United Bankshares (UBSI) 10-Q 9 Nov 17 2017 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2017	Oct. 31, 2017
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2017
Document Fiscal Year Focus	2,017
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
Entity Common Stock, Shares Outstanding		104,992,423

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Assets
Cash and due from banks	$ 212,692	$ 175,468
Interest-bearing deposits with other banks	1,533,558	1,258,334
Federal funds sold	787	725
Total cash and cash equivalents	1,747,037	1,434,527
Securities available for sale at estimated fair value (amortized cost-$1,654,657 at September 30, 2017 and $1,277,639 at December 31, 2016)	1,649,634	1,259,214
Securities held to maturity (estimated fair value-$19,909 at September 30, 2017 and $31,178 at December 31, 2016)	20,335	33,258
Other investment securities	166,756	111,166
Loans held for sale (at fair value-$311,186 at September 30, 2017 and $0 at December 31, 2016)	315,031	8,445
Loans	13,156,854	10,356,719
Less: Unearned income	(16,386)	(15,582)
Loans net of unearned income	13,140,468	10,341,137
Less: Allowance for loan losses	(74,926)	(72,771)
Net loans	13,065,542	10,268,366
Bank premises and equipment	104,311	75,909
Goodwill	1,487,607	863,767
Accrued interest receivable	51,607	39,400
Other assets	522,118	414,840
TOTAL ASSETS	19,129,978	14,508,892
Deposits:
Noninterest-bearing	4,134,019	3,171,841
Interest-bearing	9,741,278	7,625,026
Total deposits	13,875,297	10,796,867
Borrowings:
Federal funds purchased	25,800	22,235
Securities sold under agreements to repurchase	316,236	237,316
Federal Home Loan Bank borrowings	1,272,115	897,707
Other long-term borrowings	242,131	224,319
Reserve for lending-related commitments	804	1,044
Accrued expenses and other liabilities	133,752	93,657
TOTAL LIABILITIES	15,866,135	12,273,145
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-105,011,878 and 81,068,252 at September 30, 2017 and December 31, 2016, respectively, including 28,752 and 28,278 shares in treasury at September 30, 2017 and December 31, 2016, respectively	262,530	202,671
Surplus	2,126,914	1,205,778
Retained earnings	909,556	872,990
Accumulated other comprehensive loss	(34,163)	(44,717)
Treasury stock, at cost	(994)	(975)
TOTAL SHAREHOLDERS' EQUITY	3,263,843	2,235,747
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY	$ 19,129,978	$ 14,508,892

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Securities available for sale, amortized cost	$ 1,654,657	$ 1,277,639
Securities held to maturity	19,909	31,178
Loans held for sale at fair value	$ 311,186	$ 0
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	105,011,878	81,068,252
Common stock, shares in treasury	28,752	28,278

Consolidated Statements of Inco

Consolidated Statements of Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Interest income
Interest and fees on loans	$ 155,819	$ 112,273	$ 405,660	$ 314,936
Interest on federal funds sold and other short-term investments	4,874	1,107	11,345	2,371
Interest and dividends on securities:
Taxable	9,406	8,764	26,226	24,728
Tax-exempt	1,484	993	4,057	2,685
Total interest income	171,583	123,137	447,288	344,720
Interest expense
Interest on deposits	14,227	7,723	35,281	21,278
Interest on short-term borrowings	430	553	1,149	1,132
Interest on long-term borrowings	6,650	3,792	16,717	10,232
Total interest expense	21,307	12,068	53,147	32,642
Net interest income	150,276	111,069	394,141	312,078
Provision for loan losses	7,279	6,988	21,429	18,690
Net interest income after provision for loan losses	142,997	104,081	372,712	293,388
Other income
Fees from trust and brokerage services	5,052	4,891	14,683	14,552
Fees from deposit services	8,744	8,306	24,978	24,669
Bankcard fees and merchant discounts	1,332	1,551	3,432	3,754
Other service charges, commissions, and fees	535	500	1,533	1,725
Income from bank-owned life insurance	1,403	2,541	3,878	4,913
Income from mortgage banking activities	20,385	982	43,597	2,499
Other income	311	249	1,626	1,050
Total other-than-temporary impairment losses	0	0	(60)	339
Portion of loss recognized in other comprehensive income	0	0	0	(372)
Net other-than-temporary impairment losses	0	0	(60)	(33)
Net gains on sales/calls of investment securities	467	1	5,214	251
Net investment securities gains	467	1	5,154	218
Total other income	38,229	19,021	98,881	53,380
Other expense
Employee compensation	44,308	24,213	123,240	69,123
Employee benefits	9,578	7,483	27,372	21,380
Net occupancy expense	9,364	6,919	30,061	20,945
Other real estate owned (OREO) expense	2,713	1,342	4,651	4,654
Equipment expense	3,057	2,097	7,493	6,162
Data processing expense	5,597	3,857	14,971	11,004
Bankcard processing expense	449	480	1,356	1,283
FDIC insurance expense	1,540	2,086	5,062	6,341
Other expense	20,046	14,300	57,425	44,796
Total other expense	96,652	62,777	271,631	185,688
Income before income taxes	84,574	60,325	199,962	161,080
Income taxes	27,836	18,846	67,356	53,103
Net income	$ 56,738	$ 41,479	$ 132,606	$ 107,977
Earnings per common share:
Basic	$ 0.54	$ 0.54	$ 1.39	$ 1.49
Diluted	0.54	0.54	1.39	1.48
Dividends per common share	$ 0.33	$ 0.33	$ 0.99	$ 0.99
Average outstanding shares:
Basic	104,760,153	76,218,573	95,040,664	72,413,246
Diluted	105,068,122	76,647,773	95,450,626	72,746,363

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 56,738	$ 41,479	$ 132,606	$ 107,977
Change in net unrealized gain (loss) on available-for-sale (AFS) securities, net of tax	1,964	(4,865)	8,443	7,944
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	717	777	2,107	2,235
Comprehensive income, net of tax	$ 59,421	$ 37,393	$ 143,160	$ 118,160

Consolidated Statement of Chang

Consolidated Statement of Changes in Shareholders' Equity (Unaudited) - 9 months ended Sep. 30, 2017 - USD ($) $ in Thousands	Total	Cardinal Financial Corporation [Member]	Deferred Compensation Plan [Member]	Common Stock [Member]	Common Stock [Member]Cardinal Financial Corporation [Member]	Common Stock [Member]Deferred Compensation Plan [Member]	Surplus [Member]	Surplus [Member]Cardinal Financial Corporation [Member]	Surplus [Member]Deferred Compensation Plan [Member]	Retained Earnings [Member]	Retained Earnings [Member]Cardinal Financial Corporation [Member]	Retained Earnings [Member]Deferred Compensation Plan [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Other Comprehensive Income (Loss) [Member]Cardinal Financial Corporation [Member]	Accumulated Other Comprehensive Income (Loss) [Member]Deferred Compensation Plan [Member]	Treasury Stock [Member]	Treasury Stock [Member]Cardinal Financial Corporation [Member]	Treasury Stock [Member]Deferred Compensation Plan [Member]
Balance at January 1, 2017 at Dec. 31, 2016	$ 2,235,747			$ 202,671			$ 1,205,778			$ 872,990			$ (44,717)			$ (975)
Beginning Balance, shares at Dec. 31, 2016				81,068,252
Comprehensive income:
Net income	132,606			$ 0			0			132,606			0			0
Other comprehensive income, net of tax:	10,554			0			0			0			10,554			0
Total comprehensive income, net of tax	143,160
Stock based compensation expense	2,589			0			2,589			0			0			0
Acquisition, Values		$ 975,254			$ 59,226			$ 916,028			$ 0			$ 0			$ 0
Acquisition, Shares					23,690,589
Purchase of treasury stock	(1)			0			0			0			0			(1)
Distribution of treasury stock for deferred compensation plan			$ 1			$ 0			$ 0			$ 0			$ 0			$ 1
Cash dividends	(96,040)						0			(96,040)			0			0
Grant of restricted stock	0			$ 224			(224)			0			0			0
Grant of restricted stock, shares				89,475
Forfeiture of restricted stock	0			$ 0			19			0			0			(19)
Common stock options exercised	$ 3,133			$ 409			2,724			0			0			0
Common stock options exercised, shares	163,562			163,562
Balance at September 30, 2017 at Sep. 30, 2017	$ 3,263,843			$ 262,530			$ 2,126,914			$ 909,556			$ (34,163)			$ (994)
Ending Balance, shares at Sep. 30, 2017				105,011,878,000

Consolidated Statement of Chan7

Consolidated Statement of Changes in Shareholders' Equity (Unaudited) (Parenthetical)	9 Months Ended
	Sep. 30, 2017$ / sharesshares
Cash dividends per share | $ / shares	$ 0.99
Common stock options exercised, shares	163,562
Common Stock [Member]
Purchase of treasury stock, shares	82
Grant of restricted stock, shares	89,475
Forfeiture of restricted stock, shares	420
Common stock options exercised, shares	163,562
Deferred Compensation Plan [Member] | Common Stock [Member]
Distribution of treasury stock for deferred compensation plan, shares	28
Cardinal Financial Corporation [Member] | Common Stock [Member]
Acquisition, Shares	23,690,589

Condensed Consolidated Statemen

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Statement of Cash Flows [Abstract]
NET CASH PROVIDED BY OPERATING ACTIVITIES	$ 125,151	$ 125,948
INVESTING ACTIVITIES
Proceeds from maturities and calls of securities held to maturity	12,929	5,039
Proceeds from sales of securities available for sale	245,065	103,411
Proceeds from maturities and calls of securities available for sale	386,496	264,834
Purchases of securities available for sale	(630,061)	(385,030)
Purchases of bank premises and equipment	(11,115)	(4,150)
Proceeds from sales of bank premises and equipment	13	229
Purchases of other investment securities	(51,941)	(61,193)
Proceeds from sales and redemptions of other investment securities	14,393	47,285
Proceeds from the sales of OREO properties	4,908	15,435
Acquisition of subsidiaries, net of cash paid	44,531	29,330
Net change in loans	369,233	(111,723)
NET CASH PROVIDED BY (USED IN) INVESTING ACTIVITIES	384,451	(96,533)
FINANCING ACTIVITIES
Cash dividends paid	(86,709)	(71,129)
Acquisition of treasury stock	(1)	(1)
Proceeds from exercise of stock options	3,296	4,668
Repayment of long-term Federal Home Loan Bank borrowings	(845,207)	(725,077)
Proceeds from issuance of long-term Federal Home Loan Bank borrowings	815,000	795,000
Distribution of treasury stock for deferred compensation plan	1	1
Changes in:
Deposits	(269,742)	265,183
Federal funds purchased, securities sold under agreements to repurchase and other short-term borrowings	186,270	(36,889)
NET CASH (USED IN) PROVIDED BY FINANCING ACTIVITIES	(197,092)	231,756
Increase in cash and cash equivalents	312,510	261,171
Cash and cash equivalents at beginning of year	1,434,527	857,335
Cash and cash equivalents at end of period	1,747,037	1,118,506
Noncash investing activities:
Transfers of loans to OREO	$ 3,829	$ 19,228

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2017
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 considers all of its principal business activities to be bank related. All significant intercompany accounts and transactions have been eliminated in the consolidated financial statements. Dollars are in thousands, except per share or unless otherwise noted. New Accounting Standards 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, modifications. Companies will apply the modification accounting guidance if the value, vesting conditions or classification of the award changes. The new guidance should reduce diversity in practice and result in fewer changes to the terms of an award being accounted for as modifications, as the guidance will allow companies to make certain non-substantive No. 2017-09 No. 2017-09 In March 2017, the FASB issued ASU 2017-07, 2017-07 2017-07 In January 2017, the FASB issued ASU 2017-04, 2017-04 2017-04 In January 2017, the FASB issued ASU 2017-01, 2017-01 2017-01 In August 2016, the FASB issued ASU 2016-15, 2016-15 2016-15 2016-15 In June 2016, the FASB issued ASU 2016-13, 2016-13 available-for-sale 2016-13 period in which the guidance is effective. ASU 2016-13 In March 2016, the FASB issued ASU 2016-09, 2016-09 2016-09 2016-09 2016-09 tax-related 2016-09 In February 2016, the FASB issued ASU 2016-02, 2016-02 2016-02 right-of-use 2016-02 In January 2016, the FASB issued ASU 2016-01, 2016-01 2016-01 available-for-sale 2016-01 In May 2014, the FASB issued ASU 2014-09, 2014-09 2014-09 2014-09 2014-09

Mergers and Acquisitions

Mergers and Acquisitions	9 Months Ended
	Sep. 30, 2017
Business Combinations [Abstract]
Mergers and Acquisitions	2. MERGERS AND ACQUISITIONS Cardinal Financial Corporation On April 21, 2017 (Cardinal Acquisition Date), United acquired 100% of the outstanding common stock of Cardinal Financial Corporation (Cardinal), headquartered in Tysons Corner, Virginia. The acquisition of Cardinal expands United’s existing footprint in the Washington, D.C. Metropolitan Statistical Area. At consummation, Cardinal had assets of $4,136,008, loans of $3,313,033 and deposits of $3,344,740. Cardinal also operated George Mason Mortgage, LLC (George Mason), a residential mortgage lending company based in Fairfax, Virginia with offices located in Virginia, Maryland, North Carolina, South Carolina and the District of Columbia. As a result of the merger, George Mason became an indirectly-owned subsidiary of United. The merger was accounted for under the acquisition method of accounting. The results of operations of Cardinal are included in the consolidated results of operations from the Cardinal Acquisition Date. The aggregate purchase price was approximately $975,254, including common stock valued at $972,499, stock options assumed valued at $2,741, and cash paid for fractional shares of $14. The number of shares issued in the transaction was 23,690,589, which were valued based on the closing market price of $41.05 for United’s common shares on April 21, 2017. The preliminary purchase price has been allocated to the identifiable tangible and intangible assets resulting in preliminary additions to goodwill, core deposit intangibles and the George Mason trade name intangible of $622,513, $28,723 and $1,230, respectively. The core deposit intangibles are expected to be amortized over ten years. The George Mason trade name provides a source of market recognition to attract potential clients and retain existing relationships. United believes the George Mason trade name provides a competitive advantage and is likely going to be used into perpetuity and thus will not be subject to amortization, but rather be evaluated for impairment. Because the consideration paid was greater than the net fair value of the acquired assets and liabilities, the Company recorded goodwill as part of the acquisition. None of the goodwill from the Cardinal acquisition is expected to be deductible for tax purposes. United used an independent third party to help determine the fair values of the assets and liabilities acquired from Cardinal. As a result of the merger, United recorded preliminary fair value discounts of $144,434 on the loans acquired, $2,281 on leases and $8,738 on trust preferred issuances, respectively, and premiums of $4,408 on land acquired, $5,072 on interest-bearing deposits and $10,740 on long-term FHLB advances, respectively. The remaining discount and premium amounts are being accreted or amortized on an accelerated or straight-line basis over each asset’s or liability’s estimated remaining life at the time of acquisition except for loans and land. The discount on loans will be accreted into income based on the effective yield method. The premium on land will not be amortized. At September 30, 2017, the discounts on leases and trust preferred issuances had an average estimated remaining life of 6.00 years and 16.97 years, respectively, and the premiums on the interest-bearing deposits and the FHLB advances each had an average estimated remaining life of 5.00 years and 4.81 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, 2017. The estimated fair values of the acquired assets and assumed liabilities, including identifiable intangible assets are preliminary as of September 30, 2017 and are subject to refinement as additional information relative to closing date fair values becomes available. Any subsequent adjustments to the fair values of acquired assets and liabilities assumed, identifiable intangible assets, or other purchase accounting adjustments will result in adjustments to goodwill within the measurement period following the date of acquisition. In many cases, determining the estimated fair value of the acquired assets and assumed liabilities required United to estimate cash flows expected to result from those assets and liabilities and to discount those cash flows at appropriate rates of interest. The most significant of those determinations related to the fair valuation of acquired loans. The fair value of the acquired loans was based on the present value of the expected cash flows. Periodic principal and interest cash flows were adjusted for expected losses and prepayments, then discounted to determine the present value and summed to arrive at the estimated fair value. For such loans, the excess of cash flows expected at acquisition over the estimated fair value is recognized as interest income over the remaining lives of the loans. The difference between contractually required payments at acquisition and the cash flows expected to be collected at acquisition reflects the impact of estimated credit losses and other factors, such as prepayments. In accordance with GAAP, there was no carry-over of Cardinal’s previously established allowance for loan losses. The acquired loans were divided into loans with evidence of credit quality deterioration, which are accounted for under ASC topic 310-30 310-20 In conjunction with the Cardinal merger, the acquired loan portfolio was accounted for at fair value as follows: April 21, 2017 Contractually required principal and interest at acquisition $ 4,211,734 Contractual cash flows not expected to be collected (56,176 ) Expected cash flows at acquisition 4,155,558 Interest component of expected cash flows (986,959 ) Basis in acquired loans at acquisition – estimated fair value $ 3,168,599 Included in the above table is information related to acquired impaired loans. Specifically, contractually required principal and interest, cash flows expected to be collected and estimated fair value of acquired impaired loans were $132,837, $108,275, and $86,696, respectively. The consideration paid for Cardinal’s common equity and the preliminary amounts of acquired identifiable assets and liabilities assumed as of the Cardinal Acquisition Date were as follows: Purchase price: Value of common shares issued (23,690,589 shares) $ 972,499 Fair value of stock options assumed 2,741 Cash for fractional shares 14 Total purchase price 975,254 Identifiable assets: Cash and cash equivalents 44,545 Investment securities 395,829 Loans held for sale 271,301 Loans 3,168,599 Premises and equipment 24,208 Core deposit intangibles 28,723 George Mason trade name intangible 1,230 Other assets 135,383 Total identifiable assets $ 4,069,818 Identifiable liabilities: Deposits $ 3,349,812 Short-term borrowings 96,215 Long-term borrowings 220,119 Unfavorable lease liability 2,281 Other liabilities 48,650 Total identifiable liabilities 3,717,077 Preliminary fair value of net assets acquired including identifiable intangible assets 352,741 Preliminary resulting goodwill $ 622,513 The operating results of United for the nine months ended September 30, 2017 include operating results of acquired assets and assumed liabilities subsequent to the Cardinal Acquisition Date. The operations of United’s metropolitan Washington D.C. geographic area, which primarily includes the acquired operations of Cardinal, provided $157,326 in total revenues, which represents net interest income plus other income, and $81,817 in net income from the period from the Cardinal Acquisition Date to September 30, 2017. These amounts are included in United’s consolidated financial statements as of and for the nine months ended September 30, 2017. Cardinal’s results of operations prior to the Cardinal Acquisition Date are not included in United’s consolidated financial statements. The following table presents certain unaudited pro forma information for the results of operations for the nine months ended September 30, 2017 and 2016, as if the Cardinal merger had occurred on January 1, 2017 and 2016, respectively. These results combine the historical results of Cardinal into United’s consolidated statement of income and, while certain adjustments were made for the estimated impact of certain fair valuation adjustments and other acquisition-related activity, they are not indicative of what would have occurred had the acquisition taken place on the indicated date nor are they intended to represent or be indicative of future results of operations. In particular, no adjustments have been made to eliminate the amount of Cardinal’s provision for credit losses for 2017 and 2016 that may not have been necessary had the acquired loans been recorded at fair value as of the beginning of 2017 and 2016. Additionally, United expects to achieve operating cost savings and other business synergies as a result of the acquisition which are not reflected in the pro forma amounts. Proforma Nine Months Ended September 30 2017 2016 Total Revenues (1) $ 573,790 $ 585,223 Net Income 136,104 160,731 (1) Represents net interest income plus other income Bank of Georgetown After the close of business on June 3, 2016 (BOG Acquisition Date), United acquired 100% of the outstanding common stock of Bank of Georgetown, a privately held community bank headquartered in Washington, D.C. With this transaction, United continues to expand its existing footprint in the D.C. Metro Region. The results of operations of Bank of Georgetown are included in the consolidated results of operations from the BOG Acquisition Date. At consummation, Bank of Georgetown had assets of $1,278,837, loans of $999,773, and deposits of $971,369. The transaction was accounted for under the acquisition method of accounting and accordingly, assets acquired, liabilities assumed and consideration exchanged were recorded at estimated fair value on the BOG Acquisition Date. The aggregate purchase price was $264,505, including common stock valued at $253,799, stock options assumed valued at $10,696, and cash paid for fractional shares of $10. The number of shares issued in the transaction was 6,527,746, which were valued based on the closing market price of $38.88 for United’s common shares on June 3, 2016. The purchase price has been allocated to the identifiable tangible and intangible assets resulting in additions to goodwill and core deposit intangibles of $152,845 and $9,058, respectively. The core deposit intangibles are being amortized over ten years. Because the consideration paid was greater than the net fair value of the acquired assets and liabilities, the Company recorded goodwill as part of the acquisition. None of the goodwill from the Bank of Georgetown acquisition is expected to be deductible for tax purposes. United used an independent third party to help determine the fair values of the assets and liabilities acquired from the Bank of Georgetown. As a result of the merger, United recorded fair value discounts of $43,072 on the loans acquired and $1,550 on leasehold improvements, respectively, and premiums on interest-bearing deposits acquired of $316 and a premium on long-term FHLB advances of $2,659. The remaining discount and premium amounts are being amortized or accreted on an accelerated basis over each asset’s or liability’s estimated remaining life at the time of acquisition. At September 30, 2017, the premium on the interest-bearing deposits and the FHLB advances had an estimated remaining life of 0.33 years and 7.92 years, respectively. United assumed approximately $300 of liabilities to provide severance benefits to terminated employees of Bank of Georgetown, which has no remaining balance as of September 30, 2017. The measurement period has closed and the estimated fair values of the acquired assets and assumed liabilities, including identifiable intangible assets were considered final as of June 30, 2017. In many cases, determining the estimated fair value of the acquired assets and assumed liabilities required United to estimate cash flows expected to result from those assets and liabilities and to discount those cash flows at appropriate rates of interest. The most significant of those determinations related to the fair valuation of acquired loans. The fair value of the acquired loans was based on the present value of the expected cash flows. Periodic principal and interest cash flows were adjusted for expected losses and prepayments, then discounted to determine the present value and summed to arrive at the estimated fair value. For such loans, the excess of cash flows expected at acquisition over the estimated fair value is recognized as interest income over the remaining lives of the loans. The difference between contractually required payments at acquisition and the cash flows expected to be collected at acquisition reflects the impact of estimated credit losses and other factors, such as prepayments. In accordance with GAAP, there was no carry-over of Bank of Georgetown’s previously established allowance for loan losses. In conjunction with the Bank of Georgetown merger, the acquired loan portfolio was accounted for at fair value as follows: June 3, 2016 Contractually required principal and interest at acquisition $ 1,275,398 Contractual cash flows not expected to be collected (33,980 ) Expected cash flows at acquisition 1,241,418 Interest component of expected cash flows (274,548 ) Basis in acquired loans at acquisition – estimated fair value $ 966,870 Included in the above table is information related to acquired impaired loans. Specifically, contractually required principal and interest, cash flows expected to be collected and estimated fair value of acquired impaired loans were $138,125, $117,564, and $95,570, respectively. The consideration paid for Bank of Georgetown’s common equity and the fair value of acquired identifiable assets and liabilities assumed as of the BOG Acquisition Date were as follows: Purchase price: Value of common shares issued (6,527,746 shares) $ 253,799 Fair value of stock options assumed 10,696 Cash for fractional shares 10 Total purchase price 264,505 Identifiable assets: Cash and cash equivalents 29,340 Investment securities 219,783 Loans 966,870 Premises and equipment 5,574 Core deposit intangibles 9,058 Other assets 31,605 Total identifiable assets $ 1,262,230 Identifiable liabilities: Deposits $ 971,685 Short-term borrowings 101,021 Long-term borrowings 67,659 Other liabilities 11,532 Total identifiable liabilities 1,151,897 Fair value of net assets acquired including identifiable intangible assets 110,333 Resulting goodwill $ 154,172

