Loans and Allowances for Credit Losses (Tables)

3 Months Ended

12 Months Ended

Mar. 31, 2020

Mar. 31, 2019

Dec. 31, 2019

Loans and Leases Receivable, Net Amount [Abstract]

Schedule of Loans by Portfolio Segment [Table Text Block]

Portfolio segments of the loan portfolio are as follows (in thousands):

	March 31, 2020
	Fixed Rate		Variable Rate		Non-accrual		Total
Commercial	3,205,558		11,471,793		118,624		$	14,795,975
Commercial real estate	1,045,825		3,395,715		8,545		4,450,085
Loans to individuals	1,878,018		1,303,889		36,003		3,217,910
Total	$	6,129,401	$	16,171,397	$	163,172	$	22,463,970

Portfolio segments of the loan portfolio are as follows (in thousands):

	December 31, 2019
	Fixed Rate		Variable Rate		Non-accrual		Total
Commercial	$	3,231,485	$	10,684,749	$	115,416	$	14,031,650
Commercial real estate	1,056,321		3,349,836		27,626		4,433,783
Residential mortgage	1,652,653		393,897		37,622		2,084,172
Personal	193,903		1,007,192		287		1,201,382
Total	$	6,134,362	$	15,435,674	$	180,951	$	21,750,987
Accruing loans past due (90 days)1							$	7,680

¹  Excludes residential mortgage loans guaranteed by agencies of the U.S. government

Rollforward of Allowance For Loan Losses And Accrual for Off-Balance Sheet Credit Losses [Table Text Block]

The activity in the allowance for loan losses and the allowance for off-balance sheet credit losses related to loan commitments and standby letters of credit for the three months ended March 31, 2020 is summarized as follows (in thousands):

	Commercial			Commercial Real Estate			Loans to Individuals			Nonspecific Allowance			Total
Allowance for loan losses:
Beginning balance	$	118,187		$	51,805		$	23,572		$	17,195		$	210,759
Transition adjustment	33,681			(4,620		)	13,943			(17,195		)	25,809
Beginning balance, adjusted	151,868			47,185			37,515			—			236,568
Provision for loan losses	77,723			5,115			13,126			—			95,964
Loans charged off	(16,615		)	(886		)	(1,416		)	—			(18,917		)
Recoveries of loans previously charged off	462			47			1,187			—			1,696
Ending Balance	213,438			51,461			50,412			—			315,311
Allowance for off-balance sheet credit risk from unfunded loan commitments:
Beginning balance	1,434			107			44			—			1,585
Transition adjustment	10,144			11,660			1,748			—			23,552
Beginning balance, adjusted	11,578			11,767			1,792			—			25,137
Provision for off-balance sheet credit risk	2,462			808			107			—			3,377
Ending Balance	14,040			12,575			1,899			—			28,514

Changes in our reasonable and supportable forecasts of macroeconomic variables, primarily due to the impact of the COVID-19 pandemic, oil price declines, and other assumptions, required a provision of $66.2 million during the first quarter of 2020. All other changes totaled $33.1 million, which included $7.5 million related to loan growth, $8.4 million related to changes in impairment, risk grading and other portfolio changes and net charge-offs of $17.2 million.

The allowance for loan losses and recorded investment of the related loans by portfolio segment for each measurement method at March 31, 2020 is as follows (in thousands):

	Collectively Measured for General Allowances				Individually Measured for Specific Allowances				Total
	Recorded Investment		Related Allowance		Recorded Investment		Related Allowance		Recorded Investment		Related Allowance
Commercial	$	14,677,351	$	203,554	$	118,624	$	9,884	$	14,795,975	$	213,438
Commercial real estate	4,441,540		51,461		8,545		—		4,450,085		51,461
Loans to individuals	3,181,907		50,412		36,003		—		3,217,910		50,412
Total	22,300,798		305,427		163,172		9,884		22,463,970		315,311

