BancFirst (BANF) 10-Q 2 Nov 18 2018 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Oct. 31, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3
Trading Symbol	BANF
Entity Registrant Name	BANCFIRST CORP /OK/
Entity Central Index Key	760,498
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		32,753,690

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
ASSETS
Cash and due from banks	$ 185,009	$ 216,104
Interest-bearing deposits with banks	1,607,157	1,541,771
Federal funds sold	600	700
Securities held for investment (fair value: $1,447 and $2,303, respectively)	1,440	2,292
Securities available for sale at fair value	475,640	467,703
Loans held for sale	4,739	6,173
Loans (net of unearned interest)	4,947,528	4,721,995
Allowance for loan losses	(51,875)	(51,666)
Loans, net of allowance for loan losses	4,895,653	4,670,329
Premises and equipment, net	170,167	134,088
Other real estate owned	6,827	4,136
Intangible assets, net	17,257	11,082
Goodwill	79,733	54,042
Accrued interest receivable and other assets	158,216	144,736
Total assets	7,602,438	7,253,156
Deposits:
Noninterest-bearing	2,662,304	2,550,150
Interest-bearing	3,980,827	3,864,895
Total deposits	6,643,131	6,415,045
Short-term borrowings	2,200	900
Accrued interest payable and other liabilities	40,347	29,623
Junior subordinated debentures	31,959	31,959
Total liabilities	6,717,637	6,477,527
Stockholders' equity:
Common stock, $1.00 par, 40,000,000 shares authorized; shares issued and outstanding: 32,749,690 and 31,894,563, respectively	32,750	31,895
Capital surplus	149,242	107,481
Retained earnings	707,481	638,580
Accumulated other comprehensive loss, net of income tax of $(1,597) and $(795), respectively	(4,672)	(2,327)
Total stockholders' equity	884,801	775,629
Total liabilities and stockholders' equity	7,602,438	7,253,156
Senior Preferred Stock [Member]
Stockholders' equity:
Preferred stock, value
Cumulative Preferred Stock [Member]
Stockholders' equity:
Preferred stock, value

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Securities, fair value	$ 1,447	$ 2,303
Common stock, par value	$ 1	$ 1
Common stock, shares authorized	40,000,000	40,000,000
Common stock, shares issued	32,749,690	31,894,563
Common stock, shares outstanding	32,749,690	31,894,563
Accumulated other comprehensive loss, tax expense (benefit)	$ (1,597)	$ (795)
Senior Preferred Stock [Member]
Preferred stock, par value	$ 1	$ 1
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Cumulative Preferred Stock [Member]
Preferred stock, par value	$ 5	$ 5
Preferred stock, shares authorized	900,000	900,000
Preferred stock, shares issued	0	0

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
INTEREST INCOME
Loans, including fees	$ 66,788	$ 56,090	$ 195,311	$ 164,488
Securities:
Taxable	2,246	1,763	6,100	5,430
Tax-exempt	145	187	478	552
Federal funds sold	89	6	288	7
Interest-bearing deposits with banks	8,165	4,972	21,272	12,837
Total interest income	77,433	63,018	223,449	183,314
INTEREST EXPENSE
Deposits	11,171	5,247	28,150	13,272
Short-term borrowings	42	6	85	13
Junior subordinated debentures	547	532	1,626	1,589
Total interest expense	11,760	5,785	29,861	14,874
Net interest income	65,673	57,233	193,588	168,440
Provision for loan losses	747	3,276	2,286	5,189
Net interest income after provision for loan losses	64,926	53,957	191,302	163,251
NONINTEREST INCOME
Trust revenue	3,281	3,083	9,806	8,929
Service charges on deposits	18,103	16,633	52,293	48,859
Securities transactions (includes accumulated other comprehensive income reclassifications of $9, $0, $9 and $(142), respectively)	(64)	(22)	37	(352)
Income from sales of loans	800	732	2,253	2,180
Insurance commissions	5,207	4,603	14,333	12,894
Cash management	3,383	2,804	9,785	8,357
Gain (loss) on sale of other assets	195	29	348	(20)
Other	1,896	1,307	4,493	4,390
Total noninterest income	32,801	29,169	93,348	85,237
NONINTEREST EXPENSE
Salaries and employee benefits	35,051	31,471	104,017	93,672
Occupancy, net	3,386	3,298	10,184	9,264
Depreciation	2,733	2,493	7,572	7,305
Amortization of intangible assets	740	547	2,232	1,641
Data processing services	1,418	1,110	3,816	3,402
Net expense from other real estate owned	64	68	109	320
Marketing and business promotion	1,997	1,790	5,998	5,564
Deposit insurance	597	553	1,856	1,683
Other	9,823	9,270	30,171	26,290
Total noninterest expense	55,809	50,600	165,955	149,141
Income before taxes	41,918	32,526	118,695	99,347
Income tax expense	9,035	10,816	25,606	32,405
Net income	$ 32,883	$ 21,710	$ 93,089	$ 66,942
NET INCOME PER COMMON SHARE
Basic	$ 1.01	$ 0.68	$ 2.85	$ 2.11
Diluted	$ 0.98	$ 0.67	$ 2.78	$ 2.06
OTHER COMPREHENSIVE (LOSS)/INCOME
Unrealized (losses)/gains on securities, net of tax of $352, $178, $1,005 and $11, respectively	$ (1,027)	$ (282)	$ (2,956)	$ (17)
Reclassification adjustment for losses included in net income, net of tax of $2, $0, $2 and $(55), respectively	(7)		(7)	87
Other comprehensive (losses)/gains, net of tax of $354, $178, $802 and $(44), respectively	(1,034)	(282)	(2,963)	70
Comprehensive income	$ 31,849	$ 21,428	$ 90,126	$ 67,012

Consolidated Statements of Co_2

Consolidated Statements of Comprehensive Income (Unaudited) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Statement [Abstract]
Securities transactions accumulated other comprehensive income reclassifications	$ 9	$ 0	$ 9	$ (142)
Unrealized (losses)/gains on securities, tax	352	178	1,005	11
Reclassification adjustment for losses included in net income, tax	2	0	2	(55)
Other comprehensive (losses)/gains, tax	$ 354	$ 178	$ 802	$ (44)

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	COMMON STOCK [Member]	CAPITAL SURPLUS [Member]	RETAINED EARNINGS [Member]	ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) [Member]
Balance at beginning of period at Dec. 31, 2016		$ 31,622	$ 101,730	$ 577,648	$ 94
Shares issued for stock options		241	4,056
Stock-based compensation arrangements			819
Net income	$ 66,942			66,942
Dividends on common stock				(18,808)
Net change	70				70
Balance at end of period at Sep. 30, 2017	764,414	31,863	106,605	625,782	164
Balance at beginning of period at Jun. 30, 2017		31,818	105,440	610,758	446
Shares issued for stock options		45	811
Stock-based compensation arrangements			354
Net income	21,710			21,710
Dividends on common stock				(6,686)
Net change	(282)				(282)
Balance at end of period at Sep. 30, 2017	764,414	31,863	106,605	625,782	164
Balance at beginning of period at Dec. 31, 2017	775,629	31,895	107,481	638,580	(2,327)
Shares issued for stock options		122	2,015
Shares issued for acquisitions		733	38,765
Stock-based compensation arrangements			981
Net income	93,089			93,089
Cumulative effect of change in accounting principle				(618)	618
Dividends on common stock				(23,570)
Net change	(2,963)				(2,963)
Balance at end of period at Sep. 30, 2018	884,801	32,750	149,242	707,481	(4,672)
Balance at beginning of period at Jun. 30, 2018		32,731	148,494	684,425	(3,638)
Shares issued for stock options		19	395
Stock-based compensation arrangements			353
Net income	32,883			32,883
Dividends on common stock				(9,827)
Net change	(1,034)				(1,034)
Balance at end of period at Sep. 30, 2018	$ 884,801	$ 32,750	$ 149,242	$ 707,481	$ (4,672)

Consolidated Statements of St_2

Consolidated Statements of Stockholders' Equity (Unaudited) (Parenthetical) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
RETAINED EARNINGS [Member]
Dividend on common stock	$ 0.30	$ 0.21	$ 0.72	$ 0.59

Consolidated Statements of Cash

Consolidated Statements of Cash Flow (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 93,089	$ 66,942
Adjustments to reconcile to net cash provided by operating activities:
Provision for loan losses	2,286	5,189
Depreciation and amortization	9,804	8,946
Net amortization of securities premiums and discounts	(141)	(108)
Realized securities (gains)/losses	(37)	352
Gain on sales of loans	(2,253)	(2,180)
Cash receipts from the sale of loans originated for sale	145,840	163,128
Cash disbursements for loans originated for sale	(142,207)	(163,460)
Deferred income tax provision (benefit)	83	(1,690)
(Gain)/loss on other assets	(341)	66
Increase in interest receivable	(2,380)	(1,651)
Increase in interest payable	764	188
Amortization of stock-based compensation arrangements	981	819
Excess tax benefit from stock-based compensation arrangements	(1,067)	(2,229)
Other, net	(4,994)	2,513
Net cash provided by operating activities	99,427	76,825
INVESTING ACTIVITIES
Net cash received from acquisitions, net of cash paid	6,248
Net decrease/(increase) in federal funds sold	22,948	(11,300)
Purchases of held for investment securities	(225)	(220)
Purchases of available for sale securities	(168,971)	(54,456)
Proceeds from maturities, calls and paydowns of held for investment securities	1,077	1,517
Proceeds from maturities, calls and paydowns of available for sale securities	121,581	72,853
Proceeds from sales of available for sale securities	31,286
Purchase of equity securities	(2,118)
Proceeds from paydowns and sales of equity securities	1,414
Net change in loans	81,000	(251,883)
Purchases of premises, equipment and computer software	(44,398)	(11,495)
Proceeds from the sale of other real estate owned and other assets	3,899	2,846
Net cash provided by/(used in) investing activities	53,741	(252,138)
FINANCING ACTIVITIES
Net change in deposits	(101,874)	53,989
Net increase in short-term borrowings	1,300	1,600
Issuance of common stock in connection with stock options, net	2,137	4,297
Cash dividends paid	(20,440)	(18,091)
Net cash (used in)/provided by financing activities	(118,877)	41,795
Net increase/(decrease) in cash, due from banks and interest-bearing deposits	34,291	(133,518)
Cash, due from banks and interest-bearing deposits at the beginning of the period	1,757,875	1,850,461
Cash, due from banks and interest-bearing deposits at the end of the period	1,792,166	1,716,943
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Cash paid during the period for interest	29,096	14,688
Cash paid during the period for income taxes	24,255	32,051
Noncash investing and financing activities:
Stock issued in acquisitions	39,498
Cash consideration for acquisitions	24,722
Fair value of assets acquired in acquisitions	377,320
Liabilities assumed in acquisitions	338,860
Unpaid common stock dividends declared	$ 9,823	$ 6,686

Description of Business and Sum

Description of Business and Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Description of Business and Summary of Significant Accounting Policies	(1) DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES The accounting and reporting policies of BancFirst Corporation and its subsidiaries (the “Company”) conform to accounting principles generally accepted in the United States of America (U.S. GAAP) and general practice within the banking industry. A summary of significant accounting policies can be found in Note (1) to the Company’s Annual Report on Form 10-K for the year ended December 31, 2017. Basis of Presentation The accompanying unaudited interim consolidated financial statements include the accounts of BancFirst Corporation, Council Oak Partners, LLC, BancFirst Insurance Services, Inc., BancFirst Risk and Insurance Company and BancFirst and its subsidiaries. The principal operating subsidiaries of BancFirst are Council Oak Investment Corporation, Council Oak Real Estate, Inc., BFTower, LLC and BancFirst Agency, Inc. All significant intercompany accounts and transactions have been eliminated. Assets held in a fiduciary or agency capacity are not assets of the Company and, accordingly, are not included in the unaudited interim consolidated financial statements. The accompanying unaudited interim consolidated financial statements and notes are presented in accordance with the instructions for Form 10-Q. The information contained in the financial statements and footnotes included in BancFirst Corporation’s Annual Report on Form 10-K for the year ended December 31, 2017, should be referred to in connection with these unaudited interim consolidated financial statements. Operating results for the interim periods disclosed herein are not necessarily indicative of the results that may be expected for a full year or any future period. The unaudited interim consolidated financial statements contained herein reflect all adjustments which are, in the opinion of management, necessary to provide a fair statement of the financial position and results of operations of the Company for the interim periods presented. All such adjustments are of a normal and recurring nature. There have been no significant changes in the accounting policies of the Company since December 31, 2017, the date of the most recent annual report. Reclassifications Certain items in prior financial statements have been reclassified to conform to the current presentation. Such reclassifications had no effect on previously reported cash flows, stockholders’ equity or comprehensive income. Use of Estimates in the Preparation of Financial Statements The preparation of financial statements in conformity with accounting principles generally accepted in the United States inherently involves the use of estimates and assumptions that affect the amounts reported in the financial statements and the related disclosures. These estimates relate principally to the determination of the allowance for loan losses, income taxes, the fair value of financial instruments and the valuation of intangibles. Such estimates and assumptions may change over time and actual amounts realized may differ from those reported. Recent Accounting Pronouncements Standards Adopted During Current Period: In February 2018, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2018-2, Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income. ASU 2018-2 allows a reclassification from accumulated other comprehensive income (loss) to retained earnings for stranded tax effects resulting from the Tax Cuts and Jobs Act. ASU 2018-2 is effective for fiscal years beginning after December 15, 2018 with early adoption permitted. The Company elected to early adopt the provisions of ASU 2018-2 and the amount to reclassify was immaterial to the Company’s financial statements. The Company’s policy is to release material stranded tax effects on a specific identification basis. In May 2017, the FASB issued ASU No. 2017-09, “Compensation – Stock Compensation (Topic 718): Scope of Modification Accounting.” The amendments in this update provide guidance about types of changes to the terms of conditions of share-based payment awards that would require an entity to apply modification accounting under ASC 718. ASU 2017-09 was adopted on January 1, 2018 and did not have a significant impact on the Company’s financial statements and no prior periods were adjusted. In January 2017, the FASB issued ASU No. 2017-04, “Intangibles – Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment.” ASU 2017-04 removes the second step of goodwill testing. ASU 2017-04 is effective for fiscal years beginning after December 31, 2019 with early adoption permitted. The Company elected to early adopt ASU 2017-4 and it did not have a significant impact on the Company’s financial statements. In January 2017, the FASB issued ASU No. 2017-01, “Business Combinations (Topic 805): Clarifying the Definition of a Business.” ASU 2017-01 clarifies the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of a business. ASU 2017-01 was adopted on January 1, 2018 and did not have a significant impact on the Company’s financial statements. In October 2016, the FASB issued ASU No. 2016-16, “Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory.” ASU 2016-16 provides guidance stating that an entity should recognize the income tax consequences of an intra-entity transfer of an asset other than inventory when the transfer occurs. ASU 2016-16 was adopted on January 1, 2018 and did not have a significant impact on the Company’s financial statements and no prior periods were adjusted. In August 2016, the FASB issued ASU No. 2016-15, “Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments.” ASU 2016-15 is intended to reduce the diversity in practice around how certain transactions are classified within the statement of cash flows. ASU 2016-15 was adopted on January 1, 2018 and did not have a significant impact on the Company’s financial statements. In January 2016, the FASB issued ASU No. 2016-01, “Financial Instruments – Overall (Subtopic 825-10).” ASU 2016-01 requires all equity investments (except those accounted for under the equity method of accounting or those that result in consolidation of the investee) to be measured at fair value with changes in the fair value recognized through net income. The adoption of the guidance resulted in a $618,000 decrease to retained earnings and a $618,000 increase to accumulated other comprehensive income. Additional income of $41,200 was recorded in the consolidated statement of comprehensive income during 2018 as a result of changes to the accounting for equity investments. Further, the Company’s securities disclosures in Note (3) have been revised to exclude equity investments in 2018 and fair value disclosures in Note (9) have incorporated the revised disclosure requirements for financial investments. ASU 2016-01 also emphasizes the existing requirement to use exit prices to measure fair value for disclosure purposes and clarifies that entities should not make use of a practicability exception in determining the fair value of loans. Accordingly, we refined the calculation used to determine the disclosed fair value of loans held for investment as part of adopting this standard. The refined calculation did not have a significant impact on fair value disclosures. In January 2014, the FASB issued ASU No. 2014-09, “Revenue from Contracts with Customer (Topic 606).” ASU 2014-09 implements a comprehensive new revenue recognition standard that will supersede substantially all existing revenue recognition guidance. The new standard’s core principle is that a company will recognize revenue when it transfers promised goods or services to customers in a manner that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. The guidance does not apply to revenue associated with financial instruments, including loans and securities that are accounted for under other GAAP, which comprises a significant portion of the Company’s revenue stream. ASU 2014-09 was adopted on January 1, 2018 and did not have a significant impact on the Company’s financial statements. Standards Not Yet Adopted: In August 2018, the FASB issued ASU No. 2018-13, “Fair Value Measurement (Topic 820).” ASU 2018-13 removes, modifies and adds disclosure requirements on fair value measurements. ASU 2018-13 will be effective for the Company on January 1, 2020. Early adoption is permitted. In addition, early adoption of any removed or modified disclosures and delayed adoption of the additional disclosures until the effective date is also permitted. In June 2016, the FASB issued ASU No. 2016-13, “Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments.” ASU 2016-13 requires a financial asset measured at amortized cost basis to be presented at the net amount expected to be collected. The measurement of expected credit losses is based on relevant information about past events, including historical experience, current conditions, and reasonable and supportable forecasts that affect the collectability of the reported amount. ASU 2016-13 requires enhanced disclosures related to the significant estimates and judgements used in estimating credit losses, as well as the credit quality and underwriting standards of an organization’s portfolio. In addition, ASU 2016-13 amends the accounting for credit losses on available-for-sale debt securities and purchased financial assets with credit deterioration. ASU 2016-13 will be effective for the Company on January 1, 2020. The Company is currently evaluating the potential impact of ASU 2016-13 on its financial statements. In that regard, the Company has formed a task force under the direction of its Chief Financial Officer. The Company is currently developing an implementation plan to include assessment of process, portfolio segmentation, model development, system requirements and the identification of data and resource need, among other things. In February 2016, the FASB issued ASU No. 2016-02, “Leases - (Topic 842).” ASU 2016-02 requires that lessees recognize on the balance sheet the assets and liabilities for the rights and obligations created by leases. The amendments are effective for annual periods, and interim reporting periods within those annual periods, beginning after December 15, 2018. The Company .