Investment Securities

Investment Securities	9 Months Ended
	Sep. 30, 2017
Investments, Debt and Equity Securities [Abstract]
Investment Securities	3. INVESTMENT SECURITIES Securities held for indefinite periods of time and all marketable equity securities 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, 2017 Gross Gross Estimated Cumulative Amortized Unrealized Unrealized Fair OTTI in Cost Gains Losses Value AOCI (1) U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 115,224 $ 864 $ 222 $ 115,866 $ 0 State and political subdivisions 305,096 2,567 2,522 305,141 0 Residential mortgage-backed securities Agency 715,003 3,819 4,122 714,700 0 Non-agency 5,259 587 0 5,846 86 Commercial mortgage-backed securities Agency 420,115 2,081 1,404 420,792 0 Asset-backed securities 13,422 10 3 13,429 0 Trust preferred collateralized debt obligations 38,186 317 6,844 31,659 20,770 Single issue trust preferred securities 13,404 404 1,341 12,467 0 Other corporate securities 18,998 256 0 19,254 0 Marketable equity securities 9,950 541 11 10,480 0 Total $ 1,654,657 $ 11,446 $ 16,469 $ 1,649,634 $ 20,856 December 31, 2016 Gross Gross Estimated Cumulative Amortized Unrealized Unrealized Fair OTTI in Cost Gains Losses Value AOCI (1) U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 95,247 $ 698 $ 159 $ 95,786 $ 0 State and political subdivisions 196,350 1,364 4,902 192,812 0 Residential mortgage-backed securities Agency 585,208 3,999 5,111 584,096 0 Non-agency 6,629 426 12 7,043 86 Commercial mortgage-backed securities Agency 304,635 1,948 1,242 305,341 0 Asset-backed securities 217 0 0 217 0 Trust preferred collateralized debt obligations 48,558 729 15,735 33,552 25,952 Single issue trust preferred securities 13,363 284 2,170 11,477 0 Other corporate securities 14,996 66 0 15,062 0 Marketable equity securities 12,436 1,398 6 13,828 0 Total $ 1,277,639 $ 10,912 $ 29,337 $ 1,259,214 $ 26,038 (1) Non-credit before-tax. The following is a summary of securities available-for-sale Less than 12 months 12 months or longer Fair Unrealized Fair Unrealized Value Losses Value Losses September 30, 2017 U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 27,053 $ 128 $ 19,932 $ 94 State and political subdivisions 83,310 896 38,004 1,626 Residential mortgage-backed securities Agency 351,936 3,410 31,690 712 Non-agency 0 0 0 0 Commercial mortgage-backed securities Agency 228,307 1,218 12,272 186 Asset-backed securities 6,760 3 0 0 Trust preferred collateralized debt obligations 0 0 29,544 6,844 Single issue trust preferred securities 0 0 4,365 1,341 Marketable equity securities 0 0 352 11 Total $ 697,366 $ 5,655 $ 136,159 $ 10,814 Less than 12 months 12 months or longer Fair Unrealized Fair Unrealized Value Losses Value Losses December 31, 2016 U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 24,101 $ 159 $ 0 $ 0 State and political subdivisions 116,300 4,902 0 0 Residential mortgage-backed securities Agency 309,376 5,111 0 0 Non-agency 0 0 218 12 Commercial mortgage-backed securities Agency 162,479 1,242 0 0 Asset-backed securities 0 0 0 0 Trust preferred collateralized debt obligations 0 0 28,579 15,735 Single issue trust preferred securities 0 0 8,185 2,170 Marketable equity securities 357 6 0 0 Total $ 612,613 $ 11,420 $ 36,982 $ 17,917 Marketable equity securities consist mainly of equity securities of financial institutions and mutual funds within a rabbi trust for the payment of benefits under a deferred compensation plan for certain key officers of United and its subsidiaries. The following table shows the proceeds from maturities, sales and calls of available for sale securities and the gross realized gains and losses on sales and calls of those securities that have been included in earnings as a result of 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 2017 2016 2017 2016 Proceeds from sales and calls $ 64,257 $ 174,015 $ 631,561 $ 368,246 Gross realized gains 1,781 3 2,840 259 Gross realized losses 1,314 1 1,396 7 At September 30, 2017, gross unrealized losses on available for sale securities were $16,469 on 375 securities of a total portfolio of 822 available for sale securities. Securities in an unrealized loss position at September 30, 2017 consisted primarily of pooled trust preferred collateralized debt obligations (“Trup Cdos”), single issue trust preferred securities and agency residential mortgage-backed securities. The Trup Cdos and the single issue trust preferred securities relate mainly to securities of financial institutions. The state and political subdivisions securities relate to securities issued by various municipalities. The agency residential mortgage-backed securities relate to residential properties and provide a guaranty of full and timely payments of principal and interest by the issuing agency. In determining whether or not a security is other-than-temporarily impaired (“OTTI”), management considered the severity and the duration of the loss in conjunction with United’s positive intent and the more likely than not ability to hold these securities to recovery of their cost basis or maturity. State and political subdivisions United’s state and political subdivisions portfolio relates to securities issued by various municipalities located throughout the United States. The total amortized cost of available for sale state and political subdivision securities was $305,096 at September 30, 2017. As of September 30, 2017, approximately 75% 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, 2017. 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, 2017. 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 $1,135,118 at September 30, 2017. Of the $1,135,118 amount, $420,115 was related to agency commercial mortgage-backed securities and $715,003 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, 2017. 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 2017, 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 available for sale single issue trust preferred securities’ ratings ranged from a low of Ba1 to a high of BBB-. Trust preferred collateralized debt obligations (Trup Cdos) In order to determine how and when the Company recognizes OTTI, the Company first assesses its intentions regarding any sale of securities as well as the likelihood that it would be required to sell prior to recovery of the amortized cost. As of September 30, 2017, the Company has determined that it does not intend to sell any pooled trust preferred security and that it is not more likely than not that the Company will be required to sell such securities before recovery of their amortized cost. To determine a net realizable value and assess whether other-than-temporary impairment existed, management performed detailed cash flow analysis to determine whether, in management’s judgment, it was more likely that United would not recover the entire amortized cost basis of the security. The Company discounts the security-specific cash flow projection at the security-specific interest rate and compares the present value to the amortized cost. Management’s cash flow analysis was performed for each security and considered the current deferrals and defaults within the underlying collateral, the likelihood that current deferrals would cure or ultimately default, potential future deferrals and defaults, potential prepayments, cash reserves, excess interest spread, credit analysis of the underlying collateral and the priority of payments in the cash flow structure. The underlying collateral analysis for each issuer took into consideration multiple factors including capital adequacy, earnings trends and asset quality. After completing its analysis of estimated cash flows, management determined that none of the Trup Cdos experienced an adverse change in cash flows during the third quarter of 2017, as the expected discounted cash flows from these particular securities were greater than or equal to the discounted cash flows originally expected at purchase or from the previous date of other-than-temporary impairment (cash flows are discounted at the contractual coupon rate for purposes of assessing OTTI). There was no credit-related other-than-temporary impairment recognized in earnings for the third quarter of 2017 related to these securities. The balance of noncredit-related other-than-temporary impairment recognized on United’s Trup Cdos portfolio was $20,770 at September 30, 2017. The following is a summary of the available for sale Trup Cdos as of September 30, 2017: Amortized Cost Class Amortized Cost Fair Value Unrealized Loss Investment Split Below Senior – Bank $ 5,208 $ 5,287 $ (79 ) $ 3,410 $ 0 $ 1,798 Mezzanine – Bank (now in senior position) 6,428 5,518 910 0 0 6,428 Mezzanine – Bank 22,656 17,918 4,738 0 0 22,656 Mezzanine – Bank & Insurance (combination) 3,894 2,936 958 0 0 3,894 Totals $ 38,186 $ 31,659 $ 6,527 $ 3,410 $ 0 $ 34,776 While a large difference remains between the fair value and amortized cost, the Company believes the remaining unrealized losses are related to the illiquid market for Trup Cdos rather than an adverse change in expected cash flows. The expected future cash flow substantiates the return of the remaining amortized cost of the security. The Company believes the following evidence supports the position that the remaining unrealized loss is related to the illiquid market for Trup Cdos: • The market for new issuance of Trup Cdos was robust from 2000 to 2007 with an estimated $60 billion in new issuance. The new market issuances came to an abrupt halt in 2007. • The secondary market for Trup Cdos ultimately became illiquid and although the market has improved, trading activity remains limited on these securities. In making this determination, the Company holds discussions with institutional traders to identify trends in the number and type of transactions related to the Trup Cdos. • The presence of a below-investment grade rating severely limits the pool of available buyers and contributes to the illiquidity of the market. • Trup Cdos have a more complex structure than most debt instruments, making projections of tranche returns difficult for non-specialists • The variability of cash flows at the time the securities were originated was expected to be very limited. Due to the financial crisis, Trup Cdos have experienced more substantive variability of cash flows compared to expectations, resulting in a higher risk premium when evaluating discount rates. • The limited, yet relevant, observable inputs indicate that market yield requirements for Trup Cdos, on a credit-adjusted basis, remained very high relative to discount rates at purchase and compared to other similarly rated debt securities. Overall, the Company believes the lack of new issuances, illiquid secondary market, limited pool of buyers, below investment grade ratings, and complex structures are the key drivers of the remaining unrealized losses in the Company’s Trup Cdos and the robust expected cash flow analysis substantiates the return of the remaining amortized cost under ASC topic 320. Management also considered the ratings of the Company’s bonds in its portfolio and the extent of downgrades in United’s impairment analysis. However, management considered it imperative to independently perform its own credit analysis based on cash flows as described. The ratings of the investment grade Trup Cdos in the table above range from a low of AA to a high of Aaa. The below investment grade Trup Cdos range from a low of C to a high of Ba2. On the Trup Cdos that have not been deemed to be other-than-temporarily impaired, the collateralization ratios range from a low of 105.4% to a high of 414.5%, with a median of 260.0%, and a weighted average of 283.8%. The collateralization ratio is defined as the current performing collateral in a security, divided by the current balance of the specific tranche the Company owns, plus any debt which is senior or pari passu with the Company’s security’s priority level. Performing collateral excludes the balance of any issuer that has either defaulted or has deferred its interest payment. It is not uncommon for the collateralization of a security that is not other-than-temporarily impaired to be less than 100% due to the excess spread built into the securitization structure. Except for the debt securities that have already been deemed to be other-than-temporarily impaired, management does not believe any other individual security with an unrealized loss as of September 30, 2017 is other-than-temporarily impaired. For these securities, United believes the decline in value resulted from changes in market interest rates, credit spreads and liquidity, not a change in the expected contractual cash flows. Based on a review of each of the securities in the investment portfolio, management concluded that it expected to recover the amortized cost basis of the investment in such securities. Equity securities The amortized cost of United’s equity securities was $9,950 at September 30, 2017. For equity securities, management has evaluated the near-term prospects of the investment in relation to the severity and duration of any impairment and based on that evaluation, management determined that no equity securities were other-than-temporarily impaired at September 30, 2017. Other investment securities (cost method) During the third quarter of 2017, United also evaluated all of its cost method investments to determine if certain events or changes in circumstances during the third quarter of 2017 had a significant adverse effect on the fair value of any of its cost method securities. United determined that there were no events or changes in circumstances during the third quarter which would have an adverse effect on the fair value of any of its cost method securities. Therefore, no impairment was recorded. Below is a progression of the credit losses on securities which United has recorded other-than-temporary charges. These charges were recorded through earnings and other comprehensive income. Three Months Ended September 30 Nine Months Ended September 30 2017 2016 2017 2016 Balance of cumulative credit losses at beginning of period $ 22,162 $ 22,162 $ 22,162 $ 23,773 Additional credit losses on securities for which OTTI was previously recognized 0 0 0 33 Reductions during the period for securities for which the amount previously recognized in other comprehensive income was recognized in earnings (4,102 ) 0 (4,102 ) (1,644 ) Balance of cumulative credit losses at end of period $ 18,060 $ 22,162 $ 18,060 $ 22,162 The amortized cost and estimated fair value of securities available for sale at September 30, 2017 and December 31, 2016 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, 2017 December 31, 2016 Estimated Estimated Amortized Fair Amortized Fair Cost Value Cost Value Due in one year or less $ 57,720 $ 57,622 $ 53,286 $ 53,330 Due after one year through five years 370,020 371,007 296,181 297,385 Due after five years through ten years 342,176 343,326 213,094 213,791 Due after ten years 874,791 867,199 702,642 680,880 Marketable equity securities 9,950 10,480 12,436 13,828 Total $ 1,654,657 $ 1,649,634 $ 1,277,639 $ 1,259,214 The amortized cost and estimated fair values of securities held to maturity are summarized as follows: September 30, 2017 Gross Gross Estimated Amortized Unrealized Unrealized Fair Cost Gains Losses Value U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 5,215 $ 400 $ 0 $ 5,615 State and political subdivisions 5,674 12 0 5,686 Residential mortgage-backed securities Agency 26 4 0 30 Single issue trust preferred securities 9,400 0 842 8,558 Other corporate securities 20 0 0 20 Total $ 20,335 $ 416 $ 842 $ 19,909 December 31, 2016 Gross Gross Estimated Amortized Unrealized Unrealized Fair Cost Gains Losses Value U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 5,295 $ 570 $ 0 $ 5,865 State and political subdivisions 8,598 17 0 8,615 Residential mortgage-backed securities Agency 30 5 0 35 Single issue trust preferred securities 19,315 0 2,672 16,643 Other corporate securities 20 0 0 20 Total $ 33,258 $ 592 $ 2,672 $ 31,178 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 2017 and 2016. The amortized cost and estimated fair value of debt securities held to maturity at September 30, 2017 and December 31, 2016 by contractual maturity are shown below. Expected maturities may differ from contractual maturities because the issuers may have the right to call or prepay obligations without penalties. September 30, 2017 December 31, 2016 Estimated Estimated Amortized Fair Amortized Fair Cost Value Cost Value Due in one year or less $ 0 $ 0 $ 1,040 $ 1,041 Due after one year through five years 9,189 9,600 8,268 8,850 Due after five years through ten years 5,726 5,382 3,585 3,589 Due after ten years 5,420 4,927 20,365 17,698 Total $ 20,335 $ 19,909 $ 33,258 $ 31,178 The carrying value of securities pledged to secure public deposits, securities sold under agreements to repurchase, and for other purposes as required or permitted by law, approximated $1,312,813 and $1,137,408 at September 30, 2017 and December 31, 2016, respectively.

Loans

Loans	9 Months Ended
	Sep. 30, 2017
Receivables [Abstract]
Loans	4. LOANS Major classes of loans are as follows: September 30, 2017 December 31, Commercial, financial and agricultural: Owner-occupied commercial real estate $ 1,364,757 $ 1,049,885 Nonowner-occupied commercial real estate 4,686,183 3,425,453 Other commercial loans 1,757,741 1,613,437 Total commercial, financial & agricultural 7,808,681 6,088,775 Residential real estate 3,050,868 2,403,437 Construction & land development 1,599,632 1,255,738 Consumer: Bankcard 13,775 14,187 Other consumer 683,898 594,582 Total gross loans $ 13,156,854 $ 10,356,719 The table above does not include loans held for sale of $315,031 and $8,445 at September 30, 2017 and December 31, 2016, respectively. The increase was due to the acquisition of Cardinal and it mortgage banking subsidiary, George Mason. 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 $227,754 or 1.73% of total gross loans at September 30, 2017 and $171,596 or 1.66% of total gross loans at December 31, 2016. The contractual principal in these acquired impaired loans was $310,609 and $231,096 at September 30, 2017 and December 31, 2016, 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 2017 follows: Accretable yield at the beginning of the period $ 29,165 Accretion (including cash recoveries) (11,312 ) Additions 17,444 Net reclassifications to accretable from non-accretable 2,727 Disposals (including maturities, foreclosures, and charge-offs) (2,367 ) Accretable yield at the end of the period $ 35,657 United’s subsidiary banks have made loans to the directors and officers of United and its subsidiaries, and to their affiliates. The aggregate dollar amount of these loans was $364,774 and $255,476 at September 30, 2017 and December 31, 2016, respectively.

Credit Quality

Credit Quality	9 Months Ended
	Sep. 30, 2017
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, 2017, United had TDRs of $46,132 as compared to $21,152 as of December 31, 2016. Of the $46,132 aggregate balance of TDRs at September 30, 2017, $29,717 was on nonaccrual status and included in the “Loans on Nonaccrual Status” on the following pages. Of the $21,152 aggregate balance of TDRs at December 31, 2016, $11,106 was on nonaccrual status and included in the “Loans on Nonaccrual Status” on the following page. As of September 30, 2017, there were no commitments to lend additional funds to debtors owing receivables whose terms have been modified in TDRs. At September 30, 2017, United had restructured loans in the amount of $2,043 that were modified by a reduction in the interest rate, $4,507 that were modified by a combination of a reduction in the interest rate and the principal and $39,582 that was modified by a change in terms. A loan acquired and accounted for under ASC topic 310-30 No loans were restructured during the three months ended September 30, 2017. The following table sets forth United’s troubled debt restructurings that were restructured during the three months ended September 30, 2016, segregated by class of loans: Troubled Debt Restructurings For the Three Months Ended September 30, 2016 Number of Pre- Modification Post- Commercial real estate: Owner-occupied 0 $ 0 $ 0 Nonowner-occupied 0 0 0 Other commercial 1 110 110 Residential real estate 0 0 0 Construction & land development 0 0 0 Consumer: Bankcard 0 0 0 Other consumer 0 0 0 Total 1 $ 110 $ 110 The following table sets forth United’s troubled debt restructurings that were restructured during the nine months ended September 30, 2017 and 2016, segregated by class of loans: Troubled Debt Restructurings For the Nine Months Ended September 30, 2017 September 30, 2016 Number of Pre- Modification Outstanding Recorded Investment Post- Modification Outstanding Recorded Investment Number of Contracts Pre- Modification Outstanding Recorded Investment Post- Modification Outstanding Recorded Investment Commercial real estate: Owner-occupied 1 $ 5,333 $ 5,333 1 $ 1,190 $ 1,184 Nonowner-occupied 0 0 0 0 0 0 Other commercial 8 24,102 22,291 5 2,250 1,725 Residential real estate 0 0 0 1 1,400 1,400 Construction & land development 1 1,456 1,400 0 0 0 Consumer: Bankcard 0 0 0 0 0 0 Other consumer 0 0 0 0 0 0 Total 10 $ 30,891 $ 29,024 7 $ 4,840 $ 4,309 During the first nine months of 2017, $29,024 of restructured loans were modified by a change in terms. During the third quarter and first nine months of 2016, $110 and $2,909, respectively, of restructured loans were modified by a change in loan terms. In addition, during the first nine months of 2016, $1,400 of restructured loans were modified by a combination of a reduction in the interest rate and an extension of the maturity date. 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, 2017. Three Months Ended September 30, 2017 Nine Months Ended September 30, 2017 (In thousands) Number of Recorded Number of Recorded Troubled Debt Restructurings Commercial real estate: Owner-occupied 0 $ 0 0 $ 0 Nonowner-occupied 0 0 0 0 Other commercial 1 1,495 1 1,495 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 $ 1,495 1 $ 1,495 No loans restructured during the twelve-month period ended September 30, 2016 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, 2017 30-89 90 Days or Total Past Current & Total Financing Recorded & Accruing Commercial real estate: Owner-occupied $ 9,704 $ 6,912 $ 16,616 $ 1,348,141 $ 1,364,757 $ 0 Nonowner-occupied 7,686 20,797 28,483 4,657,700 4,686,183 0 Other commercial 13,589 79,342 92,931 1,664,810 1,757,741 802 Residential real estate 33,654 25,564 59,218 2,991,650 3,050,868 5,298 Construction & land development 3,351 17,852 21,203 1,578,429 1,599,632 14,828 Consumer: Bankcard 385 210 595 13,180 13,775 210 Other consumer 8,087 1,305 9,392 674,506 683,898 1,111 Total $ 76,456 $ 151,982 $ 228,438 $ 12,928,416 $ 13,156,854 $ 22,249 (1) Other includes loans with a recorded investment of $227,754 acquired and accounted for under ASC topic 310-30 Age Analysis of Past Due Loans As of December 31, 2016 (In thousands) 30-89 90 Days or Total Past Current & Total Financing Recorded & Accruing Commercial real estate: Owner-occupied $ 5,850 $ 3,981 $ 9,831 $ 1,040,054 $ 1,049,885 $ 94 Nonowner-occupied 9,288 20,847 30,135 3,395,318 3,425,453 172 Other commercial 15,273 42,766 58,039 1,555,398 1,613,437 2,518 Residential real estate 29,976 25,991 55,967 2,347,470 2,403,437 4,216 Construction & land development 3,809 7,779 11,588 1,244,150 1,255,738 33 Consumer: Bankcard 422 141 563 13,624 14,187 141 Other consumer 10,015 1,712 11,727 582,855 594,582 1,412 Total $ 74,633 $ 103,217 $ 177,850 $ 10,178,869 $ 10,356,719 $ 8,586 (1) Other includes loans with a recorded investment of $171,596 acquired and accounted for under ASC topic 310-30 The following table sets forth United’s nonaccrual loans, segregated by class of loans: Loans on Nonaccrual Status September 30, 2017 December 31, 2016 Commercial real estate: Owner-occupied $ 6,912 $ 3,887 Nonowner-occupied 20,797 20,675 Other commercial 78,540 40,248 Residential real estate 20,266 21,775 Construction & land development 3,024 7,746 Consumer: Bankcard 0 0 Other consumer 194 300 Total $ 129,733 $ 94,631 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, 2017 Commercial Real Estate Other Construction & Land Owner- Nonowner- Grade: Pass $ 1,282,657 $ 4,544,799 $ 1,611,250 $ 1,498,656 Special mention 23,827 44,080 47,450 19,872 Substandard 58,273 97,304 98,933 81,104 Doubtful 0 0 108 0 Total $ 1,364,757 $ 4,686,183 $ 1,757,741 $ 1,599,632 As of December 31, 2016 Commercial Real Estate Other Construction & Land Owner- Nonowner- Grade: Pass $ 963,503 $ 3,284,497 $ 1,463,797 $ 1,126,742 Special mention 20,490 36,462 26,537 52,327 Substandard 65,892 104,494 122,893 76,669 Doubtful 0 0 210 0 Total $ 1,049,885 $ 3,425,453 $ 1,613,437 $ 1,255,738 Credit Quality Indicators Consumer Credit Exposure As of September 30, 2017 Residential Bankcard Other Grade: Pass $ 2,999,614 $ 13,180 $ 674,447 Special mention 18,953 385 8,134 Substandard 32,301 210 1,317 Doubtful 0 0 0 Total $ 3,050,868 $ 13,775 $ 683,898 As of December 31, 2016 Residential Bankcard Other Grade: Pass $ 2,348,017 $ 13,624 $ 582,704 Special mention 18,240 422 10,132 Substandard 36,995 141 1,746 Doubtful 185 0 0 Total $ 2,403,437 $ 14,187 $ 594,582 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, 2017 December 31, 2016 Recorded Unpaid Related Recorded Unpaid Related With no related allowance recorded: Commercial real estate: Owner-occupied $ 64,592 $ 65,355 $ 0 $ 46,575 $ 47,108 $ 0 Nonowner-occupied 143,100 143,552 0 92,654 93,104 0 Other commercial 55,022 58,785 0 46,064 48,308 0 Residential real estate 20,873 22,546 0 22,747 24,404 0 Construction & land 30,959 33,225 0 19,863 21,746 0 Consumer: Bankcard 0 0 0 0 0 0 Other consumer 16 16 0 36 36 0 With an allowance recorded: Commercial real estate: Owner-occupied $ 8,220 $ 8,220 $ 923 $ 1,787 $ 2,082 $ 815 Nonowner-occupied 12,182 12,182 1,786 17,938 17,938 2,524 Other commercial 70,344 80,415 21,890 43,774 46,188 13,441 Residential real estate 13,743 15,082 1,659 12,066 12,801 3,431 Construction & land 1,411 5,910 488 4,940 7,899 3,206 Consumer: Bankcard 0 0 0 0 0 0 Other consumer 0 0 0 0 0 0 Total: Commercial real estate: Owner-occupied $ 72,812 $ 73,575 $ 923 $ 48,362 $ 49,190 $ 815 Nonowner-occupied 155,282 155,734 1,786 110,592 111,042 2,524 Other commercial 125,366 139,200 21,890 89,838 94,496 13,441 Residential real estate 34,616 37,628 1,659 34,813 37,205 3,431 Construction & land 32,370 39,135 488 24,803 29,645 3,206 Consumer: Bankcard 0 0 0 0 0 0 Other consumer 16 16 0 36 36 0 Impaired Loans For the Three Months Ended September 30, 2017 September 30, 2016 Average Interest Average Interest With no related allowance recorded: Commercial real estate: Owner-occupied $ 58,980 $ 376 $ 38,199 $ 531 Nonowner-occupied 108,959 312 71,154 321 Other commercial 57,317 306 45,028 1,221 Residential real estate 19,553 74 27,214 170 Construction & land development 23,846 552 28,730 46 Consumer: Bankcard 0 0 0 0 Other consumer 25 0 35 0 With an allowance recorded: Commercial real estate: Owner-occupied $ 11,624 $ 131 $ 3,353 $ 36 Nonowner-occupied 13,408 89 14,046 122 Other commercial 72,835 216 33,195 42 Residential real estate 15,225 16 8,579 52 Construction & land development 1,641 21 8,591 56 Consumer: Bankcard 0 0 0 0 Other consumer 0 0 0 0 Total: Commercial real estate: Owner-occupied $ 70,604 $ 507 $ 41,552 $ 567 Nonowner-occupied 122,367 401 85,200 443 Other commercial 130,152 522 78,223 1,263 Residential real estate 34,778 90 35,793 222 Construction & land development 25,487 573 37,321 102 Consumer: Bankcard 0 0 0 0 Other consumer 25 0 35 0 Impaired Loans For the Nine Months Ended September 30, 2017 September 30, 2016 Average Interest Average Interest With no related allowance recorded: Commercial real estate: Owner-occupied $ 55,506 $ 1,011 $ 34,030 $ 715 Nonowner-occupied 93,254 811 70,081 714 Other commercial 55,891 895 37,805 1,446 Residential real estate 19,634 206 26,737 406 Construction & land development 20,706 563 26,559 112 Consumer: Bankcard 0 0 0 0 Other consumer 29 0 32 0 With an allowance recorded: Commercial real estate: Owner-occupied $ 9,392 $ 424 $ 3,603 $ 92 Nonowner-occupied 14,595 363 10,416 360 Other commercial 65,142 1,410 34,755 270 Residential real estate 15,186 89 9,129 77 Construction & land development 2,872 64 10,300 146 Consumer: Bankcard 0 0 0 0 Other consumer 0 0 0 0 Total: Commercial real estate: Owner-occupied $ 64,898 $ 1,435 $ 37,633 $ 807 Nonowner-occupied 107,849 1,174 80,497 1,074 Other commercial 121,033 2,305 72,560 1,716 Residential real estate 34,820 295 35,866 483 Construction & land development 23,578 627 36,859 258 Consumer: Bankcard 0 0 0 0 Other consumer 29 0 32 0 At September 30, 2017 and December 31, 2016, other real estate owned (“OREO”) included in other assets in the Consolidated Balance Sheets was $26,826 and $31,510, 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, 2017 and December 31, 2016, the recorded investment of consumer mortgage loans secured by residential real estate properties for which formal foreclosure proceedings are in process was $116 and $660, respectively.

