Loans and Allowance for Loan Losses - Allowance for Loan Losses by Portfolio Segment and Related Recorded Investment in Loans (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Beginning Balance			$ 136,171
Loans and Leases receivable, Allowance, Ending Balance	11,734,472		11,734,472		11,577,802
Net provision for loan losses	7,569	8,101	25,404	26,141
Loans and Leases receivable, Allowance, Ending Balance	138,223		138,223
Commercial Non-Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Ending Balance	4,625,315		4,625,315		4,433,288
Construction and Land Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Ending Balance	920,408		920,408		989,306
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Ending Balance	2,914,969		2,914,969		2,923,094
Residential Mortgage Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Ending Balance	1,695,197		1,695,197		1,577,944
Consumer loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Ending Balance	1,578,583		1,578,583		1,654,170
Commercial loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Ending Balance					8,345,688
Allowance for loan losses [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Beginning Balance			136,171
Loans and Leases receivable, Allowance, Beginning Balance				124,881
Charge-offs			(40,259)	(57,427)
Recoveries			15,410	7,595
Net provision for loan losses			(25,404)	(26,141)
Increase in FDIC loss share receivable			1,497	34,401
Loans and Leases receivable, Allowance, Ending Balance	138,223		138,223
Loans and Leases receivable, Allowance, Ending Balance		135,591		135,591
Ending balance: Individually evaluated for impairment	1,945	8,602	1,945	8,602
Ending balance: Collectively evaluated for impairment	75,939	71,147	75,939	71,147
Acquired-impaired	60,339	55,842	60,339	55,842
Allowance for loan losses [Member] | Commercial Non-Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Beginning Balance			23,725
Charge-offs			(5,880)
Recoveries			3,471
Net provision for loan losses			(10,036)
Increase in FDIC loss share receivable			447
Loans and Leases receivable, Allowance, Ending Balance	31,799		31,799
Ending balance: Individually evaluated for impairment	325		325
Ending balance: Collectively evaluated for impairment	29,784		29,784
Acquired-impaired	1,690		1,690
Allowance for loan losses [Member] | Construction and Land Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Beginning Balance			17,038
Charge-offs			(9,332)
Recoveries			1,797
Net provision for loan losses			(472)
Increase in FDIC loss share receivable			(314)
Loans and Leases receivable, Allowance, Ending Balance	9,661		9,661
Ending balance: Individually evaluated for impairment	211		211
Ending balance: Collectively evaluated for impairment	6,971		6,971
Acquired-impaired	2,479		2,479
Allowance for loan losses [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Beginning Balance			36,392
Charge-offs			(8,034)
Recoveries			4,735
Net provision for loan losses			2,038
Increase in FDIC loss share receivable			(732)
Loans and Leases receivable, Allowance, Ending Balance	30,323		30,323
Ending balance: Individually evaluated for impairment	1,409		1,409
Ending balance: Collectively evaluated for impairment	20,937		20,937
Acquired-impaired	7,977		7,977
Allowance for loan losses [Member] | Residential Mortgage Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Beginning Balance			36,877
Loans and Leases receivable, Allowance, Beginning Balance				13,918
Charge-offs			(2,496)	(4,889)
Recoveries			1,004	310
Net provision for loan losses			(4,787)	(6,532)
Increase in FDIC loss share receivable			1,261	11,189
Loans and Leases receivable, Allowance, Ending Balance	41,433		41,433
Loans and Leases receivable, Allowance, Ending Balance		27,060		27,060
Ending balance: Individually evaluated for impairment		133		133
Ending balance: Collectively evaluated for impairment	5,912	4,518	5,912	4,518
Acquired-impaired	35,521	22,409	35,521	22,409
Allowance for loan losses [Member] | Consumer loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Beginning Balance			22,139
Loans and Leases receivable, Allowance, Beginning Balance				32,549
Charge-offs			(14,517)	(11,663)
Recoveries			4,403	3,060
Net provision for loan losses			(12,147)	5,753
Increase in FDIC loss share receivable			835	562
Loans and Leases receivable, Allowance, Ending Balance	25,007		25,007
Loans and Leases receivable, Allowance, Ending Balance		18,755		18,755
Ending balance: Collectively evaluated for impairment	12,335	16,080	12,335	16,080
Acquired-impaired	12,672	2,675	12,672	2,675
Allowance for loan losses [Member] | Commercial loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Beginning Balance				78,414
Charge-offs				(40,875)
Recoveries				4,225
Net provision for loan losses				(25,362)
Increase in FDIC loss share receivable				22,650
