Loans (Tables)

12 Months Ended

Dec. 31, 2017

Year-end loans, including leases net of unearned discounts, consisted of the following:



	2017		2016
Commercial and industrial	$	4,792,388	$	4,344,000
Energy:
Production	1,182,326		971,767
Service	171,795		221,213
Other	144,972		193,081
Total energy	1,499,093		1,386,061
Commercial real estate:
Commercial mortgages	3,887,742		3,481,157
Construction	1,066,696		1,043,261
Land	331,986		311,030
Total commercial real estate	5,286,424		4,835,448
Consumer real estate:
Home equity loans	355,342		345,130
Home equity lines of credit	291,950		264,862
Other	376,002		326,793
Total consumer real estate	1,023,294		936,785
Total real estate	6,309,718		5,772,233
Consumer and other	544,466		473,098
Total loans	$	13,145,665	$	11,975,392

Activities in Related Party Loans

Activity in related party loans during 2017 is presented in the following table. Other changes were primarily related to changes in related-party status.



Balance outstanding at December 31, 2016	$	142,771
Principal additions	270,684
Principal reductions	(271,325		)
Other changes	24,273
Balance outstanding at December 31, 2017	$	166,403

Non-Accrual Loans, Segregated by Class of Loans

Year-end non-accrual loans, segregated by class of loans, were as follows:



	2017		2016
Commercial and industrial	$	46,186	$	31,475
Energy	94,302		57,571
Commercial real estate:
Buildings, land and other	7,589		8,550
Construction	—		—
Consumer real estate	2,109		2,130
Consumer and other	128		425
Total	$	150,314	$	100,151

Age Analysis of Past Due Loans, Segregated by Class of Loans

An age analysis of past due loans (including both accruing and non-accruing loans), segregated by class of loans, as of December 31, 2017 was as follows:



	Loans 30-89 Days Past Due		Loans 90 or More Days Past Due		Total Past Due Loans		Current Loans		Total Loans		Accruing Loans 90 or More Days Past Due
Commercial and industrial	$	41,169	$	12,418	$	53,587	$	4,738,801	$	4,792,388	$	5,589
Energy	22,100		49,214		71,314		1,427,779		1,499,093		100
Commercial real estate:
Buildings, land and other	29,714		4,482		34,196		4,185,532		4,219,728		2,615
Construction	2,191		2,331		4,522		1,062,174		1,066,696		2,331
Consumer real estate	7,707		4,427		12,134		1,011,160		1,023,294		3,138
Consumer and other	4,791		665		5,456		539,010		544,466		659
Total	$	107,672	$	73,537	$	181,209	$	12,964,456	$	13,145,665	$	14,432

Impaired Loans

Year-end impaired loans are set forth in the following table. No interest income was recognized on impaired loans subsequent to their classification as impaired.



	Unpaid Contractual Principal Balance		Recorded Investment With No Allowance		Recorded Investment With Allowance		Total Recorded Investment		Related Allowance		Average Recorded Investment
2017
Commercial and industrial	$	60,781	$	28,038	$	15,722	$	43,760	$	7,553	$	30,073
Energy	99,606		33,080		61,162		94,242		13,267		76,492
Commercial real estate:
Buildings, land and other	10,795		6,394		—		6,394		—		6,164
Construction	—		—		—		—		—		—
Consumer real estate	1,214		1,214		—		1,214		—		1,167
Consumer and other	—		—		—		—		—		11
Total	$	172,396	$	68,726	$	76,884	$	145,610	$	20,820	$	113,907
2016
Commercial and industrial	$	40,288	$	19,862	$	9,047	$	28,909	$	5,436	$	26,074
Energy	60,522		27,759		29,804		57,563		3,750		57,360
Commercial real estate:
Buildings, land and other	11,369		6,866		—		6,866		—		17,729
Construction	—		—		—		—		—		438
Consumer real estate	977		655		—		655		—		537
Consumer and other	32		30		—		30		—		25
Total	$	113,188	$	55,172	$	38,851	$	94,023	$	9,186	$	102,163
2015
Commercial and industrial	$	26,067	$	18,776	$	4,084	$	22,860	$	2,378	$	27,338
Energy	25,240		8,689		12,450		21,139		2,000		7,235
Commercial real estate:
Buildings, land and other	37,126		32,425		—		32,425		—		18,211
Construction	793		569		—		569		—		1,320
Consumer real estate	755		485		—		485		—		664
Consumer and other	—		—		—		—		—		—
Total	$	89,981	$	60,944	$	16,534	$	77,478	$	4,378	$	54,768

Troubled Debt Restructurings

Troubled debt restructurings that occurred during 2017, 2016 and 2015 are set forth in the following table.