Allowance for Credit Losses

Allowance for Credit Losses	9 Months Ended
	Sep. 30, 2017
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, 2017, the re-estimation United maintains an allowance for loan losses and a reserve for lending-related commitments such as unfunded loan commitments and letters of credit. The reserve for lending-related commitments of $804 and $1,044 at September 30, 2017 and December 31, 2016, 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, 2017 Commercial Real Estate Construction Allowance for Owner- Nonowner- Other Residential Real & Land Consumer Estimated Total Allowance for Loan Losses: Beginning balance $ 5,129 $ 7,099 $ 37,287 $ 12,479 $ 7,514 $ 2,715 $ 760 $ 72,983 Charge-offs 518 0 4,854 299 54 632 0 6,357 Recoveries 397 168 156 60 89 151 0 1,021 Provision 230 (472 ) 8,782 (1,385 ) 452 281 (609 ) 7,279 Ending balance $ 5,238 $ 6,795 $ 41,371 $ 10,855 $ 8,001 $ 2,515 $ 151 $ 74,926 Allowance for Loan Losses and Carrying Amount of Loans For the Nine Months Ended September 30, 2017 Commercial Real Estate Construction Allowance for Owner- Nonowner- Other Residential & Land Consumer Estimated Total Allowance for Loan Losses: Beginning balance $ 5,273 $ 6,883 $ 33,087 $ 13,770 $ 10,606 $ 2,805 $ 347 $ 72,771 Charge-offs 1,433 295 14,883 2,331 2,576 2,046 0 23,564 Recoveries 1,590 198 821 352 705 624 0 4,290 Provision (192 ) 9 22,346 (936 ) (734 ) 1,132 (196 ) 21,429 Ending balance $ 5,238 $ 6,795 $ 41,371 $ 10,855 $ 8,001 $ 2,515 $ 151 $ 74,926 Ending Balance: individually evaluated for impairment $ 923 $ 1,786 $ 21,890 $ 1,659 $ 488 $ 0 $ 0 $ 26,746 Ending Balance: collectively evaluated for impairment $ 4,315 $ 5,009 $ 19,481 $ 9,196 $ 7,513 $ 2,515 $ 151 $ 48,180 Ending Balance: loans acquired with deteriorated credit quality $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 Financing receivables: Ending balance $ 1,364,757 $ 4,686,183 $ 1,757,741 $ 3,050,868 $ 1,599,632 $ 697,673 $ 0 $ 13,156,854 Ending Balance: individually evaluated for impairment $ 32,888 $ 25,220 $ 89,559 $ 15,574 $ 16,879 $ 0 $ 0 $ 180,120 Ending Balance: collectively evaluated for impairment $ 1,297,668 $ 4,537,792 $ 1,636,037 $ 3,021,173 $ 1,558,653 $ 697,657 $ 0 $ 12,748,980 Ending Balance: loans acquired with deteriorated credit quality $ 34,201 $ 123,171 $ 32,145 $ 14,121 $ 24,100 $ 16 $ 0 $ 227,754 Allowance for Loan Losses and Carrying Amount of Loans For the Year Ended December 31, 2016 Commercial Real Estate Other Residential Construction Consumer Allowance Total Owner- Nonowner- & Land Estimated Allowance for Loan Losses: Beginning balance $ 3,637 $ 5,309 $ 31,328 $ 15,148 $ 18,205 $ 1,995 $ 104 $ 75,726 Charge-offs 5,281 419 20,430 4,597 2,659 2,794 0 36,180 Recoveries 3,071 675 3,452 639 433 446 0 8,716 Provision 3,846 1,318 18,737 2,580 (5,373 ) 3,158 243 24,509 Ending balance $ 5,273 $ 6,883 $ 33,087 $ 13,770 $ 10,606 $ 2,805 $ 347 $ 72,771 Ending Balance: individually evaluated for impairment $ 815 $ 2,524 $ 13,441 $ 3,431 $ 3,206 $ 0 $ 0 $ 23,417 Ending Balance: collectively evaluated for impairment $ 4,458 $ 4,359 $ 19,646 $ 10,339 $ 7,400 $ 2,805 $ 347 $ 49,354 Ending Balance: loans acquired with deteriorated credit quality $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 Financing receivables: Ending balance $ 1,049,885 $ 3,425,453 $ 1,613,437 $ 2,403,437 $ 1,255,738 $ 608,769 $ 0 $ 10,356,719 Ending Balance: individually evaluated for impairment $ 18,976 $ 26,835 $ 56,091 $ 14,766 $ 8,152 $ 0 $ 0 $ 124,820 Ending Balance: collectively evaluated for impairment $ 1,005,999 $ 3,323,117 $ 1,527,479 $ 2,373,969 $ 1,221,006 $ 608,733 $ 0 $ 10,060,303 Ending Balance: loans acquired with deteriorated credit quality $ 24,910 $ 75,501 $ 29,867 $ 14,702 $ 26,580 $ 36 $ 0 $ 171,596

Intangible Assets

Intangible Assets	9 Months Ended
	Sep. 30, 2017
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, 2017 Community Banking Mortgage Banking Total Gross Accumulated Gross Accumulated Gross Accumulated Amortized intangible assets: Core deposit intangible assets $ 98,358 ($ 52,062 ) $ 0 ($ 0 ) $ 98,358 ($ 52,062 ) Non-amortized George Mason trade name $ 0 $ 1,230 $ 1,230 Goodwill not subject to amortization $ 1,466,152 $ 21,455 $ 1,487,607 December 31, 2016 Community Banking Total Gross Carrying Accumulated Gross Accumulated Amortized intangible assets: Core deposit intangible assets $ 69,635 ($ 46,681 ) $ 69,635 ($ 46,681 ) Goodwill not subject to amortization $ 863,767 $ 863,767 The following table provides a reconciliation of goodwill: Community Mortgage Total Goodwill at December 31, 2016 $ 863,767 $ 0 $ 863,767 Addition to goodwill from Bank of Georgetown acquisition 1,327 0 1,327 Preliminary addition to goodwill from Cardinal acquisition 601,058 21,455 622,513 Goodwill at September 30, 2017 $ 1,466,152 $ 21,455 $ 1,487,607 United incurred amortization expense on intangible assets of $2,240 and $5,381 for the quarter and nine months ended September 30, 2017, respectively, and $1,122 and $2,786 for the quarter and nine months ended September 30, 2016, respectively. The following table sets forth the anticipated amortization expense for intangible assets for the years subsequent to 2016: Year Amount 2017 $ 7,772 2018 8,039 2019 7,015 2020 6,309 2021 and thereafter 22,542

Short-Term Borrowings

Short-Term Borrowings	9 Months Ended
	Sep. 30, 2017
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 $264,000. 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, 2017, federal funds purchased were $25,800 while total securities sold under agreements to repurchase (“REPOs”) were $316,236. Included in the $316,236 of total REPOs is a wholesale REPOs of $50,000, assumed in the Virginia Commerce merger. This wholesale REPO is scheduled to mature in May of 2018. The securities sold under agreements to repurchase were accounted for as collateralized financial transactions. They were recorded at the amounts at which the securities were acquired or sold plus accrued interest. United has a $20,000 line of credit with an unrelated financial institution to provide for general liquidity needs. The line is an unsecured, revolving line of credit. The line will be renewable on a 360-day

Long-Term Borrowings

Long-Term Borrowings	9 Months Ended
	Sep. 30, 2017
Debt Disclosure [Abstract]
Long-Term Borrowings	9. LONG-TERM BORROWINGS United’s subsidiary banks are members of the Federal Home Loan Bank (“FHLB”). Membership in the FHLB makes available short-term and long-term borrowings from collateralized advances. All FHLB borrowings are collateralized by a mix of single-family residential mortgage loans, commercial loans and investment securities. At September 30, 2017, United had an unused borrowing amount of approximately $3,724,772 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, 2017, $1,272,115 of FHLB advances with a weighted-average interest rate of 1.43% are scheduled to mature within the next eight years. Overnight funds of $200,000 with an interest rate of 1.27% are included in the $1,272,115 above at September 30, 2017. The scheduled maturities of these FHLB borrowings are as follows: Year Amount 2017 $ 815,000 2018 131,776 2019 187,809 2020 42,247 2021 and thereafter 95,283 Total $ 1,272,115 At September 30, 2017, United had a total of fifteen 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, 2017 and December 31, 2016, the outstanding balance of the Debentures was $242,131 and $224,319, 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. However, with the acquisition of Cardinal on April 21, 2017, United’s total consolidated assets now exceeds $15 billion. As a result, United’s Trust Preferred Securities are no longer included in United’s Tier 1 capital but are included as a component of Tier 2 capital on a permanent basis without phase-out.

Commitments and Contingent Liab

Commitments and Contingent Liabilities	9 Months Ended
	Sep. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingent Liabilities	10. COMMITMENTS AND CONTINGENT LIABILITIES United is a party to financial instruments with off-balance-sheet United’s maximum exposure to credit loss in the event of nonperformance by the counterparty to the financial instrument for the loan commitments and standby letters of credit is the contractual or notional amount of those instruments. United uses the same policies in making commitments and conditional obligations as it does for on-balance Commitments to extend credit are agreements to lend to a customer as long as there is no violation of any condition established in the commitment contract. Commitments generally have fixed expiration dates or other termination clauses and may require the payment of a fee. Since many of the commitments are expected to expire without being drawn upon, the total commitment amounts do not necessarily, and historically do not, represent future cash requirements. The amount of collateral obtained, if deemed necessary upon the extension of credit, is based on management’s credit evaluation of the counterparty. United had approximately $4,118,868 and $2,823,396 of loan commitments outstanding as of September 30, 2017 and December 31, 2016, respectively, approximately half of which expire within one year. Included in the September 30, 2017 amount are commitments to extend credit of $407,610 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, 2017, United had no outstanding commercial letters of credit and $9 as of December 31, 2016. 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 $148,742 and $121,584 as of September 30, 2017 and December 31, 2016, 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 $575 as of September 30, 2017. 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, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Financial Instruments	11. DERIVATIVE FINANCIAL INSTRUMENTS United uses derivative instruments to help manage adverse prices 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. 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. 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, 2017 and December 31, 2016. Asset Derivatives September 30, 2017 December 31, 2016 Balance Sheet Location Notional Amount Fair Value Balance Sheet Location Fair Value Derivatives designated as hedging instruments Fair Value Hedges: Interest rate swap contracts (hedging commercial loans) Other assets $ 14,762 $ 40 Other assets $ 24 Total derivatives designated as hedging instruments $ 14,762 $ 40 $ 24 Derivatives not designated as hedging instruments Interest rate swap contracts Other assets $ 0 $ 0 Other assets $ 2,267 TBA mortgage-backed securities Other assets 322,500 501 Other assets 0 Interest rate lock commitments Other assets 169,588 7,027 Other assets 0 Total derivatives not designated as hedging instruments $ 492,088 $ 7,528 $ 2,267 Total asset derivatives $ 506,850 $ 7,568 $ 2,291 Liability Derivatives September 30, 2017 December 31, 2016 Balance Sheet Location Notional Amount Fair Value Balance Sheet Location Fair Value Derivatives designated as hedging instruments Fair Value Hedges: Interest rate swap contracts Other liabilities $ 76,869 $ 480 Other liabilities $ 338 Total derivatives designated as hedging instruments $ 76,869 $ 480 $ 338 Derivatives not designated as hedging instruments Interest rate swap contracts Other liabilities $ 0 $ 0 Other liabilities $ 2,267 Forward loan sales commitments Other liabilities 50,063 257 Other liabilities 0 Interest rate lock commitments Other liabilities 65,862 291 Other liabilities 0 Total derivatives not designated as hedging instruments $ 115,925 $ 548 $ 2,267 Total liability derivatives $ 192,794 $ 1,028 $ 2,605 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, 2017 and 2016 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 ) $ (208 ) $ (385 ) Total derivatives in hedging relationships $ (208 ) $ (385 ) Derivatives not designated as hedging instruments Forward loan sales commitments Income from Mortgage (257 ) 0 TBA mortgage-backed securities Income from Mortgage 123 0 Interest rate lock commitments Income from Mortgage (4,484 ) 0 Total derivatives not designated as hedging instruments $ (4,618 ) $ 0 Total derivatives $ (4,826 ) $ (385 ) 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 ) $ (648 ) $ 353 Cash Flow Hedges: Forward loan sales commitments Other income 0 0 Total derivatives in hedging relationships $ (648 ) $ 353 Derivatives not designated as hedging instruments Forward loan sales commitments Income from Mortgage (427 ) 0 TBA mortgage-backed securities Income from Mortgage 2,907 0 Interest rate lock commitments Income from Mortgage (3,465 ) 0 Total derivatives not designated as hedging instruments $ (985 ) $ 0 Total derivatives $ (1,633 ) $ 353

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2017
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. Assets and Liabilities Measured at Fair Value on a Recurring Basis 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 bid-ask available-for-sale spread, priority of claims, principal and interest. Discount margins used in the valuation at September 30, 2017 ranged from LIBOR plus 3.25% to LIBOR plus 6.00%. Management completed a sensitivity analysis on the fair value of its Trup Cdos. Given a comprehensive 200 basis point increase in the discount rates, the total fair value of these securities would decline by approximately 18%, or $5,741. 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” which is measured using valuations from investors for loans with similar characteristics adjusted for the Company’s actual sales experience versus the investor’s indicated pricing. These valuations fall into the Level 3 category. The unobservable input is the Company’s historical sales prices. The range of historical sales prices increased the investor’s indicated pricing by a range of 0.27% to 0.40% with a weighted average increase of 0.36%. 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, 2017 and December 31, 2016, segregated by the level of the valuation inputs within the fair value hierarchy. Fair Value at September 30, 2017 Using Description Balance as of September 30, 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 $ 115,866 $ 0 $ 115,866 $ 0 State and political subdivisions 305,141 0 305,141 0 Residential mortgage-backed securities Agency 714,700 0 714,700 0 Non-agency 5,846 0 5,846 0 Commercial mortgage-backed securities Agency 420,792 0 420,792 0 Asset-backed securities 13,429 0 13,429 0 Trust preferred collateralized debt obligations 31,659 0 0 31,659 Single issue trust preferred securities 12,467 0 12,467 0 Other corporate securities 19,254 0 19,254 0 Total available for sale debt securities 1,639,154 0 1,607,495 31,659 Available for sale equity securities: Financial services industry 3,016 401 2,615 0 Equity mutual funds (1) 6,250 6,250 0 0 Other equity securities 1,214 1,214 0 0 Total available for sale equity securities 10,480 7,865 2,615 0 Total available for sale securities 1,649,634 7,865 1,610,110 31,659 Loans held for sale 311,186 0 0 311,186 Derivative financial assets: Interest rate swap contracts 40 0 40 0 Interest rate lock commitments 7,027 0 0 7,027 TBA mortgage-backed securities 501 501 0 0 Total derivative financial assets 7,568 501 40 7,027 Liabilities Derivative financial liabilities: Interest rate swap contracts 480 0 480 0 Forward sales commitments 257 0 257 0 Interest rate lock commitments 291 0 291 0 Total derivative financial liabilities 1,028 0 1,028 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, 2016 Using Description Balance as of December 31, 2016 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets Available for sale debt securities: U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 95,786 $ 0 $ 95,786 $ 0 State and political subdivisions 192,812 0 192,812 0 Residential mortgage-backed securities Agency 584,096 0 584,096 0 Non-agency 7,043 0 7,043 0 Asset-backed securities 217 0 217 0 Commercial mortgage-backed securities Agency 305,341 0 305,341 0 Trust preferred collateralized debt obligations 33,552 0 0 33,552 Single issue trust preferred securities 11,477 0 11,477 0 Other corporate securities 15,062 0 15,062 0 Total available for sale debt securities 1,245,386 0 1,211,834 33,552 Available for sale equity securities: Financial services industry 10,735 1,372 9,363 0 Equity mutual funds (1) 1,820 1,820 0 0 Other equity securities 1,273 1,273 0 0 Total available for sale equity securities 13,828 4,465 9,363 0 Total available for sale securities 1,259,214 4,465 1,221,197 33,552 Derivative financial assets: Interest rate swap contracts 2,291 0 2,291 0 Liabilities Derivative financial liabilities: Interest rate swap contracts 2,605 0 2,605 0 (1) The equity mutual funds are within a rabbi trust for the payment of benefits under a deferred compensation plan for certain key officers of United and its subsidiaries. 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, 2017 and the year ended December 31, 2016. The following table presents additional information about financial assets and liabilities measured at fair value at September 30, 2017 and December 31, 2016 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, 2017 December 31, Balance, beginning of period $ 33,552 $ 34,686 Total gains or losses (realized/unrealized): Included in earnings (or changes in net assets) 9 0 Included in other comprehensive income 6,148 (1,134 ) Sales (8,050 ) 0 Balance, end of period $ 31,659 $ 33,552 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, 2017 December 31, Balance, beginning of period $ 0 $ 0 Acquired in Cardinal merger 271,301 0 Originations 1,644,943 0 Sales (1,639,737 ) 0 Total gains or losses during the period recognized in earnings 41,929 0 Transfers in and/or out of Level 3 (7,250 ) 0 Balance, end of period $ 311,186 $ 0 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, 2017 December 31, Balance, beginning of period $ 0 $ 0 Acquired in Cardinal merger 10,393 0 Transfers other (3,366 ) 0 Balance, end of period $ 7,027 $ 0 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 Ended September 30, 2017 Nine Months Ended September 30, 2017 Assets Loans held for sale Income from mortgage banking activities $ (5,090 ) $ (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, 2017 December 31, 2016 Description Unpaid Fair Value Fair Value Unpaid Fair Fair Value Assets Loans held for sale $ 303,953 $ 311,186 $ 7,233 $ 0 $ 0 $ 0 Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis The following describes the valuation techniques used by United to measure certain financial assets recorded at fair value on a nonrecurring basis in the financial statements. Loans held for sale Impaired Loans OREO: bi-annual Intangible Assets: The following table summarizes United’s financial assets that were measured at fair value on a nonrecurring basis during the period: Carrying value at September 30, 2017 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) YTD Losses Assets Impaired Loans $ 105,900 $ 0 $ 74,852 $ 31,048 $ 9,045 OREO 26,826 0 26,743 83 2,904 Carrying value at December 31, 2016 Description Balance as of December 31, 2016 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) YTD Losses Assets Impaired Loans $ 80,505 $ 0 $ 27,609 $ 52,896 $ 5,119 OREO 31,510 0 31,510 0 2,086 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 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, 2017 Cash and cash equivalents $ 1,747,037 $ 1,747,037 $ 0 $ 1,747,037 $ 0 Securities available for sale 1,649,634 1,649,634 7,865 1,610,110 31,659 Securities held to maturity 20,335 19,909 0 16,889 3,020 Other securities 166,756 158,418 0 0 158,418 Loans held for sale 315,031 315,031 0 3,845 311,186 Loans 13,065,542 12,550,352 0 0 12,550,352 Derivative financial assets 7,568 7,568 501 40 7,027 Deposits 13,875,297 13,859,205 0 13,859,205 0 Short-term borrowings 492,036 492,036 0 492,036 0 Long-term borrowings 1,364,246 1,328,753 0 1,328,753 0 Derivative financial liabilities 1,028 1,028 0 1,028 0 December 31, 2016 Cash and cash equivalents $ 1,434,527 $ 1,434,527 $ 0 $ 1,434,527 $ 0 Securities available for sale 1,259,214 1,259,214 4,465 1,221,197 33,552 Securities held to maturity 33,258 31,178 0 28,158 3,020 Other securities 111,166 105,608 0 0 105,608 Loans held for sale 8,445 8,445 0 8,445 0 Loans 10,268,366 10,122,486 0 0 10,122,486 Derivative financial assets 2,291 2,291 0 2,291 0 Deposits 10,796,867 10,785,294 0 10,785,294 0 Short-term borrowings 209,551 209,551 0 209,551 0 Long-term borrowings 1,172,026 1,142,782 0 1,142,782 0 Derivative financial liabilities 2,605 2,605 0 2,605 0

Stock Based Compensation

Stock Based Compensation	9 Months Ended
	Sep. 30, 2017
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 and replaced the 2011 Long-Term Incentive Plan (2011 LTI Plan) which expired during the second quarter of 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 $909 and $2,589 related to the nonvested awards under United’s Long-Term Incentive Plans was incurred for the third quarter and first nine months of 2017, respectively, as compared to the compensation expense of $720 and $2,050 related to the nonvested awards under United’s Long-Term Incentive Plans incurred for the third quarter and first nine months of 2016, 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, 2017, and the changes during the first nine months of 2017 are presented below: Nine Months Ended September 30, 2017 Weighted Average Shares Aggregate Remaining Exercise Outstanding at January 1, 2017 1,411,735 $ 28.05 Assumed in Cardinal merger 153,602 21.47 Granted 253,417 45.27 Exercised (163,562 ) 20.93 Forfeited or expired (2,962 ) 38.81 Outstanding at September 30, 2017 1,652,230 $ 12,602 5.8 $ 30.76 Exercisable at September 30, 2017 1,138,309 $ 11,964 4.5 $ 26.64 The following table summarizes the status of United’s nonvested stock option awards during the first nine months of 2017: Shares Weighted-Average Nonvested at January 1, 2017 430,278 $ 6.84 Granted 253,417 8.85 Vested (168,274 ) 6.64 Forfeited or expired (1,500 ) 8.85 Nonvested at September 30, 2017 513,921 $ 7.89 During the nine months ended September 30, 2017 and 2016, 163,562 and 248,677 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, 2017 and 2016 were issued from authorized and unissued stock. The total intrinsic value of options exercised under the Plans during the nine months ended September 30, 2017 and 2016 was $3,078 and $4,670 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, 2017: Number of Weighted-Average Outstanding at January 1, 2017 137,268 $ 33.61 Granted 89,475 45.27 Vested (53,950 ) 32.23 Forfeited (420 ) 45.30 Outstanding at September 30, 2017 172,373 $ 40.07

Employee Benefit Plans

Employee Benefit Plans	9 Months Ended
	Sep. 30, 2017
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 third quarter of 2017, United made a discretionary contribution of $10,000 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. As of December 31, 2016, United changed the method used to estimate the interest cost component of net periodic benefit cost for the Plan. Under the previous method, appropriate spot rates were used to discount the projected benefit obligation (PBO) cash flows based on date of measurement. Then, a single aggregated discount rate was calculated such that the present value of the PBO remained the same. This rate is technically a weighted-average of the spot rates. This single discount rate was applied to the interest and service costs as well. Under the full yield curve approach, separate discount rates are used to calculate the present value for each projected cash flow. This does not have any impact on the present value of the PBO as the PBO was originally discounted with spot rates. The adoption of this method concerns the manner in which it affects interest and service costs. This new method constitutes a change in an accounting estimate under the provisions of ASC topic 250, “Accounting Changes and Error Corrections,” that is inseparable from a change in accounting principle and was accounted for prospectively, with the resulting change impacting the recognition of net periodic pension cost beginning January 1, 2017. The impact of this accounting change on United’s net periodic pension cost for the third quarter and first nine months of 2017 was a decline of $252 and $748, respectively, in expense from the amount that would have been recorded under the previous method. Included in accumulated other comprehensive income at December 31, 2016 are unrecognized actuarial losses of $53,991 ($34,014 net of tax) that have not yet been recognized in net periodic pension cost. The amortization of this item expected to be recognized in net periodic pension cost during the fiscal year ended December 31, 2017 is $4,411 ($2,779 net of tax). Net periodic pension cost for the three and nine months ended September 30, 2017 and 2016 included the following components: Three Months Ended September 30 Nine Months Ended September 30 2017 2016 2017 2016 Service cost $ 574 $ 614 $ 1,705 $ 1,829 Interest cost 1,293 1,471 3,837 4,383 Expected return on plan assets (2,072 ) (2,034 ) (6,148 ) (6,058 ) Recognized net actuarial loss 1,111 1,161 3,298 3,458 Net periodic pension (benefit) cost $ 906 $ 1,212 $ 2,692 $ 3,612 Weighted-Average Assumptions: Discount rate 4.49 % 4.75 % 4.49 % 4.75 % Expected return on assets 7.00 % 7.25 % 7.00 % 7.25 % 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, 2017
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, 2017, United has provided a liability for $2,405 of unrecognized tax benefits related to various federal and state income tax matters. The entire amount of unrecognized tax benefits, if recognized, would impact United’s effective tax rate. Over the next 12 months, the statute of limitations will close on certain income tax periods. However, at this time, United cannot reasonably estimate the amount of tax benefits it may recognize over the next 12 months. United is currently open to audit under the statute of limitations by the Internal Revenue Service for the years ended December 31, 2014, 2015 and 2016 and certain State Taxing authorities for the years ended December 31, 2014 through 2016. As of September 30, 2017 and 2016, the total amount of accrued interest related to uncertain tax positions was $548 and $792, respectively. United accounts for interest and penalties related to uncertain tax positions as part of its provision for federal and state income taxes.

Comprehensive Income

Comprehensive Income	9 Months Ended
	Sep. 30, 2017
Equity [Abstract]
Comprehensive Income	16. COMPREHENSIVE INCOME The components of total comprehensive income for the three and nine months ended September 30, 2017 and 2016 are as follows: Three Months Ended Nine Months Ended 2017 2016 2017 2016 Net Income $ 56,738 $ 41,479 $ 132,606 $ 107,977 Available for sale (“AFS”) securities: AFS securities with OTTI charges during the period 0 0 (60 ) (77 ) Related income tax effect 0 0 22 28 Less: OTTI charges recognized in net income 0 0 60 33 Related income tax benefit 0 0 (22 ) (12 ) Reclassification of previous noncredit OTTI to credit OTTI 0 0 0 415 Related income tax benefit 0 0 0 (150 ) Net unrealized (losses) gains on AFS securities with OTTI 0 0 0 237 AFS securities – all other: Change in net unrealized gain on AFS securities arising during the period 3,584 (7,599 ) 14,846 12,356 Related income tax effect (1,326 ) 2,735 (5,493 ) (4,489 ) Net reclassification adjustment for (gains) losses included in net income (467 ) (1 ) (1,444 ) (251 ) Related income tax expense (benefit) 173 0 534 91 1,964 (4,865 ) 8,443 7,707 Net effect of AFS securities on other comprehensive income 1,964 (4,865 ) 8,443 7,944 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 1,111 1,161 3,298 3,458 Related income tax benefit (394 ) (384 ) (1,191 ) (1,223 ) Net effect of change in pension plan asset on other 717 777 2,107 2,235 Total change in other comprehensive income 2,683 (4,086 ) 10,554 10,183 Total Comprehensive Income $ 59,421 $ 37,393 $ 143,160 $ 118,160 The components of accumulated other comprehensive income for the nine months ended September 30, 2017 are as follows: Changes in Accumulated Other Comprehensive Income (AOCI) by Component (a) For the Nine Months Ended September 30, 2017 Unrealized Accretion on Defined Items Total Balance at January 1, 2017 ($ 10,297 ) ($ 51 ) ($ 34,369 ) ($ 44,717 ) Other comprehensive income before reclassification 9,353 4 0 9,357 Amounts reclassified from accumulated other comprehensive income (910 ) 0 2,107 1,197 Net current-period other comprehensive income, net of tax 8,443 4 2,107 10,554 Balance at September 30, 2017 ($ 1,854 ) ($ 47 ) ($ 32,262 ) ($ 34,163 ) Reclassifications out of Accumulated Other Comprehensive Income (AOCI) For the Nine Months Ended September 30, 2017 Details about AOCI Components Amount Affected Line Item in the Statement Where Net Income is Presented Available for sale (“AFS”) securities: Reclassification of previous noncredit OTTI $ 0 Total other-than-temporary impairment losses Net reclassification adjustment for losses (1,444 ) Net gains on sales/calls of investment securities (1,444 ) Total before tax Related income tax effect 534 Tax expense (910 ) Net of tax Pension plan: Recognized net actuarial loss 3,298 (a) 3,298 Total before tax Related income tax effect (1,191 ) Tax expense 2,107 Net of tax Total reclassifications for the period $ 1,197 (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, 2017
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 2017 2016 2017 2016 Distributed earnings allocated to common stock $ 34,587 $ 25,174 $ 95,871 $ 73,242 Undistributed earnings allocated to common stock 22,065 16,234 36,518 34,545 Net earnings allocated to common shareholders $ 56,652 $ 41,408 $ 132,389 $ 107,787 Average common shares outstanding 104,760,153 76,218,573 95,040,664 72,413,246 Equivalents from stock options 307,969 429,200 409,962 333,117 Average diluted shares outstanding 105,068,122 76,647,773 95,450,626 72,746,363 Earnings per basic common share $ 0.54 $ 0.54 $ 1.39 $ 1.49 Earnings per diluted common share $ 0.54 $ 0.54 $ 1.39 $ 1.48

Variable Interest Entities

Variable Interest Entities	9 Months Ended
	Sep. 30, 2017
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 fifteen 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 Century Trust March 23, 2000 $ 8,800 10.875% Fixed March 8, 2030 United Statutory Trust III December 17, 2003 $ 20,000 3-month December 17, 2033 United Statutory Trust IV December 19, 2003 $ 25,000 3-month January 23, 2034 United Statutory Trust V July 12, 2007 $ 50,000 3-month October 1, 2037 United Statutory Trust VI September 20, 2007 $ 30,000 3-month December 15, 2037 Premier Statutory Trust II September 25, 2003 $ 6,000 3-month October 8, 2033 Premier Statutory Trust III May 16, 2005 $ 8,000 3-month June 15, 2035 Premier Statutory Trust IV June 20, 2006 $ 14,000 3-month September 23, 2036 Premier Statutory Trust V December 14, 2006 $ 10,000 3-month March 1, 2037 Centra Statutory Trust I September 20, 2004 $ 10,000 3-month September 20, 2034 Centra Statutory Trust II June 15, 2006 $ 10,000 3-month July 7, 2036 Virginia Commerce Trust II December 19, 2002 $ 15,000 6-month December 19, 2032 Virginia Commerce Trust III December 20, 2005 $ 25,000 3-month February 23, 2036 Cardinal Statutory Trust I July 27, 2004 $ 20,000 3-month September 15, 2034 UFBC Capital Trust I December 30, 2004 $ 5,000 3-month March 15, 2035 United, through its banking subsidiaries, also makes limited partner equity investments in various low income housing and community development partnerships sponsored by independent third-parties. United invests in these partnerships to either realize tax credits on its consolidated federal income tax return or for purposes of earning a return on its investment. These partnerships are considered VIEs as the limited partners lack a controlling financial interest in the entities through their inability to make decisions that have a significant effect on the operations and success of the partnerships. United’s limited partner interests in these entities is immaterial, however; these partnerships are not consolidated as United is not deemed to be the primary beneficiary. The following table summarizes quantitative information about United’s significant involvement in unconsolidated VIEs: As of September 30, 2017 As of December 31, 2016 Aggregate Assets Aggregate Liabilities Risk Of Loss (1) Aggregate Assets Aggregate Liabilities Risk Of Loss (1) Trust preferred securities $ 266,560 $ 257,605 $ 8,955 $ 240,668 $ 232,583 $ 8,085 (1) Represents investment in VIEs.

