Loans, Allowance for Loan and Lease Losses, and Reserve for Off-Balance Sheet Credit Commitments (Detail 8) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
Past Due Loans and Leases
30-59 Days Past Due	$ 9,899	$ 9,800
60-89 Days Past Due	8,355	2,103
Greater Than 90 Days and Accruing	2,734	1,515
Nonaccrual	29,015	42,167
Total Past Due and Nonaccrual Loans	50,003	55,585
Current	21,879,325	20,281,621
Total Loans and Leases	21,929,328	20,337,206	$ 18,474,788
Commercial
Past Due Loans and Leases
30-59 Days Past Due	6,493	8,462
60-89 Days Past Due	4,498	325
Greater Than 90 Days and Accruing	32	148
Nonaccrual	8,337	15,096
Total Past Due and Nonaccrual Loans	19,360	24,031
Current	10,042,375	9,336,945
Total Loans and Leases	10,061,735	9,360,976
Commercial real estate mortgages
Past Due Loans and Leases
30-59 Days Past Due	3,177	693
60-89 Days Past Due	1,882
Nonaccrual	2,726	3,575
Total Past Due and Nonaccrual Loans	7,785	4,268
Current	3,843,130	3,535,435
Total Loans and Leases	3,850,915	3,539,703	3,464,918
Residential mortgages
Past Due Loans and Leases
60-89 Days Past Due	1,569	1,474
Greater Than 90 Days and Accruing	2,172	921
Nonaccrual	11,088	11,943
Total Past Due and Nonaccrual Loans	14,829	14,338
Current	5,475,546	5,092,465
Total Loans and Leases	5,490,375	5,106,803	4,814,435
Fixed
Past Due Loans and Leases
60-89 Days Past Due	519	309
Greater Than 90 Days and Accruing		921
Nonaccrual	10,500	10,365
Total Past Due and Nonaccrual Loans	11,019	11,595
Current	1,496,702	1,390,357
Total Loans and Leases	1,507,721	1,401,952
Variable
Past Due Loans and Leases
60-89 Days Past Due	1,050	1,165
Greater Than 90 Days and Accruing	2,172
Nonaccrual	588	1,578
Total Past Due and Nonaccrual Loans	3,810	2,743
Current	3,978,844	3,702,108
Total Loans and Leases	3,982,654	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	874,378	703,626
Total Loans and Leases	877,838	710,224	457,557
Construction
Past Due Loans and Leases
Current	850,560	686,990
Total Loans and Leases	850,560	686,990
Land.
Past Due Loans and Leases
Nonaccrual	3,460	6,598
Total Past Due and Nonaccrual Loans	3,460	6,598
Current	23,818	16,636
Total Loans and Leases	27,278	23,234
Home equity loans and lines of credit
Past Due Loans and Leases
60-89 Days Past Due	240	39
Greater Than 90 Days and Accruing	50	100
Nonaccrual	3,371	4,864
Total Past Due and Nonaccrual Loans	3,661	5,003
Current	783,756	780,793
Total Loans and Leases	787,417	785,796	716,816
Installment
Past Due Loans and Leases
30-59 Days Past Due	229	324
60-89 Days Past Due	145	113
Greater Than 90 Days and Accruing	480	346
Nonaccrual	29	84
Total Past Due and Nonaccrual Loans	883	867
Current	198,700	183,746
Total Loans and Leases	199,583	184,613	$ 183,518
Commercial Installment loan
Past Due Loans and Leases
Current	236	298
Total Loans and Leases	236	298
Consumer Installment loan
Past Due Loans and Leases
30-59 Days Past Due	229	324
60-89 Days Past Due	145	113
Greater Than 90 Days and Accruing	480	346
Nonaccrual	29	84
Total Past Due and Nonaccrual Loans	883	867
Current	198,464	183,448
Total Loans and Leases	199,347	184,315
Lease financing
Past Due Loans and Leases
30-59 Days Past Due		321
60-89 Days Past Due	21	152
Nonaccrual	4	7
Total Past Due and Nonaccrual Loans	25	480
Current	661,440	648,611
Total Loans and Leases	$ 661,465	$ 649,091