	2017				2016				2015
	Balance at Restructure		Balance at Year-end		Balance at Restructure		Balance at Year-end		Balance at Restructure		Balance at Year-end
Commercial and industrial	$	4,026	$	3,766	$	2,148	$	1,022	$	709	$	536
Energy	56,096		54,330		87,572		43,841		—		—
Commercial real estate:
Buildings, land and other	—		—		1,455		—		—		—
Construction	388		388		243		—		—		—
	$	60,510	$	58,484	$	91,418	$	44,863	$	709	$	536

Restructured Loans Past Due in Excess of 90 Days on Financing Receivables [Table Text Block]

Additional information related to restructured loans was as follows:



	2017		2016		2015
Restructured loans past due in excess of 90 days at period-end:
Number of loans	1		2		1
Dollar amount of loans	$	43,137	$	3,230	$	259
Restructured loans on non-accrual status at period end	53,622		44,863		536
Charge-offs of restructured loans:
Recognized in connection with restructuring	—		4,115		88
Recognized on previously restructured loans	9,951		9,490		—
Proceeds from sale of restructured loans	—		30,470		—

Weighted Average Risk Grades for All Commercial Loans by Class

The following tables present weighted average risk grades for all commercial loans by class.



	December 31, 2017			December 31, 2016
	Weighted Average Risk Grade	Loans		Weighted Average Risk Grade	Loans
Commercial and industrial
Risk grades 1-8	6.06	$	4,378,839	6.01	$	3,989,722
Risk grade 9	9.00	170,285		9.00	106,988
Risk grade 10	10.00	99,260		10.00	115,420
Risk grade 11	11.00	97,818		11.00	100,245
Risk grade 12	12.00	38,633		12.00	25,939
Risk grade 13	13.00	7,553		13.00	5,686
Total	6.41	$	4,792,388	6.35	$	4,344,000
Energy
Risk grades 1-8	6.01	$	1,199,207	6.34	$	854,688
Risk grade 9	9.00	50,427		9.00	78,524
Risk grade 10	10.00	64,282		10.00	150,872
Risk grade 11	11.00	90,875		11.00	244,406
Risk grade 12	12.00	81,035		12.00	53,821
Risk grade 13	13.00	13,267		13.00	3,750
Total	6.97	$	1,499,093	7.95	$	1,386,061
Commercial real estate:
Buildings, land and other
Risk grades 1-8	6.75	$	3,868,659	6.67	$	3,463,064
Risk grade 9	9.00	151,487		9.00	109,110
Risk grade 10	10.00	129,391		10.00	145,067
Risk grade 11	11.00	62,602		11.00	66,396
Risk grade 12	12.00	7,589		12.00	8,550
Risk grade 13	13.00	—		13.00	—
Total	7.00	$	4,219,728	6.95	$	3,792,187
Construction
Risk grades 1-8	7.11	$	1,019,635	6.97	$	1,023,194
Risk grade 9	9.00	18,042		9.00	15,829
Risk grade 10	10.00	23,393		10.00	2,889
Risk grade 11	11.00	5,626		11.00	1,349
Risk grade 12	12.00	—		12.00	—
Risk grade 13	13.00	—		13.00	—
Total	7.23	$	1,066,696	7.01	$	1,043,261

Net (Charge-Offs)/Recoveries, Segregated by Class of Loans

Net (charge-offs)/recoveries, segregated by class of loan, were as follows:



	2017			2016			2015
Commercial and industrial	$	(17,453	)	$	(12,259	)	$	(6,535	)
Energy	(10,009		)	(18,588		)	(5,997		)
Commercial real estate:
Buildings, land and other	735			813			314
Construction	11			23			18
Consumer real estate	(506		)	(257		)	(91		)
Consumer and other	(5,919		)	(4,219		)	(3,237		)
Total	$	(33,141	)	$	(34,487	)	$	(15,528	)

Unallocated Portion of the Allowance for Loan Losses

The following table presents details of the allowance for loan losses, segregated by loan portfolio segment.



