551
Impaired Loans, Average Recorded Investment, With an allowance recorded	12,465	13,111	11,158	13,492
Impaired Loans, Interest Income Recognized, With an allowance recorded	189	10	251	108
Impaired Loans, Average Recorded Investment	111,470	161,864	116,357	135,303
Impaired Loans, Interest Income Recognized	500	188	1,179	659
Other Commercial [Member]
Financing Receivable, Impaired [Line Items]
Impaired Loans, Recorded Investment, With no related allowance recorded	60,602		60,602		46,993
Impaired Loans, Unpaid Principal Balance, With no related allowance recorded	63,069		63,069		49,552
Impaired Loans, Recorded Investment, With an allowance recorded	50,454		50,454		60,512
Impaired Loans, Unpaid Principal Balance, With an allowance recorded	59,052		59,052		70,396
Impaired Loans, Related Allowance	16,500		16,500		16,721
Impaired Loans, Recorded Investment	111,056		111,056		107,505
Impaired Loans, Unpaid Principal Balance	122,121		122,121		119,948
Impaired Loans, Related Allowance	16,500		16,500		16,721
Impaired Loans, Average Recorded Investment, With no related allowance recorded	56,489	57,302	55,124	57,047
Impaired Loans, Interest Income Recognized, With no related allowance recorded	313	148	1,020	632
Impaired Loans, Average Recorded Investment, With an allowance recorded	47,563	71,886	47,736	71,736
Impaired Loans, Interest Income Recognized, With an allowance recorded	305	42	380	685
Impaired Loans, Average Recorded Investment	104,052	129,188	102,860	128,783
Impaired Loans, Interest Income Recognized	618	190	1,400	1,317
Residential Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired Loans, Recorded Investment, With no related allowance recorded	33,190		33,190		26,751
Impaired Loans, Unpaid Principal Balance, With no related allowance recorded	34,041		34,041		28,202
Impaired Loans, Recorded Investment, With an allowance recorded	17,853		17,853		9,813
Impaired Loans, Unpaid Principal Balance, With an allowance recorded	19,295		19,295		10,418
Impaired Loans, Related Allowance	3,115		3,115		1,552
Impaired Loans, Recorded Investment	51,043		51,043		36,564
Impaired Loans, Unpaid Principal Balance	53,336		53,336		38,620
Impaired Loans, Related Allowance	3,115		3,115		1,552
Impaired Loans, Average Recorded Investment, With no related allowance recorded	28,753	21,772	27,210	21,397
Impaired Loans, Interest Income Recognized, With no related allowance recorded	144	58	501	219
Impaired Loans, Average Recorded Investment, With an allowance recorded	14,975	15,276	13,946	14,904
Impaired Loans, Interest Income Recognized, With an allowance recorded	57	16	247	58
Impaired Loans, Average Recorded Investment	43,728	37,048	41,156	36,301
Impaired Loans, Interest Income Recognized	201	74	748	277
Consumer [Member] | Bankcard [Member]
Financing Receivable, Impaired [Line Items]
Impaired Loans, Recorded Investment, With no related allowance recorded	0		0		0
Impaired Loans, Unpaid Principal Balance, With no related allowance recorded	0		0		0
Impaired Loans, Recorded Investment, With an allowance recorded	0		0		0
Impaired Loans, Unpaid Principal Balance, With an allowance recorded	0		0		0
Impaired Loans, Related Allowance	0		0		0
Impaired Loans, Recorded Investment	0		0		0
Impaired Loans, Unpaid Principal Balance	0		0		0
Impaired Loans, Related Allowance	0		0		0
Impaired Loans, Average Recorded Investment, With an allowance recorded	0	0	0	0
Impaired Loans, Interest Income Recognized, With an allowance recorded	0	0	0	0
Impaired Loans, Average Recorded Investment	0	0	0	0
Impaired Loans, Interest Income Recognized	0	0	0	0
Consumer [Member] | Other Consumer [Member]
Financing Receivable, Impaired [Line Items]
Impaired Loans, Recorded Investment, With no related allowance recorded	23		23		15
Impaired Loans, Unpaid Principal Balance, With no related allowance recorded	23		23		15
Impaired Loans, Recorded Investment, With an allowance recorded	0		0		0
Impaired Loans, Unpaid Principal Balance, With an allowance recorded	0		0		0
Impaired Loans, Related Allowance	0		0		0
Impaired Loans, Recorded Investment	23		23		15
Impaired Loans, Unpaid Principal Balance	23		23		15
Impaired Loans, Related Allowance	0		0		$ 0
Impaired Loans, Average Recorded Investment, With an allowance recorded	0	0	0	0
Impaired Loans, Interest Income Recognized, With an allowance recorded	0	0	0	0
Impaired Loans, Average Recorded Investment	23	25	29	29
Impaired Loans, Interest Income Recognized	$ 0	$ 0	$ 0	$ 0

