Loans, Allowance for Loan and Lease Losses, and Reserve for Off-Balance Sheet Credit Commitments (Detail 8) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Past Due Loans and Leases
30-59 Days Past Due	$ 10,224	$ 9,800
60-89 Days Past Due	13,304	2,103
Greater Than 90 Days and Accruing	3,461	1,515
Nonaccrual	34,522	42,167
Total Past Due and Nonaccrual Loans	61,511	55,585
Current	22,475,073	20,281,621
Total Loans and Leases	22,536,584	20,337,206	$ 19,347,988
Commercial
Past Due Loans and Leases
30-59 Days Past Due	5,094	8,462
60-89 Days Past Due	1,550	325
Greater Than 90 Days and Accruing		148
Nonaccrual	14,728	15,096
Total Past Due and Nonaccrual Loans	21,372	24,031
Current	10,232,220	9,336,945
Total Loans and Leases	10,253,592	9,360,976
Commercial real estate mortgages
Past Due Loans and Leases
30-59 Days Past Due	3,847	693
Nonaccrual	2,368	3,575
Total Past Due and Nonaccrual Loans	6,215	4,268
Current	3,941,531	3,535,435
Total Loans and Leases	3,947,746	3,539,703	3,565,188
Residential mortgages
Past Due Loans and Leases
60-89 Days Past Due	8,157	1,474
Greater Than 90 Days and Accruing	2,458	921
Nonaccrual	10,588	11,943
Total Past Due and Nonaccrual Loans	21,203	14,338
Current	5,688,069	5,092,465
Total Loans and Leases	5,709,272	5,106,803	5,023,213
Fixed
Past Due Loans and Leases
60-89 Days Past Due	2,556	309
Greater Than 90 Days and Accruing	305	921
Nonaccrual	10,000	10,365
Total Past Due and Nonaccrual Loans	12,861	11,595
Current	1,475,111	1,390,357
Total Loans and Leases	1,487,972	1,401,952
Variable
Past Due Loans and Leases
60-89 Days Past Due	5,601	1,165
Greater Than 90 Days and Accruing	2,153
Nonaccrual	588	1,578
Total Past Due and Nonaccrual Loans	8,342	2,743
Current	4,212,958	3,702,108
Total Loans and Leases	4,221,300	3,704,851
Real estate construction
Past Due Loans and Leases
Nonaccrual	3,460	6,598
Total Past Due and Nonaccrual Loans	3,460	6,598
Current	928,962	703,626
Total Loans and Leases	932,422	710,224	585,232
Construction
Past Due Loans and Leases
Current	900,928	686,990
Total Loans and Leases	900,928	686,990
Land.
Past Due Loans and Leases
Nonaccrual	3,460	6,598
Total Past Due and Nonaccrual Loans	3,460	6,598
Current	28,034	16,636
Total Loans and Leases	31,494	23,234
Home equity loans and lines of credit
Past Due Loans and Leases
30-59 Days Past Due	910
60-89 Days Past Due	3,072	39
Greater Than 90 Days and Accruing	460	100
Nonaccrual	3,340	4,864
Total Past Due and Nonaccrual Loans	7,782	5,003
Current	791,929	780,793
Total Loans and Leases	799,711	785,796	759,258
Installment
Past Due Loans and Leases
30-59 Days Past Due	373	324
60-89 Days Past Due	68	113
Greater Than 90 Days and Accruing	543	346
Nonaccrual	37	84
Total Past Due and Nonaccrual Loans	1,021	867
Current	205,135	183,746
Total Loans and Leases	206,156	184,613	$ 178,803
Commercial Installment loan
Past Due Loans and Leases
Current	228	298
Total Loans and Leases	228	298
Consumer Installment loan
Past Due Loans and Leases
30-59 Days Past Due	373	324
60-89 Days Past Due	68	113
Greater Than 90 Days and Accruing	543	346
Nonaccrual	37	84
Total Past Due and Nonaccrual Loans	1,021	867
Current	204,907	183,448
Total Loans and Leases	205,928	184,315
Lease financing
Past Due Loans and Leases
30-59 Days Past Due		321
60-89 Days Past Due	457	152
Nonaccrual	1	7
Total Past Due and Nonaccrual Loans	458	480
Current	687,227	648,611
Total Loans and Leases	$ 687,685	$ 649,091