The activity in the allowance for loan losses and the allowance for off-balance sheet credit losses related to loan commitments and standby letters of credit for the three months ended March 31, 2019 is summarized as follows (in thousands):

	Commercial			Commercial Real Estate			Residential Mortgage			Personal			Nonspecific Allowance		Total
Allowance for loan losses:
Beginning balance	$	102,226		$	60,026		$	17,964		$	9,473		$	17,768	$	207,457
Provision for loan losses	11,108			(2,004		)	(2,408		)	(137		)	1,410		7,969
Loans charged off	(10,468		)	—			(42		)	(1,265		)	—		(11,775		)
Recoveries	711			112			154			712			—		1,689
Ending balance	$	103,577		$	58,134		$	15,668		$	8,783		$	19,178	$	205,340
Allowance for off-balance sheet credit losses:
Beginning balance	1,655			52			52			31			—		$	1,790
Provision for off-balance sheet credit losses	70			(4		)	(5		)	(30		)	—		31
Ending balance	$	1,725		$	48		$	47		$	1		$	—	$	1,821
Total provision for credit losses	$	11,178		$	(2,008	)	$	(2,413	)	$	(167	)	$	1,410	$	8,000

The allowance for loan losses and recorded investment of the related loans by portfolio segment for each impairment measurement method at December 31, 2019 is as follows (in thousands):

	Collectively Measured for Impairment				Individually Measured for Impairment				Total
	Recorded Investment		Related Allowance		Recorded Investment		Related Allowance		Recorded Investment		Related Allowance
Commercial	$	13,916,234	$	100,773	$	115,416	$	17,414	$	14,031,650	$	118,187
Commercial real estate	4,406,157		51,805		27,626		—		4,433,783		51,805
Residential mortgage	2,046,550		14,400		37,622		—		2,084,172		14,400
Personal	1,201,095		9,172		287		—		1,201,382		9,172
Total	21,570,036		176,150		180,951		17,414		21,750,987		193,564
Nonspecific allowance	—		—		—		—		—		17,195
Total	$	21,570,036	$	176,150	$	180,951	$	17,414	$	21,750,987	$	210,759

Schedule of Credit Quality Indicators [Table Text Block]

The following table summarizes the Company’s loan portfolio at March 31, 2020 by the risk grade categories and vintage (in thousands): 

	Origination Year
	2020		2019		2018		2017		2016		Prior		Revolving Loans		Revolving Loans Converted to Term Loans		Total
Commercial:
Energy
Pass	$	2,285	$	107,434	$	74,946	$	15,377	$	1,506	$	3,484	$	3,505,123	$	—	$	3,710,155
Special Mention	—		—		10,260		—		—		—		118,222		—		128,482
Accruing Substandard	—		—		—		—		58		13,439		163,094		—		176,591
Nonaccrual	—		3,802		—		—		—		28,899		63,747		—		96,448
Total energy	2,285		111,236		85,206		15,377		1,564		45,822		3,850,186		—		4,111,676
Healthcare
Pass	131,002		615,580		623,438		479,985		250,320		806,699		205,384		27		3,112,435
Special Mention	—		—		—		3,782		178		19,133		3,515		—		26,608
Accruing Substandard	—		3,505		7,955		1,001		57		9,465		—		—		21,983
Nonaccrual	29		37		535		—		—		2,935		534		—		4,070
Total healthcare	131,031		619,122		631,928		484,768		250,555		838,232		209,433		27		3,165,096
Services
Pass	65,471		529,831		512,549		441,302		407,067		899,776		987,628		2,594		3,846,218
Special Mention	—		1,125		18,071		13,977		4,219		10,963		10,715		—		59,070
Accruing Substandard	—		10,675		1,782		2,774		8,674		3,709		14,421		—		42,035
Nonaccrual	—		—		—		2,633		1,167		3,931		694		—		8,425
Total services	65,471		541,631		532,402		460,686		421,127		918,379		1,013,458		2,594		3,955,748
General business
Pass	154,807		525,223		365,108		271,723		165,711		278,923		1,705,114		15,600		3,482,209
Special Mention	—		7,382		3,259		6,530		1,003		5,168		7,387		138		30,867
Accruing Substandard	169		8,715		5,900		4,564		6,195		5,005		10,144		6		40,698
Nonaccrual	—		1,980		4,928		1,100		1,344		161		154		14		9,681
Total general business	154,976		543,300		379,195		283,917		174,253		289,257		1,722,799		15,758		3,563,455
Total commercial	353,763		1,815,289		1,628,731		1,244,748		847,499		2,091,690		6,795,876		18,379		14,795,975
Commercial real estate:
Pass	187,958		1,085,148		1,049,257		599,480		382,196		880,706		231,526		42		4,416,313
Special Mention	—		—		—		12,167		1,640		3,152		—		—		16,959
Accruing Substandard	—		35		1,011		6,722		—		473		27		—		8,268
Nonaccrual	—		—		—		232		7,484		829		—		—		8,545
Total commercial real estate	187,958		1,085,183		1,050,268		618,601		391,320		885,160		231,553		42		4,450,085

