Loans and Allowances 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		3 Months Ended		3 Months Ended		3 Months Ended																						3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012 Loans [Member]	Mar. 31, 2013 Loans [Member]	Mar. 31, 2012 Loans [Member] Commercial loans [Member]	Mar. 31, 2013 Loans [Member] Commercial loans [Member]	Mar. 31, 2012 Loans [Member] Residential mortgage loans [Member]	Mar. 31, 2013 Loans [Member] Residential mortgage loans [Member]	Mar. 31, 2012 Loans [Member] Consumer loans [Member]	Mar. 31, 2013 Loans [Member] Consumer loans [Member]	Mar. 31, 2013 Loans [Member] Originated loans [Member]	Mar. 31, 2012 Loans [Member] Originated loans [Member]	Mar. 31, 2013 Loans [Member] Originated loans [Member] Commercial loans [Member]	Mar. 31, 2012 Loans [Member] Originated loans [Member] Commercial loans [Member]	Mar. 31, 2013 Loans [Member] Originated loans [Member] Residential mortgage loans [Member]	Mar. 31, 2012 Loans [Member] Originated loans [Member] Residential mortgage loans [Member]	Mar. 31, 2013 Loans [Member] Originated loans [Member] Consumer loans [Member]	Mar. 31, 2012 Loans [Member] Originated loans [Member] Consumer loans [Member]	Mar. 31, 2013 Loans [Member] Acquired loans [Member]	Mar. 31, 2013 Loans [Member] Acquired loans [Member] Commercial loans [Member]	Mar. 31, 2013 Loans [Member] Acquired loans [Member] Residential mortgage loans [Member]	Mar. 31, 2013 Loans [Member] Acquired loans [Member] Consumer loans [Member]	Mar. 31, 2013 Loans [Member] Covered loans [Member]	Mar. 31, 2012 Loans [Member] Covered loans [Member]	Mar. 31, 2013 Loans [Member] Covered loans [Member] Commercial loans [Member]	Mar. 31, 2012 Loans [Member] Covered loans [Member] Commercial loans [Member]	Mar. 31, 2013 Loans [Member] Covered loans [Member] Residential mortgage loans [Member]	Mar. 31, 2012 Loans [Member] Covered loans [Member] Residential mortgage loans [Member]	Mar. 31, 2013 Loans [Member] Covered loans [Member] Consumer loans [Member]	Mar. 31, 2012 Loans [Member] Covered loans [Member] Consumer loans [Member]	Mar. 31, 2013 Allowance for loan losses [Member]	Mar. 31, 2012 Allowance for loan losses [Member]	Mar. 31, 2013 Allowance for loan losses [Member] Commercial loans [Member]	Mar. 31, 2012 Allowance for loan losses [Member] Commercial loans [Member]	Mar. 31, 2013 Allowance for loan losses [Member] Residential mortgage loans [Member]	Mar. 31, 2012 Allowance for loan losses [Member] Residential mortgage loans [Member]	Mar. 31, 2013 Allowance for loan losses [Member] Consumer loans [Member]	Mar. 31, 2012 Allowance for loan losses [Member] Consumer loans [Member]	Mar. 31, 2013 Allowance for loan losses [Member] Originated loans [Member]	Mar. 31, 2012 Allowance for loan losses [Member] Originated loans [Member]	Mar. 31, 2013 Allowance for loan losses [Member] Originated loans [Member] Commercial loans [Member]	Mar. 31, 2012 Allowance for loan losses [Member] Originated loans [Member] Commercial loans [Member]	Mar. 31, 2013 Allowance for loan losses [Member] Originated loans [Member] Residential mortgage loans [Member]	Mar. 31, 2012 Allowance for loan losses [Member] Originated loans [Member] Residential mortgage loans [Member]	Mar. 31, 2013 Allowance for loan losses [Member] Originated loans [Member] Consumer loans [Member]	Mar. 31, 2012 Allowance for loan losses [Member] Originated loans [Member] Consumer loans [Member]	Mar. 31, 2013 Allowance for loan losses [Member] Acquired loans [Member]	Mar. 31, 2013 Allowance for loan losses [Member] Acquired loans [Member] Commercial loans [Member]	Mar. 31, 2013 Allowance for loan losses [Member] Acquired loans [Member] Residential mortgage loans [Member]	Mar. 31, 2013 Allowance for loan losses [Member] Covered loans [Member]	Mar. 31, 2012 Allowance for loan losses [Member] Covered loans [Member]	Mar. 31, 2013 Allowance for loan losses [Member] Covered loans [Member] Commercial loans [Member]	Mar. 31, 2012 Allowance for loan losses [Member] Covered loans [Member] Commercial loans [Member]	Mar. 31, 2013 Allowance for loan losses [Member] Covered loans [Member] Residential mortgage loans [Member]	Mar. 31, 2012 Allowance for loan losses [Member] Covered loans [Member] Residential mortgage loans [Member]	Mar. 31, 2013 Allowance for loan losses [Member] Covered loans [Member] Consumer loans [Member]	Mar. 31, 2012 Allowance for loan losses [Member] Covered loans [Member] Consumer loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable, Allowance, Beginning Balance	$ 137,777	$ 136,171		$ 11,482,762		$ 8,291,509		$ 1,587,519		$ 1,603,734	$ 7,378,936	$ 5,451,007	$ 5,161,227	$ 3,702,528	$ 886,232	$ 564,218	$ 1,331,477	$ 1,184,261	$ 3,626,850	$ 2,996,718	$ 449,500	$ 180,632	$ 476,976	$ 633,784	$ 133,564	$ 224,523	$ 251,787	$ 275,856	$ 91,625	$ 133,405	$ 136,171	$ 124,881	$ 77,969	$ 78,414	$ 39,080	$ 13,918	$ 19,122	$ 32,549	$ 78,774	$ 83,246	$ 59,149	$ 60,211	$ 6,406	$ 4,894	$ 13,219	$ 18,141	$ 788	$ 788		$ 56,609	$ 41,635	$ 18,032	$ 18,203	$ 32,674	$ 9,024	$ 5,903	$ 14,408
Charge-offs																															(15,369)	(26,095)	(10,596)	(22,186)	(159)	(791)	(4,614)	(3,118)	(11,237)	(9,666)	(7,027)	(5,757)	(135)	(791)	(4,075)	(3,118)				(4,132)	(16,429)	(3,569)	(16,429)	(24)		(539)
Recoveries																															5,514	2,612	3,246	1,479	511	70	1,757	1,063	4,604	2,612	2,723	1,479	487	70	1,394	1,063				910		523		24		363
Net provision for loan losses																															9,578	10,015	5,659	10,473	626	3,639	3,293	(4,097)	3,355	8,303	2,754	9,559	(1,502)	2,986	2,103	(4,242)	(372)	(639)	267	6,595	1,712	3,544	914	1,861	653	1,190	145
Increase in FDIC loss share receivable																															1,883	30,924	431	15,758	1,246	12,397	206	2,769												1,883	30,924	431	15,758	1,246	12,397	206	2,769
Loans and Leases receivable, Allowance, Ending Balance	137,777	136,171	11,130,273	11,482,762	7,992,375	8,291,509	1,511,349	1,587,519	1,626,549	1,603,734	7,378,936	5,451,007	5,161,227	3,702,528	886,232	564,218	1,331,477	1,184,261	3,626,850	2,996,718	449,500	180,632	476,976	633,784	133,564	224,523	251,787	275,856	91,625	133,405	137,777	142,337	76,709	83,938	41,304	29,233	19,764	29,166	75,496	84,495	57,599	65,492	5,256	7,159	12,641	11,844	416	149	267	61,865	57,842	18,961	18,446	35,781	22,074	7,123	17,322
Ending balance: Individually evaluated for impairment			56,422	78,169	48,338	71,884	8,084	6,285			58,366	56,422	56,702	48,338	1,664	8,084			15,582	11,354	4,228		4,221		3,828		393				2,590	11,199	2,323	10,634	267	565			2,174	11,199	2,174	10,634		565			416	149	267
Ending balance: Collectively evaluated for impairment			11,073,851	11,404,593	7,944,037	8,219,625	1,503,265	1,581,234	1,626,549	1,603,734	7,320,570	5,394,585	5,104,525	3,654,190	884,568	556,134	1,331,477	1,184,261	3,611,268	2,985,364	445,272	180,632	472,755	633,784	129,736	224,523	251,394	275,856	91,625	133,405	135,187	131,138	74,386	73,304	41,037	28,668	19,764	29,166	73,322	73,296	55,425	54,858	5,256	6,594	12,641	11,844				61,865	57,842	18,961	18,446	35,781	22,074	7,123	17,322
Ending balance: Acquired loans			$ 5,045,482		$ 4,065,324		$ 671,275		$ 308,883