Recent Developments, Including

Recent Developments, Including Mergers and Acquisitions	9 Months Ended
	Sep. 30, 2018
Recent Developments Including Mergers And Acquisitions [Abstract]
Recent Developments, Including Mergers and Acquisitions	(2) RECENT DEVELOPMENTS, INCLUDING MERGERS AND ACQUISITIONS On August 31, 2018 the Company’s wholly-owned subsidiary, BFTower, LLC, On January 11, 2018, the Company acquired First Wagoner Corp. and its subsidiary bank, First Bank & Trust Company, with locations in Carney, Grove, Ketchum, Luther, Tulsa and Wagoner. First Bank & Trust Company had approximately $290 million in total assets, $247 million in loans, $251 million in deposits and $36 million in equity capital. First Bank & Trust Company operated as a subsidiary of BancFirst Corporation until it was merged into BancFirst on February 16, 2018. As a result of the acquisition, the Company recorded a core deposit intangible of approximately $6.3 million and goodwill of approximately $19.1 million. These fair value estimates are considered preliminary and are subject to change for up to one year after the closing date of the acquisition as additional information becomes available. On January 11, 2018, the Company acquired First Chandler Corp. and its subsidiary bank, First Bank of Chandler, with two locations in Chandler. First Bank of Chandler had approximately $88 million in total assets, $66 million in loans, $79 million in deposits and $11 million in equity capital. First Bank of Chandler operated as a subsidiary of BancFirst Corporation until it was merged into BancFirst on September 16, 2018. As a result of the acquisition, the Company recorded a core deposit intangible of approximately $2.2 million and goodwill of approximately $6.6 million. These fair value estimates are considered preliminary and are subject to change for up to one year after the closing date of the acquisition as additional information becomes available. On July 31, 2017, the Company completed a two-for-one stock split of the Company’s outstanding shares of common stock. The stock was payable in the form of a dividend on or about July 31, 2017 to shareholders of record of the outstanding common stock as of the close of business record date of July 17, 2017. Stockholders received one additional share for each share held on that date. This was the second stock split for the Company since going public. All share and per share amounts in these consolidated financial statements and related notes have been retroactively adjusted to reflect this stock split for all periods presented.

Securities

Securities	9 Months Ended
	Sep. 30, 2018
Investments Debt And Equity Securities [Abstract]
Securities	( 3 ) SECURITIES The following table summarizes securities held for investment and securities available for sale: September 30, 2018 December 31, 2017 (Dollars in thousands) Held for investment, at cost (fair value: $1,447 and $2,303, respectively) $ 1,440 $ 2,292 Available for sale, at fair value 475,640 467,703 Total $ 477,080 $ 469,995 The following table summarizes the amortized cost and estimated fair values of securities held for investment: Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value September 30, 2018 (Dollars in thousands) Mortgage backed securities (1) $ 145 $ 6 $ — $ 151 States and political subdivisions 795 1 — 796 Other securities 500 — — 500 Total $ 1,440 $ 7 $ — $ 1,447 December 31, 2017 Mortgage backed securities (1) $ 187 $ 10 $ — $ 197 States and political subdivisions 1,605 3 (2 ) 1,606 Other securities 500 — — 500 Total $ 2,292 $ 13 $ (2 ) $ 2,303 The following table summarizes the amortized cost and estimated fair values of securities available for sale: Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value September 30, 2018 (Dollars in thousands) U.S. treasuries $ 403,213 $ — $ (5,747 ) $ 397,466 U.S. federal agencies 32,017 1 (178 ) 31,840 Mortgage backed securities (1) 16,581 119 (566 ) 16,134 States and political subdivisions 30,098 262 (160 ) 30,200 Total $ 481,909 $ 382 $ (6,651 ) $ 475,640 December 31, 2017 U.S. treasuries $ 314,905 $ — $ (2,103 ) $ 312,802 U.S. federal agencies 89,098 82 (329 ) 88,851 Mortgage backed securities (1) 18,358 204 (586 ) 17,976 States and political subdivisions 41,937 554 (121 ) 42,370 Equity securities (2) 6,527 71 (894 ) 5,704 Total $ 470,825 $ 911 $ (4,033 ) $ 467,703 (1) Primarily consists of FHLMC, FNMA, GNMA and mortgage backed securities through U.S. agencies. (2) Consisted of equity securities that are included in other assets in 2018. The maturities of securities held for investment and available for sale are summarized in the following table using contractual maturities. Actual maturities may differ from contractual maturities due to obligations that are called or prepaid. For purposes of the maturity table, mortgage-backed securities, which are not due at a single maturity date, have been presented at their contractual maturity. September 30, 2018 December 31, 2017 Amortized Cost Estimated Fair Value Amortized Cost Estimated Fair Value (Dollars in thousands) Held for Investment Contractual maturity of debt securities: Within one year $ 495 $ 496 $ 1,036 $ 1,034 After one year but within five years 370 371 623 627 After five years but within ten years 570 575 625 633 After ten years 5 5 8 9 Total $ 1,440 $ 1,447 $ 2,292 $ 2,303 Available for Sale Contractual maturity of debt securities: Within one year $ 61,869 $ 61,656 $ 113,225 $ 112,974 After one year but within five years 368,309 362,723 289,038 287,058 After five years but within ten years 5,047 5,225 6,222 6,500 After ten years 46,684 46,036 55,813 55,467 Total debt securities 481,909 475,640 464,298 461,999 Equity securities — — 6,527 5,704 Total $ 481,909 $ 475,640 $ 470,825 $ 467,703 The following table is a summary of the Company’s book value of securities that were pledged as collateral for public funds on deposit, repurchase agreements and for other purposes as required or permitted by law: September 30, 2018 December 31, 2017 (Dollars Book value of pledged securities $ 428,057 $ 440,069

Loans and Allowance for Loan Lo

Loans and Allowance for Loan Losses	9 Months Ended
	Sep. 30, 2018
Receivables [Abstract]
Loans and Allowance for Loan Losses	( 4 ) LOANS AND ALLOWANCE FOR LOAN LOSSES The following is a schedule of loans outstanding by category: September 30, 2018 December 31, 2017 Amount Percent Amount Percent (Dollars in thousands) Commercial and financial: Commercial and industrial $ 1,042,237 21.07 % $ 995,207 21.08 % Oil & gas production and equipment 98,324 1.99 95,574 2.02 Agriculture 127,904 2.59 141,249 2.99 State and political subdivisions: Taxable 79,832 1.61 73,827 1.56 Tax-exempt 41,368 0.84 48,626 1.03 Real estate: Construction 446,046 9.02 437,277 9.26 Farmland 217,191 4.38 195,162 4.13 One to four family residences 972,922 19.66 875,766 18.55 Multifamily residential properties 62,555 1.26 46,030 0.98 Commercial 1,497,894 30.28 1,487,927 31.51 Consumer 323,952 6.55 284,373 6.02 Other (not classified above) 37,303 0.75 40,977 0.87 Total loans $ 4,947,528 100.00 % $ 4,721,995 100.00 % The Company’s loans are mostly to customers within Oklahoma and over 60% of the loans are secured by real estate. Credit risk on loans is managed through limits on amounts loaned to individual and related borrowers, underwriting standards and loan monitoring procedures. The amounts and types of collateral obtained, if any, to secure loans are based upon the Company’s underwriting standards and management’s credit evaluation. Collateral varies, but may include real estate, equipment, accounts receivable, inventory, livestock and securities. The Company’s interest in collateral is secured through filing mortgages and liens, and in some cases, by possession of the collateral. The Company’s commercial and industrial loan category includes a small percentage of loans to companies that provide ancillary services to the oil and gas industry, such as transportation, preparation contractors and equipment manufacturers. The balance of these loans was approximately $62 million at September 30, 2018 and approximately $81 million at December 31, 2017. Accounting policies related to appraisals, nonaccruals and charge-offs are disclosed in Note (1) to the Company’s Annual Report on Form 10-K for the year ended December 31, 2017. Nonperforming and Restructured Assets The following is a summary of nonperforming and restructured assets: September 30, December 31, 2018 2017 (Dollars in thousands) Past due 90 days or more and still accruing $ 4,073 $ 2,893 Nonaccrual 26,880 31,943 Restructured 13,557 4,720 Total nonperforming and restructured loans 44,510 39,556 Other real estate owned and repossessed assets 7,072 4,424 Total nonperforming and restructured assets $ 51,582 $ 43,980 Had nonaccrual loans performed in accordance with their original contractual terms, the Company would have recognized additional interest income of approximately $1.7 million for the nine months ended September 30, 2018 and approximately $1.3 million for the nine months ended September 30, 2017. The Company charges interest on principal balances outstanding on restructured loans during deferral periods. The current and future financial effects of the recorded balance of loans considered to be restructured were not considered to be material. Loans are segregated into classes based upon the nature of the collateral and the borrower. These classes are used to estimate the allowance for loan losses. The following table is a summary of amounts included in nonaccrual loans, segregated by class of loans. Residential real estate refers to one-to-four family real estate. September 30, 2018 December 31, 2017 (Dollars in thousands) Real estate: Non-residential real estate owner occupied $ 1,526 $ 1,108 Non-residential real estate other 7,125 9,809 Residential real estate permanent mortgage 1,043 781 Residential real estate all other 4,911 3,980 Commercial and financial: Non-consumer non-real estate 6,032 7,785 Consumer non-real estate 416 250 Other loans 427 5,596 Acquired loans 5,400 2,634 Total $ 26,880 $ 31,943 Loans are considered past due if the required principal and interest payments have not been received as of the date such payments were due. The following table presents an age analysis of past due loans, segregated by class of loans: Age Analysis of Past Due Loans 30-59 Days Past Due 60-89 Days Past Due 90 Days and Greater Total Past Due Loans Current Loans Total Loans Accruing Loans 90 Days or More Past Due (Dollars in thousands) As of September 30, 2018 Real estate: Non-residential real estate owner occupied $ 977 $ 1,106 $ 811 $ 2,894 $ 627,528 $ 630,422 $ 90 Non-residential real estate other 4,964 385 172 5,521 1,111,929 1,117,450 57 Residential real estate permanent mortgage 3,910 1,318 961 6,189 322,237 328,426 427 Residential real estate all other 2,034 2,790 2,333 7,157 810,727 817,884 845 Commercial and financial: Non-consumer non-real estate 2,573 1,469 2,222 6,264 1,263,816 1,270,080 1,070 Consumer non-real estate 1,721 530 552 2,803 317,629 320,432 345 Other loans 514 — 372 886 142,319 143,205 128 Acquired loans 2,927 2,175 4,164 9,266 310,363 319,629 1,111 Total $ 19,620 $ 9,773 $ 11,587 $ 40,980 $ 4,906,548 $ 4,947,528 $ 4,073 As of December 31, 2017 Real estate: Non-residential real estate owner occupied $ 998 $ 68 $ 977 $ 2,043 $ 639,575 $ 641,618 $ 84 Non-residential real estate other 2,905 271 2,112 5,288 1,121,303 1,126,591 432 Residential real estate permanent mortgage 2,211 403 977 3,591 326,743 330,334 584 Residential real estate all other 1,739 749 1,377 3,865 781,790 785,655 973 Commercial and financial: Non-consumer non-real estate 2,210 706 1,785 4,701 1,279,704 1,284,405 403 Consumer non-real estate 2,085 670 293 3,048 285,872 288,920 194 Other loans 506 103 3,916 4,525 139,920 144,445 — Acquired loans 753 192 713 1,658 118,369 120,027 223 Total $ 13,407 $ 3,162 $ 12,150 $ 28,719 $ 4,693,276 $ 4,721,995 $ 2,893 Impaired Loans Loans are considered impaired when, based on current information and events, it is probable the Company will be unable to collect the full amount of scheduled principal and interest payments in accordance with the original contractual terms of the loan agreement. If a loan is impaired, a specific valuation allowance may be allocated, if necessary, so that the loan is reported, net of allowance for loss, at the present value of future cash flows using the loan’s existing rate, or the fair value of collateral if repayment is expected solely from the collateral. The following table presents impaired loans, segregated by class of loans. During the period ended September 30, 2018 no material amount of interest income was recognized on impaired loans subsequent to their classification as impaired. During the period ended September 30, 2017, $2.3 million of interest income was recognized on impaired loans subsequent to their classification as impaired. Impaired Loans Unpaid Principal Balance Recorded Investment with Allowance Related Allowance Average Recorded Investment (Dollars in thousands) As of September 30, 2018 Real estate: Non-residential real estate owner occupied $ 8,187 $ 8,063 $ 353 $ 7,877 Non-residential real estate other 8,262 7,753 333 8,678 Residential real estate permanent mortgage 1,842 1,634 145 1,746 Residential real estate all other 6,762 6,507 2,310 6,678 Commercial and financial: Non-consumer non-real estate 19,458 12,065 2,234 13,359 Consumer non-real estate 897 825 108 818 Other loans 772 558 43 456 Acquired loans 10,784 7,745 4 7,442 Total $ 56,964 $ 45,150 $ 5,530 $ 47,054 As of December 31, 2017 Real estate: Non-residential real estate owner occupied $ 2,011 $ 1,945 $ 141 $ 1,858 Non-residential real estate other 10,323 10,240 496 3,975 Residential real estate permanent mortgage 1,745 1,542 146 1,440 Residential real estate all other 5,837 5,549 2,135 5,258 Commercial and financial: Non-consumer non-real estate 18,101 11,158 2,412 11,131 Consumer non-real estate 545 514 127 541 Other loans 6,092 5,595 178 7,439 Acquired loans 4,737 3,145 12 3,539 Total $ 49,391 $ 39,688 $ 5,647 $ 35,181 Credit Risk Monitoring and Loan Grading The Company considers various factors to monitor the credit risk in the loan portfolio including volume and severity of loan delinquencies, nonaccrual loans, internal grading of loans, historical loan loss experience and economic conditions. An internal risk grading system is used to indicate the credit risk of loans. The loan grades used by the Company are for internal risk identification purposes and do not directly correlate to regulatory classification categories or any financial reporting definitions. The general characteristics of the risk grades are disclosed in Note (5) to the Company’s Annual Report on Form 10-K for the year ended December 31, 2017. The following table presents internal loan grading by class of loans: Internal Loan Grading Grade 1 2 3 4 5 Total (Dollars in thousands) As of September 30, 2018 Real estate: Non-residential real estate owner occupied $ 478,014 $ 131,597 $ 19,221 $ 1,590 $ — $ 630,422 Non-residential real estate other 913,259 181,829 15,238 7,124 — 1,117,450 Residential real estate permanent mortgage 280,194 38,452 8,093 1,687 — 328,426 Residential real estate all other 641,246 156,018 15,000 5,620 — 817,884 Commercial and financial: Non-consumer non-real estate 980,535 268,882 14,915 5,748 — 1,270,080 Consumer non-real estate 297,516 19,975 2,202 739 — 320,432 Other loans 137,705 5,304 157 39 — 143,205 Acquired loans 188,452 99,686 25,082 6,160 249 319,629 Total $ 3,916,921 $ 901,743 $ 99,908 $ 28,707 $ 249 $ 4,947,528 As of December 31, 2017 Real estate: Non-residential real estate owner occupied $ 520,641 $ 105,696 $ 13,852 $ 1,429 $ — $ 641,618 Non-residential real estate other 931,295 178,282 14,290 2,724 — 1,126,591 Residential real estate permanent mortgage 289,200 33,033 6,352 1,749 — 330,334 Residential real estate all other 621,401 149,201 9,418 5,635 — 785,655 Commercial and financial: Non-consumer non-real estate 1,018,172 234,884 24,322 6,997 30 1,284,405 Consumer non-real estate 268,826 17,499 2,038 557 — 288,920 Other loans 136,617 5,668 1,203 957 — 144,445 Acquired loans 65,685 34,418 17,113 2,811 — 120,027 Total $ 3,851,837 $ 758,681 $ 88,588 $ 22,859 $ 30 $ 4,721,995 Allowance for Loan Losses Methodology The allowance for loan losses (“ALL”) methodology is disclosed in Note (5) to the Company’s Annual Report on Form 10-K for the year ended December 31, 2017. The following table details activity in the ALL by class of loans for the period presented. Allocation of a portion of the allowance to one category of loans does not preclude its availability to absorb losses in other categories. ALL Balance at beginning of period Charge- offs Recoveries Net charge-offs Provisions charged to operations Balance at end of period (Dollars in thousands) Three Months Ended September 30, 2018 Real estate: Non-residential real estate owner occupied $ 6,426 $ (179 ) $ 15 $ (164 ) $ 164 $ 6,426 Non-residential real estate other 10,705 (8 ) — (8 ) (49 ) 10,648 Residential real estate permanent mortgage 3,307 (39 ) — (39 ) 43 3,311 Residential real estate all other 10,123 (71 ) 95 24 274 10,421 Commercial and financial: Non-consumer non-real estate 15,069 (343 ) 7 (336 ) (337 ) 14,396 Consumer non-real estate 2,839 (294 ) 70 (224 ) 298 2,913 Other loans 2,328 — 6 6 88 2,422 Acquired loans 1,403 (337 ) 6 (331 ) 266 1,338 Total $ 52,200 $ (1,271 ) $ 199 $ (1,072 ) $ 747 $ 51,875 Nine Months Ended September 30, 2018 Real estate: Non-residential real estate owner occupied $ 6,195 $ (198 ) $ 16 $ (182 ) $ 413 $ 6,426 Non-residential real estate other 10,519 (9 ) 39 30 99 10,648 Residential real estate permanent mortgage 3,226 (101 ) 26 (75 ) 160 3,311 Residential real estate all other 9,672 (312 ) 101 (211 ) 960 10,421 Commercial and financial: Non-consumer non-real estate 15,334 (652 ) 30 (622 ) (316 ) 14,396 Consumer non-real estate 2,793 (738 ) 194 (544 ) 664 2,913 Other loans 2,481 (2 ) 30 28 (87 ) 2,422 Acquired loans 1,446 (530 ) 29 (501 ) 393 1,338 Total $ 51,666 $ (2,542 ) $ 465 $ (2,077 ) $ 2,286 $ 51,875 ALL Balance at beginning of period Charge- offs Recoveries Net charge-offs Provisions charged to operations Balance at end of period (Dollars in thousands) Three Months Ended September 30, 2017 Real estate: Non-residential real estate owner occupied $ 5,685 $ (2 ) $ 1 $ (1 ) $ 261 $ 5,945 Non-residential real estate other 10,480 — 1 1 70 10,551 Residential real estate permanent mortgage 3,148 (90 ) 9 (81 ) 91 3,158 Residential real estate all other 8,912 (89 ) 13 (76 ) 503 9,339 Commercial and financial: Non-consumer non-real estate 13,643 (538 ) 24 (514 ) 1,838 14,967 Consumer non-real estate 2,706 (238 ) 57 (181 ) 207 2,732 Other loans 3,006 (47 ) — (47 ) 153 3,112 Acquired loans 1,425 (134 ) 7 (127 ) 153 1,451 Total $ 49,005 $ (1,138 ) $ 112 $ (1,026 ) $ 3,276 $ 51,255 Nine Months Ended September 30, 2017 Real estate: Non-residential real estate owner occupied $ 5,602 $ (74 ) $ 5 $ (69 ) $ 412 $ 5,945 Non-residential real estate other 10,793 (26 ) 3 (23 ) (219 ) 10,551 Residential real estate permanent mortgage 3,129 (246 ) 20 (226 ) 255 3,158 Residential real estate all other 8,622 (162 ) 30 (132 ) 849 9,339 Commercial and financial: Non-consumer non-real estate 12,421 (1,215 ) 986 (229 ) 2,775 14,967 Consumer non-real estate 2,804 (706 ) 140 (566 ) 494 2,732 Other loans 4,045 (1,321 ) 22 (1,299 ) 366 3,112 Acquired loans 1,277 (148 ) 65 (83 ) 257 1,451 Total $ 48,693 $ (3,898 ) $ 1,271 $ (2,627 ) $ 5,189 $ 51,255 The following table details the amount of ALL by class of loans for the period presented, detailed on the basis of the impairment methodology used by the Company. ALL September 30, 2018 December 31, 2017 Individually evaluated for impairment Collectively evaluated for impairment Individually evaluated for impairment Collectively evaluated for impairment (Dollars in thousands) Real estate: Non-residential real estate owner occupied. $ 891 $ 5,535 $ 656 $ 5,539 Non-residential real estate other 978 9,670 751 9,768 Residential real estate permanent mortgage 570 2,741 483 2,743 Residential real estate all other 3,263 7,158 2,761 6,911 Commercial and financial: Non-consumer non-real estate 3,486 10,910 4,651 10,683 Consumer non-real estate 346 2,567 429 2,364 Other loans 44 2,378 133 2,348 Acquired loans — 1,338 12 1,434 Total $ 9,578 $ 42,297 $ 9,876 $ 41,790 The following table details the loans outstanding by class of loans for the period presented, on the basis of the impairment methodology used by the Company. Loans September 30, 2018 December 31, 2017 Individually evaluated for impairment Collectively evaluated for impairment Loans acquired with deteriorated credit quality Individually evaluated for impairment Collectively evaluated for impairment Loans acquired with deteriorated credit quality (Dollars in thousands) Real estate: Non-residential real estate owner occupied $ 20,813 $ 609,609 $ — $ 15,281 $ 626,337 $ — Non-residential real estate other 22,363 1,095,087 — 17,013 1,109,578 — Residential real estate permanent mortgage 9,779 318,647 — 8,100 322,234 — Residential real estate all other 20,620 797,264 — 15,052 770,603 — Commercial and financial: Non-consumer non-real estate 20,664 1,249,416 — 31,349 1,253,056 — Consumer non-real estate 2,958 317,474 — 2,600 286,320 — Other loans 130 143,075 — 764 143,681 — Acquired loans 23,916 288,131 7,582 14,464 100,106 5,457 Total $ 121,243 $ 4,818,703 $ 7,582 $ 104,623 $ 4,611,915 $ 5,457 Transfers from Loans Transfers from loans to other real estate owned and repossessed assets are non-cash transactions, and are not included in the statements of cash flow. Transfers from loans to other real estate owned and repossessed assets during the periods presented, are summarized as follows: Nine Months Ended September 30, 2018 2017 (Dollars in thousands) Other real estate owned $ 2,944 $ 1,906 Repossessed assets 842 887 Total $ 3,786 $ 2,793