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 2017
Segment Reporting [Abstract]
Segment Information	19. SEGMENT INFORMATION As a result of the Cardinal acquisition, United now operates in two business segments: community banking and mortgage banking. Prior to the Cardinal acquisition, United’s business activities were confined to just one reportable segment of community banking. Through its community banking segment, United offers a full range of products and services through various delivery channels. In particular, the community banking segment includes both commercial and consumer lending and provides customers with such products as commercial loans, real estate loans, business financing and consumer loans. In addition, this segment provides customers with several choices of deposit products including demand deposit accounts, savings accounts and certificates of deposit as well as investment and financial advisory services to businesses and individuals, including financial planning, retirement/estate planning, and investment management. The mortgage banking segment engages primarily in the origination and acquisition of residential mortgages for sale into the secondary market though George Mason. The community banking segment provides the mortgage banking segment (George Mason) with short-term funds to originate mortgage loans through a warehouse line of credit and charges the mortgage banking segment interest based on the prime rate. These transactions are eliminated in the consolidation process. The Company does not have any operating segments other than those reported. The “Other” category consists of financial information not directly attributable to a specific segment, including interest income from investments and net securities gains or losses of parent companies and their non-banking non-segment Information about the reportable segments and reconciliation of this information to the consolidated financial statements at and for the three and nine months ended September 30, 2017 and 2016 is as follows: At and For the Three Months Ended September 30, 2017 Community Mortgage Other Consolidated Net interest income $ 152,886 $ (36 ) $ (2,574 ) $ 150,276 Provision for loans losses 7,279 0 0 7,279 Other income 18,373 19,936 (80 ) 38,229 Other expense 74,553 24,036 (1,937 ) 96,652 Income taxes 29,490 (1,332 ) (322 ) 27,836 Net income (loss) $ 59,937 $ (2,804 ) $ (395 ) $ 56,738 Total assets (liabilities) $ 18,780,395 $ 350,483 $ (900 ) $ 19,129,978 Average assets (liabilities) 18,620,035 321,744 (13,994 ) 18,927,785 At and For the Three Months Ended September 30, 2016 Community Other Consolidated Net interest income $ 113,033 $ (1,964 ) $ 111,069 Provision for loans losses 6,988 0 6,988 Other income 19,666 (645 ) 19,021 Other expense 63,009 (232 ) 62,777 Income taxes 19,729 (883 ) 18,846 Net income (loss) $ 42,973 $ (1,494 ) $ 41,479 Total assets (liabilities) $ 14,364,797 $ (20,101 ) $ 14,344,696 Average assets (liabilities) 14,182,202 (22,633 ) 14,159,569 At and For the Nine Months Ended September 30, 2017 Community Mortgage Other Consolidated Net interest income $ 401,044 $ 54 $ (6,957 ) $ 394,141 Provision for loans losses 21,429 0 0 21,429 Other income 53,409 42,329 3,143 98,881 Other expense 215,935 42,744 12,952 271,631 Income taxes 73,214 (39 ) (5,819 ) 67,356 Net income (loss) $ 143,875 $ (322 ) $ (10,947 ) $ 132,606 Total assets (liabilities) $ 18,780,395 $ 350,483 $ (900 ) $ 19,129,978 Average assets (liabilities) 17,020,928 187,118 (20,402 ) 17,187,644 At and For the Nine Months Ended September 30, 2016 Community Other Consolidated Net interest income $ 317,835 $ (5,757 ) $ 312,078 Provision for loans losses 18,690 0 18,690 Other income 55,323 (1,943 ) 53,380 Other expense 186,322 (634 ) 185,688 Income taxes 55,580 (2,477 ) 53,103 Net income (loss) $ 112,566 $ (4,589 ) $ 107,977 Total assets (liabilities) $ 14,364,797 $ (20,101 ) $ 14,344,696 Average assets (liabilities) 13,125,973 (21,575 ) 13,104,398

Summary of Significant Accoun28

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2017
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 considers all of its principal business activities to be bank related. All significant intercompany accounts and transactions have been eliminated in the consolidated financial statements. Dollars are in thousands, except per share or unless otherwise noted.
New Accounting Standards	New Accounting Standards 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, modifications. Companies will apply the modification accounting guidance if the value, vesting conditions or classification of the award changes. The new guidance should reduce diversity in practice and result in fewer changes to the terms of an award being accounted for as modifications, as the guidance will allow companies to make certain non-substantive No. 2017-09 No. 2017-09 In March 2017, the FASB issued ASU 2017-07, 2017-07 2017-07 In January 2017, the FASB issued ASU 2017-04, 2017-04 2017-04 In January 2017, the FASB issued ASU 2017-01, 2017-01 2017-01 In August 2016, the FASB issued ASU 2016-15, 2016-15 2016-15 2016-15 In June 2016, the FASB issued ASU 2016-13, 2016-13 available-for-sale 2016-13 period in which the guidance is effective. ASU 2016-13 In March 2016, the FASB issued ASU 2016-09, 2016-09 2016-09 2016-09 2016-09 tax-related 2016-09 In February 2016, the FASB issued ASU 2016-02, 2016-02 2016-02 right-of-use 2016-02 In January 2016, the FASB issued ASU 2016-01, 2016-01 2016-01 available-for-sale 2016-01 In May 2014, the FASB issued ASU 2014-09, 2014-09 2014-09 2014-09 2014-09
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, 2017
Schedule of Acquired Loans Accounted for at Fair Value	In conjunction with the Cardinal merger, the acquired loan portfolio was accounted for at fair value as follows: April 21, 2017 Contractually required principal and interest at acquisition $ 4,211,734 Contractual cash flows not expected to be collected (56,176 ) Expected cash flows at acquisition 4,155,558 Interest component of expected cash flows (986,959 ) Basis in acquired loans at acquisition – estimated fair value $ 3,168,599
Schedule of Fair Value of Acquired Identifiable Assets and Liabilities Assumed	The consideration paid for Bank of Georgetown’s common equity and the fair value of acquired identifiable assets and liabilities assumed as of the BOG Acquisition Date were as follows: Purchase price: Value of common shares issued (6,527,746 shares) $ 253,799 Fair value of stock options assumed 10,696 Cash for fractional shares 10 Total purchase price 264,505 Identifiable assets: Cash and cash equivalents 29,340 Investment securities 219,783 Loans 966,870 Premises and equipment 5,574 Core deposit intangibles 9,058 Other assets 31,605 Total identifiable assets $ 1,262,230 Identifiable liabilities: Deposits $ 971,685 Short-term borrowings 101,021 Long-term borrowings 67,659 Other liabilities 11,532 Total identifiable liabilities 1,151,897 Fair value of net assets acquired including identifiable intangible assets 110,333 Resulting goodwill $ 154,172
Cardinal Financial Corporation [Member]
Schedule of Acquired Loans Accounted for at Fair Value	In conjunction with the Bank of Georgetown merger, the acquired loan portfolio was accounted for at fair value as follows: June 3, 2016 Contractually required principal and interest at acquisition $ 1,275,398 Contractual cash flows not expected to be collected (33,980 ) Expected cash flows at acquisition 1,241,418 Interest component of expected cash flows (274,548 ) Basis in acquired loans at acquisition – estimated fair value $ 966,870
Schedule of Fair Value of Acquired Identifiable Assets and Liabilities Assumed	The consideration paid for Cardinal’s common equity and the preliminary amounts of acquired identifiable assets and liabilities assumed as of the Cardinal Acquisition Date were as follows: Purchase price: Value of common shares issued (23,690,589 shares) $ 972,499 Fair value of stock options assumed 2,741 Cash for fractional shares 14 Total purchase price 975,254 Identifiable assets: Cash and cash equivalents 44,545 Investment securities 395,829 Loans held for sale 271,301 Loans 3,168,599 Premises and equipment 24,208 Core deposit intangibles 28,723 George Mason trade name intangible 1,230 Other assets 135,383 Total identifiable assets $ 4,069,818 Identifiable liabilities: Deposits $ 3,349,812 Short-term borrowings 96,215 Long-term borrowings 220,119 Unfavorable lease liability 2,281 Other liabilities 48,650 Total identifiable liabilities 3,717,077 Preliminary fair value of net assets acquired including identifiable intangible assets 352,741 Preliminary resulting goodwill $ 622,513
Schedule of Business Acquisition Pro Forma Information	The following table presents certain unaudited pro forma information for the results of operations for the nine months ended September 30, 2017 and 2016, as if the Cardinal merger had occurred on January 1, 2017 and 2016, respectively. Proforma Nine Months Ended September 30 2017 2016 Total Revenues (1) $ 573,790 $ 585,223 Net Income 136,104 160,731 (1) Represents net interest income plus other income

Investment Securities (Tables)

Investment Securities (Tables)	9 Months Ended
	Sep. 30, 2017
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, 2017 Gross Gross Estimated Cumulative Amortized Unrealized Unrealized Fair OTTI in Cost Gains Losses Value AOCI (1) U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 115,224 $ 864 $ 222 $ 115,866 $ 0 State and political subdivisions 305,096 2,567 2,522 305,141 0 Residential mortgage-backed securities Agency 715,003 3,819 4,122 714,700 0 Non-agency 5,259 587 0 5,846 86 Commercial mortgage-backed securities Agency 420,115 2,081 1,404 420,792 0 Asset-backed securities 13,422 10 3 13,429 0 Trust preferred collateralized debt obligations 38,186 317 6,844 31,659 20,770 Single issue trust preferred securities 13,404 404 1,341 12,467 0 Other corporate securities 18,998 256 0 19,254 0 Marketable equity securities 9,950 541 11 10,480 0 Total $ 1,654,657 $ 11,446 $ 16,469 $ 1,649,634 $ 20,856 December 31, 2016 Gross Gross Estimated Cumulative Amortized Unrealized Unrealized Fair OTTI in Cost Gains Losses Value AOCI (1) U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 95,247 $ 698 $ 159 $ 95,786 $ 0 State and political subdivisions 196,350 1,364 4,902 192,812 0 Residential mortgage-backed securities Agency 585,208 3,999 5,111 584,096 0 Non-agency 6,629 426 12 7,043 86 Commercial mortgage-backed securities Agency 304,635 1,948 1,242 305,341 0 Asset-backed securities 217 0 0 217 0 Trust preferred collateralized debt obligations 48,558 729 15,735 33,552 25,952 Single issue trust preferred securities 13,363 284 2,170 11,477 0 Other corporate securities 14,996 66 0 15,062 0 Marketable equity securities 12,436 1,398 6 13,828 0 Total $ 1,277,639 $ 10,912 $ 29,337 $ 1,259,214 $ 26,038 (1) Non-credit before-tax.
Summary of Securities Available for Sale in an Unrealized Loss Position	The following is a summary of securities available-for-sale Less than 12 months 12 months or longer Fair Unrealized Fair Unrealized Value Losses Value Losses September 30, 2017 U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 27,053 $ 128 $ 19,932 $ 94 State and political subdivisions 83,310 896 38,004 1,626 Residential mortgage-backed securities Agency 351,936 3,410 31,690 712 Non-agency 0 0 0 0 Commercial mortgage-backed securities Agency 228,307 1,218 12,272 186 Asset-backed securities 6,760 3 0 0 Trust preferred collateralized debt obligations 0 0 29,544 6,844 Single issue trust preferred securities 0 0 4,365 1,341 Marketable equity securities 0 0 352 11 Total $ 697,366 $ 5,655 $ 136,159 $ 10,814 Less than 12 months 12 months or longer Fair Unrealized Fair Unrealized Value Losses Value Losses December 31, 2016 U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 24,101 $ 159 $ 0 $ 0 State and political subdivisions 116,300 4,902 0 0 Residential mortgage-backed securities Agency 309,376 5,111 0 0 Non-agency 0 0 218 12 Commercial mortgage-backed securities Agency 162,479 1,242 0 0 Asset-backed securities 0 0 0 0 Trust preferred collateralized debt obligations 0 0 28,579 15,735 Single issue trust preferred securities 0 0 8,185 2,170 Marketable equity securities 357 6 0 0 Total $ 612,613 $ 11,420 $ 36,982 $ 17,917
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 2017 2016 2017 2016 Proceeds from sales and calls $ 64,257 $ 174,015 $ 631,561 $ 368,246 Gross realized gains 1,781 3 2,840 259 Gross realized losses 1,314 1 1,396 7
Summary of Unrealized Loss Positions of Available for Sale TRUP CDOs and Single Issue Trust Preferred Securities	The following is a summary of the available for sale Trup Cdos as of September 30, 2017: Amortized Cost Class Amortized Cost Fair Value Unrealized Loss Investment Split Below Senior – Bank $ 5,208 $ 5,287 $ (79 ) $ 3,410 $ 0 $ 1,798 Mezzanine – Bank (now in senior position) 6,428 5,518 910 0 0 6,428 Mezzanine – Bank 22,656 17,918 4,738 0 0 22,656 Mezzanine – Bank & Insurance (combination) 3,894 2,936 958 0 0 3,894 Totals $ 38,186 $ 31,659 $ 6,527 $ 3,410 $ 0 $ 34,776
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 2017 2016 2017 2016 Balance of cumulative credit losses at beginning of period $ 22,162 $ 22,162 $ 22,162 $ 23,773 Additional credit losses on securities for which OTTI was previously recognized 0 0 0 33 Reductions during the period for securities for which the amount previously recognized in other comprehensive income was recognized in earnings (4,102 ) 0 (4,102 ) (1,644 ) Balance of cumulative credit losses at end of period $ 18,060 $ 22,162 $ 18,060 $ 22,162
Summary of Amortized Cost and Estimated Fair Values of Securities Held to Maturity	The amortized cost and estimated fair values of securities held to maturity are summarized as follows: September 30, 2017 Gross Gross Estimated Amortized Unrealized Unrealized Fair Cost Gains Losses Value U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 5,215 $ 400 $ 0 $ 5,615 State and political subdivisions 5,674 12 0 5,686 Residential mortgage-backed securities Agency 26 4 0 30 Single issue trust preferred securities 9,400 0 842 8,558 Other corporate securities 20 0 0 20 Total $ 20,335 $ 416 $ 842 $ 19,909 December 31, 2016 Gross Gross Estimated Amortized Unrealized Unrealized Fair Cost Gains Losses Value U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 5,295 $ 570 $ 0 $ 5,865 State and political subdivisions 8,598 17 0 8,615 Residential mortgage-backed securities Agency 30 5 0 35 Single issue trust preferred securities 19,315 0 2,672 16,643 Other corporate securities 20 0 0 20 Total $ 33,258 $ 592 $ 2,672 $ 31,178
Available-for-sale Securities [Member]
Summary of Maturities of Debt Securities Held to Maturity by Amortized Cost and Estimated Fair Value	The amortized cost and estimated fair value of securities available for sale at September 30, 2017 and December 31, 2016 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, 2017 December 31, 2016 Estimated Estimated Amortized Fair Amortized Fair Cost Value Cost Value Due in one year or less $ 57,720 $ 57,622 $ 53,286 $ 53,330 Due after one year through five years 370,020 371,007 296,181 297,385 Due after five years through ten years 342,176 343,326 213,094 213,791 Due after ten years 874,791 867,199 702,642 680,880 Marketable equity securities 9,950 10,480 12,436 13,828 Total $ 1,654,657 $ 1,649,634 $ 1,277,639 $ 1,259,214
Held-to-maturity Securities [Member]
Summary of Maturities of Debt Securities Held to Maturity by Amortized Cost and Estimated Fair Value	The amortized cost and estimated fair value of debt securities held to maturity at September 30, 2017 and December 31, 2016 by contractual maturity are shown below. Expected maturities may differ from contractual maturities because the issuers may have the right to call or prepay obligations without penalties. September 30, 2017 December 31, 2016 Estimated Estimated Amortized Fair Amortized Fair Cost Value Cost Value Due in one year or less $ 0 $ 0 $ 1,040 $ 1,041 Due after one year through five years 9,189 9,600 8,268 8,850 Due after five years through ten years 5,726 5,382 3,585 3,589 Due after ten years 5,420 4,927 20,365 17,698 Total $ 20,335 $ 19,909 $ 33,258 $ 31,178

Loans (Tables)

Loans (Tables)	9 Months Ended
	Sep. 30, 2017
Receivables [Abstract]
Major Classes of Loans	Major classes of loans are as follows: September 30, 2017 December 31, Commercial, financial and agricultural: Owner-occupied commercial real estate $ 1,364,757 $ 1,049,885 Nonowner-occupied commercial real estate 4,686,183 3,425,453 Other commercial loans 1,757,741 1,613,437 Total commercial, financial & agricultural 7,808,681 6,088,775 Residential real estate 3,050,868 2,403,437 Construction & land development 1,599,632 1,255,738 Consumer: Bankcard 13,775 14,187 Other consumer 683,898 594,582 Total gross loans $ 13,156,854 $ 10,356,719
Activity for Accretable Yield	Activity for the accretable yield for the first nine months of 2017 follows: Accretable yield at the beginning of the period $ 29,165 Accretion (including cash recoveries) (11,312 ) Additions 17,444 Net reclassifications to accretable from non-accretable 2,727 Disposals (including maturities, foreclosures, and charge-offs) (2,367 ) Accretable yield at the end of the period $ 35,657

Credit Quality (Tables)

Credit Quality (Tables)	9 Months Ended
	Sep. 30, 2017
Text Block [Abstract]
Schedule of Troubled Debt Restructurings, Segregated by Class of Loans	The following table sets forth United’s troubled debt restructurings that were restructured during the three months ended September 30, 2016, segregated by class of loans: Troubled Debt Restructurings For the Three Months Ended September 30, 2016 Number of Pre- Modification Post- Commercial real estate: Owner-occupied 0 $ 0 $ 0 Nonowner-occupied 0 0 0 Other commercial 1 110 110 Residential real estate 0 0 0 Construction & land development 0 0 0 Consumer: Bankcard 0 0 0 Other consumer 0 0 0 Total 1 $ 110 $ 110 The following table sets forth United’s troubled debt restructurings that were restructured during the nine months ended September 30, 2017 and 2016, segregated by class of loans: Troubled Debt Restructurings For the Nine Months Ended September 30, 2017 September 30, 2016 Number of Pre- Modification Outstanding Recorded Investment Post- Modification Outstanding Recorded Investment Number of Contracts Pre- Modification Outstanding Recorded Investment Post- Modification Outstanding Recorded Investment Commercial real estate: Owner-occupied 1 $ 5,333 $ 5,333 1 $ 1,190 $ 1,184 Nonowner-occupied 0 0 0 0 0 0 Other commercial 8 24,102 22,291 5 2,250 1,725 Residential real estate 0 0 0 1 1,400 1,400 Construction & land development 1 1,456 1,400 0 0 0 Consumer: Bankcard 0 0 0 0 0 0 Other consumer 0 0 0 0 0 0 Total 10 $ 30,891 $ 29,024 7 $ 4,840 $ 4,309
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, 2017. Three Months Ended September 30, 2017 Nine Months Ended September 30, 2017 (In thousands) Number of Recorded Number of Recorded Troubled Debt Restructurings Commercial real estate: Owner-occupied 0 $ 0 0 $ 0 Nonowner-occupied 0 0 0 0 Other commercial 1 1,495 1 1,495 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 $ 1,495 1 $ 1,495
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, 2017 30-89 90 Days or Total Past Current & Total Financing Recorded & Accruing Commercial real estate: Owner-occupied $ 9,704 $ 6,912 $ 16,616 $ 1,348,141 $ 1,364,757 $ 0 Nonowner-occupied 7,686 20,797 28,483 4,657,700 4,686,183 0 Other commercial 13,589 79,342 92,931 1,664,810 1,757,741 802 Residential real estate 33,654 25,564 59,218 2,991,650 3,050,868 5,298 Construction & land development 3,351 17,852 21,203 1,578,429 1,599,632 14,828 Consumer: Bankcard 385 210 595 13,180 13,775 210 Other consumer 8,087 1,305 9,392 674,506 683,898 1,111 Total $ 76,456 $ 151,982 $ 228,438 $ 12,928,416 $ 13,156,854 $ 22,249 (1) Other includes loans with a recorded investment of $227,754 acquired and accounted for under ASC topic 310-30 Age Analysis of Past Due Loans As of December 31, 2016 (In thousands) 30-89 90 Days or Total Past Current & Total Financing Recorded & Accruing Commercial real estate: Owner-occupied $ 5,850 $ 3,981 $ 9,831 $ 1,040,054 $ 1,049,885 $ 94 Nonowner-occupied 9,288 20,847 30,135 3,395,318 3,425,453 172 Other commercial 15,273 42,766 58,039 1,555,398 1,613,437 2,518 Residential real estate 29,976 25,991 55,967 2,347,470 2,403,437 4,216 Construction & land development 3,809 7,779 11,588 1,244,150 1,255,738 33 Consumer: Bankcard 422 141 563 13,624 14,187 141 Other consumer 10,015 1,712 11,727 582,855 594,582 1,412 Total $ 74,633 $ 103,217 $ 177,850 $ 10,178,869 $ 10,356,719 $ 8,586 (1) Other includes loans with a recorded investment of $171,596 acquired and accounted for under ASC topic 310-30
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, 2017 December 31, 2016 Commercial real estate: Owner-occupied $ 6,912 $ 3,887 Nonowner-occupied 20,797 20,675 Other commercial 78,540 40,248 Residential real estate 20,266 21,775 Construction & land development 3,024 7,746 Consumer: Bankcard 0 0 Other consumer 194 300 Total $ 129,733 $ 94,631
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, 2017 Commercial Real Estate Other Construction & Land Owner- Nonowner- Grade: Pass $ 1,282,657 $ 4,544,799 $ 1,611,250 $ 1,498,656 Special mention 23,827 44,080 47,450 19,872 Substandard 58,273 97,304 98,933 81,104 Doubtful 0 0 108 0 Total $ 1,364,757 $ 4,686,183 $ 1,757,741 $ 1,599,632 As of December 31, 2016 Commercial Real Estate Other Construction & Land Owner- Nonowner- Grade: Pass $ 963,503 $ 3,284,497 $ 1,463,797 $ 1,126,742 Special mention 20,490 36,462 26,537 52,327 Substandard 65,892 104,494 122,893 76,669 Doubtful 0 0 210 0 Total $ 1,049,885 $ 3,425,453 $ 1,613,437 $ 1,255,738 Credit Quality Indicators Consumer Credit Exposure As of September 30, 2017 Residential Bankcard Other Grade: Pass $ 2,999,614 $ 13,180 $ 674,447 Special mention 18,953 385 8,134 Substandard 32,301 210 1,317 Doubtful 0 0 0 Total $ 3,050,868 $ 13,775 $ 683,898 As of December 31, 2016 Residential Bankcard Other Grade: Pass $ 2,348,017 $ 13,624 $ 582,704 Special mention 18,240 422 10,132 Substandard 36,995 141 1,746 Doubtful 185 0 0 Total $ 2,403,437 $ 14,187 $ 594,582
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, 2017 December 31, 2016 Recorded Unpaid Related Recorded Unpaid Related With no related allowance recorded: Commercial real estate: Owner-occupied $ 64,592 $ 65,355 $ 0 $ 46,575 $ 47,108 $ 0 Nonowner-occupied 143,100 143,552 0 92,654 93,104 0 Other commercial 55,022 58,785 0 46,064 48,308 0 Residential real estate 20,873 22,546 0 22,747 24,404 0 Construction & land 30,959 33,225 0 19,863 21,746 0 Consumer: Bankcard 0 0 0 0 0 0 Other consumer 16 16 0 36 36 0 With an allowance recorded: Commercial real estate: Owner-occupied $ 8,220 $ 8,220 $ 923 $ 1,787 $ 2,082 $ 815 Nonowner-occupied 12,182 12,182 1,786 17,938 17,938 2,524 Other commercial 70,344 80,415 21,890 43,774 46,188 13,441 Residential real estate 13,743 15,082 1,659 12,066 12,801 3,431 Construction & land 1,411 5,910 488 4,940 7,899 3,206 Consumer: Bankcard 0 0 0 0 0 0 Other consumer 0 0 0 0 0 0 Total: Commercial real estate: Owner-occupied $ 72,812 $ 73,575 $ 923 $ 48,362 $ 49,190 $ 815 Nonowner-occupied 155,282 155,734 1,786 110,592 111,042 2,524 Other commercial 125,366 139,200 21,890 89,838 94,496 13,441 Residential real estate 34,616 37,628 1,659 34,813 37,205 3,431 Construction & land 32,370 39,135 488 24,803 29,645 3,206 Consumer: Bankcard 0 0 0 0 0 0 Other consumer 16 16 0 36 36 0 Impaired Loans For the Three Months Ended September 30, 2017 September 30, 2016 Average Interest Average Interest With no related allowance recorded: Commercial real estate: Owner-occupied $ 58,980 $ 376 $ 38,199 $ 531 Nonowner-occupied 108,959 312 71,154 321 Other commercial 57,317 306 45,028 1,221 Residential real estate 19,553 74 27,214 170 Construction & land development 23,846 552 28,730 46 Consumer: Bankcard 0 0 0 0 Other consumer 25 0 35 0 With an allowance recorded: Commercial real estate: Owner-occupied $ 11,624 $ 131 $ 3,353 $ 36 Nonowner-occupied 13,408 89 14,046 122 Other commercial 72,835 216 33,195 42 Residential real estate 15,225 16 8,579 52 Construction & land development 1,641 21 8,591 56 Consumer: Bankcard 0 0 0 0 Other consumer 0 0 0 0 Total: Commercial real estate: Owner-occupied $ 70,604 $ 507 $ 41,552 $ 567 Nonowner-occupied 122,367 401 85,200 443 Other commercial 130,152 522 78,223 1,263 Residential real estate 34,778 90 35,793 222 Construction & land development 25,487 573 37,321 102 Consumer: Bankcard 0 0 0 0 Other consumer 25 0 35 0 Impaired Loans For the Nine Months Ended September 30, 2017 September 30, 2016 Average Interest Average Interest With no related allowance recorded: Commercial real estate: Owner-occupied $ 55,506 $ 1,011 $ 34,030 $ 715 Nonowner-occupied 93,254 811 70,081 714 Other commercial 55,891 895 37,805 1,446 Residential real estate 19,634 206 26,737 406 Construction & land development 20,706 563 26,559 112 Consumer: Bankcard 0 0 0 0 Other consumer 29 0 32 0 With an allowance recorded: Commercial real estate: Owner-occupied $ 9,392 $ 424 $ 3,603 $ 92 Nonowner-occupied 14,595 363 10,416 360 Other commercial 65,142 1,410 34,755 270 Residential real estate 15,186 89 9,129 77 Construction & land development 2,872 64 10,300 146 Consumer: Bankcard 0 0 0 0 Other consumer 0 0 0 0 Total: Commercial real estate: Owner-occupied $ 64,898 $ 1,435 $ 37,633 $ 807 Nonowner-occupied 107,849 1,174 80,497 1,074 Other commercial 121,033 2,305 72,560 1,716 Residential real estate 34,820 295 35,866 483 Construction & land development 23,578 627 36,859 258 Consumer: Bankcard 0 0 0 0 Other consumer 29 0 32 0

