Loans, Allowance for Loan and Lease Losses, and Reserve for Off-Balance Sheet Credit Commitments (Detail 4) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Allowance for Loan and Lease Losses
Beginning Balance	$ 308,858	$ 305,790	$ 310,149	$ 302,584
Charge-offs	(3,106)	(13,153)	(6,208)	(15,661)
Recoveries	2,534	9,518	5,194	16,196
Net (charge-offs) recoveries	(572)	(3,635)	(1,014)	535
(Reversal of) provision for credit losses	10,000	(1,000)	10,000	(1,000)
Transfers for reserve for off-balance sheet credit commitments	(1,364)	10,121	(2,213)	9,157
Ending Balance	316,922	311,276	316,922	311,276
Allowance individually evaluated for impairment	1,595	8,833	1,595	8,833
Allowance collectively evaluated for impairment	315,327	302,443	315,327	302,443
Loans and leases, excluding covered loans	21,929,328	18,474,788	21,929,328	18,474,788	$ 20,337,206
Loans and leases, individually evaluated for impairment	50,445	89,615	50,445	89,615
Loans and leases, collectively evaluated for impairment	21,878,883	18,385,173	21,878,883	18,385,173
Reserve for Off Balance Sheet Credit Commitments
Balance, beginning of the year	28,660	34,908	27,811	33,944
Transfers (to) from allowance for loan and lease losses	1,364	(10,121)	2,213	(9,157)
Balance, end of the year	30,024	24,787	30,024	24,787
Commercial (includes lease financing)
Allowance for Loan and Lease Losses
Beginning Balance	120,666	121,574	115,855	117,103
Charge-offs	(2,875)	(12,862)	(5,700)	(14,821)
Recoveries	599	7,503	1,715	9,235
Net (charge-offs) recoveries	(2,276)	(5,359)	(3,985)	(5,586)
(Reversal of) provision for credit losses	5,924	711	12,444	5,409
Transfers for reserve for off-balance sheet credit commitments		9,353		9,353
Ending Balance	124,314	126,279	124,314	126,279
Allowance individually evaluated for impairment	1,299	8,477	1,299	8,477
Allowance collectively evaluated for impairment	123,015	117,802	123,015	117,802
Loans and leases, excluding covered loans	10,723,200	8,837,544	10,723,200	8,837,544
Loans and leases, individually evaluated for impairment	8,791	29,231	8,791	29,231
Loans and leases, collectively evaluated for impairment	10,714,409	8,808,313	10,714,409	8,808,313
Commercial real estate mortgages
Allowance for Loan and Lease Losses
Beginning Balance	47,017	51,361	44,745	50,678
Charge-offs				(5)
Recoveries	42	27	1,202	127
Net (charge-offs) recoveries	42	27	1,202	122
(Reversal of) provision for credit losses	1,590	(737)	2,702	(149)
Ending Balance	48,649	50,651	48,649	50,651
Allowance individually evaluated for impairment	263	301	263	301
Allowance collectively evaluated for impairment	48,386	50,350	48,386	50,350
Loans and leases, excluding covered loans	3,850,915	3,464,918	3,850,915	3,464,918	3,539,703
Loans and leases, individually evaluated for impairment	22,993	33,456	22,993	33,456
Loans and leases, collectively evaluated for impairment	3,827,922	3,431,462	3,827,922	3,431,462
Residential mortgages
Allowance for Loan and Lease Losses
Beginning Balance	9,967	11,595	10,296	11,540
Charge-offs				(482)
Recoveries	37	190	76	225
Net (charge-offs) recoveries	37	190	76	(257)
(Reversal of) provision for credit losses	(344)	(1,489)	(712)	(987)
Ending Balance	9,660	10,296	9,660	10,296
Allowance individually evaluated for impairment	33	5	33	5
Allowance collectively evaluated for impairment	9,627	10,291	9,627	10,291
Loans and leases, excluding covered loans	5,490,375	4,814,435	5,490,375	4,814,435	5,106,803
Loans and leases, individually evaluated for impairment	11,912	10,596	11,912	10,596
Loans and leases, collectively evaluated for impairment	5,478,463	4,803,839	5,478,463	4,803,839
Real estate construction
Allowance for Loan and Lease Losses
Beginning Balance	10,234	6,468	9,115	6,351
Recoveries	1,623	687	1,710	5,075
Net (charge-offs) recoveries	1,623	687	1,710	5,075
(Reversal of) provision for credit losses	(1,205)	36	(173)	(4,235)
Ending Balance	10,652	7,191	10,652	7,191
Allowance collectively evaluated for impairment	10,652	7,191	10,652	7,191
Loans and leases, excluding covered loans	877,838	457,557	877,838	457,557	710,224
Loans and leases, individually evaluated for impairment	5,816	12,846	5,816	12,846
Loans and leases, collectively evaluated for impairment	872,022	444,711	872,022	444,711
Home equity loans and lines of credit
Allowance for Loan and Lease Losses
Beginning Balance	6,361	6,419	6,609	6,677
Charge-offs		(149)		(165)
Recoveries	35	43	73	202
Net (charge-offs) recoveries	35	(106)	73	37
(Reversal of) provision for credit losses	(992)	262	(1,278)	(139)
Ending Balance	5,404	6,575	5,404	6,575
Allowance collectively evaluated for impairment	5,404	6,575	5,404	6,575
Loans and leases, excluding covered loans	787,417	716,816	787,417	716,816	785,796
Loans and leases, individually evaluated for impairment	933	3,436	933	3,436
Loans and leases, collectively evaluated for impairment	786,484	713,380	786,484	713,380
Installment
Allowance for Loan and Lease Losses
Beginning Balance	2,153	1,824	2,228	1,842
Charge-offs	(231)	(142)	(508)	(188)
Recoveries	198	1,068	418	1,332
Net (charge-offs) recoveries	(33)	926	(90)	1,144
(Reversal of) provision for credit losses	88	(466)	70	(702)
Ending Balance	2,208	2,284	2,208	2,284
Allowance individually evaluated for impairment		50		50
Allowance collectively evaluated for impairment	2,208	2,234	2,208	2,234
Loans and leases, excluding covered loans	199,583	183,518	199,583	183,518	$ 184,613
Loans and leases, individually evaluated for impairment		50		50
Loans and leases, collectively evaluated for impairment	199,583	183,468	199,583	183,468
Qualitative
Allowance for Loan and Lease Losses
Beginning Balance	112,460	106,549	121,301	108,393
(Reversal of) provision for credit losses	4,939	683	(3,053)	(197)
Transfers for reserve for off-balance sheet credit commitments	(1,364)	768	(2,213)	(196)
Ending Balance	116,035	108,000	116,035	108,000
Allowance collectively evaluated for impairment	$ 116,035	$ 108,000	$ 116,035	$ 108,000