	Origination Year
	2020		2019		2018		2017		2016		Prior		Revolving Loans		Revolving Loans Converted to Term Loans		Total
Loans to individuals:
Residential mortgage
Pass	58,635		216,234		195,224		231,620		220,120		496,676		36,298		352,870		1,807,677
Special Mention	—		—		286		38		205		1,859		246		835		3,469
Accruing Substandard	—		—		—		94		2,155		277		40		122		2,688
Nonaccrual	—		31		491		322		1,039		26,039		658		2,141		30,721
Total residential mortgage	58,635		216,265		196,001		232,074		223,519		524,851		37,242		355,968		1,844,555
Residential mortgage guaranteed by U.S. government agencies
Pass	—		1,459		8,321		13,353		28,986		140,765		—		—		192,884
Nonaccrual	—		—		—		—		—		5,005		—		—		5,005
Total residential mortgage guaranteed by U.S. government agencies	—		1,459		8,321		13,353		28,986		145,770		—		—		197,889
Personal:
Pass	48,145		234,882		88,016		115,576		74,987		103,717		505,951		3,000		1,174,274
Special Mention	—		30		37		50		49		455		2		—		623
Accruing Substandard	—		264		9		—		—		—		19		—		292
Nonaccrual	—		57		53		24		62		50		31		—		277
Total personal	48,145		235,233		88,115		115,650		75,098		104,222		506,003		3,000		1,175,466
Total loans to individuals	106,780		452,957		292,437		361,077		327,603		774,843		543,245		358,968		3,217,910
Total loans	$	648,501	$	3,353,429	$	2,971,436	$	2,224,426	$	1,566,422	$	3,751,693	$	7,570,674	$	377,389	$	22,463,970

The allowance for loan losses and recorded investment of the related loans by portfolio segment for risk graded and non-risk graded loans at December 31, 2019 is as follows (in thousands):

	Internally Risk Graded				Non-Graded				Total
	Recorded Investment		Related Allowance		Recorded Investment		Related Allowance		Recorded Investment		Related Allowance
Commercial	$	13,997,538	$	117,236	$	34,112	$	951	$	14,031,650	$	118,187
Commercial real estate	4,433,783		51,805		—		—		4,433,783		51,805
Residential mortgage	279,113		3,085		1,805,059		11,315		2,084,172		14,400
Personal	1,116,297		7,003		85,085		2,169		1,201,382		9,172
Total	19,826,731		179,129		1,924,256		14,435		21,750,987		193,564
Nonspecific allowance	—		—		—		—		—		17,195
Total	$	19,826,731	$	179,129	$	1,924,256	$	14,435	$	21,750,987	$	210,759