Allowance for Credit Losses - A

Allowance for Credit Losses - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Financing Receivable, Allowance for Credit Losses [Line Items]
Specific loss allocations are calculated for commercial loans in excess					$ 500,000,000
Number of days for collecting principal or interest on consumer loans					90 days
Minimum collection period for home equity loan or high loan to value loan					180 days
Retail credits amount deemed unrecoverable charged-off period					60 days
Retail credits charged off period after discovery of the fraud					90 days
Reversal of provision for loan losses related to loans acquired		$ 43,000		$ 415,000
provision for loan losses related to loans acquired	$ 924		$ 3,004
Reserve for lending-related commitments	$ 1,144,000		$ 1,144,000		$ 679,000
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	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2018	Dec. 31, 2017
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses Beginning balance	$ 77,135	$ 76,627	$ 72,771
Charge-offs	7,044	20,614	32,863
Recoveries	2,042	4,738	8,313
Provision	4,808	16,190	28,406
Allowance for Loan Losses Ending balance	76,941	76,941	76,627
Allowance for Loan Losses, individually evaluated for impairment	27,353	27,353	22,345
Allowance for Loan Losses, collectively evaluated for impairment	49,588	49,588	54,282
Financing receivables	13,286,711	13,286,711	13,027,337
Financing receivables, individually evaluated for impairment	162,572	162,572	168,524
Financing receivables, collectively evaluated for impairment	12,968,613	12,968,613	12,648,292
Loans Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses	0	0	0
Financing receivables	155,526	155,526	210,521
Construction & Land Development [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses Beginning balance	6,592	7,187	10,606
Charge-offs	110	642	3,337
Recoveries	134	145	726
Provision	480	406	(808)
Allowance for Loan Losses Ending balance	7,096	7,096	7,187
Allowance for Loan Losses, individually evaluated for impairment	2,494	2,494	229
Allowance for Loan Losses, collectively evaluated for impairment	4,602	4,602	6,958
Financing receivables	1,379,985	1,379,985	1,504,907
Financing receivables, individually evaluated for impairment	16,875	16,875	16,921
Financing receivables, collectively evaluated for impairment	1,343,130	1,343,130	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	0
Financing receivables	19,980	19,980	26,780
Allowance for Estimated Imprecision [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses Beginning balance	157	73	347
Charge-offs	0	0	0
Recoveries	0	0	0
Provision	(18)	66	(274)
Allowance for Loan Losses Ending balance	139	139	73
Allowance for Loan Losses, individually evaluated for impairment	0	0	0
Allowance for Loan Losses, collectively evaluated for impairment	139	139	73
Financing receivables	0	0	0
Financing receivables, individually evaluated for impairment	0	0	0
Financing receivables, collectively evaluated for impairment	0	0	0
Allowance for Estimated Imprecision [Member] | Loans Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses	0	0	0
Financing receivables	0	0	0
Commercial Real Estate [Member] | Owner-Occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses Beginning balance	3,213	5,401	5,273
Charge-offs	1,478	3,221	2,246
Recoveries	415	1,160	2,599
Provision	2,391	1,201	(225)
Allowance for Loan Losses Ending balance	4,541	4,541	5,401
Allowance for Loan Losses, individually evaluated for impairment	2,560	2,560	2,251
Allowance for Loan Losses, collectively evaluated for impairment	1,981	1,981	3,150
Financing receivables	1,336,434	1,336,434	1,361,629
Financing receivables, individually evaluated for impairment	29,391	29,391	36,721
Financing receivables, collectively evaluated for impairment	1,284,114	1,284,114	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	0
Financing receivables	22,929	22,929	33,529
Commercial Real Estate [Member] | Nonowner-Occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses Beginning balance	6,183	6,369	6,883
Charge-offs	0	314	296
Recoveries	395	548	244
Provision	22	(3)	(462)
Allowance for Loan Losses Ending balance	6,600	6,600	6,369
Allowance for Loan Losses, individually evaluated for impairment	2,683	2,683	1,592
Allowance for Loan Losses, collectively evaluated for impairment	3,917	3,917	4,777
Financing receivables	4,341,501	4,341,501	4,451,298
Financing receivables, individually evaluated for impairment	22,768	22,768	21,851
Financing receivables, collectively evaluated for impairment	4,250,305	4,250,305	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	0
Financing receivables	68,428	68,428	108,450
Other Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses Beginning balance	48,191	45,189	33,087
Charge-offs	4,432	13,095	21,189
Recoveries	394	1,484	3,395
Provision	291	10,866	29,896
Allowance for Loan Losses Ending balance	44,444	44,444	45,189
Allowance for Loan Losses, individually evaluated for impairment	16,500	16,500	16,721
Allowance for Loan Losses, collectively evaluated for impairment	27,944	27,944	28,468
Financing receivables	1,932,919	1,932,919	1,998,979
Financing receivables, individually evaluated for impairment	73,544	73,544	78,715
Financing receivables, collectively evaluated for impairment	1,830,646	1,830,646	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	0
Financing receivables	28,729	28,729	27,558
Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses Beginning balance	10,380	9,927	13,770
Charge-offs	365	1,357	2,973
Recoveries	558	916	601
Provision	1,067	2,154	(1,471)
Allowance for Loan Losses Ending balance	11,640	11,640	9,927
Allowance for Loan Losses, individually evaluated for impairment	3,116	3,116	1,552
Allowance for Loan Losses, collectively evaluated for impairment	8,524	8,524	8,375
Financing receivables	3,387,268	3,387,268	2,996,171
Financing receivables, individually evaluated for impairment	19,994	19,994	14,316
Financing receivables, collectively evaluated for impairment	3,351,837	3,351,837	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	0
Financing receivables	15,437	15,437	14,189
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses Beginning balance	2,419	2,481	2,805
Charge-offs	659	1,985	2,822
Recoveries	146	485	748
Provision	575	1,500	1,750
Allowance for Loan Losses Ending balance	2,481	2,481	2,481
Allowance for Loan Losses, individually evaluated for impairment	0	0	0
Allowance for Loan Losses, collectively evaluated for impairment	2,481	2,481	2,481
Financing receivables	908,604	908,604	714,353
Financing receivables, individually evaluated for impairment	0	0	0
Financing receivables, collectively evaluated for impairment	908,581	908,581	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	0
Financing receivables	$ 23	$ 23	$ 15