Loans and Leases receivable, Allowance, Ending Balance		89,776		89,776
Ending balance: Individually evaluated for impairment		8,469		8,469
Ending balance: Collectively evaluated for impairment		50,549		50,549
Acquired-impaired		30,758		30,758
Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Ending Balance	11,734,472	11,434,448	11,734,472	11,434,448
Ending balance: Individually evaluated for impairment	51,907	85,861	51,907	85,861
Ending balance: Collectively evaluated for impairment	11,225,592	10,595,864	11,225,592	10,595,864
Acquired-impaired	456,973	752,723	456,973	752,723
Loans [Member] | Commercial Non-Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Ending Balance	4,625,315		4,625,315
Ending balance: Individually evaluated for impairment	11,090		11,090
Ending balance: Collectively evaluated for impairment	4,570,918		4,570,918
Acquired-impaired	43,307		43,307
Loans [Member] | Construction and Land Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Ending Balance	920,408		920,408
Ending balance: Individually evaluated for impairment	16,774		16,774
Ending balance: Collectively evaluated for impairment	865,357		865,357
Acquired-impaired	38,277		38,277
Loans [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Ending Balance	2,914,969		2,914,969
Ending balance: Individually evaluated for impairment	23,541		23,541
Ending balance: Collectively evaluated for impairment	2,805,716		2,805,716
Acquired-impaired	85,712		85,712
Loans [Member] | Residential Mortgage Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Ending Balance	1,695,197	1,561,640	1,695,197	1,561,640
Ending balance: Individually evaluated for impairment	502	7,524	502	7,524
Ending balance: Collectively evaluated for impairment	1,465,814	1,259,767	1,465,814	1,259,767
Acquired-impaired	228,881	294,349	228,881	294,349
Loans [Member] | Consumer loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Ending Balance	1,578,583	1,685,339	1,578,583	1,685,339
Ending balance: Collectively evaluated for impairment	1,517,787	1,577,265	1,517,787	1,577,265
Acquired-impaired	60,796	108,074	60,796	108,074
Loans [Member] | Commercial loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Ending Balance		8,187,469		8,187,469
Ending balance: Individually evaluated for impairment		78,337		78,337
Ending balance: Collectively evaluated for impairment		7,758,832		7,758,832
Acquired-impaired		350,300		350,300
Covered loans [Member] | Allowance for loan losses [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Beginning Balance			56,609	41,635
Charge-offs			(8,873)	(22,839)
Recoveries			3,119
Net provision for loan losses			7,987	2,645
Increase in FDIC loss share receivable			1,497	34,401
Loans and Leases receivable, Allowance, Ending Balance	60,339	55,842	60,339	55,842
Ending balance: Individually evaluated for impairment
Acquired-impaired	60,339	55,842	60,339	55,842
Covered loans [Member] | Allowance for loan losses [Member] | Commercial Non-Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Beginning Balance			2,162
Charge-offs			(681)
Recoveries			90
Net provision for loan losses			(328)
Increase in FDIC loss share receivable			447
Loans and Leases receivable, Allowance, Ending Balance	1,690		1,690
Acquired-impaired	1,690		1,690
Covered loans [Member] | Allowance for loan losses [Member] | Construction and Land Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Beginning Balance			5,623
Charge-offs			(1,784)
Recoveries			554
Net provision for loan losses			(1,600)
Increase in FDIC loss share receivable			(314)
Loans and Leases receivable, Allowance, Ending Balance	2,479		2,479
Acquired-impaired	2,479		2,479
Covered loans [Member] | Allowance for loan losses [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Beginning Balance			9,433
Charge-offs			(4,316)
Recoveries			2,395
Net provision for loan losses			1,197
Increase in FDIC loss share receivable			(732)
Loans and Leases receivable, Allowance, Ending Balance	7,977		7,977
Acquired-impaired	7,977		7,977
Covered loans [Member] | Allowance for loan losses [Member] | Residential Mortgage Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Beginning Balance			30,471	9,024
Charge-offs			(947)
Recoveries			13
Net provision for loan losses			4,723	2,196
Increase in FDIC loss share receivable			1,261	11,189
Loans and Leases receivable, Allowance, Ending Balance	35,521	22,409	35,521	22,409
Ending balance: Individually evaluated for impairment
Acquired-impaired	35,521	22,409	35,521	22,409
Covered loans [Member] | Allowance for loan losses [Member] | Consumer loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Beginning Balance			8,920	14,408
Charge-offs			(1,145)
Recoveries			67
Net provision for loan losses			3,995	(12,295)
Increase in FDIC loss share receivable			835	562
Loans and Leases receivable, Allowance, Ending Balance	12,672	2,675	12,672	2,675