The following table summarizes the Company’s loan portfolio at December 31, 2019 by the risk grade categories (in thousands): 

	Internally Risk Graded								Non-Graded
	Performing
	Pass		Other Loans Especially Mentioned		Accruing Substandard		Nonaccrual		Performing		Nonaccrual		Total
Commercial:
Energy	$	3,700,406	$	117,298	$	63,951	$	91,722	$	—	$	—	$	3,973,377
Services	3,050,946		29,943		33,791		7,483		—		—		3,122,163
Wholesale/retail	1,749,023		5,281		5,399		1,163		—		—		1,760,866
Manufacturing	623,219		18,214		13,883		10,133		—		—		665,449
Healthcare	2,995,514		13,117		20,805		4,480		—		—		3,033,916
Public finance	709,868		—		—		—		—		—		709,868
Other commercial and industrial	709,729		4,028		17,744		398		34,075		37		766,011
Total commercial	13,538,705		187,881		155,573		115,379		34,075		37		14,031,650
Commercial real estate:
Residential construction and land development	150,529		—		—		350		—		—		150,879
Retail	743,343		12,067		1,243		18,868		—		—		775,521
Office	923,202		5,177		—		—		—		—		928,379
Multifamily	1,257,005		1,604		95		6,858		—		—		1,265,562
Industrial	852,539		1,658		1,011		909		—		—		856,117
Other commercial real estate	455,045		1,639		—		641		—		—		457,325
Total commercial real estate	4,381,663		22,145		2,349		27,626		—		—		4,433,783
Residential mortgage:
Permanent mortgage	276,138		78		2,404		493		758,260		19,948		1,057,321
Permanent mortgage guaranteed by U.S. government agencies	—		—		—		—		191,694		6,100		197,794
Home equity	—		—		—		—		817,976		11,081		829,057
Total residential mortgage	276,138		78		2,404		493		1,767,930		37,129		2,084,172
Personal	1,116,196		45		—		56		84,853		232		1,201,382
Total	$	19,312,702	$	210,149	$	160,326	$	143,554	$	1,886,858	$	37,398	$	21,750,987

Summary of Impaired Loans [Table Text Block]

A summary of impaired loans at December 31, 2019 follows (in thousands): 

			Recorded Investment
	Unpaid Principal Balance		Total		With No Allowance		With Allowance		Related Allowance
Commercial:
Energy	$	149,441	$	91,722	$	44,244	$	47,478	$	16,854
Services	10,923		7,483		6,301		1,182		240
Wholesale/retail	1,980		1,163		902		261		101
Manufacturing	10,848		10,133		9,914		219		219
Healthcare	13,774		4,480		4,480		—		—
Public finance	—		—		—		—		—
Other commercial and industrial	8,227		435		435		—		—
Total commercial	195,193		115,416		66,276		49,140		17,414
Commercial real estate:
Residential construction and land development	1,306		350		350		—		—
Retail	20,265		18,868		18,868		—		—
Office	—		—		—		—		—
Multifamily	6,858		6,858		6,858		—		—
Industrial	909		909		909		—		—
Other commercial real estate	801		641		641		—		—
Total commercial real estate	30,139		27,626		27,626		—		—
Residential mortgage:
Permanent mortgage	24,868		20,441		20,441		—		—
Permanent mortgage guaranteed by U.S. government agencies1	204,187		197,794		197,794		—		—
Home equity	12,967		11,081		11,081		—		—
Total residential mortgage	242,022		229,316		229,316		—		—
Personal	360		287		287		—		—
Total	$	467,714	$	372,645	$	323,505	$	49,140	$	17,414

¹ 

All permanent mortgage loans guaranteed by U.S. government agencies are considered impaired as we do not expect full collection of contractual principal and interest. At December 31, 2019, the majority were accruing based on the guarantee by U.S. government agencies.