Intangible Assets- Summary of I

Intangible Assets- Summary of Intangible Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Goodwill not subject to amortization	$ 1,478,014	$ 1,478,380
Core Deposit Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	98,359	98,359
Accumulated Amortization	(60,482)	(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	1,472,699	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	(60,482)	(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	9 Months Ended
	Sep. 30, 2018USD ($)
Goodwill [Line Items]
Goodwill, Beginning Balance	$ 1,478,380
Goodwill, Ending Balance	1,478,014
Cardinal Financial Corporation [Member]
Goodwill [Line Items]
Addition to goodwill	(366)
Community Banking [Member]
Goodwill [Line Items]
Goodwill, Beginning Balance	1,473,265
Goodwill, Ending Balance	1,472,699
Community Banking [Member] | Cardinal Financial Corporation [Member]
Goodwill [Line Items]
Addition to goodwill	(566)
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 - Additional

Intangible Assets - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense on intangible assets	$ 2,009	$ 2,240	$ 6,029	$ 5,381

Intangible Assets - Schedule of

Intangible Assets - Schedule of Anticipated Amortization Expense (Detail) $ in Thousands	Sep. 30, 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 ($)	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Short-term Debt [Line Items]
Unused lines of credit	$ 230,000,000
Federal funds purchased	25,790,000	$ 16,235,000
Repurchase agreements	153,718,000
Unrelated Financial Institution [Member]
Short-term Debt [Line Items]
Unused lines of credit	$ 20,000,000
Renewal period of line of credit	360 days
Amount of outstanding balance under line of credit	$ 0

Long-Term Borrowings - Addition

Long-Term Borrowings - Additional Information (Detail)	9 Months Ended	12 Months Ended
	Sep. 30, 2018USD ($)Trust	Dec. 31, 2017USD ($)
Debt Instrument [Line Items]
Unused borrowing amount	$ 3,986,778,000
FHLB advances	$ 1,284,781,000	$ 1,271,531,000
FHLB advances, weighted-average interest rate	2.13%
FHLB advances, maximum maturity period	7 years
Number of statutory business trusts | Trust	14
Outstanding balances of debentures	$ 234,590,000	$ 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	Sep. 30, 2018USD ($)
Debt Disclosure [Abstract]
2,018	$ 970,890
2,019	187,224
2,020	41,779
2,021	52,667
2022 and thereafter	32,221
Total	$ 1,284,781

Commitments and Contingent Li_2

Commitments and Contingent Liabilities - Additional Information (Detail) - USD ($)	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Loss Contingencies [Line Items]
Loan commitments outstanding	$ 3,861,482,000	$ 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	433,931,000
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	$ 132,735,000	$ 147,017,000

Derivative Financial Instrume_3

Derivative Financial Instruments - Schedule of Notional Amount and Fair Value Derivative Financial Instruments (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Derivative [Line Items]
Asset derivatives, notional amount	$ 445,224	$ 251,721
Asset derivatives designated as hedging instruments	4,042	538
Liability derivatives, notional amount	22,521	255,295
Asset derivatives not designated as hedging instruments	5,152	4,561
Total asset derivatives	9,194	5,099
Liability derivatives designated as hedging instruments	0	165
Liability derivatives not designated as hedging instruments	197	312
Total liability derivatives	197	477
Designated as Hedging Instrument [Member]
Derivative [Line Items]
Asset derivatives, notional amount	86,655	71,831
Liability derivatives, notional amount	0	18,795
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Asset derivatives, notional amount	358,569	179,890
Liability derivatives, notional amount	22,521	236,500
Other Assets [Member] | TBA Mortgage Backed Securities [Member]
Derivative [Line Items]
Asset derivatives not designated as hedging instruments	1,161	0
Other Assets [Member] | Interest Rate Lock Commitments [Member]
Derivative [Line Items]
Asset derivatives not designated as hedging instruments	3,991	4,559
Other Assets [Member] | Not Designated as Hedging Instrument [Member] | TBA Mortgage Backed Securities [Member]
Derivative [Line Items]
Asset derivatives, notional amount	223,500	0
Other Assets [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Lock Commitments [Member]
Derivative [Line Items]
Asset derivatives, notional amount	135,069	148,866
Other Liabilities [Member] | TBA Mortgage Backed Securities [Member]
Derivative [Line Items]
Liability derivatives not designated as hedging instruments	0	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	0	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	4,042	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	86,655	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	0	2
Forward Loan Sale Commitments [Member] | Other Assets [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Asset derivatives, notional amount	0	31,024
Forward Loan Sale Commitments [Member] | Other Liabilities [Member]
Derivative [Line Items]
Liability derivatives not designated as hedging instruments	197	0
Forward Loan Sale Commitments [Member] | Other Liabilities [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Liability derivatives, notional amount	$ 22,521	$ 0

