	December 31,
	2018					2017
	Amount		Percent			Amount		Percent
	(Dollars in thousands)
Commercial and financial:
Commercial and industrial	$	1,032,787		20.76	%	$	995,207		21.08	%
Oil & gas production and equipment		94,729		1.90			95,574		2.02
Agriculture		136,313		2.74			141,249		2.99
State and political subdivisions:
Taxable		76,211		1.53			73,827		1.56
Tax-exempt		48,415		0.97			48,626		1.03
Real estate:
Construction		451,224		9.07			437,277		9.26
Farmland		219,241		4.41			195,162		4.13
One to four family residences		979,170		19.68			875,766		18.55
Multifamily residential properties		65,949		1.33			46,030		0.98
Commercial		1,506,937		30.28			1,487,927		31.51
Consumer		328,069		6.59			284,373		6.02
Other (not classified above)		36,931		0.74			40,977		0.87
Total loans	$	4,975,976		100.00	%	$	4,721,995		100.00	%

The Company’s loans are mostly to customers within Oklahoma and approximately 65% 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 $60 million at December 31, 2018 and approximately $81 million at December 31, 2017.

There are inherent risks associated with the Company’s lending activities. These risks include, among other things, the impact of changes in interest rates and changes in the economic conditions in the markets where the Company operates. Increases in interest rates and/or weakening economic conditions could adversely impact the ability of borrowers to repay outstanding loans or the value of the collateral securing these loans. The Company is also subject to various laws and regulations that affect its lending activities. Failure to comply with applicable laws and regulations could subject the Company to regulatory enforcement action that could result in the assessment of significant civil money penalties against the Company. As a lender, the Company faces the risk that a significant number of its borrowers will fail to pay their loans when due. If borrower defaults cause losses in excess of the Company’s allowance for loan losses, it could have an adverse effect on the Company’s business, profitability, and financial condition.

Loans secured by real estate, including farmland, multifamily, commercial, one-to-four family residential and construction and development loans, have been a large portion of the Company’s loan portfolio. The Company is subject to risk of future market fluctuations in property values relating to these loans. In addition, multi-family and commercial real estate (“CRE”) loans represent the majority of the Company’s real estate loans outstanding. A decline in tenant occupancy due to such factors or for other reasons could adversely impact the ability of the Company’s borrowers to repay their loans on a timely basis, which could have a negative impact on the Company’s financial condition and results of operation. The Company attempts to manage this risk through rigorous loan underwriting standards.

During the ordinary course of business, the Company may foreclose on and take title to properties securing certain loans. In doing so, there is a risk that hazardous or toxic substances could be found on these properties. If hazardous or toxic substances are found, the Company may be liable for remediation costs, as well as for personal injury and property damage.

Had nonaccrual loans performed in accordance with their original contractual terms, the Company would have recognized additional interest income of approximately $2.3 million in 2018, $1.8 million in 2017 and $2.0 million in 2016.

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.

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 December 31, 2018
Real estate:
Non-residential real estate owner occupied	$	5,114	$	810	$	43	$	5,967	$	620,654	$	626,621	$	—
Non-residential real estate other		2,772		32		114		2,918		1,143,210		1,146,128		—
Residential real estate permanent mortgage		2,448		653		693		3,794		324,908		328,702		430
Residential real estate all other		1,728		292		2,799		4,819		822,685		827,504		612
Commercial and financial:
Non-consumer non-real estate		3,620		702		833		5,155		1,278,499		1,283,654		282
Consumer non-real estate		1,991		565		559		3,115		323,747		326,862		325
Other loans		322		158		178		658		141,251		141,909		—
Acquired loans		5,240		1,669		4,936		11,845		282,751		294,596		267
Total	$	23,235	$	4,881	$	10,155	$	38,271	$	4,937,705	$	4,975,976	$	1,916
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

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 year ended December 31, 2018 no material amount of interest income was recognized on impaired loans subsequent to their classification as impaired. During the year ended December 31, 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 December 31, 2018
Real estate:
Non-residential real estate owner occupied	$	7,126	$	6,933	$	202	$	7,739
Non-residential real estate other		949		757		50		6,057
Residential real estate permanent mortgage		1,789		1,545		127		1,650
Residential real estate all other		7,177		6,862		2,433		7,154
Commercial and financial:
Non-consumer non-real estate		18,507		10,977		881		12,140
Consumer non-real estate		928		829		131		846
Other loans		710		490		35		481
Acquired loans		12,846		9,864		2		11,050
Total	$	50,032	$	38,257	$	3,861	$	47,117

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

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.

