Loans, Allowance for Loan Losses, and Credit Quality Commercial Loans by Credit Quality Indicator (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Commercial loans by credit quality indicator
Commercial and industrial	$ 4,822,680	$ 4,502,021
Commercial real estate - owner occupied	1,114,715	1,219,747
Lease financing	55,483	64,196
Commercial and business lending	5,992,878	5,785,964
Commercial real estate - investor	2,939,456	2,906,759
Real estate construction	896,248	655,381
Commercial real estate lending	3,835,704	3,562,140
Total commercial	9,828,582	9,348,104
Pass [Member]
Commercial loans by credit quality indicator
Commercial and industrial	4,485,160	4,208,478
Commercial real estate - owner occupied	959,849	1,030,632
Lease financing	52,733	58,099
Commercial and business lending	5,497,742	5,297,209
Commercial real estate - investor	2,740,255	2,634,035
Real estate construction	877,911	603,481
Commercial real estate lending	3,618,166	3,237,516
Total commercial	9,115,908	8,534,725
Special Mention [Member]
Commercial loans by credit quality indicator
Commercial and industrial	153,615	97,787
Commercial real estate - owner occupied	55,404	51,417
Lease financing	897	2,802
Commercial and business lending	209,916	152,006
Commercial real estate - investor	64,230	65,309
Real estate construction	2,814	6,976
Commercial real estate lending	67,044	72,285
Total commercial	276,960	224,291
Potential Problem [Member]
Commercial loans by credit quality indicator
Commercial and industrial	113,669	128,434
Commercial real estate - owner occupied	56,789	99,592
Lease financing	1,784	264
Commercial and business lending	172,242	228,290
Commercial real estate - investor	52,429	107,068
Real estate construction	5,263	13,092
Commercial real estate lending	57,692	120,160
Total commercial	229,934	348,450
Impaired [Member]
Commercial loans by credit quality indicator
Commercial and industrial	70,236	67,322
Commercial real estate - owner occupied	42,673	38,106
Lease financing	69	3,031
Commercial and business lending	112,978	108,459
Commercial real estate - investor	82,542	100,347
Real estate construction	10,260	31,832
Commercial real estate lending	92,802	132,179
Total commercial	$ 205,780	$ 240,638