Derivative Financial Instrume_4

Derivative Financial Instruments - Schedule of Derivative Financial Instruments on Statements of Income (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Derivative [Line Items]
Derivatives in hedging relationships	$ (900)	$ (4,826)	$ (224)	$ (1,633)
Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivatives in hedging relationships	24	208	42	648
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	24	208	42	648
Designated as Hedging Instrument [Member] | Other Income [Member] | Forward Loan Sale Commitments [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Derivatives in hedging relationships			0	0
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivatives not designated as hedging instruments	(876)	(4,618)	(182)	(985)
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	2,583	123	(1,473)	(2,907)
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	(3,262)	(4,484)	1,643	3,465
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	$ (197)	$ (257)	$ (12)	$ (427)

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($)	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017
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		0.12%
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		0.49%
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		0.28%
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	0.12%
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	0.49%
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	0.28%

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Financial Assets and Liabilities Measured at Fair Value (Detail) - USD ($) $ in Thousands	Sep. 30, 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	2,178,567	1,888,756
Loans held for sale	234,196	265,955
Derivative financial assets	9,194	5,099
Derivative financial liabilities	197	477
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	101,565	114,758
State and Political Subdivisions [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	252,246	303,869
Residential Mortgage-Backed Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	943,647	814,593
Commercial Mortgage-Backed Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	543,652	454,857
Asset-Backed Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	223,602	109,970
Trust Preferred Collateralized Debt Obligations [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	6,154	34,269
Single Issue Trust Preferred Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	8,104	12,560
Corporate Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	95,025	28,490
Marketable Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities		9,878
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	2,178,567	1,888,756
Loans held for sale	231,310	263,308
Derivative financial assets	9,194	5,099
Derivative financial liabilities	197	477
Available for sale debt securities		1,878,878
Fair Value, Measurements, Recurring [Member] | 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	101,565
Available for sale debt securities		114,758
Fair Value, Measurements, Recurring [Member] | State and Political Subdivisions [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	252,246
Available for sale debt securities		303,869
Fair Value, Measurements, Recurring [Member] | Residential Mortgage-Backed Securities [Member] | Agency [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	943,647
Available for sale debt securities		814,593
Fair Value, Measurements, Recurring [Member] | Residential Mortgage-Backed Securities [Member] | Non-Agency [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	4,572
Available for sale debt securities		5,512
Fair Value, Measurements, Recurring [Member] | Commercial Mortgage-Backed Securities [Member] | Agency [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	543,652
Available for sale debt securities		454,857
Fair Value, Measurements, Recurring [Member] | Asset-Backed Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	223,602
Available for sale debt securities		109,970
Fair Value, Measurements, Recurring [Member] | Trust Preferred Collateralized Debt Obligations [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	6,154
Available for sale debt securities		34,269
Fair Value, Measurements, Recurring [Member] | Single Issue Trust Preferred Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	8,104
Available for sale debt securities		12,560
Fair Value, Measurements, Recurring [Member] | Corporate Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	95,025
Available for sale debt securities		28,490
Fair Value, Measurements, Recurring [Member] | Financial Services Industry [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale equity securities		3,545
Equity securities	173
Fair Value, Measurements, Recurring [Member] | Other Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale equity securities		1
Equity securities	4,599
Fair Value, Measurements, Recurring [Member] | Marketable Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities	9,845
Fair Value, Measurements, Recurring [Member] | Interest Rate Lock Commitments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative financial assets	3,991	4,561
Fair Value, Measurements, Recurring [Member] | TBA Mortgage Backed Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative financial assets	1,161
Derivative financial liabilities		312
Interest Rate Swap Contracts [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative financial assets	4,042	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	0
Derivative financial liabilities	197
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	5,073
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	6,879	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] | Marketable Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities	9,845
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	6,879	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] | 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	0
Available for sale debt securities		0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fair Value, Measurements, Recurring [Member] | State and Political Subdivisions [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] | Fair Value, Measurements, Recurring [Member] | Residential Mortgage-Backed Securities [Member] | Agency [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] | Fair Value, Measurements, Recurring [Member] | Residential Mortgage-Backed Securities [Member] | Non-Agency [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] | Fair Value, Measurements, Recurring [Member] | Commercial Mortgage-Backed Securities [Member] | Agency [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] | Fair Value, Measurements, Recurring [Member] | Asset-Backed Securities [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] | Fair Value, Measurements, Recurring [Member] | Trust Preferred Collateralized Debt Obligations [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] | Fair Value, Measurements, Recurring [Member] | Single Issue Trust Preferred Securities [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] | Fair Value, Measurements, Recurring [Member] | Corporate Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	6,879