Intangible Assets

Intangible Assets	9 Months Ended
	Sep. 30, 2018
Goodwill And Intangible Assets Disclosure [Abstract]
Intangible Assets	( 5 ) INTANGIBLE ASSETS The following is a summary of intangible assets: Gross Carrying Amount Accumulated Amortization Net Carrying Amount (Dollars in thousands) As of September 30, 2018 Core deposit intangibles $ 25,907 $ (10,423 ) $ 15,484 Customer relationship intangibles 5,699 (4,028 ) 1,671 Mortgage servicing intangibles 403 (301 ) 102 Total $ 32,009 $ (14,752 ) $ 17,257 As of December 31, 2017 Core deposit intangibles $ 17,447 $ (8,451 ) $ 8,996 Customer relationship intangibles 5,699 (3,767 ) 1,932 Mortgage servicing intangibles 439 (285 ) 154 Total $ 23,585 $ (12,503 ) $ 11,082 The following is a summary of goodwill by business segment: Other Executive, Metropolitan Community Financial Operations Banks Banks Services & Support Consolidated (Dollars in thousands) Nine month ended September 30, 2018 Balance at beginning of period $ 8,078 $ 39,876 $ 5,464 $ 624 $ 54,042 Acquisitions 5,689 20,002 — — 25,691 Balance at end of period $ 13,767 $ 59,878 $ 5,464 $ 624 $ 79,733 Additional information for intangible assets can be found in Note (7) to the Company’s Annual Report on Form 10-K for the year ended December 31, 2017.

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	( 6 ) STOCK-BASED COMPENSATION The Company adopted a nonqualified incentive stock option plan (the “BancFirst ISOP”) in May 1986. The Company has amended the BancFirst ISOP since 1986 to increase the number of shares to be issued under the plan to 6,400,000 shares. At September 30, 2018, there were 297,970 shares available for future grants. The BancFirst ISOP will terminate on December 31, 2019, if not extended. The options vest and are exercisable beginning four years from the date of grant at the rate of 25% per year for four years. Options expire at the end of fifteen years from the date of grant. Options outstanding as of September 30, 2018 will become exercisable through the year 2025. The option price must be no less than 100% of the fair value of the stock relating to such option at the date of grant. In June 1999, the Company adopted the BancFirst Corporation Non-Employee Directors’ Stock Option Plan (the “BancFirst Directors’ Stock Option Plan”). Each non-employee director is granted an option for 10,000 shares. The Company has amended the BancFirst Directors’ Stock Option Plan since 1999 to increase the number of shares to be issued under the plan to 520,000 shares. At September 30, 2018, there were 40,000 shares available for future grants. The BancFirst Directors’ Stock Option Plan will terminate on December 31, 2019, if not extended. The options vest and are exercisable beginning one year from the date of grant at the rate of 25% per year for four years, and expire at the end of fifteen years from the date of grant. Options outstanding as of September 30, 2018 will become exercisable through the year 2022. The option price must be no less than 100% of the fair value of the stock relating to such option at the date of grant. The Company currently uses newly issued shares for stock option exercises, but reserves the right to use shares purchased under the Company’s Stock Repurchase Program (the “SRP”) in the future. The following table is a summary of the activity under both the BancFirst ISOP and the BancFirst Directors’ Stock Option Plan: Wgtd. Avg. Wgtd. Avg. Remaining Aggregate Exercise Contractual Intrinsic Options Price Term Value (Dollars in thousands, except option data) Nine Months Ended September 30, 2018 Outstanding at December 31, 2017 1,273,625 $ 25.90 Options granted 57,000 57.71 Options exercised (118,425 ) 17.37 Options canceled, forfeited, or expired (5,000 ) 48.02 Outstanding at September 30, 2018 1,207,200 28.14 9.70 Yrs $ 38,399 Exercisable at September 30, 2018 530,200 21.15 7.05 Yrs $ 20,574 The following table has additional information regarding options granted and options exercised under both the BancFirst ISOP and the BancFirst Directors’ Stock Option Plan: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (Dollars in thousands except per share data) Weighted average grant-date fair value per share of options granted $ 16.49 $ 11.63 $ 14.93 $ 11.21 Total intrinsic value of options exercised 766 1,493 4,593 7,138 Cash received from options exercised 413 856 2,057 4,113 Tax benefit realized from options exercised 195 578 1,170 2,761 The fair value of each option grant is estimated on the date of grant using the Black-Scholes option-pricing model and is based on certain assumptions including risk-free rate of return, dividend yield, stock price volatility and the expected term. The fair value of each option is expensed over its vesting period. The following table is a summary of the Company’s recorded stock-based compensation expense: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (Dollars in thousands) Stock-based compensation expense $ 353 $ 354 $ 981 $ 819 Tax benefit 90 137 250 317 Stock-based compensation expense, net of tax $ 263 $ 217 $ 731 $ 502 The Company will continue to amortize the unearned stock-based compensation expense over the remaining vesting period of approximately seven years. The following table shows the unearned stock-based compensation expense: September 30, 2018 (Dollars in thousands) Unearned stock-based compensation expense $ 3,350 The following table shows the assumptions used for computing stock-based compensation expense under the fair value method on options granted during the periods presented: Nine Months Ended September 30, 2018 2017 Risk-free interest rate 2.55 to 3.05% 2.15 to 2.38% Dividend yield 2.00% 2.00% Stock price volatility 23.05 to 23.46% 22.57 to 23.53% Expected term 10 Yrs 10 Yrs The risk-free interest rate is determined by reference to the spot zero-coupon rate for the U.S. Treasury security with a maturity similar to the expected term of the options. The dividend yield is the expected yield for the expected term. The stock price volatility is estimated from the recent historical volatility of the Company’s stock. The expected term is estimated from the historical option exercise experience. The Company accounts for forfeitures as they occur. In May 1999, the Company adopted the BancFirst Corporation Directors’ Deferred Stock Compensation Plan (the “BancFirst Deferred Stock Compensation Plan”). The Company has amended the BancFirst Deferred Stock Compensation Plan since 1999 to increase the number of shares to be issued under the plan to 222,220 shares. The BancFirst Deferred Stock Compensation Plan will terminate on December 31, 2019, if not extended. Under the plan, directors and members of the community advisory boards of the Company and its subsidiaries may defer up to 100% of their board fees. They are credited for each deferral with a number of stock units based on the current market price of the Company’s stock, which accumulate in an account until such time as the director or community board member terminates serving as a board member. Shares of common stock of the Company are then distributed to the terminating director or community board member based upon the number of stock units accumulated in his or her account. There were 3,891 and 9,918 shares of common stock distributed from the BancFirst Deferred Stock Compensation Plan during the nine months ended September 30, 2018 and September 30, 2017, respectively. A summary of the accumulated stock units is as follows: September 30, December 31, 2018 2017 Accumulated stock units 140,946 138,768 Average price $ 24.36 $ 22.84

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 2018
Equity [Abstract]
Stockholders' Equity	(7 ) STOCKHOLDERS’ EQUITY In November 1999, the Company adopted a Stock Repurchase Program (the “SRP”). The SRP may be used as a means to increase earnings per share and return on equity, to purchase treasury stock for the exercise of stock options or for distributions under the Deferred Stock Compensation Plan, to provide liquidity for optionees to dispose of stock from exercises of their stock options, and to provide liquidity for stockholders wishing to sell their stock. All shares repurchased under the SRP have been retired and not held as treasury stock. The timing, price and amount of stock repurchases under the SRP may be determined by management and approved by the Company’s Executive Committee. The following table is a summary of the shares under the program: Nine Months Ended September 30, 2018 2017 Number of shares repurchased — — Average price of shares repurchased $ — $ — Shares remaining to be repurchased 300,000 300,000 The Company and BancFirst are subject to risk-based capital guidelines issued by the Board of Governors of the Federal Reserve System and the Federal Deposit Insurance Corporation (“FDIC”). These guidelines are used to evaluate capital adequacy and involve both quantitative and qualitative evaluations of the Company’s and BancFirst’s assets, liabilities and certain off-balance-sheet items calculated under regulatory practices. Failure to meet the minimum capital requirements can initiate certain mandatory or discretionary actions by the regulatory agencies that could have a direct material effect on the Company’s financial statements. Management believes that as of September 30, 2018, the Company and BancFirst met all capital adequacy requirements to which they are subject. The actual and required capital amounts and ratios are shown in the following table: Required To Be Well For Capital With Capitalized Under Adequacy Capital Conservation Prompt Corrective Actual Purposes Buffer Action Provisions Amount Ratio Amount Ratio Amount Ratio Amount Ratio (Dollars in thousands) As of September 30, 2018: Total Capital (to Risk Weighted Assets)- BancFirst Corporation $ 875,460 16.39% $ 427,430 8.00% $ 527,609 9.875% N/A N/A BancFirst 745,152 13.96% 426,871 8.00% 526,919 9.875% $ 533,589 10.00% Common Equity Tier 1 Capital (to Risk Weighted Assets)- BancFirst Corporation $ 792,585 14.83% $ 240,430 4.50% $ 340,609 6.375% N/A N/A BancFirst 673,277 12.62% 240,115 4.50% 340,163 6.375% $ 346,833 6.50% Tier 1 Capital (to Risk Weighted Assets)- BancFirst Corporation $ 823,585 15.41% $ 320,573 6.00% $ 420,752 7.875% N/A N/A BancFirst 693,277 12.99% 320,153 6.00% 420,202 7.875% $ 426,871 8.00% Tier 1 Capital (to Total Assets)- BancFirst Corporation $ 823,585 10.93% $ 301,392 4.00% N/A N/A N/A N/A BancFirst 693,277 9.21% 301,193 4.00% N/A N/A $ 376,491 5.00% As of September 30, 2018, the most recent notification from the Federal Reserve Bank of Kansas City and the FDIC categorized BancFirst as “well capitalized” under the regulatory framework from prompt corrective action. The Company’s trust preferred securities have continued to be included in Tier 1 capital as the Company’s total assets do not exceed $15 billion. There are no conditions or events since the most recent notifications of BancFirst’s capital category that management believes would materially change its category under capital requirements existing as of the report date. Basel III Capital Rules Under the Basel III Capital Rules, in order to avoid limitations on capital distributions, including dividend payments and certain discretionary bonus payments to executive officers, a banking organization must hold a capital conservation buffer composed of CET1 capital above its minimum risk-based capital requirements. The implementation of the capital conservation buffer began on January 1, 2016 at the 0.625% level and will be phased in over a four-year period (increasing by that amount on each subsequent January 1, until it reaches 2.5% on January 1, 2019). Management believes that, as of September 30, 2018, the Company and BancFirst would meet all capital adequacy requirements under the Basel III Capital Rules on a fully phased-in basis as if such requirements were currently in effect.

Net Income Per Common Share

Net Income Per Common Share	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Net Income Per Common Share	( 8 ) NET INCOME PER COMMON SHARE Basic and diluted net income per common share based on weighted-average shares outstanding are calculated as follows: Income (Numerator) Shares (Denominator) Per Share Amount (Dollars in thousands, except per share data) Three Months Ended September 30, 2018 Basic Income available to common stockholders $ 32,883 32,742,480 $ 1.01 Dilutive effect of stock options — 761,663 Diluted Income available to common stockholders plus assumed exercises of stock options $ 32,883 33,504,143 $ 0.98 Three Months Ended September 30, 2017 Basic Income available to common stockholders $ 21,710 31,838,392 $ 0.68 Dilutive effect of stock options — 753,885 Diluted Income available to common stockholders plus assumed exercises of stock options $ 21,710 32,592,277 $ 0.67 Nine Months Ended September 30, 2018 Basic Income available to common stockholders $ 93,089 32,678,310 $ 2.85 Dilutive effect of stock options — 752,451 Diluted Income available to common stockholders plus assumed exercises of stock options $ 93,089 33,430,761 $ 2.78 Nine Months Ended September 30, 2017 Basic Income available to common stockholders $ 66,942 31,792,270 $ 2.11 Dilutive effect of stock options — 741,949 Diluted Income available to common stockholders plus assumed exercises of stock options $ 66,942 32,534,219 $ 2.06 The following table shows the number of options that were excluded from the computation of diluted net income per common share for each period because the options’ exercise prices were greater than the average market price of the common shares: Shares Three Months Ended September 30, 2018 83,799 Three Months Ended September 30, 2017 75,543 Nine Months Ended September 30, 2018 84,368 Nine Months Ended September 30, 2017 39,120