Grade 1 – Acceptable - Loans graded 1 represent reasonable and satisfactory credit risk which requires normal attention and supervision. Capacity to repay through primary and/or secondary sources is not questioned.

Grade 2 – Acceptable - Increased Attention - This category consists of loans that have credit characteristics deserving management’s close attention. These potential weaknesses could result in deterioration of the repayment prospects for the loan or the Bank’s credit position at some future date. Such credit characteristics include loans to highly leveraged borrowers in cyclical industries, adverse financial trends which could potentially weaken repayment capacity, loans that have fundamental structure deficiencies, loans lacking secondary sources of repayment where prudent, and loans with deficiencies in essential documentation, including financial information.

Grade 3 – Loans with Problem Potential - This category consists of performing loans which are considered to exhibit problem potential. Loans in this category would generally include, but not be limited to, borrowers with a weakened financial condition or poor performance history, past dues, loans restructured to reduce payments to an amount that is below market standards and/or loans with severe documentation problems. In general, these loans have no identifiable loss potential in the near future, however; the possibility of a loss developing is heightened.

Grade 4 - Problem Loans/Assets – Nonperforming - This category consists of nonperforming loans/assets which are considered to be problems. Nonperforming loans are described as being 90 days and over past due and still accruing, and loans that are nonaccrual. The government guaranteed portion of Small Business Administration (“SBA”) loans is excluded.

Grade 5 - Loss Potential - This category consists of loans/assets which are considered to possess loss potential. While the loss may not occur in the current year, management expects that loans/assets in this category will ultimately result in a loss, unless substantial improvement occurs.

Grade 6 - Charge Off - This category consists of loans that are considered uncollectible and other assets with little or no value.

	Internal Loan Grading
	Grade
		1		2		3		4		5	Total
	(Dollars in thousands)
As of December 31, 2018
Real estate:
Non-residential real estate owner occupied	$	451,059	$	157,715	$	16,949	$	898	$	—	$	626,621
Non-residential real estate other		932,454		188,341		25,146		187		—		1,146,128
Residential real estate permanent mortgage		279,870		39,806		7,401		1,625		—		328,702
Residential real estate all other		644,217		162,003		15,232		6,052		—		827,504
Commercial and financial:
Non-consumer non-real estate		1,000,089		264,134		15,128		4,303		—		1,283,654
Consumer non-real estate		302,217		21,600		2,255		790		—		326,862
Other loans		136,132		5,542		116		119		—		141,909
Acquired loans		156,008		109,075		20,884		8,284		345		294,596
Total	$	3,902,046	$	948,216	$	103,111	$	22,258	$	345	$	4,975,976

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

The allowance for loan losses (“ALL”) is determined by a calculation based on segmenting the loans into the following categories: (1) adversely graded loans [Grades 3, 4 and 5] that have a specific reserve allocation; (2) loans without a specific reserve segmented by loans secured by real estate other than one-to-four family residential property, loans secured by one-to-four family residential property, commercial, industrial and agricultural loans not secured by real estate, consumer purpose loans not secured by real estate, and loans over 60 days past due that are not otherwise Grade 3, 4, or 5; (3) Grade 2 loans; (4) Grade 1 loans and (5) loans held for sale which are excluded.

The ALL is calculated as the sum of the following: (1) the total dollar amount of specific reserve allocations; (2) the dollar amount derived by multiplying each segment of adversely graded loans without a specific reserve allocation times its respective reserve factor; (3) the dollar amount derived by multiplying Grade 2 loans and Grade 1 loans (less certain exclusions) times the respective reserve factor; and (4) other adjustments as deemed appropriate and documented by the Senior Loan Committee or Board of Directors.