Available for sale debt securities		0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fair Value, Measurements, Recurring [Member] | Financial Services Industry [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale equity securities		331
Equity securities	173
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fair Value, Measurements, Recurring [Member] | Other Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale equity securities		1
Equity securities	4,599
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fair Value, Measurements, Recurring [Member] | Marketable Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities	9,845
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 assets	0
Derivative financial liabilities		0
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
Derivative financial liabilities	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	5,073
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	2,165,534	1,847,823
Loans held for sale	2,886	2,647
Derivative financial assets	5,203	540
Derivative financial liabilities	197	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 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	2,165,534	1,847,823
Loans held for sale	0	0
Derivative financial assets	5,203	540
Derivative financial liabilities	197	477
Available for sale debt securities		1,844,609
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member] | 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	101,565
Available for sale debt securities		114,758
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member] | State and Political Subdivisions [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	252,246
Available for sale debt securities		303,869
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member] | Residential Mortgage-Backed Securities [Member] | Agency [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	943,647
Available for sale debt securities		814,593
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member] | Residential Mortgage-Backed Securities [Member] | Non-Agency [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	4,572
Available for sale debt securities		5,512
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member] | Commercial Mortgage-Backed Securities [Member] | Agency [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	543,652
Available for sale debt securities		454,857
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member] | Asset-Backed Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	223,602
Available for sale debt securities		109,970
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member] | Trust Preferred Collateralized Debt Obligations [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] | Fair Value, Measurements, Recurring [Member] | Single Issue Trust Preferred Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	8,104
Available for sale debt securities		12,560
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	88,146
Available for sale debt securities		28,490
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member] | Financial Services Industry [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] | Fair Value, Measurements, Recurring [Member] | Other Equity Securities [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] | Fair Value, Measurements, Recurring [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] | 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 assets	1,161
Derivative financial liabilities		312
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	4,042	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	0
Derivative financial liabilities	197
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	6,154	34,269
Loans held for sale	231,310	263,308
Derivative financial assets	3,991	4,559
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
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	6,154	34,269
Loans held for sale	231,310	263,308
Derivative financial assets	3,991	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] | 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	0
Available for sale debt securities		0
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member] | State and Political Subdivisions [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] | Fair Value, Measurements, Recurring [Member] | Residential Mortgage-Backed Securities [Member] | Agency [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] | Fair Value, Measurements, Recurring [Member] | Residential Mortgage-Backed Securities [Member] | Non-Agency [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] | Fair Value, Measurements, Recurring [Member] | Commercial Mortgage-Backed Securities [Member] | Agency [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] | Fair Value, Measurements, Recurring [Member] | Asset-Backed Securities [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] | Fair Value, Measurements, Recurring [Member] | Trust Preferred Collateralized Debt Obligations [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	6,154
Available for sale debt securities		34,269
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member] | Single Issue Trust Preferred Securities [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] | Fair Value, Measurements, Recurring [Member] | Corporate Bonds [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] | Fair Value, Measurements, Recurring [Member] | Financial Services Industry [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, Measurements, Recurring [Member] | Other Equity Securities [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, Measurements, Recurring [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, Measurements, Recurring [Member] | Interest Rate Lock Commitments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative financial assets	3,991	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 assets	0
Derivative financial liabilities		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
Derivative financial liabilities	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 - Sch_2

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	9 Months Ended	12 Months Ended
	Sep. 30, 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	1,157	8,757
Purchases, issuances, and settlements	0	0
Sales	(29,300)	(8,049)
Transfers in and/or out of Level 3	0	0
Balance, end of period	6,154	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)	(54,829)	(58,132)
Acquired in Cardinal merger	0	271,301
Originations	2,089,366	2,333,927
Sales	(2,148,777)	(2,408,945)
Transfers in and/or out of Level 3	(27,416)	8,893
Balance, end of period	231,310	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	(568)	(5,834)
Balance, end of period	3,991	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 - Sch_3

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		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Mortgage Banking [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Income from mortgage banking activities	$ (5,929)	$ (5,090)	$ (2,838)	$ (7,529)

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	Sep. 30, 2018	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Loans held for sale, unpaid principal balance	$ 227,943	$ 257,674
Loans held for sale, fair value	231,310	263,308
Loans held for sale, fair value over/(under) unpaid principal balance	$ 3,367	$ 5,634