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	( 9 ) FAIR VALUE MEASUREMENTS Accounting standards define fair value as the price that would be received to sell an asset or the price paid to transfer a liability in the principal or most advantageous market available to the entity in an orderly transaction between market participants on the measurement date. FASB ASC Topic 820 establishes a fair value hierarchy for valuation inputs that gives the highest priority to quoted prices in active markets for identical assets or liabilities and the lowest priority to unobservable inputs. The fair value hierarchy is as follows: • Level 1 Inputs to the valuation methodology are quoted prices (unadjusted) for identical assets or liabilities in active markets. • Level 2 Inputs to the valuation methodology include quoted prices for similar assets and liabilities in active markets, and inputs that are observable for the asset and liability, either directly or indirectly, for substantially the full term of the financial instrument. • Level 3 Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Level 3 assets and liabilities include financial instruments whose values are determined using pricing models, discounted cash flow methodologies, or similar techniques, as well as instruments for which the determination of fair value requires significant management judgment or estimation. This category includes certain impaired loans, repossessed assets, other real estate owned, goodwill and other intangible assets. Financial Assets and Financial Liabilities Measured at Fair Value on a Recurring Basis A description of the valuation methodologies and key inputs used to measure financial assets and financial liabilities at fair value on a recurring basis, as well as the general classification of such instruments pursuant to the valuation hierarchy, is set forth below. These valuation methodologies were applied to the following categories of the Company’s financial assets and financial liabilities. Securities Available for Sale Securities classified as available for sale are reported at fair value. U.S. Treasuries are valued using Level 1 inputs. Other securities available for sale including U.S. federal agencies, registered mortgage backed securities and state and political subdivisions are valued using prices from an independent pricing service utilizing Level 2 data. The fair value measurements consider observable data that may include dealer quotes, market spreads, cash flows, the U.S. Treasury yield curve, live trading levels, trade execution data, market consensus prepayment speeds, credit information and the bond’s terms and conditions, among other things. The Company also invests in private label mortgage backed securities for which observable information is not readily available. These securities are reported at fair value utilizing Level 3 inputs. For these securities, management determines the fair value based on replacement cost, the income approach or information provided by outside consultants or lead investors. The Company reviews the prices for Level 1 and Level 2 securities supplied by the independent pricing service for reasonableness and to ensure such prices are aligned with traditional pricing matrices. In general, the Company does not purchase investment portfolio securities that are esoteric or that have complicated structures. The Company’s portfolio primarily consists of traditional investments including U.S. Treasury obligations, federal agency mortgage pass-through securities, general obligation municipal bonds and a small amount of municipal revenue bonds. Pricing for such instruments is fairly generic and is easily obtained. For in-state bond issues that have relatively low issue sizes and liquidity, the Company utilizes the same parameters for pricing mentioned in the preceding paragraph adjusted for the specific issue. Periodically, the Company will validate prices supplied by the independent pricing service by comparison to prices obtained from third party sources. Equity Securities The Company invests in equity securities without readily determinable fair values and utilizes Level 3 inputs. Beginning January 1, 2018, upon adoption of ASU 2016-01, these securities are reported at cost minus impairment, if any, plus or minus changes resulting from observable price changes in orderly transactions for the identical or a similar investment of the same issuer. The realized and unrealized gains and losses are reported as securities transactions in the noninterest income section of the consolidated statements of comprehensive income. For periods prior to January 1, 2018, equity securities were classified as available-for-sale and stated at fair value with unrealized gains and losses reported as a separate component of accumulated other comprehensive income (loss), net of tax. Derivatives Derivatives are reported at fair value utilizing Level 2 inputs. The Company obtains dealer and market quotations to value its oil and gas swaps and options. The Company utilizes dealer quotes and observable market data inputs to substantiate internal valuation models. Loans Held For Sale The Company originates mortgage loans to be sold. At the time of origination, the acquiring bank has already been determined and the terms of the loan, including interest rate, have already been set by the acquiring bank, allowing the Company to originate the loan at fair value. Mortgage loans are generally sold within 30 days of origination. Loans held for sale are valued using Level 2 inputs. Gains or losses recognized upon the sale of the loans are determined on a specific identification basis. The following table summarizes financial assets and financial liabilities measured at fair value on a recurring basis as of the periods presented, segregated by the level of the valuation inputs within the fair value hierarchy utilized to measure fair value: Level 1 Inputs Level 2 Inputs Level 3 Inputs Total Fair Value (Dollars in thousands) September 30, 2018 Securities available for sale: U.S. Treasury $ 397,466 $ — $ — $ 397,466 U.S. federal agencies — 31,840 — 31,840 Mortgage-backed securities — 2,691 13,443 16,134 States and political subdivisions — 30,200 — 30,200 Equity securities — — 6,509 6,509 Derivative assets — 247 — 247 Derivative liabilities — 229 — 229 Loans held for sale — 4,739 — 4,739 December 31, 2017 Securities available for sale: U.S. Treasury $ 312,802 $ — $ — $ 312,802 U.S. federal agencies — 88,851 — 88,851 Mortgage-backed securities — 3,509 14,467 17,976 States and political subdivisions — 42,370 — 42,370 Equity securities — — 5,704 5,704 Derivative assets — 295 — 295 Derivative liabilities — 261 — 261 Loans held for sale — 6,173 — 6,173 The changes in Level 3 assets measured at estimated fair value on a recurring basis during the periods presented were as follows: Nine Months Ended September 30, Twelve Months Ended December 31, 2018 2017 (Dollars in thousands) Balance at the beginning of the year $ 20,171 $ 21,385 Purchases 2,118 1,668 Settlements (2,385 ) (722 ) Sales (73 ) (5,412 ) Gains included in earnings 67 4,060 Total unrealized losses 54 (808 ) Balance at the end of the period $ 19,952 $ 20,171 The Company’s policy is to recognize transfers in and transfers out of Levels 1, 2 and 3 as of the end of the reporting period. During the nine months ended September 30, 2018 and 2017, the Company did not transfer any securities between levels in the fair value hierarchy. Financial Assets and Financial Liabilities Measured at Fair Value on a Nonrecurring Basis Certain financial assets and financial liabilities are measured at fair value on a nonrecurring basis; that is, the instruments are not measured at fair value on an ongoing basis but are subject to fair value adjustments in certain circumstances (for example, when there is evidence of impairment). These financial assets and financial liabilities are reported at fair value utilizing Level 3 inputs. Impaired loans are reported at the fair value of the underlying collateral if repayment is dependent on liquidation of the collateral. In no case does the fair value of an impaired loan exceed the fair value of the underlying collateral. The impaired loans are adjusted to fair value through a specific allocation of the allowance for loan losses or a direct charge-down of the loan. Repossessed assets, upon initial recognition, are measured and adjusted to fair value through a charge-off to the allowance for possible loan losses based upon the fair value of the repossessed asset. Other real estate owned is revalued at fair value subsequent to initial recognition, with any losses recognized in net expense from other real estate owned. The following table summarizes assets measured at fair value on a nonrecurring basis. The fair value represents end of period values, which approximate fair value measurements that occurred on various measurement dates throughout the period: Total Fair Value Level 3 (Dollars in thousands) As of and for the Year-to-date Period Ended September 30, 2018 Impaired loans (less specific allowance) $ 39,620 Repossessed assets 244 Other real estate owned 4,610 As of and for the Year-to-date Period Ended December 31, 2017 Impaired loans (less specific allowance) $ 34,041 Repossessed assets 288 Other real estate owned 1,995 Estimated Fair Value of Financial Instruments The Company is required under current authoritative accounting guidance to disclose the estimated fair value of their financial instruments that are not recorded at fair value. For the Company, as for most financial institutions, substantially all of its assets and liabilities are considered financial instruments. A financial instrument is defined as cash, evidence of an ownership interest in an entity or a contract that creates a contractual obligation or right to deliver or receive cash or another financial instrument from a second entity. The following methods and assumptions were used to estimate the fair value of each class of financial instruments: Cash and Cash Equivalents Include: Cash and Due from Banks, Federal Funds Sold and Interest-Bearing Deposits The carrying amount of these short-term instruments is a reasonable estimate of fair value. Securities Held for Investment For securities held for investment, which are generally traded in secondary markets, fair values are based on quoted market prices or dealer quotes, if available. If a quoted market price is not available, fair value is estimated using quoted market prices for similar securities making adjustments for credit or liquidity if applicable. Loans To determine the fair value of loans, the Company uses an exit price calculation, which takes into account factors such as liquidity, credit and the nonperformance risk of loans. For certain homogeneous categories of loans, such as some residential mortgages, fair values are estimated using the quoted market prices for securities backed by similar loans, adjusted for differences in loan characteristics. The fair values of other types of loans are estimated by discounting the future cash flows using the current rates at which similar loans would be made to borrowers with similar credit ratings and for the same remaining maturities. Deposits The fair values of transaction and savings accounts are the amounts payable on demand at the reporting date. The fair values of fixed-maturity certificates of deposit are estimated using the rates currently offered for deposits of similar remaining maturities. Short-term Borrowings The amounts payable on these short-term instruments are reasonable estimates of fair value. Junior Subordinated Debentures The fair values of junior subordinated debentures are estimated using the rates that would be charged for junior subordinated debentures of similar remaining maturities. Loan Commitments and Letters of Credit The fair values of commitments are estimated using the fees currently charged to enter into similar agreements, taking into account the terms of the agreements. The fair values of letters of credit are based on fees currently charged for similar agreements. The estimated fair values of the Company’s financial instruments that are reported at amortized cost in the Company’s consolidated balance sheets, segregated by the level of valuation inputs within the fair value hierarchy utilized to measure fair value, are as follows: September 30, December 31, 2018 2017 Carrying Amount Fair Value Carrying Amount Fair Value (Dollars in thousands) FINANCIAL ASSETS Level 2 inputs: Cash and cash equivalents $ 1,792,766 $ 1,792,766 $ 1,758,575 $ 1,758,575 Securities held for investment 940 947 1,792 1,803 Level 3 inputs: Securities held for investment 500 500 500 500 Loans, net of allowance for loan losses 4,895,653 4,854,167 4,670,329 4,663,608 FINANCIAL LIABILITIES Level 2 inputs: Deposits 6,643,131 6,760,191 6,415,045 6,490,309 Short-term borrowings 2,200 2,200 900 900 Junior subordinated debentures 31,959 34,795 31,959 34,661 OFF-BALANCE SHEET FINANCIAL INSTRUMENTS Loan commitments 2,006 1,839 Letters of credit 425 428 Non-financial Assets and Non-financial Liabilities Measured at Fair Value The Company has no non-financial assets or non-financial liabilities measured at fair value on a recurring basis. Certain non-financial assets and non-financial liabilities measured at fair value on a nonrecurring basis include intangible assets (excluding mortgage service rights, which are valued periodically) and other non-financial long-lived assets measured at fair value and adjusted for impairment. These items are evaluated at least annually for impairment. The overall levels of non-financial assets and non-financial liabilities measured at fair value on a nonrecurring basis were not considered to be significant to the Company at September 30, 2018 or December 31, 2017.

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Segment Information	(10) SEGMENT INFORMATION The Company evaluates its performance with an internal profitability measurement system that measures the profitability of its business units on a pre-tax basis. The four principal business units are metropolitan banks, community banks, other financial services and executive, operations and support. Metropolitan and community banks offer traditional banking products such as commercial and retail lending and a full line of deposit accounts. Metropolitan banks consist of banking locations in the metropolitan Oklahoma City and Tulsa areas. Community banks consist of banking locations in communities throughout Oklahoma. Other financial services are specialty product business units including guaranteed small business lending, residential mortgage lending, trust services, securities brokerage, electronic banking and insurance. The executive, operations and support groups represent executive management, operational support and corporate functions that are not allocated to the other business units. The results of operations and selected financial information for the four business units are as follows: Metropolitan Banks Community Banks Other Financial Services Executive, Operations & Support Eliminations Consolidated (Dollars in thousands) Three Months Ended September 30, 2018 Net interest income (expense) $ 21,313 $ 42,773 $ 1,241 $ 346 $ — $ 65,673 Noninterest income 4,266 15,404 10,264 36,503 (33,636 ) 32,801 Income before taxes 16,538 27,515 4,440 26,344 (32,919 ) 41,918 Three Months Ended September 30, 2017 Net interest income (expense) $ 18,617 $ 37,310 $ 1,332 $ (26 ) $ — $ 57,233 Noninterest income 3,981 13,884 9,217 24,470 (22,383 ) 29,169 Income before taxes 11,499 23,810 3,762 15,137 (21,682 ) 32,526 Nine Months Ended September 30, 2018 Net interest income (expense) $ 62,701 $ 126,223 $ 4,074 $ 590 $ — $ 193,588 Noninterest income 12,391 44,189 28,784 102,306 (94,322 ) 93,348 Income before taxes 46,157 81,805 13,511 69,881 (92,659 ) 118,695 Nine Months Ended September 30, 2017 Net interest income (expense) $ 54,969 $ 109,480 $ 4,525 $ (534 ) $ — $ 168,440 Noninterest income 11,748 40,821 24,983 74,586 (66,901 ) 85,237 Income before taxes 36,357 71,038 10,526 47,368 (65,942 ) 99,347 Total Assets: September 30, 2018 $ 2,724,502 $ 4,841,853 $ 80,411 $ 945,221 $ (989,549 ) $ 7,602,438 December 31, 2017 2,552,024 4,544,196 117,332 885,590 (845,986 ) 7,253,156 The financial information for each business unit is presented on the basis used internally by management to evaluate performance and allocate resources. The Company utilizes a transfer pricing system to allocate the benefit or cost of funds provided or used by the various business units. Certain services provided by the support group to other business units, such as item processing, are allocated at rates approximating the cost of providing the services. Eliminations are adjustments to consolidate the business units and companies. Capital expenditures are generally charged to the business unit using the asset.

Description of Business and S_2

Description of Business and Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited interim consolidated financial statements include the accounts of BancFirst Corporation, Council Oak Partners, LLC, BancFirst Insurance Services, Inc., BancFirst Risk and Insurance Company and BancFirst and its subsidiaries. The principal operating subsidiaries of BancFirst are Council Oak Investment Corporation, Council Oak Real Estate, Inc., BFTower, LLC and BancFirst Agency, Inc. All significant intercompany accounts and transactions have been eliminated. Assets held in a fiduciary or agency capacity are not assets of the Company and, accordingly, are not included in the unaudited interim consolidated financial statements. The accompanying unaudited interim consolidated financial statements and notes are presented in accordance with the instructions for Form 10-Q. The information contained in the financial statements and footnotes included in BancFirst Corporation’s Annual Report on Form 10-K for the year ended December 31, 2017, should be referred to in connection with these unaudited interim consolidated financial statements. Operating results for the interim periods disclosed herein are not necessarily indicative of the results that may be expected for a full year or any future period. The unaudited interim consolidated financial statements contained herein reflect all adjustments which are, in the opinion of management, necessary to provide a fair statement of the financial position and results of operations of the Company for the interim periods presented. All such adjustments are of a normal and recurring nature. There have been no significant changes in the accounting policies of the Company since December 31, 2017, the date of the most recent annual report.
Reclassifications	Reclassifications Certain items in prior financial statements have been reclassified to conform to the current presentation. Such reclassifications had no effect on previously reported cash flows, stockholders’ equity or comprehensive income.
Use of Estimates in the Preparation of Financial Statements	Use of Estimates in the Preparation of Financial Statements The preparation of financial statements in conformity with accounting principles generally accepted in the United States inherently involves the use of estimates and assumptions that affect the amounts reported in the financial statements and the related disclosures. These estimates relate principally to the determination of the allowance for loan losses, income taxes, the fair value of financial instruments and the valuation of intangibles. Such estimates and assumptions may change over time and actual amounts realized may differ from those reported.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Standards Adopted During Current Period: In February 2018, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2018-2, Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income. ASU 2018-2 allows a reclassification from accumulated other comprehensive income (loss) to retained earnings for stranded tax effects resulting from the Tax Cuts and Jobs Act. ASU 2018-2 is effective for fiscal years beginning after December 15, 2018 with early adoption permitted. The Company elected to early adopt the provisions of ASU 2018-2 and the amount to reclassify was immaterial to the Company’s financial statements. The Company’s policy is to release material stranded tax effects on a specific identification basis. In May 2017, the FASB issued ASU No. 2017-09, “Compensation – Stock Compensation (Topic 718): Scope of Modification Accounting.” The amendments in this update provide guidance about types of changes to the terms of conditions of share-based payment awards that would require an entity to apply modification accounting under ASC 718. ASU 2017-09 was adopted on January 1, 2018 and did not have a significant impact on the Company’s financial statements and no prior periods were adjusted. In January 2017, the FASB issued ASU No. 2017-04, “Intangibles – Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment.” ASU 2017-04 removes the second step of goodwill testing. ASU 2017-04 is effective for fiscal years beginning after December 31, 2019 with early adoption permitted. The Company elected to early adopt ASU 2017-4 and it did not have a significant impact on the Company’s financial statements. In January 2017, the FASB issued ASU No. 2017-01, “Business Combinations (Topic 805): Clarifying the Definition of a Business.” ASU 2017-01 clarifies the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of a business. ASU 2017-01 was adopted on January 1, 2018 and did not have a significant impact on the Company’s financial statements. In October 2016, the FASB issued ASU No. 2016-16, “Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory.” ASU 2016-16 provides guidance stating that an entity should recognize the income tax consequences of an intra-entity transfer of an asset other than inventory when the transfer occurs. ASU 2016-16 was adopted on January 1, 2018 and did not have a significant impact on the Company’s financial statements and no prior periods were adjusted. In August 2016, the FASB issued ASU No. 2016-15, “Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments.” ASU 2016-15 is intended to reduce the diversity in practice around how certain transactions are classified within the statement of cash flows. ASU 2016-15 was adopted on January 1, 2018 and did not have a significant impact on the Company’s financial statements. In January 2016, the FASB issued ASU No. 2016-01, “Financial Instruments – Overall (Subtopic 825-10).” ASU 2016-01 requires all equity investments (except those accounted for under the equity method of accounting or those that result in consolidation of the investee) to be measured at fair value with changes in the fair value recognized through net income. The adoption of the guidance resulted in a $618,000 decrease to retained earnings and a $618,000 increase to accumulated other comprehensive income. Additional income of $41,200 was recorded in the consolidated statement of comprehensive income during 2018 as a result of changes to the accounting for equity investments. Further, the Company’s securities disclosures in Note (3) have been revised to exclude equity investments in 2018 and fair value disclosures in Note (9) have incorporated the revised disclosure requirements for financial investments. ASU 2016-01 also emphasizes the existing requirement to use exit prices to measure fair value for disclosure purposes and clarifies that entities should not make use of a practicability exception in determining the fair value of loans. Accordingly, we refined the calculation used to determine the disclosed fair value of loans held for investment as part of adopting this standard. The refined calculation did not have a significant impact on fair value disclosures. In January 2014, the FASB issued ASU No. 2014-09, “Revenue from Contracts with Customer (Topic 606).” ASU 2014-09 implements a comprehensive new revenue recognition standard that will supersede substantially all existing revenue recognition guidance. The new standard’s core principle is that a company will recognize revenue when it transfers promised goods or services to customers in a manner that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. The guidance does not apply to revenue associated with financial instruments, including loans and securities that are accounted for under other GAAP, which comprises a significant portion of the Company’s revenue stream. ASU 2014-09 was adopted on January 1, 2018 and did not have a significant impact on the Company’s financial statements. Standards Not Yet Adopted: In August 2018, the FASB issued ASU No. 2018-13, “Fair Value Measurement (Topic 820).” ASU 2018-13 removes, modifies and adds disclosure requirements on fair value measurements. ASU 2018-13 will be effective for the Company on January 1, 2020. Early adoption is permitted. In addition, early adoption of any removed or modified disclosures and delayed adoption of the additional disclosures until the effective date is also permitted. In June 2016, the FASB issued ASU No. 2016-13, “Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments.” ASU 2016-13 requires a financial asset measured at amortized cost basis to be presented at the net amount expected to be collected. The measurement of expected credit losses is based on relevant information about past events, including historical experience, current conditions, and reasonable and supportable forecasts that affect the collectability of the reported amount. ASU 2016-13 requires enhanced disclosures related to the significant estimates and judgements used in estimating credit losses, as well as the credit quality and underwriting standards of an organization’s portfolio. In addition, ASU 2016-13 amends the accounting for credit losses on available-for-sale debt securities and purchased financial assets with credit deterioration. ASU 2016-13 will be effective for the Company on January 1, 2020. The Company is currently evaluating the potential impact of ASU 2016-13 on its financial statements. In that regard, the Company has formed a task force under the direction of its Chief Financial Officer. The Company is currently developing an implementation plan to include assessment of process, portfolio segmentation, model development, system requirements and the identification of data and resource need, among other things. In February 2016, the FASB issued ASU No. 2016-02, “Leases - (Topic 842).” ASU 2016-02 requires that lessees recognize on the balance sheet the assets and liabilities for the rights and obligations created by leases. The amendments are effective for annual periods, and interim reporting periods within those annual periods, beginning after December 15, 2018. The Company .