Summary of Loans by Aging Status [Table Text Block]

A summary of loans currently performing and past due as of March 31, 2020 is as follows (in thousands):

			Past Due								Past Due 90 Days or More and Accruing
	Current		30 to 59 Days		60 to 89 Days		90 Days or More		Total
Commercial:
Energy	$	4,058,605	$	267	$	—	$	52,804	$	4,111,676	$	—
Healthcare	3,160,196		46		111		4,743		3,165,096		714
Services	3,941,795		7,173		198		6,582		3,955,748		74
General business	3,553,504		2,618		4,651		2,682		3,563,455		—
Total commercial	14,714,100		10,104		4,960		66,811		14,795,975		788
Commercial real estate	4,433,887		4,523		340		11,335		4,450,085		2,796
Loans to individuals:
Residential mortgage	1,828,421		8,759		1,717		5,658		1,844,555		119
Residential mortgage guaranteed by U.S. government agencies	55,901		25,948		16,217		99,823		197,889		96,980
Personal	1,175,143		169		77		77		1,175,466		3
Total loans to individuals	3,059,465		34,876		18,011		105,558		3,217,910		97,102
Total	$	22,207,452	$	49,503	$	23,311	$	183,704	$	22,463,970	$	100,686

A summary of loans currently performing, loans past due and accruing and nonaccrual loans as of December 31, 2019 is as follows (in thousands):

			Past Due
	Current		30 to 59 Days		60 to 89 Days		90 Days or More		Nonaccrual		Total
Commercial:
Energy	$	3,881,244	$	401	$	10	$	—	91,722		$	3,973,377
Services	3,105,621		1,737		523		6,799		7,483		3,122,163
Wholesale	1,758,878		712		113		—		1,163		1,760,866
Manufacturing	654,329		410		190		387		10,133		665,449
Healthcare	3,027,329		2,039		—		68		4,480		3,033,916
Public finance	707,638		2,230		—		—		—		709,868
Other commercial and industrial	764,390		414		772		—		435		766,011
Total commercial	13,899,429		7,943		1,608		7,254		115,416		14,031,650
Commercial real estate:
Residential construction and land development	147,379		3,093		—		57		350		150,879
Retail	756,653		—		—		—		18,868		775,521
Office	928,379		—		—		—		—		928,379
Multifamily	1,258,704		—		—		—		6,858		1,265,562
Industrial	855,208		—		—		—		909		856,117
Other commercial real estate	454,253		1,827		250		354		641		457,325
Total commercial real estate	4,400,576		4,920		250		411		27,626		4,433,783
Residential Mortgage:
Permanent mortgage	1,034,716		2,011		153		—		20,441		1,057,321
Permanent mortgage guaranteed by U.S. government agencies	46,898		24,203		18,187		102,406		6,100		197,794
Home equity	814,325		3,343		308		—		11,081		829,057
Total residential mortgage	1,895,939		29,557		18,648		102,406		37,622		2,084,172
Personal	1,196,362		4,664		54		15		287		1,201,382
Total	$	21,392,306	$	47,084	$	20,560	$	110,086	$	180,951	$	21,750,987

Financing Receivable, Nonaccrual [Table Text Block]

A summary of nonaccruing loans at March 31, 2020 follows (in thousands): 

	As of March 31, 2020
	Total		With No Allowance		With Allowance		Related Allowance
Commercial:
Energy	$	96,448	$	40,424	$	56,024	$	9,375
Healthcare	4,070		4,070		—		—
Services	8,425		7,258		1,167		240
General business	9,681		9,412		269		269
Total commercial	118,624		61,164		57,460		9,884
Commercial real estate	8,545		8,545		—		—
Loans to individuals:
Residential mortgage	30,721		30,721		—		—
Residential mortgage guaranteed by U.S. government agencies	5,005		5,005		—		—
Personal	277		277		—		—
Total loans to individuals	36,003		36,003		—		—
Total	$	163,172	$	105,712	$	57,460	$	9,884