Fair Value Measurements - Sum_2

Fair Value Measurements - Summary of Financial Assets Measured at Fair Value on Nonrecurring Basis (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held for sale	$ 0	$ 14
YTD Losses, Impaired Loans	4,177	12,291
YTD Losses, OREO	796	4,200
Loans held for sale	231,310	263,308
OREO	18,786	24,348
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held for sale	2,886	2,647
Impaired Loans	109,582	88,637
OREO	18,786	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	2,886	2,647
Impaired Loans	98,171	70,950
OREO	18,786	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	11,411	17,687
OREO	$ 0	$ 197

Fair Value Measurements - Sum_3

Fair Value Measurements - Summary of Estimated Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 1,254,686	$ 1,666,167	$ 1,747,037	$ 1,434,527
Securities available for sale	2,178,567	1,888,756
Securities held to maturity	20,351	20,428
Other securities	166,749	162,461
Loans held for sale	234,196	265,955
Loans	13,276,740	13,011,421
Derivative financial assets	9,194	5,099
Deposits	14,091,172	13,830,591
Derivative financial liabilities	197	477
Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	1,254,686	1,666,167
Securities available for sale	2,178,567	1,888,756
Securities held to maturity	20,351	20,428
Other securities	166,749	162,461
Loans held for sale	234,196	265,955
Loans	13,199,799	12,934,794
Derivative financial assets	9,194	5,099
Deposits	14,091,172	13,830,591
Short-term borrowings	379,508	477,587
Long-term borrowings	1,319,371	1,363,977
Derivative financial liabilities	197	477
Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	1,254,686	1,666,167
Securities available for sale	2,178,567	1,888,756
Securities held to maturity	19,619	20,018
Other securities	166,749	154,338
Loans held for sale	234,196	265,955
Loans	12,488,175	12,437,797
Derivative financial assets	9,194	5,099
Deposits	14,052,668	14,024,720
Short-term borrowings	379,508	477,587
Long-term borrowings	1,293,611	1,338,754
Derivative financial liabilities	197	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	9,845
Marketable Equity Securities [Member] | Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities	9,845
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	6,879	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	9,845
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	1,254,686	1,666,167
Securities available for sale	2,165,534	1,847,823
Securities held to maturity	16,599	16,998
Other securities	0	0
Loans held for sale	2,886	2,647
Loans	0	0
Derivative financial assets	5,203	540
Deposits	14,052,668	14,024,720
Short-term borrowings	379,508	477,587
Long-term borrowings	1,293,611	1,338,754
Derivative financial liabilities	197	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	6,154	34,269
Securities held to maturity	3,020	3,020
Other securities	166,749	154,338
Loans held for sale	231,310	263,308
Loans	12,488,175	12,437,797
Derivative financial assets	3,991	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	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 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
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		$ 1,024	$ 909	$ 3,016	$ 2,589
Number of share available for grant for prior plans		0		0
Maximum term for awards granted (years)				10 years
Shares issued related stock option exercises				60,161	163,562
Total intrinsic value of options exercised				$ 851	$ 3,078
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	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Disclosure Stock Based Compensation Stock Option Plan [Abstract]
Shares, Outstanding, Beginning balance	1,558,438
Shares, Granted	276,192
Shares, Exercised	(60,161)	(163,562)
Shares, Forfeited or expired	(24,007)
Shares, Outstanding, Ending balance	1,750,462
Shares, Exercisable at September 30, 2018	1,169,402
Aggregate Intrinsic Value, Outstanding at September 30, 2018	$ 9,624,912
Aggregate Intrinsic Value, Exercisable at September 30, 2018	$ 9,508,502
Weighted Average Remaining Contractual Term, Outstanding at September 30, 2018	5 years 9 months 18 days
Weighted Average Remaining Contractual Term, Exercisable at September 30, 2018	4 years 4 months 24 days
Weighted Average Exercise Price, Outstanding, Beginning balance	$ 31.09
Weighted Average Exercise Price, Granted	37.60
Weighted Average Exercise Price, Exercised	23.03
Weighted Average Exercise Price, Forfeited or expired	32.66
Weighted Average Exercise Price, Outstanding, Ending balance	32.36
Weighted Average Exercise Price, Exercisable	$ 28.78

Stock Based Compensation - Stat

Stock Based Compensation - Status of United's Nonvested Stock Option Awards (Detail)	9 Months Ended
	Sep. 30, 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	(187,815)
Shares, Forfeited or expired | shares	(15,188)
Shares, Nonvested, Ending balance | shares	581,060
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	7.53
Weighted-Average Grant Date Fair Value Per Share, Forfeited or expired | $ / shares	7.67
Weighted-Average Grant Date Fair Value Per Share, Nonvested Ending balance | $ / shares	$ 7.86

Stock Based Compensation - Chan

Stock Based Compensation - Changes to United's Restricted Common Shares (Detail) - Restricted Stock [Member]	9 Months Ended
	Sep. 30, 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	(62,411)
Shares, Forfeited | shares	(4,253)
Number of Shares, Outstanding, Ending balance | shares	200,836
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	38.42
Weighted-Average Grant Date Fair Value Per Share, Outstanding, Ending balance | $ / shares	$ 39.67