Securities (Tables)

Securities (Tables)	9 Months Ended
	Sep. 30, 2018
Investments Debt And Equity Securities [Abstract]
Summary of Securities Held for Investment and Securities Available for Sale	The following table summarizes securities held for investment and securities available for sale: September 30, 2018 December 31, 2017 (Dollars in thousands) Held for investment, at cost (fair value: $1,447 and $2,303, respectively) $ 1,440 $ 2,292 Available for sale, at fair value 475,640 467,703 Total $ 477,080 $ 469,995
Summary of Amortized Cost and Estimated Fair Values of Securities Held for Investment	The following table summarizes the amortized cost and estimated fair values of securities held for investment: Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value September 30, 2018 (Dollars in thousands) Mortgage backed securities (1) $ 145 $ 6 $ — $ 151 States and political subdivisions 795 1 — 796 Other securities 500 — — 500 Total $ 1,440 $ 7 $ — $ 1,447 December 31, 2017 Mortgage backed securities (1) $ 187 $ 10 $ — $ 197 States and political subdivisions 1,605 3 (2 ) 1,606 Other securities 500 — — 500 Total $ 2,292 $ 13 $ (2 ) $ 2,303
Summary of Amortized Cost and Estimated Fair Values of Securities Available for Sale	The following table summarizes the amortized cost and estimated fair values of securities available for sale: Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value September 30, 2018 (Dollars in thousands) U.S. treasuries $ 403,213 $ — $ (5,747 ) $ 397,466 U.S. federal agencies 32,017 1 (178 ) 31,840 Mortgage backed securities (1) 16,581 119 (566 ) 16,134 States and political subdivisions 30,098 262 (160 ) 30,200 Total $ 481,909 $ 382 $ (6,651 ) $ 475,640 December 31, 2017 U.S. treasuries $ 314,905 $ — $ (2,103 ) $ 312,802 U.S. federal agencies 89,098 82 (329 ) 88,851 Mortgage backed securities (1) 18,358 204 (586 ) 17,976 States and political subdivisions 41,937 554 (121 ) 42,370 Equity securities (2) 6,527 71 (894 ) 5,704 Total $ 470,825 $ 911 $ (4,033 ) $ 467,703 (1) Primarily consists of FHLMC, FNMA, GNMA and mortgage backed securities through U.S. agencies. (2) Consisted of equity securities that are included in other assets in 2018.
Maturity of Securities	The maturities of securities held for investment and available for sale are summarized in the following table using contractual maturities. Actual maturities may differ from contractual maturities due to obligations that are called or prepaid. For purposes of the maturity table, mortgage-backed securities, which are not due at a single maturity date, have been presented at their contractual maturity. September 30, 2018 December 31, 2017 Amortized Cost Estimated Fair Value Amortized Cost Estimated Fair Value (Dollars in thousands) Held for Investment Contractual maturity of debt securities: Within one year $ 495 $ 496 $ 1,036 $ 1,034 After one year but within five years 370 371 623 627 After five years but within ten years 570 575 625 633 After ten years 5 5 8 9 Total $ 1,440 $ 1,447 $ 2,292 $ 2,303 Available for Sale Contractual maturity of debt securities: Within one year $ 61,869 $ 61,656 $ 113,225 $ 112,974 After one year but within five years 368,309 362,723 289,038 287,058 After five years but within ten years 5,047 5,225 6,222 6,500 After ten years 46,684 46,036 55,813 55,467 Total debt securities 481,909 475,640 464,298 461,999 Equity securities — — 6,527 5,704 Total $ 481,909 $ 475,640 $ 470,825 $ 467,703
Company's Book Value of Pledged Securities	The following table is a summary of the Company’s book value of securities that were pledged as collateral for public funds on deposit, repurchase agreements and for other purposes as required or permitted by law: September 30, 2018 December 31, 2017 (Dollars Book value of pledged securities $ 428,057 $ 440,069

Loans and Allowance for Loan _2

Loans and Allowance for Loan Losses (Tables)	9 Months Ended
	Sep. 30, 2018
Receivables [Abstract]
Schedule of Loans Outstanding by Category	The following is a schedule of loans outstanding by category: September 30, 2018 December 31, 2017 Amount Percent Amount Percent (Dollars in thousands) Commercial and financial: Commercial and industrial $ 1,042,237 21.07 % $ 995,207 21.08 % Oil & gas production and equipment 98,324 1.99 95,574 2.02 Agriculture 127,904 2.59 141,249 2.99 State and political subdivisions: Taxable 79,832 1.61 73,827 1.56 Tax-exempt 41,368 0.84 48,626 1.03 Real estate: Construction 446,046 9.02 437,277 9.26 Farmland 217,191 4.38 195,162 4.13 One to four family residences 972,922 19.66 875,766 18.55 Multifamily residential properties 62,555 1.26 46,030 0.98 Commercial 1,497,894 30.28 1,487,927 31.51 Consumer 323,952 6.55 284,373 6.02 Other (not classified above) 37,303 0.75 40,977 0.87 Total loans $ 4,947,528 100.00 % $ 4,721,995 100.00 %
Summary of Nonperforming and Restructured Assets	The following is a summary of nonperforming and restructured assets: September 30, December 31, 2018 2017 (Dollars in thousands) Past due 90 days or more and still accruing $ 4,073 $ 2,893 Nonaccrual 26,880 31,943 Restructured 13,557 4,720 Total nonperforming and restructured loans 44,510 39,556 Other real estate owned and repossessed assets 7,072 4,424 Total nonperforming and restructured assets $ 51,582 $ 43,980
Summary of Amounts Included in Nonaccrual Loans Segregated by Class of Loans	Loans are segregated into classes based upon the nature of the collateral and the borrower. These classes are used to estimate the allowance for loan losses. The following table is a summary of amounts included in nonaccrual loans, segregated by class of loans. Residential real estate refers to one-to-four family real estate. September 30, 2018 December 31, 2017 (Dollars in thousands) Real estate: Non-residential real estate owner occupied $ 1,526 $ 1,108 Non-residential real estate other 7,125 9,809 Residential real estate permanent mortgage 1,043 781 Residential real estate all other 4,911 3,980 Commercial and financial: Non-consumer non-real estate 6,032 7,785 Consumer non-real estate 416 250 Other loans 427 5,596 Acquired loans 5,400 2,634 Total $ 26,880 $ 31,943
Age Analysis of Past Due Loans Segregated by Class of Loans	Loans are considered past due if the required principal and interest payments have not been received as of the date such payments were due. The following table presents an age analysis of past due loans, segregated by class of loans: Age Analysis of Past Due Loans 30-59 Days Past Due 60-89 Days Past Due 90 Days and Greater Total Past Due Loans Current Loans Total Loans Accruing Loans 90 Days or More Past Due (Dollars in thousands) As of September 30, 2018 Real estate: Non-residential real estate owner occupied $ 977 $ 1,106 $ 811 $ 2,894 $ 627,528 $ 630,422 $ 90 Non-residential real estate other 4,964 385 172 5,521 1,111,929 1,117,450 57 Residential real estate permanent mortgage 3,910 1,318 961 6,189 322,237 328,426 427 Residential real estate all other 2,034 2,790 2,333 7,157 810,727 817,884 845 Commercial and financial: Non-consumer non-real estate 2,573 1,469 2,222 6,264 1,263,816 1,270,080 1,070 Consumer non-real estate 1,721 530 552 2,803 317,629 320,432 345 Other loans 514 — 372 886 142,319 143,205 128 Acquired loans 2,927 2,175 4,164 9,266 310,363 319,629 1,111 Total $ 19,620 $ 9,773 $ 11,587 $ 40,980 $ 4,906,548 $ 4,947,528 $ 4,073 As of December 31, 2017 Real estate: Non-residential real estate owner occupied $ 998 $ 68 $ 977 $ 2,043 $ 639,575 $ 641,618 $ 84 Non-residential real estate other 2,905 271 2,112 5,288 1,121,303 1,126,591 432 Residential real estate permanent mortgage 2,211 403 977 3,591 326,743 330,334 584 Residential real estate all other 1,739 749 1,377 3,865 781,790 785,655 973 Commercial and financial: Non-consumer non-real estate 2,210 706 1,785 4,701 1,279,704 1,284,405 403 Consumer non-real estate 2,085 670 293 3,048 285,872 288,920 194 Other loans 506 103 3,916 4,525 139,920 144,445 — Acquired loans 753 192 713 1,658 118,369 120,027 223 Total $ 13,407 $ 3,162 $ 12,150 $ 28,719 $ 4,693,276 $ 4,721,995 $ 2,893
Impaired Loans Segregated by Class of Loans	The following table presents impaired loans, segregated by class of loans. During the period ended September 30, 2018 no material amount of interest income was recognized on impaired loans subsequent to their classification as impaired. During the period ended September 30, 2017, $2.3 million of interest income was recognized on impaired loans subsequent to their classification as impaired. Impaired Loans Unpaid Principal Balance Recorded Investment with Allowance Related Allowance Average Recorded Investment (Dollars in thousands) As of September 30, 2018 Real estate: Non-residential real estate owner occupied $ 8,187 $ 8,063 $ 353 $ 7,877 Non-residential real estate other 8,262 7,753 333 8,678 Residential real estate permanent mortgage 1,842 1,634 145 1,746 Residential real estate all other 6,762 6,507 2,310 6,678 Commercial and financial: Non-consumer non-real estate 19,458 12,065 2,234 13,359 Consumer non-real estate 897 825 108 818 Other loans 772 558 43 456 Acquired loans 10,784 7,745 4 7,442 Total $ 56,964 $ 45,150 $ 5,530 $ 47,054 As of December 31, 2017 Real estate: Non-residential real estate owner occupied $ 2,011 $ 1,945 $ 141 $ 1,858 Non-residential real estate other 10,323 10,240 496 3,975 Residential real estate permanent mortgage 1,745 1,542 146 1,440 Residential real estate all other 5,837 5,549 2,135 5,258 Commercial and financial: Non-consumer non-real estate 18,101 11,158 2,412 11,131 Consumer non-real estate 545 514 127 541 Other loans 6,092 5,595 178 7,439 Acquired loans 4,737 3,145 12 3,539 Total $ 49,391 $ 39,688 $ 5,647 $ 35,181
Internal Loan Grading by Class of Loans	The following table presents internal loan grading by class of loans: Internal Loan Grading Grade 1 2 3 4 5 Total (Dollars in thousands) As of September 30, 2018 Real estate: Non-residential real estate owner occupied $ 478,014 $ 131,597 $ 19,221 $ 1,590 $ — $ 630,422 Non-residential real estate other 913,259 181,829 15,238 7,124 — 1,117,450 Residential real estate permanent mortgage 280,194 38,452 8,093 1,687 — 328,426 Residential real estate all other 641,246 156,018 15,000 5,620 — 817,884 Commercial and financial: Non-consumer non-real estate 980,535 268,882 14,915 5,748 — 1,270,080 Consumer non-real estate 297,516 19,975 2,202 739 — 320,432 Other loans 137,705 5,304 157 39 — 143,205 Acquired loans 188,452 99,686 25,082 6,160 249 319,629 Total $ 3,916,921 $ 901,743 $ 99,908 $ 28,707 $ 249 $ 4,947,528 As of December 31, 2017 Real estate: Non-residential real estate owner occupied $ 520,641 $ 105,696 $ 13,852 $ 1,429 $ — $ 641,618 Non-residential real estate other 931,295 178,282 14,290 2,724 — 1,126,591 Residential real estate permanent mortgage 289,200 33,033 6,352 1,749 — 330,334 Residential real estate all other 621,401 149,201 9,418 5,635 — 785,655 Commercial and financial: Non-consumer non-real estate 1,018,172 234,884 24,322 6,997 30 1,284,405 Consumer non-real estate 268,826 17,499 2,038 557 — 288,920 Other loans 136,617 5,668 1,203 957 — 144,445 Acquired loans 65,685 34,418 17,113 2,811 — 120,027 Total $ 3,851,837 $ 758,681 $ 88,588 $ 22,859 $ 30 $ 4,721,995
Activity in ALL by Class of Loans	The following table details activity in the ALL by class of loans for the period presented. Allocation of a portion of the allowance to one category of loans does not preclude its availability to absorb losses in other categories. ALL Balance at beginning of period Charge- offs Recoveries Net charge-offs Provisions charged to operations Balance at end of period (Dollars in thousands) Three Months Ended September 30, 2018 Real estate: Non-residential real estate owner occupied $ 6,426 $ (179 ) $ 15 $ (164 ) $ 164 $ 6,426 Non-residential real estate other 10,705 (8 ) — (8 ) (49 ) 10,648 Residential real estate permanent mortgage 3,307 (39 ) — (39 ) 43 3,311 Residential real estate all other 10,123 (71 ) 95 24 274 10,421 Commercial and financial: Non-consumer non-real estate 15,069 (343 ) 7 (336 ) (337 ) 14,396 Consumer non-real estate 2,839 (294 ) 70 (224 ) 298 2,913 Other loans 2,328 — 6 6 88 2,422 Acquired loans 1,403 (337 ) 6 (331 ) 266 1,338 Total $ 52,200 $ (1,271 ) $ 199 $ (1,072 ) $ 747 $ 51,875 Nine Months Ended September 30, 2018 Real estate: Non-residential real estate owner occupied $ 6,195 $ (198 ) $ 16 $ (182 ) $ 413 $ 6,426 Non-residential real estate other 10,519 (9 ) 39 30 99 10,648 Residential real estate permanent mortgage 3,226 (101 ) 26 (75 ) 160 3,311 Residential real estate all other 9,672 (312 ) 101 (211 ) 960 10,421 Commercial and financial: Non-consumer non-real estate 15,334 (652 ) 30 (622 ) (316 ) 14,396 Consumer non-real estate 2,793 (738 ) 194 (544 ) 664 2,913 Other loans 2,481 (2 ) 30 28 (87 ) 2,422 Acquired loans 1,446 (530 ) 29 (501 ) 393 1,338 Total $ 51,666 $ (2,542 ) $ 465 $ (2,077 ) $ 2,286 $ 51,875 ALL Balance at beginning of period Charge- offs Recoveries Net charge-offs Provisions charged to operations Balance at end of period (Dollars in thousands) Three Months Ended September 30, 2017 Real estate: Non-residential real estate owner occupied $ 5,685 $ (2 ) $ 1 $ (1 ) $ 261 $ 5,945 Non-residential real estate other 10,480 — 1 1 70 10,551 Residential real estate permanent mortgage 3,148 (90 ) 9 (81 ) 91 3,158 Residential real estate all other 8,912 (89 ) 13 (76 ) 503 9,339 Commercial and financial: Non-consumer non-real estate 13,643 (538 ) 24 (514 ) 1,838 14,967 Consumer non-real estate 2,706 (238 ) 57 (181 ) 207 2,732 Other loans 3,006 (47 ) — (47 ) 153 3,112 Acquired loans 1,425 (134 ) 7 (127 ) 153 1,451 Total $ 49,005 $ (1,138 ) $ 112 $ (1,026 ) $ 3,276 $ 51,255 Nine Months Ended September 30, 2017 Real estate: Non-residential real estate owner occupied $ 5,602 $ (74 ) $ 5 $ (69 ) $ 412 $ 5,945 Non-residential real estate other 10,793 (26 ) 3 (23 ) (219 ) 10,551 Residential real estate permanent mortgage 3,129 (246 ) 20 (226 ) 255 3,158 Residential real estate all other 8,622 (162 ) 30 (132 ) 849 9,339 Commercial and financial: Non-consumer non-real estate 12,421 (1,215 ) 986 (229 ) 2,775 14,967 Consumer non-real estate 2,804 (706 ) 140 (566 ) 494 2,732 Other loans 4,045 (1,321 ) 22 (1,299 ) 366 3,112 Acquired loans 1,277 (148 ) 65 (83 ) 257 1,451 Total $ 48,693 $ (3,898 ) $ 1,271 $ (2,627 ) $ 5,189 $ 51,255
Allowance for Loan Losses Outstanding by Impairment Methodology	The following table details the amount of ALL by class of loans for the period presented, detailed on the basis of the impairment methodology used by the Company. ALL September 30, 2018 December 31, 2017 Individually evaluated for impairment Collectively evaluated for impairment Individually evaluated for impairment Collectively evaluated for impairment (Dollars in thousands) Real estate: Non-residential real estate owner occupied. $ 891 $ 5,535 $ 656 $ 5,539 Non-residential real estate other 978 9,670 751 9,768 Residential real estate permanent mortgage 570 2,741 483 2,743 Residential real estate all other 3,263 7,158 2,761 6,911 Commercial and financial: Non-consumer non-real estate 3,486 10,910 4,651 10,683 Consumer non-real estate 346 2,567 429 2,364 Other loans 44 2,378 133 2,348 Acquired loans — 1,338 12 1,434 Total $ 9,578 $ 42,297 $ 9,876 $ 41,790
Loans Outstanding by Impairment Methodology	The following table details the loans outstanding by class of loans for the period presented, on the basis of the impairment methodology used by the Company. Loans September 30, 2018 December 31, 2017 Individually evaluated for impairment Collectively evaluated for impairment Loans acquired with deteriorated credit quality Individually evaluated for impairment Collectively evaluated for impairment Loans acquired with deteriorated credit quality (Dollars in thousands) Real estate: Non-residential real estate owner occupied $ 20,813 $ 609,609 $ — $ 15,281 $ 626,337 $ — Non-residential real estate other 22,363 1,095,087 — 17,013 1,109,578 — Residential real estate permanent mortgage 9,779 318,647 — 8,100 322,234 — Residential real estate all other 20,620 797,264 — 15,052 770,603 — Commercial and financial: Non-consumer non-real estate 20,664 1,249,416 — 31,349 1,253,056 — Consumer non-real estate 2,958 317,474 — 2,600 286,320 — Other loans 130 143,075 — 764 143,681 — Acquired loans 23,916 288,131 7,582 14,464 100,106 5,457 Total $ 121,243 $ 4,818,703 $ 7,582 $ 104,623 $ 4,611,915 $ 5,457
Transfers from Loans to Other Real Estate Owned and Repossessed Assets	Transfers from loans to other real estate owned and repossessed assets during the periods presented, are summarized as follows: Nine Months Ended September 30, 2018 2017 (Dollars in thousands) Other real estate owned $ 2,944 $ 1,906 Repossessed assets 842 887 Total $ 3,786 $ 2,793

Intangible Assets (Tables)

Intangible Assets (Tables)	9 Months Ended
	Sep. 30, 2018
Goodwill And Intangible Assets Disclosure [Abstract]
Summary of Intangible Assets	The following is a summary of intangible assets: Gross Carrying Amount Accumulated Amortization Net Carrying Amount (Dollars in thousands) As of September 30, 2018 Core deposit intangibles $ 25,907 $ (10,423 ) $ 15,484 Customer relationship intangibles 5,699 (4,028 ) 1,671 Mortgage servicing intangibles 403 (301 ) 102 Total $ 32,009 $ (14,752 ) $ 17,257 As of December 31, 2017 Core deposit intangibles $ 17,447 $ (8,451 ) $ 8,996 Customer relationship intangibles 5,699 (3,767 ) 1,932 Mortgage servicing intangibles 439 (285 ) 154 Total $ 23,585 $ (12,503 ) $ 11,082
Summary of Goodwill by Business Segment	The following is a summary of goodwill by business segment: Other Executive, Metropolitan Community Financial Operations Banks Banks Services & Support Consolidated (Dollars in thousands) Nine month ended September 30, 2018 Balance at beginning of period $ 8,078 $ 39,876 $ 5,464 $ 624 $ 54,042 Acquisitions 5,689 20,002 — — 25,691 Balance at end of period $ 13,767 $ 59,878 $ 5,464 $ 624 $ 79,733