Ending balance: Individually evaluated for impairment
Acquired-impaired	12,672	2,675	12,672	2,675
Covered loans [Member] | Allowance for loan losses [Member] | Commercial loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Beginning Balance				18,203
Charge-offs				(22,839)
Recoveries
Net provision for loan losses				12,744
Increase in FDIC loss share receivable				22,650
Loans and Leases receivable, Allowance, Ending Balance		30,758		30,758
Ending balance: Individually evaluated for impairment
Acquired-impaired		30,758		30,758
Covered loans [Member] | Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Ending Balance	392,002	555,732	392,002	555,732
Acquired-impaired	392,002		392,002
Acquired-impaired		555,732		555,732
Covered loans [Member] | Loans [Member] | Commercial Non-Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Ending Balance	24,340		24,340
Acquired-impaired	24,340		24,340
Covered loans [Member] | Loans [Member] | Construction and Land Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Ending Balance	23,197		23,197
Acquired-impaired	23,197		23,197
Covered loans [Member] | Loans [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Ending Balance	60,280		60,280
Acquired-impaired	60,280		60,280
Covered loans [Member] | Loans [Member] | Residential Mortgage Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Ending Balance	223,494	271,618	223,494	271,618
Acquired-impaired	223,494		223,494
Acquired-impaired		271,618		271,618
Covered loans [Member] | Loans [Member] | Consumer loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Ending Balance	60,691	107,390	60,691	107,390
Acquired-impaired	60,691		60,691
Acquired-impaired		107,390		107,390
Covered loans [Member] | Loans [Member] | Commercial loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Ending Balance		176,724		176,724
Acquired-impaired		176,724		176,724
Originated loans [Member] | Allowance for loan losses [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Beginning Balance			78,774	83,246
Charge-offs			(31,386)	(34,588)
Recoveries			12,291	7,595
Net provision for loan losses			(17,742)	(23,496)
Loans and Leases receivable, Allowance, Ending Balance	77,421	79,749	77,421	79,749
Ending balance: Individually evaluated for impairment	1,482	8,602	1,482	8,602
Ending balance: Collectively evaluated for impairment	75,939	71,147	75,939	71,147
Originated loans [Member] | Allowance for loan losses [Member] | Commercial Non-Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Beginning Balance			20,775
Charge-offs			(5,199)
Recoveries			3,381
Net provision for loan losses			(11,152)
Loans and Leases receivable, Allowance, Ending Balance	30,109		30,109
Ending balance: Individually evaluated for impairment	325		325
Ending balance: Collectively evaluated for impairment	29,784		29,784
Originated loans [Member] | Allowance for loan losses [Member] | Construction and Land Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Beginning Balance			11,415
Charge-offs			(7,548)
Recoveries			1,243
Net provision for loan losses			(2,072)
Loans and Leases receivable, Allowance, Ending Balance	7,182		7,182
Ending balance: Individually evaluated for impairment	211		211
Ending balance: Collectively evaluated for impairment	6,971		6,971
Originated loans [Member] | Allowance for loan losses [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Beginning Balance			26,959
Charge-offs			(3,718)
Recoveries			2,340
Net provision for loan losses			3,698
Loans and Leases receivable, Allowance, Ending Balance	21,883		21,883
Ending balance: Individually evaluated for impairment	946		946
Ending balance: Collectively evaluated for impairment	20,937		20,937
Originated loans [Member] | Allowance for loan losses [Member] | Residential Mortgage Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Beginning Balance			6,406	4,894
Charge-offs			(1,549)	(4,889)
Recoveries			991	310
Net provision for loan losses			(64)	(4,336)
Loans and Leases receivable, Allowance, Ending Balance	5,912	4,651	5,912	4,651
Ending balance: Individually evaluated for impairment		133		133
Ending balance: Collectively evaluated for impairment	5,912	4,518	5,912	4,518
Originated loans [Member] | Allowance for loan losses [Member] | Consumer loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Beginning Balance			13,219	18,141
Charge-offs			(13,372)	(11,663)
Recoveries			4,336	3,060
Net provision for loan losses			(8,152)	(6,542)
Loans and Leases receivable, Allowance, Ending Balance	12,335	16,080	12,335	16,080
Ending balance: Collectively evaluated for impairment	12,335	16,080	12,335	16,080
Originated loans [Member] | Allowance for loan losses [Member] | Commercial loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Beginning Balance				60,211
Charge-offs				(18,036)
Recoveries				4,225