Allowance for Credit Losses (Ta

Allowance for Credit Losses (Tables)	9 Months Ended
	Sep. 30, 2017
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, 2017 Commercial Real Estate Construction Allowance for Owner- Nonowner- Other Residential Real & Land Consumer Estimated Total Allowance for Loan Losses: Beginning balance $ 5,129 $ 7,099 $ 37,287 $ 12,479 $ 7,514 $ 2,715 $ 760 $ 72,983 Charge-offs 518 0 4,854 299 54 632 0 6,357 Recoveries 397 168 156 60 89 151 0 1,021 Provision 230 (472 ) 8,782 (1,385 ) 452 281 (609 ) 7,279 Ending balance $ 5,238 $ 6,795 $ 41,371 $ 10,855 $ 8,001 $ 2,515 $ 151 $ 74,926 Allowance for Loan Losses and Carrying Amount of Loans For the Nine Months Ended September 30, 2017 Commercial Real Estate Construction Allowance for Owner- Nonowner- Other Residential & Land Consumer Estimated Total Allowance for Loan Losses: Beginning balance $ 5,273 $ 6,883 $ 33,087 $ 13,770 $ 10,606 $ 2,805 $ 347 $ 72,771 Charge-offs 1,433 295 14,883 2,331 2,576 2,046 0 23,564 Recoveries 1,590 198 821 352 705 624 0 4,290 Provision (192 ) 9 22,346 (936 ) (734 ) 1,132 (196 ) 21,429 Ending balance $ 5,238 $ 6,795 $ 41,371 $ 10,855 $ 8,001 $ 2,515 $ 151 $ 74,926 Ending Balance: individually evaluated for impairment $ 923 $ 1,786 $ 21,890 $ 1,659 $ 488 $ 0 $ 0 $ 26,746 Ending Balance: collectively evaluated for impairment $ 4,315 $ 5,009 $ 19,481 $ 9,196 $ 7,513 $ 2,515 $ 151 $ 48,180 Ending Balance: loans acquired with deteriorated credit quality $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 Financing receivables: Ending balance $ 1,364,757 $ 4,686,183 $ 1,757,741 $ 3,050,868 $ 1,599,632 $ 697,673 $ 0 $ 13,156,854 Ending Balance: individually evaluated for impairment $ 32,888 $ 25,220 $ 89,559 $ 15,574 $ 16,879 $ 0 $ 0 $ 180,120 Ending Balance: collectively evaluated for impairment $ 1,297,668 $ 4,537,792 $ 1,636,037 $ 3,021,173 $ 1,558,653 $ 697,657 $ 0 $ 12,748,980 Ending Balance: loans acquired with deteriorated credit quality $ 34,201 $ 123,171 $ 32,145 $ 14,121 $ 24,100 $ 16 $ 0 $ 227,754 Allowance for Loan Losses and Carrying Amount of Loans For the Year Ended December 31, 2016 Commercial Real Estate Other Residential Construction Consumer Allowance Total Owner- Nonowner- & Land Estimated Allowance for Loan Losses: Beginning balance $ 3,637 $ 5,309 $ 31,328 $ 15,148 $ 18,205 $ 1,995 $ 104 $ 75,726 Charge-offs 5,281 419 20,430 4,597 2,659 2,794 0 36,180 Recoveries 3,071 675 3,452 639 433 446 0 8,716 Provision 3,846 1,318 18,737 2,580 (5,373 ) 3,158 243 24,509 Ending balance $ 5,273 $ 6,883 $ 33,087 $ 13,770 $ 10,606 $ 2,805 $ 347 $ 72,771 Ending Balance: individually evaluated for impairment $ 815 $ 2,524 $ 13,441 $ 3,431 $ 3,206 $ 0 $ 0 $ 23,417 Ending Balance: collectively evaluated for impairment $ 4,458 $ 4,359 $ 19,646 $ 10,339 $ 7,400 $ 2,805 $ 347 $ 49,354 Ending Balance: loans acquired with deteriorated credit quality $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 Financing receivables: Ending balance $ 1,049,885 $ 3,425,453 $ 1,613,437 $ 2,403,437 $ 1,255,738 $ 608,769 $ 0 $ 10,356,719 Ending Balance: individually evaluated for impairment $ 18,976 $ 26,835 $ 56,091 $ 14,766 $ 8,152 $ 0 $ 0 $ 124,820 Ending Balance: collectively evaluated for impairment $ 1,005,999 $ 3,323,117 $ 1,527,479 $ 2,373,969 $ 1,221,006 $ 608,733 $ 0 $ 10,060,303 Ending Balance: loans acquired with deteriorated credit quality $ 24,910 $ 75,501 $ 29,867 $ 14,702 $ 26,580 $ 36 $ 0 $ 171,596

Intangible Assets (Tables)

Intangible Assets (Tables)	9 Months Ended
	Sep. 30, 2017
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, 2017 Community Banking Mortgage Banking Total Gross Accumulated Gross Accumulated Gross Accumulated Amortized intangible assets: Core deposit intangible assets $ 98,358 ($ 52,062 ) $ 0 ($ 0 ) $ 98,358 ($ 52,062 ) Non-amortized George Mason trade name $ 0 $ 1,230 $ 1,230 Goodwill not subject to amortization $ 1,466,152 $ 21,455 $ 1,487,607 December 31, 2016 Community Banking Total Gross Carrying Accumulated Gross Accumulated Amortized intangible assets: Core deposit intangible assets $ 69,635 ($ 46,681 ) $ 69,635 ($ 46,681 ) Goodwill not subject to amortization $ 863,767 $ 863,767
Reconciliation of Goodwill	The following table provides a reconciliation of goodwill: Community Mortgage Total Goodwill at December 31, 2016 $ 863,767 $ 0 $ 863,767 Addition to goodwill from Bank of Georgetown acquisition 1,327 0 1,327 Preliminary addition to goodwill from Cardinal acquisition 601,058 21,455 622,513 Goodwill at September 30, 2017 $ 1,466,152 $ 21,455 $ 1,487,607
Schedule of Anticipated Amortization Expense	The following table sets forth the anticipated amortization expense for intangible assets for the years subsequent to 2016: Year Amount 2017 $ 7,772 2018 8,039 2019 7,015 2020 6,309 2021 and thereafter 22,542

Long-Term Borrowings (Tables)

Long-Term Borrowings (Tables)	9 Months Ended
	Sep. 30, 2017
Debt Disclosure [Abstract]
Schedule of Maturities of FHLB Borrowings	The scheduled maturities of these FHLB borrowings are as follows: Year Amount 2017 $ 815,000 2018 131,776 2019 187,809 2020 42,247 2021 and thereafter 95,283 Total $ 1,272,115

Derivative Financial Instrume36

Derivative Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2017
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, 2017 and December 31, 2016. Asset Derivatives September 30, 2017 December 31, 2016 Balance Sheet Location Notional Amount Fair Value Balance Sheet Location Fair Value Derivatives designated as hedging instruments Fair Value Hedges: Interest rate swap contracts (hedging commercial loans) Other assets $ 14,762 $ 40 Other assets $ 24 Total derivatives designated as hedging instruments $ 14,762 $ 40 $ 24 Derivatives not designated as hedging instruments Interest rate swap contracts Other assets $ 0 $ 0 Other assets $ 2,267 TBA mortgage-backed securities Other assets 322,500 501 Other assets 0 Interest rate lock commitments Other assets 169,588 7,027 Other assets 0 Total derivatives not designated as hedging instruments $ 492,088 $ 7,528 $ 2,267 Total asset derivatives $ 506,850 $ 7,568 $ 2,291 Liability Derivatives September 30, 2017 December 31, 2016 Balance Sheet Location Notional Amount Fair Value Balance Sheet Location Fair Value Derivatives designated as hedging instruments Fair Value Hedges: Interest rate swap contracts Other liabilities $ 76,869 $ 480 Other liabilities $ 338 Total derivatives designated as hedging instruments $ 76,869 $ 480 $ 338 Derivatives not designated as hedging instruments Interest rate swap contracts Other liabilities $ 0 $ 0 Other liabilities $ 2,267 Forward loan sales commitments Other liabilities 50,063 257 Other liabilities 0 Interest rate lock commitments Other liabilities 65,862 291 Other liabilities 0 Total derivatives not designated as hedging instruments $ 115,925 $ 548 $ 2,267 Total liability derivatives $ 192,794 $ 1,028 $ 2,605
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, 2017 and 2016 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 ) $ (208 ) $ (385 ) Total derivatives in hedging relationships $ (208 ) $ (385 ) Derivatives not designated as hedging instruments Forward loan sales commitments Income from Mortgage (257 ) 0 TBA mortgage-backed securities Income from Mortgage 123 0 Interest rate lock commitments Income from Mortgage (4,484 ) 0 Total derivatives not designated as hedging instruments $ (4,618 ) $ 0 Total derivatives $ (4,826 ) $ (385 ) 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 ) $ (648 ) $ 353 Cash Flow Hedges: Forward loan sales commitments Other income 0 0 Total derivatives in hedging relationships $ (648 ) $ 353 Derivatives not designated as hedging instruments Forward loan sales commitments Income from Mortgage (427 ) 0 TBA mortgage-backed securities Income from Mortgage 2,907 0 Interest rate lock commitments Income from Mortgage (3,465 ) 0 Total derivatives not designated as hedging instruments $ (985 ) $ 0 Total derivatives $ (1,633 ) $ 353

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2017
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, 2017 and December 31, 2016, segregated by the level of the valuation inputs within the fair value hierarchy. Fair Value at September 30, 2017 Using Description Balance as of September 30, 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 $ 115,866 $ 0 $ 115,866 $ 0 State and political subdivisions 305,141 0 305,141 0 Residential mortgage-backed securities Agency 714,700 0 714,700 0 Non-agency 5,846 0 5,846 0 Commercial mortgage-backed securities Agency 420,792 0 420,792 0 Asset-backed securities 13,429 0 13,429 0 Trust preferred collateralized debt obligations 31,659 0 0 31,659 Single issue trust preferred securities 12,467 0 12,467 0 Other corporate securities 19,254 0 19,254 0 Total available for sale debt securities 1,639,154 0 1,607,495 31,659 Available for sale equity securities: Financial services industry 3,016 401 2,615 0 Equity mutual funds (1) 6,250 6,250 0 0 Other equity securities 1,214 1,214 0 0 Total available for sale equity securities 10,480 7,865 2,615 0 Total available for sale securities 1,649,634 7,865 1,610,110 31,659 Loans held for sale 311,186 0 0 311,186 Derivative financial assets: Interest rate swap contracts 40 0 40 0 Interest rate lock commitments 7,027 0 0 7,027 TBA mortgage-backed securities 501 501 0 0 Total derivative financial assets 7,568 501 40 7,027 Liabilities Derivative financial liabilities: Interest rate swap contracts 480 0 480 0 Forward sales commitments 257 0 257 0 Interest rate lock commitments 291 0 291 0 Total derivative financial liabilities 1,028 0 1,028 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, 2016 Using Description Balance as of December 31, 2016 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets Available for sale debt securities: U.S. Treasury securities and obligations of U.S. Government corporations and agencies $ 95,786 $ 0 $ 95,786 $ 0 State and political subdivisions 192,812 0 192,812 0 Residential mortgage-backed securities Agency 584,096 0 584,096 0 Non-agency 7,043 0 7,043 0 Asset-backed securities 217 0 217 0 Commercial mortgage-backed securities Agency 305,341 0 305,341 0 Trust preferred collateralized debt obligations 33,552 0 0 33,552 Single issue trust preferred securities 11,477 0 11,477 0 Other corporate securities 15,062 0 15,062 0 Total available for sale debt securities 1,245,386 0 1,211,834 33,552 Available for sale equity securities: Financial services industry 10,735 1,372 9,363 0 Equity mutual funds (1) 1,820 1,820 0 0 Other equity securities 1,273 1,273 0 0 Total available for sale equity securities 13,828 4,465 9,363 0 Total available for sale securities 1,259,214 4,465 1,221,197 33,552 Derivative financial assets: Interest rate swap contracts 2,291 0 2,291 0 Liabilities Derivative financial liabilities: Interest rate swap contracts 2,605 0 2,605 0 (1) The equity mutual funds are within a rabbi trust for the payment of benefits under a deferred compensation plan for certain key officers of United and its subsidiaries.
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, 2017 and December 31, 2016 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, 2017 December 31, Balance, beginning of period $ 33,552 $ 34,686 Total gains or losses (realized/unrealized): Included in earnings (or changes in net assets) 9 0 Included in other comprehensive income 6,148 (1,134 ) Sales (8,050 ) 0 Balance, end of period $ 31,659 $ 33,552 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, 2017 December 31, Balance, beginning of period $ 0 $ 0 Acquired in Cardinal merger 271,301 0 Originations 1,644,943 0 Sales (1,639,737 ) 0 Total gains or losses during the period recognized in earnings 41,929 0 Transfers in and/or out of Level 3 (7,250 ) 0 Balance, end of period $ 311,186 $ 0 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, 2017 December 31, Balance, beginning of period $ 0 $ 0 Acquired in Cardinal merger 10,393 0 Transfers other (3,366 ) 0 Balance, end of period $ 7,027 $ 0 The amount of total gains or losses for the period included in earnings (or changes in net assets) attributable to the change in unrealized gains or losses relating to assets still held at reporting date $ 0 $ 0
Schedule of Changes in Fair Value Included in Earnings of Financial Instruments for which Fair Value Option has been Elected	The following table reflects the change in fair value included in earnings of financial instruments for which the fair value option has been elected: Description Three Months Ended September 30, 2017 Nine Months Ended September 30, 2017 Assets Loans held for sale Income from mortgage banking activities $ (5,090 ) $ (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, 2017 December 31, 2016 Description Unpaid Fair Value Fair Value Unpaid Fair Fair Value Assets Loans held for sale $ 303,953 $ 311,186 $ 7,233 $ 0 $ 0 $ 0
Summary of Financial Assets Measured at Fair Value on Nonrecurring Basis	The following table summarizes United’s financial assets that were measured at fair value on a nonrecurring basis during the period: Carrying value at September 30, 2017 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) YTD Losses Assets Impaired Loans $ 105,900 $ 0 $ 74,852 $ 31,048 $ 9,045 OREO 26,826 0 26,743 83 2,904 Carrying value at December 31, 2016 Description Balance as of December 31, 2016 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) YTD Losses Assets Impaired Loans $ 80,505 $ 0 $ 27,609 $ 52,896 $ 5,119 OREO 31,510 0 31,510 0 2,086
Summary of Estimated Fair Values of Financial Instruments	The estimated fair values of United’s financial instruments 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, 2017 Cash and cash equivalents $ 1,747,037 $ 1,747,037 $ 0 $ 1,747,037 $ 0 Securities available for sale 1,649,634 1,649,634 7,865 1,610,110 31,659 Securities held to maturity 20,335 19,909 0 16,889 3,020 Other securities 166,756 158,418 0 0 158,418 Loans held for sale 315,031 315,031 0 3,845 311,186 Loans 13,065,542 12,550,352 0 0 12,550,352 Derivative financial assets 7,568 7,568 501 40 7,027 Deposits 13,875,297 13,859,205 0 13,859,205 0 Short-term borrowings 492,036 492,036 0 492,036 0 Long-term borrowings 1,364,246 1,328,753 0 1,328,753 0 Derivative financial liabilities 1,028 1,028 0 1,028 0 December 31, 2016 Cash and cash equivalents $ 1,434,527 $ 1,434,527 $ 0 $ 1,434,527 $ 0 Securities available for sale 1,259,214 1,259,214 4,465 1,221,197 33,552 Securities held to maturity 33,258 31,178 0 28,158 3,020 Other securities 111,166 105,608 0 0 105,608 Loans held for sale 8,445 8,445 0 8,445 0 Loans 10,268,366 10,122,486 0 0 10,122,486 Derivative financial assets 2,291 2,291 0 2,291 0 Deposits 10,796,867 10,785,294 0 10,785,294 0 Short-term borrowings 209,551 209,551 0 209,551 0 Long-term borrowings 1,172,026 1,142,782 0 1,142,782 0 Derivative financial liabilities 2,605 2,605 0 2,605 0

Stock Based Compensation (Table

Stock Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2017
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, 2017, and the changes during the first nine months of 2017 are presented below: Nine Months Ended September 30, 2017 Weighted Average Shares Aggregate Remaining Exercise Outstanding at January 1, 2017 1,411,735 $ 28.05 Assumed in Cardinal merger 153,602 21.47 Granted 253,417 45.27 Exercised (163,562 ) 20.93 Forfeited or expired (2,962 ) 38.81 Outstanding at September 30, 2017 1,652,230 $ 12,602 5.8 $ 30.76 Exercisable at September 30, 2017 1,138,309 $ 11,964 4.5 $ 26.64
Status of United's Nonvested Stock Option Awards	The following table summarizes the status of United’s nonvested stock option awards during the first nine months of 2017: Shares Weighted-Average Nonvested at January 1, 2017 430,278 $ 6.84 Granted 253,417 8.85 Vested (168,274 ) 6.64 Forfeited or expired (1,500 ) 8.85 Nonvested at September 30, 2017 513,921 $ 7.89
Changes to United's Restricted Common Shares	The following summarizes the changes to United’s restricted common shares for the period ended September 30, 2017: Number of Weighted-Average Outstanding at January 1, 2017 137,268 $ 33.61 Granted 89,475 45.27 Vested (53,950 ) 32.23 Forfeited (420 ) 45.30 Outstanding at September 30, 2017 172,373 $ 40.07

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	9 Months Ended
	Sep. 30, 2017
Retirement Benefits [Abstract]
Net Periodic Pension Cost	Net periodic pension cost for the three and nine months ended September 30, 2017 and 2016 included the following components: Three Months Ended September 30 Nine Months Ended September 30 2017 2016 2017 2016 Service cost $ 574 $ 614 $ 1,705 $ 1,829 Interest cost 1,293 1,471 3,837 4,383 Expected return on plan assets (2,072 ) (2,034 ) (6,148 ) (6,058 ) Recognized net actuarial loss 1,111 1,161 3,298 3,458 Net periodic pension (benefit) cost $ 906 $ 1,212 $ 2,692 $ 3,612 Weighted-Average Assumptions: Discount rate 4.49 % 4.75 % 4.49 % 4.75 % Expected return on assets 7.00 % 7.25 % 7.00 % 7.25 % 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, 2017
Equity [Abstract]
Components of Total Comprehensive Income	The components of total comprehensive income for the three and nine months ended September 30, 2017 and 2016 are as follows: Three Months Ended Nine Months Ended 2017 2016 2017 2016 Net Income $ 56,738 $ 41,479 $ 132,606 $ 107,977 Available for sale (“AFS”) securities: AFS securities with OTTI charges during the period 0 0 (60 ) (77 ) Related income tax effect 0 0 22 28 Less: OTTI charges recognized in net income 0 0 60 33 Related income tax benefit 0 0 (22 ) (12 ) Reclassification of previous noncredit OTTI to credit OTTI 0 0 0 415 Related income tax benefit 0 0 0 (150 ) Net unrealized (losses) gains on AFS securities with OTTI 0 0 0 237 AFS securities – all other: Change in net unrealized gain on AFS securities arising during the period 3,584 (7,599 ) 14,846 12,356 Related income tax effect (1,326 ) 2,735 (5,493 ) (4,489 ) Net reclassification adjustment for (gains) losses included in net income (467 ) (1 ) (1,444 ) (251 ) Related income tax expense (benefit) 173 0 534 91 1,964 (4,865 ) 8,443 7,707 Net effect of AFS securities on other comprehensive income 1,964 (4,865 ) 8,443 7,944 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 1,111 1,161 3,298 3,458 Related income tax benefit (394 ) (384 ) (1,191 ) (1,223 ) Net effect of change in pension plan asset on other 717 777 2,107 2,235 Total change in other comprehensive income 2,683 (4,086 ) 10,554 10,183 Total Comprehensive Income $ 59,421 $ 37,393 $ 143,160 $ 118,160
Components of Accumulated Other Comprehensive Income	The components of accumulated other comprehensive income for the nine months ended September 30, 2017 are as follows: Changes in Accumulated Other Comprehensive Income (AOCI) by Component (a) For the Nine Months Ended September 30, 2017 Unrealized Accretion on Defined Items Total Balance at January 1, 2017 ($ 10,297 ) ($ 51 ) ($ 34,369 ) ($ 44,717 ) Other comprehensive income before reclassification 9,353 4 0 9,357 Amounts reclassified from accumulated other comprehensive income (910 ) 0 2,107 1,197 Net current-period other comprehensive income, net of tax 8,443 4 2,107 10,554 Balance at September 30, 2017 ($ 1,854 ) ($ 47 ) ($ 32,262 ) ($ 34,163 )
Reclassifications Out of Accumulated Other Comprehensive Income	Reclassifications out of Accumulated Other Comprehensive Income (AOCI) For the Nine Months Ended September 30, 2017 Details about AOCI Components Amount Affected Line Item in the Statement Where Net Income is Presented Available for sale (“AFS”) securities: Reclassification of previous noncredit OTTI $ 0 Total other-than-temporary impairment losses Net reclassification adjustment for losses (1,444 ) Net gains on sales/calls of investment securities (1,444 ) Total before tax Related income tax effect 534 Tax expense (910 ) Net of tax Pension plan: Recognized net actuarial loss 3,298 (a) 3,298 Total before tax Related income tax effect (1,191 ) Tax expense 2,107 Net of tax Total reclassifications for the period $ 1,197 (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, 2017
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 2017 2016 2017 2016 Distributed earnings allocated to common stock $ 34,587 $ 25,174 $ 95,871 $ 73,242 Undistributed earnings allocated to common stock 22,065 16,234 36,518 34,545 Net earnings allocated to common shareholders $ 56,652 $ 41,408 $ 132,389 $ 107,787 Average common shares outstanding 104,760,153 76,218,573 95,040,664 72,413,246 Equivalents from stock options 307,969 429,200 409,962 333,117 Average diluted shares outstanding 105,068,122 76,647,773 95,450,626 72,746,363 Earnings per basic common share $ 0.54 $ 0.54 $ 1.39 $ 1.49 Earnings per diluted common share $ 0.54 $ 0.54 $ 1.39 $ 1.48

Variable Interest Entities (Tab

Variable Interest Entities (Tables)	9 Months Ended
	Sep. 30, 2017
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 Century Trust March 23, 2000 $ 8,800 10.875% Fixed March 8, 2030 United Statutory Trust III December 17, 2003 $ 20,000 3-month December 17, 2033 United Statutory Trust IV December 19, 2003 $ 25,000 3-month January 23, 2034 United Statutory Trust V July 12, 2007 $ 50,000 3-month October 1, 2037 United Statutory Trust VI September 20, 2007 $ 30,000 3-month December 15, 2037 Premier Statutory Trust II September 25, 2003 $ 6,000 3-month October 8, 2033 Premier Statutory Trust III May 16, 2005 $ 8,000 3-month June 15, 2035 Premier Statutory Trust IV June 20, 2006 $ 14,000 3-month September 23, 2036 Premier Statutory Trust V December 14, 2006 $ 10,000 3-month March 1, 2037 Centra Statutory Trust I September 20, 2004 $ 10,000 3-month September 20, 2034 Centra Statutory Trust II June 15, 2006 $ 10,000 3-month July 7, 2036 Virginia Commerce Trust II December 19, 2002 $ 15,000 6-month December 19, 2032 Virginia Commerce Trust III December 20, 2005 $ 25,000 3-month February 23, 2036 Cardinal Statutory Trust I July 27, 2004 $ 20,000 3-month September 15, 2034 UFBC Capital Trust I December 30, 2004 $ 5,000 3-month March 15, 2035
Summary of Quantitative Information Related to Significant Involvement in Unconsolidated Variable Interest Entities	The following table summarizes quantitative information about United’s significant involvement in unconsolidated VIEs: As of September 30, 2017 As of December 31, 2016 Aggregate Assets Aggregate Liabilities Risk Of Loss (1) Aggregate Assets Aggregate Liabilities Risk Of Loss (1) Trust preferred securities $ 266,560 $ 257,605 $ 8,955 $ 240,668 $ 232,583 $ 8,085 (1) Represents investment in VIEs.