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Activity Under Stock Option Plan	The following table is a summary of the activity under both the BancFirst ISOP and the BancFirst Directors’ Stock Option Plan: Wgtd. Avg. Wgtd. Avg. Remaining Aggregate Exercise Contractual Intrinsic Options Price Term Value (Dollars in thousands, except option data) Nine Months Ended September 30, 2018 Outstanding at December 31, 2017 1,273,625 $ 25.90 Options granted 57,000 57.71 Options exercised (118,425 ) 17.37 Options canceled, forfeited, or expired (5,000 ) 48.02 Outstanding at September 30, 2018 1,207,200 28.14 9.70 Yrs $ 38,399 Exercisable at September 30, 2018 530,200 21.15 7.05 Yrs $ 20,574
Options Granted and Options Exercised Under Stock Option Plan	The following table has additional information regarding options granted and options exercised under both the BancFirst ISOP and the BancFirst Directors’ Stock Option Plan: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (Dollars in thousands except per share data) Weighted average grant-date fair value per share of options granted $ 16.49 $ 11.63 $ 14.93 $ 11.21 Total intrinsic value of options exercised 766 1,493 4,593 7,138 Cash received from options exercised 413 856 2,057 4,113 Tax benefit realized from options exercised 195 578 1,170 2,761
Stock-based Employee Compensation Expense	The following table is a summary of the Company’s recorded stock-based compensation expense: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (Dollars in thousands) Stock-based compensation expense $ 353 $ 354 $ 981 $ 819 Tax benefit 90 137 250 317 Stock-based compensation expense, net of tax $ 263 $ 217 $ 731 $ 502
Unearned Stock-based Compensation Expense	The Company will continue to amortize the unearned stock-based compensation expense over the remaining vesting period of approximately seven years. The following table shows the unearned stock-based compensation expense: September 30, 2018 (Dollars in thousands) Unearned stock-based compensation expense $ 3,350
Assumptions Used for Computing Stock-Based Compensation Expense	The following table shows the assumptions used for computing stock-based compensation expense under the fair value method on options granted during the periods presented: Nine Months Ended September 30, 2018 2017 Risk-free interest rate 2.55 to 3.05% 2.15 to 2.38% Dividend yield 2.00% 2.00% Stock price volatility 23.05 to 23.46% 22.57 to 23.53% Expected term 10 Yrs 10 Yrs
Summary of Accumulated Stock Units	A summary of the accumulated stock units is as follows: September 30, December 31, 2018 2017 Accumulated stock units 140,946 138,768 Average price $ 24.36 $ 22.84

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2018
Equity [Abstract]
Summary of Shares Repurchased Under Stock Purchase Program	The following table is a summary of the shares under the program: Nine Months Ended September 30, 2018 2017 Number of shares repurchased — — Average price of shares repurchased $ — $ — Shares remaining to be repurchased 300,000 300,000
Required Capital Amounts and Company's Respective Ratios	The actual and required capital amounts and ratios are shown in the following table: Required To Be Well For Capital With Capitalized Under Adequacy Capital Conservation Prompt Corrective Actual Purposes Buffer Action Provisions Amount Ratio Amount Ratio Amount Ratio Amount Ratio (Dollars in thousands) As of September 30, 2018: Total Capital (to Risk Weighted Assets)- BancFirst Corporation $ 875,460 16.39% $ 427,430 8.00% $ 527,609 9.875% N/A N/A BancFirst 745,152 13.96% 426,871 8.00% 526,919 9.875% $ 533,589 10.00% Common Equity Tier 1 Capital (to Risk Weighted Assets)- BancFirst Corporation $ 792,585 14.83% $ 240,430 4.50% $ 340,609 6.375% N/A N/A BancFirst 673,277 12.62% 240,115 4.50% 340,163 6.375% $ 346,833 6.50% Tier 1 Capital (to Risk Weighted Assets)- BancFirst Corporation $ 823,585 15.41% $ 320,573 6.00% $ 420,752 7.875% N/A N/A BancFirst 693,277 12.99% 320,153 6.00% 420,202 7.875% $ 426,871 8.00% Tier 1 Capital (to Total Assets)- BancFirst Corporation $ 823,585 10.93% $ 301,392 4.00% N/A N/A N/A N/A BancFirst 693,277 9.21% 301,193 4.00% N/A N/A $ 376,491 5.00%

Net Income Per Common Share (Ta

Net Income Per Common Share (Tables)	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Basic and Diluted Net Income Per Common Share Based on Weighted-average Shares Outstanding	Basic and diluted net income per common share based on weighted-average shares outstanding are calculated as follows: Income (Numerator) Shares (Denominator) Per Share Amount (Dollars in thousands, except per share data) Three Months Ended September 30, 2018 Basic Income available to common stockholders $ 32,883 32,742,480 $ 1.01 Dilutive effect of stock options — 761,663 Diluted Income available to common stockholders plus assumed exercises of stock options $ 32,883 33,504,143 $ 0.98 Three Months Ended September 30, 2017 Basic Income available to common stockholders $ 21,710 31,838,392 $ 0.68 Dilutive effect of stock options — 753,885 Diluted Income available to common stockholders plus assumed exercises of stock options $ 21,710 32,592,277 $ 0.67 Nine Months Ended September 30, 2018 Basic Income available to common stockholders $ 93,089 32,678,310 $ 2.85 Dilutive effect of stock options — 752,451 Diluted Income available to common stockholders plus assumed exercises of stock options $ 93,089 33,430,761 $ 2.78 Nine Months Ended September 30, 2017 Basic Income available to common stockholders $ 66,942 31,792,270 $ 2.11 Dilutive effect of stock options — 741,949 Diluted Income available to common stockholders plus assumed exercises of stock options $ 66,942 32,534,219 $ 2.06
Options Excluded From Computation of Diluted Net Income Per Common Share	The following table shows the number of options that were excluded from the computation of diluted net income per common share for each period because the options’ exercise prices were greater than the average market price of the common shares: Shares Three Months Ended September 30, 2018 83,799 Three Months Ended September 30, 2017 75,543 Nine Months Ended September 30, 2018 84,368 Nine Months Ended September 30, 2017 39,120

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value of Financial Assets and Liabilities Measured on Recurring Basis	The following table summarizes financial assets and financial liabilities measured at fair value on a recurring basis as of the periods presented, segregated by the level of the valuation inputs within the fair value hierarchy utilized to measure fair value: Level 1 Inputs Level 2 Inputs Level 3 Inputs Total Fair Value (Dollars in thousands) September 30, 2018 Securities available for sale: U.S. Treasury $ 397,466 $ — $ — $ 397,466 U.S. federal agencies — 31,840 — 31,840 Mortgage-backed securities — 2,691 13,443 16,134 States and political subdivisions — 30,200 — 30,200 Equity securities — — 6,509 6,509 Derivative assets — 247 — 247 Derivative liabilities — 229 — 229 Loans held for sale — 4,739 — 4,739 December 31, 2017 Securities available for sale: U.S. Treasury $ 312,802 $ — $ — $ 312,802 U.S. federal agencies — 88,851 — 88,851 Mortgage-backed securities — 3,509 14,467 17,976 States and political subdivisions — 42,370 — 42,370 Equity securities — — 5,704 5,704 Derivative assets — 295 — 295 Derivative liabilities — 261 — 261 Loans held for sale — 6,173 — 6,173
Changes in Level 3 Assets Measured at Estimated Fair Value on Recurring Basis	The changes in Level 3 assets measured at estimated fair value on a recurring basis during the periods presented were as follows: Nine Months Ended September 30, Twelve Months Ended December 31, 2018 2017 (Dollars in thousands) Balance at the beginning of the year $ 20,171 $ 21,385 Purchases 2,118 1,668 Settlements (2,385 ) (722 ) Sales (73 ) (5,412 ) Gains included in earnings 67 4,060 Total unrealized losses 54 (808 ) Balance at the end of the period $ 19,952 $ 20,171
Assets Measured at Fair Value on Nonrecurring Basis	The following table summarizes assets measured at fair value on a nonrecurring basis. The fair value represents end of period values, which approximate fair value measurements that occurred on various measurement dates throughout the period: Total Fair Value Level 3 (Dollars in thousands) As of and for the Year-to-date Period Ended September 30, 2018 Impaired loans (less specific allowance) $ 39,620 Repossessed assets 244 Other real estate owned 4,610 As of and for the Year-to-date Period Ended December 31, 2017 Impaired loans (less specific allowance) $ 34,041 Repossessed assets 288 Other real estate owned 1,995
Estimated Fair Values of Financial Instruments	The estimated fair values of the Company’s financial instruments that are reported at amortized cost in the Company’s consolidated balance sheets, segregated by the level of valuation inputs within the fair value hierarchy utilized to measure fair value, are as follows: September 30, December 31, 2018 2017 Carrying Amount Fair Value Carrying Amount Fair Value (Dollars in thousands) FINANCIAL ASSETS Level 2 inputs: Cash and cash equivalents $ 1,792,766 $ 1,792,766 $ 1,758,575 $ 1,758,575 Securities held for investment 940 947 1,792 1,803 Level 3 inputs: Securities held for investment 500 500 500 500 Loans, net of allowance for loan losses 4,895,653 4,854,167 4,670,329 4,663,608 FINANCIAL LIABILITIES Level 2 inputs: Deposits 6,643,131 6,760,191 6,415,045 6,490,309 Short-term borrowings 2,200 2,200 900 900 Junior subordinated debentures 31,959 34,795 31,959 34,661 OFF-BALANCE SHEET FINANCIAL INSTRUMENTS Loan commitments 2,006 1,839 Letters of credit 425 428

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Results of Operations and Selected Financial Information	The results of operations and selected financial information for the four business units are as follows: Metropolitan Banks Community Banks Other Financial Services Executive, Operations & Support Eliminations Consolidated (Dollars in thousands) Three Months Ended September 30, 2018 Net interest income (expense) $ 21,313 $ 42,773 $ 1,241 $ 346 $ — $ 65,673 Noninterest income 4,266 15,404 10,264 36,503 (33,636 ) 32,801 Income before taxes 16,538 27,515 4,440 26,344 (32,919 ) 41,918 Three Months Ended September 30, 2017 Net interest income (expense) $ 18,617 $ 37,310 $ 1,332 $ (26 ) $ — $ 57,233 Noninterest income 3,981 13,884 9,217 24,470 (22,383 ) 29,169 Income before taxes 11,499 23,810 3,762 15,137 (21,682 ) 32,526 Nine Months Ended September 30, 2018 Net interest income (expense) $ 62,701 $ 126,223 $ 4,074 $ 590 $ — $ 193,588 Noninterest income 12,391 44,189 28,784 102,306 (94,322 ) 93,348 Income before taxes 46,157 81,805 13,511 69,881 (92,659 ) 118,695 Nine Months Ended September 30, 2017 Net interest income (expense) $ 54,969 $ 109,480 $ 4,525 $ (534 ) $ — $ 168,440 Noninterest income 11,748 40,821 24,983 74,586 (66,901 ) 85,237 Income before taxes 36,357 71,038 10,526 47,368 (65,942 ) 99,347 Total Assets: September 30, 2018 $ 2,724,502 $ 4,841,853 $ 80,411 $ 945,221 $ (989,549 ) $ 7,602,438 December 31, 2017 2,552,024 4,544,196 117,332 885,590 (845,986 ) 7,253,156

Description of Business and S_3

Description of Business and Summary of Significant Accounting Policies - Additional Information (Detail) - Accounting Standards Update 2016-01 [Member]	9 Months Ended
	Sep. 30, 2018USD ($)
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Additional income from changes in equity investments	$ 41,200
Retained Earnings [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Effect of change in accounting principle	(618,000)
Accumulated Other Comprehensive Income [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Effect of change in accounting principle	$ 618,000

Recent Developments Including M

Recent Developments Including Mergers and Acquisitions - Additional Information (Detail) $ in Thousands	Aug. 31, 2018USD ($)ft²Floor	Jan. 11, 2018USD ($)Location	Jul. 31, 2017shares	Sep. 30, 2018USD ($)Community	Dec. 31, 2017USD ($)
Business Combination Separately Recognized Transactions [Line Items]
Goodwill				$ 79,733	$ 54,042
Number of additional banking communities | Community				5
Common Stock [Member]
Business Combination Separately Recognized Transactions [Line Items]
Stock split description				On July 31, 2017, the Company completed a two-for-one stock split of the Company’s outstanding shares of common stock.
Stock split conversion ratio			2
Stock payable in form of dividend, payable date			Jul. 31, 2017
Stock payable in form of dividend, record date			Jul. 17, 2017
Additional shares received by stockholders for each share held | shares			1
First Bank & Trust Company [Member]
Business Combination Separately Recognized Transactions [Line Items]
Date of acquisition		Jan. 11, 2018
Total assets acquired		$ 290,000
Loans		247,000
Deposits		251,000
Equity capital		36,000
Intangibles assets, net		6,300
Goodwill		$ 19,100
Fair value estimates period		1 year
First Bank of Chandler [Member]
Business Combination Separately Recognized Transactions [Line Items]
Date of acquisition		Jan. 11, 2018
Total assets acquired		$ 88,000
Loans		66,000
Deposits		79,000
Equity capital		11,000
Intangibles assets, net		2,200
Goodwill		$ 6,600
Fair value estimates period		1 year
Number of locations acquired | Location		2
BFTower LLC [Member] | Cotter Ranch Tower [Member]
Business Combination Separately Recognized Transactions [Line Items]
Contract price	$ 21,000
Number of square feet | ft²	507,000
Number of floors | Floor	36
Date of acquisition	Aug. 31, 2018

Securities - Summary of Securit

Securities - Summary of Securities Held for Investment and Securities Available for Sale (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Marketable Securities [Abstract]
Held for investment, at cost (fair value: $1,447 and $2,303, respectively)	$ 1,440	$ 2,292
Available for sale, at fair value	475,640	467,703
Total	$ 477,080	$ 469,995

Securities - Summary of Secur_2

Securities - Summary of Securities Held for Investment and Securities Available for Sale (Parenthetical) (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Marketable Securities [Abstract]
Held for investment at fair value	$ 1,447	$ 2,303

Securities - Summary of Amortiz

Securities - Summary of Amortized Cost and Estimated Fair Values of Securities Held for Investment (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 1,440	$ 2,292
Gross Unrealized Gains	7	13
Gross Unrealized Losses		(2)
Estimated Fair Value	1,447	2,303
Mortgage Backed Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	145	187
Gross Unrealized Gains	6	10
Estimated Fair Value	151	197
States and Political Subdivisions [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	795	1,605
Gross Unrealized Gains	1	3
Gross Unrealized Losses		(2)
Estimated Fair Value	796	1,606
Other Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	500	500
Estimated Fair Value	$ 500	$ 500

Securities - Summary of Amort_2

Securities - Summary of Amortized Cost and Estimated Fair Values of Securities Available for Sale (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 481,909	$ 470,825
Gross Unrealized Gains	382	911
Gross Unrealized Losses	(6,651)	(4,033)
Estimated Fair Value	475,640	467,703
U.S. Treasuries [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	403,213	314,905
Gross Unrealized Losses	(5,747)	(2,103)
Estimated Fair Value	397,466	312,802
U.S. Federal Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	32,017	89,098
Gross Unrealized Gains	1	82
Gross Unrealized Losses	(178)	(329)
Estimated Fair Value	31,840	88,851
Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	16,581	18,358
Gross Unrealized Gains	119	204
Gross Unrealized Losses	(566)	(586)
Estimated Fair Value	16,134	17,976
States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	30,098	41,937
Gross Unrealized Gains	262	554
Gross Unrealized Losses	(160)	(121)
Estimated Fair Value	$ 30,200	42,370
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		6,527
Gross Unrealized Gains		71
Gross Unrealized Losses		(894)
Estimated Fair Value		$ 5,704

Securities - Maturity of Securi

Securities - Maturity of Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Held for Investment, Contractual maturity of debt securities, Amortized Cost
Amortized cost, Within one year	$ 495	$ 1,036
Amortized cost, After one year but within five years	370	623
Amortized cost, After five years but within ten years	570	625
Amortized cost, After ten years	5	8
Amortized Cost	1,440	2,292
Available for sale, Contractual maturity of debt securities, Amortized Cost
Amortized Cost, Within one year	61,869	113,225
Amortized Cost, After one year but within five years	368,309	289,038
Amortized Cost, After five years but within ten years	5,047	6,222
Amortized Cost, After ten years	46,684	55,813
Total debt securities	481,909	464,298
Amortized Cost, Equity securities		6,527
Amortized Cost	481,909	470,825
Held for Investment, Contractual maturity of debt securities, Estimated Fair Value
Estimated Fair Value, Within one year	496	1,034
Estimated Fair Value, After one year but within five years	371	627
Estimated Fair Value, After five years but within ten years	575	633
Estimated Fair Value, After ten years	5	9
Estimated Fair Value	1,447	2,303
Available for sale, Contractual maturity of debt securities, Estimated Fair Value
Estimated Fair Value, Within one year	61,656	112,974
Estimated Fair Value, After one year but within five years	362,723	287,058
Estimated Fair Value, After five years but within ten years	5,225	6,500
Estimated Fair Value, After ten years	46,036	55,467
Total debt securities	475,640	461,999
Estimated Fair Value, Equity securities		5,704
Estimated Fair Value, Total	$ 475,640	$ 467,703

Securities - Company's Book Val

Securities - Company's Book Value of Pledged Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Pledged Financial Instruments Not Separately Reported Securities Pledged By Type Of Security [Abstract]
Book value of pledged securities	$ 428,057	$ 440,069

Loans and Allowance for Loan _3

Loans and Allowance for Loan Losses - Schedule of Loans Outstanding by Category (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Financing Receivable Recorded Investment [Line Items]
Total loans	$ 4,947,528	$ 4,721,995
Percent	100.00%	100.00%
Taxable [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	$ 79,832	$ 73,827
Percent	1.61%	1.56%
Tax-exempt [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	$ 41,368	$ 48,626
Percent	0.84%	1.03%
Commercial and Financial [Member] | Commercial and Industrial [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	$ 1,042,237	$ 995,207
Percent	21.07%	21.08%
Commercial and Financial [Member] | Oil & Gas Production And Equipment [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	$ 98,324	$ 95,574
Percent	1.99%	2.02%
Commercial and Financial [Member] | Agriculture [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	$ 127,904	$ 141,249
Percent	2.59%	2.99%
Real Estate [Member] | Construction [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	$ 446,046	$ 437,277
Percent	9.02%	9.26%
Real Estate [Member] | Farmland [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	$ 217,191	$ 195,162
Percent	4.38%	4.13%
Real Estate [Member] | One to Four Family Residences [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	$ 972,922	$ 875,766
Percent	19.66%	18.55%
Real Estate [Member] | Multifamily Residential Properties [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	$ 62,555	$ 46,030
Percent	1.26%	0.98%
Real Estate [Member] | Commercial [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	$ 1,497,894	$ 1,487,927
Percent	30.28%	31.51%
Consumer [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	$ 323,952	$ 284,373
Percent	6.55%	6.02%
Other (Not Classified Above) [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	$ 37,303	$ 40,977
Percent	0.75%	0.87%