	Commercial and Industrial		Energy		Commercial Real Estate		Consumer Real Estate		Consumer and Other			Total
December 31, 2017
Historical valuation allowances	$	26,401	$	22,073	$	18,931	$	2,473	$	5,603		$	75,481
Specific valuation allowances	7,553		13,267		—		—		—			20,820
General valuation allowances	9,112		7,964		4,165		2,133		(91		)	23,283
Macroeconomic valuation allowances	16,548		8,224		7,852		1,051		2,105			35,780
Total	$	59,614	$	51,528	$	30,948	$	5,657	$	7,617		$	155,364
December 31, 2016
Historical valuation allowances	$	33,251	$	34,626	$	16,976	$	2,225	$	4,585		$	91,663
Specific valuation allowances	5,436		3,750		—		—		—			9,186
General valuation allowances	6,708		3,769		5,004		1,506		(144		)	16,843
Macroeconomic valuation allowances	7,520		18,508		8,233		507		585			35,353
Total	$	52,915	$	60,653	$	30,213	$	4,238	$	5,026		$	153,045

Investment in Loans Related to the Allowance for Loan Losses by Portfolio Segment Disaggregated Based on Impairment Methodology

The Corporation’s recorded investment in loans related to each balance in the allowance for loan losses by portfolio segment and detailed on the basis of the impairment methodology used by the Corporation was as follows:



	Commercial and Industrial		Energy		Commercial Real Estate		Consumer Real Estate		Consumer and Other		Total
December 31, 2017
Individually evaluated	$	43,760	$	94,242	$	6,394	$	1,214	$	—	$	145,610
Collectively evaluated	4,748,628		1,404,851		5,280,030		1,022,080		544,466		13,000,055
Total	$	4,792,388	$	1,499,093	$	5,286,424	$	1,023,294	$	544,466	$	13,145,665
December 31, 2016
Individually evaluated	$	28,909	$	57,563	$	6,866	$	655	$	30	$	94,023
Collectively evaluated	4,315,091		1,328,498		4,828,582		936,130		473,068		11,881,369
Total	$	4,344,000	$	1,386,061	$	4,835,448	$	936,785	$	473,098	$	11,975,392

Activity in Allowance for Loan Losses by Portfolio Segment

The following table details activity in the allowance for loan losses by portfolio segment for 2017, 2016 and 2015. Allocation of a portion of the allowance to one category of loans does not preclude its availability to absorb losses in other categories.



	Commercial and Industrial			Energy			Commercial Real Estate			Consumer Real Estate			Consumer and Other			Total
2017
Beginning balance	$	52,915		$	60,653		$	30,213		$	4,238		$	5,026		$	153,045
Provision for loan losses	24,152			884			(11		)	1,925			8,510			35,460
Charge-offs	(20,619		)	(10,595		)	(86		)	(925		)	(15,579		)	(47,804		)
Recoveries	3,166			586			832			419			9,660			14,663
Net charge-offs	(17,453		)	(10,009		)	746			(506		)	(5,919		)	(33,141		)
Ending balance	$	59,614		$	51,528		$	30,948		$	5,657		$	7,617		$	155,364
Allocated to loans:
Individually evaluated for impairment	$	7,553		$	13,267		$	—		$	—		$	—		$	20,820
Collectively evaluated for impairment	52,061			38,261			30,948			5,657			7,617			134,544
Ending balance	$	59,614		$	51,528		$	30,948		$	5,657		$	7,617		$	155,364
2016
Beginning balance	$	42,993		$	54,696		$	24,313		$	4,659		$	9,198		$	135,859
Provision for loan losses	22,181			24,545			5,064			(164		)	47			51,673
Charge-offs	(15,910		)	(18,644		)	(82		)	(814		)	(12,878		)	(48,328		)
Recoveries	3,651			56			918			557			8,659			13,841
Net charge-offs	(12,259		)	(18,588		)	836			(257		)	(4,219		)	(34,487		)
Ending balance	$	52,915		$	60,653		$	30,213		$	4,238		$	5,026		$	153,045
Allocated to loans:
Individually evaluated for impairment	$	5,436		$	3,750		$	—		$	—		$	—		$	9,186
Collectively evaluated for impairment	47,479			56,903			30,213			4,238			5,026			143,859
Ending balance	$	52,915		$	60,653		$	30,213		$	4,238		$	5,026		$	153,045
2015
Beginning balance	$	44,273		$	14,919		$	27,163		$	5,178		$	8,009		$	99,542
Provision for loan losses	5,255			45,774			(3,182		)	(428		)	4,426			51,845
Charge-offs	(11,092		)	(6,000		)	(657		)	(577		)	(11,246		)	(29,572		)
Recoveries	4,557			3			989			486			8,009			14,044
Net charge-offs	(6,535		)	(5,997		)	332			(91		)	(3,237		)	(15,528		)
Ending balance	$	42,993		$	54,696		$	24,313		$	4,659		$	9,198		$	135,859
Allocated to loans:
Individually evaluated for impairment	$	2,378		$	2,000		$	—		$	—		$	—		$	4,378
Collectively evaluated for impairment	40,615			52,696			24,313			4,659			9,198			131,481
Ending balance	$	42,993		$	54,696		$	24,313		$	4,659		$	9,198		$	135,859