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2017
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, 2017 and 2016 is as follows: At and For the Three Months Ended September 30, 2017 Community Mortgage Other Consolidated Net interest income $ 152,886 $ (36 ) $ (2,574 ) $ 150,276 Provision for loans losses 7,279 0 0 7,279 Other income 18,373 19,936 (80 ) 38,229 Other expense 74,553 24,036 (1,937 ) 96,652 Income taxes 29,490 (1,332 ) (322 ) 27,836 Net income (loss) $ 59,937 $ (2,804 ) $ (395 ) $ 56,738 Total assets (liabilities) $ 18,780,395 $ 350,483 $ (900 ) $ 19,129,978 Average assets (liabilities) 18,620,035 321,744 (13,994 ) 18,927,785 At and For the Three Months Ended September 30, 2016 Community Other Consolidated Net interest income $ 113,033 $ (1,964 ) $ 111,069 Provision for loans losses 6,988 0 6,988 Other income 19,666 (645 ) 19,021 Other expense 63,009 (232 ) 62,777 Income taxes 19,729 (883 ) 18,846 Net income (loss) $ 42,973 $ (1,494 ) $ 41,479 Total assets (liabilities) $ 14,364,797 $ (20,101 ) $ 14,344,696 Average assets (liabilities) 14,182,202 (22,633 ) 14,159,569 At and For the Nine Months Ended September 30, 2017 Community Mortgage Other Consolidated Net interest income $ 401,044 $ 54 $ (6,957 ) $ 394,141 Provision for loans losses 21,429 0 0 21,429 Other income 53,409 42,329 3,143 98,881 Other expense 215,935 42,744 12,952 271,631 Income taxes 73,214 (39 ) (5,819 ) 67,356 Net income (loss) $ 143,875 $ (322 ) $ (10,947 ) $ 132,606 Total assets (liabilities) $ 18,780,395 $ 350,483 $ (900 ) $ 19,129,978 Average assets (liabilities) 17,020,928 187,118 (20,402 ) 17,187,644 At and For the Nine Months Ended September 30, 2016 Community Other Consolidated Net interest income $ 317,835 $ (5,757 ) $ 312,078 Provision for loans losses 18,690 0 18,690 Other income 55,323 (1,943 ) 53,380 Other expense 186,322 (634 ) 185,688 Income taxes 55,580 (2,477 ) 53,103 Net income (loss) $ 112,566 $ (4,589 ) $ 107,977 Total assets (liabilities) $ 14,364,797 $ (20,101 ) $ 14,344,696 Average assets (liabilities) 13,125,973 (21,575 ) 13,104,398

Summary of Significant Accoun44

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017	Sep. 30, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase to net cash from operating activity		$ 125,151	$ 125,948
Decrease to net cash from financing activities		(197,092)	231,756
ASU 2016-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Decrease in income tax expense	$ 146	$ 960
Increase to net cash from operating activity			2,083
Decrease to net cash from financing activities			$ (2,083)

Mergers and Acquisitions - Addi

Mergers and Acquisitions - Additional Information (Detail) - USD ($)	Sep. 30, 2017	Apr. 21, 2017	Jun. 03, 2016	Sep. 30, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Total assets at consummation	$ 19,129,978,000			$ 19,129,978,000	$ 14,508,892,000
Loans at consummation	13,156,854,000			13,156,854,000	10,356,719,000
Deposits at consummation	13,875,297,000			13,875,297,000	10,796,867,000
Resulting goodwill	1,487,607,000			1,487,607,000	$ 863,767,000
Liabilities to provide severance benefits	$ 0			$ 0
Contractually required principal and interest at acquisition		$ 132,837	$ 138,125
Expected cash flows at acquisition		108,275	117,564
Estimated fair value of acquired impaired loans at acquisition		$ 86,696	95,570
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
Loans at consummation		3,313,033
Deposits at consummation		3,344,740
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		$ 622,513,000
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
Premium on long-term FHLB advances acquired		10,740,000
Estimated remaining life of discount on leases acquired	6 years
Estimated remaining life of discount on trust preferred issuances acquired	16 years 11 months 19 days
Estimated remaining life of premium on interest-bearing deposits acquired	5 years
Estimated remaining life of the FHLB advances acquired	4 years 9 months 22 days
Assumed liabilities to provide severance benefits		1,825,000
Contractually required principal and interest at acquisition		4,211,734,000
Expected cash flows at acquisition		4,155,558,000
Estimated fair value of acquired impaired loans at acquisition		3,168,599,000
Revenue since acquisition included in consolidated results				$ 157,326
Revenue since acquisition included in consolidated results				$ 81,817
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		$ 28,723,000
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		$ 1,230
Bank of Georgetown [Member]
Business Acquisition [Line Items]
Outstanding common stock acquired	100.00%			100.00%
Total assets at consummation	$ 1,278,837			$ 1,278,837
Loans at consummation	999,773			999,773
Deposits at consummation	971,369			971,369
Common stock paid in cash			264,505,000
Common stock value			253,799,000
Stock options exchanged value			$ 10,696,000
Common stock, shares issued			6,527,746
Resulting goodwill			$ 154,172,000
Fractional shares cash paid per share			10,000
Goodwill from acquisition expected to be tax deductible			0
Fair value discounts on loans acquired			43,072
Fair value discounts on leases				1,550
Premiums on interest-bearing deposits acquired			316,000
Premium on long-term FHLB advances acquired	$ 2,659			2,659
Estimated remaining life of premium on interest-bearing deposits acquired	3 months 29 days
Estimated remaining life of the FHLB advances acquired	7 years 11 months 1 day
Assumed liabilities to provide severance benefits	$ 300,000			$ 300,000
Contractually required principal and interest at acquisition			1,275,398,000
Expected cash flows at acquisition			1,241,418,000
Estimated fair value of acquired impaired loans at acquisition			966,870,000
Bank of Georgetown [Member] | Common Stock [Member]
Business Acquisition [Line Items]
Common stock value			$ 253,799,000
Common stock, shares issued			6,527,746
Closing market price per common share			$ 38.88
Bank of Georgetown [Member] | Core Deposit Intangible Assets [Member]
Business Acquisition [Line Items]
Purchase price allocation of Identifiable Intangible assets			$ 9,058,000
Estimated period of amortization of core deposit intangibles			10 years
Fractional shares cash paid per share			$ 10,000

Mergers and Acquisitions - Sche

Mergers and Acquisitions - Schedule of Acquired Loans Accounted for at Fair Value (Detail) - USD ($)	Apr. 21, 2017	Jun. 03, 2016
Business Acquisition [Line Items]
Contractually required principal and interest at acquisition	$ 132,837	$ 138,125
Expected cash flows at acquisition	108,275	117,564
Basis in acquired loans at acquisition - estimated fair value	86,696	95,570
Cardinal Financial Corporation [Member]
Business Acquisition [Line Items]
Contractually required principal and interest at acquisition	4,211,734,000
Contractual cash flows not expected to be collected	(56,176,000)
Expected cash flows at acquisition	4,155,558,000
Interest component of expected cash flows	(986,959,000)
Basis in acquired loans at acquisition - estimated fair value	$ 3,168,599,000
Bank of Georgetown [Member]
Business Acquisition [Line Items]
Contractually required principal and interest at acquisition		1,275,398,000
Contractual cash flows not expected to be collected		(33,980,000)
Expected cash flows at acquisition		1,241,418,000
Interest component of expected cash flows		(274,548,000)
Basis in acquired loans at acquisition - estimated fair value		$ 966,870,000

Mergers and Acquisitions - Sc47

Mergers and Acquisitions - Schedule of Fair Value of Acquired Identifiable Assets and Liabilities Assumed (Detail) - USD ($) $ in Thousands	Apr. 21, 2017	Jun. 03, 2016	Sep. 30, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Resulting goodwill			$ 1,487,607	$ 863,767
Cardinal Financial Corporation [Member]
Business Acquisition [Line Items]
Value of common shares issued	$ 972,499
Fair value of stock options assumed	2,741
Cash for fractional shares	14
Total purchase price	975,254
Cash and cash equivalents	44,545
Investment securities	395,829
Loans held for sale	271,301
Loans	3,168,599
Premises and equipment	24,208
Other assets	135,383
Total identifiable assets	4,069,818
Deposits	3,349,812
Short-term borrowings	96,215
Long-term borrowings	220,119
Unfavorable lease liability	2,281
Other liabilities	48,650
Total identifiable liabilities	3,717,077
Fair value of net assets acquired including identifiable intangible assets	352,741
Resulting goodwill	622,513
Cardinal Financial Corporation [Member] | Core Deposit Intangible Assets [Member]
Business Acquisition [Line Items]
Cash for fractional shares	14
Core deposit intangibles	28,723
Cardinal Financial Corporation [Member] | George Mason Trade Name Intangible [Member]
Business Acquisition [Line Items]
Core deposit intangibles	$ 1,230
Bank of Georgetown [Member]
Business Acquisition [Line Items]
Value of common shares issued		$ 253,799
Fair value of stock options assumed		10,696
Cash for fractional shares		10
Total purchase price		264,505
Cash and cash equivalents		29,340
Investment securities		219,783
Loans		966,870
Premises and equipment		5,574
Other assets		31,605
Total identifiable assets		1,262,230
Deposits		971,685
Short-term borrowings		101,021
Long-term borrowings		67,659
Other liabilities		11,532
Total identifiable liabilities		1,151,897
Fair value of net assets acquired including identifiable intangible assets		110,333
Resulting goodwill		154,172
Bank of Georgetown [Member] | Core Deposit Intangible Assets [Member]
Business Acquisition [Line Items]
Cash for fractional shares		10
Core deposit intangibles		$ 9,058

Mergers and Acquisitions - Sc48

Mergers and Acquisitions - Schedule of Fair Value of Acquired Identifiable Assets and Liabilities Assumed (Parenthetical) (Detail) - shares	Apr. 21, 2017	Jun. 03, 2016
Cardinal Financial Corporation [Member]
Business Acquisition [Line Items]
Common stock, shares issued	23,690,589
Bank of Georgetown [Member]
Business Acquisition [Line Items]
Common stock, shares issued		6,527,746

Mergers and Acquisitions - Sc49

Mergers and Acquisitions - Schedule of Business Acquisition Pro Forma Information (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Business Combinations [Abstract]
Total Revenues	$ 573,790	$ 585,223
Net Income	$ 136,104	$ 160,731

Investment Securities - Summary

Investment Securities - Summary of Amortized Cost and Estimated Fair Values of Available for Sale Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Schedule of Investments [Line Items]
Amortized Cost	$ 1,654,657	$ 1,277,639
Gross Unrealized Gains	11,446	10,912
Gross Unrealized Losses	16,469	29,337
Estimated Fair Value	1,649,634	1,259,214
Cumulative OTTI in AOCI	20,856	26,038
U.S. Treasury Securities and Obligations of U.S. Government Corporations and Agencies [Member]
Schedule of Investments [Line Items]
Amortized Cost	115,224	95,247
Gross Unrealized Gains	864	698
Gross Unrealized Losses	222	159
Estimated Fair Value	115,866	95,786
Cumulative OTTI in AOCI	0	0
State and Political Subdivisions [Member]
Schedule of Investments [Line Items]
Amortized Cost	305,096	196,350
Gross Unrealized Gains	2,567	1,364
Gross Unrealized Losses	2,522	4,902
Estimated Fair Value	305,141	192,812
Cumulative OTTI in AOCI	0	0
Residential Mortgage-Backed Securities, Agency [Member]
Schedule of Investments [Line Items]
Amortized Cost	715,003	585,208
Gross Unrealized Gains	3,819	3,999
Gross Unrealized Losses	4,122	5,111
Estimated Fair Value	714,700	584,096
Cumulative OTTI in AOCI	0	0
Residential Mortgage-Backed Securities, Non-agency [Member]
Schedule of Investments [Line Items]
Amortized Cost	5,259	6,629
Gross Unrealized Gains	587	426
Gross Unrealized Losses	0	12
Estimated Fair Value	5,846	7,043
Cumulative OTTI in AOCI	86	86
Commercial Mortgage-Backed Securities, Agency [Member]
Schedule of Investments [Line Items]
Amortized Cost	420,115	304,635
Gross Unrealized Gains	2,081	1,948
Gross Unrealized Losses	1,404	1,242
Estimated Fair Value	420,792	305,341
Cumulative OTTI in AOCI	0	0
Asset-Backed Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	13,422	217
Gross Unrealized Gains	10	0
Gross Unrealized Losses	3	0
Estimated Fair Value	13,429	217
Cumulative OTTI in AOCI	0	0
Trust Preferred Collateralized Debt Obligations [Member]
Schedule of Investments [Line Items]
Amortized Cost	38,186	48,558
Gross Unrealized Gains	317	729
Gross Unrealized Losses	6,844	15,735
Estimated Fair Value	31,659	33,552
Cumulative OTTI in AOCI	20,770	25,952
Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	13,404	13,363
Gross Unrealized Gains	404	284
Gross Unrealized Losses	1,341	2,170
Estimated Fair Value	12,467	11,477
Cumulative OTTI in AOCI	0	0
Corporate Bonds [Member]
Schedule of Investments [Line Items]
Amortized Cost	18,998	14,996
Gross Unrealized Gains	256	66
Gross Unrealized Losses	0	0
Estimated Fair Value	19,254	15,062
Cumulative OTTI in AOCI	0	0
Marketable Equity Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	9,950	12,436
Gross Unrealized Gains	541	1,398
Gross Unrealized Losses	11	6
Estimated Fair Value	10,480	13,828
Cumulative OTTI in AOCI	$ 0	$ 0

Investment Securities - Summa51

Investment Securities - Summary of Securities Available for Sale in an Unrealized Loss Position (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	$ 697,366	$ 612,613
Less than 12 months, Unrealized Losses	5,655	11,420
12 months or longer, Fair Value	136,159	36,982
12 months or longer, Unrealized Losses	10,814	17,917
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	27,053	24,101
Less than 12 months, Unrealized Losses	128	159
12 months or longer, Fair Value	19,932	0
12 months or longer, Unrealized Losses	94	0
State and Political Subdivisions [Member]
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	83,310	116,300
Less than 12 months, Unrealized Losses	896	4,902
12 months or longer, Fair Value	38,004	0
12 months or longer, Unrealized Losses	1,626	0
Residential Mortgage-Backed Securities, Agency [Member]
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	351,936	309,376
Less than 12 months, Unrealized Losses	3,410	5,111
12 months or longer, Fair Value	31,690	0
12 months or longer, Unrealized Losses	712	0
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	218
12 months or longer, Unrealized Losses	0	12
Commercial Mortgage-Backed Securities, Agency [Member]
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	228,307	162,479
Less than 12 months, Unrealized Losses	1,218	1,242
12 months or longer, Fair Value	12,272	0
12 months or longer, Unrealized Losses	186	0
Asset-Backed Securities [Member]
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	6,760	0
Less than 12 months, Unrealized Losses	3	0
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	29,544	28,579
12 months or longer, Unrealized Losses	6,844	15,735
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	4,365	8,185
12 months or longer, Unrealized Losses	1,341	2,170
Marketable Equity Securities [Member]
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	0	357
Less than 12 months, Unrealized Losses	0	6
12 months or longer, Fair Value	352	0
12 months or longer, Unrealized Losses	$ 11	$ 0

Investment Securities - Summa52

Investment Securities - Summary of Gains or Losses on Proceeds from Maturities, Sales and Calls of Available for Sale Securities by Specific Identification Method (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Investments, Debt and Equity Securities [Abstract]
Proceeds from sales and calls	$ 64,257	$ 174,015	$ 631,561	$ 368,246
Gross realized gains	1,781	3	2,840	259
Gross realized losses	$ 1,314	$ 1	$ 1,396	$ 7

Investment Securities - Additio

Investment Securities - Additional Information (Detail)	3 Months Ended		9 Months Ended		96 Months Ended
	Sep. 30, 2017USD ($)Securities	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)Securities	Sep. 30, 2016USD ($)	Dec. 31, 2007USD ($)	Dec. 31, 2016USD ($)
Schedule of Investments [Line Items]
Gross unrealized losses on available for sale securities	$ 16,469,000		$ 16,469,000			$ 29,337,000
Available for sale securities in unrealized loss position | Securities	375		375
Available for sale securities in portfolio, number | Securities	822		822
Amortized cost of available for sale securities	$ 1,654,657,000		$ 1,654,657,000			1,277,639,000
Capitalization of banks, equal to or greater than, in the single-issue trust preferred portfolio	10,000,000,000		10,000,000,000
Noncredit-related other-than-temporary impairment recognized	20,856,000		$ 20,856,000			26,038,000
New issuance of Preferred Stock estimated					$ 60,000,000,000
Security other-than-temporarily impaired			100.00%
Amortized cost of equity securities	9,950		$ 9,950
Gross realized gains	0	$ 0	0	$ 0
Gross realized losses	0	$ 0	0	$ 0
Carrying value of securities pledged	1,312,813		1,312,813			1,137,408
TRUP CDOs [Member]
Schedule of Investments [Line Items]
Credit-related other-than-temporary impairment recognized in earnings	0
Noncredit-related other-than-temporary impairment recognized	20,770		20,770
SunTrust Bank [Member]
Schedule of Investments [Line Items]
Amortized cost of trust preferred securities	7,424,000		7,424,000
Royal Bank of Scotland [Member]
Schedule of Investments [Line Items]
Amortized cost of trust preferred securities	976,000		$ 976,000
Minimum [Member]
Schedule of Investments [Line Items]
Other-than-temporarily impaired, the collateralization ratios			105.40%
Maximum [Member]
Schedule of Investments [Line Items]
Other-than-temporarily impaired, the collateralization ratios			414.50%
Weighted Average [Member]
Schedule of Investments [Line Items]
Other-than-temporarily impaired, the collateralization ratios			283.80%
Median [Member]
Schedule of Investments [Line Items]
Other-than-temporarily impaired, the collateralization ratios			260.00%
Investment Grade [Member]
Schedule of Investments [Line Items]
Amortized cost of available for sale single issue trust preferred securities	3,017		$ 3,017
Below Investment Grade [Member]
Schedule of Investments [Line Items]
Amortized cost of available for sale single issue trust preferred securities	5,707		5,707
Split Rated [Member]
Schedule of Investments [Line Items]
Amortized cost of available for sale single issue trust preferred securities	4,680		4,680
State and Political Subdivisions [Member]
Schedule of Investments [Line Items]
Gross unrealized losses on available for sale securities	2,522,000		2,522,000			4,902,000
Amortized cost of available for sale securities	$ 305,096,000		$ 305,096,000			196,350,000
Percent of portfolio with credit support	75.00%		75.00%
Investment grade credit rate percentage			1.00%
Number of equity securities other-than-temporarily impaired | Securities	0		0
Noncredit-related other-than-temporary impairment recognized	$ 0		$ 0			0
Agency Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Amortized cost of available for sale securities	1,135,118,000		1,135,118,000
Commercial Mortgage-Backed Securities, Agency [Member]
Schedule of Investments [Line Items]
Gross unrealized losses on available for sale securities	1,404,000		1,404,000			1,242,000
Amortized cost of available for sale securities	420,115,000		420,115,000			304,635,000
Noncredit-related other-than-temporary impairment recognized	0		0			0
Residential Mortgage-Backed Securities, Agency [Member]
Schedule of Investments [Line Items]
Gross unrealized losses on available for sale securities	4,122,000		4,122,000			5,111,000
Amortized cost of available for sale securities	715,003,000		715,003,000			585,208,000
Noncredit-related other-than-temporary impairment recognized	0		0			0
Residential Mortgage-Backed Securities, Non-agency [Member]
Schedule of Investments [Line Items]
Gross unrealized losses on available for sale securities	0		0			12,000
Amortized cost of available for sale securities	5,259,000		5,259,000			6,629,000
Noncredit-related other-than-temporary impairment recognized	86,000		$ 86,000			$ 86,000
Residential Mortgage-Backed Securities, Non-agency [Member] | Originated Prior to 2005 [Member]
Schedule of Investments [Line Items]
Percentage of portfolio of non-agency mortgage backed securities with collateral			18.00%
Residential Mortgage-Backed Securities, Non-agency [Member] | Originated in 2006 and 2007 [Member]
Schedule of Investments [Line Items]
Percentage of portfolio of non-agency mortgage backed securities with collateral			82.00%
Residential Mortgage-Backed Securities, Non-agency [Member] | Investment Grade [Member]
Schedule of Investments [Line Items]
Amortized cost of available for sale securities	627,000		$ 627,000
Residential Mortgage-Backed Securities, Non-agency [Member] | Below Investment Grade [Member]
Schedule of Investments [Line Items]
Amortized cost of available for sale securities	$ 4,632,000		$ 4,632,000

Investment Securities - Summa54

Investment Securities - Summary of Unrealized Loss Positions of Available for Sale TRUP CDOs and Single Issue Trust Preferred Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Schedule of Investments [Line Items]
Amortized Cost	$ 1,654,657	$ 1,277,639
Fair Value	1,649,634	$ 1,259,214
Trup CDOs and Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	38,186
Fair Value	31,659
Net Unrealized Loss	6,527
Senior - Bank [Member] | Trup CDOs and Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	5,208
Fair Value	5,287
Net Unrealized Loss	(79)
Mezzanine - Bank (now in senior position) [Member] | Trup CDOs and Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	6,428
Fair Value	5,518
Net Unrealized Loss	910
Mezzanine - Bank [Member] | Trup CDOs and Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	22,656
Fair Value	17,918
Net Unrealized Loss	4,738
Mezzanine - Bank & Insurance (combination) [Member] | Trup CDOs and Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	3,894
Fair Value	2,936
Net Unrealized Loss	958
Investment Grade [Member] | Trup CDOs and Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	3,410
Investment Grade [Member] | Senior - Bank [Member] | Trup CDOs and Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	3,410
Investment Grade [Member] | Mezzanine - Bank (now in senior position) [Member] | Trup CDOs and Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	0
Investment Grade [Member] | Mezzanine - Bank [Member] | Trup CDOs and Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	0
Investment Grade [Member] | Mezzanine - Bank & Insurance (combination) [Member] | Trup CDOs and Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	0
Split Rated [Member] | Trup CDOs and Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	0
Split Rated [Member] | Senior - Bank [Member] | Trup CDOs and Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	0
Split Rated [Member] | Mezzanine - Bank (now in senior position) [Member] | Trup CDOs and Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	0
Split Rated [Member] | Mezzanine - Bank [Member] | Trup CDOs and Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	0
Split Rated [Member] | Mezzanine - Bank & Insurance (combination) [Member] | Trup CDOs and Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	0
Below Investment Grade [Member] | Trup CDOs and Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	34,776
Below Investment Grade [Member] | Senior - Bank [Member] | Trup CDOs and Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	1,798
Below Investment Grade [Member] | Mezzanine - Bank (now in senior position) [Member] | Trup CDOs and Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	6,428
Below Investment Grade [Member] | Mezzanine - Bank [Member] | Trup CDOs and Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	22,656
Below Investment Grade [Member] | Mezzanine - Bank & Insurance (combination) [Member] | Trup CDOs and Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	$ 3,894

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, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Investments, Debt and Equity Securities [Abstract]
Cumulative credit losses, Beginning Balance	$ 22,162	$ 22,162	$ 22,162	$ 23,773
Additional credit losses on securities for which OTTI was previously recognized	0	0	0	33
Reductions during the period for securities for which the amount previously recognized in other comprehensive income was recognized in earnings	(4,102)	0	(4,102)	(1,644)
Cumulative credit losses, Ending Balance	$ 18,060	$ 22,162	$ 18,060	$ 22,162

Investment Securities - Summa56

Investment Securities - Summary of Maturities of Securities Available for Sale by Amortized Cost and Estimated Fair Value (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Investments, Debt and Equity Securities [Abstract]
Due in one year or less, Amortized Cost	$ 57,720	$ 53,286
Due after one year through five years, Amortized Cost	370,020	296,181
Due after five years through ten years, Amortized Cost	342,176	213,094
Due after ten years, Amortized Cost	874,791	702,642
Marketable equity securities, Amortized Cost	9,950	12,436
Amortized Cost	1,654,657	1,277,639
Due in one year or less, Estimated Fair Value	57,622	53,330
Due after one year through five years, Estimated Fair Value	371,007	297,385
Due after five years through ten years, Estimated Fair Value	343,326	213,791
Due after ten years, Estimated Fair Value	867,199	680,880
Marketable equity securities, Estimated Fair Value	10,480	13,828
Total available for sale securities	$ 1,649,634	$ 1,259,214

Investment Securities - Summa57

Investment Securities - Summary of Amortized Cost and Estimated Fair Values of Securities Held to Maturity (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Schedule of Investments [Line Items]
Amortized Cost	$ 20,335	$ 33,258
Gross Unrealized Gains	416	592
Gross Unrealized Losses	842	2,672
Estimated Fair Value	19,909	31,178
U.S. Treasury Securities and Obligations of U.S. Government Corporations and Agencies [Member]
Schedule of Investments [Line Items]
Amortized Cost	5,215	5,295
Gross Unrealized Gains	400	570
Gross Unrealized Losses	0	0
Estimated Fair Value	5,615	5,865
State and Political Subdivisions [Member]
Schedule of Investments [Line Items]
Amortized Cost	5,674	8,598
Gross Unrealized Gains	12	17
Gross Unrealized Losses	0	0
Estimated Fair Value	5,686	8,615
Residential Mortgage-Backed Securities, Agency [Member]
Schedule of Investments [Line Items]
Amortized Cost	26	30
Gross Unrealized Gains	4	5
Gross Unrealized Losses	0	0
Estimated Fair Value	30	35
Single Issue Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	9,400	19,315
Gross Unrealized Gains	0	0
Gross Unrealized Losses	842	2,672
Estimated Fair Value	8,558	16,643
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 - Summa58

Investment Securities - Summary of Maturities of Debt Securities Held to Maturity by Amortized Cost and Estimated Fair Value (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Investments, Debt and Equity Securities [Abstract]
Due in one year or less, Amortized Cost	$ 0	$ 1,040
Due after one year through five years, Amortized Cost	9,189	8,268
Due after five years through ten years, Amortized Cost	5,726	3,585
Due after ten years, Amortized Cost	5,420	20,365
Amortized Cost	20,335	33,258
Due in one year or less, Estimated Fair Value	0	1,041
Due after one year through five years, Estimated Fair Value	9,600	8,850
Due after five years through ten year, Estimated Fair Value	5,382	3,589
Due after ten years, Estimated Fair Value	4,927	17,698
Estimated Fair Value, Total	$ 19,909	$ 31,178

Loans - Major Classes of Loans

Loans - Major Classes of Loans (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Commercial, financial, and agricultural
Total commercial, financial & agricultural	$ 7,808,681	$ 6,088,775
Residential real estate	3,050,868	2,403,437
Construction & land development	1,599,632	1,255,738
Consumer:
Bankcard	13,775	14,187
Other consumer	683,898	594,582
Total Financing Receivables	13,156,854	10,356,719
Owner-Occupied [Member]
Commercial, financial, and agricultural
Total commercial, financial & agricultural	1,364,757	1,049,885
Nonowner-Occupied [Member]
Commercial, financial, and agricultural
Total commercial, financial & agricultural	4,686,183	3,425,453
Other Commercial Loans [Member]
Commercial, financial, and agricultural
Total commercial, financial & agricultural	$ 1,757,741	$ 1,613,437

Loans - Additional Information

Loans - Additional Information (Detail) - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Loans held for sale	$ 315,031,000	$ 8,445,000
Acquired impaired loans from merger	$ 13,156,854,000	10,356,719,000
Percentage of acquired impaired loans from merger on total gross loans	1.73%
Recorded investment in acquired impaired loans	$ 227,754,000	231,096,000
Directors and Officers [Member]
Related party loans	364,774	$ 255,476
Maximum [Member]
Percentage of acquired impaired loans from merger on total gross loans		1.66%
Loans Acquired with Deteriorated Credit Quality [Member]
Acquired impaired loans from merger	$ 227,754,000	$ 171,596,000

Loans - Activity for Accretable

Loans - Activity for Accretable Yield (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2017USD ($)
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	$ 29,165
Accretion (including cash recoveries)	(11,312)
Additions	17,444
Net reclassifications to accretable from non-accretable	2,727
Disposals (including maturities, foreclosures, and charge-offs)	(2,367)
Accretable yield at the end of the period	$ 35,657

Credit Quality - Additional Inf

Credit Quality - Additional Information (Detail)	3 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2016USD ($)SecurityLoan	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)SecurityLoan	Dec. 31, 2016USD ($)
Receivables [Abstract]
Minimum days for discontinue of accrual interest on commercial and consumer loan		90 days
Maximum days for discontinue of accrual interest on commercial and consumer loan		120 days
Troubled debt restructuring		$ 46,132		$ 21,152
Restructured loans on nonaccrual status		29,717		11,106
Restructured loans modified by reduction in interest		2,043
Restructured loan and interest		4,507
Restructured loans modified by change in terms		39,582
Restructured loans modified by reduction in interest rate and change in terms			$ 1,400,000
Restructured loans modified by change in loan terms amount	$ 110,000	$ 29,024,000	$ 2,909,000
Number of loans restructured | SecurityLoan	0		0
Minimum number of days required for special mention		30 days
Maximum number of days required for special mention		89 days
Number of days required for substandard		90 days
Real estate acquired in foreclosure or other settlement of loans		$ 26,826,000		31,510,000
Recorded investment of consumer mortgage loans		$ 116,000		$ 660,000