Loans and Allowance for Loan _4

Loans and Allowance for Loan Losses - Additional Information (Detail) - USD ($)	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Financing Receivable Recorded Investment [Line Items]
Total loans	$ 4,947,528,000		$ 4,721,995,000
Percentage of loans secured by real estate	60.00%
Interest income that would have been recognized	$ 1,700,000	$ 1,300,000
Interest income recognized on impaired loans	0	$ 2,300,000
Commercial and Industrial [Member] | Ancillary Services [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	$ 62,000,000		$ 81,000,000

Loans and Allowance for Loan _5

Loans and Allowance for Loan Losses - Summary of Nonperforming and Restructured Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Summary Of Nonperforming And Restructured Assets [Abstract]
Past due 90 days or more and still accruing	$ 4,073	$ 2,893
Nonaccrual	26,880	31,943
Restructured	13,557	4,720
Total nonperforming and restructured loans	44,510	39,556
Other real estate owned and repossessed assets	7,072	4,424
Total nonperforming and restructured assets	$ 51,582	$ 43,980

Loans and Allowance for Loan _6

Loans and Allowance for Loan Losses - Summary of Amounts Included in Nonaccrual Loans Segregated by Class of Loans (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual Loans, Total	$ 26,880	$ 31,943
Real Estate [Member] | Non-residential Real Estate Owner Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual Loans, Total	1,526	1,108
Real Estate [Member] | Non-residential Real Estate Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual Loans, Total	7,125	9,809
Real Estate [Member] | Residential Real Estate Permanent Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual Loans, Total	1,043	781
Real Estate [Member] | Residential Real Estate All Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual Loans, Total	4,911	3,980
Commercial and Financial [Member] | Non-consumer Non-real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual Loans, Total	6,032	7,785
Consumer Non-real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual Loans, Total	416	250
Other Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual Loans, Total	427	5,596
Acquired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual Loans, Total	$ 5,400	$ 2,634

Loans and Allowance for Loan _7

Loans and Allowance for Loan Losses - Age Analysis of Past Due Loans Segregated by Class of Loans (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	$ 40,980	$ 28,719
Current Loans	4,906,548	4,693,276
Total Loans	4,947,528	4,721,995
Accruing Loans 90 Days or More Past Due	4,073	2,893
Real Estate [Member] | Non-residential Real Estate Owner Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	2,894	2,043
Current Loans	627,528	639,575
Total Loans	630,422	641,618
Accruing Loans 90 Days or More Past Due	90	84
Real Estate [Member] | Non-residential Real Estate Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	5,521	5,288
Current Loans	1,111,929	1,121,303
Total Loans	1,117,450	1,126,591
Accruing Loans 90 Days or More Past Due	57	432
Real Estate [Member] | Residential Real Estate Permanent Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	6,189	3,591
Current Loans	322,237	326,743
Total Loans	328,426	330,334
Accruing Loans 90 Days or More Past Due	427	584
Real Estate [Member] | Residential Real Estate All Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	7,157	3,865
Current Loans	810,727	781,790
Total Loans	817,884	785,655
Accruing Loans 90 Days or More Past Due	845	973
Commercial and Financial [Member] | Non-consumer Non-real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	6,264	4,701
Current Loans	1,263,816	1,279,704
Total Loans	1,270,080	1,284,405
Accruing Loans 90 Days or More Past Due	1,070	403
Consumer Non-real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	2,803	3,048
Current Loans	317,629	285,872
Total Loans	320,432	288,920
Accruing Loans 90 Days or More Past Due	345	194
Other Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	886	4,525
Current Loans	142,319	139,920
Total Loans	143,205	144,445
Accruing Loans 90 Days or More Past Due	128
Acquired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	9,266	1,658
Current Loans	310,363	118,369
Total Loans	319,629	120,027
Accruing Loans 90 Days or More Past Due	1,111	223
30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	19,620	13,407
30 to 59 Days Past Due [Member] | Real Estate [Member] | Non-residential Real Estate Owner Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	977	998
30 to 59 Days Past Due [Member] | Real Estate [Member] | Non-residential Real Estate Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	4,964	2,905
30 to 59 Days Past Due [Member] | Real Estate [Member] | Residential Real Estate Permanent Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	3,910	2,211
30 to 59 Days Past Due [Member] | Real Estate [Member] | Residential Real Estate All Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	2,034	1,739
30 to 59 Days Past Due [Member] | Commercial and Financial [Member] | Non-consumer Non-real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	2,573	2,210
30 to 59 Days Past Due [Member] | Consumer Non-real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	1,721	2,085
30 to 59 Days Past Due [Member] | Other Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	514	506
30 to 59 Days Past Due [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	2,927	753
60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	9,773	3,162
60 to 89 Days Past Due [Member] | Real Estate [Member] | Non-residential Real Estate Owner Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	1,106	68
60 to 89 Days Past Due [Member] | Real Estate [Member] | Non-residential Real Estate Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	385	271
60 to 89 Days Past Due [Member] | Real Estate [Member] | Residential Real Estate Permanent Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	1,318	403
60 to 89 Days Past Due [Member] | Real Estate [Member] | Residential Real Estate All Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	2,790	749
60 to 89 Days Past Due [Member] | Commercial and Financial [Member] | Non-consumer Non-real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	1,469	706
60 to 89 Days Past Due [Member] | Consumer Non-real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	530	670
60 to 89 Days Past Due [Member] | Other Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans		103
60 to 89 Days Past Due [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	2,175	192
90 Days and Greater [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	11,587	12,150
90 Days and Greater [Member] | Real Estate [Member] | Non-residential Real Estate Owner Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	811	977
90 Days and Greater [Member] | Real Estate [Member] | Non-residential Real Estate Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	172	2,112
90 Days and Greater [Member] | Real Estate [Member] | Residential Real Estate Permanent Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	961	977
90 Days and Greater [Member] | Real Estate [Member] | Residential Real Estate All Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	2,333	1,377
90 Days and Greater [Member] | Commercial and Financial [Member] | Non-consumer Non-real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	2,222	1,785
90 Days and Greater [Member] | Consumer Non-real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	552	293
90 Days and Greater [Member] | Other Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	372	3,916
90 Days and Greater [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	$ 4,164	$ 713

Loans and Allowance for Loan _8

Loans and Allowance for Loan Losses - Impaired Loans Segregated by Class of Loans (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Principal Balance	$ 56,964	$ 49,391
Recorded Investment with Allowance	45,150	39,688
Related Allowance	5,530	5,647
Average Recorded Investment	47,054	35,181
Real Estate [Member] | Non-residential Real Estate Owner Occupied [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Principal Balance	8,187	2,011
Recorded Investment with Allowance	8,063	1,945
Related Allowance	353	141
Average Recorded Investment	7,877	1,858
Real Estate [Member] | Non-residential Real Estate Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Principal Balance	8,262	10,323
Recorded Investment with Allowance	7,753	10,240
Related Allowance	333	496
Average Recorded Investment	8,678	3,975
Real Estate [Member] | Residential Real Estate Permanent Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Principal Balance	1,842	1,745
Recorded Investment with Allowance	1,634	1,542
Related Allowance	145	146
Average Recorded Investment	1,746	1,440
Real Estate [Member] | Residential Real Estate All Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Principal Balance	6,762	5,837
Recorded Investment with Allowance	6,507	5,549
Related Allowance	2,310	2,135
Average Recorded Investment	6,678	5,258
Commercial and Financial [Member] | Non-consumer Non-real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Principal Balance	19,458	18,101
Recorded Investment with Allowance	12,065	11,158
Related Allowance	2,234	2,412
Average Recorded Investment	13,359	11,131
Consumer Non-real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Principal Balance	897	545
Recorded Investment with Allowance	825	514
Related Allowance	108	127
Average Recorded Investment	818	541
Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Principal Balance	772	6,092
Recorded Investment with Allowance	558	5,595
Related Allowance	43	178
Average Recorded Investment	456	7,439
Acquired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Principal Balance	10,784	4,737
Recorded Investment with Allowance	7,745	3,145
Related Allowance	4	12
Average Recorded Investment	$ 7,442	$ 3,539

Loans and Allowance for Loan _9

Loans and Allowance for Loan Losses - Internal Loan Grading by Class of Loans (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Financing Receivable Recorded Investment [Line Items]
Total loans	$ 4,947,528	$ 4,721,995
Real Estate [Member] | Non-residential Real Estate Owner Occupied [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	630,422	641,618
Real Estate [Member] | Non-residential Real Estate Other [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	1,117,450	1,126,591
Real Estate [Member] | Residential Real Estate Permanent Mortgage [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	328,426	330,334
Real Estate [Member] | Residential Real Estate All Other [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	817,884	785,655
Commercial and Financial [Member] | Non-consumer Non-real Estate [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	1,270,080	1,284,405
Consumer Non-real Estate [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	320,432	288,920
Other Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	143,205	144,445
Acquired Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	319,629	120,027
Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	3,916,921	3,851,837
Grade 1 [Member] | Real Estate [Member] | Non-residential Real Estate Owner Occupied [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	478,014	520,641
Grade 1 [Member] | Real Estate [Member] | Non-residential Real Estate Other [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	913,259	931,295
Grade 1 [Member] | Real Estate [Member] | Residential Real Estate Permanent Mortgage [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	280,194	289,200
Grade 1 [Member] | Real Estate [Member] | Residential Real Estate All Other [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	641,246	621,401
Grade 1 [Member] | Commercial and Financial [Member] | Non-consumer Non-real Estate [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	980,535	1,018,172
Grade 1 [Member] | Consumer Non-real Estate [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	297,516	268,826
Grade 1 [Member] | Other Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	137,705	136,617
Grade 1 [Member] | Acquired Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	188,452	65,685
Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	901,743	758,681
Grade 2 [Member] | Real Estate [Member] | Non-residential Real Estate Owner Occupied [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	131,597	105,696
Grade 2 [Member] | Real Estate [Member] | Non-residential Real Estate Other [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	181,829	178,282
Grade 2 [Member] | Real Estate [Member] | Residential Real Estate Permanent Mortgage [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	38,452	33,033
Grade 2 [Member] | Real Estate [Member] | Residential Real Estate All Other [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	156,018	149,201
Grade 2 [Member] | Commercial and Financial [Member] | Non-consumer Non-real Estate [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	268,882	234,884
Grade 2 [Member] | Consumer Non-real Estate [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	19,975	17,499
Grade 2 [Member] | Other Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	5,304	5,668
Grade 2 [Member] | Acquired Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	99,686	34,418
Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	99,908	88,588
Grade 3 [Member] | Real Estate [Member] | Non-residential Real Estate Owner Occupied [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	19,221	13,852
Grade 3 [Member] | Real Estate [Member] | Non-residential Real Estate Other [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	15,238	14,290
Grade 3 [Member] | Real Estate [Member] | Residential Real Estate Permanent Mortgage [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	8,093	6,352
Grade 3 [Member] | Real Estate [Member] | Residential Real Estate All Other [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	15,000	9,418
Grade 3 [Member] | Commercial and Financial [Member] | Non-consumer Non-real Estate [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	14,915	24,322
Grade 3 [Member] | Consumer Non-real Estate [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	2,202	2,038
Grade 3 [Member] | Other Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	157	1,203
Grade 3 [Member] | Acquired Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	25,082	17,113
Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	28,707	22,859
Grade 4 [Member] | Real Estate [Member] | Non-residential Real Estate Owner Occupied [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	1,590	1,429
Grade 4 [Member] | Real Estate [Member] | Non-residential Real Estate Other [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	7,124	2,724
Grade 4 [Member] | Real Estate [Member] | Residential Real Estate Permanent Mortgage [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	1,687	1,749
Grade 4 [Member] | Real Estate [Member] | Residential Real Estate All Other [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	5,620	5,635
Grade 4 [Member] | Commercial and Financial [Member] | Non-consumer Non-real Estate [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	5,748	6,997
Grade 4 [Member] | Consumer Non-real Estate [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	739	557
Grade 4 [Member] | Other Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	39	957
Grade 4 [Member] | Acquired Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	6,160	2,811
Grade 5 [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	249	30
Grade 5 [Member] | Commercial and Financial [Member] | Non-consumer Non-real Estate [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans		$ 30
Grade 5 [Member] | Acquired Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans	$ 249

Loans and Allowance for Loan_10

Loans and Allowance for Loan Losses - Activity in ALL by Class of Loans (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	$ 52,200	$ 49,005	$ 51,666	$ 48,693
Charge- offs	(1,271)	(1,138)	(2,542)	(3,898)
Recoveries	199	112	465	1,271
Net charge- offs	(1,072)	(1,026)	(2,077)	(2,627)
Provisions charged to operations	747	3,276	2,286	5,189
Balance at end of period	51,875	51,255	51,875	51,255
Real Estate [Member] | Non-residential Real Estate Owner Occupied [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	6,426	5,685	6,195	5,602
Charge- offs	(179)	(2)	(198)	(74)
Recoveries	15	1	16	5
Net charge- offs	(164)	(1)	(182)	(69)
Provisions charged to operations	164	261	413	412
Balance at end of period	6,426	5,945	6,426	5,945
Real Estate [Member] | Non-residential Real Estate Other [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	10,705	10,480	10,519	10,793
Charge- offs	(8)		(9)	(26)
Recoveries		1	39	3
Net charge- offs	(8)	1	30	(23)
Provisions charged to operations	(49)	70	99	(219)
Balance at end of period	10,648	10,551	10,648	10,551
Real Estate [Member] | Residential Real Estate Permanent Mortgage [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	3,307	3,148	3,226	3,129
Charge- offs	(39)	(90)	(101)	(246)
Recoveries		9	26	20
Net charge- offs	(39)	(81)	(75)	(226)
Provisions charged to operations	43	91	160	255
Balance at end of period	3,311	3,158	3,311	3,158
Real Estate [Member] | Residential Real Estate All Other [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	10,123	8,912	9,672	8,622
Charge- offs	(71)	(89)	(312)	(162)
Recoveries	95	13	101	30
Net charge- offs	24	(76)	(211)	(132)
Provisions charged to operations	274	503	960	849
Balance at end of period	10,421	9,339	10,421	9,339
Commercial and Financial [Member] | Non-consumer Non-real Estate [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	15,069	13,643	15,334	12,421
Charge- offs	(343)	(538)	(652)	(1,215)
Recoveries	7	24	30	986
Net charge- offs	(336)	(514)	(622)	(229)
Provisions charged to operations	(337)	1,838	(316)	2,775
Balance at end of period	14,396	14,967	14,396	14,967
Consumer Non-real Estate [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	2,839	2,706	2,793	2,804
Charge- offs	(294)	(238)	(738)	(706)
Recoveries	70	57	194	140
Net charge- offs	(224)	(181)	(544)	(566)
Provisions charged to operations	298	207	664	494
Balance at end of period	2,913	2,732	2,913	2,732
Other Loans [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	2,328	3,006	2,481	4,045
Charge- offs		(47)	(2)	(1,321)
Recoveries	6		30	22
Net charge- offs	6	(47)	28	(1,299)
Provisions charged to operations	88	153	(87)	366
Balance at end of period	2,422	3,112	2,422	3,112
Acquired Loans [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	1,403	1,425	1,446	1,277
Charge- offs	(337)	(134)	(530)	(148)
Recoveries	6	7	29	65
Net charge- offs	(331)	(127)	(501)	(83)
Provisions charged to operations	266	153	393	257
Balance at end of period	$ 1,338	$ 1,451	$ 1,338	$ 1,451

Loans and Allowance for Loan_11

Loans and Allowance for Loan Losses - Allowance for Loan Losses Outstanding by Impairment Methodology (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Individually evaluated for impairment	$ 9,578	$ 9,876
Collectively evaluated for impairment	42,297	41,790
Real Estate [Member] | Non-residential Real Estate Owner Occupied [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Individually evaluated for impairment	891	656
Collectively evaluated for impairment	5,535	5,539
Real Estate [Member] | Non-residential Real Estate Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Individually evaluated for impairment	978	751
Collectively evaluated for impairment	9,670	9,768
Real Estate [Member] | Residential Real Estate Permanent Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Individually evaluated for impairment	570	483
Collectively evaluated for impairment	2,741	2,743
Real Estate [Member] | Residential Real Estate All Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Individually evaluated for impairment	3,263	2,761
Collectively evaluated for impairment	7,158	6,911
Commercial and Financial [Member] | Non-consumer Non-real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Individually evaluated for impairment	3,486	4,651
Collectively evaluated for impairment	10,910	10,683
Consumer Non-real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Individually evaluated for impairment	346	429
Collectively evaluated for impairment	2,567	2,364
Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Individually evaluated for impairment	44	133
Collectively evaluated for impairment	2,378	2,348
Acquired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Individually evaluated for impairment		12
Collectively evaluated for impairment	$ 1,338	$ 1,434

Loans and Allowance for Loan_12

Loans and Allowance for Loan Losses - Loans Outstanding by Impairment Methodology (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Individually evaluated for impairment	$ 121,243	$ 104,623
Collectively evaluated for impairment	4,818,703	4,611,915
Receivables Acquired with Deteriorated Credit Quality [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired with deteriorated credit quality	7,582	5,457
Real Estate [Member] | Non-residential Real Estate Owner Occupied [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Individually evaluated for impairment	20,813	15,281
Collectively evaluated for impairment	609,609	626,337
Real Estate [Member] | Non-residential Real Estate Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Individually evaluated for impairment	22,363	17,013
Collectively evaluated for impairment	1,095,087	1,109,578
Real Estate [Member] | Residential Real Estate Permanent Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Individually evaluated for impairment	9,779	8,100
Collectively evaluated for impairment	318,647	322,234
Real Estate [Member] | Residential Real Estate All Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Individually evaluated for impairment	20,620	15,052
Collectively evaluated for impairment	797,264	770,603
Commercial and Financial [Member] | Non-consumer Non-real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Individually evaluated for impairment	20,664	31,349
Collectively evaluated for impairment	1,249,416	1,253,056
Consumer Non-real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Individually evaluated for impairment	2,958	2,600
Collectively evaluated for impairment	317,474	286,320
Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Individually evaluated for impairment	130	764
Collectively evaluated for impairment	143,075	143,681
Acquired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Individually evaluated for impairment	23,916	14,464
Collectively evaluated for impairment	288,131	100,106
Acquired Loans [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired with deteriorated credit quality	$ 7,582	$ 5,457