The amount of the ALL is an estimate based upon factors which are subject to rapid change due to changing economic conditions and the economic prospects of borrowers. It is reasonably possible that a material change could occur in the estimated ALL in the near term.

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)
As of December 31, 2018
Real estate:
Non-residential real estate owner occupied	$	6,195	$	(282	)	$	17	$	(265	)	$	398		$	6,328
Non-residential real estate other		10,519		(93	)		41		(52	)		560			11,027
Residential real estate permanent mortgage		3,226		(174	)		26		(148	)		183			3,261
Residential real estate all other		9,672		(395	)		106		(289	)		1,290			10,673
Commercial and financial:
Non-consumer non-real estate		15,334		(2,257	)		92		(2,165	)		(18	)		13,151
Consumer non-real estate		2,793		(1,066	)		245		(821	)		1,093			3,065
Other loans		2,481		(16	)		361		345			(403	)		2,423
Acquired loans		1,446		(720	)		36		(684	)		699			1,461
Total	$	51,666	$	(5,003	)	$	924	$	(4,079	)	$	3,802		$	51,389
As of December 31, 2017
Real estate:
Non-residential real estate owner occupied	$	5,602	$	(74	)	$	6	$	(68	)	$	661		$	6,195
Non-residential real estate other		10,793		(47	)		16		(31	)		(243	)		10,519
Residential real estate permanent mortgage		3,129		(373	)		25		(348	)		445			3,226
Residential real estate all other		8,622		(330	)		66		(264	)		1,314			9,672
Commercial and financial:
Non-consumer non-real estate		12,421		(1,344	)		1,033		(311	)		3,224			15,334
Consumer non-real estate		2,804		(913	)		180		(733	)		722			2,793
Other loans		4,045		(3,727	)		23		(3,704	)		2,140			2,481
Acquired loans		1,277		(157	)		77		(80	)		249			1,446
Total	$	48,693	$	(6,965	)	$	1,426	$	(5,539	)	$	8,512		$	51,666

The following table details the amount of ALL by class of loans for the period presented, on the basis of the impairment methodology used by the Company.

	ALL
	December 31, 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	$	669	$	5,659	$	656	$	5,539
Non-residential real estate other		1,119		9,908		751		9,768
Residential real estate permanent mortgage		505		2,756		483		2,743
Residential real estate all other		3,413		7,260		2,761		6,911
Commercial and financial:
Non-consumer non-real estate		2,114		11,037		4,651		10,683
Consumer non-real estate		374		2,691		429		2,364
Other loans		65		2,358		133		2,348
Acquired loans		—		1,461		12		1,434
Total	$	8,259	$	43,130	$	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
	December 31, 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	$	17,846	$	608,775	$	—	$	15,281	$	626,337	$	—
Non-residential real estate other		25,333		1,120,795		—		17,013		1,109,578		—
Residential real estate permanent mortgage		9,026		319,676		—		8,100		322,234		—
Residential real estate all other		21,285		806,219		—		15,052		770,603		—
Commercial and financial:
Non-consumer non-real estate		19,432		1,264,222		—		31,349		1,253,056		—
Consumer non-real estate		3,093		323,769		—		2,600		286,320		—
Other loans		209		141,700		—		764		143,681		—
Acquired loans		22,132		265,084		7,380		14,464		100,106		5,457
Total	$	118,356	$	4,850,240	$	7,380	$	104,623	$	4,611,915	$	5,457

Transfers from loans and premises and equipment 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 and premises and equipment to other real estate owned and repossessed assets during the periods presented are summarized as follows:

The Company has made loans in the ordinary course of business to the executive officers and directors of the Company and to certain affiliates of these executive officers and directors. Management believes that all such loans were made on substantially the same terms as those prevailing at the time for comparable transactions with other persons and do not represent more than a normal risk of collectability or present other unfavorable features. A summary of these loans is as follows: