Loans and Allowances for Credit Losses (Tables)

3 Months Ended

Mar. 31, 2016

Loans Receivable, Net [Abstract]

Schedule of Loans by Portfolio Segment [Table Text Block]

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

	March 31, 2016								December 31, 2015
	Fixed Rate		Variable Rate		Non-accrual		Total		Fixed Rate		Variable Rate		Non-accrual		Total
Commercial	$	1,932,757	$	8,181,016	$	174,652	$	10,288,425	$	1,850,548	$	8,325,559	$	76,424	$	10,252,531
Commercial real estate	643,033		2,718,204		9,270		3,370,507		627,678		2,622,354		9,001		3,259,033
Residential mortgage	1,592,706		219,026		57,577		1,869,309		1,598,992		216,661		61,240		1,876,893
Personal	87,092		406,902		331		494,325		91,816		460,418		463		552,697
Total	$	4,255,588	$	11,525,148	$	241,830	$	16,022,566	$	4,169,034	$	11,624,992	$	147,128	$	15,941,154
Accruing loans past due (90 days)1							$	8,019							$	1,207

	March 31, 2015
	Fixed Rate		Variable Rate		Non-accrual		Total
Commercial	$	1,807,837	$	7,569,446	$	13,880	$	9,391,163
Commercial real estate	703,511		2,212,051		19,902		2,935,464
Residential mortgage	1,679,211		201,301		46,487		1,926,999
Personal	100,719		329,327		464		430,510
Total	$	4,291,278	$	10,312,125	$	80,733	$	14,684,136
Accruing loans past due (90 days)1							$	523

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, 2016 is summarized as follows (in thousands):

	Commercial			Commercial Real Estate		Residential Mortgage			Personal			Nonspecific Allowance			Total
Allowance for loan losses:
Beginning balance	$	130,334		$	41,391	$	19,509		$	4,164		$	30,126		$	225,524
Provision for loan losses	31,097			2,977		(731		)	1,466			(4,705		)	30,104
Loans charged off	(22,126		)	—		(474		)	(1,391		)	—			(23,991		)
Recoveries	488			85		163			783			—			1,519
Ending balance	$	139,793		$	44,453	$	18,467		$	5,022		$	25,421		$	233,156
Allowance for off-balance sheet credit losses:
Beginning balance	$	1,506		$	153	$	30		$	22		$	—		$	1,711
Provision for off-balance sheet credit losses	4,813			75		28			(20		)	—			4,896
Ending balance	$	6,319		$	228	$	58		$	2		$	—		$	6,607
Total provision for credit losses	$	35,910		$	3,052	$	(703	)	$	1,446		$	(4,705	)	$	35,000

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, 2015 is summarized as follows (in thousands):

	Commercial			Commercial Real Estate			Residential Mortgage			Personal			Nonspecific Allowance		Total
Allowance for loan losses:
Beginning balance	$	90,875		$	42,445		$	23,458		$	4,233		$	28,045	$	189,056
Provision for loan losses	10,353			(10,417		)	(27		)	339			28		276
Loans charged off	(174		)	(28		)	(624		)	(1,343		)	—		(2,169		)
Recoveries	357			8,819			437			910			—		10,523
Ending balance	$	101,411		$	40,819		$	23,244		$	4,139		$	28,073	$	197,686
Allowance for off-balance sheet credit losses:
Beginning balance	$	475		$	707		$	28		$	20		$	—	$	1,230
Provision for off-balance sheet credit losses	102			(374		)	(4		)	—			—		(276		)
Ending balance	$	577		$	333		$	24		$	20		$	—	$	954
Total provision for credit losses	$	10,455		$	(10,791	)	$	(31	)	$	339		$	28	$	—

The allowance for loan losses and recorded investment of the related loans by portfolio segment for each impairment measurement method at March 31, 2016 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	$	10,113,773	$	137,191	$	174,652	$	2,602	$	10,288,425	$	139,793
Commercial real estate	3,361,237		44,435		9,270		18		3,370,507		44,453
Residential mortgage	1,811,732		18,401		57,577		66		1,869,309		18,467
Personal	493,994		5,022		331		—		494,325		5,022
Total	15,780,736		205,049		241,830		2,686		16,022,566		207,735
Nonspecific allowance	—		—		—		—		—		25,421
Total	$	15,780,736	$	205,049	$	241,830	$	2,686	$	16,022,566	$	233,156

The allowance for loan losses and recorded investment of the related loans by portfolio segment for each impairment measurement method at December 31, 2015 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	$	10,176,107	$	114,027	$	76,424	$	16,307	$	10,252,531	$	130,334
Commercial real estate	3,250,032		41,373		9,001		18		3,259,033		41,391
Residential mortgage	1,815,653		19,441		61,240		68		1,876,893		19,509
Personal	552,234		4,164		463		—		552,697		4,164
Total	15,794,026		179,005		147,128		16,393		15,941,154		195,398
Nonspecific allowance	—		—		—		—		—		30,126
Total	$	15,794,026	$	179,005	$	147,128	$	16,393	$	15,941,154	$	225,524

The allowance for loan losses and recorded investment of the related loans by portfolio segment for each impairment measurement method at March 31, 2015 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	$	9,377,283	$	101,214	$	13,880	$	197	$	9,391,163	$	101,411
Commercial real estate	2,915,562		40,801		19,902		18		2,935,464		40,819
Residential mortgage	1,880,512		23,142		46,487		102		1,926,999		23,244
Personal	430,046		4,139		464		—		430,510		4,139
Total	14,603,403		169,296		80,733		317		14,684,136		169,613
Nonspecific allowance	—		—		—		—		—		28,073
Total	$	14,603,403	$	169,296	$	80,733	$	317	$	14,684,136	$	197,686

Schedule of Allowance for Loan Losses and Recorded Investment by Portfolio Segment for Risk Graded and Non-Risk Graded Loans [Table Text Block]

The allowance for loan losses and recorded investment of the related loans by portfolio segment for risk graded and non-risk graded loans at March 31, 2016 is as follows (in thousands):

	Internally Risk Graded				Non-Graded				Total
	Recorded Investment		Related Allowance		Recorded Investment		Related Allowance		Recorded Investment		Related Allowance
Commercial	$	10,264,965	$	138,887	$	23,460	$	906	$	10,288,425	$	139,793
Commercial real estate	3,370,507		44,453		—		—		3,370,507		44,453
Residential mortgage	192,658		2,822		1,676,651		15,645		1,869,309		18,467
Personal	410,318		2,954		84,007		2,068		494,325		5,022
Total	14,238,448		189,116		1,784,118		18,619		16,022,566		207,735
Nonspecific allowance	—		—		—		—		—		25,421
Total	$	14,238,448	$	189,116	$	1,784,118	$	18,619	$	16,022,566	$	233,156

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, 2015 is as follows (in thousands):

	Internally Risk Graded				Non-Graded				Total
	Recorded Investment		Related Allowance		Recorded Investment		Related Allowance		Recorded Investment		Related Allowance
Commercial	$	10,227,303	$	129,426	$	25,228	$	908	$	10,252,531	$	130,334
Commercial real estate	3,259,033		41,391		—		—		3,259,033		41,391
Residential mortgage	196,701		2,883		1,680,192		16,626		1,876,893		19,509
Personal	467,955		1,390		84,742		2,774		552,697		4,164
Total	14,150,992		175,090		1,790,162		20,308		15,941,154		195,398
Nonspecific allowance	—		—		—		—		—		30,126
Total	$	14,150,992	$	175,090	$	1,790,162	$	20,308	$	15,941,154	$	225,524

The allowance for loan losses and recorded investment of the related loans by portfolio segment for risk graded and non-risk graded loans at March 31, 2015 is as follows (in thousands):

	Internally Risk Graded				Non-Graded				Total
	Recorded Investment		Related Allowance		Recorded Investment		Related Allowance		Recorded Investment		Related Allowance
Commercial	$	9,367,119	$	100,592	$	24,044	$	819	$	9,391,163	$	101,411
Commercial real estate	2,935,464		40,819		—		—		2,935,464		40,819
Residential mortgage	196,782		3,028		1,730,217		20,216		1,926,999		23,244
Personal	341,530		1,386		88,980		2,753		430,510		4,139
Total	12,840,895		145,825		1,843,241		23,788		14,684,136		169,613
Nonspecific allowance	—		—		—		—		—		28,073
Total	$	12,840,895	$	145,825	$	1,843,241	$	23,788	$	14,684,136	$	197,686

Schedule of Credit Quality Indicators [Table Text Block]

The following table summarizes the Company’s loan portfolio at March 31, 2016 by the risk grade categories (in thousands): 

	Internally Risk Graded						Non-Graded
	Performing		Potential Problem		Nonaccrual		Performing		Nonaccrual		Total
Commercial:
Energy	$	2,466,909	$	402,958	$	159,553	$	—	$	—	$	3,029,420
Services	2,712,494		6,885		9,512		—		—		2,728,891
Wholesale/retail	1,428,215		19,946		3,685		—		—		1,451,846
Manufacturing	588,827		11,506		312		—		—		600,645
Healthcare	1,986,598		7,804		1,023		—		—		1,995,425
Other commercial and industrial	458,255		—		483		23,376		84		482,198
Total commercial	9,641,298		449,099		174,568		23,376		84		10,288,425
Commercial real estate:
Residential construction and land development	166,237		923		4,789		—		—		171,949
Retail	808,800		420		1,302		—		—		810,522
Office	694,923		—		629		—		—		695,552
Multifamily	726,933		6,506		250		—		—		733,689
Industrial	564,391		—		76		—		—		564,467
Other commercial real estate	392,095		9		2,224		—		—		394,328
Total commercial real estate	3,353,379		7,858		9,270		—		—		3,370,507
Residential mortgage:
Permanent mortgage	187,166		3,146		2,346		730,596		25,151		948,405
Permanent mortgages guaranteed by U.S. government agencies	—		—		—		177,800		19,550		197,350
Home equity	—		—		—		713,024		10,530		723,554
Total residential mortgage	187,166		3,146		2,346		1,621,420		55,231		1,869,309
Personal	410,095		100		123		83,799		208		494,325
Total	$	13,591,938	$	460,203	$	186,307	$	1,728,595	$	55,523	$	16,022,566

The following table summarizes the Company’s loan portfolio at December 31, 2015 by the risk grade categories (in thousands): 

	Internally Risk Graded						Non-Graded
	Performing		Potential Problem		Nonaccrual		Performing		Nonaccrual		Total
Commercial:
Energy	$	2,906,357	$	129,782	$	61,189	$	—	$	—	$	3,097,328
Services	2,767,225		6,761		10,290		—		—		2,784,276
Wholesale/retail	1,412,780		6,365		2,919		—		—		1,422,064
Manufacturing	554,526		1,872		331		—		—		556,729
Healthcare	1,882,308		—		1,072		—		—		1,883,380
Other commercial and industrial	483,030		—		496		25,101		127		508,754
Total commercial	10,006,226		144,780		76,297		25,101		127		10,252,531
Commercial real estate:
Residential construction and land development	155,724		293		4,409		—		—		160,426
Retail	794,754		426		1,319		—		—		796,499
Office	636,501		555		651		—		—		637,707
Multifamily	744,299		6,512		274		—		—		751,085
Industrial	563,093		—		76		—		—		563,169
Other commercial real estate	347,864		11		2,272		—		—		350,147
Total commercial real estate	3,242,235		7,797		9,001		—		—		3,259,033
Residential mortgage:
Permanent mortgage	192,456		1,932		2,313		721,964		26,671		945,336
Permanent mortgages guaranteed by U.S. government agencies	—		—		—		175,037		21,900		196,937
Home equity	—		—		—		724,264		10,356		734,620
Total residential mortgage	192,456		1,932		2,313		1,621,265		58,927		1,876,893
Personal	467,811		14		130		84,409		333		552,697
Total	$	13,908,728	$	154,523	$	87,741	$	1,730,775	$	59,387	$	15,941,154

The following table summarizes the Company’s loan portfolio at March 31, 2015 by the risk grade categories (in thousands): 

	Internally Risk Graded						Non-Graded
	Performing		Potential Problem		Nonaccrual		Performing		Nonaccrual		Total
Commercial:
Energy	$	2,857,004	$	44,115	$	1,875	$	—	$	—	$	2,902,994
Services	2,573,879		14,253		4,744		—		—		2,592,876
Wholesale/retail	1,377,439		23,960		4,401		—		—		1,405,800
Manufacturing	546,566		13,942		417		—		—		560,925
Healthcare	1,505,072		4,547		1,558		—		—		1,511,177
Other commercial and industrial	392,549		—		798		23,957		87		417,391
Total commercial	9,252,509		100,817		13,793		23,957		87		9,391,163
Commercial real estate:
Residential construction and land development	128,795		759		9,598		—		—		139,152
Retail	654,429		574		3,857		—		—		658,860
Office	510,881		571		2,410		—		—		513,862
Multifamily	737,750		12,236		—		—		—		749,986
Industrial	478,508		—		76		—		—		478,584
Other commercial real estate	390,345		714		3,961		—		—		395,020
Total commercial real estate	2,900,708		14,854		19,902		—		—		2,935,464
Residential mortgage:
Permanent mortgage	192,473		2,069		2,240		736,357		31,125		964,264
Permanent mortgages guaranteed by U.S. government agencies	—		—		—		196,923		3,256		200,179
Home equity	—		—		—		752,690		9,866		762,556
Total residential mortgage	192,473		2,069		2,240		1,685,970		44,247		1,926,999
Personal	341,355		17		158		88,674		306		430,510
Total	$	12,687,045	$	117,757	$	36,093	$	1,798,601	$	44,640	$	14,684,136

Summary of Impaired Loans [Table Text Block]

Impaired Loans

Loans are considered to be impaired when it is probable that the Company will not be able to collect all amounts due according to the contractual terms of the loan agreement. This includes all nonaccruing loans, all loans modified in a TDR and all loans repurchased from GNMA pools.

A summary of impaired loans follows (in thousands):

	As of										For the
	March 31, 2016										Three Months Ended
			Recorded Investment								March 31, 2016
	Unpaid Principal Balance		Total		With No Allowance		With Allowance		Related Allowance		Average Recorded Investment		Interest Income Recognized
Commercial:
Energy	$	182,224	$	159,553	$	125,072	$	34,481	$	2,558	$	93,627	$	—
Services	12,824		9,512		9,512		—		—		9,901		—
Wholesale/retail	9,502		3,685		3,673		12		9		3,302		—
Manufacturing	658		312		312		—		—		322		—
Healthcare	1,338		1,023		905		118		35		1,048		—
Other commercial and industrial	8,235		567		567		—		—		595		—
Total commercial	214,781		174,652		140,041		34,611		2,602		108,795		—
Commercial real estate:
Residential construction and land development	7,621		4,789		4,789		—		—		4,599		—
Retail	1,923		1,302		1,302		—		—		1,311		—
Office	920		629		629		—		—		640		—
Multifamily	1,192		250		250		—		—		262		—
Industrial	76		76		76		—		—		76		—
Other real estate loans	8,348		2,224		2,068		156		18		2,248		—
Total commercial real estate	20,080		9,270		9,114		156		18		9,136		—
Residential mortgage:
Permanent mortgage	35,149		27,497		27,383		114		66		28,240		327
Permanent mortgage guaranteed by U.S. government agencies1	203,396		197,350		197,350		—		—		199,697		1,772
Home equity	11,321		10,530		10,530		—		—		10,443		—
Total residential mortgage	249,866		235,377		235,263		114		66		238,380		2,099
Personal	363		331		331		—		—		397		—
Total	$	485,090	$	419,630	$	384,749	$	34,881	$	2,686	$	356,708	$	2,099

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 March 31, 2016, $19.6 million of these loans were nonaccruing and $178 million were accruing based on the guarantee by U.S. government agencies.

Generally, no interest income is recognized on impaired loans until all principal balances, including amounts charged-off, are recovered.

A summary of impaired loans at December 31, 2015 follows (in thousands): 

			Recorded Investment
	Unpaid Principal Balance		Total		With No Allowance		With Allowance		Related Allowance
Commercial:
Energy	$	63,910	$	61,189	$	18,330	$	42,859	$	16,115
Services	13,449		10,290		9,657		633		148
Wholesale/retail	8,582		2,919		2,907		12		9
Manufacturing	665		331		331		—		—
Healthcare	1,352		1,072		931		141		35
Other commercial and industrial	8,304		623		623		—		—
Total commercial	96,262		76,424		32,779		43,645		16,307
Commercial real estate:
Residential construction and land development	8,963		4,409		4,409		—		—
Retail	1,923		1,319		1,319		—		—
Office	937		651		651		—		—
Multifamily	1,192		274		274		—		—
Industrial	76		76		76		—		—
Other real estate loans	8,363		2,272		2,113		159		18
Total commercial real estate	21,454		9,001		8,842		159		18
Residential mortgage:
Permanent mortgage	37,273		28,984		28,868		116		68
Permanent mortgage guaranteed by U.S. government agencies1	202,984		196,937		196,937		—		—
Home equity	10,988		10,356		10,356		—		—
Total residential mortgage	251,245		236,277		236,161		116		68
Personal	489		463		463		—		—
Total	$	369,450	$	322,165	$	278,245	$	43,920	$	16,393

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, 2015, $21.9 million of these loans were nonaccruing and $175 million were accruing based on the guarantee by U.S. government agencies.

A summary of impaired loans at March 31, 2015 follows (in thousands): 

											For the
	As of March 31, 2015										Three Months Ended
			Recorded Investment								March 31, 2015
	Unpaid Principal Balance		Total		With No Allowance		With Allowance		Related Allowance		Average Recorded Investment		Interest Income Recognized
Commercial:
Energy	$	1,884	$	1,875	$	1,875	$	—	$	—	$	1,646	$	—
Services	7,698		4,744		4,051		693		153		4,972		—
Wholesale/retail	9,953		4,401		4,369		32		9		4,275		—
Manufacturing	716		417		417		—		—		433		—
Healthcare	2,626		1,558		1,362		196		35		1,469		—
Other commercial and industrial	8,559		885		885		—		—		908		—
Total commercial	31,436		13,880		12,959		921		197		13,703		—
Commercial real estate:
Residential construction and land development	14,367		9,598		9,598		—		—		7,449		—
Retail	5,376		3,857		3,857		—		—		3,892		—
Office	4,464		2,410		2,410		—		—		2,915		—
Multifamily	—		—		—		—		—		—		—
Industrial	76		76		76		—		—		38		—
Other real estate loans	9,950		3,961		3,791		170		18		4,936		—
Total commercial real estate	34,233		19,902		19,732		170		18		19,230		—
Residential mortgage:
Permanent mortgage	42,011		33,365		33,200		165		102		34,105		315
Permanent mortgage guaranteed by U.S. government agencies1	207,133		200,179		200,179		—		—		207,795		2,256
Home equity	10,129		9,866		9,866		—		—		9,715		—
Total residential mortgage	259,273		243,410		243,245		165		102		251,615		2,571
Personal	482		464		464		—		—		515		—
Total	$	325,424	$	277,656	$	276,400	$	1,256	$	317	$	285,063	$	2,571

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 March 31, 2015, $3.3 million of these loans were nonaccruing and $197 million were accruing based on the guarantee by U.S. government agencies.

Troubled Debt Restructurings [Table Text Block]

Troubled Debt Restructurings

A summary of troubled debt restructurings ("TDRs") by accruing status as of March 31, 2016 is as follows (in thousands):

	As of March 31, 2016
	Recorded Investment		Performing in Accordance With Modified Terms		Not Performing in Accordance With Modified Terms		Specific Allowance		Amounts Charged Off During the Three Months Ended March 31, 2016
Nonaccruing TDRs:
Commercial:
Energy	$	2,829	$	—	$	2,829	$	—	$	—
Services	8,863		8,076		787		—		—
Wholesale/retail	2,619		2,567		52		9		—
Manufacturing	267		267		—		—		—
Healthcare	656		656		—		—		—
Other commercial and industrial	548		65		483		—		57
Total commercial	15,782		11,631		4,151		9		57
Commercial real estate:
Residential construction and land development	1,871		296		1,575		—		—
Retail	1,302		925		377		—		—
Office	160		160		—		—		—
Multifamily	—		—		—		—		—
Industrial	—		—		—		—		—
Other real estate loans	909		478		431		—		—
Total commercial real estate	4,242		1,859		2,383		—		—
Residential mortgage:
Permanent mortgage	16,242		11,451		4,791		66		3
Permanent mortgage guaranteed by U.S. government agencies	9,809		851		8,958		—		—
Home equity	5,078		4,207		871		—		66
Total residential mortgage	31,129		16,509		14,620		66		69
Personal	284		262		22		—		7
Total nonaccruing TDRs	$	51,437	$	30,261	$	21,176	$	75	$	133
Accruing TDRs:
Permanent mortgages guaranteed by U.S. government agencies	77,598		28,415		49,183		—		—
Total TDRs	$	129,035	$	58,676	$	70,359	$	75	$	133

A summary of troubled debt restructurings by accruing status as of December 31, 2015 is as follows (in thousands):

	As of
	December 31, 2015
	Recorded Investment		Performing in Accordance With Modified Terms		Not Performing in Accordance With Modified Terms		Specific Allowance
Nonaccruing TDRs:
Commercial:
Energy	$	2,304	$	2,304	$	—	$	—
Services	9,027		8,210		817		148
Wholesale/retail	2,758		2,706		52		9
Manufacturing	282		282		—		—
Healthcare	673		673		—		—
Other commercial and industrial	621		89		532		—
Total commercial	15,665		14,264		1,401		157
Commercial real estate:
Residential construction and land development	2,328		1,556		772		—
Retail	1,319		942		377		—
Office	165		165		—		—
Multifamily	—		—		—		—
Industrial	—		—		—		—
Other real estate loans	920		478		442		—
Total commercial real estate	4,732		3,141		1,591		—
Residential mortgage:
Permanent mortgage	16,618		9,043		7,575		68
Permanent mortgage guaranteed by U.S. government agencies	11,136		139		10,997		—
Home equity	5,159		4,218		941		—
Total residential mortgage	32,913		13,400		19,513		68
Personal	324		297		27		—
Total nonaccuring TDRs	$	53,634	$	31,102	$	22,532	$	225
Accruing TDRs:
Permanent mortgages guaranteed by U.S. government agencies	74,050		23,029		51,021		—
Total TDRs	$	127,684	$	54,131	$	73,553	$	225

A summary of troubled debt restructurings by accruing status as of March 31, 2015 is as follows (in thousands):

	As of March 31, 2015
	Recorded Investment		Performing in Accordance With Modified Terms		Not Performing in Accordance With Modified Terms		Specific Allowance		Amounts Charged Off During the Three Months Ended March 31, 2015
Nonaccruing TDRs:
Commercial:
Energy	$	—	$	—	$	—	$	—	$	—
Services	1,617		687		930		148		—
Wholesale/retail	3,224		3,131		93		9		—
Manufacturing	325		325		—		—		—
Healthcare	—		—		—		—		—
Other commercial and industrial	636		87		549		—		—
Total commercial	5,802		4,230		1,572		157		—
Commercial real estate:
Residential construction and land development	7,234		5,724		1,510		—		—
Retail	3,543		1,384		2,159		—		—
Office	1,364		182		1,182		—		—
Multifamily	—		—		—		—		—
Industrial	—		—		—		—		—
Other real estate loans	1,474		1,001		473		—		—
Total commercial real estate	13,615		8,291		5,324		—		—
Residential mortgage:
Permanent mortgage	15,680		11,667		4,013		102		5
Permanent mortgage guaranteed by U.S. government agencies	1,579		320		1,259		—		—
Home equity	5,298		4,333		965		—		24
Total residential mortgage	22,557		16,320		6,237		102		29
Personal	410		254		156		—		4
Total nonaccruing TDRs	$	42,384	$	29,095	$	13,289	$	259	$	33
Accruing TDRs:
Permanent mortgages guaranteed by U.S. government agencies	80,225		24,483		55,742		—		—
Total TDRs	$	122,609	$	53,578	$	69,031	$	259	$	33

Troubled debt restructurings generally consist of interest rate concessions, payment stream concessions or a combination of concessions to distressed borrowers. The following tables detail the recorded balance of loans at March 31, 2016 by class that were restructured during the three months ended March 31, 2016 by primary type of concession (in thousands):

	Three Months Ended March 31, 2016
	Accruing							Nonaccrual						Total
		Payment Stream		Combination & Other		Total		Payment Stream		Combination & Other		Total
Commercial:
Energy		$	—	$	—	$	—	$	525	$	—	$	525	$	525
Services		—		—		—		—		—		—		—
Wholesale/retail		—		—		—		—		—		—		—
Manufacturing		—		—		—		—		—		—		—
Healthcare		—		—		—		—		—		—		—
Other commercial and industrial		—		—		—		—		—		—		—
Total commercial		—		—		—		525		—		525		525
Commercial real estate:
Residential construction and land development		—		—		—		—		—		—		—
Retail		—		—		—		—		—		—		—
Office		—		—		—		—		—		—		—
Multifamily		—		—		—		—		—		—		—
Industrial		—		—		—		—		—		—		—
Other real estate loans		—		—		—		—		—		—		—
Total commercial real estate		—		—		—		—		—		—		—
Residential mortgage:
Permanent mortgage		—		—		—		367		62		429		429
Permanent mortgage guaranteed by U.S. government agencies		4,331		4,658		8,989		—		90		90		9,079
Home equity		—		—		—		—		622		622		622
Total residential mortgage		4,331		4,658		8,989		367		774		1,141		10,130
Personal		—		—		—		—		10		10		10
Total		$	4,331	$	4,658	$	8,989	$	892	$	784	$	1,676	$	10,665

Troubled debt restructurings generally consist of interest rate concessions, payment stream concessions or a combination of concessions to distressed borrowers. The following tables detail the recorded balance of loans by class that were restructured during three months ended March 31, 2015 by primary type of concession (in thousands):

	Three Months Ended March 31, 2015
	Accruing						Nonaccrual						Total
	Payment Stream		Combination & Other		Total		Payment Stream		Combination & Other		Total
Commercial:
Energy	$	—	$	—	$	—	$	—	$	—	$	—	$	—
Services	—		—		—		—		—		—		—
Wholesale/retail	—		—		—		—		—		—		—
Manufacturing	—		—		—		—		—		—		—
Healthcare	—		—		—		—		—		—		—
Other commercial and industrial	—		—		—		—		—		—		—
Total commercial	—		—		—		—		—		—		—
Commercial real estate:
Residential construction and land development	—		—		—		4,649		—		4,649		4,649
Retail	—		—		—		—		—		—		—
Office	—		—		—		—		—		—		—
Multifamily	—		—		—		—		—		—		—
Industrial	—		—		—		—		—		—		—
Other real estate loans	—		—		—		—		—		—		—
Total commercial real estate	—		—		—		4,649		—		4,649		4,649
Residential mortgage:
Permanent mortgage	—		—		—		659		622		1,281		1,281
Permanent mortgage guaranteed by U.S. government agencies	7,990		6,308		14,298		—		142		142		14,440
Home equity	—		—		—		152		842		994		994
Total residential mortgage	7,990		6,308		14,298		811		1,606		2,417		16,715
Personal	—		—		—		—		63		63		63
Total	$	7,990	$	6,308	$	14,298	$	5,460	$	1,669	$	7,129	$	21,427

The following table summarizes, by loan class, the recorded investment at March 31, 2016 and 2015, respectively, of loans modified as TDRs within the previous 12 months and for which there was a payment default during the three months ended March 31, 2016 and 2015, respectively (in thousands):

	Three Months Ended March 31, 2016						Three Months Ended March 31, 2015
	Accruing		Nonaccrual		Total		Accruing		Nonaccrual		Total
Commercial:
Energy	$	—	$	2,829	$	2,829	$	—	$	—	$	—
Services	—		—		—		—		—		—
Wholesale/retail	—		—		—		—		—		—
Manufacturing	—		—		—		—		—		—
Healthcare	—		—		—		—		—		—
Other commercial and industrial	—		—		—		—		—		—
Total commercial	—		2,829		2,829		—		—		—
Commercial real estate:
Residential construction and land development	—		—		—		—		363		363
Retail	—		—		—		—		—		—
Office	—		—		—		—		—		—
Multifamily	—		—		—		—		—		—
Industrial	—		—		—		—		—		—
Other real estate loans	—		—		—		—		—		—
Total commercial real estate	—		—		—		—		363		363
Residential mortgage:
Permanent mortgage	—		1,597		1,597		—		2,383		2,383
Permanent mortgage guaranteed by U.S. government agencies	22,606		1,346		23,952		33,920		673		34,593
Home equity	—		365		365		—		693		693
Total residential mortgage	22,606		3,308		25,914		33,920		3,749		37,669
Personal	—		—		—		—		24		24
Total	$	22,606	$	6,137	$	28,743	$	33,920	$	4,136	$	38,056

A payment default is defined as being 30 days or more past due. The table above includes loans that experienced a payment default during the period, but may be performing in accordance with the modified terms as of the balance sheet date.

Summary of Loans by Aging Status [Table Text Block]

Nonaccrual & Past Due Loans

Past due status for all loan classes is based on the actual number of days since the last payment was due according to the contractual terms of the loans.