Employee Benefit Plans - Additi

Employee Benefit Plans - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Mar. 31, 2018	Sep. 30, 2018
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		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 673	$ 574	$ 1,997	$ 1,705
Interest cost	1,324	1,293	3,927	3,837
Expected return on plan assets	(2,578)	(2,072)	(7,651)	(6,148)
Recognized net actuarial loss	1,174	1,111	3,485	3,298
Net periodic pension (benefit) cost	$ 593	$ 906	$ 1,758	$ 2,692
Weighted-Average Assumptions:
Discount rate	3.83%	4.49%	3.83%	4.49%
Expected return on assets	7.00%	7.00%	7.00%	7.00%
Rate of compensation increase	3.00%	3.00%	3.00%	3.00%
Prior to Age 45 [Member]
Weighted-Average Assumptions:
Rate of compensation increase	3.50%	3.50%	3.50%	3.50%

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Accrued interest related to uncertain tax positions	$ 649		$ 548	$ 649	$ 548
Federal corporate tax rate				21.00%		35.00%
Deferred tax expense due to the Tax Act		$ 37,732
Effective tax rate	21.77%		32.91%	22.25%	33.68%

Comprehensive Income - Componen

Comprehensive Income - Components of Total Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Net income	$ 64,412	$ 56,738	$ 192,392	$ 132,606
AFS securities with OTTI charges during the period	0	0	0	(60)
Related income tax effect	0	0	0	22
Less: OTTI charges recognized in net income	0	0	0	60
Related income tax benefit	0	0	0	(22)
Reclassification of previous noncredit OTTI to credit OTTI	0	0	0	0
Related income tax benefit	0	0	0	0
Net unrealized (losses) gains on AFS securities with OTTI	0	0	0	0
Change in net unrealized gain on AFS securities arising during the period	(9,995)	3,584	(42,696)	14,846
Related income tax effect	2,329	(1,326)	11,621	(5,493)
Net reclassification adjustment for (gains) losses included in net income	114	(467)	290	(1,444)
Related income tax expense (benefit)	(27)	173	(68)	534
Total AFS securities - all other	(7,579)	1,964	(30,853)	8,443
Net effect of AFS securities on other comprehensive income	(7,579)	1,964	(30,853)	8,443
Accretion on the unrealized loss for securities transferred from AFS to the HTM investment portfolio prior to call or maturity	2	2	6	6
Related income tax expense	0	0	(2)	(2)
Net effect of HTM securities on other comprehensive income	2	2	4	4
Pension plan:
Recognized net actuarial loss	1,174	1,111	3,485	3,298
Related income tax benefit	(256)	(394)	(782)	(1,191)
Net effect of change in pension plan asset on other comprehensive income	918	717	2,703	2,107
Net current-period other comprehensive income, net of tax	(6,659)	2,683	(28,146)	10,554
Comprehensive income, net of tax	$ 57,753	$ 59,421	$ 164,246	$ 143,160

Comprehensive Income - Compon_2

Comprehensive Income - Components of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			$ 3,240,530
Cumulative effect of adopting Accounting Standard Update 2016-01	$ 0		0
Reclass due to adopting Accounting Standard Update 2018-02	0		0
Net current-period other comprehensive income, net of tax	(6,659)	$ 2,683	(28,146)	$ 10,554
Ending Balance	3,251,128		3,251,128
Pension Plan [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			(35,775)
Cumulative effect of adopting Accounting Standard Update 2016-01	0		0
Reclass due to adopting Accounting Standard Update 2018-02	(4,721)		(4,721)
Other comprehensive income before reclassification			0
Amounts reclassified from accumulated other comprehensive income			2,703
Net current-period other comprehensive income, net of tax			2,703
Ending Balance	(37,793)		(37,793)
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)		(136)
Reclass due to adopting Accounting Standard Update 2018-02	(1,632)		(1,632)
Other comprehensive income before reclassification			(31,075)
Amounts reclassified from accumulated other comprehensive income			222
Net current-period other comprehensive income, net of tax			(30,853)
Ending Balance	(38,825)		(38,825)
Accumulated Unrealized Loss On Securities Available For Sale Transferred To Held To Maturity [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			(46)
Cumulative effect of adopting Accounting Standard Update 2016-01	0		0
Reclass due to adopting Accounting Standard Update 2018-02	0		0
Other comprehensive income before reclassification			4
Amounts reclassified from accumulated other comprehensive income			0
Net current-period other comprehensive income, net of tax			4
Ending Balance	(42)		(42)
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)		(136)
Reclass due to adopting Accounting Standard Update 2018-02	(6,353)		(6,353)
Other comprehensive income before reclassification			(31,071)
Amounts reclassified from accumulated other comprehensive income			2,925
Net current-period other comprehensive income, net of tax			(28,146)
Ending Balance	$ (76,660)		$ (76,660)