Loans and Allowance for Loan_13

Loans and Allowance for Loan Losses - Transfers from Loans to Other Real Estate Owned and Repossessed Assets (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Financing Receivable Allowance For Credit Loss Additional Information Transfer From Loans To Other Real Estate Owned And Repossessed Assets [Abstract]
Other real estate owned	$ 2,944	$ 1,906
Repossessed assets	842	887
Total	$ 3,786	$ 2,793

Intangible Assets - Summary of

Intangible Assets - Summary of Intangible Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 32,009	$ 23,585
Accumulated Amortization	(14,752)	(12,503)
Net Carrying Amount	17,257	11,082
Core Deposit Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	25,907	17,447
Accumulated Amortization	(10,423)	(8,451)
Net Carrying Amount	15,484	8,996
Customer Relationship Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	5,699	5,699
Accumulated Amortization	(4,028)	(3,767)
Net Carrying Amount	1,671	1,932
Mortgage Servicing Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	403	439
Accumulated Amortization	(301)	(285)
Net Carrying Amount	$ 102	$ 154

Intangible Assets - Summary o_2

Intangible Assets - Summary of Goodwill by Business Segment (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2018USD ($)
Goodwill [Line Items]
Balance at beginning of period	$ 54,042
Acquisitions	25,691
Balance at end of period	79,733
Metropolitan Banks [Member]
Goodwill [Line Items]
Balance at beginning of period	8,078
Acquisitions	5,689
Balance at end of period	13,767
Community Banks [Member]
Goodwill [Line Items]
Balance at beginning of period	39,876
Acquisitions	20,002
Balance at end of period	59,878
Other Financial Services [Member]
Goodwill [Line Items]
Balance at beginning of period	5,464
Balance at end of period	5,464
Executive, Operations & Support [Member]
Goodwill [Line Items]
Balance at beginning of period	624
Balance at end of period	$ 624

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - shares	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Deferred board fees percentage for stock units accumulation	100.00%
Nonqualified Incentive Stock Option Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period in years	7 years
Nonqualified Incentive Stock Option Plan [Member] | Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares to be issued under incentive stock option plan	6,400,000
Shares for future grants	297,970
Stock option plan termination date	Dec. 31, 2019
Option exercisable rate	25.00%
Option exercisable period	4 years
Options expire period	15 years
Share based compensation options exercisable period	2,025
Vesting period in years, start	4 years
Options vest and exercisable Description	The options vest and are exercisable beginning four years from the date of grant at the rate of 25% per year for four years. Options expire at the end of fifteen years from the date of grant
Nonqualified Incentive Stock Option Plan [Member] | Stock Option [Member] | Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock price percentage to fair value at grant date	100.00%
Non-Employee Directors Stock Option Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares to be issued under incentive stock option plan	520,000
Shares for future grants	40,000
Option exercisable rate	25.00%
Option exercisable period	1 year
Options expire period	15 years
Share based compensation options exercisable period	2,022
Options vest and exercisable Description	The options vest and are exercisable beginning one year from the date of grant at the rate of 25% per year for four years
Number of options granted for non-employee director	10,000
Vesting period in years	4 years
Non-Employee Directors Stock Option Plan [Member] | Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock price percentage to fair value at grant date	100.00%
Banc First Deferred Stock Compensation Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized for issuance under deferred compensation plan	222,220
Number of shares of common stock distributed	3,891	9,918

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Activity Under Stock Option Plan (Detail) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2018USD ($)$ / sharesshares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Outstanding at beginning period - Options | shares	1,273,625
Options granted | shares	57,000
Options exercised | shares	(118,425)
Options canceled, forfeited, or expired | shares	(5,000)
Outstanding at ending period - Options | shares	1,207,200
Exercisable at ending period - Options | shares	530,200
Outstanding at beginning period - Wgtd. Avg. Exercise Price | $ / shares	$ 25.90
Options granted - Wgtd. Avg. Exercise Price | $ / shares	57.71
Options exercised - Wgtd. Avg. Exercise Price | $ / shares	17.37
Options canceled, forfeited, or expired - Wgtd. Avg. Exercise Price | $ / shares	48.02
Outstanding at ending period - Wgtd. Avg. Exercise Price | $ / shares	28.14
Exercisable at ending period - Wgtd. Avg. Exercise Price | $ / shares	$ 21.15
Outstanding at ending period - Wgtd. Avg. Remaining Contractual Term, years	9 years 8 months 12 days
Exercisable at ending period - Wgtd. Avg. Remaining Contractual Term, years	7 years 18 days
Outstanding at ending period - Aggregate Intrinsic Value | $	$ 38,399
Exercisable at ending period - Aggregate Intrinsic Value | $	$ 20,574

Stock-Based Compensation - Opti

Stock-Based Compensation - Options Granted and Options Exercised Under Stock Option Plan (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Share Based Compensation Arrangement By Share Based Payment Award Options Additional Disclosures [Abstract]
Weighted average grant-date fair value per share of options granted	$ 16.49	$ 11.63	$ 14.93	$ 11.21
Total intrinsic value of options exercised	$ 766	$ 1,493	$ 4,593	$ 7,138
Cash received from options exercised	413	856	2,057	4,113
Tax benefit realized from options exercised	$ 195	$ 578	$ 1,170	$ 2,761

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock-Based Employee Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Labor And Related Expense [Abstract]
Stock-based compensation expense	$ 353	$ 354	$ 981	$ 819
Tax benefit	90	137	250	317
Stock-based compensation expense, net of tax	$ 263	$ 217	$ 731	$ 502

Stock-Based Compensation - Unea

Stock-Based Compensation - Unearned Stock-based Compensation Expense (Detail) $ in Thousands	Sep. 30, 2018USD ($)
Share Based Compensation [Abstract]
Unearned stock-based compensation expense	$ 3,350

Stock-Based Compensation - Assu

Stock-Based Compensation - Assumptions Used for Computing Stock-Based Compensation Expense (Detail)	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions And Methodology [Abstract]
Risk-free interest rate, minimum	2.55%	2.15%
Risk-free interest rate, maximum	3.05%	2.38%
Dividend yield	2.00%	2.00%
Stock price volatility, minimum	23.05%	22.57%
Stock price volatility, maximum	23.46%	23.53%
Expected term	10 years	10 years

Stock - Based Compensation - Su

Stock - Based Compensation - Summary of Accumulated Stock Units (Detail) - $ / shares	Sep. 30, 2018	Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Accumulated stock units	140,946	138,768
Average price	$ 24.36	$ 22.84

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Shares Repurchased Under Stock Purchase Program (Detail) - shares	Sep. 30, 2018	Sep. 30, 2017
Summary Of Shares Repurchased Under Stock Purchase Program [Abstract]
Shares remaining to be repurchased	300,000	300,000

Stockholders' Equity - Required

Stockholders' Equity - Required Capital Amounts and Company's Respective Ratios (Detail) $ in Thousands	Sep. 30, 2018USD ($)
Parent Company [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital Amount	$ 875,460
Total Capital To Risk Weighted Assets Actual Ratio	16.39%
Capital Required For Capital Adequacy Amount	$ 427,430
Capital Required For Capital Adequacy to Risk Weighted Assets Ratio	8.00%
Capital With Capital Conservation Buffer Amount	$ 527,609
Capital With Capital Conservation To Risk Based Weighted Assets Buffer Ratio	9.875%
Common Equity Tier 1 Risk Based Capital Amount	$ 792,585
Common Equity Tier 1 Risk Based Capital To Risk Weighted Assets Ratio	14.83%
Common Equity Tier 1 Risk Based Capital Required For Capital Adequacy Amount	$ 240,430
Common Equity Tier 1 Risk Based Capital Required For Capital Adequacy To Risk Weighted Assets Ratio	4.50%
Common Equity Tier 1 Risk Based Capital With Capital Conservation Buffer Amount	$ 340,609
Common Equity Tier 1 Risk Based Capital With Capital Conservation Buffer To Risk Weighted Assets Ratio	6.375%
Tier 1 Risk Based Capital Amount	$ 823,585
Tier 1 Risk Based Capital To Risk Weighted Assets Ratio	15.41%
Tier 1 Risk Based Capital Required For Capital Adequacy Amount	$ 320,573
Tier 1 Risk Based Capital Required For Capital Adequacy To Risk Weighted Assets Ratio	6.00%
Tier 1 Risk Based Capital With Capital Conservation Buffer Amount	$ 420,752
Tier 1 Risk Based Capital With Capital Conservation Buffer To Risk Weighted Assets Ratio	7.875%
Tier 1 Capital Amount	$ 823,585
Tier 1 Capital To Average Assets Ratio	10.93%
Tier 1 Capital Required For Capital Adequacy Amount	$ 301,392
Tier 1 Capital Required For Capital Adequacy To Average Assets Ratio	4.00%
BancFirst [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital Amount	$ 745,152
Total Capital To Risk Weighted Assets Actual Ratio	13.96%
Capital Required For Capital Adequacy Amount	$ 426,871
Capital Required For Capital Adequacy to Risk Weighted Assets Ratio	8.00%
Capital With Capital Conservation Buffer Amount	$ 526,919
Capital With Capital Conservation To Risk Based Weighted Assets Buffer Ratio	9.875%
Capital Required To Be Well Capitalized Amount	$ 533,589
Capital Required To Be Well Capitalized To Risk Weighted Assets Ratio	10.00%
Common Equity Tier 1 Risk Based Capital Amount	$ 673,277
Common Equity Tier 1 Risk Based Capital To Risk Weighted Assets Ratio	12.62%
Common Equity Tier 1 Risk Based Capital Required For Capital Adequacy Amount	$ 240,115
Common Equity Tier 1 Risk Based Capital Required For Capital Adequacy To Risk Weighted Assets Ratio	4.50%
Common Equity Tier 1 Risk Based Capital With Capital Conservation Buffer Amount	$ 340,163
Common Equity Tier 1 Risk Based Capital With Capital Conservation Buffer To Risk Weighted Assets Ratio	6.375%
Common Equity Tier 1 Risk Based Capital Required To Be Well Capitalized Amount	$ 346,833
Common Equity Tier 1 Risk Based Capital Required To Be Well Capitalized To Risk Weighted Assets Ratio	6.50%
Tier 1 Risk Based Capital Amount	$ 693,277
Tier 1 Risk Based Capital To Risk Weighted Assets Ratio	12.99%
Tier 1 Risk Based Capital Required For Capital Adequacy Amount	$ 320,153
Tier 1 Risk Based Capital Required For Capital Adequacy To Risk Weighted Assets Ratio	6.00%
Tier 1 Risk Based Capital With Capital Conservation Buffer Amount	$ 420,202
Tier 1 Risk Based Capital With Capital Conservation Buffer To Risk Weighted Assets Ratio	7.875%
Tier 1 Risk Based Capital Required To Be Well Capitalized Amount	$ 426,871
Tier 1 Risk Based Capital Required To Be Well Capitalized To Risk Weighted Assets Ratio	8.00%
Tier 1 Capital Amount	$ 693,277
Tier 1 Capital To Average Assets Ratio	9.21%
Tier 1 Capital Required For Capital Adequacy Amount	$ 301,193
Tier 1 Capital Required For Capital Adequacy To Average Assets Ratio	4.00%
Tier 1 Capital Required To Be Well Capitalized Amount	$ 376,491
Tier 1 Capital Required To Be Well Capitalized To Average Assets Ratio	5.00%

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2018USD ($)
2016 [Member]
Stockholders Equity [Line Items]
Implementation of the capital conservation buffer, Percentage	0.625%
Capital conservation buffer implementation phase-in period	4 years
2019 [Member]
Stockholders Equity [Line Items]
Capital Conservation Buffer Maximum Level	2.50%
Maximum [Member]
Stockholders Equity [Line Items]
Quantitative limit for trust preferred securities to be included in tier 1 capital	$ 15,000,000,000

Net Income Per Common Share - B

Net Income Per Common Share - Basic and Diluted Net Income Per Common Share Based on Weighted-average Shares Outstanding (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share Reconciliation [Abstract]
Income available to common stockholders	$ 32,883	$ 21,710	$ 93,089	$ 66,942
Income available to common stockholders plus assumed exercises of stock options	$ 32,883	$ 21,710	$ 93,089	$ 66,942
Income available to common stockholders - Shares	32,742,480	31,838,392	32,678,310	31,792,270
Dilutive effect of stock options - Shares	761,663	753,885	752,451	741,949
Income available to common stockholders plus assumed exercises of stock options - Shares	33,504,143	32,592,277	33,430,761	32,534,219
Income available to common stockholders - Per Share Amount	$ 1.01	$ 0.68	$ 2.85	$ 2.11
Income available to common stockholders plus assumed exercises of stock options - Per Share Amount	$ 0.98	$ 0.67	$ 2.78	$ 2.06

Net Income Per Common Share - O

Net Income Per Common Share - Options Excluded From Computation of Diluted Net Income Per Common Share (Detail) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Schedule Of Antidilutive Securities Excluded From Computation Of Earnings Per Share [Abstract]
Shares	83,799	75,543	84,368	39,120

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($)	9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Debt Instrument Fair Value Disclosure [Abstract]
Days from origination after which mortgage loan are sold	30 days
Transfer of securities between levels of fair value hierarchy	$ 0	$ 0
Amount of non-financial assets (liabilities) measured at fair value on a recurring basis	$ 0		$ 0

Fair Value Measurements - Fair

Fair Value Measurements - Fair Value of Financial Assets and Liabilities Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale, at fair value	$ 475,640	$ 467,703
Equity securities	6,509	5,704
Derivative assets	247	295
Derivative liabilities	229	261
Loans held for sale	4,739	6,173
U.S. Treasuries [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale, at fair value	397,466	312,802
U.S. Federal Agencies [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale, at fair value	31,840	88,851
Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale, at fair value	16,134	17,976
States and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale, at fair value	30,200	42,370
Level 1 Inputs [Member] | U.S. Treasuries [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale, at fair value	397,466	312,802
Level 2 Inputs [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	247	295
Derivative liabilities	229	261
Loans held for sale	4,739	6,173
Level 2 Inputs [Member] | U.S. Federal Agencies [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale, at fair value	31,840	88,851
Level 2 Inputs [Member] | Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale, at fair value	2,691	3,509
Level 2 Inputs [Member] | States and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale, at fair value	30,200	42,370
Level 3 Inputs [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	6,509	5,704
Level 3 Inputs [Member] | Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale, at fair value	$ 13,443	$ 14,467

Fair Value Measurements - Chang

Fair Value Measurements - Changes in Level 3 Assets Measured at Estimated Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation Calculation Roll Forward
Balance at the beginning of the year	$ 20,171	$ 21,385
Purchases	2,118	1,668
Settlements	(2,385)	(722)
Sales	(73)	(5,412)
Gains included in earnings	67	4,060
Total unrealized losses	54	(808)
Balance at the end of the period	$ 19,952	$ 20,171

Fair Value Measurements - Asset

Fair Value Measurements - Assets Measured at Fair Value on Nonrecurring Basis (Detail) - Level 3 [Member] - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Impaired Loans (Less Specific Allowance) [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Total Fair Value	$ 39,620	$ 34,041
Repossessed Assets [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Total Fair Value	244	288
Other Real Estate Owned [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Total Fair Value	$ 4,610	$ 1,995

Fair Value Measurements - Estim

Fair Value Measurements - Estimated Fair Values of Company's Financial Instruments (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
FINANCIAL ASSETS
Securities held for investment, Carrying Amount	$ 1,440	$ 2,292
Loans, net of allowance for loan losses, Carrying Amount	4,895,653	4,670,329
Securities held for investment, Fair Value	1,447	2,303
FINANCIAL LIABILITIES
Deposits, Carrying Amount	6,643,131	6,415,045
Short-term borrowings, Carrying Amount	2,200	900
Junior subordinated debentures, Carrying Amount	31,959	31,959
OFF-BALANCE SHEET FINANCIAL INSTRUMENTS
Loan commitments, Fair Value	2,006	1,839
Letters of credit, Fair Value	425	428
Level 2 Inputs [Member]
FINANCIAL ASSETS
Cash and cash equivalents, Carrying Amount	1,792,766	1,758,575
Securities held for investment, Carrying Amount	940	1,792
Cash and cash equivalents, Fair Value	1,792,766	1,758,575
Securities held for investment, Fair Value	947	1,803
FINANCIAL LIABILITIES
Deposits, Carrying Amount	6,643,131	6,415,045
Short-term borrowings, Carrying Amount	2,200	900
Junior subordinated debentures, Carrying Amount	31,959	31,959
Deposits, Fair Value	6,760,191	6,490,309
Short-term borrowings, Fair Value	2,200	900
Junior subordinated debentures, Fair Value	34,795	34,661
Level 3 Inputs [Member]
FINANCIAL ASSETS
Securities held for investment, Carrying Amount	500	500
Loans, net of allowance for loan losses, Carrying Amount	4,895,653	4,670,329
Securities held for investment, Fair Value	500	500
Loans, net of allowance for loan losses, Fair Value	$ 4,854,167	$ 4,663,608

Segment Information - Additiona

Segment Information - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2018Business_Unit
Segment Reporting [Abstract]
Number of principal business units	4

Segment Information - Results o

Segment Information - Results of Operations and Selected Financial Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Segment Reporting Information [Line Items]
Net interest income (expense)	$ 65,673	$ 57,233	$ 193,588	$ 168,440
Noninterest income	32,801	29,169	93,348	85,237
Income before taxes	41,918	32,526	118,695	99,347
Total Assets	7,602,438		7,602,438		$ 7,253,156
Operating Segments [Member] | Metropolitan Banks [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)	21,313	18,617	62,701	54,969
Noninterest income	4,266	3,981	12,391	11,748
Income before taxes	16,538	11,499	46,157	36,357
Total Assets	2,724,502		2,724,502		2,552,024
Operating Segments [Member] | Community Banks [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)	42,773	37,310	126,223	109,480
Noninterest income	15,404	13,884	44,189	40,821
Income before taxes	27,515	23,810	81,805	71,038
Total Assets	4,841,853		4,841,853		4,544,196
Operating Segments [Member] | Other Financial Services [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)	1,241	1,332	4,074	4,525
Noninterest income	10,264	9,217	28,784	24,983
Income before taxes	4,440	3,762	13,511	10,526
Total Assets	80,411		80,411		117,332
Operating Segments [Member] | Executive, Operations & Support [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)	346	(26)	590	(534)
Noninterest income	36,503	24,470	102,306	74,586
Income before taxes	26,344	15,137	69,881	47,368
Total Assets	945,221		945,221		885,590
Eliminations [Member]
Segment Reporting Information [Line Items]
Noninterest income	(33,636)	(22,383)	(94,322)	(66,901)
Income before taxes	(32,919)	$ (21,682)	(92,659)	$ (65,942)
Total Assets	$ (989,549)		$ (989,549)		$ (845,986)