Loans, Allowance for Loan and Lease Losses, and Reserve for Off-Balance Sheet Credit Commitments (Details 8) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Past Due Loans and Leases
30-59 Days Past Due	$ 9,800	$ 8,191
60-89 Days Past Due	2,103	2,925
Greater Than 90 Days and Accruing	1,515	453
Nonaccrual	42,167	68,651
Total Past Due and Nonaccrual Loans	55,585	80,220
Current	20,281,621	17,090,218
Total Loans and Leases	20,337,206	17,170,438
Contractual interest foregone on nonaccrual loans, excluding covered loans
Interest income that would have been recognized had nonaccrual loans performed in accordance with their original terms	4,339	6,013	8,549
Less: Interest income recognized on nonaccrual loans on a cash basis	(301)	(1,219)	(1,446)
Interest income foregone on nonaccrual loans	4,038	4,794	7,103
Commercial
Past Due Loans and Leases
30-59 Days Past Due	8,462	6,582
60-89 Days Past Due	325	362
Greater Than 90 Days and Accruing	148
Nonaccrual	15,096	14,248
Total Past Due and Nonaccrual Loans	24,031	21,192
Current	9,336,945	7,541,108
Total Loans and Leases	9,360,976	7,562,300
Commercial | Loans previously reported as lease financing
Past Due Loans and Leases
Total Loans and Leases		158,200
Commercial real estate mortgages
Past Due Loans and Leases
30-59 Days Past Due	693	1,197
60-89 Days Past Due		1,633
Nonaccrual	3,575	18,449
Total Past Due and Nonaccrual Loans	4,268	21,279
Current	3,535,435	3,201,722
Total Loans and Leases	3,539,703	3,223,001
Residential mortgages
Past Due Loans and Leases
60-89 Days Past Due	1,474
Greater Than 90 Days and Accruing	921	379
Nonaccrual	11,943	11,661
Total Past Due and Nonaccrual Loans	14,338	12,040
Current	5,092,465	4,542,271
Total Loans and Leases	5,106,803	4,554,311
Fixed
Past Due Loans and Leases
60-89 Days Past Due	309
Greater Than 90 Days and Accruing	921	379
Nonaccrual	10,365	3,789
Total Past Due and Nonaccrual Loans	11,595	4,168
Current	1,390,357	1,436,283
Total Loans and Leases	1,401,952	1,440,451
Variable
Past Due Loans and Leases
60-89 Days Past Due	1,165
Nonaccrual	1,578	7,872
Total Past Due and Nonaccrual Loans	2,743	7,872
Current	3,702,108	3,105,988
Total Loans and Leases	3,704,851	3,113,860
Real estate construction
Past Due Loans and Leases
60-89 Days Past Due		797
Nonaccrual	6,598	19,067
Total Past Due and Nonaccrual Loans	6,598	19,864
Current	703,626	347,140
Total Loans and Leases	710,224	367,004
Construction
Past Due Loans and Leases
Nonaccrual		5,467
Total Past Due and Nonaccrual Loans		5,467
Current	686,990	332,131
Total Loans and Leases	686,990	337,598
Land.
Past Due Loans and Leases
60-89 Days Past Due		797
Nonaccrual	6,598	13,600
Total Past Due and Nonaccrual Loans	6,598	14,397
Current	16,636	15,009
Total Loans and Leases	23,234	29,406
Home equity loans and lines of credit
Past Due Loans and Leases
60-89 Days Past Due	39
Greater Than 90 Days and Accruing	100	74
Nonaccrual	4,864	5,144
Total Past Due and Nonaccrual Loans	5,003	5,218
Current	780,793	704,126
Total Loans and Leases	785,796	709,344
Installment
Past Due Loans and Leases
30-59 Days Past Due	324	11
60-89 Days Past Due	113	7
Greater Than 90 Days and Accruing	346
Nonaccrual	84	32
Total Past Due and Nonaccrual Loans	867	50
Current	183,746	151,905
Total Loans and Leases	184,613	151,955
Commercial Installment loan
Past Due Loans and Leases
30-59 Days Past Due		1
Total Past Due and Nonaccrual Loans		1
Current	298	361
Total Loans and Leases	298	362
Consumer Installment loan
Past Due Loans and Leases
30-59 Days Past Due	324	10
60-89 Days Past Due	113	7
Greater Than 90 Days and Accruing	346
Nonaccrual	84	32
Total Past Due and Nonaccrual Loans	867	49
Current	183,448	151,544
Total Loans and Leases	184,315	151,593
Lease financing
Past Due Loans and Leases
30-59 Days Past Due	321	401
60-89 Days Past Due	152	126
Nonaccrual	7	50
Total Past Due and Nonaccrual Loans	480	577
Current	648,611	601,946
Total Loans and Leases	649,091	602,523
Lease financing | Loans previously reported as lease financing
Past Due Loans and Leases
Total Loans and Leases		$ (158,200)