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, 2016USD ($)Contract	Sep. 30, 2017USD ($)Contract	Sep. 30, 2016USD ($)Contract
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	1	10	7
Pre-Modification Outstanding Recorded Investment	$ 110	$ 30,891	$ 4,840
Post-Modification Outstanding Recorded Investment	$ 110	$ 29,024	$ 4,309
Construction & Land Development [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	0	1	0
Pre-Modification Outstanding Recorded Investment	$ 0	$ 1,456	$ 0
Post-Modification Outstanding Recorded Investment	$ 0	$ 1,400	$ 0
Commercial Real Estate [Member] | Owner-Occupied [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	0	1	1
Pre-Modification Outstanding Recorded Investment	$ 0	$ 5,333	$ 1,190
Post-Modification Outstanding Recorded Investment	$ 0	$ 5,333	$ 1,184
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	1	8	5
Pre-Modification Outstanding Recorded Investment	$ 110	$ 24,102	$ 2,250
Post-Modification Outstanding Recorded Investment	$ 110	$ 22,291	$ 1,725
Residential Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	0	0	1
Pre-Modification Outstanding Recorded Investment	$ 0	$ 0	$ 1,400
Post-Modification Outstanding Recorded Investment	$ 0	$ 0	$ 1,400
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, 2017USD ($)Contract	Sep. 30, 2017USD ($)Contract
Financing Receivable, Modifications [Line Items]
Number of Contracts | Contract	1	1
Recorded Investment | $	$ 1,495	$ 1,495
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 | $	$ 1,495	$ 1,495
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, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, 30-89 Days Past Due	$ 76,456	$ 74,633
Loans, Total Past Due	228,438	177,850
Loans, Current & Other	12,928,416	10,178,869
Total Financing Receivables	13,156,854	10,356,719
Loans, Recorded Investment >90 Days & Accruing	22,249	8,586
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Total Past Due	151,982	103,217
Construction & Land Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, 30-89 Days Past Due	3,351	3,809
Loans, Total Past Due	21,203	11,588
Loans, Current & Other	1,578,429	1,244,150
Total Financing Receivables	1,599,632	1,255,738
Loans, Recorded Investment >90 Days & Accruing	14,828	33
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	17,852	7,779
Commercial Real Estate [Member] | Owner-Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, 30-89 Days Past Due	9,704	5,850
Loans, Total Past Due	16,616	9,831
Loans, Current & Other	1,348,141	1,040,054
Total Financing Receivables	1,364,757	1,049,885
Loans, Recorded Investment >90 Days & Accruing	0	94
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	6,912	3,981
Commercial Real Estate [Member] | Nonowner-Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, 30-89 Days Past Due	7,686	9,288
Loans, Total Past Due	28,483	30,135
Loans, Current & Other	4,657,700	3,395,318
Total Financing Receivables	4,686,183	3,425,453
Loans, Recorded Investment >90 Days & Accruing	0	172
Commercial Real Estate [Member] | Nonowner-Occupied [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Total Past Due	20,797	20,847
Other Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, 30-89 Days Past Due	13,589	15,273
Loans, Total Past Due	92,931	58,039
Loans, Current & Other	1,664,810	1,555,398
Total Financing Receivables	1,757,741	1,613,437
Loans, Recorded Investment >90 Days & Accruing	802	2,518
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	79,342	42,766
Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, 30-89 Days Past Due	33,654	29,976
Loans, Total Past Due	59,218	55,967
Loans, Current & Other	2,991,650	2,347,470
Total Financing Receivables	3,050,868	2,403,437
Loans, Recorded Investment >90 Days & Accruing	5,298	4,216
Residential Real Estate [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Total Past Due	25,564	25,991
Consumer [Member] | Bankcard [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, 30-89 Days Past Due	385	422
Loans, Total Past Due	595	563
Loans, Current & Other	13,180	13,624
Total Financing Receivables	13,775	14,187
Loans, Recorded Investment >90 Days & Accruing	210	141
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	210	141
Consumer [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, 30-89 Days Past Due	8,087	10,015
Loans, Total Past Due	9,392	11,727
Loans, Current & Other	674,506	582,855
Total Financing Receivables	683,898	594,582
Loans, Recorded Investment >90 Days & Accruing	1,111	1,412
Consumer [Member] | Other Consumer [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, Total Past Due	$ 1,305	$ 1,712

Credit Quality - Schedule of 66

Credit Quality - Schedule of Age Analysis of its Past Due Loans, Segregated by Class of Loans (Parenthetical) (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Acquired impaired loans from merger	$ 13,156,854	$ 10,356,719
Loans Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Acquired impaired loans from merger	227,754	171,596
Loans and Debt Securities Acquired with Deteriorated Credit Quality [Member] | Loans Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Acquired impaired loans from merger	$ 227,754	$ 171,596

Credit Quality - Schedule of No

Credit Quality - Schedule of Nonaccrual Loans, Segregated by Class of Loans (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans on Nonaccrual Status	$ 129,733	$ 94,631
Construction & Land Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans on Nonaccrual Status	3,024	7,746
Commercial Real Estate [Member] | Owner-Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans on Nonaccrual Status	6,912	3,887
Commercial Real Estate [Member] | Nonowner-Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans on Nonaccrual Status	20,797	20,675
Other Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans on Nonaccrual Status	78,540	40,248
Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans on Nonaccrual Status	20,266	21,775
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	$ 194	$ 300

Credit Quality - Schedule of Cr

Credit Quality - Schedule of Credit Quality Indicators Information, by Class of Loans (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	$ 13,156,854	$ 10,356,719
Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	3,050,868	2,403,437
Other Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	1,757,741	1,613,437
Bankcard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	13,775	14,187
Other Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	683,898	594,582
Owner-Occupied [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	1,364,757	1,049,885
Nonowner-Occupied [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	4,686,183	3,425,453
Construction & Land Development [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	1,599,632	1,255,738
Pass [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	2,999,614	2,348,017
Pass [Member] | Other Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	1,611,250	1,463,797
Pass [Member] | Bankcard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	13,180	13,624
Pass [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	674,447	582,704
Pass [Member] | Owner-Occupied [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	1,282,657	963,503
Pass [Member] | Nonowner-Occupied [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	4,544,799	3,284,497
Pass [Member] | Construction & Land Development [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	1,498,656	1,126,742
Special Mention [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	18,953	18,240
Special Mention [Member] | Other Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	47,450	26,537
Special Mention [Member] | Bankcard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	385	422
Special Mention [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	8,134	10,132
Special Mention [Member] | Owner-Occupied [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	23,827	20,490
Special Mention [Member] | Nonowner-Occupied [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	44,080	36,462
Special Mention [Member] | Construction & Land Development [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	19,872	52,327
Substandard [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	32,301	36,995
Substandard [Member] | Other Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	98,933	122,893
Substandard [Member] | Bankcard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	210	141
Substandard [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	1,317	1,746
Substandard [Member] | Owner-Occupied [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	58,273	65,892
Substandard [Member] | Nonowner-Occupied [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	97,304	104,494
Substandard [Member] | Construction & Land Development [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	81,104	76,669
Doubtful [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	0	185
Doubtful [Member] | Other Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, credit quality indicators information	108	210
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, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Construction & Land Development [Member]
Financing Receivable, Impaired [Line Items]
Impaired Loans, Recorded Investment, With no related allowance recorded	$ 30,959		$ 30,959		$ 19,863
Impaired Loans, Unpaid Principal Balance, With no related allowance recorded	33,225		33,225		21,746
Impaired Loans, Recorded Investment, With an allowance recorded	1,411		1,411		4,940
Impaired Loans, Unpaid Principal Balance, With an allowance recorded	5,910		5,910		7,899
Impaired Loans, Related Allowance	488		488		3,206
Impaired Loans, Recorded Investment	32,370		32,370		24,803
Impaired Loans, Unpaid Principal Balance	39,135		39,135		29,645
Impaired Loans, Related Allowance	488		488		3,206
Impaired Loans, Average Recorded Investment, With no related allowance recorded	23,846	$ 28,730	20,706	$ 26,559
Impaired Loans, Interest Income Recognized, With no related allowance recorded	552	46	563	112
Impaired Loans, Average Recorded Investment, With an allowance recorded	1,641	8,591	2,872	10,300
Impaired Loans, Interest Income Recognized, With an allowance recorded	21	56	64	146
Impaired Loans, Average Recorded Investment	25,487	37,321	23,578	36,859
Impaired Loans, Interest Income Recognized	573	102	627	258
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	25	35	29	32
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	64,592		64,592		46,575
Impaired Loans, Unpaid Principal Balance, With no related allowance recorded	65,355		65,355		47,108
Impaired Loans, Recorded Investment, With an allowance recorded	8,220		8,220		1,787
Impaired Loans, Unpaid Principal Balance, With an allowance recorded	8,220		8,220		2,082
Impaired Loans, Related Allowance	923		923		815
Impaired Loans, Recorded Investment	72,812		72,812		48,362
Impaired Loans, Unpaid Principal Balance	73,575		73,575		49,190
Impaired Loans, Related Allowance	923		923		815
Impaired Loans, Average Recorded Investment, With no related allowance recorded	58,980	38,199	55,506	34,030
Impaired Loans, Interest Income Recognized, With no related allowance recorded	376	531	1,011	715
Impaired Loans, Average Recorded Investment, With an allowance recorded	11,624	3,353	9,392	3,603
Impaired Loans, Interest Income Recognized, With an allowance recorded	131	36	424	92
Impaired Loans, Average Recorded Investment	70,604	41,552	64,898	37,633
Impaired Loans, Interest Income Recognized	507	567	1,435	807
Commercial Real Estate [Member] | Nonowner-Occupied [Member]
Financing Receivable, Impaired [Line Items]
Impaired Loans, Recorded Investment, With no related allowance recorded	143,100		143,100		92,654
Impaired Loans, Unpaid Principal Balance, With no related allowance recorded	143,552		143,552		93,104
Impaired Loans, Recorded Investment, With an allowance recorded	12,182		12,182		17,938
Impaired Loans, Unpaid Principal Balance, With an allowance recorded	12,182		12,182		17,938
Impaired Loans, Related Allowance	1,786		1,786		2,524
Impaired Loans, Recorded Investment	155,282		155,282		110,592
Impaired Loans, Unpaid Principal Balance	155,734		155,734		111,042
Impaired Loans, Related Allowance	1,786		1,786		2,524
Impaired Loans, Average Recorded Investment, With no related allowance recorded	108,959	71,154	93,254	70,081
Impaired Loans, Interest Income Recognized, With no related allowance recorded	312	321	811	714
Impaired Loans, Average Recorded Investment, With an allowance recorded	13,408	14,046	14,595	10,416
Impaired Loans, Interest Income Recognized, With an allowance recorded	89	122	363	360
Impaired Loans, Average Recorded Investment	122,367	85,200	107,849	80,497
Impaired Loans, Interest Income Recognized	401	443	1,174	1,074
Other Commercial [Member]
Financing Receivable, Impaired [Line Items]
Impaired Loans, Recorded Investment, With no related allowance recorded	55,022		55,022		46,064
Impaired Loans, Unpaid Principal Balance, With no related allowance recorded	58,785		58,785		48,308
Impaired Loans, Recorded Investment, With an allowance recorded	70,344		70,344		43,774
Impaired Loans, Unpaid Principal Balance, With an allowance recorded	80,415		80,415		46,188
Impaired Loans, Related Allowance	21,890		21,890		13,441
Impaired Loans, Recorded Investment	125,366		125,366		89,838
Impaired Loans, Unpaid Principal Balance	139,200		139,200		94,496
Impaired Loans, Related Allowance	21,890		21,890		13,441
Impaired Loans, Average Recorded Investment, With no related allowance recorded	57,317	45,028	55,891	37,805
Impaired Loans, Interest Income Recognized, With no related allowance recorded	306	1,221	895	1,446
Impaired Loans, Average Recorded Investment, With an allowance recorded	72,835	33,195	65,142	34,755
Impaired Loans, Interest Income Recognized, With an allowance recorded	216	42	1,410	270
Impaired Loans, Average Recorded Investment	130,152	78,223	121,033	72,560
Impaired Loans, Interest Income Recognized	522	1,263	2,305	1,716
Residential Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired Loans, Recorded Investment, With no related allowance recorded	20,873		20,873		22,747
Impaired Loans, Unpaid Principal Balance, With no related allowance recorded	22,546		22,546		24,404
Impaired Loans, Recorded Investment, With an allowance recorded	13,743		13,743		12,066
Impaired Loans, Unpaid Principal Balance, With an allowance recorded	15,082		15,082		12,801
Impaired Loans, Related Allowance	1,659		1,659		3,431
Impaired Loans, Recorded Investment	34,616		34,616		34,813
Impaired Loans, Unpaid Principal Balance	37,628		37,628		37,205
Impaired Loans, Related Allowance	1,659		1,659		3,431
Impaired Loans, Average Recorded Investment, With no related allowance recorded	19,553	27,214	19,634	26,737
Impaired Loans, Interest Income Recognized, With no related allowance recorded	74	170	206	406
Impaired Loans, Average Recorded Investment, With an allowance recorded	15,225	8,579	15,186	9,129
Impaired Loans, Interest Income Recognized, With an allowance recorded	16	52	89	77
Impaired Loans, Average Recorded Investment	34,778	35,793	34,820	35,866
Impaired Loans, Interest Income Recognized	90	222	295	483
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	16		16		36
Impaired Loans, Unpaid Principal Balance, With no related allowance recorded	16		16		36
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	16		16		36
Impaired Loans, Unpaid Principal Balance	16		16		36
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	25	35	29	32
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
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Financing Receivable, Allowance for Credit Losses [Line Items]
Specific loss allocations are calculated for commercial loans in excess			$ 500,000
Number of days for collecting principal or interest on consumer loans			90 days
Minimum collection period for home equity loan or high loan to value loan			180 days
Retail credits amount deemed unrecoverable charged-off period			60 days
Retail credits charged off period after discovery of the fraud			90 days
Reversal of provision for loan losses related to loans acquired	$ 43,000	$ 1,130,000	$ 415,000	$ 160,000
Reserve for lending-related commitments	$ 804,000		$ 804,000		$ 1,044,000
Closed-End Retail Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Number of days delinquent from contractual due date			120 days
Open-End Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Number of days delinquent from contractual due date			180 days

Allowance for Credit Losses - S

Allowance for Credit Losses - Schedule of Allowance for Loan Losses and Carrying Amount of Loans (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses Beginning balance	$ 72,983		$ 72,771	$ 75,726	$ 75,726
Charge-offs	6,357		23,564		36,180
Recoveries	1,021		4,290		8,716
Provision	7,279	$ 6,988	21,429	18,690	24,509
Allowance for Loan Losses Ending balance	74,926		74,926		72,771
Allowance for Loan Losses, individually evaluated for impairment	26,746		26,746		23,417
Allowance for Loan Losses, collectively evaluated for impairment	48,180		48,180		49,354
Financing receivables	13,156,854		13,156,854		10,356,719
Financing receivables, individually evaluated for impairment	180,120		180,120		124,820
Financing receivables, collectively evaluated for impairment	12,748,980		12,748,980		10,060,303
Loans Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses	0		0		0
Financing receivables	227,754		227,754		171,596
Construction & Land Development [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses Beginning balance	7,514		10,606	18,205	18,205
Charge-offs	54		2,576		2,659
Recoveries	89		705		433
Provision	452		(734)		(5,373)
Allowance for Loan Losses Ending balance	8,001		8,001		10,606
Allowance for Loan Losses, individually evaluated for impairment	488		488		3,206
Allowance for Loan Losses, collectively evaluated for impairment	7,513		7,513		7,400
Financing receivables	1,599,632		1,599,632		1,255,738
Financing receivables, individually evaluated for impairment	16,879		16,879		8,152
Financing receivables, collectively evaluated for impairment	1,558,653		1,558,653		1,221,006
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	24,100		24,100		26,580
Allowance for Estimated Imprecision [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses Beginning balance	760		347	104	104
Charge-offs	0		0		0
Recoveries	0		0		0
Provision	(609)		(196)		243
Allowance for Loan Losses Ending balance	151		151		347
Allowance for Loan Losses, individually evaluated for impairment	0		0		0
Allowance for Loan Losses, collectively evaluated for impairment	151		151		347
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	5,129		5,273	3,637	3,637
Charge-offs	518		1,433		5,281
Recoveries	397		1,590		3,071
Provision	230		(192)		3,846
Allowance for Loan Losses Ending balance	5,238		5,238		5,273
Allowance for Loan Losses, individually evaluated for impairment	923		923		815
Allowance for Loan Losses, collectively evaluated for impairment	4,315		4,315		4,458
Financing receivables	1,364,757		1,364,757		1,049,885
Financing receivables, individually evaluated for impairment	32,888		32,888		18,976
Financing receivables, collectively evaluated for impairment	1,297,668		1,297,668		1,005,999
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	34,201		34,201		24,910
Commercial Real Estate [Member] | Nonowner-Occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses Beginning balance	7,099		6,883	5,309	5,309
Charge-offs	0		295		419
Recoveries	168		198		675
Provision	(472)		9		1,318
Allowance for Loan Losses Ending balance	6,795		6,795		6,883
Allowance for Loan Losses, individually evaluated for impairment	1,786		1,786		2,524
Allowance for Loan Losses, collectively evaluated for impairment	5,009		5,009		4,359
Financing receivables	4,686,183		4,686,183		3,425,453
Financing receivables, individually evaluated for impairment	25,220		25,220		26,835
Financing receivables, collectively evaluated for impairment	4,537,792		4,537,792		3,323,117
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	123,171		123,171		75,501
Other Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses Beginning balance	37,287		33,087	31,328	31,328
Charge-offs	4,854		14,883		20,430
Recoveries	156		821		3,452
Provision	8,782		22,346		18,737
Allowance for Loan Losses Ending balance	41,371		41,371		33,087
Allowance for Loan Losses, individually evaluated for impairment	21,890		21,890		13,441
Allowance for Loan Losses, collectively evaluated for impairment	19,481		19,481		19,646
Financing receivables	1,757,741		1,757,741		1,613,437
Financing receivables, individually evaluated for impairment	89,559		89,559		56,091
Financing receivables, collectively evaluated for impairment	1,636,037		1,636,037		1,527,479
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	32,145		32,145		29,867
Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses Beginning balance	12,479		13,770	15,148	15,148
Charge-offs	299		2,331		4,597
Recoveries	60		352		639
Provision	(1,385)		(936)		2,580
Allowance for Loan Losses Ending balance	10,855		10,855		13,770
Allowance for Loan Losses, individually evaluated for impairment	1,659		1,659		3,431
Allowance for Loan Losses, collectively evaluated for impairment	9,196		9,196		10,339
Financing receivables	3,050,868		3,050,868		2,403,437
Financing receivables, individually evaluated for impairment	15,574		15,574		14,766
Financing receivables, collectively evaluated for impairment	3,021,173		3,021,173		2,373,969
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	14,121		14,121		14,702
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses Beginning balance	2,715		2,805	$ 1,995	1,995
Charge-offs	632		2,046		2,794
Recoveries	151		624		446
Provision	281		1,132		3,158
Allowance for Loan Losses Ending balance	2,515		2,515		2,805
Allowance for Loan Losses, individually evaluated for impairment	0		0		0
Allowance for Loan Losses, collectively evaluated for impairment	2,515		2,515		2,805
Financing receivables	697,673		697,673		608,769
Financing receivables, individually evaluated for impairment	0		0		0
Financing receivables, collectively evaluated for impairment	697,657		697,657		608,733
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	$ 16		$ 16		$ 36

Intangible Assets - Summary of

Intangible Assets - Summary of Intangible Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Goodwill not subject to amortization	$ 1,487,607	$ 863,767
Community Banking [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill not subject to amortization	1,466,152	863,767
Mortgage Banking [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill not subject to amortization	21,455	0
Core Deposit Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	98,358	69,635
Accumulated Amortization	(52,062)	(46,681)
Core Deposit Intangible Assets [Member] | Community Banking [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	98,358	69,635
Accumulated Amortization	(52,062)	$ (46,681)
Core Deposit Intangible Assets [Member] | Mortgage Banking [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	0
Accumulated Amortization	0
George Mason Trade Name Intangible [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,230
George Mason Trade Name Intangible [Member] | Community Banking [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	0
George Mason Trade Name Intangible [Member] | Mortgage Banking [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 1,230

Intangible Assets - Reconciliat

Intangible Assets - Reconciliation of Goodwill (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2017USD ($)
Goodwill [Line Items]
Goodwill, Beginning Balance	$ 863,767
Goodwill, Ending Balance	1,487,607
Bank of Georgetown [Member]
Goodwill [Line Items]
Addition to goodwill	1,327
Cardinal Financial Corporation [Member]
Goodwill [Line Items]
Addition to goodwill	622,513
Community Banking [Member]
Goodwill [Line Items]
Goodwill, Beginning Balance	863,767
Goodwill, Ending Balance	1,466,152
Community Banking [Member] | Bank of Georgetown [Member]
Goodwill [Line Items]
Addition to goodwill	1,327
Community Banking [Member] | Cardinal Financial Corporation [Member]
Goodwill [Line Items]
Addition to goodwill	601,058
Mortgage Banking [Member]
Goodwill [Line Items]
Goodwill, Beginning Balance	0
Goodwill, Ending Balance	21,455
Mortgage Banking [Member] | Bank of Georgetown [Member]
Goodwill [Line Items]
Addition to goodwill	0
Mortgage Banking [Member] | Cardinal Financial Corporation [Member]
Goodwill [Line Items]
Addition to goodwill	$ 21,455

Intangible Assets - Additional

Intangible Assets - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Intangible Liability Disclosure [Abstract]
Amortization expense on intangible assets	$ 2,240	$ 1,122	$ 5,381	$ 2,786

Intangible Assets - Schedule of

Intangible Assets - Schedule of Anticipated Amortization Expense (Detail) $ in Thousands	Sep. 30, 2017USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
2,017	$ 7,772
2,018	8,039
2,019	7,015
2,020	6,309
2021 and thereafter	$ 22,542

Short-Term Borrowings - Additio

Short-Term Borrowings - Additional Information (Detail) - USD ($)	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Short-term Debt [Line Items]
Unused lines of credit	$ 264,000,000
Federal funds purchased	25,800,000	$ 22,235,000
Repurchase agreements	316,236,000
Wholesale REPO	$ 50,000,000
Maturity date of wholesale REPO	2018-05
Unrelated Financial Institution [Member]
Short-term Debt [Line Items]
Unused lines of credit	$ 20,000,000
Renewal period of line of credit	360 days
Amount of outstanding balance under line of credit	$ 0

Long-Term Borrowings - Addition

Long-Term Borrowings - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2017USD ($)Trust	Jun. 30, 2017USD ($)	Apr. 21, 2017USD ($)	Dec. 31, 2016USD ($)
Debt Instrument [Line Items]
Unused borrowing amount	$ 3,724,772,000
FHLB advances	$ 1,272,115,000			$ 897,707,000
FHLB advances, weighted-average interest rate	1.43%
FHLB advances, maximum maturity period	8 years
Overnight funds	$ 200,000,000
Acquisition accounting adjustment to fair value, interest rate	1.27%
Number of statutory business trusts | Trust	15
Outstanding balances of debentures	$ 242,131,000			$ 224,319,000
Maximum time to defer payment of interest on subordinate debt	5 years
Trust Preferred Securities limit percentage	25.00%
Maximum [Member]
Debt Instrument [Line Items]
Risk based assets		$ 15,000,000,000
Cardinal Financial Corporation [Member] | Minimum [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	15

Long -Term Borrowings - Schedul

Long -Term Borrowings - Schedule of Maturities of FHLB Borrowings (Detail) $ in Thousands	Sep. 30, 2017USD ($)
Debt Disclosure [Abstract]
2,017	$ 815,000
2,018	131,776
2,019	187,809
2,020	42,247
2021 and thereafter	95,283
Total	$ 1,272,115

Commitments and Contingent Li79

Commitments and Contingent Liabilities - Additional Information (Detail) - USD ($)	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Loss Contingencies [Line Items]
Loan commitments outstanding	$ 4,118,868,000	$ 2,823,396,000
Loan commitments expiry period	1 year
George Mason [Member]
Loss Contingencies [Line Items]
Aggregate available reserve amount under specified circumstances	$ 575,000
Commitments to Extend Credit [Member] | George Mason [Member] | Short-term Contract with Customer [Member]
Loss Contingencies [Line Items]
Additional commitments to extend credit	407,610,000
Commercial Letters of Credit [Member]
Loss Contingencies [Line Items]
Letters of credit issued	0	9,000
Standby Letters of Credit [Member]
Loss Contingencies [Line Items]
Letters of credit issued	$ 148,742,000	$ 121,584,000

Derivative Financial Instrume80

Derivative Financial Instruments - Schedule of Notional Amount and Fair Value of Derivative Financial Instruments (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Derivative [Line Items]
Asset derivatives, notional amount	$ 506,850
Asset derivatives designated as hedging instruments	40	$ 24
Liability derivatives, notional amount	192,794
Asset derivatives not designated as hedging instruments	7,528	2,267
Total asset derivatives	7,568	2,291
Liability derivatives designated as hedging instruments	480	338
Liability derivatives not designated as hedging instruments	548	2,267
Total liability derivatives	1,028	2,605
Designated as Hedging Instrument [Member]
Derivative [Line Items]
Asset derivatives, notional amount	14,762
Liability derivatives, notional amount	76,869
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Asset derivatives, notional amount	492,088
Liability derivatives, notional amount	115,925
Other Assets [Member] | TBA Mortgage Backed Securities [Member]
Derivative [Line Items]
Asset derivatives not designated as hedging instruments	501	0
Other Assets [Member] | Interest Rate Lock Commitments [Member]
Derivative [Line Items]
Asset derivatives not designated as hedging instruments	7,027	0
Other Assets [Member] | Not Designated as Hedging Instrument [Member] | TBA Mortgage Backed Securities [Member]
Derivative [Line Items]
Asset derivatives, notional amount	322,500
Other Assets [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Lock Commitments [Member]
Derivative [Line Items]
Asset derivatives, notional amount	169,588
Other Liabilities [Member] | Interest Rate Lock Commitments [Member]
Derivative [Line Items]
Liability derivatives not designated as hedging instruments	291	0
Other Liabilities [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Lock Commitments [Member]
Derivative [Line Items]
Liability derivatives, notional amount	65,862
Interest Rate Swap Contracts [Member] | Other Assets [Member]
Derivative [Line Items]
Asset derivatives not designated as hedging instruments	0	2,267
Interest Rate Swap Contracts [Member] | Other Assets [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Asset derivatives, notional amount	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	40	24
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	14,762
Interest Rate Swap Contracts [Member] | Other Liabilities [Member]
Derivative [Line Items]
Liability derivatives not designated as hedging instruments	0	2,267
Interest Rate Swap Contracts [Member] | Other Liabilities [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Liability derivatives, notional amount	0
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	480	338
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	76,869
Forward Loan Sale Commitments [Member] | Other Liabilities [Member]
Derivative [Line Items]
Liability derivatives not designated as hedging instruments	257	$ 0
Forward Loan Sale Commitments [Member] | Other Liabilities [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Liability derivatives, notional amount	$ 50,063

Derivative Financial Instrume81

Derivative Financial Instruments - Schedule of Derivative Financial Instruments on Statement of Income (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Derivative [Line Items]
Derivatives in hedging relationships	$ (4,826)	$ (385)	$ (1,633)	$ 353
Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivatives in hedging relationships	(208)	(385)	(648)	353
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	(208)	(385)	(648)	353
Designated as Hedging Instrument [Member] | Other Income [Member] | Forward Loan Sale Commitments [Member] | Cash Flow Hedges [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	(4,618)	0	(985)	0
Not Designated as Hedging Instrument [Member] | Income from Mortgage Banking Activities [Member] | TBA Mortgage Backed Securities [Member]
Derivative [Line Items]
Derivatives not designated as hedging instruments	123	0	2,907	0
Not Designated as Hedging Instrument [Member] | Income from Mortgage Banking Activities [Member] | Interest Rate Lock Commitments [Member]
Derivative [Line Items]
Derivatives not designated as hedging instruments	4,484	0	3,465	0
Not Designated as Hedging Instrument [Member] | Income from Mortgage Banking Activities [Member] | Forward Loan Sale Commitments [Member]
Derivative [Line Items]
Derivatives not designated as hedging instruments	$ 257	$ 0	$ 427	$ 0