Net provision for loan losses				(12,618)
Loans and Leases receivable, Allowance, Ending Balance		59,018		59,018
Ending balance: Individually evaluated for impairment		8,469		8,469
Ending balance: Collectively evaluated for impairment		50,549		50,549
Originated loans [Member] | Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Ending Balance	8,700,767	6,581,194	8,700,767	6,581,194
Ending balance: Individually evaluated for impairment	46,125	85,861	46,125	85,861
Ending balance: Collectively evaluated for impairment	8,654,642	6,495,333	8,654,642	6,495,333
Originated loans [Member] | Loans [Member] | Commercial Non-Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Ending Balance	3,633,490		3,633,490
Ending balance: Individually evaluated for impairment	8,911		8,911
Ending balance: Collectively evaluated for impairment	3,624,579		3,624,579
Originated loans [Member] | Loans [Member] | Construction and Land Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Ending Balance	738,983		738,983
Ending balance: Individually evaluated for impairment	16,044		16,044
Ending balance: Collectively evaluated for impairment	722,939		722,939
Originated loans [Member] | Loans [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Ending Balance	1,816,402		1,816,402
Ending balance: Individually evaluated for impairment	21,170		21,170
Ending balance: Collectively evaluated for impairment	1,795,232		1,795,232
Originated loans [Member] | Loans [Member] | Residential Mortgage Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Ending Balance	1,124,649	757,471	1,124,649	757,471
Ending balance: Individually evaluated for impairment		7,524		7,524
Ending balance: Collectively evaluated for impairment	1,124,649	749,947	1,124,649	749,947
Originated loans [Member] | Loans [Member] | Consumer loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Ending Balance	1,387,243	1,357,987	1,387,243	1,357,987
Ending balance: Collectively evaluated for impairment	1,387,243	1,357,987	1,387,243	1,357,987
Originated loans [Member] | Loans [Member] | Commercial loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Ending Balance		4,465,736		4,465,736
Ending balance: Individually evaluated for impairment		78,337		78,337
Ending balance: Collectively evaluated for impairment		4,387,399		4,387,399
Acquired loans [Member] | Allowance for loan losses [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Beginning Balance			788
Net provision for loan losses			325
Loans and Leases receivable, Allowance, Ending Balance	463		463
Ending balance: Individually evaluated for impairment	463		463
Acquired loans [Member] | Allowance for loan losses [Member] | Commercial Non-Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Beginning Balance			788
Net provision for loan losses			788
Acquired loans [Member] | Allowance for loan losses [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net provision for loan losses			(463)
Loans and Leases receivable, Allowance, Ending Balance	463		463
Ending balance: Individually evaluated for impairment	463		463
Acquired loans [Member] | Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Ending Balance	2,641,703		2,641,703
Ending balance: Individually evaluated for impairment	5,782		5,782
Ending balance: Collectively evaluated for impairment	2,570,950		2,570,950
Acquired-impaired	64,971		64,971
Acquired loans [Member] | Loans [Member] | Commercial Non-Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Ending Balance	967,485		967,485
Ending balance: Individually evaluated for impairment	2,179		2,179
Ending balance: Collectively evaluated for impairment	946,339		946,339
Acquired-impaired	18,967		18,967
Acquired loans [Member] | Loans [Member] | Construction and Land Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Ending Balance	158,228		158,228
Ending balance: Individually evaluated for impairment	730		730
Ending balance: Collectively evaluated for impairment	142,418		142,418
Acquired-impaired	15,080		15,080
Acquired loans [Member] | Loans [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Ending Balance	1,038,287		1,038,287
Ending balance: Individually evaluated for impairment	2,371		2,371
Ending balance: Collectively evaluated for impairment	1,010,484		1,010,484
Acquired-impaired	25,432		25,432
Acquired loans [Member] | Loans [Member] | Residential Mortgage Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Ending Balance	347,054		347,054
Ending balance: Individually evaluated for impairment	502		502
Ending balance: Collectively evaluated for impairment	341,165		341,165
Acquired-impaired	5,387		5,387
Acquired loans [Member] | Loans [Member] | Consumer loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Ending Balance	130,649		130,649
Ending balance: Collectively evaluated for impairment	130,544		130,544
Acquired-impaired	$ 105		$ 105