A summary of loans currently performing, loans past due and accruing and nonaccrual loans as of March 31, 2016 is as follows (in thousands):

			Past Due
	Current		30 to 89 Days		90 Days or More		Nonaccrual		Total
Commercial:
Energy	$	2,864,408	$	3,001	$	2,458	$	159,553	$	3,029,420
Services	2,714,697		4,682		—		9,512		2,728,891
Wholesale/retail	1,443,503		4,658		—		3,685		1,451,846
Manufacturing	600,029		—		304		312		600,645
Healthcare	1,994,402		—		—		1,023		1,995,425
Other commercial and industrial	481,286		345		—		567		482,198
Total commercial	10,098,325		12,686		2,762		174,652		10,288,425
Commercial real estate:
Residential construction and land development	167,160		—		—		4,789		171,949
Retail	809,220		—		—		1,302		810,522
Office	694,923		—		—		629		695,552
Multifamily	728,183		—		5,256		250		733,689
Industrial	564,391		—		—		76		564,467
Other real estate loans	392,104		—		—		2,224		394,328
Total commercial real estate	3,355,981		—		5,256		9,270		3,370,507
Residential mortgage:
Permanent mortgage	918,965		1,943		—		27,497		948,405
Permanent mortgages guaranteed by U.S. government agencies	43,259		27,325		107,216		19,550		197,350
Home equity	710,824		2,200		—		10,530		723,554
Total residential mortgage	1,673,048		31,468		107,216		57,577		1,869,309
Personal	493,722		271		1		331		494,325
Total	$	15,621,076	$	44,425	$	115,235	$	241,830	$	16,022,566

A summary of loans currently performing, loans past due and accruing and nonaccrual loans as of December 31, 2015 is as follows (in thousands):

			Past Due
	Current		30 to 89 Days		90 Days or More		Nonaccrual		Total
Commercial:
Energy	$	3,033,504	$	2,635	$	—	$	61,189	$	3,097,328
Services	2,769,895		4,091		—		10,290		2,784,276
Wholesale/retail	1,418,396		49		700		2,919		1,422,064
Manufacturing	556,398		—		—		331		556,729
Healthcare	1,879,873		2,435		—		1,072		1,883,380
Other commercial and industrial	507,929		100		102		623		508,754
Total commercial	10,165,995		9,310		802		76,424		10,252,531
Commercial real estate:
Residential construction and land development	156,017		—		—		4,409		160,426
Retail	795,180		—		—		1,319		796,499
Office	637,056		—		—		651		637,707
Multifamily	742,697		8,114		—		274		751,085
Industrial	563,093		—		—		76		563,169
Other real estate loans	347,498		—		377		2,272		350,147
Total commercial real estate	3,241,541		8,114		377		9,001		3,259,033
Residential mortgage:
Permanent mortgage	913,062		3,290		—		28,984		945,336
Permanent mortgages guaranteed by U.S. government agencies	33,653		30,383		111,001		21,900		196,937
Home equity	721,149		3,095		20		10,356		734,620
Total residential mortgage	1,667,864		36,768		111,021		61,240		1,876,893
Personal	551,533		693		8		463		552,697
Total	$	15,626,933	$	54,885	$	112,208	$	147,128	$	15,941,154

A summary of loans currently performing, loans past due and accruing and nonaccrual loans as of March 31, 2015 is as follows (in thousands):

			Past Due
	Current		30 to 89 Days		90 Days or More		Nonaccrual		Total
Commercial:
Energy	$	2,894,332	$	6,787	$	—	$	1,875	$	2,902,994
Services	2,587,668		415		49		4,744		2,592,876
Wholesale/retail	1,401,399		—		—		4,401		1,405,800
Manufacturing	560,008		500		—		417		560,925
Healthcare	1,509,594		25		—		1,558		1,511,177
Other commercial and industrial	416,362		115		29		885		417,391
Total commercial	9,369,363		7,842		78		13,880		9,391,163
Commercial real estate:
Residential construction and land development	129,554		—		—		9,598		139,152
Retail	654,558		—		445		3,857		658,860
Office	511,452		—		—		2,410		513,862
Multifamily	745,247		4,739		—		—		749,986
Industrial	478,508		—		—		76		478,584
Other real estate loans	390,411		648		—		3,961		395,020
Total commercial real estate	2,909,730		5,387		445		19,902		2,935,464
Residential mortgage:
Permanent mortgage	926,848		4,051		—		33,365		964,264
Permanent mortgages guaranteed by U.S. government agencies	39,309		22,370		135,244		3,256		200,179
Home equity	749,618		3,072		—		9,866		762,556
Total residential mortgage	1,715,775		29,493		135,244		46,487		1,926,999
Personal	429,618		428		—		464		430,510
Total	$	14,424,486	$	43,150	$	135,767	$	80,733	$	14,684,136