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($)	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Discount rates utilized, minimum	3.25%
Discount rates utilized, maximum	6.00%
Amount of decrease in fair value of securities	$ 5,741,000
Transfers from Level 1 to Level 2 for financial assets	0	$ 0
Transfers from Level 2 to Level 1 for financial assets	0	0
Transfers from Level 1 to Level 2 for financial liabilities	0	0
Transfers from Level 2 to Level 1 for financial liabilities	0	$ 0
Nonrecurring fair value adjustments on loans held for sale	0
Fair value measurement of intangible assets	$ 0		$ 0
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	0.27%
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	0.40%
Loans Held For Sale [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Sales price of loans held for sale increase percentage	0.36%
Derivatives [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Sales price of loans held for sale increase percentage	0.27%
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	0.40%
Derivatives [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Sales price of loans held for sale increase percentage	0.36%
Trust Preferred Collateralized Debt Obligations [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Decrease in fair value of securities	18.00%
Increase in discount rates, basis point	2.00%

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Financial Assets and Liabilities Measured at Fair Value (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale equity securities	$ 10,480	$ 13,828
Total available for sale securities	1,649,634	1,259,214
Loans held for sale	315,031	8,445
Derivative financial assets	7,568	2,291
Derivative financial liabilities	1,028	2,605
Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	1,639,154	1,245,386
Available for sale equity securities	10,480	13,828
Total available for sale securities	1,649,634	1,259,214
Loans held for sale	311,186
Derivative financial assets	7,568
Derivative financial liabilities	1,028
Fair Value, Measurements, Recurring [Member] | Interest Rate Lock Commitments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative financial assets	7,027
Derivative financial liabilities	291
Fair Value, Measurements, Recurring [Member] | TBA Mortgage Backed Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative financial assets	501
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	115,866	95,786
U.S. Treasury Securities and Obligations of U.S. Government Corporations and Agencies [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	115,866	95,786
State and Political Subdivisions [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	305,141	192,812
State and Political Subdivisions [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	305,141	192,812
Residential Mortgage-Backed Securities, Agency [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	714,700	584,096
Residential Mortgage-Backed Securities, Agency [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	714,700	584,096
Residential Mortgage-Backed Securities, Non-agency [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	5,846	7,043
Residential Mortgage-Backed Securities, Non-agency [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	5,846	7,043
Asset-Backed Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	13,429	217
Asset-Backed Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	13,429	217
Commercial Mortgage-Backed Securities, Agency [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	420,792	305,341
Commercial Mortgage-Backed Securities, Agency [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	420,792	305,341
Trust Preferred Collateralized Debt Obligations [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	31,659	33,552
Trust Preferred Collateralized Debt Obligations [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	31,659	33,552
Single Issue Trust Preferred Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	12,467	11,477
Single Issue Trust Preferred Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	12,467	11,477
Corporate Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	19,254	15,062
Corporate Bonds [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	19,254	15,062
Financial Services Industry [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale equity securities	3,016	10,735
Other Equity Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale equity securities	1,214	1,273
Interest Rate Swap Contracts [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative financial assets	40	2,291
Derivative financial liabilities	480	2,605
Forward Loan Sale Commitments [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative financial liabilities	257
Equity Mutual Funds [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale equity securities	6,250	1,820
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	7,865	4,465
Loans held for sale	0	0
Derivative financial assets	501	0
Derivative financial liabilities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	0	0
Available for sale equity securities	7,865	4,465
Total available for sale securities	7,865	4,465
Loans held for sale	0
Derivative financial assets	501
Derivative financial liabilities	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate Lock Commitments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative financial assets	0
Derivative financial liabilities	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	501
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | U.S. Treasury Securities and Obligations of U.S. Government Corporations and Agencies [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | State and Political Subdivisions [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Residential Mortgage-Backed Securities, Agency [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Residential Mortgage-Backed Securities, Non-agency [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Asset-Backed Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Commercial Mortgage-Backed Securities, Agency [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Trust Preferred Collateralized Debt Obligations [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Single Issue Trust Preferred Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Corporate Bonds [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Financial Services Industry [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale equity securities	401	1,372
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Equity Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale equity securities	1,214	1,273
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	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 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	6,250	1,820
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	1,610,110	1,221,197
Loans held for sale	3,845	8,445
Derivative financial assets	40	2,291
Derivative financial liabilities	1,028	2,605
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	1,607,495	1,211,834
Available for sale equity securities	2,615	9,363
Total available for sale securities	1,610,110	1,221,197
Loans held for sale	0
Derivative financial assets	40
Derivative financial liabilities	1,028
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
Derivative financial liabilities	291
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	0
Significant Other Observable Inputs (Level 2) [Member] | U.S. Treasury Securities and Obligations of U.S. Government Corporations and Agencies [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	115,866	95,786
Significant Other Observable Inputs (Level 2) [Member] | State and Political Subdivisions [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	305,141	192,812
Significant Other Observable Inputs (Level 2) [Member] | Residential Mortgage-Backed Securities, Agency [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	714,700	584,096
Significant Other Observable Inputs (Level 2) [Member] | Residential Mortgage-Backed Securities, Non-agency [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	5,846	7,043
Significant Other Observable Inputs (Level 2) [Member] | Asset-Backed Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	13,429	217
Significant Other Observable Inputs (Level 2) [Member] | Commercial Mortgage-Backed Securities, Agency [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	420,792	305,341
Significant Other Observable Inputs (Level 2) [Member] | Trust Preferred Collateralized Debt Obligations [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	0	0
Significant Other Observable Inputs (Level 2) [Member] | Single Issue Trust Preferred Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	12,467	11,477
Significant Other Observable Inputs (Level 2) [Member] | Corporate Bonds [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	19,254	15,062
Significant Other Observable Inputs (Level 2) [Member] | Financial Services Industry [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale equity securities	2,615	9,363
Significant Other Observable Inputs (Level 2) [Member] | Other Equity Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale equity securities	0	0
Significant Other Observable Inputs (Level 2) [Member] | Interest Rate Swap Contracts [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative financial assets	40	2,291
Derivative financial liabilities	480	2,605
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 liabilities	257
Significant Other Observable Inputs (Level 2) [Member] | Equity Mutual Funds [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale equity securities	0	0
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available for sale securities	31,659	33,552
Loans held for sale	311,186	0
Derivative financial assets	7,027	0
Derivative financial liabilities	0	0
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	31,659	33,552
Available for sale equity securities	0	0
Total available for sale securities	31,659	33,552
Loans held for sale	311,186
Derivative financial assets	7,027
Derivative financial liabilities	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	7,027
Derivative financial liabilities	0
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
Significant Unobservable Inputs (Level 3) [Member] | U.S. Treasury Securities and Obligations of U.S. Government Corporations and Agencies [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	0	0
Significant Unobservable Inputs (Level 3) [Member] | State and Political Subdivisions [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	0	0
Significant Unobservable Inputs (Level 3) [Member] | Residential Mortgage-Backed Securities, Agency [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	0	0
Significant Unobservable Inputs (Level 3) [Member] | Residential Mortgage-Backed Securities, Non-agency [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	0	0
Significant Unobservable Inputs (Level 3) [Member] | Asset-Backed Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	0	0
Significant Unobservable Inputs (Level 3) [Member] | Commercial Mortgage-Backed Securities, Agency [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	0	0
Significant Unobservable Inputs (Level 3) [Member] | Trust Preferred Collateralized Debt Obligations [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	31,659	33,552
Significant Unobservable Inputs (Level 3) [Member] | Single Issue Trust Preferred Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	0	0
Significant Unobservable Inputs (Level 3) [Member] | Corporate Bonds [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale debt securities	0	0
Significant Unobservable Inputs (Level 3) [Member] | Financial Services Industry [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale equity securities	0	0
Significant Unobservable Inputs (Level 3) [Member] | Other Equity Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale equity securities	0	0
Significant Unobservable Inputs (Level 3) [Member] | Interest Rate 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	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 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	$ 0

Fair Value Measurements - Sch84

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, 2017	Dec. 31, 2016
Trust Preferred Collateralized Debt Obligations [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Balance, beginning of period	$ 33,552	$ 34,686
Sales	(8,050)	0
Included in earnings (or changes in net assets)	9	0
Included in other comprehensive income	6,148	(1,134)
Balance, end of period	31,659	33,552
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	0	0
Acquired in Cardinal merger	271,301	0
Originations	1,644,943	0
Sales	(1,639,737)	0
Included in earnings (or changes in net assets)	41,929	0
Transfers in and/or out of Level 3	(7,250)	0
Balance, end of period	311,186	0
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	0	0
Acquired in Cardinal merger	10,393	0
Transfers in and/or out of Level 3	(3,366)	0
Balance, end of period	7,027	0
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 - Sch85

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, 2017	Sep. 30, 2017
Mortgage Banking [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Income from mortgage banking activities	$ (5,090)	$ (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, 2017	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Loans held for sale, unpaid principal balance	$ 303,953	$ 0
Loans held for sale, fair value	311,186	0
Loans held for sale, fair value over/(under) unpaid principal balance	$ 7,233	$ 0

Fair Value Measurements - Sum87

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, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
YTD Losses, Impaired Loans	$ 9,045	$ 5,119
YTD Losses, OREO	2,904	2,086
Impaired Loans	105,900	80,505
OREO	26,826	31,510
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Impaired Loans	0	0
OREO	0	0
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Impaired Loans	74,852	27,609
OREO	26,743	31,510
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Impaired Loans	31,048	52,896
OREO	$ 83	$ 0

Fair Value Measurements - Sum88

Fair Value Measurements - Summary of Estimated Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 1,747,037	$ 1,434,527	$ 1,118,506	$ 857,335
Securities available for sale	1,649,634	1,259,214
Securities held to maturity	20,335	33,258
Other securities	166,756	111,166
Loans held for sale	315,031	8,445
Loans	13,140,468	10,341,137
Derivative financial assets	7,568	2,291
Deposits	13,875,297	10,796,867
Derivative financial liabilities	1,028	2,605
Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	1,747,037	1,434,527
Securities available for sale	1,649,634	1,259,214
Securities held to maturity	20,335	33,258
Other securities	166,756	111,166
Loans held for sale	315,031	8,445
Loans	13,065,542	10,268,366
Derivative financial assets	7,568	2,291
Deposits	13,875,297	10,796,867
Short-term borrowings	492,036	209,551
Long-term borrowings	1,364,246	1,172,026
Derivative financial liabilities	1,028	2,605
Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	1,747,037	1,434,527
Securities available for sale	1,649,634	1,259,214
Securities held to maturity	19,909	31,178
Other securities	158,418	105,608
Loans held for sale	315,031	8,445
Loans	12,550,352	10,122,486
Derivative financial assets	7,568	2,291
Deposits	13,859,205	10,785,294
Short-term borrowings	492,036	209,551
Long-term borrowings	1,328,753	1,142,782
Derivative financial liabilities	1,028	2,605
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	0	0
Securities available for sale	7,865	4,465
Securities held to maturity	0	0
Other securities	0	0
Loans held for sale	0	0
Loans	0	0
Derivative financial assets	501	0
Deposits	0	0
Short-term borrowings	0	0
Long-term borrowings	0	0
Derivative financial liabilities	0	0
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	1,747,037	1,434,527
Securities available for sale	1,610,110	1,221,197
Securities held to maturity	16,889	28,158
Other securities	0	0
Loans held for sale	3,845	8,445
Loans	0	0
Derivative financial assets	40	2,291
Deposits	13,859,205	10,785,294
Short-term borrowings	492,036	209,551
Long-term borrowings	1,328,753	1,142,782
Derivative financial liabilities	1,028	2,605
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	31,659	33,552
Securities held to maturity	3,020	3,020
Other securities	158,418	105,608
Loans held for sale	311,186	0
Loans	12,550,352	10,122,486
Derivative financial assets	7,027	0
Deposits	0	0
Short-term borrowings	0	0
Long-term borrowings	0	0
Derivative financial liabilities	$ 0	$ 0

Stock Based Compensation - Addi

Stock Based Compensation - Additional Information (Detail) - USD ($) $ in Thousands	May 18, 2016	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
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				253,417
Recognition of compensation expense		$ 909	$ 720	$ 2,589	$ 2,050
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				163,562	248,677
Total intrinsic value of options exercised				$ 3,078	$ 4,670
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares granted				89,475
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, 2017	Sep. 30, 2016
Schedule Of Stock Options [Line Items]
Shares, Outstanding, Beginning balance	1,411,735
Shares, Granted	253,417
Shares, Exercised	(163,562)	(248,677)
Shares, Forfeited or expired	(2,962)
Shares, Outstanding, Ending balance	1,652,230
Shares, Exercisable at September 30, 2017	1,138,309
Aggregate Intrinsic Value, Outstanding at September 30, 2017	$ 12,602
Aggregate Intrinsic Value, Exercisable at September 30, 2017	$ 11,964
Weighted Average Remaining Contractual Term, Outstanding at June 30, 2017	5 years 9 months 18 days
Weighted Average Remaining Contractual Term, Exercisable at June 30, 2017	4 years 6 months
Weighted Average Exercise Price, Outstanding, Beginning balance	$ 28.05
Weighted Average Exercise Price, Granted	45.27
Weighted Average Exercise Price, Exercised	20.93
Weighted Average Exercise Price, Forfeited or expired	38.81
Weighted Average Exercise Price, Outstanding, Ending balance	30.76
Weighted Average Exercise Price, Exercisable	$ 26.64
Cardinal Financial Corporation [Member]
Schedule Of Stock Options [Line Items]
Shares, Assumed in Cardinal merger	153,602
Weighted Average Exercise Price, Exercisable	$ 21.47

Stock Based Compensation - Stat

Stock Based Compensation - Status of United's Nonvested Stock Option Awards (Detail)	9 Months Ended
	Sep. 30, 2017$ / sharesshares
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Shares, Nonvested, Beginning balance | shares	430,278
Shares, Granted | shares	253,417
Shares, Vested | shares	(168,274)
Shares, Forfeited or expired | shares	(1,500)
Shares, Nonvested, Ending balance | shares	513,921
Weighted-Average Grant Date Fair Value Per Share, Nonvested Beginning balance | $ / shares	$ 6.84
Weighted-Average Grant Date Fair Value Per Share, Granted | $ / shares	8.85
Weighted-Average Grant Date Fair Value Per Share, Vested | $ / shares	6.64
Weighted-Average Grant Date Fair Value Per Share, Forfeited or expired | $ / shares	8.85
Weighted-Average Grant Date Fair Value Per Share, Nonvested Ending balance | $ / shares	$ 7.89

Stock Based Compensation - Chan

Stock Based Compensation - Changes to United's Restricted Common Shares (Detail) - Restricted Stock [Member]	9 Months Ended
	Sep. 30, 2017$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Outstanding, Beginning balance | shares	137,268
Shares, Granted | shares	89,475
Shares, Vested | shares	(53,950)
Shares, Forfeited | shares	(420)
Number of Shares, Outstanding, Ending balance | shares	172,373
Weighted-Average Grant Date Fair Value Per Share, Outstanding, Beginning balance | $ / shares	$ 33.61
Weighted-Average Grant Date Fair Value Per Share, Granted | $ / shares	45.27
Weighted-Average Grant Date Fair Value Per Share, Vested | $ / shares	32.23
Weighted-Average Grant Date Fair Value Per Share, Forfeited | $ / shares	45.30
Weighted-Average Grant Date Fair Value Per Share, Outstanding, Ending balance | $ / shares	$ 40.07

Employee Benefit Plans - Additi

Employee Benefit Plans - Additional Information (Detail) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2017USD ($)	Sep. 30, 2017USD ($)
Retirement Benefits [Abstract]
Employer discretionary contribution amount	$ 10,000
Net periodic pension cost decline in expense	252	$ 748
Unrecognized actuarial gains (losses), before tax	53,991	53,991
Unrecognized actuarial gains (losses), net of tax	34,014	34,014
Amortization expected to be recognized	$ 4,411	4,411
Amortization expected to be recognized, net of tax		$ 2,779

Employee Benefit Plans - Net Pe

Employee Benefit Plans - Net Periodic Pension Cost (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 574	$ 614	$ 1,705	$ 1,829
Interest cost	1,293	1,471	3,837	4,383
Expected return on plan assets	(2,072)	(2,034)	(6,148)	(6,058)
Recognized net actuarial loss	1,111	1,161	3,298	3,458
Net periodic pension (benefit) cost	$ 906	$ 1,212	$ 2,692	$ 3,612
Weighted-Average Assumptions:
Discount rate	4.49%	4.75%	4.49%	4.75%
Expected return on assets	7.00%	7.25%	7.00%	7.25%
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	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Income Tax Disclosure [Abstract]
Estimate of unrecognized tax benefits, reasonable possible	United cannot reasonably estimate the amount of tax benefits it may recognize over the next 12 months.
Liability of unrecognized tax benefits	$ 2,405
Accrued interest related to uncertain tax positions	$ 548	$ 792

Comprehensive Income - Componen

Comprehensive Income - Components of Total Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Net income	$ 56,738	$ 41,479	$ 132,606	$ 107,977
AFS securities with OTTI charges during the period	0	0	(60)	(77)
Related income tax effect	0	0	22	28
Less: OTTI charges recognized in net income	0	0	60	33
Related income tax benefit	0	0	(22)	(12)
Reclassification of previous noncredit OTTI to credit OTTI	0	0	0	415
Related income tax benefit	0	0	0	(150)
Net unrealized (losses) gains on AFS securities with OTTI	0	0	0	237
Change in net unrealized gain on AFS securities arising during the period	3,584	(7,599)	14,846	12,356
Related income tax effect	(1,326)	2,735	(5,493)	(4,489)
Net reclassification adjustment for (gains) losses included in net income	(467)	(1)	(1,444)	(251)
Related income tax expense (benefit)	173	0	534	91
Total AFS securities - all other	1,964	(4,865)	8,443	7,707
Net effect of AFS securities on other comprehensive income	1,964	(4,865)	8,443	7,944
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	1,111	1,161	3,298	3,458
Related income tax benefit	(394)	(384)	(1,191)	(1,223)
Net effect of change in pension plan asset on other comprehensive income	717	777	2,107	2,235
Net current-period other comprehensive income, net of tax	2,683	(4,086)	10,554	10,183
Comprehensive income, net of tax	$ 59,421	$ 37,393	$ 143,160	$ 118,160

Comprehensive Income - Compon97

Comprehensive Income - Components of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at January 1, 2017			$ 2,235,747
Net current-period other comprehensive income, net of tax	$ 2,683	$ (4,086)	10,554	$ 10,183
Balance at September 30, 2017	3,263,843		3,263,843
Pension Plan [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at January 1, 2017			(34,369)
Other comprehensive income before reclassification			0
Amounts reclassified from accumulated other comprehensive income			2,107
Net current-period other comprehensive income, net of tax			2,107
Balance at September 30, 2017	(32,262)		(32,262)
Unrealized Gains/Losses on AFS Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at January 1, 2017			(10,297)
Other comprehensive income before reclassification			9,353
Amounts reclassified from accumulated other comprehensive income			(910)
Net current-period other comprehensive income, net of tax			8,443
Balance at September 30, 2017	(1,854)		(1,854)
Accumulated Unrealized Loss On Securities Available For Sale Transferred To Held To Maturity [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at January 1, 2017			(51)
Other comprehensive income before reclassification			4
Amounts reclassified from accumulated other comprehensive income			0
Net current-period other comprehensive income, net of tax			4
Balance at September 30, 2017	(47)		(47)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at January 1, 2017			(44,717)
Other comprehensive income before reclassification			9,357
Amounts reclassified from accumulated other comprehensive income			1,197
Net current-period other comprehensive income, net of tax			10,554
Balance at September 30, 2017	$ (34,163)		$ (34,163)

Comprehensive Income - Reclassi

Comprehensive Income - Reclassifications Out of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Available for sale ("AFS") securities:
Net reclassification adjustment for losses (gains) included in net income	$ 467	$ 1	$ 5,214	$ 251
Income before income taxes	84,574	60,325	199,962	161,080
Related income tax effect	(27,836)	(18,846)	(67,356)	(53,103)
Net income	56,738	41,479	132,606	107,977
Pension plan:
Recognized net actuarial loss	1,111	1,161	3,298	3,458
Income before income taxes	84,574	60,325	199,962	161,080
Related income tax effect	(27,836)	(18,846)	(67,356)	(53,103)
Net income	$ 56,738	$ 41,479	132,606	$ 107,977
Reclassification out of Accumulated Other Comprehensive Income [Member]
Available for sale ("AFS") securities:
Net income			1,197
Pension plan:
Net income			1,197
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			(1,444)
Income before income taxes			(1,444)
Related income tax effect			534
Net income			(910)
Pension plan:
Income before income taxes			(1,444)
Related income tax effect			534
Net income			(910)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
Available for sale ("AFS") securities:
Income before income taxes			3,298
Related income tax effect			(1,191)
Net income			2,107
Pension plan:
Recognized net actuarial loss			3,298
Income before income taxes			3,298
Related income tax effect			(1,191)
Net income			$ 2,107

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, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share [Abstract]
Distributed earnings allocated to common stock	$ 34,587	$ 25,174	$ 95,871	$ 73,242
Undistributed earnings allocated to common stock	22,065	16,234	36,518	34,545
Net earnings allocated to common shareholders	$ 56,652	$ 41,408	$ 132,389	$ 107,787
Average common shares outstanding	104,760,153	76,218,573	95,040,664	72,413,246
Equivalents from stock options	307,969	429,200	409,962	333,117
Average diluted shares outstanding	105,068,122	76,647,773	95,450,626	72,746,363
Earnings per basic common share	$ 0.54	$ 0.54	$ 1.39	$ 1.49
Earnings per diluted common share	$ 0.54	$ 0.54	$ 1.39	$ 1.48

Variable Interest Entities - Ad

Variable Interest Entities - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2017Trust
Variable Interest Entity, Not Primary Beneficiary, Disclosures [Abstract]
Number of statutory business trusts	15
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, 2017USD ($)
Century Trust [Member]
Variable Interest Entity [Line Items]
Issuance Date	Mar. 23, 2000
Amount of Capital Securities Issued	$ 8,800
Interest Rate	10.875% Fixed
Maturity Date	Mar. 8, 2030
United Statutory Trust III [Member]
Variable Interest Entity [Line Items]
Issuance Date	Dec. 17, 2003
Amount of Capital Securities Issued	$ 20,000
Interest Rate	3-month LIBOR + 2.85%
Maturity Date	Dec. 17, 2033
United Statutory Trust IV [Member]
Variable Interest Entity [Line Items]
Issuance Date	Dec. 19, 2003
Amount of Capital Securities Issued	$ 25,000
Interest Rate	3-month LIBOR + 2.85%
Maturity Date	Jan. 23, 2034
United Statutory Trust V [Member]
Variable Interest Entity [Line Items]
Issuance Date	Jul. 12, 2007
Amount of Capital Securities Issued	$ 50,000
Interest Rate	3-month LIBOR + 1.55%
Maturity Date	Oct. 1, 2037
United Statutory Trust VI [Member]
Variable Interest Entity [Line Items]
Issuance Date	Sep. 20, 2007
Amount of Capital Securities Issued	$ 30,000
Interest Rate	3-month LIBOR + 1.30%
Maturity Date	Dec. 15, 2037
Premier Statutory Trust II [Member]
Variable Interest Entity [Line Items]
Issuance Date	Sep. 25, 2003
Amount of Capital Securities Issued	$ 6,000
Interest Rate	3-month LIBOR + 3.10%
Maturity Date	Oct. 8, 2033
Premier Statutory Trust III [Member]
Variable Interest Entity [Line Items]
Issuance Date	May 16, 2005
Amount of Capital Securities Issued	$ 8,000
Interest Rate	3-month LIBOR + 1.74%
Maturity Date	Jun. 15, 2035
Premier Statutory Trust IV [Member]
Variable Interest Entity [Line Items]
Issuance Date	Jun. 20, 2006
Amount of Capital Securities Issued	$ 14,000
Interest Rate	3-month LIBOR + 1.55%
Maturity Date	Sep. 23, 2036
Premier Statutory Trust V [Member]
Variable Interest Entity [Line Items]
Issuance Date	Dec. 14, 2006
Amount of Capital Securities Issued	$ 10,000
Interest Rate	3-month LIBOR + 1.61%
Maturity Date	Mar. 1, 2037
Centra Statutory Trust I [Member]
Variable Interest Entity [Line Items]
Issuance Date	Sep. 20, 2004
Amount of Capital Securities Issued	$ 10,000
Interest Rate	3-month LIBOR + 2.29%
Maturity Date	Sep. 20, 2034
Centra Statutory Trust II [Member]
Variable Interest Entity [Line Items]
Issuance Date	Jun. 15, 2006
Amount of Capital Securities Issued	$ 10,000
Interest Rate	3-month LIBOR + 1.65%
Maturity Date	Jul. 7, 2036
Virginia Commerce Trust II [Member]
Variable Interest Entity [Line Items]
Issuance Date	Dec. 19, 2002
Amount of Capital Securities Issued	$ 15,000
Interest Rate	6-month LIBOR + 3.30%
Maturity Date	Dec. 19, 2032
Virginia Commerce Trust III [Member]
Variable Interest Entity [Line Items]
Issuance Date	Dec. 20, 2005
Amount of Capital Securities Issued	$ 25,000
Interest Rate	3-month LIBOR + 1.42%
Maturity Date	Feb. 23, 2036
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, 2017	Dec. 31, 2016
Variable Interest Entity [Line Items]
Aggregate Assets	$ 266,560	$ 240,668
Aggregate Liabilities	257,605	232,583
Risk Of Loss	$ 8,955	$ 8,085

Segment Information - Additiona

Segment Information - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2017Segment
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		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Segment Reporting Information [Line Items]
Net interest income	$ 150,276	$ 111,069	$ 394,141	$ 312,078
Provision for loans losses	7,279	6,988	21,429	18,690	$ 24,509
Other income	38,229	19,021	98,881	53,380
Other expense	96,652	62,777	271,631	185,688
Income taxes	27,836	18,846	67,356	53,103
Net income	56,738	41,479	132,606	107,977
Total assets (liabilities)	19,129,978	14,344,696	19,129,978	14,344,696
Average assets (liabilities)	18,927,785	14,159,569	17,187,644	13,104,398
Operating Segments [Member] | Community Banking [Member]
Segment Reporting Information [Line Items]
Net interest income	152,886	113,033	401,044	317,835
Provision for loans losses	7,279	6,988	21,429	18,690
Other income	18,373	19,666	53,409	55,323
Other expense	74,553	63,009	215,935	186,322
Income taxes	29,490	19,729	73,214	55,580
Net income	59,937	42,973	143,875	112,566
Total assets (liabilities)	18,780,395	14,364,797	18,780,395	14,364,797
Average assets (liabilities)	18,620,035	14,182,202	17,020,928	13,125,973
Operating Segments [Member] | Mortgage Banking [Member]
Segment Reporting Information [Line Items]
Net interest income	(36)		54
Provision for loans losses	0		0
Other income	19,936		42,329
Other expense	24,036		42,744
Income taxes	(1,332)		(39)
Net income	(2,804)		(322)
Total assets (liabilities)	350,483		350,483
Average assets (liabilities)	321,744		187,118
Other [Member]
Segment Reporting Information [Line Items]
Net interest income	(2,574)	(1,964)	(6,957)	(5,757)
Provision for loans losses	0	0	0	0
Other income	(80)	(645)	3,143	(1,943)
Other expense	(1,937)	(232)	12,952	(634)
Income taxes	(322)	(883)	(5,819)	(2,477)
Net income	(395)	(1,494)	(10,947)	(4,589)
Total assets (liabilities)	(900)	(20,101)	(900)	(20,101)
Average assets (liabilities)	$ (13,994)	$ (22,633)	$ (20,402)	$ (21,575)