Comprehensive Income - Reclassi

Comprehensive Income - Reclassifications Out of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Available for sale ("AFS") securities:
Income before income taxes	$ 82,338	$ 84,574	$ 247,458	$ 199,962
Related income tax effect	(17,926)	(27,836)	(55,066)	(67,356)
Net income	64,412	56,738	192,392	132,606
Pension plan:
Income before income taxes	82,338	84,574	247,458	199,962
Related income tax effect	(17,926)	(27,836)	(55,066)	(67,356)
Net income	$ 64,412	$ 56,738	192,392	$ 132,606
Reclassification out of Accumulated Other Comprehensive Income [Member]
Available for sale ("AFS") securities:
Net income			2,925
Pension plan:
Net income			2,925
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			290
Income before income taxes			290
Related income tax effect			(68)
Net income			222
Pension plan:
Income before income taxes			290
Related income tax effect			(68)
Net income			222
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
Available for sale ("AFS") securities:
Income before income taxes			3,485
Related income tax effect			(782)
Net income			2,703
Pension plan:
Recognized net actuarial loss			3,485
Income before income taxes			3,485
Related income tax effect			(782)
Net income			$ 2,703

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		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Distributed earnings allocated to common stock	$ 35,234	$ 34,587	$ 106,429	$ 95,871
Undistributed earnings allocated to common stock	29,060	22,065	85,617	36,518
Net earnings allocated to common shareholders	$ 64,294	$ 56,652	$ 192,046	$ 132,389
Average common shares outstanding	103,617,590	104,760,153	104,382,094	95,040,664
Equivalents from stock options	316,369	307,969	297,782	409,962
Average diluted shares outstanding	103,933,959	105,068,122	104,679,876	95,450,626
Earnings per basic common share	$ 0.62	$ 0.54	$ 1.84	$ 1.39
Earnings per diluted common share	$ 0.62	$ 0.54	$ 1.83	$ 1.39

Variable Interest Entities - Ad

Variable Interest Entities - Additional Information (Detail)	9 Months Ended
	Sep. 30, 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	9 Months Ended
	Sep. 30, 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	Sep. 30, 2018	Dec. 31, 2017
Variable Interest Entity [Line Items]
Aggregate Assets	$ 257,873	$ 266,669
Aggregate Liabilities	248,921	257,674
Risk Of Loss	$ 8,952	$ 8,995

Segment Information - Additiona

Segment Information - Additional Information (Detail)	9 Months Ended
	Sep. 30, 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		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Net interest income	$ 148,775	$ 150,276	$ 441,940	$ 394,141
Provision for loans losses	4,808	7,279	16,190	21,429
Other income	31,686	38,229	98,885	98,881
Other expense	93,315	96,652	277,177	271,631
Income taxes	17,926	27,836	55,066	67,356
Net income	64,412	56,738	192,392	132,606
Total assets (liabilities)	19,187,643	19,129,978	19,187,643	19,129,978
Average assets (liabilities)	19,047,689	18,927,785	18,769,934	17,187,644
Operating Segments [Member] | Community Banking [Member]
Segment Reporting Information [Line Items]
Net interest income	149,770	152,886	444,840	401,044
Provision for loans losses	4,808	7,279	16,190	21,429
Other income	18,717	18,373	53,952	53,409
Other expense	75,255	74,553	224,240	215,935
Income taxes	19,296	29,490	57,519	73,214
Net income	69,128	59,937	200,843	143,875
Total assets (liabilities)	19,080,734	19,083,318	19,080,734	19,083,318
Average assets (liabilities)	18,982,530	18,889,710	18,718,295	17,180,219
Operating Segments [Member] | Mortgage Banking [Member]
Segment Reporting Information [Line Items]
Net interest income	388	(36)	1,028	54
Provision for loans losses	0	0	0	0
Other income	16,478	19,936	54,829	42,329
Other expense	17,957	24,036	57,566	42,744
Income taxes	(246)	(1,332)	(385)	(39)
Net income	(845)	(2,804)	(1,324)	(322)
Total assets (liabilities)	288,638	350,483	288,638	350,483
Average assets (liabilities)	303,556	321,744	284,100	187,118
Other [Member]
Segment Reporting Information [Line Items]
Net interest income	(3,168)	(2,574)	(8,794)	(6,957)
Provision for loans losses	0	0	0	0
Other income	58	(80)	(696)	3,143
Other expense	1,885	(1,937)	(295)	12,952
Income taxes	(1,124)	(322)	(2,068)	(5,819)
Net income	(3,871)	(395)	(7,127)	(10,947)
Total assets (liabilities)	12,545	(900)	12,545	(900)
Average assets (liabilities)	5,468	(13,994)	8,043	(20,402)
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Net interest income	1,785	0	4,866	0
Provision for loans losses	0	0	0	0
Other income	(3,567)	0	(9,200)	0
Other expense	(1,782)	0	(4,334)	0
Income taxes	0	0	0	0
Net income	0	0	0	0
Total assets (liabilities)	(194,274)	(302,923)	(194,274)	(302,923)
Average assets (liabilities)	$ (243,867)	$ (269,675)	$ (240,505)	$ (159,291)